Ultrasound and radiographic outcomes of the Coxaflex brace in the treatment of developmental dysplasia of the hip (DDH): a multicentre prospective study

Ultrasound and radiographic outcomes of the Coxaflex brace in the treatment of developmental dysplasia of the hip (DDH): a multicentre prospective study | 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 Ultrasound and radiographic outcomes of the Coxaflex brace in the treatment of developmental dysplasia of the hip (DDH): a multicentre prospective study Maria Rizzo, Michela Saracco, Clara De Negri, Valerio Verdoliva, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9271883/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 Purpose Early diagnosis is essential for the treatment of developmental dysplasia of the hip (DDH), and the use of abduction bracing is considered the gold standard for patients < 6 months of age. The aim of this study is to report an analysis of the results of using the coxaflex abduction brace. Methods Data from 44 DDH were prospectively analysed in two different paediatric orthopaedic units. The diagnosis was made clinically and by ultrasound during the outpatient screening visit. All patients underwent follow-up ultrasound examinations. Radiographic examinations were requested at the end of treatment to assess the acetabular index (AI) and the radiographic position of the proximal femoral growth plate. Results The mean age at the start of treatment was 46 days (range, 4–150 days). The first follow-up (T1) was performed at 42 ± 13 days of treatment, a second follow-up (T2) at 91 ± 21 days, and a third follow-up (T3) at 134 ± 22 days. Ultrasound examinations were performed at each follow-up, which revealed a mean α angle of 47°±4° at the start of treatment. At the T1 follow-up, the mean α angle was 57°±7°, while on T2 and T3 they measured 63°±5° and 64°±5°, respectively. The angular increase on T1 and T2 was statistically significant (p < 0.001). The X-ray examination was performed at an average of 162 ± 40 days and showed an AI of 23°±5° (range 14°-38°). Conclusions The Coxaflex brace is easy to wear and is well tolerated by the newborn, factors that contribute to achieving therapeutic success, along with early diagnosis. developmental dysplasia of the hip Coxaflex brace dynamic brace Infant hip instability Figures Figure 1 Figure 2 Introduction Developmental dysplasia of the hip (DDH) is a congenital disorder of the hip joint that ranges from mild acetabular dysplasia to complete hip dislocation. It is one of the most common orthopaedic conditions in newborns, with an incidence varying based on factors such as gender, family history, and breech presentation.( 1 ) Early detection and timely treatment are crucial to ensuring proper hip development, preventing long-term complications such as joint instability, gait abnormalities, and early-onset osteoarthritis. Currently, a screening program is implemented to facilitate the early diagnosis of DDH. A significant reduction in the rate of surgery for DDH later in life was shown after the introduction of universal ultrasound screening.( 2 ) Although clinical examination plays a crucial role in the diagnostic process, studies indicate that up to 54% of dislocations have no clinical signs including no Ortolani sign and no risk factors.( 3 ) Nowadays, ultrasound is considered the gold standard in the diagnostic process, this is mainly because the US examination of newborns’ hips allows a morphological study of both the bone and the cartilage components and also permits a dynamic evaluation of hip instability, so a dysplasia can be identified in vivo, immediately in the peri-natal period minimizing exposure to X-ray radiation.( 4 ) The Graf classification is the most widely used system, based on the measurement of the alpha and beta angles, and categorizes dysplastic hips into four main types according to these angular values. ( 5 ) The management of DDH depends on the patient's age and the severity of the condition. Among the most employed therapeutic options are dynamic and static splints, which are selected based on the reducibility of the hip and the developmental stage of the child.( 6 ) Static splints are designed to achieve a "rigid reduction" by immobilizing the hips in a fixed position of abduction and flexion, without allowing active joint motion. These devices are typically composed of rigid materials. Evidence suggests that static splints are associated with a higher incidence of complications, particularly avascular necrosis (AVN), when compared to dynamic orthoses. ( 7 )The most widely accepted indication is in children older than 6 to 9 months of age, who require prolonged positioning in abduction due to persistent acetabular dysplasia and/or subluxation. ( 8 ) A dynamic splint facilitates a “dynamic reduction,” allowing controlled movement of the lower limbs while maintaining the hips in a position of flexion and abduction. The most widely accepted indication is the presence of hip instability that can be centred through concentric reduction in under 6 months infants. Among the dynamic splints employed in the treatment of DDH, the Pavlik harness is the most extensively studied and commonly used brace.( 9 ) However, alternative devices, such as the Coxaflex brace, have been developed to provide effective treatment while potentially addressing limitations associated with other bracing methods. The Coxaflex brace aims to achieve a stable reduction while allowing controlled movement. This position allows for the concentric reduction of the femoral head within the acetabulum, facilitating remodelling. 6 Despite its use in clinical practice, data on its effectiveness remain limited compared to the Pavlik harness. The aim of this study is understanding the impact of the Coxaflex brace as a conservative therapeutic option on hip development, as well as its potential advantages and limitations, to optimize treatment strategies for DDH.( 10 ) The authors analysed the ultrasound (US) and radiographic outcomes of the Coxaflex brace in a cohort of infants with DDH. By assessing US parameters such as the evolution of the α angle, acetabular index (AI), and overall hip stability over the treatment period. The findings may contribute to refining current treatment protocols and guiding clinical decision-making in paediatric orthopaedics. Materials and Methods Data from patients evaluated for DDH from June 2022 to May 2025 was prospectively gathered and retrospectively reviewed. Parents of each patient enrolled expressed written informed consent to participate. The study inclusion criteria were patients less than 6 months of age diagnosed with a reduced but displaceable (Barlow+), unilateral or bilateral. ( 11 ) Exclusion criteria were infants greater than 6 months of age at the time of diagnosis, those with less than 6 months of follow-up to assess outcome, presence of a fixed or teratologic dislocation or arthrogryposis, or those with stable ultrasonic hip dysplasia. Infants unable to wear the brace due to femoral nerve palsy within the first 2 weeks of initiating treatment and those not compliant were also excluded. All patients were evaluated clinically by neonatologists at birth and then by experienced pediatric orthopedists. Both children with positive tests and risk factors at birth and children without risk factors who underwent ultrasound screening were enrolled. They were subsequently reevaluated clinically and by ultrasound every 45 days during treatment until resolution. The ultrasound analysis included measurement of the Graf alpha and beta angles and the age of appearance of the femoral head growth nucleus in days. Ultrasound examinations, performed according to the Graf method using a linear transducer (7.5 MHz), provided an accurate in vivo analysis for the diagnosis of DDH. All hips were examined sonographically. ( 