Rupture of the Deep Layer of the Deltoid Ligament: Is the External Rotation Stress Test Diagnostic?

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Zhen Jiang, Xiaoyan Guo, Rui Zhang, Xiangji Meng, Dailiang Jia, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8791887/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Background The integrity of the deep layer of the deltoid ligament is a critical determinant of ankle joint stability. The external rotation stress test, a common physical examination for assessing medial structural integrity, has suboptimal diagnostic sensitivity, potentially leading to false negative findings. Methods According to the Lauge-Hansen classification,seventeen patients were diagnosed with supination-external rotation type IV, nine patients were diagnosed with pronation-external rotation type IV,four patients were diagnosed with pronation-abduction type III, and two patients were diagnosed with supination-adduction type II. Eleven patients were preoperatively diagnosed with deep deltoid ligament rupture (with a medial malleolar gap≥5mm compared to the contralateral side or with lateral subluxation/dislocation of the talus).Twenty-one patients were intraoperatively diagnosed with deep deltoid ligament rupture (with a medial malleolar gap≥5mm or lateral subluxation of the talus after reduction of the ankle fracture, as demonstrated by a positive external rotation stress test or Cotton test). All patients underwent external rotation stress and Cotton testing.A comparative analysis of the diagnostic performance for deep deltoid ligament rupture was conducted between the individual and combined application of the two tests. Statistical analyses were performed via SPSS software (version 26.0), with a P value < 0.05 considered statistically significant. Results The results of the external rotation stress test, the Cotton test, and the combined application of both testing methods were as follows: the accuracies were 68.75%, 78.13%, and 96.88%, respectively, and the missed diagnosis rates were 31.25%, 21.88%, and 3.12%, respectively. These tests can lead to missed diagnoses, and the Cotton test appears to be more sensitive than the external rotation stress test. Moreover, the combined application of the two methods significantly improved the diagnostic rate of deep deltoid ligament rupture compared with the external rotation stress test (P = 0.004 < 0.05) and the Cotton test (P = 0.031 < 0.05). Conclusions The external rotation stress test, a commonly used method for physical examination of the ankle joint, demonstrated limitations in diagnosing deep deltoid ligament ruptures in this cohort. Therefore, the Cotton test and external rotation stress test should be performed together to improve the positive rate. Health sciences/Anatomy Health sciences/Diseases Health sciences/Health care Health sciences/Medical research Deltoid ligament Diagnosis External rotation stress test Cotton test Figures Figure 1 Figure 2 Figure 3 Background Ankle fractures can be classified as stable or unstable. Stable fractures have a good prognosis with nonsurgical treatment, whereas unstable fractures commonly necessitate surgical reduction and maintenance in a stable position. Otherwise, the prognosis will be poor. The presence or absence of a medial ankle injury is key to diagnosing whether an ankle fracture is stable. Injury to the medial ankle encompasses both medial malleolar fractures and deltoid ligament injuries. Medial malleolar fractures are easy to diagnose, and a consensus is that they require reduction and stable fixation. There is controversy surrounding the treatment of deltoid ligament injuries[ 9 ]. The timing and accuracy of diagnosing deltoid ligament rupture hold significant clinical relevance, irrespective of the subsequent therapeutic pathway—be it surgical intervention or conservative management. Ligament injuries are not visible on conventional DR (digital radiography) and CT (computed tomography) scans, especially when the medial malleolar space is normal or not significantly widened, which can easily lead to missed diagnoses or misdiagnosed cases, causing patients to miss the best treatment timing or choose the wrong treatment plan. For pure-ligament injuries, whether the deep layer of the deltoid ligament is ruptured is a critical factor in determining ankle joint stability. The external rotation stress test is considered the gold standard for the clinical diagnosis of deep deltoid ligament ruptures[ 21 ]. Finding new and effective diagnostic measures is extremely important for confirming deep deltoid ligament rupture at the medial malleolus. The Cotton test is widely used in clinical practice and plays a crucial role in diagnosing deltoid ligament ruptures. However, its diagnostic value for deep deltoid ligament rupture remains unclear. This study analyzed the diagnostic effectiveness of the external rotation stress test and Cotton test, individually and unitedly, for detecting deep deltoid ligament ruptures. We conducted these tests on patients who were already diagnosed with such ruptures at the medial malleolus. This study aimed to enhance the diagnostic basis for deep deltoid ligament ruptures at the medial malleolus by uniquely evaluating the efficacy of the combined application of the external rotation stress test and Cotton test. Despite the perceived utility of the external rotation stress test, preliminary observations suggest a potentially high rate of missed diagnoses, which this study aims to explore, particularly in combination with the Cotton test. Methods The inclusion criteria were as follows: (1) aged 22–65 years; (2) had closed ankle fractures; and (3) had confirmed deep deltoid ligament ruptures at the medial malleolus (diagnosed as follows: 1. Magnetic resonance imaging (MRI) revealing deep deltoid ligament rupture; 2. Direct intraoperative visualization and palpation of the ruptured ligament). DR findings were used as index test results, not as part of the reference standard for rupture confirmation[ 7 ]. ). The exclusion criteria were as follows: (1) patients with multiple underlying diseases who could not tolerate surgery and (2) patients with poor compliance due to mental disorders. Study subjects We retrospectively analyzed data from thirty-two patients with ankle fractures and deep deltoid ligament ruptures between October 2012 and January 2023. After the reduction and fixation of ankle fractures were completed, we routinely performed an external rotation stress test for all different types of fractures (Fig. 1 , Fig. 2 ). These patients met the criteria for deep deltoid ligament ruptures at the medial malleolus, and their ages ranged from 22–65 years. The Lauge–Hansen classification system[ 17 ] included seventeen cases of supination–external