Aims. The objective of this study was to present the outcomes of rotational acetabular osteotomy (RAO) over a 30-year period for osteoarthritis (OA) secondary to dysplasia of the hip in pre- or early-stage OA. Methods. Between September 1987 and December 1994, we provided treatment to 47 patients (55 hips) with RAO for the management of pre- or early-stage OA due to developmental hip dysplasia. Of those, eight patients (11 hips) with pre-OA (follow-up rate 79%) and 27 patients (32 hips) with early-stage OA (follow-up rate 78%), totalling 35 patients (43 hips) (follow-up rate 78%), were available at a minimum of 28 years after surgery. Results. In the pre-OA group, the mean Merle d'Aubigné score improved significantly from 14.5 points (SD 0.7) preoperatively to 17.4 points at final follow-up (SD 1.2; p = 0.004) and in the early-stage group, the mean score did not improve significantly from 14.0 (SD 0.3) to 14.6 (SD 2.4; p = 0.280). Radiologically, the centre-edge angle, acetabular roof angle, and head lateralization index were significantly improved postoperatively in both groups. Radiological progression of OA was observed in two patients (two hips) in the pre-OA group and 17 patients (18 hips) in the early-stage group. Kaplan-Meier survival analysis, with radiological progression of OA as the primary outcome, projected a 30-year survival rate of 81.8% (95% confidence interval (CI) 0.59 to 1.00) for the pre-OA group and 42.2% (95% CI 0.244 to 0.600) for the early-stage group. In all cases, the overall survival rate stood at 51.5% (95% CI 0.365 to 0.674) over a 30-year period, and when the endpoint was conversion to total hip arthroplasty, the survival rate was 74.0% (95% CI 0.608 to 0.873). Conclusion. For younger patients with pre-OA, joint preservation of over 30 years can be expected after RAO. Cite this article: Bone Joint J 2024;106-B(5 Supple B):25–31

We performed rotational acetabular osteotomy in order to treat dysplasia of the hip in five ambulatory adults with cerebral palsy. There was one man and four women, with a mean age of 21 years (16 to 27) who were followed up for a mean of 12 years and two months. The mean Sharp angle improved from 52° to 43°, the mean acetabular index from 30.2° to 2.8°, the mean centre-edge angle from −5.6° to 29.2°, and the mean acetabular head index from 49.2 to 88.2. There was no progression of joint degeneration and relief from pain was maintained. Our results suggest that rotational acetabular osteotomy is a valuable option for the treatment of acetabular dysplasia in adults with cerebral palsy who have incapacitating pain in the hip

We have studied whether the state of the articular cartilage at the time of rotational acetabular osteotomy for dysplasia of the hip affects the outcome 2 to 5.5 years after surgery. Arthroscopy in 57 patients (59 joints) at the time of the operation showed grade-0 changes in seven, grade-1 in nine, grade-2 in 17, grade-3 in 14 and grade-4 in 12 joints, according to the classification of Outerbridge. There was radiological evidence of the progression of arthritis in four joints which were classified at arthroscopy as grade 4. Stepwise regression analysis showed that damage to acetabular or femoral articular cartilage significantly affected the progression of arthritis. We conclude that the short-term results of successful rotational acetabular osteotomy for dysplasia are affected by the state of the articular cartilage

Acetabular dysplasia was produced in 24 immature white rabbits. A rotational acetabular osteotomy was then carried out and radiological and histological studies of the articular cartilage were made. In the hips which did not undergo osteotomy, radiographs at 26 weeks showed that residual subluxation remained and arthritic changes such as narrowing of the joint space or dislocation were still seen. However, in the operated group there was a remarkable increase in cover, but arthritic changes were not observed. After 24 weeks, the Mankin grading score in the operated group was significantly lower than that in the non-operated group. The latter hips showed an irregular surface of the cartilage, exfoliation and proliferation of synovial tissue. In those undergoing osteotomy, primary cloning of chondrocytes or hypercellularity was seen and at 24 weeks after operation and metaplasia of the cartilage in the fibrous tissue was observed in the boundary between the medial area of the acetabulum and the acetabular fossa

