Chiari pelvic osteotomy for osteoarthritis secondary to hip dysplasia. Indications and long-term results

Ultra-long-term results of the Chiari pelvic osteotomy in hip dysplasia patients: a minimum of thirty-five years follow-up

PURPOSE

The Chiari pelvic osteotomy was the first surgical procedure to address hip dysplasia by changing the position of the acetabulum by medialization, thus creating a bony roof and improving biomechanical conditions. The aim of this retrospective cohort study was to report on the very long-term results of this technique.

METHODS

Out of a consecutive series of 1536 hips, 504 in 405 patients were available for follow-up. The patients were assessed by physical and radiological examination. A Kaplan-Meier survival analysis with total hip arthroplasty as an endpoint was performed and stratified for age groups, pre-operative diagnosis, sex and osteoarthritis stage.

RESULTS

The average follow-up was 36 ± 8.1 years (range, 35.2 to 54). The average pain level on the Visual Analogue Scale was 2.9 ± 2.6 (range 0 to 8.7). The average Harris Hip Score was 80.2 ± 17.4 (range 17.4 to 100). Correction of dysplasia was effective and remained stable over time. Osteoarthritis significantly increased over time with 53% Tönnis grade 3 at follow-up. The cumulative survivorship was 79.8% (95% confidence interval (CI), 76.1-83.2%) at 20 years, 57.1% (95% CI, 52.8-61.8%) at 30 years and 35% (95% CI, 30.3-40.3%) at 40 years. Young age, male sex and low osteoarthritis grade were positive prognostic factors.

CONCLUSIONS

Although the Chiari pelvic osteotomy is considered a salvage procedure nowadays, it achieved excellent long-term results even in indications, which would be treated differently today. Young patients without osteoarthritis had the best outcome.

Long-Term Results after Chiari Pelvic Osteotomy in the Skeletally Immature and the Role of the Anti-Chiari Effect

Several authors observed a loss of correction after performing Chiari pelvic osteotomy (CPO) in young patients. Hence, the aim of this study was to answer two questions: (1) Does the Chiari pelvic osteotomy affect the development of the acetabulum in skeletally immature patients in the long term? (2) Is there any evidence of the previously described "Anti-Chiari" effect after a mean follow-up of 36 years? Data from 21 patients (27 hips) undergoing CPO before the age of 16 years were clinically assessed, and the evolution of radiological parameters over time was analyzed. The mean age at CPO was 11.2 years (±3; 4.4-15.7). The 20- and 30-year survival rates of the CPO were 100% and 92.6%, respectively. Mean postoperative medialization was 54% (±18; 23-99). The average osteotomy angle was 11° (±7; 2-28). No significant changes were found for the center-edge angle (CEA) and acetabular index (AI) over time; the angle of Idelberger and Frank (ACM) almost reached normal values at follow-up (FU); for the acetabular-head index (AHI), a slight shift toward the initial situation could be detected. The morphology of the acetabulum remained unchanged over time. The "Anti-Chiari effect" seems to be primarily caused by insufficient coverage of the femoral head rather than damage to the apophysis due to surgery.

Long-term clinical and radiological outcome in patients with severe Legg-Calvé-Perthes disease after Chiari pelvic osteotomy: a mean of 14 years follow-up

INTRODUCTION

The Chiari pelvic osteotomy (CPO) has been recommended as a salvage procedure to improve head coverage in case of hip joint incongruence in paediatric hip disease. In this study, we aimed to assess the long-term results of CPO for severe Legg-Calvé-Perthes disease (LCPD).

METHODS

A total of 39 patients who underwent a CPO at our department between 1995 and 2010 were prospectively followed both radiologically (Stulberg classification) and clinically (Harris Hip Score [HHS], conversion into total hip arthroplasty). In this study, we retrospectively reviewed the cases of 12 hips (12 patients, 3 girls, 8 left hips) treated by CPO for severe LCPD (Catterall grade 3 or 4) with hip joint incongruence. Mean follow-up was 14.0 (range 7.6-21.3) years.

RESULTS

Mean age at surgery was 10.2 (range 8.2-17.8) years. Additional femoral osteotomy was performed in 8 patients. A good radiological result (Stulberg I or II) was achieved in 2 patients, a fair result (Stulberg III) in 4 patients, and a poor outcome (Stulberg IV or V) in 6 patients. Mean postoperative HHS averaged 93 (range 65-100) points. An excellent functional outcome (HHS 90-100 points) was achieved in 9 patients. No patient underwent total hip arthroplasty during follow-up. Postoperative limb-length discrepancy was found in 3 patients.

CONCLUSIONS

CPO for severe LCPD with hip joint incongruence resulted in good long-term clinical outcome in about ⅔ of our patients after a mean of 14 years. Our results suggest that CPO can still be considered as a salvage joint-conserving procedure in this selected group of younger patients.

Total Hip Arthroplasty after Previous Chiari Pelvic Osteotomy-A Retrospective Study of 301 Dysplastic Hips

BACKGROUND

Controversy exists whether previous pelvic osteotomies have negative effects on total hip arthroplasty (THA). This study evaluates the implant survival and patient-reported outcomes of THA after previous Chiari pelvic osteotomy (CPO).

METHODS

Data on 301 THAs after CPO were collected through clinical and radiological follow-up examinations and telephone interviews. The Kaplan-Meier survivorship analysis depicts implant survival.

RESULTS

Of this consecutive series of 1536 CPOs, follow-up was completed in 405 patients with 504 CPOs after a mean time of 36 years (±8; range, 22-54 years). At follow-up, 301 hips (60%) had already undergone THA. The overall survival of THA with revision as an end point after 10, 20, and 25 years was 93%, 76%, and 68%, respectively. The revision rate was 12%. The average period between THA and revision surgery was 9.6 years (±6.1; 4 months-25.4 years). The patient's age at revision was 57.9 years (±10; 33.2-78.5 years). Aseptic loosening was the most common of the known reasons for revision surgery.

CONCLUSION

This retrospective study supports the hypothesis that prior CPO does not compromise the prerequisites for successful THA at a later stage. Survival rates of the implanted prosthesis are comparable to primary implanted hips, as overall survival was 93% after 10 years.

