The Pavlik method: a systematic review of current concepts

Study on the efficacy of brace therapy for developmental dysplasia of the hip with Graf IIc and greater severity

To assess changes in the α and β angle with brace treatment in DDH classified as Type Graf IIc, D, III, and IV; to study the α angle threshold that can predict the treatment effect; to analyze the effective rate in different groups. A retrospective study was conducted on children from 2013 to 2018 with Graf type IIc and greater diagnosed with ultrasound (US). Brace therapy was applied to 356 patients, with 423 affected hips (Graf IIc: 202 hips; Graf D: 17 hips; Graf III: 118 hips; and Graf IV: 86 hips). For follow-up efficacy analyses using US, X-ray and clinical examination, based on the success of early treatment of the brace, the outcomes were divided into 'effective' and 'noneffective' groups. The statistical results showed that the α angle increased ( P  < 0.05) and the β angle decreased ( P  < 0.05). When α≥43°, the accuracy of success with early treatment was 95.95%. The overall effective rate of bracing treatment was 74.70%. Children with α ≥ 43° are recommended to receive brace therapy as soon as possible and demonstrate the best effects. The effective rate varies across different Graf types and the age at treatment initiation. Brace therapy is more effective for Graf IIc and D hips compared to Graf III and IV.

Reapplication of the Pavlik Harness for Treatment of Developmental Dysplasia of the Hip After Initial Pavlik Harness Failure

OBJECTIVE

The Pavlik harness (PH) has been widely used as the standard treatment for infants with developmental dysplasia of the hip (DDH). When the initial application of the PH fails, alternative treatments, such as closed reduction, open reduction, and reapplication of the PH will be considered. Compared with other treatments, reapplication of the PH offers certain advantages, including simplicity and reduced physical, and psychological stress, on both infants and caregivers. This study aims to investigate the effectiveness of reapplying the PH in patients with DDH.

METHODS

This study included patients with DDH (complete dislocation) who were treated by reapplication of PH between 1988 and 2012. Patients who were able to follow-up for more than 5 years were included. We examined the reduction rate and several factors to identify indicators associated with successful reduction during reapplication, including age, sex, side of hip dislocation, and the presence of the Ortolani sign. At the final follow-up, hip development was assessed using the Severin classification, whereas avascular necrosis (AVN) was evaluated using the Kalamchi classification and the Salter criteria.

RESULTS

A total of 56 patients (48 females and 8 males) and 57 hips were included in this study. The mean age at first and second application of PH was 4.2 months old (range: 0.12 to 6.4), and 5.8 months old (3.0 to 11.4), respectively. The reduction rate was 49% (28 out of 57 hips). Among the successfully reduced hips, the AVN rate was 3.6% (1 out of 28 hips). The Severin classification revealed 27 hips in class I and 1 hip in class III. Statistical analysis indicated a significantly higher proportion of left hip involvement in the reduction group (85% vs 41%, χ 2 test, P < 0.001). Although not statistically significant, the rate of positive Ortolani sign tended to be higher in the reduction group (61% vs 38%, χ 2 test, P = 0.06).

CONCLUSION

The reapplication method demonstrated a 49% reduction rate and a low AVN rate of 3.6% in our study. It is worth considering for patients who fail the initial PH treatment, particularly in cases of left-side dislocation and a positive Ortolani sign during the initial application.

Radiological long-term follow-up up to 12 years of initially ultrasound unstable hip types D, III and IV after treatment with the Tübingen splint worn as a plaster

INTRODUCTION

The treatment of ultrasound unstable hips with the Tübingen splint is currently under discussion. However, there is a lack of long-term follow-up data. This study presents to the best of our knowledge first radiological mid-term to long-term data of the successful initial treatment with the Tübingen splint of ultrasound unstable hips.

MATERIALS AND METHODS

From 2002 to 2022 the treatment of ultrasound unstable hips type D, III and IV (age ≤ 6 weeks, no severe limitation of abduction) with the Tübingen splint worn as a plaster is evaluated. Based on data derived from routine X-rays during the follow-up period, a radiological follow-up (FU) analysis until the age of 12 years was performed. The acetabular index (ACI) and center-edge angle (CEA) were measured and classified according to Tönnis as normal findings (NF), slightly (sliD) or severely dysplastic (sevD).

RESULTS

193 of 201 (95.5%) unstable hips could be successfully treated showing normal findings with an alpha angle > 65°. The few patients showing treatment failures were successfully treated applying a Fettweis plaster (human position) under anesthesia. The radiological FU of 38 hips showed a favorable trend with increase of normal findings from 52.8% to 81.1% and decrease of 38.9% to 19.9% of sliD respectively 8.3% to 0% of sevD hips. The analysis of avascular necrosis of the femoral head showed 2 cases (5.3%) of grade 1 according to Kalamchi and McEwen, which were improving over time in the further course.

CONCLUSIONS

The Tübingen splint as alternative to replace a plaster has proven a successful therapeutic option for ultrasound unstable hips type D, III and IV with favorable and over time improving radiological parameter up to the age of 12 years.

Universal screening may reduce the incidence of late diagnosis of developmental dysplasia of the hip : a systematic review and meta-analysis

AIMS

We investigated the prevalence of late developmental dysplasia of the hip (DDH), abduction bracing treatment, and surgical procedures performed following the implementation of universal ultrasound screening versus selective ultrasound screening programmes.

METHODS

A systematic search of PubMed, Embase, The Cochrane Library, OrthoSearch, and Web of Science from the date of inception of each database until 27 March 2022 was performed. The primary outcome of interest was the prevalence of late detection of DDH, diagnosed after three months. Secondary outcomes of interest were the prevalence of abduction bracing treatment and surgical procedures performed in childhood for dysplasia. Only studies describing the primary outcome of interest were included.

RESULTS

A total of 31 studies were identified, of which 13 described universal screening and 20 described selective screening. Two studies described both. The prevalence of late DDH was 0.10 per 1,000 live births (95% confidence interval (CI) 0.00 to 0.39) in the universal screening group and 0.45 per 1,000 live births (95% CI 0.31 to 0.61) in the selective screening group. Abduction bracing treatment was performed on 55.54 per 1,000 live births (95% CI 24.46 to 98.15) in the universal screening group versus 0.48 per 1,000 live births (95% CI 0.07 to 1.13) in the selective screening group. Both the universal and selective screening groups had a similar prevalence of surgical procedures in childhood for dysplasia being performed (0.48 (95% CI 0.32 to 0.63) vs 0.49 (95% CI 0.31 to 0.71) per 1,000 live births, respectively).