5 ) All enrolled children underwent anteroposterior pelvic x-rays to assess the acetabular index upon removal of the brace. Residual dysplasia was defined as acetabular index greater than two standard deviations above the value expected for the age, as defined by Tonnis and subsequent revisions. ( 12 ) The treatment was based on the use of the Coxaflex harness, classified as a dynamic brace but with greater rigidity compared to other dynamic harnesses. Coxaflex is a medical hip abduction orthosis (splint) designed to treat hip issues such as DDH or to keep the hip joint centred and stable after it has been reduced in position. Coxaflex holds the baby’s hips in a controlled flexion and abduction position which is considered a physiologically safe posture that promotes correct hip socket development. The device includes adjustable bars and straps that let clinicians set the amount of flexion (bending) and abduction (outward angle) to suit the child’s condition. Its design allows natural restful muscle positions while preventing extreme positions that could impair blood flow or cause discomfort. The Coxaflex brace allows for hip flexion in a range of 90° to 100° and abduction between 45° and 50°. The brace must be worn 23 hours a day for a minimum period of 16 weeks or until ultrasound resolution. The following demographic data were collected: sex, laterality, age (days), family history, associated malformations, positive test results, Graf classification at the first ultrasound evaluation and trend of alpha and beta values ​​at all subsequent check-ups, acetabular index on x-rays and age of appearance of the ossification nucleus. Ultrasound values ​​of the alpha and beta angles were compared at T0 (enrollment), T1 (45 days from T0) and T2 (90 days from T0). In cases where alpha had not exceeded 60 degrees at T2, a further check was scheduled at T3 (a further 45 days from T2). Before removal of the brace, all children underwent x-ray. In patients who showed no ultrasound or radiographic evidence of ossification of the proximal femur at the time of brace removal, an ultrasound scan was performed after 3 months. In patients who showed ultrasound normalization of the hip but an AI > 90th percentile, the brace was not removed and they continued to wear the brace with further ultrasound monitoring. In these patients, an X-ray was finally performed at one year to reevaluate AI. Ultrasound was performed by two independent experienced pediatric orthopedists and acetabular indices were measured by two independent observers. Clinical, ultrasound and radiographic success was defined as obtaining a stable hip on physical examination and normalization ultrasound hip ultrasound without need to perform a closed or open reduction or to use a rigid abduction orthosis prior to achieving clinical stability. Complications were recorded. Complications include failure of reduction, femoral nerve palsy and residual acetabular dysplasia. Statistical analysis Statistical analysis was performed using SPSS (IBM Statistics). Data was collected using Excel (Microsoft). To incorporate the data of the participants into data analysis regardless of the protocol adherence, all the analyses were performed in accordance with the intention to-treat principle. Appropriate sample size calculation and power analysis were assessed during the planning of the clinical study. Paired t-test or Wilcoxon signed rank test was applied to assess changes after the proposed treatment. Data were expressed as frequencies and percentages for categorical variables and mean and standard deviation (M ± SD) for continuous variables. Intra-class correlation coefficients were used as a measure of concordance in radiographic evaluations between observers. A confidence level of 95% was selected and a p -value < 0.05 chosen as significance threshold. Univariate and multivariate logistic regression analysis was performed to identify predictors of the presence of the proximal femoral ossification nucleus at the end of brace treatment. Age at diagnosis, alpha angle at T0, Beta angle at T0 and treatment duration were tested as possible predictors. Linear regression analysis was carried out to assess possible predictors of the AI at diagnosis, alpha angle at T0, Beta angle at T0 and treatment duration were tested as possible outcome predictors. A two-sided p-value < 0.05 was considered statistically significant, with a confidence level set at 95%. Results A total of 44 hips were evaluated, including 22 unilateral and 11 bilateral cases, comprising 18 right and 26 left hips. The study population included 28 females and 5 males. ( Fig. 1 –clinical case) Detailed demographic data are reported in the Supplementary Material . The median age at diagnosis (T0) was 46 ± 40 days (range, 4–150 days) and the average age at the end of treatment was 224 ± 54 days. The mean alpha angle at T0 was 47 ± 4°, and the mean beta angle was 62 ± 13°. Nineteen hips demonstrated a positive Ortolani manoeuvre. Hip types according to the classification system are summarized in Table 1 . The concordance in radiographic evaluations between observers for ultrasound and radiographic assessments was greater than 80%. Ultrasound follow-up assessments were performed at T1, with a mean interval of 42 ± 13 days; at T2, with a mean interval of 91 ± 21 days; and at T3, where 33 hips were evaluated, with a mean interval of 132 ± 22 days. At T1, the mean alpha and beta angles were 57 ± 7° and 54 ± 6°, respectively, showing a statistically significant difference compared with the time of diagnosis (p < 0.001). At the second follow-up (T2), the mean alpha and beta angles were 63 ± 5° and 53 ± 6°, respectively. The alpha angle demonstrated a statistically significant increase (p < 0.001), whereas the beta angle did not show a statistically significant reduction on paired t-test analysis (p = 0.165). (Fig. 2 – angles graph) At the ultrasound evaluation performed at T3, the mean alpha angle was 64 ± 5°, and the mean beta angle was 51 ± 7°, with no statistically significant differences compared with the previous follow-up (p = 0.317 and p = 0.017, respectively), as shown in Table 2 . All ultrasound examinations were performed by paediatric orthopaedic surgeons with expertise in hip ultrasonography. A standard anteroposterior pelvic radiograph was obtained prior to brace discontinuation, at a mean follow-up of 162 ± 40 days. At the time of imaging, patients had a mean age of 208 ± 57 days. This evaluation allowed assessment of the acetabular index (AI) and comparison with age- and sex-specific percentiles. The mean AI was 23 ± 5° (range 14°-38°), consistent with values reported in the literature. At the end of brace treatment, 30 hips (68%) showed ultrasonographic evidence of the proximal femoral ossification nucleus, with a mean age of 164 ± 45 days. However, hips without ultrasonographic or radiographic evidence of the proximal femoral ossification nucleus at the time of brace discontinuation, underwent additional follow-up evaluations, including ultrasound at 3 and 6 months after brace removal and radiographic assessment at 1 year. In all cases, the proximal femoral ossification nucleus was detected at these subsequent post-treatment evaluations Univariate and multivariate regression analysis was performed to evaluate the association between age at diagnosis and treatment duration with the appearance of the proximal femoral ossification nucleus at the end of brace treatment. Treatment duration was significantly associated with the outcome (B = − 0.024; SE = 0.011; p = 0.032; OR = 0.977; 95% CI: 0.956–0.998), indicating that longer treatment duration was associated with a reduced likelihood of ossification nucleus absence at brace removal. Conversely, age at diagnosis was not significantly associated with the outcome (B = − 0.001; SE = 0.008; p = 0.942; OR = 0.999; 