Periacetabular Osteotomy for Developmental Dysplasia of the Hip and Femoroacetabular Impingement: A Study Using the U.K. Non-Arthroplasty Hip Registry (NAHR) Data Set

BACKGROUND

Periacetabular osteotomy (PAO) is a well-recognized procedure for the treatment of hip dysplasia in young adults and can be used for the surgical management of femoroacetabular impingement (FAI) with acetabular retroversion. The aim of this study was to use a national database to assess the outcomes of PAO for developmental dysplasia of the hip (DDH) and for FAI.

METHODS

All patients in whom an isolated PAO had been performed between January 2012 and February 2019 were identified in the Non-Arthroplasty Hip Registry (NAHR). Their outcomes were assessed using the EuroQol-5 Dimensions (EQ-5D) index and the International Hip Outcome Tool (iHOT)-12 preoperatively and then at 6 months, 12 months, and 2 years postoperatively.

RESULTS

Six hundred and thirty (630) PAOs were identified, with 558 (89%) performed for DDH and 72 (11%) performed for FAI. Most patients (90%) were female. The mean age in the DDH group (31.2 years) was significantly higher (p < 0.0001) than that in the FAI group (26.5 years). There were no other significant between-group demographic differences. Preoperatively and at each follow-up time-period, iHOT-12 scores were better in the DDH group than in the FAI group; however, only the preoperative scores differed significantly. There was significant improvement between the preoperative and 6-month iHOT-12 and EQ-5D index scores in both the DDH and the FAI group. This improvement was maintained at 12 months postoperatively, by which time almost 90% of the patients had achieved the minimum clinically important difference (MCID) in their iHOT-12 score.

CONCLUSIONS

This study shows that PAO is a successful surgical intervention for DDH and FAI in the short term, with significant improvement in patient-reported outcome scores that is maintained up to 2 years postoperatively.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Patient-Reported Outcomes and Perioperative Complications of Total Hip Arthroplasty Following Joint Preservation Surgery for Hip Dysplasia

BACKGROUND

There is growing recognition of the importance of patient-reported outcome measures and assessment of patient satisfaction in the evaluation of outcomes following surgical interventions. This study aimed to evaluate patient-reported outcomes and complication rates after total hip arthroplasty following joint preservation surgery for hip dysplasia.

METHODS

Patient-reported outcomes and complication rates of 85 hips with previous joint preservation surgery (salvage group) were compared with those of 1279 hips without joint preservation surgery (primary arthroplasty group). As a patient-reported outcome measure, the Japanese Orthopedic Association Hip Disease Evaluation Questionnaire was used to evaluate the hip condition both preoperatively and 12 months postoperatively. Operative data and postoperative (within 12 months) complications were investigated.

RESULTS

The salvage group had a longer operative time (56.8 vs 44.9 minutes, P < .001) and a higher total complication rate (5.9% vs 1.1%, P < .001). Additionally, the salvage group exhibited a lower degree of improvement in the visual analog scale value for satisfaction (75.1 vs 83.1 mm, P = .011), the pain and movement category scores, and the total score of the Japanese Orthopedic Association Hip Disease Evaluation Questionnaire (14.2 vs 16.2, P = .031; 13.7 vs 16.0, P = .005; and 42.3 vs 47.9, P = .007, respectively) compared with the primary arthroplasty group.

CONCLUSION

This study demonstrated a lower rate of improvement in patient satisfaction and worse self-reported outcomes in the salvage group. Furthermore, these patients had a longer operative time and a higher risk of operative complications.

Outcomes in 385 developmental dysplastic hips requiring total hip arthroplasty

BACKGROUND

Patients with developmental dysplasia of the hip (DDH) require special surgical considerations for total hip arthroplasty (THA). Despite the difficulties posed by the population's anatomical abnormalities, few large evaluations of postoperative outcomes exist. This study seeks to characterize outcomes following primary THA among patients diagnosed with DDH.

METHODS

A retrospective review was conducted at a tertiary care center on all THA patients between June 2011 and March 2018. Inclusion criteria for this study included any patient diagnosed with DDH undergoing primary THA. Baseline information, operative reports, and postoperative outcomes were pulled from the medical record.

RESULTS

In total, 336 patients (385 hips) undergoing a THA between June 2011 and March 2018 were included. The average age was 52.6 ± 13.0 years and body mass index was 27.8 ± 6.0 kg/m². Most patients were female (82%). The majority of hips (89%, n = 344) were Crowe type 1, followed by 2 (6.9%, n = 26), 3 (2.6%, n = 10), and 4 (1.3%, n = 5). Most hips were Hartofilakidis Class A (83%, n = 320), followed by Class B (15%, n = 59), then C (1.6%, n = 6). Mean follow-up was 24.8 months. Revision THA was required in 19 (4.9%) cases, with the most common indications being infection (2.1%) and periprosthetic fracture (1.0%). Readmission rates were 1.8% (7 hips) and 2.9% (11 hips) at 30-day and 90-day, respectively. The 30-day and 90-day ED visit rates were 1.3% (5 hips) and 2.1% (8 hips), respectively. No complications were seen following 344 (87%) THAs.

CONCLUSION

Despite their surgical complexity, DDH patients on average have notably low rates of revision and dislocation. Longer follow-up is needed to better assess outcomes after THA in this complex patient population.

Total hip arthroplasty after a previous pelvic osteotomy: A systematic review and meta-analysis

BACKGROUND

There are several reports regarding total hip arthroplasty (THA) after a previous pelvic osteotomy (PO). However, to our knowledge, until now there has been no formal systematic review and meta-analysis published to summarize the clinical results of THA after a previous PO. Therefore, we conducted a systematic review and meta-analysis of results of THA after a previous PO. We focus on these questions as follows: does a previous PO affect the results of subsequent THA, such as clinical outcomes, operative time, operative blood loss, and radiological parameters.

METHODS

Using PubMed, Web of Science, and Cochrane Library, we searched for relevant original papers. The pooling of data was performed using RevMan software (version 5.3, Cochrane Collaboration, Oxford, UK). A p-value<0.05 was judged as significant. Standardized mean differences (SMD) were calculated for continuous data with a 95% confidence interval (CI) was reported. Statistical heterogeneity was assessed based on I² using standard χ² test. When I²>50%, significant heterogeneity was assumed and a random-effects model was applied for the meta-analysis. A fixed-effects model was applied in the absence of significant heterogeneity.

