The SP-ET Index is a New Index for Assessing The Vertical Position of Patella

The SP-ET Index is a New Index for Assessing The Vertical Position of Patella | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research article The SP-ET Index is a New Index for Assessing The Vertical Position of Patella Jia Li, Lanyu Qiu, Bo Sheng, Fan Yu, Haitao Yang, Furong Lv, Fajin Lv, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-957545/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background. There were some parameters in previous studies did not better reflect the vertical position of the patella relative to the femoral trochlear. The purposes of this study were to assess the value of the most superior point of patella - entrance of femoral trochlea distance ratio (SP-ET index) as a newer index in defining the vertical position of patella relative to the trochlea, correlate it with the Insall-Salvati ratio, and investigate the effect of the new index on chondromalacia patella. Methods. A total of 99 knees of 77 patients with chondromalacia patella were retrospectively analyzed using magnetic resonance imaging (MRI) data from our database. The Insall–Salvati ratio and SP-ET index were measured on MR images. There were 99 knees just with meniscus rupture were enrolled as the control group. The two parameters of the chondromalacia patella were compared with those of the control group. Results. The Insall–Salvati ratio and SP-ET index in the chondromalacia patella group were significantly higher than those in the control group ( p < 0.001). The SP-ET index showed a moderate positive correlation with the Insall–Salvati ratio ( r =0.307, p <0.001). Receiver operating characteristic (ROC) analysis showed the diagnostic efficiency of the SP-ET index was better than that of the Insall–Salvati ratio in patients with chondromalacia patella. Conclusion. The SP-ET index may be a useful complement parameter to define the vertical position of the patella relative to the femoral trochlear. Increased of the SP-ET index may be an important risk factor for chondromalacia patella. Orthopedics Orthopedic Surgery Chondromalacia patella the SP-ET index The Insall–Salvati ratio Patellofemoral joint vertical position Figures Figure 1 Figure 2 Figure 3 Figure 4 Background The primary anatomical factors which were associated with patellofemoral malalignment included: patella alta, trochlear dysplasia, and abnormal lateral patellar tilt [ 1 , 2 ]. Patellofemoral malalignment resulted in abnormal joint contact and chondral stresses within the patellofemoral compartment, and often associated with chondral damage and chronic anterior knee pain [ 3 ]. Chondromalacia patella is characterized by softening, swelling, fissuring or fraying of the patellar cartilage and can lead to a decrease in quality of life, it is one of common causes of chronic anterior knee pain [ 4 – 6 ]. A progressive loss of articular cartilage can lead to the development of patellofemoral osteoarthritis[ 7 , 8 ]. The most commonly cited hypothesis is patellofemoral malalignment and/or maltracking leads to pathological loadings on the patellofemoral joint, and increases subsequent articular cartilage wear[ 8 , 9 ], and we found that there have been several studies focusing on the relationship between patellofemoral malalignment and chondromalacia patella. Duran S et al[ 10 ] and Tuna BK et al[ 5 ] were reported that there was an association between abnormal trochlear morphology and chondromalacia patella in women. In addition, the study of Tabary M et al showed that the patellar height might be an important factor in the severity of chondromalacia patella[ 11 ]. In the study by Deniz Özel, both patella alta and patella baja were found to be related to chondromalacia patella, and the modified Insall-Salvati index ratio was the best indicator to define patella alta[ 12 ]. Patella alta may cause excessive lateral motion of the patella during knee flexion[ 13 ], and cause the patella may not be able to engage the trochlear groove early in knee flexion[ 14 ], all of these could the development of chondromalacia patella. Multiple methods of assessing the vertical position of the patella on imaging have been described in previous literature[ 14 , 15 ]. Most noteworthy, some studies suggested that the ratio between the articular cartilage of the patella and the trochlear cartilage (parameters Patellotrochlear index[ 16 ] and Patellar Articular Overlap[ 14 ]) could be better used to assess the vertical position of the patella in patients with patellofemoral instability. In addition, there were some researches focusing on the role of trochlear dysplasia in chondromalacia patella or patellofemoral cartilage lesions[ 8 , 10 , 17 ], and the study of Ambra LF et al[ 8 ] suggested that trochlear dysplasia might be more important than the patellar malposition in the pathogenesis of patellofemoral cartilage lesions. But the measurement parameters defining the vertical position of the patella in some studies did not better reflect the vertical position of the patella relative to the femoral trochlear as Patellotrochlear index[ 16 ] and Patellar Articular Overlap[ 14 ] do. Therefore, the present study aimed to identify the ratio of the most superior point of patella-entrance of femoral trochlea distance to the length of the patella articular surface on sagittal MRI as a newer index which can define the vertical position of patella relative to the trochlea, and investigate the effect of this parameter on chondromalacia patella. We hypothesized that the new parameter was a good indicator to define the vertical position of the patella, moreover, increased of this parameter might be a potential risk factor for developing chondromalacia patella. Materials And Methods Participants This retrospective study was approved by the Committee for Human Research of our institution (No. 2021-203). We retrospectively reviewed patients who were diagnosed with the modified Noyes classification system grade 1-2B chondromalacia patella based on MRI between January 2020 to April 2021 using picture archiving and communication systems at our department. Inclusion criteria were as follows: (1) patients with typical clinical presentation and MR signs with chondromalacia patella; (2) the flexion angle of the knee in MR images was 0-10°. Exclusion criteria were as follows: (1) participants with a history of traumatism or surgery of the knee; (2) presence of patellar dislocation, meniscus or ligamentous lesions; (3) presence of severe osteoarthritis (≥ KL 3 grade) or inflammatory arthritis; and (4) poor MR image quality (Fig. 1). In order to obtain a control group of participants without anterior knee pain and without any detectable alignment abnormalities or structural lesions on MRI and arthroscopy, patients undergoing meniscus rupture repair were chosen. All the clinical information was acquired by reviewing the clinical records or collected by telephone for medical history if uncertain on records. MRI protocol MRI was performed using 1.5-T MRI equipment (Magnetom Essenza; Siemens Healthcare) with an extremity matrix knee coil (a Tim coil). The imaging protocol was as follows: sagittal and coronal T1 turbo spin echo (repetition time/echo time 306/ 12 ms, field of view 16 cm, matrix size 320 × 320, slice thickness 4 mm), sagittal T2 turbo spin echo (repetition time/echo time 3220/99 ms, field of view 16 cm, matrix size 320 × 320, slice thickness 4 mm), sagittal and coronal intermediate-weighted turbo spin echo with fat saturation (repetition time/echo time 2800/38 ms, field of view 16 cm, matrix size 256 × 256, slice thickness 4 mm), and axial intermediate-weighted turbo spin echo with fat saturation (repetition time/echo time 2800/51 ms, field of view 16 cm, matrix size 232 × 256, slice thickness 4 mm). Image analyses All MRI images were independently