CONCLUSION

Universal screening showed a trend towards lower prevalence of late DDH compared to selective screening. However, it was also associated with a significant increase in the prevalence of abduction bracing without a significant reduction in the prevalence of surgical procedures in childhood for dysplasia being performed. High-quality studies comparing both treatment methods are required, in addition to studies into the natural history of missed DDH.Cite this article: Bone Joint J 2023;105-B(2):198-208.

Clinical and sonographic improvement of developmental dysplasia of the hip: analysis of 948 patients

BACKGROUND

Developmental dysplasia of the hip is a common condition, which varies in severity. Abduction treatment is widely used to correct the development of the hips, but mild forms of DDH can also recover spontaneously. The purpose of this study was to evaluate factors affecting the rate of improvement of developmental dysplasia of the hip, and evaluate any risk factors slowing the process.

MATERIAL AND METHODS

The study population consisted of patients diagnosed with DDH in Tampere University hospital in the years 1998-2018. Data were retrospectively collected, and associations between clinical variables and rate of improvement were analyzed. Alpha angles were assessed monthly, and associations between risk factors and improvement of alpha angles were studied. A total of 948 patients were included in the analysis.

RESULTS

More severe first status of the hips was associated with faster improvement in dynamic ultrasound compared to milder DDH in univariate design in first 3 months of age; in the multivariable design, Ortolani positivity was conversely associated with lower alpha angles in 1-month follow-up. Immediate abduction treatment was associated with faster recovery rate compared to delayed abduction or watchful waiting. Female sex and positive family history were associated with slower rate of improvement and lower alpha angles. In multivariable design, female sex, positive family history and treatment strategy remained statistically significant as initiation time of the treatment explained the first found association of clinical hip status and the recovery rate after 2 months of age.

CONCLUSION

Female sex and positive family history might be independent risk factors for slower recovery in DDH before 6 months of age. These children might need special attention in their follow-up plans and abduction treatment.

Failure to achieve reduction on developmental dysplasia of hip: an ultrasound evaluation

BACKGROUND

Ultrasound examination of the medial side of the hip joint has been rarely used to evaluate the status of developmental dysplasia of the hip (DDH) in Pavlik harness treatment according to the literature.

PURPOSE

To analyze the effects of cartilaginous acetabulum, hip joint labrum, and acetabular tissue on the reduction of DDH.

MATERIAL AND METHODS

A total of 50 cases (100 hips) were detected by the Graf method with a high-frequency linear transducer (L 5-12), and there were 59 dislocated hips and 41 non-dislocated hips. Patients were treated with a Pavlik harness. Ultrasound examination of the medial side of the hip joint was performed for follow-up. The hip joints were divided into three groups: the non-dislocated group; the reducible group; and the non-reducible group.

RESULTS

The success rate of reduction was significantly higher when the acetabulum cartilage was located on the cephalic side (chi-square = 28.12, P < 0.001). The success rate was also significantly higher when the hip joint labrum was located on the cephalic side (chi-square = 17.21, P < 0.001). Type III and D had a higher success rate of reduction than type IV (P < 0.001). The pairwise comparison of the measurements of acetabular tissue between the non-dislocated group, the reducible group, and the non-reducible group showed statistical differences (P < 0.001).

CONCLUSION

The present study confirmed that the location of acetabulum cartilage and hip joint labrum affected the outcome of treatment. The degree of dislocation and the amount of acetabular tissue were correlated with the success rate of treatment.

A Survey of Parents' and Carers' Perceptions of Parenting a Child With Developmental Dysplasia of the Hip

PURPOSE

To explore parents' and carers' perceptions of parenting a child with developmental dysplasia of the hip (DDH).

METHODS

A retrospective analysis of a questionnaire of parents and carers of children with hip dysplasia. Data analysis was guided by qualitative content analysis.

RESULTS

There were 753 responses describing a range of parenting experiences. Three themes emerged: arduous parenting , detailed the parenting challenges, both practical and emotional posed by the management of DDH; insufficient understanding , described the social disconnection experienced by the respondents due to a lack of empathy from others; inconsistent guidance , encompassed respondents' reliance on health professionals for information and support, yet frustration at variability in the management of DDH.

CONCLUSIONS

Overall, having to care for a child with DDH has a negative effect on the practice of parenting. Health professionals can support parenting and provide consistent education to assist parents' understanding of the complex nature of DDH management. What this study adds to the evidence: Despite a good prognosis, the diagnosis of hip dysplasia has a negative effect on of parenting. Parents and carers of children with hip dysplasia rely on the support of health professionals but find the associated loss of parenting autonomy distressing.

Twelve-week standard of care protocol longer than median time to normalization among IIc hips treated with Pavlik harness

Best treatment protocols for infants with developmental dysplasia of the hip (DDH) are poorly defined. This study estimates the time to normalization among Graf IIc hips undergoing Pavlik harness treatment. Following institutional review board approval, patients referred for DDH evaluation at a pediatric institution between 2009 and 2018 (n = 1424 hips/712 patients) were identified. We isolated all Graf IIc hips that underwent Pavlik harness treatment (n = 132 hips/n = 106 patients). Demographic and outcome measures were collected. Normalization was defined as alpha angle greater than or equal to 60° and femoral head coverage greater than or equal to 50%. Kaplan-Meier and Cox proportional hazards regression analyses modeled time to normalization and identified factors associated with earlier normalization. Median time to normalization was 7.0 weeks. At 12 weeks standard treatment, 85.8% [95% confidence interval (CI): 80.2-91.9%] had normalized. Greater femoral head coverage [hazard ratio (HR) per 1% increase: 1.03; 95% CI: 1.01-1.05; P = 0.0068] and hip stability at treatment initiation (HR unstable vs. stable: 0.64; 95% CI: 0.44-0.93; P = 0.0192) were associated with longer time to normalization. Some patients may not need 12 weeks of Pavlik bracing, particularly those with stable presentation who normalize before week 12. Shorter treatment lengths offer benefit without sacrificing long-term outcomes. Findings reinforce growing evidence that femoral head coverage should be a more significant consideration during diagnosis and instability is a concerning finding on examination.