RESULTS

Eleven studies were included in this meta-analysis. The pooled results indicated that there was no significant difference in postoperative Merle D'Aubigne-Postel score (I²=0%, SMD=-0.15, 95% CI: -0.36 to 0.06, p=0.17), postoperative Harris hip score (I²=60%, SMD=-0.23, 95% CI: -0.50 to 0.05, p=0.10), operative time (I²=86%, SMD=0.37, 95% CI: -0.09 to 0.82, p=0.11), operative blood loss (I²=82%, SMD=0.23, 95% CI: -0.17 to 0.63, p=0.25), and cup abduction angle (I²=43%, SMD=-0.08, 95% CI: -0.25 to 0.09, p=0.38) between THA with and without a previous PO. However, cup anteversion angle of THA with a previous PO was significantly smaller than that of without a previous PO (I²=77%, SMD=-0.63, 95% CI: -1.13 to -0.13, p=0.01).

CONCLUSION

Systematic review and meta-analysis of results of THA after a previous PO was performed. A previous PO did not affect the results of subsequent THA, except for cup anteversion. Because of the low quality evidence currently available, high-quality randomized controlled trials are required.

LEVEL OF EVIDENCE

Level III, meta-analysis of case-control studies.

[Bernese periacetabular osteotomy. : Indications, technique and results 30 years after the first description]

The Bernese periacetabular osteotomy (PAO) is a surgical technique for the treatment of (1) hip dysplasia and (2) femoroacetabular impingement due to acetabular retroversion. The aim of the surgery is to prevent secondary osteoarthritis by improvement of the hip biomechanics. In contrast to other pelvic osteotomies, the posterior column remains intact with this technique. This improves the inherent stability of the acetabular fragment and thereby facilitates postoperative rehabilitation. The birth canal remains unchanged. Through a shortened ilioinguinal incision, four osteotomies and one controlled fracture around the acetabulum are performed. The direction of acetabular reorientation differs for both indications while the sequence of the osteotomies remains the same. This surgical approach allows for a concomitant osteochondroplasty in the case of an aspherical femoral head-neck junction. The complication rate is relatively low despite the complexity of the procedure. The key point for a successful long term outcome is an optimal reorientation of the acetabulum for both indications. With an optimal reorientation and a spherical femoral head, the cumulative survivorship of the hip after 10 years is 80-90 %. For the very first 75 patients, the cumulative 20-year survivorship was 60 %. The preliminary evaluation of the same series at a 30-year follow-up still showed a survivorship of approximately 30 %. The PAO has become the standard procedure for the surgical therapy of hip dysplasia in adolescents and adults.

Open treatment of dysplasia-other than PAO: does it have to be a PAO?

Hip dysplasia is a developmental disorder that results in anatomic abnormalities in which the acetabular coverage is insufficient. In the absence of severe degenerative changes, younger active patients with these symptomatic structural abnormalities are increasingly managed with joint-preserving operations. Historically there have been numerous reconstructive pelvic osteotomies. In recent years, the Bernese periacetabular osteotomy (PAO) has become the preferred osteotomy by many surgeons. Even so, as our understanding of the hip advances and new diagnostic and treatment techniques are developed, we sought to put a focus on the long-term results of augmental osteotomies and pelvic osteotomies other than the PAO, to see if any of these surgeries still have a place in the current algorithm of treatment for the dysplastic hip. As the longevity of the treatment is the focal point for joint preservation surgeries for the dysplastic hip, these authors have searched databases for articles in the English literature that reported results of long-term follow-up with a minimum of 11-year survivorship after surgical treatment of developmental dysplasia of the hip. Reconstruction osteotomies for the dysplastic hip are intended to restore normal hip anatomy and biomechanics, improve symptoms and prevent degenerative changes, in this manuscript each procedure is independently assessed on the ability to achieve these important characteristics.

One-third of Hips After Periacetabular Osteotomy Survive 30 Years With Good Clinical Results, No Progression of Arthritis, or Conversion to THA

BACKGROUND

Since its first description in 1984, periacetabular osteotomy (PAO) has become an accepted treatment for hip dysplasia. The 30-year survivorship with this procedure has not been reported. Because these patients are often very young at the time of surgery, long-term followup and identification of factors associated with poor outcome could help to improve patient selection.

QUESTIONS/PURPOSES

Looking at the initial group of patients with hip dysplasia undergoing PAO at the originator's institution, we asked: (1) What is the cumulative 30-year survival rate free from conversion to THA, radiographic progression of osteoarthritis, and/or a Merle d'Aubigné-Postel score < 15? (2) Did hip function improve and pain decrease? (3) Did radiographic osteoarthritis progress? (4) What are the factors associated with one or more of the three endpoints: THA, radiographic progression of osteoarthritis, and/or Merle d'Aubigné-Postel score < 15?

METHODS

We retrospectively evaluated the first 63 patients (75 hips) who underwent PAO for hip dysplasia between 1984 and 1987. At that time, hip dysplasia was the only indication for PAO and no patients with acetabular retroversion, the second indication for a PAO performed today, were included. During that period, no other surgical treatment for hip dysplasia in patients with closed triradiate cartilage was performed. Advanced osteoarthritis (≥ Grade 2 according to Tönnis) was present preoperatively in 18 hips (24%) and 22 patients (23 hips [31%]) had previous femoral and/or acetabular surgery. Thirty-nine patients (42 hips [56%]) were converted to a THA and one patient (one hip [1%]) had hip fusion at latest followup. Two patients (three hips [4%]) died from a cause unrelated to surgery 6 and 16 years after surgery with an uneventful followup. From the remaining 21 patients (29 hips), the mean followup was 29 years (range, 27-32 years). Of those, five patients (six hips [8%]) did not return for the most recent followup and only a questionnaire was available. The cumulative survivorship of the hip according to Kaplan-Meier was calculated if any of the three endpoints, including conversion to THA, progression of osteoarthritis by at least one grade according to Tönnis, and/or a Merle d'Aubigné-Postel score < 15, occurred. Hip pain and function were assessed with Merle d'Aubigné-Postel score, Harris hip score, limp, and anterior and posterior impingement tests. Progression of radiographic osteoarthritis was assessed with Tönnis grades. A Cox regression model was used to calculate factors associated with the previously defined endpoints.