reviewed by two musculoskeletal radiologists (Qiu and Sheng, with 3 and 13 years of clinical experience respectively). The routine MR imaging protocol were used to grade the articular cartilage on the patellofemoral joint according to the modified Noyes classification system: grade 0= normal cartilage, grade 1= increased T2 signal intensity of morphologically normal cartilage, grade 2A = superficial partial-thickness cartilage defect less than 50% of total articular surface thickness, grade 2B = deep partial-thickness cartilage defect greater than 50% of the total articular surface thickness, and grade 3 = full thickness cartilage defect [18, 19] (Fig. 2). The MRI measurements were performed by two other fellowship-trained musculoskeletal radiologists (Li and Yu, with 7 and 18 years of clinical experience respectively) after all the data of the two groups were mixed and blindly and randomly distributed. All measurements were repeated by one of the radiologists (Li), and the interval between the first and second reading was at last 4 weeks. Two quantitative parameters for evaluating patellar position were assessed on the images of each MRI examination. The Insall–Salvati ratio was calculated as the patellar tendon length divided by the maximum patellar diagonal length on sagittal MRI image (Fig. 3a). The Insall–Salvati ratio was used to reflect the height of the patella, and the threshold was defined as >1.2[20]. The most superior point of patella - entrance of femoral trochlea distance ratio (SP-ET index) was used to reflected the vertical position of the patella relative to the trochlea. The entrance of femoral trochlea was the first craniocaudal plane where the complete cartilaginous trochlea can be seen[21, 22]. The sagittal plain with the greatest longitudinal diameter of the patella was used to obtain the SP-ET index which was calculated as the distance between the most superior point of patella and the entrance of femoral trochlea divided by the patellar articular surface length (Fig. 3b-c). Statistical tests In this study, descriptive data were calculated for demographic data. The subjects were categorized, according to the inclusion and exclusion criteria, into the chondromalacia patella group and the control group. Intraclass correlation coefficients (ICCs) were used to assess the intra- and inter-reader reliability of MRI quantitative measures. Continuous variables with a normal distribution were expressed as mean ± standard deviation, and Student’s t test was used to detect the difference. The Spearman correlation was used to analyze the relationship between the two parameters. The above statistical analyses were performed using Windows software SPSS (version 17.0; SPSS, Chicago, IL, USA), and the significance level was set at 0.05. In addition, the diagnostic efficacy of two measurements of the patellar position were determined with receiver operating characteristic (ROC) curve analyses, it was performed using MedCalc statistical software (Med-Calc Software, Mariakerke, Belgium). Optimum cut-off point, sensitivity, specificity, and area under the curve (AUC) of each parameter were calculated, then, comparisons of ROC curves between the two groups, and the significance level was set at 0.05. Results Demographic characteristics of the subjects in the two groups During the study period, there was a total of 99 knees (25 left, 30 right, and 22 bilateral) of 77 patients (45 males and 32 females, age range 23–50 years, mean age 43 ± 7 years) were included in the chondromalacia patella group. There were 99 knees (51 left, 42 right, and 3 bilateral) of 96 participants (62 males and 34 females, age range 17–45 years, mean age 33 ± 8 years) in the control group (Table. 1). Intra- And Inter-observer Reliability Of Quantitative Mri Measurements The intra-reader ICCs for the SP-ET index and Insall–Salvati ratio quantitative measurements were 0.930 and 0.875, respectively. and the inter-reader ICCs for the SP-ET index and Insall–Salvati ratio were 0.890 and 0.973, respectively, as shown in Table. 2, indicating good intra and inter-reader reliability. Comparison between the chondromalacia patella group and control group and the correlation between the two parameters The two measurement parameters showed significant differences between chondromalacia patella group and control group. The Insall–Salvati ratio and SP-ET index in the chondromalacia patella group were significantly higher than those in the control group ( p < 0.001) (Table. 3). The SP-ET index showed a moderate positive correlation with the Insall–Salvati ratio ( r =0.307, p <0.001). Roc Analyses Of Mri Quantitative Measurements The ROC curves of the Insall–Salvati ratio and SP-ET index were generated (Table 4 , Fig. 4 ). The area under the curve (AUC) of the SP-ET index was 0.803 (95% CI 0.740–0.856; Youden’s index 0.525; cutoff value 0.833; sensitivity and specificity were 0.859 and 0.667, respectively). The AUC of the Insall–Salvati ratio was 0.699 [95% confidence interval (CI) 0.629–0.762; Youden’s index 0.343; cutoff value 1.125; sensitivity and specificity were 0.424 and 0.911, respectively]. The AUC of the SP-ET index was significantly higher than the AUC of Insall–Salvati ratio ( p = 0.027). Discussion The main findings of this present study were twofold. Firstly, our data showed that increased of the SP-ET index was relationship with the risk of developing chondromalacia patella. Secondly, the SP-ET index might be a better indicator to define the vertical position of the patella relative to femoral trochlear than the Insall–Salvati ratio in chondromalacia patella patients. These findings supported our hypothesis and indicated that the SP-ET index may be a useful complement parameter to define the vertical position of the patella relative to the femoral trochlear, and a higher position of patella might play a role in the pathogenesis of chondromalacia patella. The previous researches have analyzed the influence of patellofemoral malalignment on chondromalacia patella or patellar cartilage defects [ 5 , 8 , 10 , 12 , 17 , 23 ]. Duran S et al[ 10 ] suggested that abnormal trochlear morphology was increased the risk of chondromalacia patella in women and, in particular, women with a shallow trochlea and/or flattened lateral trochlea, this conclusion was similar to the result of Tuna BK et al[ 5 ]. In addition, the study of Tuna BK et al also found that patellar tilt was related to the presence of chondromalacia patella. Some studies found that a higher position of patella was an important influencing factor of chondromalacia patella[ 8 , 12 , 17 ], and in addition to the standard measurements of patellar height, some other measurements were analyzed, such as modified Insall-Salvati index[ 12 , 17 , 24 ], patellotrochlear index and patellophyseal index[ 17 , 24 ]. Overall, patellofemoral malalignment and structural abnormalities of the patellofemoral joint leaded to pathologic pressure on the patellofemoral joint might be an important pathogenesis of chondromalacia patella[ 17 , 24 ]. The Insall-Salvati ratio was defined as the length of the patellar tendon divided by the length of the patella, which was a validated and widely used index for evaluating the position of patella[ 20 , 25 ]. The Insall-Salvati ratio can be measured on both lateral radiographs and sagittal MR image of knee. A higher position of patella might result in failure of the patella to engage the trochlear groove early in knee flexion [ 14 ], and decreased the contact area between the patellar articular surface and trochlea[ 7 , 13 ]. Previous studies have shown that patella alta was associated with patellofemoral joint pain, instability, chondromalacia, and osteoarthritis [ 1 , 7 , 26 , 27 ]. In this study, although the Insall–Salvati ratio was significantly higher in the chondromalacia patella group than that in the