Combined assessment of acetabular coverage and femoral head-neck shapes predicts osteoarthritis progression after periacetabular osteotomy.

INTRODUCTION: Postoperative osteoarthritis (OA) progression is a major determinant of failure after curved periacetabular osteotomy (CPO). A large postoperative combination angle, i.e., the combination of computed tomography-based anterior center edge and alpha angles, is associated with femoroacetabular impingement after CPO, but its association with postoperative OA progression is unclear. We aimed to identify the anatomical parameters that can lead to OA progression after CPO and the impact of the combination angle on the same. MATERIALS AND METHODS: We included 90 hips that were subjected to CPO at our center between March 2013 and March 2018. Seventeen hips showed OA progression with an increase in the Tönnis classification after surgery; 73 hips showed no progression. Radiographic anatomical parameters, including the lateral and anterior center edge angles, femoral and acetabular anteversion, and combination angle, and clinical outcomes, including modified Harris Hip Scores (mHHSs), postoperative anterior impingement, and range of motion, were compared between the two groups. Statistical significance was set at P < 0.05. RESULTS: Postoperative OA progression was significantly affected by preoperative OA evidence (P = 0.017), acetabular anteversion < 5.0° (P = 0.003), and a combination angle > 107.0° (P = 0.025). Patients with radiographic OA progression were associated with poor mHHSs (P = 0.017) and high frequencies of anterior impingement with a limited hip flexion and internal rotation angle. CONCLUSIONS: OA progression after CPO may be associated with preoperative evidence of OA and postoperative acetabular retroversion as well as a large combination angle. Surgeons should focus on the potential effects of preoperative OA grades, postoperative reduction in acetabular anteversion, and postoperative combination angle.

Periacetabular osteotomy using computed tomography-based navigation: preoperative planning and accuracy evaluation.

PURPOSE: Since 2011, we have used computed tomography (CT)-based navigation to perform safe and accurate rotational acetabular osteotomy (RAO) for treating developmental dysplasia of the hip. We developed a new method with four fiducial points to improve the accuracy of a published technique. In this study, we introduced a new method to achieve reorientation in accordance with planning and evaluated its accuracy. METHODS: This study included 40 joints, which underwent RAO used CT-based navigation. In 20 joints, reorientation was confirmed by touching the lateral aspect of the rotated fragment with navigation and checking whether it matched the preoperative plan. A new fiducial point method was adopted for the remaining 20 joints. To assess the accuracy of the position of the rotated fragment in each group, postoperative radial reformatted CT images were obtained around the acetabulum and three-dimensional evaluation was performed. The accuracy of acetabular fragment repositioning was evaluated using the acetabular sector angle (ASA). RESULTS: The absolute value of ΔASA, which represents the error between preoperative planning and the actual postoperative position, was significantly smaller in the new fiducial method group than the previous method group in the area from 11:30 to 13:30 (p < 0.05). The Harris Hip Score at 1 year after surgery did not differ significantly between the previous and new fiducial point methods. CONCLUSION: The new fiducial point method significantly reduced reorientation error in the superior-lateral area of the acetabulum: significantly fewer errors and fewer cases of under-correction of lateral acetabular coverage were recorded. The four-reference fiducial method facilitates reorientation of the acetabulum as planned, with fewer errors. The effect of the improved accuracy of the fiducial point method on clinical outcomes will be investigated in the future work.

Long-term course of developmental dysplasia of the hip: follow-up of the non-operated hips of patients undergoing unilateral rotational acetabular osteotomy for twenty-four years.