95% CI: 0.983–1.016). Furthermore, linear regression analysis demonstrated that age at diagnosis, alpha angle at T0, beta angle at T0 and treatment duration were not significantly associated with the acetabular index and did not represent independent predictors of this radiographic parameter. Three hips presented an acetabular index above the 90th percentile at the time of ultrasonographic normalization. One female with bilateral dysplasia showed an acetabular index of 33° in the right hip and 38° in the left hip; therefore, a third ultrasound follow-up was performed, and the treatment period was prolonged, resulting in a total duration of 182 days. Another female patient had an acetabular index of 36°; in this case an additional ultrasound follow-up was performed 30 days after the radiographic assessment, with a total treatment duration of 150 days. These patients underwent further radiographic examination at one year of age. The first patient had an AI of 22° on the right and 25° on the left. The second patient had an AI of 22°. In all cases, the growth plate of the proximal femur was present. No complications were recorded. Discussion The Coxaflex brace is similar to the Pavlik one as a dynamic orthosis but provides greater stability. This makes it easier to use, allowing for improved parental compliance. The Pavlik brace remains the preferred treatment for children under 6 months of age, as it is the most widely described, analysed, and considered safe and highly effective in large samples. ( 13 ) Therapeutic success has been reported with the use of other braces, including the Coxaflex (98.3%); however, the small sample size of the study did not allow for a proper comparison with other types of braces. ( 10 ) The available literature on this device is still limited especially compared to the Pavlik brace. This disparity was also highlighted by Pavone et al. (2021), who in a systematic review analysed the main static and dynamic braces used in the treatment of DDH. ( 9 ) The only study in the literature specifically dedicated to the Coxaflex brace, authored by Azzoni et al. (2011), reported a success rate close to 100% on a sample of 59 patients. The authors also observed that more severe DDH require a longer treatment period and that cases treated late require more time to achieve correction. ( 10 ) According to a study by Aarvold et al., the majority of British Society for Children’s Orthopaedic Surgery (BSCOS) members reported that the duration of DDH treatment ranged from 6 to 16 weeks (mostly 12 weeks). ( 14 ) Another survey by Kelley et al. confirmed that most paediatric orthopaedic surgeons believe that DDH treatment should last for three months.( 15 ) Anyway, at the end of the treatment, a control pelvis X-ray is essential to evaluate acetabular angles. ( 16 ) The systematic review by Merchant et al. found an average duration of full-time brace use of 16.4 weeks for dynamic devices and 8.9 weeks for static ones. Bracing is generally maintained full-time, with one hour per day off for child hygiene. ( 17 ) Hines et al. also demonstrated that there are no significant clinical differences between wearing the brace for 23 or 24 hours a day. ( 18 ) The importance of radiographic normalization, in addition to ultrasound, was reiterated by Li et al. (2022), who in a retrospective study demonstrated the possible persistence of the pathology despite ultrasound normalization upon discontinuation of the brace. ( 19 , 20 ) Finally, some recent studies support the use of static braces in the treatment of residual acetabular dysplasia in older infants, when the Pavlik brace is no longer indicated. ( 21 ) These devices appear to improve the acetabular index, although data are still limited. In many centres, the use of a rigid, part-time abduction brace is common, which can promote acetabular remodelling without significantly interfering with the child's activity. ( 22 ) However, the optimal duration of treatment remains a matter of debate. The Coxaflex brace showed a low incidence of complications compared to static braces, confirming its conformity with other dynamic devices. Merchant et al. (2021), in his systematic review, emphasized the greater safety and tolerability of dynamic braces compared to static ones, findings later shared by other authors. ( 17 , 23 ) An advantage of static braces is their design, which reduces the risk of parental errors in positioning, allowing for easier application and minimizing the possibility of incorrect use. Furthermore, these devices can also be used in children over six months of age. In the review by Pavone et al., the success rate for static braces was 93%, with a failure rate of 7%. Although the number of cases analysed (212 hips) is relatively limited, the results confirm the effectiveness of this type of treatment. ( 9 ) Several authors have also reported cases of stabilization of persistent posterior dislocations after failure of the Pavlik dynamic brace using static ones. ( 21 , 24 ) Zgoda et al. documented that the use of dynamic braces for DDH did not interfere with locomotor development, although it showed an average delay of approximately three weeks in the onset of ambulation, with no long-term functional consequences. ( 25 ) This study certainly has some limitations: the follow-up is short. It would be interesting to re-evaluate all children at 2 years of age with an antero-posterior pelvic x-ray to exclude the presence of avascular necrosis according to Salter's criteria. It would also be interesting to expand the sample size. On the other hand, this is the first prospective study on the Coxaflex brace, to the authors' knowledge. In conclusion, the treatment of DDH requires a long period of care, not only from the specialist but also from the parents. Therefore, compliance is essential to achieve a successful outcome. The Coxaflex brace is easy to wear and is well tolerated by the newborn, factors that contribute to achieving therapeutic success, along with early diagnosis. Declarations Author Contribution MR, MS, and MM conceived and designed the study. CDN, VV, and MPM collected the data. MR, FML, DD, and AC performed the hip ultrasound examinations. MM performed the statistical analysis. MR and MS drafted the manuscript. FML and MM critically revised the manuscript for important intellectual content. All authors interpreted the data, reviewed the manuscript, and approved the final version. Data Availability All data supporting the findings of this study are available within the paper and its Supplementary Information. 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J Bone Joint Surg Am 98(14):1215–1221. 10.2106/JBJS.15.01018 Zídka M, Džupa V (2019) Pavlik harness and Frejka pillow: compliance affects results of outpatient treatment. Arch Orthop Trauma Surg 139(11):1519–1524. 10.1007/s00402-019-03179-7 Dyskin E, Ferrick M (2015) Semirigid Abduction Bracing is Effective Treatment of Reducible Developmental Dysplastic Hips after Failure of Pavlik Harness. Ann Orthop Rheumatol 3(2):1045 Zgoda M, Wasilewski P, Wasilewska I, Golicki D (2010) Influence of the treatment of developmental dysplasia of the hip by the abduction brace on locomotor development in children. J Child Orthop 4(1):9–12. 10.1007/s11832-009-0219-0 Tables Table 1. Graf Classification N =44 Age (days) at the end of treatment (M±SD) 2B 3 300±2 2C 30 213±49 D 3 254±56 3A 8 234±66 Table 2. Ultrasound assessments at diagnosis and follow-up Time point Number of hips Mean age / interval (days) Alpha angle (°) Beta angle (°) Statistical significance T0 (Diagnosis) 44 46 ± 40 47 ± 4 62 ± 13 p < 0.001 T1 44 42 ± 13 57 ± 7 54 ± 6 Alpha: p < 0.001; Beta: p = 0.165 T2 44 91 ± 21 63 ± 5 53 ± 6 Alpha p = 0.317; Beta p = 0.017 T3 33 132 ± 22 64 ± 5 51 ± 7 Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterials.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 18 Apr, 2026 Reviewers invited by journal 12 Apr, 2026 Editor assigned by journal 06 Apr, 2026 Submission checks completed at journal 06 Apr, 2026 First submitted to journal 30 Mar, 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. 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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-9271883","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":625277958,"identity":"33963d31-83f6-42a2-aa9c-5cd4c2eb77aa","order_by":0,"name":"Maria Rizzo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIiWNgGAWjYJCCA0DMA8SMDxgYJEB0A9FamA2gWhoJ64ECNgkoA781uu1nHx74wXBPRr7/8LFq3h0WefwNzO0P8GkxO5NucLCHoZiHseFY2m3eMxLFEgcIOMzsQBrDAR6GBB5mxh6z27xtEokNBLWcf8Zw8A9QCxszj1kxSMt8glpupDEcBtnCw8ZjxgzSsoGwlmcMh2UMEngkeNiSJecCtWw8zNg4A7/D0pg/vqlIsAeG2MEPb9vqEucdb3/wAZ8WCDBA5jATVj8KRsEoGAWjgAAAAK8MRZ5VpjudAAAAAElFTkSuQmCC","orcid":"","institution":"Federico II University","correspondingAuthor":true,"prefix":"","firstName":"Maria","middleName":"","lastName":"Rizzo","suffix":""},{"id":625277959,"identity":"22c40c7a-bdec-4431-9076-c681c7f7c5ad","order_by":1,"name":"Michela Saracco","email":"","orcid":"","institution":"Federico II University","correspondingAuthor":false,"prefix":"","firstName":"Michela","middleName":"","lastName":"Saracco","suffix":""},{"id":625277960,"identity":"ec124a40-47a7-49c9-b45c-bffdb1fa8238","order_by":2,"name":"Clara De Negri","email":"","orcid":"","institution":"Federico II University","correspondingAuthor":false,"prefix":"","firstName":"Clara","middleName":"","lastName":"De Negri","suffix":""},{"id":625277961,"identity":"538604da-9c89-4390-880c-aeaab500c399","order_by":3,"name":"Valerio Verdoliva","email":"","orcid":"","institution":"Federico II University","correspondingAuthor":false,"prefix":"","firstName":"Valerio","middleName":"","lastName":"Verdoliva","suffix":""},{"id":625277962,"identity":"4e2893dd-db73-4687-abe4-9dabee5ef80c","order_by":4,"name":"Francesco Maria Lotito","email":"","orcid":"","institution":"Federico II University","correspondingAuthor":false,"prefix":"","firstName":"Francesco","middleName":"Maria","lastName":"Lotito","suffix":""},{"id":625277963,"identity":"52c1e305-d28b-4645-a4e6-0ab853c4880f","order_by":5,"name":"Antonio Colella","email":"","orcid":"","institution":"Giovanni XXIII Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Antonio","middleName":"","lastName":"Colella","suffix":""},{"id":625277964,"identity":"a5761867-2ac4-4b0f-b467-5a4dffeb13ac","order_by":6,"name":"Maria Paola Miolla","email":"","orcid":"","institution":"Giovanni XXIII Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"Paola","lastName":"Miolla","suffix":""},{"id":625277965,"identity":"4882a3f1-f981-4fc3-97df-1c007eb8c2a8","order_by":7,"name":"Daniela Dibello","email":"","orcid":"","institution":"Giovanni XXIII Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Daniela","middleName":"","lastName":"Dibello","suffix":""},{"id":625277966,"identity":"8ab26887-d362-4f1f-b214-19b488e75760","order_by":8,"name":"Massimo Mariconda","email":"","orcid":"","institution":"Federico II University","correspondingAuthor":false,"prefix":"","firstName":"Massimo","middleName":"","lastName":"Mariconda","suffix":""}],"badges":[],"createdAt":"2026-03-30 20:53:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9271883/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9271883/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107322112,"identity":"ab27fed5-902a-4223-9bc8-f11490afb35d","added_by":"auto","created_at":"2026-04-20 10:41:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":846581,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA:\u003c/strong\u003e Female, 18 days of age. Born at term, from a spontaneous delivery and with no family history of DDH. Positive Ortolani test on the left side.She therefore underwent hip ultrasonography according to the Graf method, which showed a type 2C hip on the left with an α angle of 49° and a β angle of 60° (T0).\u003c/p\u003e\n\u003cp\u003ePatient was therefore immediately treated with a Coxaflex brace full-time, with careful parental education regarding its use (worn 23 hours/day).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1B: 50 days Follow-up (T1\u003c/strong\u003e): \u0026nbsp;Improvement in the Graf angles, with an α angle of 60° and a β angle of 55°. The ossification nucleus of the femoral head was also visible.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1C: Follow-up performed at 90 days (T2):\u003c/strong\u003e α angle = 67°, while the β angle = 55°\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e120 days follow-up (T3)\u003c/strong\u003e: \u0026nbsp;US stabilization of the Graf angle values within the normal range ( α angle= 69° and β = 55°)( Figure 1D). Radiographic follow-up performed at 120 days (Figure 1E). The radiograph showed, on the affected left side, an acetabular index (AI) of 18°, within the normal percentile range for age and sex (\u0026lt;25°) and comparable to the contralateral side (AI 20°).\u003c/p\u003e\n\u003cp\u003eAfter normalization of ultrasound and radiographic parameters, the patient discontinued the Coxaflex brace.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9271883/v1/dd58c7171a838d7f4956b810.png"},{"id":107322133,"identity":"cb128a2c-8bb8-42db-819d-4ab4e77606d9","added_by":"auto","created_at":"2026-04-20 10:42:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":96030,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9271883/v1/26a2790f597e836a2fb4baa0.png"},{"id":107322239,"identity":"5963b9d5-f7ae-45dd-8d59-7761f9b25ac0","added_by":"auto","created_at":"2026-04-20 10:42:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1173776,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9271883/v1/1b3989d7-ed0b-428d-97d4-652e5840b4aa.pdf"},{"id":107322127,"identity":"af546063-177f-499a-a54b-eaf68cd2f57f","added_by":"auto","created_at":"2026-04-20 10:42:03","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":14644,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-9271883/v1/46750ed74c8d12918b76ae39.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eUltrasound and radiographic outcomes of the Coxaflex brace in the treatment of developmental dysplasia of the hip (DDH): a multicentre prospective study\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eDevelopmental dysplasia of the hip (DDH) is a congenital disorder of the hip joint that ranges from mild acetabular dysplasia to complete hip dislocation. It is one of the most common orthopaedic conditions in newborns, with an incidence varying based on factors such as gender, family history, and breech presentation.(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eEarly detection and timely treatment are crucial to ensuring proper hip development, preventing long-term complications such as joint instability, gait abnormalities, and early-onset osteoarthritis. Currently, a screening program is implemented to facilitate the early diagnosis of DDH. A significant reduction in the rate of surgery for DDH later in life was shown after the introduction of universal ultrasound screening.(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Although clinical examination plays a crucial role in the diagnostic process, studies indicate that up to 54% of dislocations have no clinical signs including no Ortolani sign and no risk factors.(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Nowadays, ultrasound is considered the gold standard in the diagnostic process, this is mainly because the US examination of newborns\u0026rsquo; hips allows a morphological study of both the bone and the cartilage components and also permits a dynamic evaluation of hip instability, so a dysplasia can be identified in vivo, immediately in the peri-natal period minimizing exposure to X-ray radiation.