rotation type IV injuries, nine cases of pronation–external rotation type IV injuries, four cases of pronation–abduction type III injuries, and two cases of supination–adduction type II injuries (Table 1 ). Table 1 Lauge-hansen classification and results of the Cotton test and stress external rotation test in cases case Cotton test External rotation stress test Lauge-Hansen classification Case1 + - supination–external rotation Case 2 + - supination–external rotation Case 3 - - supination–external rotation Case 4 + + pronation–external rotation Case 5 - + supination-adduction Case 6 - + supination–external rotation Case 7 - + supination–external rotation Case 8 + - pronation–external rotation Case 9 + + supination–external rotation Case 10 + + pronation–abduction Case 11 + + pronation–external rotation Case 12 + - supination–external rotation Case 13 + - pronation–external rotation Case 14 + + supination–external rotation Case 15 + + supination–external rotation Case 16 + + supination–external rotation Case 17 + + pronation–external rotation Case 18 + + supination–external rotation Case 19 + + pronation–external rotation Case 20 + + pronation–abduction Case21 + + supination–external rotation Case22 + + supination–external rotation Case23 - + supination–external rotation Case24 + - supination–external rotation Case25 + - supination–external rotation Case26 - + pronation–external rotation Case27 + + supination–external rotation Case28 - + pronation–abduction Case29 + + pronation–external rotation Case30 + - pronation–external rotation Case31 + + supination-adduction Case32 + - pronation–abduction +: Positive,-: Feminine. Description of the surgery We administered spinal or combined spinal–epidural anesthesia and applied a thigh tourniquet to the affected side. Anatomical reduction and fixation of the fibula followed. If the posterior malleolar fracture was ≥ 25% in size, it was fixed with screws or a buttress plate. Medial malleolar fractures are routinely treated with open reduction and fixation via cannulated screws or K-wires for anatomical reduction. After fixation, standard ankle mortise DR examinations, external rotation stress tests, and Cotton tests were performed. In our hands, the modified Cotton test was performed as follows: with the foot and ankle stabilized, a pointed reduction clamp was applied to perform lateral traction to the fibula. A force of 58.8–88.2 N was used (based on the patient's weight, F = 0.98 N/kg, F = mg, g = 9.8 m/s²). The test was considered positive, indicating ankle instability, if radiographic imaging revealed syndesmotic widening of more than 5 mm (Fig. 3 ). Variables and outcome measures 1 Parallel Test Model In the combined test, if either the external rotation stress test or the Cotton test yielded a positive result, the combined test result was considered positive. Conversely, if both tests yielded negative results simultaneously, the combined test result was considered negative. 2. Statistical methods We processed the data via SPSS 26.0 statistical software. Count data are expressed as cases (thirty-two), and we performed intergroup comparisons via McNemar's test for paired designs for comprehensive statistical analysis. Statistical significance was set at P < 0.05. Results 1. The Cotton test demonstrated increased diagnostic accuracy for assessing deltoid ligament integrity The results of the use of the external rotation stress test for detecting deep deltoid ligament rupture were as follows: there were 10 false-negative cases, the sensitivity was 68.75%, the accuracy was 68.75%, and the missed diagnosis rate was 31.25%. The results of the Cotton test were as follows: there were 7 false-negative cases, the sensitivity was 78.13%, the accuracy was 78.13%, and the missed diagnosis rate was 21.88%. 2. Combining the Cotton test with the external rotation stress test enhances the sensitivity for detecting deep deltoid ligament ruptures The results of the combined application of both testing methods revealed that the sensitivity was 96.88%, the accuracy was 96.88%, and the missed diagnosis rate was 3.12%. The Cotton test appears to be more sensitive than the external rotation stress test, and both tests can lead to missed diagnoses. However, the combined application of the two methods significantly improved the diagnostic rate of deep deltoid ligament rupture, with a statistically significant difference when the combined application was compared with the external rotation stress test alone (P = 0.004 < 0.05, 95% CI: 0.110–0.452) and with the Cotton test alone (P = 0.031 < 0.05, 95% CI: 0.033–0.343). (Table 2 ) Table 2 Diagnostic value of the stress external rotation test, Cotton test, and their combination for deep deltoid ligament rupture of the medial malleolus (P < 0.05). Testing methods sensitivity(%) Missed diagnosis rate(%) accuracy(%) External rotation stress test 68.75% 31.25% 68.75% Cotton test 78.13% 21.88% 78.13% combined tests 96.88% 3.12% 96.88% Ρ(combination of tests vs Cotton test) 0.031 Ρ(combination of tests vs stress external rotation test) 0.004 Discussion 1 Important roles of the medial malleolus and deltoid ligament The deltoid ligament consists of two parts: a superficial layer and a deep layer. The superficial layer was divided into four bundles. The deep layer is composed of the posterior and anterior tibiotalar deep ligaments, with the former being the only consistently present structure[ 2 , 20 ]. The deltoid ligament is one of the most important anatomical structures that maintains ankle stability. Recent biomechanical studies have shown that both the deep and superficial layers of the deltoid ligament work together to restrict talar valgus and posterior displacement, whereas the deep layer plays a greater role in restricting talar external rotation and lateral displacement[ 22 ]. The deep layer of the ligament plays a decisive role in the medial stability of the ankle joint; therefore, diagnosing whether there is a rupture in the deep layer of the medial deltoid ligament is crucial[ 1 , 5 , 18 ]. 2 Diagnosis of medial deltoid ligament injury When an external rotation stress test is performed on a normal ankle joint, there is only a slight measurable tilt of the talus (mostly less than 2°). A tilt greater than 2° may indicate potential injury to the medial deltoid ligament[ 12 ]. The external rotation stress test has always been a useful tool and the "gold standard" for preoperative and intraoperative assessment of the stability of the medial structures in ankle torsion fractures[ 19 ]. Widening of the medial clear space of the ankle joint (≥ 4 mm) is considered a diagnostic basis for the presence of a deep deltoid ligament tear[ 6 , 11 , 15 , 21 ]. In some cases of deltoid ligament rupture, there is no separation of the syndesmosis (the lower tibiofibular joint) or widening of the medial ankle joint space on plain radiography, leading to a relatively high rate of misdiagnosis and missed diagnosis. Henari et al.