Prolonged Brace Treatment Does Not Result in Improved Acetabular Indices in Infantile Dislocated Hips

BACKGROUND

The Pavlik harness (PH) is commonly used to treat infantile dislocated hips. However, significant variability exists in the duration of brace treatment after successful reduction of the dislocated hip. The purpose of this study was to evaluate the effect of prescribed time in brace on acetabular index (AI) at two years of age using a prospective, international, multicenter database.

METHODS

We retrospectively studied prospectively enrolled infants with at least 1 dislocated hip that were initially treated with a PH and had a recorded AI at 2-year follow-up. Subjects were treated at 1 of 2 institutions. Institution 1 used the PH until they observed normal radiographic acetabular development. Institution 2 followed a structured shorter brace treatment protocol. Hip dislocation was defined as <30% femoral head coverage at rest on the pretreatment ultrasound or International Hip Dysplasia Institute (IHDI) grade III or IV on the pretreatment radiograph.

RESULTS

Fifty-three hips met our inclusion criteria. Hips from Institution 1 were treated with a brace ×3 longer than hips from institution 2 (adjusted mean 8.9±1.3 vs. 2.6±0.2 mo) (P<0.001). Institution 1 had an 88% success rate and institution 2 had an 85% success rate at achieving hip reduction (P=0.735). At 2-year follow-up, we observed no significant difference in AI between Institution 1 (adjusted mean 25.6±0.9 degrees) compared with Institution 2 (adjusted mean 23.5±0.8 degrees) (P=0.1). However, 19% of patients from Institution 1 and 44% of patients from Institution 2 were at or below the 50th percentile of previously published age-matched and sex-matched AI normal data (P=0.049). Also, 27% (7/26) of hips from Institution 1 had significant acetabular dysplasia (more than 2 SD from the mean), compared with a 22% (6/27) from Institution 2 (P=0.691). We found no correlation between age at initiation of bracing and AI at 2-year follow-up (P=0.071).

CONCLUSIONS

The PH brace can successfully treat dislocated infant hips, however, prolonged brace treatment was not found to result in improved acetabular development at 2-year follow-up.

LEVEL OF EVIDENCE

Level III.

A Virtual Clinic for DDH Pavlik Harness Monitoring

BACKGROUND

Pavlik harness (PH) treatment is successful in treating over 90% of newborns with developmental dysplasia of the hip (DDH). There is a need for close supervision, frequent adjustments, size changes, and monitoring of complications. This paper aims to provide a safe criterion for remote follow-up of DDH patients treated in a PH to reduce the risk of COVID-19 (coronavirus disease 2019) exposure to patients, parents, and health practitioners.

METHODS

All infants with stable hips (Graf I, IIa/b/c/d, treated III/IV) with consenting parents after appropriate counseling were enrolled in a virtual clinic. Clinics were conducted using the NHS "Attend anywhere" virtual link service by an extended scope practitioner-specialist physiotherapist and a clinical nurse specialist. The virtual clinic group was compared with a matched cohort of patients from 2018/2019.

RESULTS

A total of 141 patients were referred to the neonatal hip clinic; 45 patients were eligible for harness treatment and 20 patients were selected for virtual clinics. In total, there were 35 virtual clinic appointments. Each of the patients had an average of 1.7 virtual appointments ranging from 1 to 3 (26.3% of total number of clinics). Age at presentation of the treated group was 7±4.2 weeks and control group 5.7±5.5 weeks (P=0.59). PH duration of the study group was 9±2.6 weeks and the control group, 7.8±2.5 weeks (P=0.12). There were no missed complications at the follow-up face-to-face appointment. Patients saved an average of 76 km total travel distance.

CONCLUSIONS

This study demonstrates adequate evidence that children requiring routine follow-up appointments involving PH adjustment, skincare, and identification of clinical anomalies, can be treated and followed up safely using virtual clinics. Clinical triage of suitable patients for virtual clinic provision must always be made by experienced clinicians. Children presenting with Graf IIa, IIb, IIc, IId, as well as those with stable and improving Graf III at initial diagnoses, had successful treatment with virtual clinic follow-up appointments in this study.

LEVEL OF EVIDENCE

Level IV.

Comparing Hip Dysplasia in Dogs and Humans: A Review

Hip dysplasia (HD) is common in both humans and dogs. This interconnection is because humans and dogs descended from a common ancestor and therefore have a similar anatomy at micro- and macroscopic levels. Furthermore, dogs are the animals of choice for testing new treatments for human hip dysplasia and orthopedic surgery in general. However, little literature exists comparing HD between the two species. Therefore, the aim of this review is to describe the anatomy, etiology, pathogenesis, diagnostics, and treatment of HD in humans and dogs. HD as an orthopedic condition has many common characteristics in terms of etiology and pathogenesis and most of the differences can be explained by the evolutionary differences between dogs and humans. Likewise, the treatment of HD shows many commonalities between humans and dogs. Conservative treatment and surgical interventions such as femoral osteotomy, pelvic osteotomy and total hip arthroplasty are very similar between humans and dogs. Therefore, future integration of knowledge and experiences for HD between dogs and humans could be beneficial for both species.

The nomogram predicting the early failure rate of the Pavlik harness for developmental dysplasia of the hip in infants under 6 months of age

BACKGROUND

The aim of our study was to develop a nomogram predicting the early failure rate of Pavlik harness in infants under 6 months of age with developmental dysplasia of the hip (DDH).

METHODS

We retrospectively analyzed the clinical data of 227 patients (372 hips) with DDH who were treated with Pavlik harness at our institution from August 2019 to January 2022. Fifty-eight patients (102 hips) failed the Pavlik harness treatment, and 169 patients (270 hips) were successfully treated. Then, the independent risk factors for treatment failure were determined via univariate and multivariate logistic regression and used to generate the nomogram predicting the failure rate of the Pavlik harness.

RESULTS

It was found that age at initial treatment (OR 1.031, 95% CI 1.022-1.040, P < 0.001), angle α (OR 0.723, 95% CI 0.671-0.779, P < 0.001), and concomitant deformity (OR 0.129, 95% CI 0.036-0.459, p = 0.002) were independent risk factors for treatment failure. The nomogram showed good discrimination [the area under the curve (AUC): 0.862], good calibration, and a net benefit in the range of probabilities between 5 and 90% according to the decision curve analysis.