(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) The Graf classification is the most widely used system, based on the measurement of the alpha and beta angles, and categorizes dysplastic hips into four main types according to these angular values. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe management of DDH depends on the patient's age and the severity of the condition. Among the most employed therapeutic options are dynamic and static splints, which are selected based on the reducibility of the hip and the developmental stage of the child.(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eStatic splints are designed to achieve a \"rigid reduction\" by immobilizing the hips in a fixed position of abduction and flexion, without allowing active joint motion. These devices are typically composed of rigid materials. Evidence suggests that static splints are associated with a higher incidence of complications, particularly avascular necrosis (AVN), when compared to dynamic orthoses. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e)The most widely accepted indication is in children older than 6 to 9 months of age, who require prolonged positioning in abduction due to persistent acetabular dysplasia and/or subluxation. (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eA dynamic splint facilitates a \u0026ldquo;dynamic reduction,\u0026rdquo; allowing controlled movement of the lower limbs while maintaining the hips in a position of flexion and abduction. The most widely accepted indication is the presence of hip instability that can be centred through concentric reduction in under 6 months infants. Among the dynamic splints employed in the treatment of DDH, the Pavlik harness is the most extensively studied and commonly used brace.(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e) However, alternative devices, such as the Coxaflex brace, have been developed to provide effective treatment while potentially addressing limitations associated with other bracing methods.\u003c/p\u003e \u003cp\u003eThe Coxaflex brace aims to achieve a stable reduction while allowing controlled movement. This position allows for the concentric reduction of the femoral head within the acetabulum, facilitating remodelling. 6 Despite its use in clinical practice, data on its effectiveness remain limited compared to the Pavlik harness. The aim of this study is understanding the impact of the Coxaflex brace as a conservative therapeutic option on hip development, as well as its potential advantages and limitations, to optimize treatment strategies for DDH.(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe authors analysed the ultrasound (US) and radiographic outcomes of the Coxaflex brace in a cohort of infants with DDH. By assessing US parameters such as the evolution of the α angle, acetabular index (AI), and overall hip stability over the treatment period.\u003c/p\u003e \u003cp\u003eThe findings may contribute to refining current treatment protocols and guiding clinical decision-making in paediatric orthopaedics.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eData from patients evaluated for DDH from June 2022 to May 2025 was prospectively gathered and retrospectively reviewed. Parents of each patient enrolled expressed written informed consent to participate.\u003c/p\u003e \u003cp\u003eThe study inclusion criteria were patients less than 6 months of age diagnosed with a reduced but displaceable (Barlow+), unilateral or bilateral. (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) Exclusion criteria were infants greater than 6 months of age at the time of diagnosis, those with less than 6 months of follow-up to assess outcome, presence of a fixed or teratologic dislocation or arthrogryposis, or those with stable ultrasonic hip dysplasia. Infants unable to wear the brace due to femoral nerve palsy within the first 2 weeks of initiating treatment and those not compliant were also excluded.\u003c/p\u003e \u003cp\u003eAll patients were evaluated clinically by neonatologists at birth and then by experienced pediatric orthopedists. Both children with positive tests and risk factors at birth and children without risk factors who underwent ultrasound screening were enrolled. They were subsequently reevaluated clinically and by ultrasound every 45 days during treatment until resolution.\u003c/p\u003e \u003cp\u003eThe ultrasound analysis included measurement of the Graf alpha and beta angles and the age of appearance of the femoral head growth nucleus in days. Ultrasound examinations, performed according to the Graf method using a linear transducer (7.5 MHz), provided an accurate in vivo analysis for the diagnosis of DDH. All hips were examined sonographically. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) All enrolled children underwent anteroposterior pelvic x-rays to assess the acetabular index upon removal of the brace.\u003c/p\u003e \u003cp\u003eResidual dysplasia was defined as acetabular index greater than two standard deviations above the value expected for the age, as defined by Tonnis and subsequent revisions. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe treatment was based on the use of the Coxaflex harness, classified as a dynamic brace but with greater rigidity compared to other dynamic harnesses. Coxaflex is a medical hip abduction orthosis (splint) designed to treat hip issues such as DDH or to keep the hip joint centred and stable after it has been reduced in position. Coxaflex holds the baby\u0026rsquo;s hips in a controlled flexion and abduction position which is considered a physiologically safe posture that promotes correct hip socket development. The device includes adjustable bars and straps that let clinicians set the amount of flexion (bending) and abduction (outward angle) to suit the child\u0026rsquo;s condition. Its design allows natural restful muscle positions while preventing extreme positions that could impair blood flow or cause discomfort. The Coxaflex brace allows for hip flexion in a range of 90\u0026deg; to 100\u0026deg; and abduction between 45\u0026deg; and 50\u0026deg;. The brace must be worn 23 hours a day for a minimum period of 16 weeks or until ultrasound resolution.\u003c/p\u003e \u003cp\u003eThe following demographic data were collected: sex, laterality, age (days), family history, associated malformations, positive test results, Graf classification at the first ultrasound evaluation and trend of alpha and beta values ​​at all subsequent check-ups, acetabular index on x-rays and age of appearance of the ossification nucleus.\u003c/p\u003e \u003cp\u003eUltrasound values ​​of the alpha and beta angles were compared at T0 (enrollment), T1 (45 days from T0) and T2 (90 days from T0). In cases where alpha had not exceeded 60 degrees at T2, a further check was scheduled at T3 (a further 45 days from T2). Before removal of the brace, all children underwent x-ray. In patients who showed no ultrasound or radiographic evidence of ossification of the proximal femur at the time of brace removal, an ultrasound scan was performed after 3 months.\u003c/p\u003e \u003cp\u003eIn patients who showed ultrasound normalization of the hip but an AI\u0026thinsp;\u0026gt;\u0026thinsp;90th percentile, the brace was not removed and they continued to wear the brace with further ultrasound monitoring. In these patients, an X-ray was finally performed at one year to reevaluate AI.\u003c/p\u003e \u003cp\u003eUltrasound was performed by two independent experienced pediatric orthopedists and acetabular indices were measured by two independent observers.\u003c/p\u003e \u003cp\u003eClinical, ultrasound and radiographic success was defined as obtaining a stable hip on physical examination and normalization ultrasound hip ultrasound without need to perform a closed or open reduction or to use a rigid abduction orthosis prior to achieving clinical stability.