RESULTS

The cumulative survivorship free from conversion to THA, radiographic progression of osteoarthritis, and/or Merle d'Aubigné-Postel score < 15 was 29% (95% confidence interval, 17%-42%) at 30 years. No improvement was found for either the Merle d'Aubigné-Postel (15 ± 2 versus 16 ± 2, p = 0.144) or Harris hip score (83 ± 11 versus 85 ± 17, p = 0.602). The percentage of a positive anterior impingement test (39% versus 14%, p = 0.005) decreased at 30-year followup, whereas the percentage of a positive posterior impingement test (14% versus 3%, p = 0.592) did not decrease. The percentage of positive limp decreased from preoperatively 66% to 18% at 30-year followup (p < 0.001). Mean osteoarthritis grade (Tönnis) increased from preoperatively 0.8 ± 1 (0-3) to 2.1 ± 1 (0-3) at 30-year followup (p < 0.001). Ten factors associated with poor outcome defined as THA, radiographic progression of osteoarthritis, and/or Merle d'Aubigné-Postel score < 15 were found: preoperative age > 40 years (hazard ratio [HR] 4.3 [3.7-4.9]), a preoperative Merle d'Aubigné-Postel score < 15 (HR 4.1 [3.5-4.6]), a preoperative Harris hip score < 70 (HR 5.8 [5.2-6.4]), preoperative limp (HR 1.7 [1.4-1.9]), presence of a preoperative positive anterior impingement test (HR 3.6 [3.1-4.2]), presence of a preoperative positive posterior impingement test (HR 2.5 [1.7-3.2]), a preoperative internal rotation of < 20° (HR 4.3 [3.7-4.9]), a preoperative Tönnis Grade > 1 (HR 5.7 [5.0-6.4]), a postoperative anterior coverage > 27% (HR 3.2 [2.5-3.9]), and a postoperative acetabular retroversion (HR 4.8 [3.4-6.3]).

CONCLUSIONS

Thirty years postoperatively, 29% of hips undergoing PAO for hip dysplasia can be preserved, but more than 70% will develop progressive osteoarthritis, pain, and/or undergo THA. Periacetabular osteotomy is an effective technique to treat symptomatic hip dysplasia in selected and young patients with closed triradiate cartilage. Hips with advanced joint degeneration (osteoarthritis Tönnis Grade ≥ 2) should not be treated with PAO. Postoperative anterior acetabular overcoverage or postoperative acetabular retroversion were associated with decreased joint survival.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Total Hip Arthroplasty after Previous Acetabular Osteotomy: Comparison of Three Types of Acetabular Osteotomy

To compare surgical results of total hip arthroplasty (THA) following acetabular osteotomy, operative records of 13 hips following Chiari osteotomy (Chiari group), 22 hips following rotational periacetabular osteotomy (RAO; RAO group), 16 hips following shelf acetabuloplasty (Shelf group), and 2475 hips without previous osteotomy (Control group) were retrospectively reviewed. The operative time was significantly longer in the RAO group than in the Control group. Bulk bone augmentation was required more often in the Chiari and RAO groups than in the Control group. An early migration of the acetabular cup occurred in 2 hips in the RAO group. RAO made conversion to THA more complicated than did the Chiari osteotomy or the shelf acetabuloplasty.

High survival of dome pelvic osteotomy in patients with early osteoarthritis from hip dysplasia

BACKGROUND

The Chiari osteotomy reportedly has a 60% to 91% survival rate at a minimum 20 years followup. The dome pelvic osteotomy (DPO) has the advantage of allowing a larger weightbearing surface, and congruity in the sagittal plane presumably would reduce the joint contact stress and perhaps increase longevity.

QUESTIONS/PURPOSES

We determined: (1) the survival after DPO at a minimum 25-year followup, (2) patient function, (3) acetabular coverage, and (4) factors influencing conversion to THA.

METHODS

We retrospectively reviewed 50 patients (59 hips) with developmental dysplasia of the hip (DDH) treated with DPO. The preoperative radiographic stages were graded as prearthritis (18 hips), early osteoarthritis (25 hips), and advanced osteoarthritis (16 hips). We performed a Kaplan-Meier survival analysis with THA conversion as the end point. We determined various radiographic parameters reflecting coverage, and compared demographic information for hips without and with THA conversion using multivariate logistic regression analysis. The minimum followup was 25 years (mean, 27.5 years; range, 25-32 years).

RESULTS

Survival for all hips was 63.6% (95% CI, 51-76) at 27.5 years and that for hips with prearthritis and early osteoarthritis before the surgery was 79.1% (95% CI, 63-91). Twenty-one hips (36%) had undergone THAs at a mean 18.3 years (range, 2.5-25 years). At the last followup, pain, walking ability, and acetabular coverage improved. We identified four factors predicting THA conversion: greater age, presence of a preoperative Trendelenburg sign, higher preoperative radiographic osteoarthritis grade, and smaller postoperative acetabular head index (AHI) predicted conversion to THA.

CONCLUSIONS

DPO is a reasonable treatment option for patients with DDH and prearthritis or early osteoarthritis, with high survival at greater than 25 years.

Evaluation of femoral head coverage following Chiari pelvic osteotomy in adolescents by three-dimensional computed tomography and conventional radiography

INTRODUCTION

Currently, the cover of the femoral head was mainly assessed using conventional plain films after Chiari pelvic osteotomy in most studies. The purpose of the current study was to observe whether the femoral head coverage measured by three-dimensional computed tomography (3D-CT) was consistent with the radiographic findings.

PATIENTS AND METHODS

A total of 24 patients (24 hips) with an average age of 11.5 years, underwent Chiari osteotomy due to acetabular dysplasia, and 15 subjects (30 hips) of normal control with a mean age of 12 years were involved in the study. The pre- and postoperative coverage of femoral head was measured by using conventional plain film and 3D-CT on the anterior 1/4, middle 1/2, and posterior 1/4 coronal plane. The anterolateral, mediolateral and posterolateral coverage measured by 3D-CT were compared with the coverage measured by plain radiograph, and which were also compared with the normal control individuals.

RESULTS

The postoperative anterolateral, mediolateral coverage measured by 3D-CT was significantly smaller than that measured by radiography (P < 0.01). No significant difference was found between the 3D-CT measurements on the posterolateral coverage and the radiographic results. The anterolateral femoral head coverage in the patients following Chiari pelvic osteotomy was also smaller than that in the normal control individuals (P = 0.026). In contrast, the postoperative posterolateral coverage in the patients was more excessive than that in the normal control individuals (P = 0.001).

