Tumor-induced osteomalacia caused by a massive phosphaturic mesenchymal tumor of the acetabulum: A case report.

We report a case of tumor-induced osteomalacia (TIO) caused by a massive phosphaturic mesenchymal tumor (PMT) of the acetabulum. A 68-year-old woman presented with progressive bone pain of the rib cage, and polyarthralgia and back pain for 3 years. She was diagnosed with hypophosphatemic osteomalacia because laboratory testing was remarkable for low serum phosphorus and a low level of 1,25(OH)2 vitamin D. Three years later, her hip radiograph revealed an osteolytic lesion of the acetabulum. Magnetic resonance imaging of the acetabulum showed a massive lesion. Laboratory data showed hypophosphatemia and an elevated serum level of fibroblast growth factor 23 (FGF-23). Samples obtained with open biopsy showed a low-grade spindle cell neoplasm with FGF-23 positivity, identified by using immunohistochemical staining, confirming the diagnosis of a PMT mixed connective tissue variant. Curettage of the tumor was performed, and the defects were filled with bone allografts. The hip joint was reconstructed with total hip arthroplasty using a Muller support ring. To our knowledge, this report represents the first documented case of massive PMT of the acetabulum causing TIO.

Cementless total hip arthroplasty for patients previously treated with femoral osteotomy for hip dysplasia: the incidence of periprosthetic fracture.

PURPOSE: Femur deformities can make stem fixation difficult in total hip arthroplasty (THA). We report the clinical results of cementless THA using a press-fit stem in patients who had previously undergone femoral osteotomy for hip dysplasia. METHODS: The subjects included 66 hips in 64 patients, with the mean follow-up period of 7.3 years. THA was performed at a mean period of 17.1 years after intertrochanteric femoral osteotomy. Valgus osteotomy was performed in 42 hips, and varus osteotomy in 24. Clinical results were evaluated by using the Merle d'Aubigne-Postel score. Implant survival was determined with revision as the end point, and any related complications were investigated. RESULTS: The Merle d'Aubigne-Postel score improved from 9.4 to 16.1 at the final follow-up, without any implant loosening. However, periprosthetic femoral fractures were observed in four hips (6.0 %), one intra-operatively and three within three weeks after THA. Among these cases, three hips previously had varus osteotomy (12.5 %) and one hip had valgus osteotomy (2.3 %). Two hips were revised with full porous stems and circumferential wiring. The five and ten year cumulative survivorship rates were 97 % (range, 88.8-99.3 %) and 97 % (88.8-99.3 %), respectively. CONCLUSIONS: Although the use of a press-fit cementless stem yielded acceptable results in most of the patients, perioperative femoral fracture was a major complication especially in the patients previously treated with intertrochanteric varus osteotomy. Careful planning and implant selection could be emphasized for these cases.

Dislocation and its recurrence after revision total hip arthroplasty.

PURPOSE: Dislocation is a leading cause of failure after revision total hip arthroplasty (THA). This study was conducted to examine the risk factors for dislocation as well as their recurrence after revision THA. METHODS: We retrospectively reviewed 178 revision THAs in 162 patients between 1998 and 2013. The mean patient age was 65.2 years at operation and the mean follow-up period was 6.7 years. Multivariate logistic regression was performed to identify risk factors for dislocation, and further comparison was made between patients with single and recurrent dislocations. RESULTS: Sixteen hips in 15 patients (9.0 %) dislocated at a mean of 9.1 months (range, 0-83 months) after revision THA. Multivariate analysis identified advanced age (odds ratio [OR] = 2.94/10 years) and osteonecrosis of the femoral head (OR = 7.71) as the independent risk factors for any dislocations. Risk factors for recurrent dislocations, which were observed in eight hips (50 %), were later dislocations (≥4 months) and lower BMI. CONCLUSION: Dislocation is a serious problem after revision THA with multiple risk factors. Although our findings were limited to revision THAs done through posterolateral approach, recognition of these factors is helpful in patient education and surgical planning.

Delayed diagnosis of ankylosing spondylitis in a Japanese population.