[ 8 ] reported on 12 patients with deltoid ligament ruptures, 3 of whom presented with a normal medial clear space on radiography. Tornetta[ 13 ] reported that 26% of medial malleolar avulsion fractures were accompanied by tears of the deep deltoid ligament. In most of these cases, the medial malleolar fracture fragment was small, specifically located at the anterior tuberosity, with a fragment width of less than 1.7 cm. Doctors may easily overlook injuries to the deltoid ligament and fix only medial malleolar fractures. Owing to the untreated deep layer of the deltoid ligament, medial instability may occur; therefore, it is very important to perform the abovementioned external rotation stress test routinely after open reduction and internal fixation of the fracture. A medial clear space of ≥ 5 mm or lateral subluxation of the talus is indicative of deltoid ligament rupture[ 6 ]. Our findings indicate that the external rotation stress test, considered the “gold standard’’ for diagnosing deep deltoid ligament rupture, resulted in the diagnosis of only 22 cases, with 10 false negatives. This resulted in a missed diagnosis rate of 31.25%. After fracture fixation, we performed routine external rotation stress tests on the patients, followed by the Cotton test. The results revealed that the medial malleolar clear space increased to > 5 mm in 9 of the 10 patients who tested negative in the external rotation stress test. These findings indicate that the Cotton test is an important supplement to the external rotation stress test. Furthermore, we observed that the two tests cannot replace each other. In many cases, one test may be positive, whereas the other test may be negative. Although our sample size was small and we did not definitively establish that the Cotton test is more sensitive than the external rotation stress test for diagnosing deep deltoid ligament rupture, it was sufficient to suggest that the former is a useful supplement to the latter. Moreover, performing both tests simultaneously after fracture fixation can better determine the status of the deep deltoid ligament and more accurately assess ankle stability, thereby facilitating the formulation of a more appropriate treatment plan. Following open reduction and internal fixation (ORIF) of the fibular fracture and closed reduction internal fixation (CRIF) of the medial malleolus, intraoperative stress tests should be employed to assess the integrity of the deep deltoid ligament. If a rupture is confirmed, definitive surgical repair is indicated; if the ligament is intact, repair can be safely omitted, thereby avoiding unnecessary dissection and minimizing iatrogenic trauma. Henari et al.[ 8 ] reported that ultrasound has both a sensitivity and specificity of 100% for diagnosing deltoid ligament injuries, making it a useful and noninvasive diagnostic tool for medial deltoid ligament injuries in ankles. MRI has been reported to be accurate in diagnosing deltoid ligament injuries. However, Nortunen S et al.[ 16 ] reported that MRI results are not precise and do not recommend the use of MRI findings as an important reference factor in determining the treatment plan for ankle fractures. They suggested that the external rotation stress test can guide clinicians in deciding whether surgical treatment is needed for patients with lateral malleolar fractures and a normal medial clear space. We believe that the diagnostic accuracy of imaging examinations is highly dependent on the skill level of radiologists, and there are currently notable differences among various medical institutions. The use of dynamic stress ultrasonography for diagnosing medial ankle instability in patients with supination external rotation (SER) ankle injury appears to be a feasible tool[ 23 ]. However, it is not appropriate to rely solely on ultrasound or MRI examinations as the basis for diagnosing deep deltoid ligament ruptures of the medial malleolus. Although the external rotation stress test under intraoperative fluoroscopy remains the "gold standard" for diagnosing deltoid ligament injuries of the medial malleolus, our research revealed that this "gold standard" also has limitations, with some cases being missed by it. The Cotton test should be performed concurrently to improve the diagnostic rate of deltoid ligament rupture. Lacorda et al.[ 10 ] reported that the average latent period for the onset of posttraumatic arthritis following rotational ankle fractures was 21.1 years. Day G et al.[ 3 , 19 ] conducted a follow-up study with a minimum duration of 10 years and reported that the percentage of patients with moderate to severe posttraumatic arthritis among those who underwent open reduction and internal fixation for ankle fractures reached 36%. Milos et al.[ 14 ] reported that tears of the medial deltoid ligament can lead to chronic instability of the ankle joint, resulting in the development of medial ankle impingement syndrome. Ultimately, this can cause the cartilage of the talar dome to shed, leading to long-term pain on the medial side of the ankle joint. Femino et al.[ 4 ] also expressed their doubts regarding a clinically unconfirmed issue: whether rotational instability of the ankle joint due to deep deltoid ligament rupture truly exists. This could be an important underlying factor contributing to the high incidence of posttraumatic arthritis following rotational ankle fractures and ankle sprains. The cumulative effect of mild ankle rotational instability may explain the long latency period of posttraumatic arthritis. The aforementioned literature suggests that the high incidence and long latent period of posttraumatic arthritis of the ankle joint may be partially attributed to the chronic instability of the ankle joint caused by deep deltoid ligament ruptures, which could be an important contributing factor. This raises an urgent question: how can we make a definitive diagnosis of deep deltoid ligament ruptures of the medial malleolus? We hope that the method combining the external rotation stress test with the Cotton test presented in this article can be beneficial for improving the diagnosis of deep deltoid ligament ruptures. Conclusions For the diagnosis of deep deltoid ligament ruptures of the medial malleolus, the external rotation stress test still has a relatively high rate of missed diagnoses. The Cotton test serves as a useful supplement, and performing both tests together can increase the detection rate. The accurate diagnosis of deep deltoid ligament rupture offers a reliable basis for determining next-step treatment strategies, which in turn minimizes the occurrence