CONCLUSION

Conventional radiographs may show sufficient cover of the femoral head after Chiari osteotomy, whereas in fact, the cover may be not perfect, especially on the anterolateral part. Therefore, the postoperative 3D-CT is beneficial for evaluating the outcome of Chiari osteotomy, especially when the anterolateral coverage o

Similar survival of eccentric rotational acetabular osteotomy in patients younger and older than 50 years

Pelvic osteotomy for middle-aged patients with hip dysplasia remains controversial. We asked whether pelvic osteotomy would yield lower Harris hip scores and survivorship in older patients than in younger patients. We compared patients younger than 50 years (n = 123) with patients 50 years or older (n = 41). At last followup, the mean Harris hip scores improved similarly in both groups: from 60 to 89 points in the older group and from 63 to 92 points in the younger group. However, in patients with bilateral surgery, the older group tended to have lower mean scores than the younger group (86 versus 93 points, respectively). Fifteen-year survivorship with a Harris hip score less than 80 points as the end point was similar in the two groups (71% in older patients and 81% in younger patients). In patients with bilateral surgery, the 15-year survivorship was lower in the older group (66% in older patients and 83% in younger patients). The data suggest eccentric rotational osteotomy for older patients can provide lasting function in most patients. However, prudent selection of patients is required for older patients with bilateral osteoarthritis.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Long-term experience with Chiari's osteotomy

Fifty-six years after the introduction of Chiari's pelvic osteotomy, we report the long-term function scores and radiographic grade of osteoarthritis in 66 patients with 80 pelvic osteotomies with a minimum followup time of 27 years (average, 32 years; range, 27-48 years). These 66 patients were those who could be contacted and who returned for a followup visit from among 450 patients operated between 1961 and 1981. Thirty-two hips (40%) in 28 patients had undergone a total joint arthroplasty after an average 26 years (range, 13-41 years). Forty-eight hips in 41 patients (60%) were not replaced, their Harris hip score being a median of 82 points (range, 37-100 points). For the 22 patients for whom we had complete radiographs the average preoperative CE angle was 11.6 degrees, 48.6 degrees (range, 31 degrees-82.8 degrees) immediately postoperatively, and 41.6 degrees (range, 13.7 degrees-90 degrees) at last followup . Despite a functional hip score in most patients retaining their native hip, the degree of osteoarthritis progressed at last followup. We observed a similar mean age at the time of osteotomy in patients converted to total hip arthroplasty and those retaining their native hip. Age at time of surgery was inversely correlated (r = -0.78) with the interval between the osteotomy and THA. In this select patient group we found good functional outcome in patients who underwent Chiari pelvic osteotomy, with a conversion rate of 40% to total hip arthroplasty a mean of 32 years after the procedure.

LEVEL OF EVIDENCE

Level IV, case series. See Guidelines for Authors for a complete description of levels of evidence.

A computer model for evaluating the osteotomy parameters of Chiari pelvic osteotomy

This study was conducted to evaluate the effect of the various osteotomy parameters on the biomechanical aspects of the hip joint on a computerised model. The data of the radiographs and a three-dimensional (3D) CT scan of six patients with coverage deficient hip joint were used to construct a 3D computer model. Then Chiari type osteotomies were simulated using various heights, angles and fibrocartilage thicknesses. A new angle called the mid acetabular center edge (MACE) angle was defined in a mid coronal CT cut. The optimum displacement for obtaining the maximum coverage averaged 73%. The angle and height of the osteotomy had a significant effect on the MACE angle (P value < 0.01). Our findings of these Chiari parameters may change the results of the osteotomy. The probability of adapting the proximal osteotomy segment to a deformed femoral head was explained by the model and a modified osteotomy "multiple height osteotomy" was proposed.

[Indications and results of corrective pelvic osteotomies in developmental dysplasia of the hip]

BACKGROUND

Joint-preserving reconstructive surgeries in children and adolescents remain challenging for orthopaedists with regard to indication and surgical technique. Besides skeletal maturity and tissue quality at the time of surgery, the kind and degree of deformity, the causative pathologies in secondary dysplasias, and the prognosis have to be considered when deciding for or against a surgical procedure. Developmental dysplasia of the hip (DDH) is the most frequent deformity that indicates reorienting surgery on the hip joint in children and adolescents. The aim of these procedures is to prevent early secondary osteoarthritis. For patients and families as well as for the orthopaedist, risk-benefit analysis is of major interest.

METHODS

In this study, the surgical techniques and specialties of different reconstructive operations are presented. Based on a review of the literature, the results of defined surgical methods are discussed and compared with own experiences.

RESULTS

Only limited information is available about the clinical long-term outcome after defined reconstructing surgery on the hip joint in children and adolescents. The degree of the deformity, the age of onset, and the surgical experience of the orthopaedist are crucial factors in decision making for or against a surgical treatment. In early childhood, acetabuloplasty and Salter osteotomy are widely accepted to correct DDH. Triple and periacetabular osteotomies are preferred and have shown promising results in late adolescence and young adults. When the triradiate cartilage (growth plate) is closed, good outcomes can be achieved by the Ganz osteotomy. Intertrochanteric varus and derotation osteotomies of the femur may serve as additional procedures for pelvic osteotomies and are rarely indicated as a single procedure today.

CONCLUSION

Reconstructive surgery on the hip joint improves function and may prevent early osteoarthritis and delay progression of cartilage degeneration in most patients when the indication and surgical technique are appropriate.

Mean 20-year followup of Bernese periacetabular osteotomy

The goal of the Bernese periacetabular osteotomy is to correct the deficient acetabular coverage in hips with developmental dysplasia to prevent secondary osteoarthrosis. We determined the 20-year survivorship of symptomatic patients treated with this procedure, determined the clinical and radiographic outcomes of the surviving hips, and identified factors predicting poor outcome. We retrospectively evaluated the first 63 patients (75 hips) who underwent periacetabular osteotomy at the institution where this technique was developed. The mean age of the patients at surgery was 29 years (range, 13-56 years), and preoperatively 24% presented with advanced grades of osteoarthritis. Four patients (five hips) were lost to followup and one patient (two hips) died. The remaining 58 patients (68 hips) were followed for a minimum of 19 years (mean, 20.4 years; range, 19-23 years) and 41 hips (60%) were preserved at last followup. The overall mean Merle d'Aubigné and Postel score decreased in comparison to the 10-year value and was similar to the preoperative score. We observed no major changes in any of the radiographic parameters during the 20-year postoperative period except the osteoarthritis score. We identified six factors predicting poor outcome: age at surgery, preoperative Merle d'Aubigné and Postel score, positive anterior impingement test, limp, osteoarthrosis grade, and the postoperative extrusion index. Periacetabular osteotomy is an effective technique for treating symptomatic developmental dysplasia of the hip and can maintain the natural hip at least 19 years in selected patients.