\u003c/p\u003e \u003cp\u003eComplications were recorded. Complications include failure of reduction, femoral nerve palsy and residual acetabular dysplasia.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS (IBM Statistics). Data was collected using Excel (Microsoft). To incorporate the data of the participants into data analysis regardless of the protocol adherence, all the analyses were performed in accordance with the intention to-treat principle. Appropriate sample size calculation and power analysis were assessed during the planning of the clinical study. Paired t-test or Wilcoxon signed rank test was applied to assess changes after the proposed treatment. Data were expressed as frequencies and percentages for categorical variables and mean and standard deviation (M\u0026thinsp;\u0026plusmn;\u0026thinsp;SD) for continuous variables. Intra-class correlation coefficients were used as a measure of concordance in radiographic evaluations between observers. A confidence level of 95% was selected and a \u003cem\u003ep\u003c/em\u003e-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 chosen as significance threshold.\u003c/p\u003e \u003cp\u003eUnivariate and multivariate logistic regression analysis was performed to identify predictors of the presence of the proximal femoral ossification nucleus at the end of brace treatment. Age at diagnosis, alpha angle at T0, Beta angle at T0 and treatment duration were tested as possible predictors.\u003c/p\u003e \u003cp\u003eLinear regression analysis was carried out to assess possible predictors of the AI at diagnosis, alpha angle at T0, Beta angle at T0 and treatment duration were tested as possible outcome predictors.\u003c/p\u003e \u003cp\u003eA two-sided p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant, with a confidence level set at 95%.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 44 hips were evaluated, including 22 unilateral and 11 bilateral cases, comprising 18 right and 26 left hips. The study population included 28 females and 5 males. \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003e\u0026ndash;clinical case)\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDetailed demographic data are reported in the \u003cb\u003eSupplementary Material\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eThe median age at diagnosis (T0) was 46\u0026thinsp;\u0026plusmn;\u0026thinsp;40 days (range, 4\u0026ndash;150 days) and the average age at the end of treatment was 224\u0026thinsp;\u0026plusmn;\u0026thinsp;54 days. The mean alpha angle at T0 was 47\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u0026deg;, and the mean beta angle was 62\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u0026deg;. Nineteen hips demonstrated a positive Ortolani manoeuvre. Hip types according to the classification system are summarized in \u003cb\u003eTable\u0026nbsp;1\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eThe concordance in radiographic evaluations between observers for ultrasound and radiographic assessments was greater than 80%.\u003c/p\u003e \u003cp\u003eUltrasound follow-up assessments were performed at T1, with a mean interval of 42\u0026thinsp;\u0026plusmn;\u0026thinsp;13 days; at T2, with a mean interval of 91\u0026thinsp;\u0026plusmn;\u0026thinsp;21 days; and at T3, where 33 hips were evaluated, with a mean interval of 132\u0026thinsp;\u0026plusmn;\u0026thinsp;22 days.\u003c/p\u003e \u003cp\u003eAt T1, the mean alpha and beta angles were 57\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u0026deg; and 54\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u0026deg;, respectively, showing a statistically significant difference compared with the time of diagnosis (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). At the second follow-up (T2), the mean alpha and beta angles were 63\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u0026deg; and 53\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u0026deg;, respectively. The alpha angle demonstrated a statistically significant increase (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), whereas the beta angle did not show a statistically significant reduction on paired t-test analysis (p\u0026thinsp;=\u0026thinsp;0.165). \u003cb\u003e(Fig.\u0026nbsp;2 \u0026ndash; angles graph)\u003c/b\u003e At the ultrasound evaluation performed at T3, the mean alpha angle was 64\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u0026deg;, and the mean beta angle was 51\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u0026deg;, with no statistically significant differences compared with the previous follow-up (p\u0026thinsp;=\u0026thinsp;0.317 and p\u0026thinsp;=\u0026thinsp;0.017, respectively), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e. All ultrasound examinations were performed by paediatric orthopaedic surgeons with expertise in hip ultrasonography. A standard anteroposterior pelvic radiograph was obtained prior to brace discontinuation, at a mean follow-up of 162\u0026thinsp;\u0026plusmn;\u0026thinsp;40 days. At the time of imaging, patients had a mean age of 208\u0026thinsp;\u0026plusmn;\u0026thinsp;57 days. This evaluation allowed assessment of the acetabular index (AI) and comparison with age- and sex-specific percentiles. The mean AI was 23\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u0026deg; (range 14\u0026deg;-38\u0026deg;), consistent with values reported in the literature. At the end of brace treatment, 30 hips (68%) showed ultrasonographic evidence of the proximal femoral ossification nucleus, with a mean age of 164\u0026thinsp;\u0026plusmn;\u0026thinsp;45 days. However, hips without ultrasonographic or radiographic evidence of the proximal femoral ossification nucleus at the time of brace discontinuation, underwent additional follow-up evaluations, including ultrasound at 3 and 6 months after brace removal and radiographic assessment at 1 year. In all cases, the proximal femoral ossification nucleus was detected at these subsequent post-treatment evaluations\u003c/p\u003e \u003cp\u003eUnivariate and multivariate regression analysis was performed to evaluate the association between age at diagnosis and treatment duration with the appearance of the proximal femoral ossification nucleus at the end of brace treatment. Treatment duration was significantly associated with the outcome (B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.024; SE\u0026thinsp;=\u0026thinsp;0.011; p\u0026thinsp;=\u0026thinsp;0.032; OR\u0026thinsp;=\u0026thinsp;0.977; 95% CI: 0.956\u0026ndash;0.998), indicating that longer treatment duration was associated with a reduced likelihood of ossification nucleus absence at brace removal. Conversely, age at diagnosis was not significantly associated with the outcome (B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.001; SE\u0026thinsp;=\u0026thinsp;0.008; p\u0026thinsp;=\u0026thinsp;0.942; OR\u0026thinsp;=\u0026thinsp;0.999; 95% CI: 0.983\u0026ndash;1.016).\u003c/p\u003e \u003cp\u003eFurthermore, linear regression analysis demonstrated that age at diagnosis, alpha angle at T0, beta angle at T0 and treatment duration were not significantly associated with the acetabular index and did not represent independent predictors of this radiographic parameter.\u003c/p\u003e \u003cp\u003eThree hips presented an acetabular index above the 90th percentile at the time of ultrasonographic normalization. One female with bilateral dysplasia showed an acetabular index of 33\u0026deg; in the right hip and 38\u0026deg; in the left hip; therefore, a third ultrasound follow-up was performed, and the treatment period was prolonged, resulting in a total duration of 182 days. Another female patient had an acetabular index of 36\u0026deg;; in this case an additional ultrasound follow-up was performed 30 days after the radiographic assessment, with a total treatment duration of 150 days. These patients underwent further radiographic examination at one year of age. The first patient had an AI of 22\u0026deg; on the right and 25\u0026deg; on the left. The second patient had an AI of 22\u0026deg;. In all cases, the growth plate of the proximal femur was present.