of posttraumatic ankle instability. Declarations Ethics approval and consent to participate This study involving human subjects was approved by the Medical Ethics Committee of Jining Medical University Affiliated Hospital (Approval Number: 2025-11-C022). All procedures were conducted in accordance with the Declaration of Helsinki and JOSR’s policy on human subject protection. Informed consent was obtained from all participants (or their legally authorized representatives for minors/incapacitated individuals) prior to study enrollment. Consent for publication Not applicable Competing interests The authors declare that they have no competing interests. Funding This study was supported by the “2023 Jining City Key R & D Program Fund” (no. 2023YXNS203). Author Contribution Z.J. designed the study,conducted the tests,collected the data, analyzed the data and wrote the manuscript. X-Y.G. collected the data. R.Z. interpreted the data and edited the manuscript. X-J.M. collected the data and wrote the manuscript.D-L.J. designed the study analyzed the data. H-B.W. designed the study.Y-F.Z.designed the study and conducted the tests. X.Z. designed theStudy the data and wrote the manuscript. All authors have read and approved the final submitted manuscript. Acknowledgement The authors would like to thank our department colleagues, the Affiliated Hospital of Jining Medical University (Jining City, China), and these patients for their dedication. Data Availability The datasets used and/or anaed during the current study are available fromthe corresponding author on reasonable request. References Balasubramanian, N. 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Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 12 Feb, 2026 Editor assigned by journal 12 Feb, 2026 Editor invited by journal 12 Feb, 2026 Submission checks completed at journal 10 Feb, 2026 First submitted to journal 10 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8791887","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":590403081,"identity":"dcc516d9-ec5f-4d63-a371-f18e61d24878","order_by":0,"name":"Zhen Jiang","email":"","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zhen","middleName":"","lastName":"Jiang","suffix":""},{"id":590403085,"identity":"b07b4715-9c7b-4bfc-81fd-495b47f1fb0e","order_by":1,"name":"Xiaoyan Guo","email":"","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xiaoyan","middleName":"","lastName":"Guo","suffix":""},{"id":590403087,"identity":"c0d67680-2867-461e-88f1-1a811e84a341","order_by":2,"name":"Rui Zhang","email":"","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Zhang","suffix":""},{"id":590403089,"identity":"42d49de3-fe62-413c-b835-8a64cc1db5d4","order_by":3,"name":"Xiangji Meng","email":"","orcid":"","institution":"Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xiangji","middleName":"","lastName":"Meng","suffix":""},{"id":590403090,"identity":"5662aa34-587e-4506-af1b-50e2dd4aa6a6","order_by":4,"name":"Dailiang Jia","email":"","orcid":"","institution":"Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Dailiang","middleName":"","lastName":"Jia","suffix":""},{"id":590403091,"identity":"e65d6b83-163f-4878-9655-99d70524d7ea","order_by":5,"name":"Haibin Wang","email":"","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Haibin","middleName":"","lastName":"Wang","suffix":""},{"id":590403092,"identity":"a257bdb3-0b9f-41c5-8857-df62160147f8","order_by":6,"name":"Yifeng Zhao","email":"","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yifeng","middleName":"","lastName":"Zhao","suffix":""},{"id":590403094,"identity":"8a8e86d1-994f-4229-93a4-50c2507067ba","order_by":7,"name":"Xu Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYLACxgYgwcx88EFCRQ0pWtjZkg0enDlGihZ+HjXJhy3MhFWbs/cefPhzh12evDMPW0ViAxsDf3t3Al4tlj3nkg0kzyQXGx7mPXYjcYcMg8SZsxvwajG4kWMmYdjGnLixmS/tRuIZNgYDiVyCWsx/JLbVA7XwmBUktjETpcWM4WDb4cT5zDxmDERpAflFsrHteOIGZrZkiYQzx3gI+gUUYh9/tlUnzu8/fPDjj4oaOf72XgIOY+CBMg5AaB68ylG0yDcQVDsKRsEoGAUjFQAA5JpLn/BGwqIAAAAASUVORK5CYII=","orcid":"","institution":"Affiliated Hospital of Jining Medical University","correspondingAuthor":true,"prefix":"","firstName":"Xu","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2026-02-05 03:53:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8791887/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8791887/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102991616,"identity":"213cfc53-b217-4848-b567-a5adbd7e91c1","added_by":"auto","created_at":"2026-02-19 11:34:31","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":50822,"visible":true,"origin":"","legend":"\u003cp\u003eDiagnostic confirmation of a pronation-external rotation ankle injury.\u003cbr\u003e\nF1A. Radiograph revealing a widened medial clear space, consistent with a suspected deep deltoid ligament injury.\u003c/p\u003e\n\u003cp\u003eF1B. Surgical view confirming the deep deltoid ligament rupture.\u003cbr\u003e\nF1C. Intraoperative external rotation stress test yielding a negative (mildly abnormal) result.\u003cbr\u003e\nF1D. Positive Cotton test, indicating syndesmotic disruption and medial clear space gapping.\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8791887/v1/acaba8d5d94d8fe88d178806.jpg"},{"id":102991618,"identity":"5912970b-3c75-460c-9260-5526a5f7298e","added_by":"auto","created_at":"2026-02-19 11:34:31","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":57850,"visible":true,"origin":"","legend":"\u003cp\u003eDiagnostic confirmation of a supination-external rotation ankle fracture.\u003cbr\u003e\nF2A. Point tenderness over the medial malleolus, raising suspicion for deltoid ligament involvement.\u003cbr\u003e\nF2B. MRI confirmation of a deep deltoid ligament rupture(Red arrow).\u003cbr\u003e\nF2C. Post-fixation radiograph after lateral malleolar stabilization.\u003cbr\u003e\nF2D. Negative Cotton test, ruling out significant syndesmotic diastasis.\u003cbr\u003e\nF2E. Positive external rotation stress test, verifying persistent medial instability.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8791887/v1/ad96eba9001569ed8f78b71a.jpg"},{"id":103050057,"identity":"ae762b0d-bf8f-4d76-b6e7-2339225b7192","added_by":"auto","created_at":"2026-02-20 07:47:53","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":89764,"visible":true,"origin":"","legend":"\u003cp\u003eIntraoperative Cotton test. A lateral traction force (F≈71.9N) was applied to the fibula, resulting in a positive test as evidenced by a clear syndesmotic diastasis of \u0026gt;2 mm.