PURPOSE: To follow-up the non-operated hips of patients who underwent unilateral rotational acetabular osteotomy (RAO) for bilateral developmental dysplasia of the hip (DDH) for a minimum of 20 years to clarify (1) the timing of onset of hip osteoarthritis (OA) in DDH, and (2) factors associated with the development of OA. METHODS: This study included 92 non-operated hips of patients who underwent unilateral RAO for bilateral DDH. We examined the timing of OA onset and total hip arthroplasty (THA) and the joint survival rate in the studied hips. Furthermore, the patients were divided into those with OA onset (progression group) and those without OA onset and compared in terms of lateral center-edge angle (LCEA), sharp angle, acetabular head index (AHI), acetabular roof obliquity (ARO), joint congruity, and the presence or absence of OA progression on the RAO side. RESULTS: The progression group experienced OA onset 12 years after RAO and underwent THA 6 years after OA onset. The 20-year joint survival rate was 73% with the endpoint of OA onset and 81% with the endpoint of THA. The progression group had significantly smaller LCEA and AHI and larger ARO. The risk of developing OA was 8.2 times greater in patients with LCEA ≤ 7° than in those with LCEA > 7°. CONCLUSION: The patients with OA progression group experienced OA onset at an average age of 55 years. A small LCEA (≤ 7°) was identified as a risk factor for the development of OA.

Risk factors for lateralization or superiorization of the center of the femoral head in eccentric rotational acetabular osteotomy.

PURPOSE: This study aimed to clarify the factors that cause the lateralization and superiorization of the femoral head after eccentric rotational acetabular osteotomy (ERAO) by examining the three-dimensional morphology of the osteotomy site using computed tomography (CT). METHODS: This study included 52 patients who underwent ERAO for hip dysplasia. Postoperatively, the center of the femoral head was measured for lateralization and superiorization. We defined the iliac and sciatic osteotomy angles in the coronal and axial CT planes, respectively. The surgical factors for lateralization and superiorization were analysed using multiple logistic regression analysis. We also analysed the relationship between the femoral head relocation and clinical outcomes (as assessed using Japanese Orthopaedic Association (JOA) scores). RESULTS: Thirty-five patients had hips with lateralized femoral heads, and 25 patients' femoral heads were superiorized. Logistic regression analysis revealed that a higher osteotomy angle of the ilium in the coronal plane served as a significant predictor of superiorization of the femoral head. Similarly, a larger osteotomy angle of the ischium in the axial plane and the amount of change in the lateral centre edge angle were identified as predictors of lateralization. A weak negative correlation was observed between the amount of lateralization and the JOA score. CONCLUSION: Large osteotomy angles in the superior and posterior aspects of the acetabulum carry a risk of superiorization and lateralization of the center of the femoral head. Surgeons should be aware of the need to chisel through the internal plate to achieve the results described in the ERAO theory. STUDY DESIGN: A single-center, retrospective study.

Total hip arthroplasty after rotational acetabular osteotomy for developmental dysplasia of the hip: a retrospective observational study.

BACKGROUND: Total hip arthroplasty after osteotomy is more technically challenging than primary total hip arthroplasty, especially concerning cup placement. This is attributed to bone morphological abnormalities caused by acetabular bone loss and osteophyte formation. This study aimed to investigate the clinical and radiological outcomes of total hip arthroplasty after rotational acetabular osteotomy compared with those of primary total hip arthroplasty, focusing mainly on acetabular deformity and cup position. METHODS: The study included 22 hips that had undergone rotational acetabular osteotomy and 22 hips in an age- and sex-matched control group of patients who underwent total hip arthroplasties between 2005 and 2020. We analyzed cup abduction and anteversion; lateral, anterior, and posterior cup center-edge angle; hip joint center position; femoral anteversion angle; and presence of acetabular defect using postoperative radiography and computed tomography. Operative results and clinical evaluations were also analyzed. RESULTS: The clinical evaluation showed that the postoperative flexion range of motion was lower in total hip arthroplasty after rotational acetabular osteotomy than in primary total hip arthroplasty, although no significant difference was noted in the postoperative total Japanese Orthopedic Association hip score. The operative time was significantly longer in the rotational acetabular osteotomy group than in the control group, but there was no significant difference in blood loss. The lateral cup center-edge angle was significantly higher and the posterior cup center-edge angle was significantly lower in the total hip arthroplasty after rotational acetabular osteotomy, suggesting a posterior bone defect existed in the acetabulum. In total hip arthroplasty after rotational acetabular osteotomy, the hip joint center was located significantly superior and lateral to the primary total hip arthroplasty. CONCLUSIONS: In total hip arthroplasty after rotational acetabular osteotomy, the cup tended to be placed in the superior and lateral positions, where there was more bone volume. The deformity of the acetabulum and the high hip center should be considered for treatment success because they may cause cup instability, limited range of motion, and impingement.