CONCLUSION

This study successfully established the nomogram prediction model based on three independent risk factors. Due to the high level of predicting accuracy, this nomogram could be a useful resource for pediatric orthopedic surgeons to identify patients at major risk of Pavlik harness failure who might need more reliable treatments.

Principles of Bracing in the Early Management of Developmental Dysplasia of the Hip

Bracing is considered a gold standard in treating Developmental Dysplasia of the Hip (DDH) in infants under 6 months of age with reducible hips. A variety of braces are available that work on similar principles of limiting hip adduction and extension. This paper summarises the current evidence regarding bracing in DDH. Most of the literature pertains to the Pavlik harness (PH) and there are few studies for other brace types. Bracing eliminates dislocating forces from the hamstrings, the block to reduction of the psoas and improves the muscle line of pull to stabilise the hip joint. Recent studies have shown no benefit in bracing for stable dysplasia. The rates of PH treatment failure in Ortolani-positive hips have been reported to be high. Barlow positive hips have lower Graf grades and are more amenable to PH treatment. There is consensus that the earlier the diagnosis of DDH and initiation of PH treatment, the better the outcome. Failure rates due to unsuccessful reduction and AVN are higher with treatment initiated after age 4-6 months. Studies have shown no benefits of staged weaning of braces. While there is no maximum time in brace, current consensus suggests a minimum of 6 weeks. The key to successful bracing lies in education and communication with the family.

What Are the Rate and Risk Factors for Developing a Complication With the Pavlik Method for the Treatment of Hip Dysplasia?

BACKGROUND

The Pavlik method for the treatment of developmental dysplasia of the hip (DDH) has been proven successful for over 85 years. The high success rate and reproducibility have made it the mainstay of treatment.

METHODS

We performed a retrospective cohort study of patients with DDH treated with the Pavlik method between September 2016 and August 2018 with at least 24 months of follow up in a single academic center. We excluded patients with neuromuscular conditions, teratologic dislocations, and arthrogryposis. We identified and included a total of 307 patients in the analysis. There were 66 patients with dysplasia, 97 with instability, and 144 with a dislocation. Data collected included age at initiation of the Pavlik method, diagnosis (isolated dysplasia, subluxation, or dislocation), duration of treatment, follow up duration and any complication. At final follow up, anteroposterior radiographs of the pelvis were used to determine the Severin classification.

RESULTS

Major complications were proximal femoral growth disturbance (5.8%) and femoral nerve palsy (0.98%). Multivariate analysis showed that an initial diagnosis of a dislocated hip (odds ratio, 2.20; P<0.01), was significantly associated with developing a complication. At final follow up, we found Severin type I or II radiographic findings in 100% of patients with dysplasia, 95% of patients with instability and 54% of patients with dislocation (P=0.001).

CONCLUSIONS

Complications are not entirely uncommon when the Pavlik method is used for the treatment of DDH. The overall rate of major complications was 7%. The Pavlik method is safe, and independent risk factors for complications were being over 5 months of age and having a dislocated hip at initial presentation.

LEVEL OF EVIDENCE

Level IV-cohort study.

Tübingen hip flexion splint for the treatment of developmental dysplasia of the hip in children younger than six months age: a meta-analysis

PURPOSE

To investigate the success rate of the Tübingen hip flexion splint (THFS) for the treatment of developmental dysplasia of the hip (DDH), of different severity as per the Graf classification, among infants younger than six months of age. The type and incidence rate of complications associated with THFS treatment were also evaluated.

METHODS

The following databases were searched using keywords and limited for age less than six months: PubMed, Embase, Web of Science, Cochrane Library, and SinoMed, between inception and July 2020. Articles were screened and extracted by two researchers, and the quality of the included literature was evaluated (methodological index for non-randomized studies criteria). R studio 1.3 was used for statistical analysis. The review process was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

After screening, eight articles were included in the analysis, contributing 1211 hips (875 patients). The overall success rate of THFS treatment is 91% (95% confidence interval (CI) 0.82 to 0.95). The success rate by Graf type is as follows: type-II, 98% (95% CI 0.94 to 1.00); type-III, 96% (95% CI 0.88 to 1.00); and type-IV, 32% (95% CI 0.18 to 0.47). Complications (24/1211, 2%) included transient femoral nerve palsy (n = 1); avascular necrosis of the femoral head (n = 9) and residual acetabular dysplasia (n = 14).

CONCLUSION

THFS treatment is successful for Graf type-II and -III, but low for type-IV, with a low rate of complication. THFS may be an effective treatment option for DDH among infants less than six months of age. However, those with Graf type-IV require close monitoring.

LEVEL OF EVIDENCE

III.

Team Approach: Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH) encompasses a wide spectrum of hip disorders, including neonatal instability, acetabular dysplasia, hip subluxation, and frank dislocation of the hip. It is a common disorder, with a reported incidence of between 0.1% and >10% of live births. Coordinated, interdisciplinary care is important to achieving successful outcomes. This starts with accurate assessment of risk factors in the prenatal period, thorough clinical examination by the primary care provider at all well-child visits, and early referral to a pediatric orthopaedic surgeon for prompt diagnosis and treatment. Early diagnosis and prompt treatment is critical for an excellent outcome. Ongoing, open communication between clinicians is essential for the effective coordination of care. Treatment options vary depending on the age of presentation. A Pavlik harness (dynamic hip abduction orthosis) is used for children up to 6 months of age. A more rigid abduction orthosis may be used if treatment with a Pavlik harness is unsuccessful, with a closed reduction and spica cast being the next step if needed for children up to 18 months of age. Finally, open reduction with possible concomitant femoral and/or pelvic osteotomies is the surgical option in an older child, when necessary. In general, the later the child is diagnosed with and treated for DDH, the greater the risk of a nonoptimal outcome. Depending on the severity of the condition, children with DDH may need to be followed closely until skeletal maturity so as not to miss the diagnosis of asymptomatic residual hip dysplasia, which can predispose patients to early hip arthritis.