\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8791887/v1/074cb6c7a0a465597b3543c5.jpg"},{"id":103051595,"identity":"59557abb-47c9-43b7-bbae-1d074ba18932","added_by":"auto","created_at":"2026-02-20 08:01:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":872440,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8791887/v1/61b431ff-6b61-431a-97ca-9b2e947568c1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Rupture of the Deep Layer of the Deltoid Ligament: Is the External Rotation Stress Test Diagnostic?","fulltext":[{"header":"Background","content":"\u003cp\u003eAnkle fractures can be classified as stable or unstable. Stable fractures have a good prognosis with nonsurgical treatment, whereas unstable fractures commonly necessitate surgical reduction and maintenance in a stable position. Otherwise, the prognosis will be poor. The presence or absence of a medial ankle injury is key to diagnosing whether an ankle fracture is stable. Injury to the medial ankle encompasses both medial malleolar fractures and deltoid ligament injuries. Medial malleolar fractures are easy to diagnose, and a consensus is that they require reduction and stable fixation. There is controversy surrounding the treatment of deltoid ligament injuries[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The timing and accuracy of diagnosing deltoid ligament rupture hold significant clinical relevance, irrespective of the subsequent therapeutic pathway\u0026mdash;be it surgical intervention or conservative management.\u003c/p\u003e \u003cp\u003eLigament injuries are not visible on conventional DR (digital radiography) and CT (computed tomography) scans, especially when the medial malleolar space is normal or not significantly widened, which can easily lead to missed diagnoses or misdiagnosed cases, causing patients to miss the best treatment timing or choose the wrong treatment plan. For pure-ligament injuries, whether the deep layer of the deltoid ligament is ruptured is a critical factor in determining ankle joint stability. The external rotation stress test is considered the gold standard for the clinical diagnosis of deep deltoid ligament ruptures[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFinding new and effective diagnostic measures is extremely important for confirming deep deltoid ligament rupture at the medial malleolus. The Cotton test is widely used in clinical practice and plays a crucial role in diagnosing deltoid ligament ruptures. However, its diagnostic value for deep deltoid ligament rupture remains unclear. This study analyzed the diagnostic effectiveness of the external rotation stress test and Cotton test, individually and unitedly, for detecting deep deltoid ligament ruptures. We conducted these tests on patients who were already diagnosed with such ruptures at the medial malleolus. This study aimed to enhance the diagnostic basis for deep deltoid ligament ruptures at the medial malleolus by uniquely evaluating the efficacy of the combined application of the external rotation stress test and Cotton test. Despite the perceived utility of the external rotation stress test, preliminary observations suggest a potentially high rate of missed diagnoses, which this study aims to explore, particularly in combination with the Cotton test.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThe inclusion criteria were as follows: (1) aged 22\u0026ndash;65 years; (2) had closed ankle fractures; and (3) had confirmed deep deltoid ligament ruptures at the medial malleolus (diagnosed as follows: 1. Magnetic resonance imaging (MRI) revealing deep deltoid ligament rupture; 2. Direct intraoperative visualization and palpation of the ruptured ligament). DR findings were used as index test results, not as part of the reference standard for rupture confirmation[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. ).\u003c/p\u003e \u003cp\u003eThe exclusion criteria were as follows: (1) patients with multiple underlying diseases who could not tolerate surgery and (2) patients with poor compliance due to mental disorders.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy subjects\u003c/h2\u003e \u003cp\u003eWe retrospectively analyzed data from thirty-two patients with ankle fractures and deep deltoid ligament ruptures between October 2012 and January 2023. After the reduction and fixation of ankle fractures were completed, we routinely performed an external rotation stress test for all different types of fractures (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These patients met the criteria for deep deltoid ligament ruptures at the medial malleolus, and their ages ranged from 22\u0026ndash;65 years. The Lauge\u0026ndash;Hansen classification system[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] included seventeen cases of supination\u0026ndash;external rotation type IV injuries, nine cases of pronation\u0026ndash;external rotation type IV injuries, four cases of pronation\u0026ndash;abduction type III injuries, and two cases of supination\u0026ndash;adduction type II injuries (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLauge-hansen classification and results of the Cotton test and stress external rotation test in cases\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecase\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCotton test\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExternal rotation stress test\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLauge-Hansen classification\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination-adduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;abduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase 20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;abduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;abduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;external rotation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003esupination-adduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCase32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003epronation\u0026ndash;abduction\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e+: Positive,-: Feminine.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eDescription of the surgery\u003c/b\u003e \u003c/p\u003e \u003cp\u003eWe administered spinal or combined spinal\u0026ndash;epidural anesthesia and applied a thigh tourniquet to the affected side. Anatomical reduction and fixation of the fibula followed. If the posterior malleolar fracture was \u0026ge;\u0026thinsp;25% in size, it was fixed with screws or a buttress plate. Medial malleolar fractures are routinely treated with open reduction and fixation via cannulated screws or K-wires for anatomical reduction. After fixation, standard ankle mortise DR examinations, external rotation stress tests, and Cotton tests were performed. In our hands, the modified Cotton test was performed as follows: with the foot and ankle stabilized, a pointed reduction clamp was applied to perform lateral traction to the fibula. A force of 58.8\u0026ndash;88.2 N was used (based on the patient's weight, F\u0026thinsp;=\u0026thinsp;0.98 N/kg, F\u0026thinsp;=\u0026thinsp;mg, g\u0026thinsp;=\u0026thinsp;9.8 m/s\u0026sup2;). The test was considered positive, indicating ankle instability, if radiographic imaging revealed syndesmotic widening of more than 5 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eVariables and outcome measures\u003c/b\u003e \u003c/p\u003e \u003cp\u003e1 Parallel Test Model\u003c/p\u003e \u003cp\u003eIn the combined test, if either the external rotation stress test or the Cotton test yielded a positive result, the combined test result was considered positive. Conversely, if both tests yielded negative results simultaneously, the combined test result was considered negative.