Comparison between cup implantations during total hip arthroplasty with or without a history of rotational acetabular osteotomy.

INTRODUCTION: Total hip arthroplasty (THA) after rotational acetabular osteotomy (RAO) is technically demanding because of the characteristic acetabular morphology after RAO. The present study aimed to investigate the differences in the three-dimensional cup position between THA after RAO and primary THA. MATERIALS AND METHODS: We analysed the pre-operative and post-operative computed tomography (CT) data of 120 patients (20 patients after RAO and 100 patients without a history of RAO) who underwent THA between January 2017 and June 2018. We evaluated radiographic parameters, including acetabular anteversion, antero-posterior distance at the level of the femoral head centre, the presence of anterior acetabular osteophyte and/or rotated fragment during RAO from the CT data. Additionally, operative data and clinical scores were also evaluated. RESULTS: Although we found no significant differences in any clinical parameters, there were significant differences in radiographic parameters and operative data. The morphology of the acetabulum was significantly retroverted, and the antero-posterior distance was longer in patients after RAO, compared to the implanted cup. Additionally, longer operative time was necessary for such patients. These results reflect the atypical acetabular morphology after RAO, and emphasize that care should be taken to avoid anterior bony impingement and post-operative dislocation. CONCLUSION: For cup implantation during THA after RAO, surgeons should acknowledge the atypical morphology of the acetabulum and not be misled by its visual shape.

Preoperative T2 mapping MRI of articular cartilage values predicts postoperative osteoarthritis progression following rotational acetabular osteotomy.

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. METHODS: We reviewed 61 hips with early-stage OA in 61 patients who underwent RAO for DDH. They underwent preoperative and five-year postoperative radiological analysis of the hip. Those with a joint space narrowing of more than 1 mm were considered to have 'OA progression'. Preoperative assessment of articular cartilage was also performed using 3T MRI with the T2 mapping technique. The region of interest was defined as the weightbearing portion of the acetabulum and femoral head. RESULTS: There were 16 patients with postoperative OA progression. The T2 values of the centre to the anterolateral region of the acetabulum and femoral head in the OA progression cases were significantly higher than those in patients without OA progression. The preoperative T2 values in those regions were positively correlated with the narrowed joint space width. The receiver operating characteristic analysis revealed that the T2 value of the central portion in the acetabulum provided excellent discrimination, with OA progression patients having an area under the curve of 0.858. Furthermore, logistic regression analysis showed T2 values of the centre to the acetabulum's anterolateral portion as independent predictors of subsequent OA progression (p < 0.001). CONCLUSION: This was the first study to evaluate the relationship between intra-articular degeneration using T2 mapping MRI and postoperative OA progression. Our findings suggest that preoperative T2 values of the hip can be better prognostic factors for OA progression than radiological measures following RAO. Cite this article: Bone Joint J 2021;103-B(9):1472-1478.

Characteristics of three-dimensional acetabular morphology of patients with excellent outcome after rotational acetabular osteotomy over 20 years.