OBJECTIVES: This study was conducted to evaluate the period from symptom onset to diagnosis of ankylosing spondylitis (AS) in Japanese patients and to examine possible reasons for delayed diagnosis. METHODS: Seventy-two consecutive patients with AS were studied. Diagnostic delay was defined as the gap between the first spondyloarthropathic symptom and diagnosis of AS according to the modified New York criteria. RESULTS: The mean patient ages at disease onset and diagnosis were 25.6 ± 11.3 and 33.3 ± 13.2 years old, respectively, resulting in diagnostic delay of 6.7 years. The number of medical institutions to which patients were referred before diagnosis was 2.4, and orthopedic surgeons were most commonly visited (62%). Non-specific low back pain or lumbar spondylitis (33%) and degenerative arthritis (28%) were the primary diagnoses preceding that of AS. Absence of articular symptoms significantly correlated with diagnostic delay. The patients with disease onset on year 2000 or later had significantly shorter periods until diagnosis than those before 2000 (3.6 vs. 7.5 years). CONCLUSIONS: The present study showed a marked diagnostic delay among Japanese patients with AS. Although it has been improved, continuing medical education focusing on inflammatory back pain in adolescent is required for early diagnosis of AS.

Pelvic tilt and movement during total hip arthroplasty in the lateral decubitus position.

OBJECTIVES: Total hip arthroplasty (THA) is often performed in the lateral decubitus (lateral) position. In this position, the pelvis may have various degrees of tilt leading to implant malposition. We sought to quantify the pelvic tilt in lateral position and further pelvic movement during surgery. METHODS: In 95 cases with primary THA, three-dimensional pelvic tilts were quantified by superimposing images reconstructed from CT data onto antero-posterior radiographs taken in lateral position at set-up and after cup placement. Pelvises were fixed with a device compressing anterior superior iliac spines and sacrum. RESULTS: Various degrees of pelvic tilt occurred compared to the supine position; sagittal: -3.1° (-25.5° to 10.2°), axial: 3.9° (-8.4° to 17°), coronal: 0.9° (-11.9° to 13.2°). Absolute changes more than 5° were observed 43%, 47%, and 12% in the sagittal, axial, and coronal planes, respectively. The more preoperative posterior pelvic tilt resulted in the more change in the sagittal plane. Further pelvic movement of about 3° in three planes were observed ranging from -11° to 20° after cup placement. CONCLUSION: This study showed various pelvic tilt and movement during THA. As pelvic tilt directly alters the cup orientation, its changes should be well understood. Improved tools for positioning and holding the pelvis are required.

Rapidly destructive arthrosis of the hip joint in a young adult with systemic lupus erythematosus.

A 37-year-old female had been treated with corticosteroids for systemic lupus erythematosus clinically diagnosed at age 10. She suddenly had right hip pain without any antecedent trauma. Four months after the onset of pain, she visited her primary care physician. On magnetic resonance imaging, joint space narrowing at the weight-bearing area was already seen with bone marrow edematous lesions in both the femoral head and acetabulum. She was treated non-operatively; however, her pain continued to worsen in severity. Thirteen months after the onset of pain, she was referred to our hospital. A plain radiograph showed subluxation of the collapsed femoral head accompanied by destruction of the acetabular rim. Because of her severe intractable pain, she underwent total hip arthroplasty 1 month after her first visit. Histological examination of the resected femoral head revealed pseudogranulomatous lesions along with prominent callus formation, suggesting rapid destruction of the femoral head.

Efficacy and Safety of Infliximab for Ankylosing Spondylitis in Japanese Patients: A Retrospective Study of 11 Cases.

PURPOSE: Tumor necrosis factor inhibitors (TNFi) such as infliximab (IFX) and adalimumab have been shown to be efficacious not only for rheumatoid arthritis but also for Ankylosing Spondylitis (AS). However, only a limited number of reports regarding the effect of TNFi on AS in Japanese population have been published. MATERIALS AND METHODS: We retrospectively evaluated all 11 patients (8 males and 3 females) with AS who were treated with IFX. RESULTS: After a mean follow-up period of 19 months, the mean BASDAI decreased from 4.7 ± 2.2 to 1.7 ± 1.2 and the serum CRP level decreased from 1.62 ± 1.94 mg/dl to 0.23 ± 0.45 mg/dl. There was no case of serious infection or anaphylaxis. CONCLUSIONS: Our results indicate that IFX is efficacious and safe for AS in Japanese patients.