Current Evidence about Developmental Dysplasia of the Hip in Pregnancy

In adults, developmental dysplasia of the hip (DDH) represents a spectrum of disorders. It is commonly found in women in routine orthopedic practice. Hip dysplasia is a leading precursor of joint laxity; when untreated, it can contribute to chronic modifications, such as thickening of the pulvinar and ligamentum teres (which can also elongate), hypertrophy of the transverse acetabular ligament, and osteoarthritis. DDH is presumed to be associated with alterations in pelvic morphology that may affect vaginal birth by the reduction in the transverse diameter of the pelvic inlet or outlet. Here, we provide an overview of the current knowledge of pregnancy-associated DDH. We primarily focused on how a surgical DDH treatment might influence the pelvic shape and size and the effects on the mechanism of birth. We presented the female pelvis from the standpoint of bone and ligament morphology relative to a pelvic osteotomy. Then, we described whether the pregnancy was impacted by previous surgical DDH treatments, performed from infancy to adulthood. In conclusion, hip dysplasia is not associated with high-risk complications during pregnancy or with increased difficulty in vaginal delivery.

Comparison between the Pavlik harness and the Tübingen hip flexion splint for the early treatment of developmental dysplasia of the hip

The Pavlik harness and the Tübingen hip flexion splint (Tübingen hip flexion splint) are two effective options for the early management of patients younger than 6 months of age with developmental dysplasia of the hip (DDH). The main objective of this study was to evaluate the clinical and radiological outcomes of patients younger than 6 months of age with type IIb to IV DDH managed by Pavlik harness or Tübingen hip flexion splint. The Pavlik harness and Tübingen hip flexion splint groups were comparable regarding the affected side (P = 0.09), Graf grade (P = 0.635), and age at initial treatment (P = 0.77). Overall, failure rates were 12 and 33% in Pavlik harness (4/33 hips) and Tübingen hip flexion splint groups (14/43 hips), respectively (P = 0.038). No cases of avascular necrosis (AVN) were found in either group. In the Tübingen hip flexion splint group, the failure rate was significantly higher in bilateral cases (66.6%; P = 0.004), in severe forms (Graf grade IV hips; P ≤ 0.0001), and in patients with lower age at initial treatment (67.7 ± 39.3 days; P = 0.005). The average follow-up time was 30.35 ± 3.58 months (range: 24-36). At the last follow-up visit, no statistically significant differences were found between the Pavlik harness and Tübingen hip flexion splint groups regarding the acetabular index (t = 0.632; P = 0.53) or center-edge angle (Z = -0.303; P = 0.762). Our study showed that both the brace treatments for DDH in children younger than 6 months of age were effective and well tolerated. However, Tübingen hip flexion splint should not be used in patients with severe forms of DDH (Graf grade IV hips).

Tübingen hip flexion splints for developmental dysplasia of the hip in infants aged 0-6 months

Background

Developmental dysplasia of the hip (DDH) is a common disorder in infants. The present study aimed to evaluate the efficacy and safety of the Tübingen hip flexion splints in treating DDH in infants aged 0–6 months.

Methods

This is a retrospective study analyzing 259 hips in 195 infants with DDH of Graf type IIc or worse classifications treated between January 2015 and December 2017. Patients were followed up for at least 6 months. Avascular necrosis of the femoral head was diagnosed using plain radiographs at the last follow-up visit according to the Bucholz-Ogden classification. Successful treatment was defined as an improvement of the Graft classification to type I, or an improvement of the International Hip Dysplasia Institute classification to type I in patients aged > 6 months.

Results

Treatment was deemed successful in 128 patients (83.7%). Avascular necrosis occurred in 3 patients (3 hips). Univariate analysis showed that late treatment initiation, family history of DDH, Graf type IV and bilateral involvement were independent risk factors for treatment failure (p < 0.05). The receiver operating characteristic curve showed a cut-off value of 12 weeks for age at treatment initiation regarding successful treatment. Logistic regression analysis showed that gender, breech presentation, firstborn, swaddling, birth weight > 3.5 kg, oligohydramnios, foot deformity and torticollis did not affect the success rate of treatment (p > 0.05).

Conclusions

The Tübingen splint showed good efficacy and safety in treating DDH in infants aged 0–6 months. Family history of DDH, Graf classification of type IV, bilateral involvement and treatment initiation after 12 weeks of age are risk factors of treatment failure.

Trial registration

N/A

Comparison of Pavlik Harness treatment regimens for reduced but dislocatable (Barlow positive) hips in infantile DDH

Objective

Although the Pavlik Harness (PH) is the most utilized treatment for developmental dysplasia of the hip (DDH), the ideal treatment protocol (frequency of clinic visits in the first month and daily wear duration) for Barlow ​+ ​hips (reduced but dislocatable) has yet to be defined.

Methods

This study compared DDH patients with Barlow hips who were treated with 23 vs 24 h per day PH wear and weekly vs every other week visits. Clinical success was defined as a stable hip that did not require closed or open reduction, or the use of an abduction orthosis prior to achieving clinical stability. Radiographic success was based on the acetabular index at 2-year follow up.

Results

Sixty-five patients (75 hips/58 females) with Barlow hips had a mean age of presentation of 15 ± 12 days (range 4-70) and mean follow-up of 33 ± 17 months (range 6-90). There was no difference in clinical or radiographic success rate between 23 h vs 24 h wear groups (p > 0.99 both) or the Frequently vs Infrequent visit groups (p = 0.49 both). Overall clinical success rate was 97% (73/75 hips) and radiographic success rate at 2 years was 97% (58/60 hips).

Conclusion

A strict, weekly clinic visit and 24-h PH regimen may not be necessary to obtain good clinical and radiographic outcomes in infants presenting <6 months of age with Barlow positive hips.

Level of evidence

Therapeutic, Level III.

Developmental dysplasia of the hip: addressing evidence gaps with a multicentre prospective international study

There is a lack of high quality evidence available to guide clinical practice in the treatment and management of developmental dysplasia of the hip (DDH). Evidence has been limited by persistent confusion on diagnostic and classification terminology, variability in surgeon decision making and a reliance on single centre, retrospective studies with small patient numbers. To address gaps in knowledge regarding screening, diagnosis and management of DDH, the International Hip Dysplasia Institute began a multicentre, international prospective study on infants with hips dislocated at rest. This review discusses the current state of screening, diagnostic and management practices in DDH and addresses important unanswered questions that will be critical in identifying best practices and optimising patient outcomes. There is insufficient evidence to support universal ultrasound screening; instead, selective screening should be performed by 6-8 weeks of age on infants with risk factors of breech presentation, family history, or history of clinical hip instability. Follow-up of infants with risk factors and normal initial screening should be considered to at least 6 months of age. Brace treatment is a sensible first-line treatment for management of dislocated hips at rest in infants < 6 months of age. Early operative reduction may be considered as there is insufficient evidence to support a protective role for the ossific nucleus in the development of avascular necrosis.