control group, there were just 24.2% (24/99) of patients in the chondromalacia patella group showed a pathologic Insall–Salvati ratio of >1.2, which coincided with the results of Ambra LF et al[ 8 ]. Moreover, Ali SA et al[ 28 ] found that the Insall-Salvati ratio did not correlate with the severity of patellotrochlear articular cartilage defected. In our opinion, the Insall–Salvati ratio in most patients with chondromalacia patella were in the normal range, which might reduce the instruction of this parameter in practical clinical work. Therefore, it was of great clinical impact to find more effective and direct evaluation indicators. In the present study, the SP-ET index was used to defione the position of the patella relative to the femoral trochlear, and SP-ET index showed a moderate correlation with the Insall–Salvati ratio. Ali SA et al[ 28 ] and Mehl J et al[ 17 ] had used the patellophyseal index to assess patella height in their studies, this parameter was calculated as the distance from the most superior point of the patellar cartilage to the most superior point of the femoral cartilage divided by length of patellar articular cartilage, there were some similarities between the SP-ET index and patellophyseal index. However, the measurement of the SP-ET index only needed to be done at one plain (the sagittal plain with the greatest longitudinal diameter of the patella), and without the effect of axial displacement of patella. Therefore, we thought that the SP-ET index had a good practicability, and the intra and inter-reader reliability of this parameter were also good in our study. Despite Mehl J et al[ 17 ] suggested that no significant difference of the patellophyseal index between the patellar cartilage defect group and control group. But different from the study of Mehl J et al[ 17 ], the study of Ali SA et al [ 28 ] have found that there was statistically significant difference in the patellophyseal index between normal group and severe patellar cartilage defect group. In the present study, we found that the SP-ET index in chondromalacia patella group was significantly higher than that in control group, and the AUC of the SP-ET index was significantly higher than that of Insall–Salvati ratio. The difference of the results might be related to the different severity of the included participants in these studies, and the strict control of the flexion angle of the knee in our study. Because in our practical measurement process, it was found that the flexion angle of the knee had a great impact on the value of the SP-ET index. According to the results of these studies, we thought that the correlation of the SP-ET index and patellophyseal index with the occurrence and severity of chondromalacia patella/ patellar cartilage defect required prospective and biomechanical studies to explore this further. Our study has several limitations. First, this was a retrospective study, and the selection of participants in the chondromalacia patella group were based on MR images without histologic or pathologic evidence. Second, because of the measurement errors might be caused by the formation of patella spurs, only patients with grade 1-2B chondromalacia patella (based on the modified Noyes classification system) were included in the patient group, therefore, patients with severe chondromalacia patella were excluded in this study. Third, the flexion angle of the knee has a great influence on the SP-ET index, so the measurement of the SP-ET index needs to strictly control the flexion angle of the knee. In addition, there were no strict age and gender matching between the two groups of participants. Future research efforts should focus on the relationship between the SP-ET index and patellofemoral osteoarthritis using a prospective longitudinal study, and the role of the SP-ET index in different grades of chondromalacia patella. Conclusions The SP-ET index can be easily measured to define the vertical position of the patella relative to the femoral trochlear, and it showed a moderate correlation with the Insall–Salvati ratio which was a conventional measurement of patellar height. ROC analysis showed the diagnostic efficiency of the SP-ET index was better than the Insall–Salvati ratio in patients with chondromalacia patella. Therefore, the SP-ET index showed promise as a useful complement parameter to define the vertical position of the patella, and a higher position of patella might be one of the factors of developing chondromalacia patella. Abbreviations AUC Area under the curve CI Confidence interval ICCs Intraclass correlation coefficients MRI Magnetic resonance imaging PL Patellar diagonal length PT Patellar tendon length SP-ET Most superior point of patella - entrance of femoral trochlea distance ROC Receiver operating characteristic Declarations Ethics approval and consent to participate: Institutional Review Board approval was obtained by The First Affiliated Hospital of Chongqing Medical University. (No. 2021-203). Consent for publication: Not applicable (Written informed consent for this retrospective analysis was waived). Availability of data and materials: The data used and analysed during the current study are available from the corresponding author on reasonable request. Competing interests: The authors declare that they have no competing interests. Funding: No funding was received for this study. Authors' contributions: Wei Huang Conceptualized the study, Carried out the statistical analysis, reviewed the manuscript, Lead author of original trial data. Jia Li collected and analyzed the data, Wrote the manuscript. Lanyu Qiu Carried out the statistical analysis, reviewed the manuscript. Bo Sheng Collected and analyzed the data. The author(s) read and approved the final manuscript. Jia Li and Lanyu Qiu contribute equally to this work. Acknowledgements: Not applicable. References Askenberger M, Janarv PM, Finnbogason T, Arendt EA. Morphology and anatomic patellar instability risk factors in first time traumatic lateral patellar dislocations: A Prospective Magnetic Resonance Imaging Study in Skeletally Immature Children. Am J Sports Med. 2017;45(1):50–8. Grantham WJ, Aman ZS, Brady AW, Rosenberg SI, Lee Turnbull T, Storaci HW, Dornan GJ, LaPrade RF. 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Tables Table 1 Descriptive data chondromalacia patella group (n=99) control group (n=99) Age 43 ± 7 33 ± 8 Gender (n, %) male 32(41.6%) 62(64.6%) female 45(58.4%) 34(35.4%) Side (n, %) right 30(39.0%) 42(43.8%) left 25(32.5%) 51(53.1%) bilateral 22(28.5%) 3 (3.1%) Patellar alta (n, %) 24(24.2%) — Table 2 The intra- and inter-observer agreement between two radiologists of quantitative MRI measurements Quantitative parameters Intra-observer Inter-observer ICCs (95%CI) f value p value ICCs (95%CI) f value p value SP-ET index 0.930 (0.863-0.964) 14.088 <0.001 0.890 (0.799-0.945) 8.855 <0.001 Insall-Salvati ratio 0.875 (0.754-0.936) 7.846 <0.001 0.973 (0.943-0.987) 38.141 <0.001 SP-ET index : the most superior point of patella - entrance of femoral trochlea distance ratio. ICCs : intraclass correlation coefficients. CI : confidence interval. Table 3 Comparison of MR quantitative parameters between the chondromalacia patella group and control groups SP-ET index Insall-Salvati ratio chondromalacia patella group 0.933±0.115 1.100±0.145 control group 0.802±0.108 1.004±0.086 t value 8.227 5.709 P value <0.001 0.833(se= 0.859, sp=0.667) Insall-Salvati ratio 0.699(0.629-0.762) >1.125 (se=0.424, sp=0.911) z value 2.216 — p value 0.027 — ROC : receiver operating characteristic. Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-957545","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research article","associatedPublications":[],"authors":[{"id":56190232,"identity":"90aa35a0-176d-4b7a-8f71-3803a08f167f","order_by":0,"name":"Jia Li","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Jia","middleName":"","lastName":"Li","suffix":""},{"id":56190233,"identity":"dc5770f1-f7e6-4e0d-8ee7-68ef6816828e","order_by":1,"name":"Lanyu Qiu","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Lanyu","middleName":"","lastName":"Qiu","suffix":""},{"id":56190234,"identity":"6d25ab7c-430c-457e-a170-c2bbc23ebf51","order_by":2,"name":"Bo Sheng","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Sheng","suffix":""},{"id":56190235,"identity":"1d8e8223-6478-4f49-bd0d-75316846464d","order_by":3,"name":"Fan Yu","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Fan","middleName":"","lastName":"Yu","suffix":""},{"id":56190236,"identity":"fdc272cc-a822-4ae8-aa76-14b6f34229bc","order_by":4,"name":"Haitao Yang","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Haitao","middleName":"","lastName":"Yang","suffix":""},{"id":56190237,"identity":"c23a18bf-8739-4e58-9430-abe098f93828","order_by":5,"name":"Furong Lv","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Furong","middleName":"","lastName":"Lv","suffix":""},{"id":56190238,"identity":"d3b5f864-27df-477f-a8de-64187e666b1d","order_by":6,"name":"Fajin Lv","email":"","orcid":"","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Fajin","middleName":"","lastName":"Lv","suffix":""},{"id":56190239,"identity":"67fb39ea-ffe7-4e58-a663-4befce89641e","order_by":7,"name":"Wei Huang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3klEQVRIiWNgGAWjYBACAyjNw8/efPDBhx+kaJHsOZZsOLMHyGQjUguDwYwcM2kONiK0mEskP3v4tc1GxoDnzAdpBh6GPH75BvxaLGekmRvLtqXxmLP3bjAusGAolmwj5LAbCWbSktsO81j2nN2QPIOHIXHDMYJa0r8BtfznMbiR8+AwDxtD4n7CWnLMJD9uOwDSwtgM0rKBYIideVMmzfgvGRTIxowzeyQSZxxLIKDlePo2yR9n7OyBUfn8x4cfNon9zQcIWAMEzDwItgRh5SDASEwyGQWjYBSMghEMAPemRalxEzQNAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-9116-2985","institution":"The First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":true,"prefix":"","firstName":"Wei","middleName":"","lastName":"Huang","suffix":""}],"badges":[],"createdAt":"2021-10-06 10:44:37","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-957545/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-957545/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":14491159,"identity":"72ae0f05-f534-4a2f-bf10-aa8be49dac45","added_by":"auto","created_at":"2021-10-13 14:59:48","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":192494,"visible":true,"origin":"","legend":"Flowchart for selection of participants in chondromalacia patella group","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/044556402936b0093a61de61.jpeg"},{"id":14491160,"identity":"7251262c-623d-43d1-a5a9-8df3db821985","added_by":"auto","created_at":"2021-10-13 14:59:48","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":792079,"visible":true,"origin":"","legend":"The modified Noyes classification system of patellar chondral lesions.\n(a): grade 1 - increased T2 signal intensity of morphologically normal cartilage;\n(b): grade 2A - superficial partial-thickness cartilage defect less than 50% of total articular surface thickness;\n(c): grade 2B - deep partial-thickness cartilage defect greater than 50% of the total articular surface thickness;\n(d): grade 3 - full thickness cartilage defect.","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/5080d7d3f74857db8acd6cae.jpeg"},{"id":14491162,"identity":"65d24830-b2ca-4306-8e1e-bf3438bd2b3c","added_by":"auto","created_at":"2021-10-13 14:59:48","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":615065,"visible":true,"origin":"","legend":"Methods for determining the Insall-Salvati ratio (a) and SP-ET index (b), demonstration of measurements of the related parameters on sagittal MR images.\n(a): The Insall-Salvati ratio was calculated as the patellar tendon length (PT) divided by the maximum patellar diagonal length (PL);\n(b): The SP-ET index was calculated as the distance between the most superior point of patella and the entrance of femoral trochlea (β) divided by the patellar articular surface length (α). Line γ was the reference line of the entrance plane of femoral trochlea;\n(c): The entrance plane of femoral trochlea, it was the first craniocaudal plane where the complete cartilaginous trochlea can be seen.","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/17d2f7944ba827855b54f0f5.jpeg"},{"id":14491161,"identity":"45abbdbf-4349-49de-a27c-a9628c718ca8","added_by":"auto","created_at":"2021-10-13 14:59:48","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":61281,"visible":true,"origin":"","legend":"The receiver operating characteristic (ROC) curves of SP-ET index and Insall–Salvati ratio. The ROC of SP-ET index was the blue curve (area under curve (AUC) = 0.803), the ROC of Insall–Salvati ratio was the red curve (AUC = 0.699).","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/969cbb419a0277a96ee3d72b.jpeg"},{"id":14491164,"identity":"cdccb5ec-15e1-4f81-9b59-fce5789b384b","added_by":"auto","created_at":"2021-10-13 14:59:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":754143,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/2cd6ac52-ec1b-4110-8953-a0b3b8a11a15.pdf"},{"id":14491163,"identity":"dbf401fe-8702-4b89-b6be-2641eefee8fa","added_by":"auto","created_at":"2021-10-13 14:59:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":754143,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-957545/v1/6f9c2418-5c56-45b7-9a29-222327fdeb27.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eThe SP-ET Index is a New Index for Assessing The Vertical Position of Patella\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eThe primary anatomical factors which were associated with patellofemoral malalignment included: patella alta, trochlear dysplasia, and abnormal lateral patellar tilt [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Patellofemoral malalignment resulted in abnormal joint contact and chondral stresses within the patellofemoral compartment, and often associated with chondral damage and chronic anterior knee pain [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Chondromalacia patella is characterized by softening, swelling, fissuring or fraying of the patellar cartilage and can lead to a decrease in quality of life, it is one of common causes of chronic anterior knee pain [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A progressive loss of articular cartilage can lead to the development of patellofemoral osteoarthritis[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The most commonly cited hypothesis is patellofemoral malalignment and/or maltracking leads to pathological loadings on the patellofemoral joint, and increases subsequent articular cartilage wear[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], and we found that there have been several studies focusing on the relationship between patellofemoral malalignment and chondromalacia patella.\u003c/p\u003e \u003cp\u003eDuran S et al[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and Tuna BK et al[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] were reported that there was an association between abnormal trochlear morphology and chondromalacia patella in women. In addition, the study of Tabary M et al showed that the patellar height might be an important factor in the severity of chondromalacia patella[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In the study by Deniz \u0026Ouml;zel, both patella alta and patella baja were found to be related to chondromalacia patella, and the modified Insall-Salvati index ratio was the best indicator to define patella alta[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Patella alta may cause excessive lateral motion of the patella during knee flexion[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and cause the patella may not be able to engage the trochlear groove early in knee flexion[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], all of these could the development of chondromalacia patella. Multiple methods of assessing the vertical position of the patella on imaging have been described in previous literature[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Most noteworthy, some studies suggested that the ratio between the articular cartilage of the patella and the trochlear cartilage (parameters Patellotrochlear index[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] and Patellar Articular Overlap[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]) could be better used to assess the vertical position of the patella in patients with patellofemoral instability.