LEVEL OF EVIDENCE

Level III, prognostic study.

[Periacetabular osteotomy medium term survival in adult acetabular dysplasia]

PURPOSE OF THE STUDY

Acetabular dysplasia is a recognized cause of early onset degenerative hip disease. With the widespread use of arthroplasty, the role for conservative treatment has become a controversial issue. Periacetabular osteotomy (PAO) as proposed by Ganz has several advantages, but remains a technically difficult procedure. The purpose of this work was to assess our mid-term results considering indications and potential complications and to describe changes in our technique.

MATERIAL AND METHODS

This study included 33 dysplasic hips in 24 women and four men, treated by PAO. Mean age was 32 years (range 18-47). Mean follow-up was 12 years (range 2-19). The radiographic work-up included an anteroposterior view of the pelvis and anterior and Lequesne oblique views of the hip joint. The cephalocervicodiaphyseal (CC'D), lateral cover (VCE), anterior cover (VCA), and acetabular roof horizontality (HTE) angles and noted whether osteoarthritis was present or not. Hips were classified with the Hip Study Group system as moderate dysplasia (VCE and VCA 25 degrees to 21 degrees ), severe dysplasia (20 degrees to 5 degrees ) and extreme dysplasia (less than 5 degrees ). The complete work-up included an assessment of joint congruency with recentered films in addition to the surgical lateral view of the hip in order to determine a new index called S/FH (S: acetabular surface, FH: half of the femoral head surface). ArthroCT and MRI were performed in patients with signs of osteoarthritis. The original technique included three cuts (ilio-ischiatic, iliopubic, and iliac) close to the acetabulum using a triple access: infracoxofemoral, intrapelvic, and extrapelvic. The first change in the technique was an osteotomy of the anterosuperior iliac spine and an oblique iliac cut farther from the acetabulum.

RESULTS

Preoperatively, average angle measurements were as follows: 135 degrees (121 to 150 degrees ) for CC'D, 23.2 degrees (3 degrees to 40 degrees ) for HTE, 7.6 degrees (-14 degrees to 22 degrees ) for VCE, 11.3 degrees (-26 degrees to 32 degrees ) for VCA. Postoperatively, the values were as follows: 134.5 degrees (121 degrees to 150 degrees ) for CC'D, 9.5 degrees (-9 degrees to 20 degrees ) for HTE, 31.7 degrees (14 degrees to 60 degrees ) for VCE and 31.7 degrees (10 degrees to 48 degrees ) for VCA. An intertrochanteric osteotomy was also performed in one patient. The mean Postel-Merle-d'Aubigné score improved from 7.5 points (range 5.6-11) preoperatively to 14.9 (range 8.1-18). At last follow-up, there was no sign of osetoarthritic degradation in 17 patients (51.5%). Seven patients required total hip arthroplasty at mean four years (two to nine years), including one for aseptic acetabular necrosis. Survival was 73.8+/-9 % at 12 years.

DISCUSSION AND CONCLUSION

This study confirmed the importance of PAO as part of the therapeutic armamentarium for conservative treatment of acetabular dyplasia. Several changes were made in the original technique: the three cuts were all done via the intrapelvic access; for severe and extreme dysplasia, a two thirds PAO was performed. At the present time, the best indication appears to be young subjects (aged less than 30 years) with moderate to severe dysplasia, with no sign (even minimal) of intra-articular disorder or osteoarthritis.

The results of Chiari pelvic osteotomy in adolescents with a brief literature review

PURPOSE

Chiari medial displacement osteotomy is a procedure that uses the cancellous bone of the ilium to contain the femoral head and bear weight. It is the most contraversial osteotomy of the hip joint. This study was therefore conducted to determine the results of this osteotomy with mid-term follow-up in children.

METHODS

From 1995 to 2004, 20 Chiari pelvic osteotomies (in 18 patients) were performed. There were 15 male and 3 female patients. The average age at operation was 12.6 years and the mean follow-up was 54 months. The operative technique was as described by Chiari. An iliofemoral approach was used without utilizing a traction table. If there was anterior or anterolateral uncoverage of the femoral head, bone graft augmentation was performed.

RESULTS

The angle of the osteotomy averaged 12 degrees , with the distance from the acetabulum averaging 3.2 mm. The average displacement was 42%. Of the 20 Chiari osteotomies, 11 were categorized as excellent, 8 as good and one as fair in terms of clinical and radiological results. Student's t test statistics showed improvements in all radiologic parameters of the hip joint (Sharp angle, center-edge angle and coverage of the femoral head). Graft resorption was observed in 25% of the patients.

CONCLUSION

There are very rare indications of Chiari osteotomy in patients younger than 10 years. Because of the high rate of graft resorption, Chiari osteotomy should be the last treatment option when there is anterior or anterolateral uncoverage of the hip joint.

Total hip arthroplasty of dysplastic hip after previous Chiari pelvic osteotomy

INTRODUCTION

Many reports have suggested that Chiari pelvic osteotomy would improve the results of acetabular component placement and fixation in subsequent total hip arthroplasty. However, little is known concerning the biomechanical, radiological, and clinical effects of Chiari pelvic osteotomy on subsequent total hip arthroplasty.

MATERIALS AND METHODS

Ten total hip arthroplasties for developmental dysplasia of the hip after previous Chiari pelvic osteotomy (Chiari group) were compared with 20 total hip arthroplasties for developmental dysplasia of the hip without previous surgery (control group). Preoperative patient demographic data and operative technique were well matched between the groups. The mean duration of follow-up was 3.0 years. Biomechanical, radiological, and clinical evaluations were performed.

RESULTS

No acetabular or femoral components exhibited loosening. All patients had good or excellent clinical score according to the Merle d'Aubigne-Postel rating system at the most recent follow-up. Abductor force and joint force were smaller in the Chiari group, although long operative time, more blood loss, and verticalization of joint force were noted in this group.

CONCLUSION

This limited study suggested that Chiari pelvic osteotomy changed the biomechanical features of the hip joint, and that this alteration might have compromised subsequent total hip arthroplasty.