Ischio-pubic stress fracture after peri-acetabular osteotomy in patients with hip dysplasia.

PURPOSE: Ischio-pubic stress fracture is one of the potential complications after peri-acetabular osteotomy (PAO) in patients with hip dysplasia. The purpose of this study was to examine the prevalence of and risk factors for ischio-pubic fractures following PAO. METHODS: A total of 296 hips in 275 patients who underwent transposition osteotomy of the acetabulum between 2001 and 2012 were retrospectively reviewed. Patient characteristics and radiographic parameters were compared between patients with and without fracture. RESULTS: Fourteen ipsilateral hips (4.7%) in 14 female patients had fracture of the inferior pubic ramus (11 hips) or the ischial ramus (three hips) on the same side as the surgery at an average of 4.6 weeks after PAO. Multivariate analysis indicated that younger age at operation (odds ratio of 1.43 per five years, p = 0.0169) and greater degree of correction (odds ratio of 1.98 per five degrees, p = 0.0005) were significantly associated with ischio-pubic fracture as independent risk factors. All fractures healed conservatively with partial weight-bearing. CONCLUSIONS: Younger female patients and greater deformity corrections increased the risk of ischio-pubic stress fracture after PAO.

Influencing factors for the increased stem version compared to the native femur in cementless total hip arthroplasty.

PURPOSE: Stem version is not always equivalent to femoral neck version (native version) in cementless total hip arthroplasty (THA). We therefore examined the discrepancy of version between the native femoral neck and stem using pre- and postoperative computed tomography (CT), the level of the femur where the canal version most closely fit the stem version, and the factors influencing version discrepancy between the native femoral neck and stem. METHODS: A total of 122 hips in 122 patients who underwent primary THA using a metaphyseal-fit stem through the postero-lateral approach were included. Pre- and postoperative CT images were utilized to measure native and stem version, and the version of the femoral canal at four levels relative to the lesser trochanter. RESULTS: The mean native and stem versions were 28.1 ± 11.0° and 38.0 ± 11.2°, respectively, revealing increased stem version with a mean difference of 9.8° (p < 0.0001). A total of 84 hips (68.9 %) revealed an increase in version greater than 5°. Femoral canal version at the level of the lesser trochanter most closely approximated that of stem version. Among the factors analysed, both univariate and multivariate analysis showed that greater degrees of native version and anterior stem tilt significantly reduced the version discrepancy between the native femoral neck and stem version. CONCLUSIONS: Since a cementless stem has little version adjustability in the femoral canal, these findings are useful for surgeons in preoperative planning and to achieve proper component placement in THA.

Subclinical bilateral involvement of the hip in patients with slipped capital femoral epiphysis: a multicentre study.

PURPOSE: This study was conducted to assess the posterior inclination of the contralateral femoral epiphysis in patients with unilateral slipped capital femoral epiphysis (SCFE). METHODS: The posterior sloping angle (PSA) was measured using lateral radiographs in 67 patients with a unilateral SCFE and in 41 age-matched normal controls. A symptomatic epiphyseal slip was defined as the development of SCFE. RESULTS: The contralateral PSA in SCFE patients was more widely distributed and significantly larger compared to controls (15.0° vs. 9.0°, p < 0.0001). Forty-seven hips (70.1%) had a PSA of greater than 12.8°, which was +2SD of the control hips. Of the 65 hips excluding the two cases with prophylactic pinning, 11 hips (16.9%) eventually developed a contralateral SCFE during adolescence and their PSA at the initial visit was significantly larger compared to patients without a contralateral SCFE (18.0° vs. 14.3°, p < 0.005) with a cutoff value of 19°. CONCLUSIONS: These findings suggested the possibility of bilateral hip involvement in SCFE patients. Hips with greater degrees of PSA (> 19°) are likely to become symptomatic.

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty.

PURPOSE: The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup. METHODS: We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(-)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips. RESULTS: One hip (0.4%) had a dislocation in the CA(+) group, whereas ten hips (2.5%) had a dislocation in the CA(-) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(-) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0%) achieved the intended CA. CONCLUSIONS: Although the manual placement of the cup resulted in 27% of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.