Associations between risk factors and developmental dysplasia of the hip and ultrasonographic hip type: a retrospective case control study

PURPOSE

We aimed to revisit the correlation between the previously defined risk factors and the occurrence of developmental dysplasia of the hip (DDH) and to assess the influence of these factors on the ultrasonographic type of hip dysplasia according to the Graf's classification in patients with DDH.

METHODS

Data of healthy infants (mean age 33 days) who had bilateral mature (normal) hips (Graf type I) were compared with the data of infants (mean age 105 days) who were treated by abduction brace due to unilateral or bilateral DDH (Graf type IIa- and worse hips).

RESULTS

Infants with at least one risk factor had a significantly higher rate of DDH than those with no risk factors (p < 0.001). Likewise, infants with more than one risk factor had a significantly higher rate of DDH than those with only one risk factor (p = 0.008). Family history, breech presentation and swaddling were found to be the three significant risk factors related to the development of DDH. Family history, swaddling and oligohydramnios were found to be the three significant risk factors correlated with a higher rate of unstable/decentred hip(s) (Graf types D/III/IV) in patients with DDH.

CONCLUSION

The risk of DDH significantly increases in infants who have more than one risk factor for DDH. Positive family history and postnatal traditional swaddling are the two main factors both in the aetiology of DDH and in development of a more severe hip dysplasia in patients with DDH. Besides, breech presentation increases the risk of development of DDH and oligohydramnios leads to development of a more severe hip dysplasia in patients with DDH. By introducing these four variables as 'absolute risk factors for DDH' to the selective newborn hip screening programmes, the sensitivity and specificity of these programmes may be optimized and the risk of delayed diagnosis may be lessened.

LEVEL OF EVIDENCE

Level III prognostic study.

Treatment of developmental dysplasia of the hip with the Pavlik harness in children under six months of age: indications, results and failures

PURPOSE

The aim of this article is to review the current concepts in the indications, results and failure causes of the treatment of developmental dysplasia of the hip (DDH) with the Pavlik harness.

METHODS

The reported variables influencing the outcome in the Pavlik harness treatment were analyzed.

RESULTS

Significant discrepancies about the clinical and radiological outcomes, the rates of failure and complications as well as the variables influencing the treatment outcome occur in the published studies due to the heterogeneity of the data and the differences in the methods used. The overall short-, mid- or long-term success rate of the treatment ranges from 45% to 100% and it is commonly over 75%. The rate of osteonecrosis of the femoral head ranges from 1% to 30%. Age, gender, laterality, radiological or clinical severity of the initial hip pathology and parents' compliance are the commonly reported determinants of failure of the treatment.

CONCLUSION

The failure in treatment with the Pavlik harness is multifactorial, initial type of hip dysplasia being the most prominent followed by the treatment initiation age. This type of treatment cannot be considered as the best option in Graf IV hips (hip ultrasonography) or highly dislocated hips (plain radiography) and in infants older than three months of age, as the risk of failure and development of complications including osteonecrosis and femoral nerve palsy seem to increase in such circumstances. Large-scale, comparative studies including homogenous data are needed to answer the unsolved questions concerning indications.

An analysis of variables affecting the duration of Pavlik harness treatment: Is it possible to predict the duration of treatment?

BACKGROUND

Pavlik harness is the initial treatment for the infants with developmental dysplasia of the hip who have not yet begun walking.

OBJECTIVES

The present study evaluates the variables which affect the duration of PH treatment for patients successfully treated.

STUDY DESIGN

Cross-sectional study.

METHODS

Pavlik harness was employed for 140 hips of 87 patients with developmental dysplasia of the hip in our institution between 2010 and 2013. In all, 55 hips of 46 patients who were treated successfully with Pavlik harness were included in this study. According to Graf's sonographic classification, 23 hips were Type IIC, 26 were Type IID, and 6 were Type III. The studied variables were (1) alpha angle, (2) age at the start of treatment, (3) laterality, and (4) gender. The variables were compared with the duration of Pavlik harness treatment.

RESULTS

A highly significant inverse correlation was observed between Pavlik harness application time and alpha angle at the start of the treatment ( r = -0.050; p < 0.001). Bilateral involvement has statistically longer duration, when compared with unilateral involvement ( r = 0.28; p = 0.036). No statistically significant difference was present between duration of treatment and age at the start of Pavlik harness treatment ( r = -0.034; p = 0.804). There was no statistical significance between gender and duration of Pavlik harness ( r = 0.201; p > 0.05).

CONCLUSION

The duration of treatment was negatively correlated with the initial alpha angle. A change of 1 degree in alpha angle may alter the duration of treatment as 0.89 week calculated by the formula (Application time (Week) = 56.6 - 0.89 × alpha angle). Bilateral involvement may need longer Pavlik harness treatment. Clinical relevance Pavlik harnes generally is the first treatment method for the infants with DDH. This study suggest conclutions about how long time is the Pavlik harness should be kept on the infants? The main indicator is initial alfa angle which is negatively correlated with the duration of treatment.

Developmental dysplasia of the hip: an update on diagnosis and management from birth to 6 months

PURPOSE OF REVIEW

Our understanding of the epidemiology, diagnosis, and management of developmental dysplasia of the hip (DDH) is evolving. This review focuses on the most up-to-date literature on DDH in patients from birth to six months of age.

RECENT FINDINGS

Well known risk factors for DDH include family history, female sex, and breech positioning. Recent evidence suggests higher birth weight is a risk, whereas prematurity may be protective. Screening includes physical examination of all infant hips and imaging when abnormal findings or risk factors are present. Treatment in the first six months consists of a harness, with 70-95% success. Failure risk factors include femoral nerve palsy, static bracing, irreducible hips, initiation after seven weeks of age, right hip dislocation, Graf-IV hips, and male sex. Rigid bracing may be trialed if reduction with a harness fails and closed reduction is indicated after failed bracing. If the hip is still irreducible, nonconcentric, or unstable, open reduction may be required following closed reduction. Evidence does not support delaying hip reduction until the ossific nucleus is present.

SUMMARY

DDH affects 1-7% of infants. All infants should be examined and selective screening with imaging should be performed for abnormal physical exams or risk factors. Early treatment is associated with optimal outcomes.