BACKGROUND: Rotational acetabular osteotomy (RAO) is a type of pelvic osteotomy performed to improve the acetabular bony coverage against the femoral head for patients with acetabular dysplasia. The acetabular bony coverage is ideally evaluated three-dimensionally; however, there is a paucity of published data regarding three-dimensional morphology in patients with long-term excellent outcome after RAO. The present study investigated the characteristics of three-dimensional acetabular morphology with long-term excellent outcome after RAO in comparison to patients with normal hip joints and those converted to total hip arthroplasty (THA) after RAO because of osteoarthritis (OA) progression. METHODS: Anteroposterior plain radiograph and computed tomography data of 57 hip joints (17 joints with excellent outcome 20 years or more after RAO, 16 normal joints, and 20 joints converted to THA after RAO) were analyzed. The two-dimensional lateral center-edge (CE) angle from plain radiographs and acetabular anteversion, anterior acetabular sector angle, and posterior sector angle from computed tomography (CT) images were calculated. RESULTS: Compared with patients converted to THA, all parameters in patients with long-term excellent outcome after RAO were similar to those in patients with normal hip joints, particularly in the three-dimensional analyses. The anterior bony coverage was excessive, whereas the posterior bony coverage was deficient in patients converted to THA after RAO. Anterior bony impingement and posterior instability may be the cause of OA progression after RAO. CONCLUSION: Caution must be taken to avoid rotating the separated fragment excessively to the anterior direction during RAO to prevent OA progression and achieve long-term excellent outcome.

Incidence and determinants of anteflexion impairment after rotational acetabular osteotomy.

This study aimed to identify the incidence of anteflexion impairment after rotational acetabular osteotomy based on patient-reported outcome measures, and the morphological factors and postoperative bony range of motion associated with anteflexion impairment at 2 years postoperatively. We analyzed 26 patients with developmental dysplasia of the hip who underwent rotational acetabular osteotomy at our institution. Using questionnaires, we defined anteflexion impairment as difficulty in clipping toenails and pulling up and removing socks. Morphological parameters and bony range of motion measured using a postoperative three-dimensional surface model, were compared between the subjects with and without anteflexion impairment. The incidence of anteflexion impairment was 69% at 6 months, 35% at 1 year, and 12% at 2 years after rotational acetabular osteotomy. The mean bony flexion angle was smaller in subjects with impairment than in those without impairment. The mean internal rotation (IR) angle at 90° of flexion was smaller in subjects with impairment than in those without impairment. The incidence of impairment was significantly higher in subjects with both less than or equal to 105° of bony flexion and less than or equal to 20° of IR at 90° of flexion than in the remaining subjects. No significant difference was observed in postoperative femoral head coverage and preoperative morphological parameters including spinal condition between the two groups. To prevent femoroacetabular impingement after rotational acetabular osteotomy, surgeons need to reorient the acetabulum to restore postoperative bony flexion to more than or equal to 105° and/or postoperative IR range of motion to more than or equal to 20° at 90° of flexion.

Long-Term Outcomes of Eccentric Rotational Acetabular Osteotomy Combined With Femoral Osteotomy for Hip Dysplasia.

BACKGROUND: This study aimed at investigating the clinical outcomes of eccentric rotational acetabular osteotomy (ERAO) combined with intertrochanteric valgus osteotomy (ITVO) over a period of more than 10 years. METHODS: This is a case-control study of 39 patients (40 hips) who underwent ERAO combined with ITVO for hip dysplasia (ITVO group). Patients were matched for age, sex, follow-up period, and preoperative joint stage to 78 patients (80 hips) who underwent ERAO alone (ERAO group). We compared the clinical and radiographic outcomes and the survival rates between the groups. RESULTS: The Harris Hip Score at the final follow-up was significantly lower in the ITVO group than in the ERAO group. The postoperative center edge angle, acetabular head index, and minimum joint space were significantly smaller in the ITVO group than in the ERAO group. The survival rates for the conversion to total hip arthroplasty end point were not significantly different between groups. However, survival rates for the Harris Hip Score < 80 end point were significantly poorer in the ITVO group than in the ERAO group. CONCLUSION: The long-term results of ERAO combined with ITVO were not satisfactory from a hip function perspective. ERAO combined with ITVO should be indicated in only young active patients with pre-osteoarthritis and initial stages of osteoarthritis.

Changes in muscle strength of the hip after rotational acetabular osteotomy: a retrospective study.