We have investigated the factors which affect the progression of osteoarthritis after rotational acetabular osteotomy (RAO). Between 1984 and 1998, we treated 60 dysplastic hips by RAO. The mean age at surgery was 31.6 years (13 to 51) and the mean period of follow-up was 4.6 years (2 to 9.5). The thickness of the articular cartilage on the weight-bearing area, pre- and postoperative acetabular cover, and the sphericity of the femoral head were used for radiological assessment. The osteoarthritis did not progress in 39 hips. Significant factors which affected the radiological grade included sphericity of the femoral head and the postoperative acetabular cover. The surgical approach and preoperative acetabular cover did not affect the progression of osteoarthritis. Patients were divided into two groups according to the surgical approach used, either conventional (23 hips) or modified (37 hips). Significant factors included the postoperative acetabular cover in the modified approach, and the sphericity of the femoral head in the conventional approach. It is critical that the postoperative cover is sufficient, especially when RAO is carried out using our modified technique

Aims. The influence of identifiable pre-operative factors on the outcome of eccentric rotational acetabular osteotomy (ERAO) is unknown. We aimed to determine the factors that might influence the outcome, in order to develop a scoring system for predicting the prognosis for patients undergoing this procedure. Patients and Methods. We reviewed 700 consecutive ERAOs in 54 men and 646 women with symptomatic acetabular dysplasia or early onset osteoarthritis (OA) of the hip, which were undertaken between September 1989 and March 2013. The patients’ pre-operative background, clinical and radiological findings were examined retrospectively. Multivariate Cox regression analysis was performed using the time from the day of surgery to a conversion to total hip arthroplasty (THA) as an endpoint. A risk score was calculated to predict the prognosis for conversion to THA, and its predictive capacity was investigated. Results. The congruity of the hip, age, the pre-operative minimum width of the joint space and range of abduction were identified as factors predicting conversion to THA. For three groups of patients (scoring 0 to 5, 6 to 7, and 8 to 9 points), the Kaplan-Meier event-free rates of survival at 15 years post-operatively for conversion to THA were 99.6%, 85.2% and 67.3%, respectively. Conclusion. These four pre-operative factors are easily measured and predict the prognosis for patients following ERAO. They may be used for decision making when offering surgical treatment to patients with acetabular dysplasia and early onset osteoarthritis. Cite this article: Bone Joint J 2016;98-B:1326–32

Aims

Rotational acetabular osteotomy (RAO) is an effective joint-preserving surgical treatment for acetabular dysplasia. The purpose of this study was to investigate changes in muscle strength, gait speed, and clinical outcome in the operated hip after RAO over a one-year period using a standard protocol for rehabilitation.

Aims

Rotational acetabular osteotomy (RAO) has been reported to be effective in improving symptoms and preventing osteoarthritis (OA) progression in patients with mild to severe develomental dysplasia of the hip (DDH). However, some patients develop secondary OA even when the preoperative joint space is normal; determining who will progress to OA is difficult. We evaluated whether the preoperative cartilage condition may predict OA progression following surgery using T2 mapping MRI.

In this study we used subject-specific finite element analysis to investigate the mechanical effects of rotational acetabular osteotomy (RAO) on the hip joint and analysed the correlation between various radiological measurements and mechanical stress in the hip joint.

We evaluated 13 hips in 12 patients (two men and ten women, mean age at surgery 32.0 years; 19 to 46) with developmental dysplasia of the hip (DDH) who were treated by RAO.

Subject-specific finite element models were constructed from CT data. The centre–edge (CE) angle, acetabular head index (AHI), acetabular angle and acetabular roof angle (ARA) were measured on anteroposterior pelvic radiographs taken before and after RAO. The relationship between equivalent stress in the hip joint and radiological measurements was analysed.