Evaluation of Brace Treatment for Infant Hip Dislocation in a Prospective Cohort: Defining the Success Rate and Variables Associated with Failure

BACKGROUND

The use of a brace has been shown to be an effective treatment for hip dislocation in infants; however, previous studies of such treatment have been single-center or retrospective. The purpose of the current study was to evaluate the success rate for brace use in the treatment of infant hip dislocation in an international, multicenter, prospective cohort, and to identify the variables associated with brace failure.

METHODS

All dislocations were verified with use of ultrasound or radiography prior to the initiation of treatment, and patients were followed prospectively for a minimum of 18 months. Successful treatment was defined as the use of a brace that resulted in a clinically and radiographically reduced hip, without surgical intervention. The Mann-Whitney test, chi-square analysis, and Fisher exact test were used to identify risk factors for brace failure. A multivariate logistic regression model was used to determine the probability of brace failure according to the risk factors identified.

RESULTS

Brace treatment was successful in 162 (79%) of the 204 dislocated hips in this series. Six variables were found to be significant risk factors for failure: developing femoral nerve palsy during brace treatment (p = 0.001), treatment with a static brace (p < 0.001), an initially irreducible hip (p < 0.001), treatment initiated after the age of 7 weeks (p = 0.005), a right hip dislocation (p = 0.006), and a Graf-IV hip (p = 0.02). Hips with no risk factors had a 3% probability of failure, whereas hips with 4 or 5 risk factors had a 100% probability of failure.

CONCLUSIONS

These data provide valuable information for patient families and their providers regarding the important variables that influence successful brace treatment for dislocated hips in infants.

LEVEL OF EVIDENCE

Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Skill Acquisition and Retention Following Simulation-Based Training in Pavlik Harness Application

BACKGROUND

Simulation-based learning is increasingly prevalent in many surgical training programs, as medical education moves toward competency-based curricula. In orthopaedic surgery, developmental dysplasia of the hip is a commonly treated condition, where the standard of care for patients less than six months of age is an orthotic device such as the Pavlik harness. However, despite widespread use of the Pavlik harness and the potential complications that may arise from inappropriate application, we know of no previously described formal training curriculum for Pavlik harness application.

METHODS

We developed a video and model-based simulation learning module for Pavlik harness application. Two novice groups (residents and allied health professionals) were exposed to the module and, at pre-intervention, post-intervention, and retention testing, were evaluated on their ability to apply a Pavlik harness to the model. Evaluations were completed using a previously validated Objective Structured Assessment of Technical Skills (OSATS) and a global rating scale (GRS) specific to Pavlik harness application. A control group that did not undergo the module was also evaluated at two time points to determine if exposure to the Pavlik harness alone would affect skill acquisition. All groups were compared with a group of clinical experts, whose scores were used as a competency benchmark. Statistical analysis of skill acquisition and retention was conducted using t tests and analysis of variance (ANOVA).

RESULTS

Exposure to the learning module improved resident and allied health professionals' competency in applying a Pavlik harness (p < 0.05) to the level of the expert clinicians, and this level of competency was retained one month after exposure to the module. Control subjects who were not exposed to the module did not improve, nor did they achieve competency.

CONCLUSIONS

The simulation-based learning module was shown to be an effective tool for teaching the application of a Pavlik harness, and learners demonstrated retainable skills post-intervention. This learning module can form the cornerstone of formal teaching of Pavlik harness application for developmental dysplasia of the hip.

What Is the Impact of Center Variability in a Multicenter International Prospective Observational Study on Developmental Dysplasia of the Hip?

BACKGROUND

Little information exists concerning the variability of presentation and differences in treatment methods for developmental dysplasia of the hip (DDH) in children < 18 months. The inherent advantages of prospective multicenter studies are well documented, but data from different centers may differ in terms of important variables such as patient demographics, diagnoses, and treatment or management decisions. The purpose of this study was to determine whether there is a difference in baseline data among the nine centers in five countries affiliated with the International Hip Dysplasia Institute to establish the need to consider the center as a key variable in multicenter studies.

QUESTIONS/PURPOSES

(1) How do patient demographics differ across participating centers at presentation? (2) How do patient diagnoses (severity and laterality) differ across centers? (3) How do initial treatment approaches differ across participating centers?

METHODS

A multicenter prospective hip dysplasia study database was analyzed from 2010 to April 2015. Patients younger than 6 months of age at diagnosis were included if at least one hip was completely dislocated, whereas patients between 6 and 18 months of age at diagnosis were included with any form of DDH. Participating centers (academic, urban, tertiary care hospitals) span five countries across three continents. Baseline data (patient demographics, diagnosis, swaddling history, baseline International Hip Dysplasia Institute classification, and initial treatment) were compared among all nine centers. A total of 496 patients were enrolled with site enrolment ranging from 10 to 117. The proportion of eligible patients who were enrolled and followed at the nine participating centers was 98%. Patient enrollment rates were similar across all sites, and data collection/completeness for relevant variables at initial presentation was comparable.

RESULTS

In total, 83% of all patients were female (410 of 496), and the median age at presentation was 2.2 months (range, 0-18 months). Breech presentation occurred more often in younger (< 6 months) than in older (6-18 months at diagnosis) patients (30% [96 of 318] versus 9% [15 of 161]; odds ratio [OR], 4.2; 95% confidence interval [CI], 2.3-7.5; p < 0.001). The Australia site was underrepresented in breech presentation in comparison to the other centers (8% [five of 66] versus 23% [111 of 479]; OR, 0.3, 95% CI, 0.1-0.7; p = 0.034). The largest diagnostic category was < 6 months, dislocated reducible (51% [253 of 496 patients]); however, the Australia and Boston sites had more irreducible dislocations compared with the other sites (ORs, 2.1 and 1.9; 95% CIs, 1.2-3.6 and 1.1-3.4; p = 0.02 and 0.015, respectively). Bilaterality was seen less often in older compared with younger patients (8% [seven of 93] versus 26% [85 of 328]; p < 0.001). The most common diagnostic group was Grade 3 (by International Hip Dysplasia Institute classification), which included 58% (51 of 88) of all classified dislocated hips. Splintage was the primary initial treatment of choice at 80% (395 of 496), but was far more likely in younger compared with older patients (94% [309 of 328] versus 18% [17 of 93]; p < 0.001).

CONCLUSIONS

With the lack of strong prognostic indicators for DDH identified to date, the center is an important variable to include as a potential predictor of treatment success or failure.