\u003c/p\u003e \u003cp\u003e2. Statistical methods\u003c/p\u003e \u003cp\u003eWe processed the data via SPSS 26.0 statistical software. Count data are expressed as cases (thirty-two), and we performed intergroup comparisons via McNemar's test for paired designs for comprehensive statistical analysis. Statistical significance was set at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e1. The Cotton test demonstrated increased diagnostic accuracy for assessing deltoid ligament integrity\u003c/p\u003e \u003cp\u003eThe results of the use of the external rotation stress test for detecting deep deltoid ligament rupture were as follows: there were 10 false-negative cases, the sensitivity was 68.75%, the accuracy was 68.75%, and the missed diagnosis rate was 31.25%. The results of the Cotton test were as follows: there were 7 false-negative cases, the sensitivity was 78.13%, the accuracy was 78.13%, and the missed diagnosis rate was 21.88%.\u003c/p\u003e \u003cp\u003e2. Combining the Cotton test with the external rotation stress test enhances the sensitivity for detecting deep deltoid ligament ruptures\u003c/p\u003e \u003cp\u003eThe results of the combined application of both testing methods revealed that the sensitivity was 96.88%, the accuracy was 96.88%, and the missed diagnosis rate was 3.12%. The Cotton test appears to be more sensitive than the external rotation stress test, and both tests can lead to missed diagnoses. However, the combined application of the two methods significantly improved the diagnostic rate of deep deltoid ligament rupture, with a statistically significant difference when the combined application was compared with the external rotation stress test alone (P\u0026thinsp;=\u0026thinsp;0.004\u0026thinsp;\u0026lt;\u0026thinsp;0.05, 95% CI: 0.110\u0026ndash;0.452) and with the Cotton test alone (P\u0026thinsp;=\u0026thinsp;0.031\u0026thinsp;\u0026lt;\u0026thinsp;0.05, 95% CI: 0.033\u0026ndash;0.343). (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDiagnostic value of the stress external rotation test, Cotton test, and their combination for deep deltoid ligament rupture of the medial malleolus (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting methods\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003esensitivity(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMissed diagnosis rate(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eaccuracy(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExternal rotation stress test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e68.75%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.25%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e68.75%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCotton test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e78.13%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.88%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e78.13%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecombined tests\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e96.88%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.12%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e96.88%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eΡ(combination of tests \u003cb\u003evs\u003c/b\u003e Cotton test)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c5\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eΡ(combination of tests \u003cb\u003evs\u003c/b\u003e stress external rotation test)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c5\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e1 Important roles of the medial malleolus and deltoid ligament\u003c/p\u003e \u003cp\u003eThe deltoid ligament consists of two parts: a superficial layer and a deep layer. The superficial layer was divided into four bundles. The deep layer is composed of the posterior and anterior tibiotalar deep ligaments, with the former being the only consistently present structure[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The deltoid ligament is one of the most important anatomical structures that maintains ankle stability. Recent biomechanical studies have shown that both the deep and superficial layers of the deltoid ligament work together to restrict talar valgus and posterior displacement, whereas the deep layer plays a greater role in restricting talar external rotation and lateral displacement[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The deep layer of the ligament plays a decisive role in the medial stability of the ankle joint; therefore, diagnosing whether there is a rupture in the deep layer of the medial deltoid ligament is crucial[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e2 Diagnosis of medial deltoid ligament injury\u003c/p\u003e \u003cp\u003eWhen an external rotation stress test is performed on a normal ankle joint, there is only a slight measurable tilt of the talus (mostly less than 2\u0026deg;). A tilt greater than 2\u0026deg; may indicate potential injury to the medial deltoid ligament[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The external rotation stress test has always been a useful tool and the \"gold standard\" for preoperative and intraoperative assessment of the stability of the medial structures in ankle torsion fractures[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Widening of the medial clear space of the ankle joint (\u0026ge;\u0026thinsp;4 mm) is considered a diagnostic basis for the presence of a deep deltoid ligament tear[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In some cases of deltoid ligament rupture, there is no separation of the syndesmosis (the lower tibiofibular joint) or widening of the medial ankle joint space on plain radiography, leading to a relatively high rate of misdiagnosis and missed diagnosis. Henari et al.