\u003c/p\u003e \u003cp\u003eIn addition, there were some researches focusing on the role of trochlear dysplasia in chondromalacia patella or patellofemoral cartilage lesions[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and the study of Ambra LF et al[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] suggested that trochlear dysplasia might be more important than the patellar malposition in the pathogenesis of patellofemoral cartilage lesions. But the measurement parameters defining the vertical position of the patella in some studies did not better reflect the vertical position of the patella relative to the femoral trochlear as Patellotrochlear index[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] and Patellar Articular Overlap[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] do. Therefore, the present study aimed to identify the ratio of the most superior point of patella-entrance of femoral trochlea distance to the length of the patella articular surface on sagittal MRI as a newer index which can define the vertical position of patella relative to the trochlea, and investigate the effect of this parameter on chondromalacia patella. We hypothesized that the new parameter was a good indicator to define the vertical position of the patella, moreover, increased of this parameter might be a potential risk factor for developing chondromalacia patella.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis retrospective study was approved by the Committee for Human Research of our institution (No. 2021-203). We retrospectively reviewed patients who were diagnosed with the modified Noyes classification system grade 1-2B chondromalacia patella based on MRI between January 2020 to April 2021 using picture archiving and communication systems at our department. Inclusion criteria were as follows: (1) patients with typical clinical presentation and MR signs with chondromalacia patella; (2) the flexion angle of the knee in MR images was 0-10\u0026deg;. Exclusion criteria were as follows: (1) participants with a history of traumatism or surgery of the knee; (2) presence of patellar dislocation, meniscus or ligamentous lesions; (3) presence of severe osteoarthritis (\u0026ge; KL 3 grade) or inflammatory arthritis; and (4) poor MR image quality (Fig. 1). In order to obtain a control group of participants without anterior knee pain and without any detectable alignment abnormalities or structural lesions on MRI and arthroscopy, patients undergoing meniscus rupture repair were chosen. All the clinical information was acquired by reviewing the clinical records or collected by telephone for medical history if uncertain on records.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMRI protocol\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMRI was performed using 1.5-T MRI equipment (Magnetom Essenza; Siemens Healthcare) with an extremity matrix knee coil (a Tim coil). The imaging protocol was as follows: sagittal and coronal T1 turbo spin echo (repetition time/echo time 306/ 12 ms, field of view 16 cm, matrix size 320 \u0026times; 320, slice thickness 4 mm), sagittal T2 turbo spin echo (repetition time/echo time 3220/99 ms, field of view 16 cm, matrix size 320 \u0026times; 320, slice thickness 4 mm), sagittal and coronal intermediate-weighted turbo spin echo with fat saturation (repetition time/echo time 2800/38 ms, field of view 16 cm, matrix size 256 \u0026times; 256, slice thickness 4 mm), and axial intermediate-weighted turbo spin echo with fat saturation (repetition time/echo time 2800/51 ms, field of view 16 cm, matrix size 232 \u0026times; 256, slice thickness 4 mm).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImage analyses\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll MRI images were independently reviewed by two musculoskeletal radiologists (Qiu and Sheng, with 3 and 13 years of clinical experience respectively). The routine MR imaging protocol were used to grade the articular cartilage on the patellofemoral joint according to the modified Noyes classification system: grade 0= normal cartilage, grade 1= increased T2 signal intensity of morphologically normal cartilage, grade 2A = superficial partial-thickness cartilage defect less than 50% of total articular surface thickness, grade 2B = deep partial-thickness cartilage defect greater than 50% of the total articular surface thickness, and grade 3 = full thickness cartilage defect [18, 19] (Fig. 2). The MRI measurements were performed by two other fellowship-trained musculoskeletal radiologists (Li and Yu, with 7 and 18 years of clinical experience respectively) after all the data of the two groups were mixed and blindly and randomly distributed. All measurements were repeated by one of the radiologists (Li), and the interval between the first and second reading was at last 4 weeks.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTwo quantitative parameters for evaluating patellar position were assessed on the images of each MRI examination. The Insall\u0026ndash;Salvati ratio was calculated as the patellar tendon length divided by the maximum patellar diagonal length on sagittal MRI image (Fig. 3a). The Insall\u0026ndash;Salvati ratio was used to reflect the height of the patella, and the threshold was defined as \u0026gt;1.2[20]. The most superior point of patella - entrance of femoral trochlea distance ratio (SP-ET index) was used to reflected the vertical position of the patella relative to the trochlea. The entrance of femoral trochlea was the first craniocaudal plane where the complete cartilaginous trochlea can be seen[21, 22]. The sagittal plain with the greatest longitudinal diameter of the patella was used to obtain the SP-ET index which was calculated as the distance between the most superior point of patella and the entrance of femoral trochlea divided by the patellar articular surface length (Fig. 3b-c).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical tests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, descriptive data were calculated for demographic data. The subjects were categorized, according to the inclusion and exclusion criteria, into the chondromalacia patella group and the control group. Intraclass correlation coefficients (ICCs) were used to assess the intra- and inter-reader reliability of MRI quantitative measures. Continuous variables with a normal distribution were expressed as mean \u0026plusmn; standard deviation, and Student\u0026rsquo;s t test was used to detect the difference. The Spearman correlation was used to analyze the relationship between the two parameters. The above statistical analyses were performed using Windows software SPSS (version 17.0; SPSS, Chicago, IL, USA), and the significance level was set at 0.05. In addition, the diagnostic efficacy of two measurements of the patellar position were determined with receiver operating characteristic (ROC) curve analyses, it was performed using MedCalc statistical software (Med-Calc Software, Mariakerke, Belgium). Optimum cut-off point, sensitivity, specificity, and area under the curve (AUC) of each parameter were calculated, then, comparisons of ROC curves between the two groups, and the significance level was set at 0.05.