A novel population of cells expressing both hematopoietic and mesenchymal markers is present in the normal adult bone marrow and is augmented in a murine model of marrow fibrosis.

Bone marrow (BM) fibrosis is a feature of severe hyperparathyroidism. Consistent with this observation, mice expressing constitutively active parathyroid hormone (PTH)/PTH-related peptide receptors (PPR) in osteoblasts (PPR*Tg) display BM fibrosis. To obtain insight into the nature of BM fibrosis in such a model, a double-mutant mouse expressing constitutively active PPR and green fluorescent protein (GFP) under the control of the type I collagen promoter (PPR*Tg/GFP) was generated. Confocal microscopy and flow cytometry revealed the presence of a cell population expressing GFP (GFP(+)) that was also positive for the hematopoietic marker CD45 in the BM of both PPR*Tg/GFP and control animals. This cell population was expanded in PPR*Tg/GFP. The existence of cells expressing both type I collagen and CD45 in the adult BM was confirmed by IHC and fluorescence-activated cell sorting. An analysis of total RNA extracted from sorted GFP(+)CD45(+) cells showed that these cells produced type I collagen and PTH/PTH-related peptide receptor and receptor activator for NF-κB mRNAs, further supporting their features of being both mesenchymal and hematopoietic lineages. Similar cells, known as fibrocytes, are also present in pathological fibroses. Our findings, thus, indicate that the BM is a permissive microenvironment for the differentiation of fibrocyte-like cells and raise the possibility that these cells could contribute to the pathogenesis of BM fibrosis.

The JAK inhibitor tofacitinib regulates synovitis through inhibition of interferon-γ and interleukin-17 production by human CD4+ T cells.

OBJECTIVE: Tofacitinib (CP-690,550) is a novel JAK inhibitor that is currently in clinical trials for the treatment of rheumatoid arthritis (RA). The aim of this study was to examine the effects of tofacitinib in vitro and in vivo in RA, in order to elucidate the role of JAK in the disease process. METHODS: CD4+ T cells, CD14+ monocytes, and synovial fibroblasts (SFs) were purified from the synovium and peripheral blood of patients with RA and were evaluated for the effect of tofacitinib on cytokine production and cell proliferation. For in vivo analysis, synovium and cartilage samples obtained from patients with RA were implanted in immunodeficient mice (SCID-HuRAg mice), and tofacitinib was administered via an osmotic minipump. RESULTS: Tofacitinib treatment of CD4+ T cells originating from synovium and peripheral blood inhibited the production of interleukin-17 (IL-17) and interferon-γ (IFNγ) in a dose-dependent manner, affecting both proliferation and transcription, but had no effect on IL-6 and IL-8 production. Tofacitinib did not affect IL-6 and IL-8 production by RASFs and CD14+ monocytes. However, conditioned medium from CD4+ T cells cultured with tofacitinib inhibited IL-6 production by RASFs and IL-8 production by CD14+ monocytes. Treatment of SCID-HuRAg mice with tofacitinib decreased serum levels of human IL-6 and IL-8 and markedly suppressed invasion of synovial tissue into cartilage. CONCLUSION: Tofacitinib directly suppressed the production of IL-17 and IFNγ and the proliferation of CD4+ T cells, resulting in inhibition of IL-6 production by RASFs and IL-8 production by CD14+ cells and decreased cartilage destruction. In CD4+ T cells, presumably Th1 and Th17 cells, JAK plays a crucial role in RA synovitis.

Surgeon error in performing intraoperative estimation of stem anteversion in cementless total hip arthroplasty.

To examine the accuracy of intraoperative estimation of stem anteversion in total hip arthroplasty (THA), we compared the intraoperatively estimated stem anteversion (estimated prosthetic anteversion) to stem anteversion measured by postoperative computed tomography (true anteversion) in 73 hips in 73 patients. Estimated prosthetic anteversion was significantly greater than true anteversion by 5.8°, and the mean absolute value of surgeon error was 7.3° ranging from 11° underestimation to 25° overestimation. Surgeons tended to overestimate when the true anteversion was smaller. A multivariate analysis showed that advanced knee osteoarthritis significantly increased surgeon error. These results indicated that estimated prosthetic anteversion was generally larger than true anteversion and that the grade of knee osteoarthritis affected the degree of surgeon error.