The equivalent stress in the acetabulum decreased from 4.1 MPa (2.7 to 6.5) pre-operatively to 2.8 MPa (1.8 to 3.6) post-operatively (p < 0.01). There was a moderate correlation between equivalent stress in the acetabulum and the radiological measurements: CE angle (R = –0.645, p < 0.01); AHI (R = –0.603, p < 0.01); acetabular angle (R = 0.484, p = 0.02); and ARA (R = 0.572, p < 0.01).

The equivalent stress in the acetabulum of patients with DDH decreased after RAO. Correction of the CE angle, AHI and ARA was considered to be important in reducing the mechanical stress in the hip joint.

Cite this article: Bone Joint J 2015;97-B:492–7.

We evaluated the results of rotational acetabular osteotomy in 44 hips (42 patients) with advanced osteoarthritis secondary to developmental dysplasia. The mean age of the patients at surgery was 43.4 years (30 to 59) and the mean follow-up was 12.1 years (8 to 19). The mean Merle d’Aubigné clinical score improved from 10.8 points (8 to 15) pre-operatively to 13.5 points (6 to 18) at follow-up. Radiologically, this procedure produced adequate improvement regarding cover of the femoral head. At follow-up, the osteoarthritic stage assessed using the Japanese Orthopaedic Association grading, was improved in 11 hips (25%), unchanged in 22 (50%) and had progressed in 11 (25%). The mean pre-operative roundness index of the femoral head was significantly different in the 33 hips which had improved or maintained their osteoarthritic stage compared with the 11 which had progressed (53.7% vs 63.7%; p < 0.001). Osteoarthritis with a round femoral head is considered to be an indication for rotational acetabular osteotomy, even in advanced stages of the disease

Satisfactory intermediate and long-term results of rotational acetabular osteotomy (RAO) for the treatment of early osteoarthritis secondary to developmental dysplasia of the hip have been reported. The purpose of this study is to examine the 30-year results of RAO. Between 1987 and 1994, we treated 49 patients (55 hips) with RAO for diagnosis of pre- OA or early-stage OA. Of those patients, 35 patients (43 hips) were available at a minimum of 28 years. The follow-up rate was 78.2% and the mean follow-up was 30.5 years. The mean age at the time of surgery was 34 years. Clinical evaluation was performed with the Merle d'Aubigne and Postel rating scale, and radiographic analyses included measurements of the center-edge angle, acetabular roof angle, and head lateralization index on preoperative, postoperative AP radiographs of the pelvis. Postoperative joint congruency was classified into four grades. The radiographic evidence of progression of OA was defined as the minimum joint space less than 2.5mm. The mean preoperative clinical score was 14.0, which improved to a mean of 15.3 at the time of the latest follow-up. The mean center-edge angle improved from 0.6° preoperatively to 34° postoperatively, the mean acetabular roof angle improved from 28.4°preoperatively to 1.0°postoperatively, the mean head lateralization index improved from 0.642 preoperatively to 0.59 postoperatively. Postoperative joint congruency was excellent in 11 hips, good in 29 hips, and fair in 3 hips. Nineteen patients (20 hips) had radiographic OA progression, and 10 patients (11 hips) were converted to THA. Kaplan-Meier survivorship analysis, with radiographic OA progression as the end point, predicted survival of 75.6% at 20 years and 48.8% at 30 years, and with THA conversion as the end point, 90.2% at 20 years and 71.2% at 30 years. The RAO is an effective surgical procedure for symptomatic dysplastic hips of pre- and early-stage OA and could change the natural history of the dysplastic hip

Aims. The aim of this study was to report the long-term results of rotational acetabular osteotomy (RAO) for symptomatic hip dysplasia in patients aged younger than 21 years at the time of surgery. Patients and Methods. We evaluated 31 patients (37 hips) aged younger than 21 years at the time of surgery retrospectively. There were 29 female and two male patients. Their mean age at the time of surgery was 17.4 years (12 to 21). The mean follow-up was 17.9 years (7 to 30). The RAO was combined with a varus or valgus femoral osteotomy or a greater trochanteric displacement in eight hips, as instability or congruence of the hip could not be corrected adequately using RAO alone. Results. The mean Merle d’Aubigné clinical score improved significantly from 15.4 to 17.2 (p < 0.0001). The mean centre-edge (CE) angle improved from -2.6° to 26°, the mean acetabular roof angle improved from 3.0° to 5.2°, and the mean head lateralization index improved from 0.68 to 0.62. Progression of radiological osteoarthritis (OA) was seen in seven hips, but no patient underwent total hip arthroplasty. Conclusion. RAO is an effective form of correction for a severely dysplastic hip in adolescent and young adult patients. Cite this article: Bone Joint J 2019;101-B:390–395