Long-term results of Chiari pelvic osteotomy in patients with developmental dysplasia of the hip: indications for Chiari pelvic osteotomy according to disease stage and femoral head shape

BACKGROUND

We evaluated the long-term results of Chiari pelvic osteotomy for developmental dysplasia of the hip (DDH) after follow-up of 10 years or more. The indications for Chiari osteotomy were assessed based on the results.

METHODS

We evaluated 74 hips in 69 patients treated for DDH with Chiari osteotomy. The average postoperative follow-up period was 13 years. The mean age at the time of surgery was 32 years (range 6-64 years). The disease was classified into two stages based on joint space measurements on radiographs: an early stage (36 hips) in which the mean age at surgery was 21 years (range 6-48 years) and an advanced stage (38 hips) in which the mean age at surgery was 41 years (range 18-64 years). Femoral head shape was classified into two types based on measurements of the sphericity of the femoral head: spherical (33 hips) or flat (41 hips). Clinical manifestations were evaluated according to Japanese Orthopaedic Association (JOA) hip scores. The joint space was measured on radiographs as an index of the progression of osteoarthritis. We attempted to identify factors that affected the long-term results of Chiari osteotomy, especially in regard to disease stage and femoral head shape.

RESULTS

The mean total JOA score was 72 preoperatively and 87 at final follow-up. It had improved in 66 hips and was worse in 7 hips. All of the worse cases were at the advanced stage at the time of surgery, and in 6 of the worse cases the femoral head was spherical. Hips with advanced DDH and a spherical femoral head had poor outcomes and exhibited joint space narrowing postoperatively.

CONCLUSIONS

Early DDH is considered a good indication for Chiari pelvic osteotomy because of the good results at 10 years or more. Even with advanced DDH, a flat femoral head predicts a good surgical outcome, but patients with a spherical femoral head may experience early progression to osteoarthritis.

Long-term survivorship of hip shelf arthroplasty and Chiari osteotomy in adults

The current authors retrospectively assessed 56 hip shelf arthroplasties (48 patients) with a mean followup of 17 years (range, 15-30 years) and 89 Chiari osteotomies (82 patients) with a mean followup of 13 years (range, 6-25 years) done in adults with painful hip dysplasia. Preoperative joint space narrowing was observed in 32 of 56 shelf arthroplasties and in 67 of 89 Chiari osteotomies. Survival rates, using hip replacement as the end point, were 37% (20% to 54%) at 20 years for shelf arthroplasty and 68% (54% to 81%) at 18 years for Chiari osteotomy. The severity of preoperative arthrosis was the main factor that impaired the survivorship of shelf arthroplasty and Chiari osteotomy. With arthritic changes without joint space narrowing, the 18-year survival rates were 83% (69% to 97%) for shelf arthroplasty and 94% (89% to 99%) for Chiari osteotomy. Shelf arthroplasty is best indicated for moderate dysplasia (center edge angle >0 degrees) without severe arthrosis. Chiari osteotomy is best suited for severe dysplasia (center edge angle <0 degrees) especially without or with slight arthrosis. Chiari osteotomy also can be a salvage procedure when marked joint space narrowing is present but only if it is related to severe dysplasia (center edge angle <0 degrees).

Rationale of osteotomy and related procedures for hip preservation: a review

Most osteoarthrosis of the hip results from chronic abnormal hip mechanics, often associated with instability, impingement, or combinations of instability and impingement. The etiology of the mechanical problems in many hips is a surgically treatable anatomic abnormality, often a developmental deformity (dysplasia, Perthes disease, slipped epiphysis, femoral or acetabular retroversion, or reduced head-neck offset). The rationale of mechanically-based measures to prevent or treat osteoarthrosis assumes the following: (1) correctable mechanical overload is a major etiologic factor in osteoarthrosis; and (2) relief of the mechanical overload can prevent or improve osteoarthrosis. The success of such mechanically-based joint-preserving measures depends largely on the completeness with which the joint-preserving treatment normalizes the mechanical environment of the hip. A limiting factor often is the amount of irreversible articular damage that is present at the time treatment is begun.

Does Chiari osteotomy compromise subsequent total hip arthroplasty?

We compared 28 total hip arthroplasties done in dysplastic hips after previous Chiari osteotomy (group I) with a well-matched control group of 50 primary procedures (group II) done during the same period at an average follow-up of 5 years (range, 25-199 months). Group I required significantly less acetabular augmentation, had significantly shorter operative times, had less intraoperative blood loss, and had fewer complications than group II. There was no significant difference between the 2 groups in terms of clinical or radiographic outcome. Total hip arthroplasty after a successful Chiari osteotomy leads to medium-term results similar to those of other dysplastic hips. In our experience, less bone grafting was required, better coverage of the cup by host-bone was obtained, and the center of motion of the hip was more anatomic. Chiari osteotomy may delay the need for total hip arthroplasty, may facilitate acetabular reconstruction, and does not seem to compromise the medium-term clinical or radiographic outcome.

Surgical treatment of developmental dysplasia of the hip in adults: I. Nonarthroplasty options

Hip dysplasia is a developmental disorder that results in anatomic abnormalities leading to increased contact pressure in the joint and, eventually, coxarthrosis. However, many patients with hip dysplasia become symptomatic before the development of severe degenerative changes because of abnormal hip biomechanics, mild hip instability, impingement, or associated labral pathology. Several nonarthroplasty treatment options are available. Because the primary deformity is mostly acetabular, for many patients, a reconstructive osteotomy that restores more nearly normal pelvic anatomy is preferable. The Bernese periacetabular osteotomy is presently favored because it provides good correction while creating little secondary pelvic deformity or destabilizing the pelvis. Proximal femoral osteotomy is occasionally needed as a complement to pelvic osteotomy and may also be indicated as an isolated procedure when most deformity is located on the femoral side (coxa valga subluxans). Arthroscopy can be beneficial when symptoms seem to be related only to labral tears or loose bodies in the absence of severe structural abnormalities about the hip. Fusion and resection arthroplasty are rarely indicated and are reserved for occasional patients who are not candidates for total hip replacement or other procedures but who complain of refractory hip pain.