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. PATIENTS AND METHODS: A total of 57 patients underwent RAO for acetabular dysplasia. Changes in muscle strength of the operated hip, 10 m gait speed, Japanese Orthopaedic Association (JOA) hip score, and factors correlated with hip muscle strength after RAO were retrospectively analyzed. RESULTS: Three months postoperatively, the strength of the operated hip in flexion and abduction and gait speed had decreased from their preoperative levels. After six months, the strength of flexion and abduction had recovered to their preoperative level, as had gait speed. At one-year follow-up, significant improvements were seen in the strength of hip abduction and gait speed, but muscle strength in hip flexion remained at the preoperative level. The mean JOA score for hip function was 91.4 (51 to 100)) at one-year follow-up. Body mass index (BMI) showed a negative correlation with both strength of hip flexion (r = -0.4203) and abduction (r = -0.4589) one year after RAO. Although weak negative correlations were detected between strength of hip flexion one year after surgery and age (r = -0.2755) and centre-edge (CE) angle (r = -0.2989), no correlation was found between the strength of abduction and age and radiological evaluations of CE angle and acetabular roof obliquity (ARO). CONCLUSION: Hip muscle strength and gait speed had recovered to their preoperative levels six months after RAO. The clinical outcome at one year was excellent, although the strength of hip flexion did not improve to the same degree as that of hip abduction and gait speed. A higher BMI may result in poorer recovery of hip muscle strength after RAO. Radiologically, acetabular coverage did not affect the recovery of hip muscle strength at one year's follow-up. A more intensive rehabilitation programme may improve this. Cite this article: Bone Joint J 2019;101-B:1459-1463.

Failed periacetabular osteotomy leads to acetabular defects during subsequent total hip arthroplasty.

BACKGROUND: Acetabular wall defects after periacetabular osteotomy (PAO) lead to technical difficulties when performing subsequent total hip arthroplasty (THA). There is no unified consensus regarding the solution for THA socket installation after PAO. In the current study, we performed computed tomography (CT)-based simulation of socket installation and evaluated the acetabular defect following THA after PAO and after primary osteoarthritis (OA). PATIENTS AND METHODS: The study group comprised 55 patients (56 hips) who underwent THA after PAO. For the control group, after matching for age, sex, and Crowe classification, we included 55 patients (56 hips) who underwent primary THA for hip dysplasia. We evaluated the anterior, posterior, and superior acetabular sector angle (ASA) and medial wall thickness (MWT) at the anatomical hip center (at the 20-mm vertical hip level from teardrop) in the study group (anatomical PAO group) and control group (primary OA group). In addition, we investigated the changes in the socket covering when the socket was positioned 10 mm above the anatomical hip center (30 mm above the teardrop; elevated osteotomy group). RESULTS: All ASA and MWT values were significantly smaller in the anatomical PAO group than in the primary OA group. In particular, the individuals with a Crowe classification of II/III in the anatomical PAO group presented severe acetabular defects. However, the elevated PAO group had a significantly larger ASA compared to the anatomical PAO group, with improved socket coverings. CONCLUSION: Acetabular defects in the anatomical hip center following THA after PAO were significantly common compared to those after primary THA. Elevation of hip joint centers as much as 10 mm is one therapeutic option in the case of severe acetabular defects following THA after PAO.

Computer-assisted anteverting eccentric rotational acetabular osteotomy for recurrent posterior dislocation associated with acetabular retroversion: a case report.

BACKGROUND: Acetabular retroversion is a rotatory abnormality of the entire hemipelvis that includes anterior over-coverage and posterior deficiency of the acetabulum, and is associated with pincer-type femoroacetabular impingement and posterior hip instability. Acetabular retroversion is thought to cause posterior dislocation of the hip in athletes due to both the pincer-type femoroacetabular impingement and posterior hip instability. CASE PRESENTATION: A 26-year-old Japanese man had acetabular retroversion that induced recurrent posterior dislocation of his hip due to excessive hip flexion while wakeboarding. We performed anteverting eccentric rotational acetabular osteotomy using preoperative three-dimensional planning and an intraoperative computerized navigation system. Our patient was able to return to sports activities 1 year postoperatively. CONCLUSIONS: Both preoperative three-dimensional surgical planning software and an intraoperative navigation system can provide a highly accurate map for this complicated surgery that simultaneously improves the pincer-type femoroacetabular impingement and posterior deficiency of the acetabulum.