[Introduction]. Total hip arthroplasty (THA) markedly improves pain, gait, and activities of daily living for most patients with osteoarthritis. However, pelvic osteotomy has been recommended for young and active patients with hip dysplasia, because THA in that population is associated with high rates of revision THA. The rotational acetabular osteotomy (RAO) of Ninomiya and Tagawa, and the eccentric rotational acetabular osteotomy of Hasegawa for hip dysplasia reportedly are successful in young and active patients. However, even after the surgery of RAO, osteoarthritis developed in some cases and leaded to the conversion to THA. The differences of bone quality of acetabulum have been reported between at the surgery of THA after RAO and at the surgery of primary THA. We should not discuss the results of these two THA equally. The purpose of this study is to report the results of THA after RAO. [Patients and Methods]. We retrospectively reviewed 33 patients (37 hips) treated by total hip arthroplasty after rotational acetabular osteotomy between 1992 and 2012. Five cases were performed RAO with valgus osteotomy. At the time of THA surgery, the overall mean age of the patients was 57.5 years (range, 39–72 years). The average of follow-up period was 7.0 years (range, 8–258 months). One surgeon (TT) evaluated the hips clinically using the Japanese Orthopaedics Association (JOA) score. The radiographic measurements were performed by the other physician (JY) blinded to the clinical scores. Radiographical examination was performed using AP X-ray. We evaluated the presence of osteolysis and loosening of the implants. We evaluated the stability of stem implants using Engh classification and of cup implants using Hodgkinson classification. [Results]. The cases of this study were converted to THA in an average 17.2 years after the surgery of RAO. JOA score was 55.7 points before THA and 86.7 points at the final follow-up. Osteolysis were found in five cases. Thirty-three cases showed good implant stability, but four cases showed fibrous union between cup and acetabulum. Three cases were converted to the revision THA due to fibrous union. All revision cases were acetabular side. [Discussion]. There were no reports about results of THA after RAO. Osteotomy should be considered for young patients because of the high rates of revision THA needed owing to prolongation of the average lifespan. McAuley et al reported the results of THA in patients 50 years and younger patients. They described the survival rates for femoral and acetabular components, using any revision as the end point, were 89% at 10-year followup and 60% at 15-year followup. Osteosclerosis of the acetabular roof bone should be careful in the case of THA after RAO. The cancellous bone could hardly be founded, even if the enough reaming was performed. Osteosclerosis may cause the difficulty in ingrowth of new bone into the implant, and lead to fibrous union between the acetabular roof bone and the implant. These two revision cases showed fibrous union before their THA. Primary fixation is very important in the case of THA after RAO. Primary fixation is very important in the case of THA after the RAO

Aims: To evaluate technical and clinical results of a new 2-incision technique of rotational acetabular osteotomy. Methods: 27 patients, with a mean age of 40 years, were reviewed after a minimum of 1 year subsequently to rotational acetabular osteotomy, which was done through short low midline and iliac approaches. An analysis of complications, the length of rehabilitation period, time to union of the osteotomy, radiographic correction of acetabular roof, proceeding of hip arthrosis, as well as of clinical status at follow-up, using scores by Merle DñAubigne and Harris, was performed. Results: No major operative complications were observed. The median time to union of osteotomy and a painless status was 10 weeks. Femoral head covering by acetabular roof increased signiþcantly, whereas the range of motion of the operated hip was not compromised by the operation. A signiþcant increase in the mean scores, mainly caused by a decrease in pain, were observed in a subgroup of 20 patients with a minimum follow-up of 2 years. The most signiþcant factor predisposing poor outcome was grave preoperative arthrosis of the hip. Conclusions: This new technique of osteotomy is safe and less traumatic than previous methods, allowing early weight bearing and a fast recovery. The early clinical results are satisfactory