Hip Click in the Neonate: Should I Be Concerned?

Developmental dysplasia of the hip (DDH) requires precise evaluation and rapid treatment/referral to specialists to optimize results. The incidence of DDH ranges between 4/1,000 and 133/1,000 newborns depending on patient risk factors (female gender, breech birth, and family history). Multiple associations have been identified including metatarsus adductus, oligohydramnios, and muscular torticollis. Classic physical examination results are well known by pediatricians, but can be difficult to elicit. Ultrasound screening is a useful test in defining early dysplasia and dislocation, but can generate misleading results if used inappropriately. Early ultrasound is useful for the identification of unstable hips and discerning treatment. High rates of ultrasound abnormalities have been identified in the early neonatal period, most of which have been shown to spontaneously improve. Ortolani/Barlow negative hips are best evaluated at age 6 weeks if continued concern is present. Treatment with the Pavlik harness or an abduction splint is well known to have excellent outcomes, but not without risk.

Retrospective analysis of the radiographic indicators for peri-acetabular osteotomy of developmental dysplasia in children

PURPOSE

Open surgery, nonsurgical positioning device and casting are mainstay treatments of developmental dysplasia of the hip (DDH). The optimal indicators for surgical interventions remain unclear. In this study, we aim to establish empirical, sensitive radiographic indicators for peri-acetabular osteotomy intervention in developmental dysplasia in Chinese children.

METHODS

One hundred and three DDH patients treated in The Soochow University Children's Hospital between 2006 and 2012 were assessed; patients with known causes of neuron muscular and abnormal hip joint origin were excluded. Fifty-four suitable patients, demonstrating 71 dysplasia hips with complete clinical record and adequate X-ray films, were enrolled in this study. Patients were divided into group A (conservative interventions failed, followed by salvage peri-acetabular osteotomy) and group B (conservative treatment only); a total of 16 quantitative parameters were measured on each pelvic X-ray film.

RESULTS

Among 71 hip joints measured, 29 hips of group A underwent salvage peri-acetabular osteotomy (40.8 %,) showed higher X2, Y, h, and Smith c/b (Vh) (p < 0.05). The age, c, HT, b, A2 in the group A salvage operation were statistically significantly different compared to group B patients (without salvage operations) (p < 0.05).

CONCLUSIONS

Pre-operative pelvic X-ray film assessment of acetabulum lateralization markers (X2, c, HT, c/b ratio) and the superior migration measurements (Y, h, h/b ratio) are potentially valuable radiographic indicators for determining which DDH patients will require peri-acetabular osteotomy.

The efficacy of semirigid hip orthosis in the delayed treatment of developmental dysplasia of the hip

This study assessed the use of semirigid hip orthosis to stabilize the femoral head into the acetabulum in the delayed treatment of developmental dysplasia of the hip (DDH; Graf type IIb or more severe) under the age of 6 months. Ninety-eight hips from 75 patients (four boys, 71 girls) were evaluated retrospectively. The mean age at treatment initiation was 3.2±1.3 months (1-6 months). As the dysplastic hip matured into a type I hip, we applied the weaning regimen for 1 month. Seventy-two patients (96%) were treated successfully in 4.2±1.1 months (2-8 months). All of the failures were type IV hips. We did not detect any acetabular or femoral head pathology in the later follow-up. Semirigid hip orthosis is safe and effective as the first-line treatment method for delayed DDH except in type IV hips in patients under 6 months of age.

LEVEL OF EVIDENCE

Level IV. Case series.

Developmental dysplasia of the hip in neonates: evolution of acetabular dysplasia after hip stabilization by brief Pavlik harness treatment

BACKGROUND

The recommended treatment duration in neonates with developmental dysplasia of the hip (DDH) varies depending on whether prolonged Pavlik harness therapy is believed to favourably affect the course of the acetabular dysplasia. According to one theory, several months of additional Pavlik harness therapy after achieving hip reduction contributes to correct the acetabular dysplasia. Another theory holds that hip dislocation induces the acetabular dysplasia, which corrects spontaneously once the femoral head is properly seated in the acetabulum. Here, we evaluated this second theory by studying outcomes after early brief Pavlik harness therapy.

HYPOTHESIS

Acetabular dysplasia associated with neonatal hip instability undergoes self-correction provided stable hip reduction is achieved very early after birth. Therefore, the duration of Pavlik harness therapy can be substantially shortened.

MATERIALS AND METHODS

We defined hip instability as either reducible hip dislocation or a very easily dislocatable hip with a soft clunk precluding determination of spontaneous hip position as dislocated or reduced. Static and dynamic ultrasound scans were obtained. Patients with ultrasonographic instability (pubo-femoral distance>5mm with less than 50% of coverage) underwent a second physical examination and received treatment. We re-evaluated 42 abnormal hips in 30 patients after a mean follow-up of 6.7 years (range, 5-14 years). Mean age at treatment initiation was 5 days (range, 1-15 days) and mean treatment duration was 34 days (range, 15-75 days).

RESULTS

Mean acetabular angle was 20° (range, 12°-30°) and mean Wiberg's lateral centre-edge angle was 30° (range, 22°-35°). Blunting of the lateral angle of the bony roof was noted in 8 hips at last follow-up. In 1 patient whose hip was stable clinically but unstable by ultrasonography at 21 days of age, recurrent dislocation occurred at 5 months of age. The Severin class was 1a in all patients.

DISCUSSION

Despite continuing controversy about whether hip dislocation induces dysplasia or vice versa, the need for early treatment is universally recognised. The optimal treatment duration, however, remains debated. Proponents of the familial determinism of DDH consider that acetabular shaping is genetically programmed when the femoral head is centred in the acetabular socket. Others advocate routine prolongation of Pavlik harness therapy for 2 months or longer, based on the opinion that this strategy decreases the dislocation recurrence rate and that mechanical hip unloading may promote correction of the dysplasia. Mean treatment duration in our population was 34 days and our sole objective was to treat the instability. The hip was reduced and held in its proper position long enough to allow sufficient capsule and ligament tightening to stabilise the hip. Under these conditions, the acetabular dysplasia underwent self-correction that was not related to treatment duration.

CONCLUSION

Very early Pavlik harness therapy to ensure rapid hip reduction and stabilisation optimises the potential of the acetabulum for spontaneous remodelling.

LEVEL OF EVIDENCE

Level IV, retrospective study.