Results at a minimum of 10 years of follow-up for AMS and PerFix HA-coated cementless total hip arthroplasty: impact of cross-linked polyethylene on implant longevity.

PURPOSE: The purpose of this study was to report results at a minimum of 10 years for hydroxyapatite (HA) coating on the titanium arc-sprayed cementless total hip arthroplasty (THA) and to evaluate the impact of cross-linked polyethylene (XLPE) on implant longevity. METHODS: A total of 131 consecutive primary THAs in 123 patients using an AMS acetabular cup and a PerFix HA stem were retrospectively reviewed. Conventional PE was used for 62 hips (CPE group) and cross-linked PE for 69 hips (XLPE group), with mean follow-up periods of 13 and 11.5 years, respectively. These patients were reviewed using the Japanese Orthopaedic Association (JOA) Hip Score and evaluated in terms of PE wear, osteolysis, and implant survival. RESULTS: The JOA score improved from 42.6 to 83.9 points at the final follow-up. The mean wear rate of 0.12 mm/year in the CPE group was significantly greater than that of XLPE at 0.007 mm/year. In the CPE group, ten (16.1 %) and two (3.2 %) hips, respectively, underwent PE exchange due to severe wear and acetabular revision due to loosening associated with osteolysis. Three patients had revision in the XLPE group: one cup for aseptic loosening, one PE for recurrent dislocation, and one stem for neck fracture. No evident osteolysis was seen in the XLPE group. Kaplan-Meier survivorship with any revision as the end point shows that the 12-year survival rate was 97.7 % for cups, 93.8 % for PE liners, and 99.2 % for stems. Multivariate analysis revealed that the use of XLPE significantly reduced the risk of revision, with the odds ratio (OR) of 4.3. CONCLUSIONS: AMS and PerFix HA components in this series show excellent implant fixation; however, high rates of PE wear and subsequent osteolysis were limiting factors in long-term success. Low wear rates with XLPE suggest improved implant longevity.

Late dislocation is associated with recurrence after total hip arthroplasty.

PURPOSE: This study was conducted to examine the risk factors for recurrent dislocation after total hip arthroplasty (THA) and test the hypothesis that late dislocations are associated with recurrence. METHODS: A total of 1,250 hips in 1,017 patients were retrospectively reviewed. All operations were performed through the posterolateral approach with posterior soft tissue repair. An early or late dislocation was defined as a dislocation occurring before or after one year postoperatively, respectively. RESULTS: Dislocation occurred in 36 hips (2.9 %) and 20 of them experienced recurrence. Recurrent dislocations were observed in ten out of 25 hips (40.0 %) with early dislocation; however, ten out of 11 hips (90.9 %) with late dislocation experienced recurrence (p = 0.0046). Multivariate analysis revealed that late dislocation was significantly associated with recurrence with odds ratio of 5.94 per year. Seven in 20 hips with recurrent dislocation required surgical treatment. CONCLUSION: Late dislocation significantly contributed to the development of recurrent dislocations.

Remodelling of femoral head-neck junction in slipped capital femoral epiphysis: a multicentre study.

PURPOSE: We examined the remodelling of the femoral head-neck junction in patients with slipped capital femoral epiphysis (SCFE) and the frequency of residual cam deformities. METHODS: We reviewed 69 hips in 56 patients with stable SCFE who had undergone in situ pinning. Mean age at slip was 11.7 years and the follow-up period 63.4 months. Cam deformity was evaluated using the anterior offset alpha (α) angle and head-neck offset ratio (HNOR). RESULTS: The average α angle and HNOR significantly improved from 76.2° to 51.3° and 0.086 to 0.135, respectively; 25 hips (36.2%) still had an α angle greater than 50°, and 32 hips (46.4%) had an HNOR of under 0.145. A multivariate analysis selected age at onset and slip angle as risk factors for cam deformity, with cutoff values 11.1 years and 21.0°, respectively. CONCLUSIONS: Although most hips had remodelling of the head-neck junction, 29.4 % had residual cam deformities that may be susceptible to femoroacetabular impingement.

Clinical and radiographic evaluation of total hip arthroplasties using porous tantalum modular acetabular components: 5-year follow-up of clinical trial.