Radiographic Progression of Osteoarthritis after Rotational Acetabular Osteotomy: Minimum 10-Year Follow-up Outcome According to the Tönnis Grade.

BACKGROUND: Although satisfactory mid- to long-term results of rotational acetabular osteotomy for early osteoarthritis secondary to acetabular dysplasia have been reported, there is still controversy about the long-term effects of this surgery in more advanced osteoarthritis. The purpose of this study was to investigate the radiographic progression of osteoarthritic changes after rotational acetabular osteotomy in acetabular dysplasia according to the preoperative Tönnis grade and evaluate its effects after minimum 10-year follow-up. METHODS: We performed 71 consecutive rotational acetabular osteotomies in 64 patients with symptomatic acetabular dysplasia between November 1984 and April 2005. Of these, 46 hips (four hips with Tönnis grade 0, 30 with grade 1, and 12 with grade 2) whose clinical and radiographic findings were available after minimum 10-year follow-up were evaluated in this study. The mean age at the time of surgery was 39.0 years (range, 18 to 62 years) and the average follow-up duration was 17.3 years (range, 10.0 to 27.7 years). Clinical and radiographic evaluations were performed according to the preoperative Tönnis grade. RESULTS: The average Harris hip score improved from 71.8 (range, 58 to 89) to 85.1 (range, 62 to 98). The radiographic parameters also improved in all Tönnis grades after the index surgery. Although the improvement of radiographic parameters was not different between preoperative Tönnis grades, the incidence of osteoarthritic progression was significantly different between grades (zero in Tönnis grade 0, four in Tönnis grade 1, and 10 in Tönnis grade 2; p < 0.001). The mean age at the time of surgery was also significantly older in osteoarthritic progression patients (p < 0.002). Kaplan-Meier survivorship analysis, with radiographic progression of osteoarthritis as the endpoint, predicted a 10-year survival rate of 100% in Tönnis grade 0, 85.7% in Tönnis grade 1, and 14.3% in Tönnis grade 2 (p < 0.001). CONCLUSIONS: The outcome of rotational acetabular osteotomy in most hips with Tönnis grade 0 and 1 was satisfactory after an average of 17 years of follow-up. The incidence of osteoarthritic progression was higher in Tönnis grade 2 and older age. Our results support that early joint preserving procedure is essential in the case of symptomatic dysplastic hips.

Evaluation of articular cartilage following rotational acetabular osteotomy for hip dysplasia using T2 mapping MRI.

BACKGROUND: Rotational acetabular osteotomy (RAO) is one of the surgical treatments for acetabular dysplasia, and satisfactory results have been reported. We evaluated the postoperative changes of articular cartilage and whether the pre-operative condition of the articular cartilage influences the clinical results using T2 mapping MRI. METHODS: We reviewed 31 hips with early stage osteoarthritis in 31 patients (mean age, 39.6 years), including three men and 28 women who underwent RAO for hip dysplasia. Clinical evaluations including Japanese Orthopedic Association (JOA) score and Japanese Orthopedic Association Hip Disease Evaluation Questionnaire (JHEQ), and radiographical evaluations on X-ray were performed. Longitudinal qualitative assessment of articular cartilage was also performed using 3.0-T MRI with T2 mapping technique preoperatively, 6 months, and at 1 and 2 years postoperatively. RESULTS: There was no case with progression of osteoarthritis. The mean JOA score improved from 70.1 to 93.4 points, the mean postoperative JHEQ score was 68.8 points, and radiographical data also improved postoperatively. We found that the T2 values of the cartilage at both femoral head and acetabulum increased at 6 months on coronal and sagittal views. However, they significantly decreased 1 and 2 years postoperatively. The T2 values of the center to anterolateral region of acetabulum negatively correlated with postoperative JHEQ score, particularly in pain score. CONCLUSIONS: This study suggests that biomechanical and anatomical changes could apparently cause decreased T2 values 1-2 years postoperatively compared with those preoperatively. Furthermore, preoperative T2 values of the acetabulum can be prognostic factors for the clinical results of RAO.