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003cp\u003e\u003cb\u003eDemographic characteristics of the subjects in the two groups\u003c/b\u003e\u003c/p\u003e \u003cp\u003eDuring the study period, there was a total of 99 knees (25 left, 30 right, and 22 bilateral) of 77 patients (45 males and 32 females, age range 23\u0026ndash;50 years, mean age 43 \u0026plusmn; 7 years) were included in the chondromalacia patella group. There were 99 knees (51 left, 42 right, and 3 bilateral) of 96 participants (62 males and 34 females, age range 17\u0026ndash;45 years, mean age 33 \u0026plusmn; 8 years) in the control group (Table. 1).\u003c/p\u003e \u003c/div\u003e\n\u003cp\u003e\u003cb\u003eIntra- And Inter-observer Reliability Of Quantitative Mri Measurements\u003c/b\u003e\u003c/p\u003e\n\u003cp\u003eThe intra-reader ICCs for the SP-ET index and Insall\u0026ndash;Salvati ratio quantitative measurements were 0.930 and 0.875, respectively. and the inter-reader ICCs for the SP-ET index and Insall\u0026ndash;Salvati ratio were 0.890 and 0.973, respectively, as shown in Table. 2, indicating good intra and inter-reader reliability.\u003c/p\u003e \u003cp\u003e \u003cb\u003eComparison between the chondromalacia patella group and control group and the correlation between the two parameters\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe two measurement parameters showed significant differences between chondromalacia patella group and control group. The Insall\u0026ndash;Salvati ratio and SP-ET index in the chondromalacia patella group were significantly higher than those in the control group (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001) (Table. 3). The SP-ET index showed a moderate positive correlation with the Insall\u0026ndash;Salvati ratio (\u003cem\u003er\u003c/em\u003e=0.307, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.001).\u003c/p\u003e\n\u003cp\u003e\u003cb\u003eRoc Analyses Of Mri Quantitative Measurements\u003c/b\u003e\u003c/p\u003e\n\u003cp\u003eThe ROC curves of the Insall\u0026ndash;Salvati ratio and SP-ET index were generated (Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The area under the curve (AUC) of the SP-ET index was 0.803 (95% CI 0.740\u0026ndash;0.856; Youden\u0026rsquo;s index 0.525; cutoff value 0.833; sensitivity and specificity were 0.859 and 0.667, respectively). The AUC of the Insall\u0026ndash;Salvati ratio was 0.699 [95% confidence interval (CI) 0.629\u0026ndash;0.762; Youden\u0026rsquo;s index 0.343; cutoff value 1.125; sensitivity and specificity were 0.424 and 0.911, respectively]. The AUC of the SP-ET index was significantly higher than the AUC of Insall\u0026ndash;Salvati ratio (\u003cem\u003ep\u003c/em\u003e = 0.027).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe main findings of this present study were twofold. Firstly, our data showed that increased of the SP-ET index was relationship with the risk of developing chondromalacia patella. Secondly, the SP-ET index might be a better indicator to define the vertical position of the patella relative to femoral trochlear than the Insall\u0026ndash;Salvati ratio in chondromalacia patella patients. These findings supported our hypothesis and indicated that the SP-ET index may be a useful complement parameter to define the vertical position of the patella relative to the femoral trochlear, and a higher position of patella might play a role in the pathogenesis of chondromalacia patella.\u003c/p\u003e \u003cp\u003eThe previous researches have analyzed the influence of patellofemoral malalignment on chondromalacia patella or patellar cartilage defects [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Duran S et al[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] suggested that abnormal trochlear morphology was increased the risk of chondromalacia patella in women and, in particular, women with a shallow trochlea and/or flattened lateral trochlea, this conclusion was similar to the result of Tuna BK et al[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In addition, the study of Tuna BK et al also found that patellar tilt was related to the presence of chondromalacia patella. Some studies found that a higher position of patella was an important influencing factor of chondromalacia patella[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and in addition to the standard measurements of patellar height, some other measurements were analyzed, such as modified Insall-Salvati index[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], patellotrochlear index and patellophyseal index[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Overall, patellofemoral malalignment and structural abnormalities of the patellofemoral joint leaded to pathologic pressure on the patellofemoral joint might be an important pathogenesis of chondromalacia patella[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe Insall-Salvati ratio was defined as the length of the patellar tendon divided by the length of the patella, which was a validated and widely used index for evaluating the position of patella[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The Insall-Salvati ratio can be measured on both lateral radiographs and sagittal MR image of knee. A higher position of patella might result in failure of the patella to engage the trochlear groove early in knee flexion [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and decreased the contact area between the patellar articular surface and trochlea[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Previous studies have shown that patella alta was associated with patellofemoral joint pain, instability, chondromalacia, and osteoarthritis [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. In this study, although the Insall\u0026ndash;Salvati ratio was significantly higher in the chondromalacia patella group than that in the control group, there were just 24.2% (24/99) of patients in the chondromalacia patella group showed a pathologic Insall\u0026ndash;Salvati ratio of \u0026gt;1.2, which coincided with the results of Ambra LF et al[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Moreover, Ali SA et al[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] found that the Insall-Salvati ratio did not correlate with the severity of patellotrochlear articular cartilage defected. In our opinion, the Insall\u0026ndash;Salvati ratio in most patients with chondromalacia patella were in the normal range, which might reduce the instruction of this parameter in practical clinical work. Therefore, it was of great clinical impact to find more effective and direct evaluation indicators.\u003c/p\u003e \u003cp\u003eIn the present study, the SP-ET index was used to defione the position of the patella relative to the femoral trochlear, and SP-ET index showed a moderate correlation with the Insall\u0026ndash;Salvati ratio. Ali SA et al[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] and Mehl J et al[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] had used the patellophyseal index to assess patella height in their studies, this parameter was calculated as the distance from the most superior point of the patellar cartilage to the most superior point of the femoral cartilage divided by length of patellar articular cartilage, there were some similarities between the SP-ET index and patellophyseal index. However, the measurement of the SP-ET index only needed to be done at one plain (the sagittal plain with the greatest longitudinal diameter of the patella), and without the effect of axial displacement of patella. Therefore, we thought that the SP-ET index had a good practicability, and the intra and inter-reader reliability of this parameter were also good in our study.