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] reported on 12 patients with deltoid ligament ruptures, 3 of whom presented with a normal medial clear space on radiography. Tornetta[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] reported that 26% of medial malleolar avulsion fractures were accompanied by tears of the deep deltoid ligament. In most of these cases, the medial malleolar fracture fragment was small, specifically located at the anterior tuberosity, with a fragment width of less than 1.7 cm. Doctors may easily overlook injuries to the deltoid ligament and fix only medial malleolar fractures. Owing to the untreated deep layer of the deltoid ligament, medial instability may occur; therefore, it is very important to perform the abovementioned external rotation stress test routinely after open reduction and internal fixation of the fracture. A medial clear space of \u0026ge;\u0026thinsp;5 mm or lateral subluxation of the talus is indicative of deltoid ligament rupture[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur findings indicate that the external rotation stress test, considered the \u0026ldquo;gold standard\u0026rsquo;\u0026rsquo; for diagnosing deep deltoid ligament rupture, resulted in the diagnosis of only 22 cases, with 10 false negatives. This resulted in a missed diagnosis rate of 31.25%. After fracture fixation, we performed routine external rotation stress tests on the patients, followed by the Cotton test. The results revealed that the medial malleolar clear space increased to \u0026gt;\u0026thinsp;5 mm in 9 of the 10 patients who tested negative in the external rotation stress test. These findings indicate that the Cotton test is an important supplement to the external rotation stress test. Furthermore, we observed that the two tests cannot replace each other. In many cases, one test may be positive, whereas the other test may be negative. Although our sample size was small and we did not definitively establish that the Cotton test is more sensitive than the external rotation stress test for diagnosing deep deltoid ligament rupture, it was sufficient to suggest that the former is a useful supplement to the latter. Moreover, performing both tests simultaneously after fracture fixation can better determine the status of the deep deltoid ligament and more accurately assess ankle stability, thereby facilitating the formulation of a more appropriate treatment plan. Following open reduction and internal fixation (ORIF) of the fibular fracture and closed reduction internal fixation (CRIF) of the medial malleolus, intraoperative stress tests should be employed to assess the integrity of the deep deltoid ligament. If a rupture is confirmed, definitive surgical repair is indicated; if the ligament is intact, repair can be safely omitted, thereby avoiding unnecessary dissection and minimizing iatrogenic trauma.\u003c/p\u003e \u003cp\u003eHenari et al.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] reported that ultrasound has both a sensitivity and specificity of 100% for diagnosing deltoid ligament injuries, making it a useful and noninvasive diagnostic tool for medial deltoid ligament injuries in ankles. MRI has been reported to be accurate in diagnosing deltoid ligament injuries. However, Nortunen S et al.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] reported that MRI results are not precise and do not recommend the use of MRI findings as an important reference factor in determining the treatment plan for ankle fractures. They suggested that the external rotation stress test can guide clinicians in deciding whether surgical treatment is needed for patients with lateral malleolar fractures and a normal medial clear space. We believe that the diagnostic accuracy of imaging examinations is highly dependent on the skill level of radiologists, and there are currently notable differences among various medical institutions. The use of dynamic stress ultrasonography for diagnosing medial ankle instability in patients with supination external rotation (SER) ankle injury appears to be a feasible tool[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. However, it is not appropriate to rely solely on ultrasound or MRI examinations as the basis for diagnosing deep deltoid ligament ruptures of the medial malleolus.\u003c/p\u003e \u003cp\u003eAlthough the external rotation stress test under intraoperative fluoroscopy remains the \"gold standard\" for diagnosing deltoid ligament injuries of the medial malleolus, our research revealed that this \"gold standard\" also has limitations, with some cases being missed by it. The Cotton test should be performed concurrently to improve the diagnostic rate of deltoid ligament rupture. Lacorda et al.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] reported that the average latent period for the onset of posttraumatic arthritis following rotational ankle fractures was 21.1 years. Day G et al.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] conducted a follow-up study with a minimum duration of 10 years and reported that the percentage of patients with moderate to severe posttraumatic arthritis among those who underwent open reduction and internal fixation for ankle fractures reached 36%. Milos et al.[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] reported that tears of the medial deltoid ligament can lead to chronic instability of the ankle joint, resulting in the development of medial ankle impingement syndrome. Ultimately, this can cause the cartilage of the talar dome to shed, leading to long-term pain on the medial side of the ankle joint. Femino et al.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] also expressed their doubts regarding a clinically unconfirmed issue: whether rotational instability of the ankle joint due to deep deltoid ligament rupture truly exists. This could be an important underlying factor contributing to the high incidence of posttraumatic arthritis following rotational ankle fractures and ankle sprains. The cumulative effect of mild ankle rotational instability may explain the long latency period of posttraumatic arthritis. The aforementioned literature suggests that the high incidence and long latent period of posttraumatic arthritis of the ankle joint may be partially attributed to the chronic instability of the ankle joint caused by deep deltoid ligament ruptures, which could be an important contributing factor. This raises an urgent question: how can we make a definitive diagnosis of deep deltoid ligament ruptures of the medial malleolus? We hope that the method combining the external rotation stress test with the Cotton test presented in this article can be beneficial for improving the diagnosis of deep deltoid ligament ruptures.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eFor the diagnosis of deep deltoid ligament ruptures of the medial malleolus, the external rotation stress test still has a relatively high rate of missed diagnoses. The Cotton test serves as a useful supplement, and performing both tests together can increase the detection rate. The accurate diagnosis of deep deltoid ligament rupture offers a reliable basis for determining next-step treatment strategies, which in turn minimizes the occurrence of posttraumatic ankle instability.