OBJECTIVES: Porous tantalum is a biomaterial newly applied for artificial joints. We present here 5-years follow-up report of a multicenter clinical trial of total hip arthroplasties (THA) with porous tantalum modular acetabular component (modular PTC). METHODS: Study participants received 82 hips in 79 cases, with 61.2 months follow-up on average. Age at operation was 60.9 years. Clinical results were evaluated using Merle d'Aubigne Postel score. Presence of implant loosening, periacetabular radiolucency, osteolysis, and gap filling were examined for radiographic results. RESULTS: Merle d'Aubigne Postel score improved from 10.0 to 16.4 points. All PTC were radiographically stable, with no evidence of progressive radiolucencies. Average polyethylene wear rate was 0.004 mm/year, with no periacetabular osteolysis. Fifteen hips (18.3%) showed a gap >1 mm; however, all showed bone filling within 12 months. PTC with oversized reaming was significantly less likely to have a gap. No implant failure was noted related to modularity. Resulting survival rate of modular PTC was 100% at 5 years. CONCLUSIONS: Modular PTC showed excellent results at 5-years of follow-up. Some hips showed periacetabular gaps, which were filled with bone within 1 year. Further follow-up was needed to determine long-term efficacy.

Effects of adalimumab administration in bio-naïve and bio-switch rheumatoid arthritis patients in daily clinical practice : two-year results from single center.

AIMS: To investigate the impact of adalimumab on the biologic-naive (bio-naïve) and bio-switch rheumatoid arthritis (RA) patients, and to clarify the appropriate indications for adalimumab treatment. METHODS: The retention rate, efficacy and safety of adalimumab in twenty-one RA patients were analyzed. Fourteen of the patients were bio-naive and seven were bio-switched from other biologics. Concomitant methotrexate was used in 85% of the bio-naive and 71% of the bio-switch patients. The radiographic findings before and after the 1 year and the two years treatment were also surveyed. RESULTS: In the bio-naive group, 63% of patients continued adalimumab for 2 years, and remission was achieved in approximately 50% of patients. The mean 28-joint Disease Activity Scores improved from 5.2 to 2.6. Radiographically, the joint damage did not progress in either erosions or joint space narrowing. In the bio-switch group, the retention rate was 29%, and only patients who were switched from infliximab showed responses to the treatment. Herpes zoster requiring hospitalization occurred in two cases and injection site reactions were noted in other two cases. CONCLUSION: Adalimumab combined with methotrexate would be a useful first choice biologic regimen in bio-naïve RA patients. As a second biologic, adalimumab could be useful only when treatments are switched from infliximab.

Abductor recovery after muscle-sparing periacetabular osteotomy using a lateral approach.

To decrease hip abductor dysfunction after periacetabular osteotomy using a lateral/trochanteric approach, we aimed to modify transposition osteotomy of the acetabulum (TOA) to not cut the greater trochanter and abductor-iliac crest detachment. We subsequently compared abductor muscle strength recovery between TOAs with [conventional TOA (C-TOA)] and without [modified TOA (M-TOA)] trochanteric osteotomy. C-TOA and M-TOA were performed in 27 and 34 hips, respectively. Hip abduction, flexion and knee extension muscle strength were measured preoperatively and at 3, 5, 10, 24 and 52 weeks postoperatively. The muscle strength ratio of the affected and contralateral lower limbs was compared between the C-TOA and M-TOA groups. Neither the mean Merle d'Aubigné-Postel score at the final follow-up nor the postoperative center-edge angle showed significant differences between the M-TOA and C-TOA groups (15.7 versus 16.4 points; P = 0.25 and 38.5° versus P = 0.62 and 39.8°, respectively). The mean muscle strength ratios of hip abduction at 5, 12 and 24 weeks postoperatively were significantly higher in the M-TOA group than in the C-TOA group (0.62 versus 0.39, 0.76 versus 0.59 and 0.94 versus 0.70; P = 0.03, 0.04 and 0.01, respectively). There were no significant differences between groups at Postoperative Week 52 (P = 0.36). Discomfort at the greater trochanter was observed in 18 hips (66.7%) in the C-TOA group but only in 4 hips (11.2%) in the M-TOA group. In conclusion, M-TOA is less invasive than C-TOA and allows an earlier recovery of abductor muscle strength without significant correction loss.