\u003c/p\u003e \u003cp\u003eDespite Mehl J et al[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] suggested that no significant difference of the patellophyseal index between the patellar cartilage defect group and control group. But different from the study of Mehl J et al[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], the study of Ali SA et al [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] have found that there was statistically significant difference in the patellophyseal index between normal group and severe patellar cartilage defect group. In the present study, we found that the SP-ET index in chondromalacia patella group was significantly higher than that in control group, and the AUC of the SP-ET index was significantly higher than that of Insall\u0026ndash;Salvati ratio. The difference of the results might be related to the different severity of the included participants in these studies, and the strict control of the flexion angle of the knee in our study. Because in our practical measurement process, it was found that the flexion angle of the knee had a great impact on the value of the SP-ET index. According to the results of these studies, we thought that the correlation of the SP-ET index and patellophyseal index with the occurrence and severity of chondromalacia patella/ patellar cartilage defect required prospective and biomechanical studies to explore this further.\u003c/p\u003e \u003cp\u003eOur study has several limitations. First, this was a retrospective study, and the selection of participants in the chondromalacia patella group were based on MR images without histologic or pathologic evidence. Second, because of the measurement errors might be caused by the formation of patella spurs, only patients with grade 1-2B chondromalacia patella (based on the modified Noyes classification system) were included in the patient group, therefore, patients with severe chondromalacia patella were excluded in this study. Third, the flexion angle of the knee has a great influence on the SP-ET index, so the measurement of the SP-ET index needs to strictly control the flexion angle of the knee. In addition, there were no strict age and gender matching between the two groups of participants. Future research efforts should focus on the relationship between the SP-ET index and patellofemoral osteoarthritis using a prospective longitudinal study, and the role of the SP-ET index in different grades of chondromalacia patella.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe SP-ET index can be easily measured to define the vertical position of the patella relative to the femoral trochlear, and it showed a moderate correlation with the Insall\u0026ndash;Salvati ratio which was a conventional measurement of patellar height. ROC analysis showed the diagnostic efficiency of the SP-ET index was better than the Insall\u0026ndash;Salvati ratio in patients with chondromalacia patella. Therefore, the SP-ET index showed promise as a useful complement parameter to define the vertical position of the patella, and a higher position of patella might be one of the factors of developing chondromalacia patella.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAUC \u0026nbsp; \u0026nbsp; \u0026nbsp;Area under the curve\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCI \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Confidence interval\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eICCs \u0026nbsp; \u0026nbsp; \u0026nbsp;Intraclass correlation coefficients\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMRI \u0026nbsp; \u0026nbsp; \u0026nbsp; Magnetic resonance imaging\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePL \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Patellar diagonal length\u003c/p\u003e\n\u003cp\u003ePT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Patellar tendon length\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSP-ET \u0026nbsp; \u0026nbsp; Most superior point of patella - entrance of femoral trochlea distance\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eROC \u0026nbsp; \u0026nbsp; \u0026nbsp;Receiver operating characteristic\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u0026nbsp;\u003c/strong\u003eInstitutional Review Board approval was obtained by The First Affiliated Hospital of Chongqing Medical University. (No. 2021-203).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable (Written informed consent for this retrospective analysis was waived).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u0026nbsp;\u003c/strong\u003eThe data used and analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eNo funding was received for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions:\u0026nbsp;\u003c/strong\u003eWei Huang Conceptualized the study, Carried out the statistical analysis, reviewed the manuscript, Lead author of original trial data. Jia Li collected and analyzed the data, Wrote the manuscript. Lanyu Qiu Carried out the statistical analysis, reviewed the manuscript. Bo Sheng Collected and analyzed the data. The author(s) read and approved the final manuscript. Jia Li and Lanyu Qiu contribute equally to this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAskenberger M, Janarv PM, Finnbogason T, Arendt EA. Morphology and anatomic patellar instability risk factors in first time traumatic lateral patellar dislocations: A Prospective Magnetic Resonance Imaging Study in Skeletally Immature Children. Am J Sports Med. 2017;45(1):50\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrantham WJ, Aman ZS, Brady AW, Rosenberg SI, Lee Turnbull T, Storaci HW, Dornan GJ, LaPrade RF. 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AJR Am J Roentgenol. 2009;193(5):1361\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cdiv class=\"gridtable\"\u003e\n \u003ctable border=\"1\" id=\"Tab1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDescriptive data\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003echondromalacia patella group (n=99)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003econtrol group (n=99)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e43 \u0026plusmn; 7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33 \u0026plusmn; 8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGender (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32(41.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e62(64.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003efemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e45(58.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34(35.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSide (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eright\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30(39.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e42(43.8%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eleft\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25(32.5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e51(53.1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ebilateral\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22(28.5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3 (3.1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePatellar alta (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24(24.2%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e The intra- and inter-observer agreement between two radiologists of quantitative MRI measurements\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 12.4382%;\" valign=\"top\" width=\"17.747440273037544%\"\u003e\n \u003cp\u003eQuantitative parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width: 32.5088%;\" valign=\"top\" width=\"38.737201365187715%\"\u003e\n \u003cp\u003eIntra-observer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width: 25.9128%;\" valign=\"top\" width=\"40.27303754266212%\"\u003e\n \u003cp\u003eInter-observer\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 