Evaluation of the three-dimensional bony coverage before and after rotational acetabular osteotomy.

PURPOSE: Rotational acetabular osteotomy is a type of pelvic osteotomy that involves rotation of the acetabular bone to improve the bony coverage of the femoral head for patients with acetabular dysplasia. Favourable post-operative long-term outcomes have been reported in previous studies. However, there is a paucity of published data regarding three-dimensional bony coverage. The present study investigated the three-dimensional bony coverage of the acetabulum covering the femoral head in hips before and after rotational acetabular osteotomy and in normal hips. METHODS: The computed tomography data of 40 hip joints (12 joints before and after rotational acetabular osteotomy; 16 normal joints) were analyzed. The three-dimensional bony coverage of each joint was evaluated using original software. RESULTS: The post-operative bony coverage improved significantly compared with pre-operative values. In particular, the anterolateral aspect of the acetabulum tended to be dysplastic in patients with acetabular dysplasia compared to those with normal hip joints. However, greater bony coverage at the anterolateral aspect was obtained after rotational acetabular osteotomy. Meanwhile, the results of the present study may indicate that the bony coverage in the anterior aspect may be excessive. CONCLUSION: Three-dimensional analysis indicated that rotational acetabular osteotomy achieved favorable bony coverage. Further investigations are necessary to determine the ideal bony coverage after rotational acetabular osteotomy.

Morphological variation of the anterior inferior iliac spine affects hip range of motion in flexion after rotational acetabular osteotomy.

PURPOSE: Reduced range of motion (ROM) in flexion and internal rotation are associated with impaired activities of daily living (ADL) after rotational acetabular osteotomy (RAO). This study focused on the morphological variation of the anterior inferior iliac spine in developmental dysplasia of the hip (DDH) and its impact on post-operative bony ROM after RAO. This study aimed to investigate the association between bony ROM after RAO and pre-operative morphological factors of the pelvis and femur, including a positional variation of the anterior inferior iliac spine. METHODS: Bony ROM in 52 patients with DDH was assessed after virtual RAO using computed tomography (CT). Post-operative acetabular coverage was set at lateral and anterior centre-edge angles of 30° and 55°, respectively. The position of the anterior inferior iliac spine was classified as higher or lower. RESULTS: Multiple regression analysis revealed that the lower anterior inferior iliac spine and higher femoral neck shaft angle were significantly associated with the lower flexion angle after RAO. Lower femoral anteversion, higher femoral neck shaft angle and higher alpha angle at the anterosuperior part were significantly associated with lower internal rotation angle at 90° flexion after RAO. CONCLUSION: Therefore, morphological variation of the anterior inferior iliac spine affected bony ROM in flexion and that of the femoral neck affected bony ROM in internal rotation at flexion after RAO.

Radiographic Progression of Osteoarthritis after Rotational Acetabular Osteotomy: Minimum 10-Year Follow-up Outcome According to the Tönnis Grade

BACKGROUND: Although satisfactory mid- to long-term results of rotational acetabular osteotomy for early osteoarthritis secondary to acetabular dysplasia have been reported, there is still controversy about the long-term effects of this surgery in more advanced osteoarthritis. The purpose of this study was to investigate the radiographic progression of osteoarthritic changes after rotational acetabular osteotomy in acetabular dysplasia according to the preoperative Tönnis grade and evaluate its effects after minimum 10-year follow-up. METHODS: We performed 71 consecutive rotational acetabular osteotomies in 64 patients with symptomatic acetabular dysplasia between November 1984 and April 2005. Of these, 46 hips (four hips with Tönnis grade 0, 30 with grade 1, and 12 with grade 2) whose clinical and radiographic findings were available after minimum 10-year follow-up were evaluated in this study. The mean age at the time of surgery was 39.0 years (range, 18 to 62 years) and the average follow-up duration was 17.3 years (range, 10.0 to 27.7 years). Clinical and radiographic evaluations were performed according to the preoperative Tönnis grade. RESULTS: The average Harris hip score improved from 71.8 (range, 58 to 89) to 85.1 (range, 62 to 98). The radiographic parameters also improved in all Tönnis grades after the index surgery. Although the improvement of radiographic parameters was not different between preoperative Tönnis grades, the incidence of osteoarthritic progression was significantly different between grades (zero in Tönnis grade 0, four in Tönnis grade 1, and 10 in Tönnis grade 2; p < 0.001). The mean age at the time of surgery was also significantly older in osteoarthritic progression patients (p < 0.002). Kaplan-Meier survivorship analysis, with radiographic progression of osteoarthritis as the endpoint, predicted a 10-year survival rate of 100% in Tönnis grade 0, 85.7% in Tönnis grade 1, and 14.3% in Tönnis grade 2 (p < 0.001). CONCLUSIONS: The outcome of rotational acetabular osteotomy in most hips with Tönnis grade 0 and 1 was satisfactory after an average of 17 years of follow-up. The incidence of osteoarthritic progression was higher in Tönnis grade 2 and older age. Our results support that early joint preserving procedure is essential in the case of symptomatic dysplastic hips.