Background. The rotational acetabular osteotomy (RAO), that was developed in Japan, has been used successfully in patients with developmental dysplasia of the hip (DDH) (Figure 1). However there are some patients who are forced to have a total hip arthroplasty (THA) due to the progression of osteoarthritis. It is unknown if a RAO poses technical difficulties or increases the chances of complications if a THA must be performed afterwards becausethere is not much data on patients who underwent a THA after a previous RAO. Objectives. The purpose of this study was to investigate the mid-term results of a THA after a RAO. Methods. We compared 22 THAs (2 males and 16 females) that were performed after previous RAOs (group R) with a control group of 28 patients (30 hips) who only underwent THAs (2 males and 27 females, group C). The average age at surgery in Group R and C was 53.6 years and 55.8 years, the average follow-up period was 7.2 years (range, 6–10 years), 7.7 years (range, 6–11 years). The average interval from osteotomy to THA was 12.7 years. Trilogy acetabular components (Zimmer) were used for all patients. Results. No acetabular or femoral components exhibited loosening or revision in both groups. No osteolysis was seen in both groups and there was no significant difference in terms of the incidence of ectopic ossification. The Harris hip score (HHS) at the most recent follow-up was not compromised (Group R: mean, 93.2, Group C: 94.3), there were no significant differences in intraoperative blood loss and operative times between the two groups (Group R: mean, 136.0 ml; 89.5 mins, Group C: 131.3 ml; 96.3 mins) Group R did not have higher rates of infection, dislocation, intraoperative fracture or deep venous thrombosis compared with group C. Acetabular components in group R were placed more superiorly and laterally than group C (Figure 2, Table 1). On the other hand, the acetabulum after RAO often gets harder than the one that did not undergo a previous osteotomy. The Screw that is used to fix the acetabular component has been found to work well in securing the sclerotic acetabulum, thus screw fixation of a cementless cup is a feasible option for a THA after a RAO. Conclusions. Patients who underwent aTHA after a successful RAO had mid-term results similar to those of other dysplastic hips. The results of this study found RAOs do not lead to higher revisions rates, compromised HHSs, or shortened survivorships in eventual THAs in DDHs. However there was a tendency of superolateral placement of the acetabular component, therefore a longer follow-up is required to confirm if polyethylene wear increases. The results of this study indicated rotational acetabular osteotomies do not lead to higher revisions rates, compromised HHSs, or shortened survivorships in eventual total hip arthroplasties in developmental dysplasia of the hip

Introduction. Several reports demonstrated the overcoverage of the anterior acetabulum. Anterior CE angle over 46°may be a probable risk factor for pincer FAI syndrome after a rotational acetabular osteotomy. In addition, a highly anteverted femoral neck, reported as a risk factor for posterior impingement, has been found in DDH patients. These findings indicate proper acetabular reorientation is essential to avoid anterior or posterior impingement after periacetabular osteotomy (PAO). The aim of this study was to evaluate the relationship between acetabular three-dimensional (3D) alignment reorientation and clinical range of motion (ROM) after periacetabular osteotomy (PAO). Methods. A total of 53 patients who underwent curved PAO (CPO) for DDH from January 2014 to April 2017 were selected. Three (5.7%) of them were lost to follow-up. Therefore, the data from 58 hips, contributed by 50 patients (44 women and 6 men), were included in the analysis. Pre- and postoperative computed tomography (CT) scans from the pelvis to the knee joint were performed and transferred to a 3D template software (Zed Hip; Lexi, Tokyo, Japan). The pelvic plane axis was defined according to the functional pelvic plane. The pre- and postoperative lateral and anterior 3D center-edge (CE) angles were measured on the coronal and sagittal views through the center of the femoral head. The pre- and postoperative 3D center-edge (CE) angles and femoral anteversion were measured and compared with clinical outcomes, including postoperative ROM. Results. The radiographical outcomes of our study are demonstrated in Figure 1. The mean values of pre- and postoperative lateral CE angles were 12.6º±8.7 and 30.2º±9.7, respectively (p<0.001), and mean pre- and postoperative anterior CE angles were 42.4º±15.3 and 63.9º±12.1, respectively (p<0.001). Both CE angles were significantly improved. The correlation between pre- and postoperative acetabular coverage and postoperative ROM was evaluated. Postoperative abduction and internal rotation ROM were significantly associated with postoperative lateral CE angles (abduction; p < 0.001, internal rotation; p = 0.028); flexion and internal rotation ROM was significantly associated with postoperative anterior CE angles (flexion; p < 0.001, internal rotation; p = 0.028). Femoral anteversion was negatively correlated with postoperative abduction (p = 0.017) and external rotation (p = 0.047) ROM (Table 1). Postoperative abduction ROM was strongly positively correlated with femoral anteversion, whereas postoperative external rotation was strongly negatively correlated (Table 2). The total anteversion was strongly correlated with pre- or postoperative ROMs during flexion and internal rotation ROM (Table 2). Conclusion. Postoperativeanterior acetabular coverage may affect internal rotation ROM more than the lateral coverage. Therefore, the direction of acetabular reorientation should be carefully determined according to 3D alignment during PAO. For any figures or tables, please contact the authors directly