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eThis study involving human subjects was approved by the Medical Ethics Committee of Jining Medical University Affiliated Hospital (Approval Number: 2025-11-C022). All procedures were conducted in accordance with the Declaration of Helsinki and JOSR\u0026rsquo;s policy on human subject protection. Informed consent was obtained from all participants (or their legally authorized representatives for minors/incapacitated individuals) prior to study enrollment.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported by the \u0026ldquo;2023 Jining City Key R \u0026amp; D Program Fund\u0026rdquo; (no. 2023YXNS203).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZ.J. designed the study,conducted the tests,collected the data, analyzed the data and wrote the manuscript. X-Y.G. collected the data. R.Z. interpreted the data and edited the manuscript. X-J.M. collected the data and wrote the manuscript.D-L.J. designed the study analyzed the data. H-B.W. designed the study.Y-F.Z.designed the study and conducted the tests. X.Z. designed theStudy the data and wrote the manuscript. All authors have read and approved the final submitted manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to thank our department colleagues, the Affiliated Hospital of Jining Medical University (Jining City, China), and these patients for their dedication.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or anaed during the current study are available fromthe corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBalasubramanian, N. 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(Bristol Avon)\u003c/em\u003e. \u003cb\u003e27\u003c/b\u003e (2), 189\u0026ndash;195. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.clinbiomech.2011.08.015\u003c/span\u003e\u003cspan address=\"10.1016/j.clinbiomech.2011.08.015\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2012).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSaengsin, J. et al. Ultrasonography for diagnosing medial sided ankle instability in supination external rotation ankle fracture[J]. \u003cem\u003eJ. Orthop. Surg. Res.\u003c/em\u003e \u003cb\u003e20\u003c/b\u003e (1). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1186/s13018-025-05645-y\u003c/span\u003e\u003cspan address=\"10.1186/s13018-025-05645-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Deltoid ligament, Diagnosis, External rotation stress test, Cotton test","lastPublishedDoi":"10.21203/rs.3.rs-8791887/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8791887/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe integrity of the deep layer of the deltoid ligament is a critical determinant of ankle joint stability. The external rotation stress test, a common physical examination for assessing medial structural integrity, has suboptimal diagnostic sensitivity, potentially leading to false negative findings.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eAccording to the Lauge-Hansen classification,seventeen patients were diagnosed with supination-external rotation type IV, nine patients were diagnosed with pronation-external rotation type IV,four patients were diagnosed with pronation-abduction type III, and two patients were diagnosed with supination-adduction type II. Eleven patients were preoperatively diagnosed with deep deltoid ligament rupture (with a medial malleolar gap\u0026ge;5mm compared to the contralateral side or with lateral subluxation/dislocation of the talus).Twenty-one patients were intraoperatively diagnosed with deep deltoid ligament rupture (with a medial malleolar gap\u0026ge;5mm or lateral subluxation of the talus after reduction of the ankle fracture, as demonstrated by a positive external rotation stress test or Cotton test). All patients underwent external rotation stress and Cotton testing.A comparative analysis of the diagnostic performance for deep deltoid ligament rupture was conducted between the individual and combined application of the two tests. Statistical analyses were performed via SPSS software (version 26.0), with a P value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 considered statistically significant.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe results of the external rotation stress test, the Cotton test, and the combined application of both testing methods were as follows: the accuracies were 68.75%, 78.13%, and 96.88%, respectively, and the missed diagnosis rates were 31.25%, 21.88%, and 3.12%, respectively. These tests can lead to missed diagnoses, and the Cotton test appears to be more sensitive than the external rotation stress test. Moreover, the combined application of the two methods significantly improved the diagnostic rate of deep deltoid ligament rupture compared with the external rotation stress test (P\u0026thinsp;=\u0026thinsp;0.004\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and the Cotton test (P\u0026thinsp;=\u0026thinsp;0.031\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe external rotation stress test, a commonly used method for physical examination of the ankle joint, demonstrated limitations in diagnosing deep deltoid ligament ruptures in this cohort. Therefore, the Cotton test and external rotation stress test should be performed together to improve the positive rate.\u003c/p\u003e","manuscriptTitle":"Rupture of the Deep Layer of the Deltoid Ligament: Is the External Rotation Stress Test Diagnostic?","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-19 11:34:09","doi":"10.21203/rs.3.rs-8791887/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-02-12T09:46:12+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-12T09:31:01+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-12T06:32:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-10T08:29:21+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-02-10T07:56:32+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"371755db-1cd8-4d51-8468-15288091589b","owner":[],"postedDate":"February 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":62828258,"name":"Health sciences/Anatomy"},{"id":62828259,"name":"Health sciences/Diseases"},{"id":62828260,"name":"Health sciences/Health care"},{"id":62828261,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2026-02-19T11:34:09+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-19 11:34:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8791887","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8791887","identity":"rs-8791887","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}