Ten-year survival rate after rotational acetabular osteotomy in adulthood hip dysplasia.

BACKGROUND: Rotational acetabular osteotomy (RAO) is an effective joint-preserving surgical treatment for adulthood hip dysplasia (AHD). Despite sufficient correction of acetabular dysplasia, some patients still experience osteoarthritis (OA) progression and require total hip arthroplasty (THA). The purposes of the current study were to investigate the survival rate and the risk factors for OA progression or THA requirement after RAO and to explore whether acetabular overcorrection relates to OA progression. METHODS: Fifty-six patients (65 hips, mean age: 36.5 ± 11.7 years) with AHD who underwent RAO and were followed up for >10 years (mean: 15.0 ± 3.2 years) were enrolled in this study. A Kaplan-Meier survival analysis was performed to assess the non-OA progression rate and THA-free survival rate of RAO during the 10-year follow-up. To analyze the risk factors for OA progression and THA requirement, the Cox proportional hazards regression analysis was performed. RESULTS: No OA progression was found in 76.7% of the patients, and THA was not required in 92.3% during the 10-year follow-up. By multivariate regression analysis, older age at the time of surgery was a risk factor for both OA progression (hazard ratio [HR] = 1.047, 95% confidence interval [CI] = 1.005-1.091) and THA requirement (HR = 1.293, 95% CI = 1.041-1.606). CONCLUSION: RAO is an effective surgical procedure for symptomatic patients with AHD that prevents OA progression and protects the hips from undergoing THA. However, older patients have a higher risk for both OA progression and THA requirement.

Long-term results of rotational acetabular osteotomy for osteonecrosis with collapse of the femoral head in young patients.

PURPOSE: The surgical treatment of osteonecrosis with collapse of the femoral head is still controversial. The purpose of this study was to investigate the clinical outcome of rotational acetabular osteotomy by Ninomiya and Tagawa for osteonecrosis of the femoral head in young patients. PATIENTS AND METHODS: Rotational acetabular osteotomy was performed in 202 consecutive patients between 1995 and 2003. Among them, rotational acetabular osteotomy with osteonecrosis of the femoral head was performed in 31 patients (42 hips). The mean age at the time of surgery was 31.2 years (range 16-45). The mean duration of follow-up was 16.1 years (range 13.1-21 years). RESULTS: The mean preoperative Japanese Orthopedic Association hip score of 56.8 points improved to a mean of 72.4 points at the final follow-up. The 10-year survival rate with conversion to total hip arthroplasty as an end-point was 91.9%, and the 15-year survival rate was 75.5%, the 20-year survival rate was 67.9%. The conversion to total hip arthroplasty was performed in nine hips. The average time to the conversion to total hip arthroplasty was 12.1 years. CONCLUSIONS: Even though the necrotized range is wide, if normal cartilage remains on the lateral side of the femoral head, it can be utilized for the weight-bearing region by laterally rotating the acetabulum. Since the outcome was favorable, we believe that this is a valuable treatment option for this disease.