14.6054%;\" valign=\"top\" width=\"21.369294605809127%\"\u003e\n \u003cp\u003eICCs (95%CI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.3863%;\" valign=\"top\" width=\"12.033195020746888%\"\u003e\n \u003cp\u003e\u003cem\u003ef\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.5171%;\" valign=\"top\" width=\"13.692946058091286%\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.6996%;\" valign=\"top\" width=\"21.57676348547718%\"\u003e\n \u003cp\u003eICCs (95%CI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6.7845%;\" valign=\"top\" width=\"13.692946058091286%\"\u003e\n \u003cp\u003e\u003cem\u003ef\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 4.3345%;\" valign=\"top\" width=\"13.692946058091286%\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12.4382%;\" valign=\"top\" width=\"17.747440273037544%\"\u003e\n \u003cp\u003eSP-ET index\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.6054%;\" valign=\"top\" width=\"17.576791808873722%\"\u003e\n \u003cp\u003e0.930 (0.863-0.964)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.3863%;\" valign=\"top\" width=\"9.897610921501707%\"\u003e\n \u003cp\u003e14.088\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.5171%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.6996%;\" valign=\"top\" width=\"17.747440273037544%\"\u003e\n \u003cp\u003e0.890 (0.799-0.945)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6.7845%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e8.855\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 4.3345%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12.4382%;\" valign=\"top\" width=\"17.747440273037544%\"\u003e\n \u003cp\u003eInsall-Salvati ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.6054%;\" valign=\"top\" width=\"17.576791808873722%\"\u003e\n \u003cp\u003e0.875 (0.754-0.936)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.3863%;\" valign=\"top\" width=\"9.897610921501707%\"\u003e\n \u003cp\u003e7.846\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.5171%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.6996%;\" valign=\"top\" width=\"17.747440273037544%\"\u003e\n \u003cp\u003e0.973 (0.943-0.987)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6.7845%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e38.141\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 4.3345%;\" valign=\"top\" width=\"11.262798634812286%\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003eSP-ET index\u003c/em\u003e:\u0026nbsp;the most superior point of patella - entrance of femoral trochlea distance ratio.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eICCs\u003c/em\u003e:\u0026nbsp;intraclass correlation coefficients.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCI\u003c/em\u003e: confidence interval.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003ctable border=\"1\" id=\"Tab2\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison of MR quantitative parameters between the chondromalacia patella group and control groups\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSP-ET index\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eInsall-Salvati ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003echondromalacia patella group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.933\u0026plusmn;0.115\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.100\u0026plusmn;0.145\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003econtrol group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.802\u0026plusmn;0.108\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.004\u0026plusmn;0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003et\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.227\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.709\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable border=\"1\" id=\"Tab3\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThe results of ROC analysis of the SP-ET index and Insall-Salvati ratio\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAUC (95%CI)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbnormal MRI cutoff value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSP-ET index\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.803(0.740-0.856)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;0.833(se= 0.859, sp=0.667)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eInsall-Salvati ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.699(0.629-0.762)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;1.125 (se=0.424, sp=0.911)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ez\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.027\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cem\u003eROC\u003c/em\u003e: receiver operating characteristic.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Chondromalacia patella, the SP-ET index, The Insall–Salvati ratio, Patellofemoral joint, vertical position","lastPublishedDoi":"10.21203/rs.3.rs-957545/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-957545/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground.\u003c/h2\u003e \u003cp\u003eThere were some parameters in previous studies did not better reflect the vertical position of the patella relative to the femoral trochlear. The purposes of this study were to assess the value of the most superior point of patella - entrance of femoral trochlea distance ratio (SP-ET index) as a newer index in defining the vertical position of patella relative to the trochlea, correlate it with the Insall-Salvati ratio, and investigate the effect of the new index on chondromalacia patella.\u003c/p\u003e\u003ch2\u003eMethods.\u003c/h2\u003e \u003cp\u003eA total of 99 knees of 77 patients with chondromalacia patella were retrospectively analyzed using magnetic resonance imaging (MRI) data from our database. The Insall\u0026ndash;Salvati ratio and SP-ET index were measured on MR images. There were 99 knees just with meniscus rupture were enrolled as the control group. The two parameters of the chondromalacia patella were compared with those of the control group.\u003c/p\u003e\u003ch2\u003eResults.\u003c/h2\u003e \u003cp\u003eThe Insall\u0026ndash;Salvati ratio and SP-ET index in the chondromalacia patella group were significantly higher than those in the control group (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). The SP-ET index showed a moderate positive correlation with the Insall\u0026ndash;Salvati ratio (\u003cem\u003er\u003c/em\u003e=0.307, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.001). Receiver operating characteristic (ROC) analysis showed the diagnostic efficiency of the SP-ET index was better than that of the Insall\u0026ndash;Salvati ratio in patients with chondromalacia patella.\u003c/p\u003e\u003ch2\u003eConclusion.\u003c/h2\u003e \u003cp\u003eThe SP-ET index may be a useful complement parameter to define the vertical position of the patella relative to the femoral trochlear. Increased of the SP-ET index may be an important risk factor for chondromalacia patella.\u003c/p\u003e","manuscriptTitle":"The SP-ET Index is a New Index for Assessing The Vertical Position of Patella","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-10-13 14:59:46","doi":"10.21203/rs.3.rs-957545/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7a35961f-9f23-4010-ac0a-fed7bce41f2d","owner":[],"postedDate":"October 13th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":7818594,"name":"Orthopedics"},{"id":7818595,"name":"Orthopedic Surgery"}],"tags":[],"updatedAt":"2021-10-13T14:59:47+00:00","versionOfRecord":[],"versionCreatedAt":"2021-10-13 14:59:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-957545","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-957545","identity":"rs-957545","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}