Adolescent and young adult patients with a history of DDH and residual hip dysplasia tend to have an early presentation of symptoms. In these patients, a severe acetabular dysplasia, aspheric femoral head and/or high greater trochanter are often observed. We evaluated the long-term results of rotational acetabular osteotomy (RAO) for symptomatic hip dysplasia in patients younger than 21 years. We performed 492 RAOs for hip dysplasia from 1987 to 2017. In these cases, patients younger than 21 years at the time of surgery were 40 patients (46 hips). We evaluated 34 patients (40 hips, follow-up rate; 85%) retrospectively. There were 32 females and two males; their mean age at the time of surgery was 17.8 years (12–21). The mean follow-up period was 16.8 years (1–30). In eight hips, isolated RAO was not adequate to correct instability and/or congruency. For these hips, four varus femoral osteotomies, two valgus femoral osteotomies and two greater trochanter displacement were combined with RAO. The mean clinical score (JOA) was improved from 80 to 90 significantly at the final follow-up. The mean CE angle was improved from −3.4 (−35–10) degrees to 27 (8–42) degrees, acetabular roof angle from 30 (15–60) degrees to 6.7 (−3–30) degrees, head lateralization index from 0.665 (0.5–1.0) to 0.614 (0.429–0.7) postoperatively. Radiographic OA progression was observed in four hips, but no hip was converted to THA. The RAO is an effective technique for surgical correction of a relatively severe dysplastic hip in adolescent and young adults

Objective. To investigate the biomechanical basis and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when treating developmental dysplasia of the hip (DDH). Methods. Biomechanical model of the hip joint was established on cadaveric hips. After performed ERAO on the biomechanical model, we explored the impact of this surgery on biomechanics of the hip joint. Meanwhile, we reported postoperative follow-up cases who underwent ERAO in our hospital between November 2007 to July 2012. A total of 14 patients (15 hips) were reported, including 4 males and 10 females, mean age was 30 years old. Harris hip score was defined as clinical evaluation standard and radiographic assessment was based on the measurement and further comparison of pre- and post-operative AHI (Acetabular-head index), CE angle (Center-edge angle) and Sharp angle. Results. The established biomechanical model was accord with the physiological state of normal hip joint. Postoperative stress was not statistically significant compared with the preoperative stress. Meanwhile, by the end of follow-up, 13 patients (14 hips) were followed for an average time of 26 months, thus, the follow-up rate was 92.9%. Harris hip score improved from preoperative (67.1 ± 8.7) points to (88.1 ± 7.3) points; postoperative AHI increased an average of 39.6%, CE angle increased an average of 33.2 ° and sharp angle reduced an average of 9.6 °. Conclusions. Both biomechanical study and preliminary clinical observation show that ERAO has the ability to correct the deformity of acetabulum. It enlarges the acetabular coverage of the femoral head and thus corrects the abnormal stress pattern. No bone graft is needed during the operation and postoperative rehabilitation is short, therefore, ERAO may have good curative effect when treating the DDH