Total hip arthroplasty in neglected congenital high dislocation of the hip. A comparison of four different surgical techniques

The safest and easiest technique of performing a total hip replacement (THR) in neglected high congenitally dislocated hip (CDH) is still debatable. To find the best method, a prospective randomised trial comparing four different techniques was undertaken. A total of 48 THRs were performed on 40 patients with CDH. Average age was 40.6 years and average follow-up was 42 months. Four different techniques (n=12 each) were used: 1) THR into neo-acetabulum in a single operation, 2) THR into real acetabulum as a one stage procedure, 3) Campbell release operation followed by THR into real acetabulum after three weeks of traction, 4) THR with proximal femoral shortening. Even though shortening and one stage THR is technically more demanding we believe it superior to the other techniques. (Hip International 2002; 12: 308-13).

Present role of femoral and acetabular osteotomies: The Chiari osteotomy (long term follow-up)

none.

Bombelli's valgus-extension osteotomy for osteoarthritis due to acetabular dysplasia: results at 10 to 14 years

Severe osteoarthritis due to acetabular dysplasia (n = 17) was treated with valgus-extension osteotomy, and the patients' clinical outcomes 10-14 years after operation were evaluated according to clinical factors (Japanese Orthopaedic Association hip score; JOA score) and by roentgenography. The mean JOA score 10 years or later had improved by 22 points compared with the preoperative score. On roentgenography, joints which had preoperative roof osteophyte had better postoperative formation of roof osteophyte. The JOA score was higher in the 12 joints which had osteophyte 5 mm or longer than in those joints with osteophyte that was 5 mm or shorter. Postoperative joint space widening occurred in 15 joints (88.2%) 3-6 months postoperatively, and it reached the maximum at 3-5 years. In patients who had a large bone cyst in the femoral head preoperatively, the cyst collapsed, and deformation of femoral head occurred after operation, but remodeling of the joint surface occurred naturally and the congruity improved. In the 6 joints in which the preoperative acetabular head index was less than 60% and the acetabular angle was larger than 30 degrees, the JOA score at 10 years or later was lower than that of the other joints. Based on these findings, valgus-extension osteotomy was evaluated as a useful surgical method for advanced or terminal osteoarthritis in young or middle-aged patients. Predictive factors for long-term prognosis would be the preoperative length of roof osteophyte, joint space widening, and the degree of femoral head covering.

Results of periacetabular osteotomy in patients with previous surgery for hip dysplasia

The results of 19 periacetabular osteotomies in 18 patients who had undergone prior bony surgical procedures for hip dysplasia were evaluated. There were 10 females and eight males with an average age of 30.9 years. Previous surgical interventions included 18 intertrochanteric osteotomies, nine pelvic osteotomies, and two shelf acetabuloplasties. The average clinical followup for this group was 45 months. Harris hip score averages improved from 60 to 90 points. Merle d'Aubigne scores showed similar elevations from 13.1 to 16.4 points. Radiographic assessment documented increased coverage and lower Tönnis secondary arthrosis grades in a significant number of hips. No significant differences in outcome were found between this group and a reference group of patients undergoing periacetabular osteotomy who had no previous hip surgery. These intermediate term results are encouraging and seem to discount anticipated problems of prior scarring and distorted pelvic and proximal femoral anatomy.

Bernese periacetabular osteotomy

Seventy-five symptomatic dysplastic hip joints (63 patients) were treated with the Bernese periacetabular osteotomy during a period of 44 months. The mean patients' age was 29 years (range, 13-56 years) and the female:male ratio was 3.4:1. Group III dysplasia according to Severin was seen in 50% and Group IV dysplasia was seen in 44% of the patients. Osteoarthritis was present in 58% of the patients. Followup was obtained at a mean of 11.3 years (range, 10-13.8 years) in 71 hip joints (95%). Radiographic measurements of the lateral center edge angle, anterior center edge angle, acetabular index, lateralization of the femoral head, and intactness of Shenton's line showed a high correction potential of this type of osteotomy. In 58 patients (82%) the hip joint was preserved at last followup with a good to excellent result in 73%. Unfavorable outcome was significantly associated with higher age of the patient, moderate to severe osteoarthritis at surgery, a labral lesion, less anterior coverage correction, and a suboptimal acetabular index. Major complications were encountered in the first 18 patients including an intraarticular cut in two, excessive lateralization in one, secondary loss of correction in two and femoral head subluxation in three patients.

Long-term outcome of rotational acetabular osteotomy: 145 hips followed for 10-23 years

We report the long-term outcome of rotational acetabular osteotomy in 145 dysplastic hips of 131 patients after an average follow-up of 13 (10-23) years. The mean age at operation was 28 (11-52) years. The radiographic severity of osteoarthrosis before operation, according to the criteria of the Japanese Orthopaedic Association, was stage I (no degenerative change) in 63 hips, stage II (early degenerative stage) in 49, stage III (progressive stage) in 21 and stage IV (end stage) in 12. The clinical outcome based on the Merle d'Aubigné and Postel score was excellent or good for 90 (80%) of the 112 hips which had stage I or II osteoarthrosis preoperatively, and was excellent or good for only 9 of the 33 hips which had stage III or IV osteoarthrosis (p < 0.001, chi-square test). The radiographic severity of osteoarthrosis at the most recent review was stage I or II for 79 (70%) of the 112 hips which had stage I or II osteoarthrosis preoperatively. The long-term outcome of rotational acetabular osteotomy was satisfactory for a dysplastic hip with little, if any, osteoarthrosis, but was unsatisfactory for a hip with more advanced osteoarthrosis.

Surgical correction of "functional retroversion" and "functional coxa vara" in late Legg-Calvé-Perthes disease and epiphyseal dysplasia: correction of deformity defined by new imaging modalities

We studied six patients with severe femoral head deformity treated surgically by valgus-flexion-internal-rotation femoral osteotomy plus simultaneous acetabuloplasty based on the concept of "functional retroversion" and "functional coxa vara" of the deformed femoral head in late severe Legg-Calvé-Perthes disease and epiphyseal dysplasia. The combined procedure achieves the following: (i) corrects the "functional coxa vara" and hinge abduction (valgus osteotomy); (ii) establishes a more normal articulation between the posteromedial portion of the true femoral head and the acetabulum, while moving the anterolateral protruding portion of the femoral head away from the anterolateral acetabular margin (valgus-flexion osteotomy); (iii) corrects external-rotation deformity of the distal limb (internal-rotation osteotomy); (iv) improves joint congruity and anterolateral femoral-head coverage in hips with associated acetabular dysplasia (acetabuloplasty).