\u003c/p\u003e \u003cp\u003eNo complications were recorded.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe Coxaflex brace is similar to the Pavlik one as a dynamic orthosis but provides greater stability. This makes it easier to use, allowing for improved parental compliance. The Pavlik brace remains the preferred treatment for children under 6 months of age, as it is the most widely described, analysed, and considered safe and highly effective in large samples. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) Therapeutic success has been reported with the use of other braces, including the Coxaflex (98.3%); however, the small sample size of the study did not allow for a proper comparison with other types of braces. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) The available literature on this device is still limited especially compared to the Pavlik brace. This disparity was also highlighted by Pavone et al. (2021), who in a systematic review analysed the main static and dynamic braces used in the treatment of DDH. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e) The only study in the literature specifically dedicated to the Coxaflex brace, authored by Azzoni et al. (2011), reported a success rate close to 100% on a sample of 59 patients. The authors also observed that more severe DDH require a longer treatment period and that cases treated late require more time to achieve correction. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) According to a study by Aarvold et al., the majority of British Society for Children\u0026rsquo;s Orthopaedic Surgery (BSCOS) members reported that the duration of DDH treatment ranged from 6 to 16 weeks (mostly 12 weeks). (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) Another survey by Kelley et al. confirmed that most paediatric orthopaedic surgeons believe that DDH treatment should last for three months.(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) Anyway, at the end of the treatment, a control pelvis X-ray is essential to evaluate acetabular angles. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe systematic review by Merchant et al. found an average duration of full-time brace use of 16.4 weeks for dynamic devices and 8.9 weeks for static ones. Bracing is generally maintained full-time, with one hour per day off for child hygiene. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) Hines et al. also demonstrated that there are no significant clinical differences between wearing the brace for 23 or 24 hours a day. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe importance of radiographic normalization, in addition to ultrasound, was reiterated by Li et al. (2022), who in a retrospective study demonstrated the possible persistence of the pathology despite ultrasound normalization upon discontinuation of the brace. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) Finally, some recent studies support the use of static braces in the treatment of residual acetabular dysplasia in older infants, when the Pavlik brace is no longer indicated. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) These devices appear to improve the acetabular index, although data are still limited. In many centres, the use of a rigid, part-time abduction brace is common, which can promote acetabular remodelling without significantly interfering with the child's activity. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) However, the optimal duration of treatment remains a matter of debate.\u003c/p\u003e \u003cp\u003eThe Coxaflex brace showed a low incidence of complications compared to static braces, confirming its conformity with other dynamic devices. Merchant et al. (2021), in his systematic review, emphasized the greater safety and tolerability of dynamic braces compared to static ones, findings later shared by other authors. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eAn advantage of static braces is their design, which reduces the risk of parental errors in positioning, allowing for easier application and minimizing the possibility of incorrect use. Furthermore, these devices can also be used in children over six months of age. In the review by Pavone et al., the success rate for static braces was 93%, with a failure rate of 7%. Although the number of cases analysed (212 hips) is relatively limited, the results confirm the effectiveness of this type of treatment. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e) Several authors have also reported cases of stabilization of persistent posterior dislocations after failure of the Pavlik dynamic brace using static ones. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eZgoda et al. documented that the use of dynamic braces for DDH did not interfere with locomotor development, although it showed an average delay of approximately three weeks in the onset of ambulation, with no long-term functional consequences. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThis study certainly has some limitations: the follow-up is short. It would be interesting to re-evaluate all children at 2 years of age with an antero-posterior pelvic x-ray to exclude the presence of avascular necrosis according to Salter's criteria. It would also be interesting to expand the sample size. On the other hand, this is the first prospective study on the Coxaflex brace, to the authors' knowledge.\u003c/p\u003e \u003cp\u003eIn conclusion, the treatment of DDH requires a long period of care, not only from the specialist but also from the parents. Therefore, compliance is essential to achieve a successful outcome. The Coxaflex brace is easy to wear and is well tolerated by the newborn, factors that contribute to achieving therapeutic success, along with early diagnosis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMR, MS, and MM conceived and designed the study. CDN, VV, and MPM collected the data. MR, FML, DD, and AC performed the hip ultrasound examinations. MM performed the statistical analysis. MR and MS drafted the manuscript. FML and MM critically revised the manuscript for important intellectual content. All authors interpreted the data, reviewed the manuscript, and approved the final version.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data supporting the findings of this study are available within the paper and its Supplementary Information.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKuitunen I, Uimonen MM, Haapanen M, Sund R, Helenius I, Ponkilainen VT (2022) Incidence of Neonatal Developmental Dysplasia of the Hip and Late Detection Rates Based on Screening Strategy: A Systematic Review and Meta-analysis. 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Ann Orthop Rheumatol 3(2):1045\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZgoda M, Wasilewski P, Wasilewska I, Golicki D (2010) Influence of the treatment of developmental dysplasia of the hip by the abduction brace on locomotor development in children. J Child Orthop 4(1):9\u0026ndash;12. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11832-009-0219-0\u003c/span\u003e\u003cspan address=\"10.1007/s11832-009-0219-0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003eGraf Classification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003eN =44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003eAge (days) at the end of treatment (M\u0026plusmn;SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e2B\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e300\u0026plusmn;2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e2C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e213\u0026plusmn;49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003eD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e254\u0026plusmn;56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e3A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 149px;\"\u003e\n \u003cp\u003e234\u0026plusmn;66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Table 2. Ultrasound assessments at diagnosis and follow-up\u003c/strong\u003e\u003c/p\u003e\n\u003ctable style=\"border-width: medium; border-style: none; border-color: currentcolor; border-image: initial; width: 100%;\" cellspacing=\"3\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 14.0173%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime point\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15.1734%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of hips\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24.711%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMean age / interval (days)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.5954%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAlpha angle (\u0026deg;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13.1503%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBeta angle (\u0026deg;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.3526%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eStatistical significance\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 14.0173%;\"\u003e\n \u003cp\u003eT0 (Diagnosis)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15.1734%;\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24.711%;\"\u003e\n \u003cp\u003e46 \u0026plusmn; 40\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.5954%;\"\u003e\n \u003cp\u003e47 \u0026plusmn; 4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13.1503%;\"\u003e\n \u003cp\u003e62 \u0026plusmn; 13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 18.3526%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003ep \u0026lt; 0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 14.0173%;\"\u003e\n \u003cp\u003eT1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 15.1734%;\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 24.711%;\"\u003e\n \u003cp\u003e42 \u0026plusmn; 13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 14.5954%;\"\u003e\n \u003cp\u003e57 \u0026plusmn; 7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 13.1503%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e54 \u0026plusmn; 6\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 18.3526%;\"\u003e\n \u003cp\u003eAlpha: p \u0026lt; 0.001;\u003cbr\u003e\u0026nbsp;Beta: p = 0.165\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 14.0173%;\"\u003e\n \u003cp\u003eT2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 15.1734%;\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 24.711%;\"\u003e\n \u003cp\u003e91 \u0026plusmn; 21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 14.5954%;\"\u003e\n \u003cp\u003e63 \u0026plusmn; 5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 13.1503%;\"\u003e\n \u003cp\u003e53 \u0026plusmn; 6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 18.3526%;\"\u003e\n \u003cp\u003eAlpha p = 0.317;\u003cbr\u003e\u0026nbsp;Beta p = 0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 14.0173%;\"\u003e\n \u003cp\u003eT3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15.1734%;\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24.711%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e132 \u0026plusmn; 22\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.5954%;\"\u003e\n \u003cp\u003e64 \u0026plusmn; 5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13.1503%;\"\u003e\n \u003cp\u003e51 \u0026plusmn; 7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\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":"european-journal-of-orthopaedic-surgery-and-traumatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejos","sideBox":"Learn more about [European Journal of Orthopaedic Surgery \u0026 Traumatology](http://link.springer.com/journal/590)","snPcode":"590","submissionUrl":"https://submission.springernature.com/new-submission/590/3","title":"European Journal of Orthopaedic Surgery \u0026 Traumatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"developmental dysplasia of the hip, Coxaflex brace, dynamic brace, Infant hip instability","lastPublishedDoi":"10.21203/rs.3.rs-9271883/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9271883/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEarly diagnosis is essential for the treatment of developmental dysplasia of the hip (DDH), and the use of abduction bracing is considered the gold standard for patients \u0026lt; 6 months of age. The aim of this study is to report an analysis of the results of using the coxaflex abduction brace.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData from 44 DDH were prospectively analysed in two different paediatric orthopaedic units. The diagnosis was made clinically and by ultrasound during the outpatient screening visit. All patients underwent follow-up ultrasound examinations. Radiographic examinations were requested at the end of treatment to assess the acetabular index (AI) and the radiographic position of the proximal femoral growth plate.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe mean age at the start of treatment was 46 days (range, 4–150 days). The first follow-up (T1) was performed at 42 ± 13 days of treatment, a second follow-up (T2) at 91 ± 21 days, and a third follow-up (T3) at 134 ± 22 days. Ultrasound examinations were performed at each follow-up, which revealed a mean α angle of 47°±4° at the start of treatment. At the T1 follow-up, the mean α angle was 57°±7°, while on T2 and T3 they measured 63°±5° and 64°±5°, respectively. The angular increase on T1 and T2 was statistically significant (p \u0026lt; 0.001). The X-ray examination was performed at an average of 162 ± 40 days and showed an AI of 23°±5° (range 14°-38°).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e The Coxaflex brace is easy to wear and is well tolerated by the newborn, factors that contribute to achieving therapeutic success, along with early diagnosis.\u003c/p\u003e","manuscriptTitle":"Ultrasound and radiographic outcomes of the Coxaflex brace in the treatment of developmental dysplasia of the hip (DDH): a multicentre prospective study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-20 10:39:59","doi":"10.21203/rs.3.rs-9271883/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"141097475279225190772817461979051189280","date":"2026-04-18T04:36:03+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-13T02:52:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-06T12:21:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-06T12:20:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Orthopaedic Surgery \u0026 Traumatology","date":"2026-03-30T20:47:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-orthopaedic-surgery-and-traumatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejos","sideBox":"Learn more about [European Journal of Orthopaedic Surgery \u0026 Traumatology](http://link.springer.com/journal/590)","snPcode":"590","submissionUrl":"https://submission.springernature.com/new-submission/590/3","title":"European Journal of Orthopaedic Surgery \u0026 Traumatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"0859005e-e9cd-496e-af7d-5eeddc96f14f","owner":[],"postedDate":"April 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-20T10:40:00+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-20 10:39:59","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9271883","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9271883","identity":"rs-9271883","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}