Introduction. Pelvic osteotomy such as Chiari osteotomy and rotational acetabular osteotomy (RAO) have been used successfully in patients with developmental dysplasia of the hip (DDH). However, some patients are forced to undergo total hip arthroplasty (THA) because of the progression of osteoarthritis. THA after pelvic osteotomy is thought to be more difficult because of altered anatomy of the pelvis. We compared six THAs done in dysplastic hips after previous pelvic osteotomy between 2008 and 2015 with a well-matched control group of 20 primary procedures done during the same period. Materials and methods. Six THAs for DDH after previous Pelvic osteotomy (three Chiari osteotomies and three RAOs) were compared with 20 THAs for DDH without previous surgery. The patients were matched for age, sex, and BMI. Minimum follow-up for both groups of patients was one year (range, 12–79 months and 12–77 months, respectively). The average interval from pelvic osteotomy to total hip arthroplasty was 19.8 years (range 12–26 years). Clinical and Radiological evaluations were performed. Results. Both groups had similar short-term results except clinical score. There were no signiï¬ï¿½cant differences in range of motion, intraoperative blood loss and operative time between the two groups. There were no infections, dislocations, intraoperative fractures, damaged nerves, or deep vein thromboses in either group. Clinical score according to Japanese Orthopaedic Association rating system at the most recent follow-up were significantly lower in previous pelvic osteotomy group (P=0.003). Lower clinical score was assumed to be caused by one patient with previous Chiari osteotomy who had contralateral sciatic nerve palsy which was unrelated to the surgery. Although we were concerned about the failures on the acetabular side in patients with THA after pelvic osteotomy because of osteosclerotic acetabular bone, no acetabular component exhibited loosening or revision. This result supports the thought that the pelvic osteotomy fragment maintains its blood supply and allows porous acetabular components to ingrow. Conclusion. Pelvic osteotomies do not seem to compromise the short-term clinical or radiographic outcome

Objective. To investigate the biomechanical mechanism and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when conduct treatment for developmental dysplasia of the hip (DDH). Methods. Biomechanical model of the hip joint was established on six female cadaveric hips embalmed by formalin and stimulate ERAO was then performed on the model. Vertical force was loaded on the cadaveric spine from 0 N to 500 N and strain value on femoral head was measured preoperatively and postoperatively when loading force on spine reached the point of 100, 200, 300, 400 and 500 N. Stress value were then calculated base on the measurements. Besides, we reported postoperative follow up cases which were underwent ERAO to treat DDH in our hospital from July 2007 to October 2014. A total of 25 patients (26 hips) were reported, including 6 males and 19 females. Age varies from 11 to 57 years old, and the average age was 31 years old. Postoperative hip function was evaluated by Harris hip score and anteroposterior X⁃ray of pelvic was taken preoperatively and postoperatively to measure the Acetabular⁃head index (AHI), CE angle and Sharp angle. Results. Preoperative stress increased when loaded on spine became larger, but postoperative stress changed its increasing trend into decreasing when the load was greater than 300 N (turning point), which showed a parabolic trend. Compared with the preoperative stress under different load varying from 100 N to 500 N, postoperative stress was not statistically significant. Meanwhile, by the end of follow up period, 18 patients (19 hips) were followed form 7 to 85 months. The average follow up time was 40months and the follow up rate was 72%. Harris hip score improved from preoperative 64.3±7.2 points to 85.6±5.3 points; postoperative AHI increased an average of 36.5%, CE angle increased an average of 33.1° and sharp angle reduced an average of 12.3°. All differences between pre and post operative indexes were statistically significant. Conclusion. ERAO has the ability to correct the deformity of acetabulum. It enlarges the acetabular coverage of the femoral head and thus reduces the pressure of weight bearing area