Long-Term Outcomes for Cementless Anatomic Femoral Components, Compared by Area of Porous Coating, in Patients Younger Than 50 Years Treated for Hip Dysplasia.

BACKGROUND: We investigated whether the proximal circumferential porous coating of cementless stems would make implant survival of >20 years possible in young patients. METHODS: Data for patients younger than 50 years with hip dysplasia who had an anatomic stem implanted with a proximal porous coating with hydroxyapatite/tricalcium phosphate were reviewed. Noncircumferential porous (non-C-type) stems were used in 17 hips (13 cases), and circumferential porous (C-type) stems were used in 87 hips (68 cases). Acetabular components with conventional polyethylene were used for all hips. The mean ages at surgery for patients with non-C-type stems and those with C-type stems were 43.3 and 44.7 years, respectively. Stems that had not loosened were retained at the time of acetabular revision. The average duration of follow-up for patients with non-C-type stems was 26.9 years and was 22.3 years for those with C-type stems. RESULTS: Mean survival rates as determined by the Kaplan-Meier method were 74.9% at 20 years and 59.9% at 25 years for non-C-type stems and were 100% at 20 years and 94.0% at 25 years for C-type stems. The survivorship for C-type stems was significantly higher than that for non-C-type stems (P < .01). Focal osteolysis in the shoulder of 37 hips with C-type stems suppressed the spread of osteolysis to the distal femur. CONCLUSION: Anatomic femoral stems with a circumferential porous coating provide excellent durability in patients with hip dysplasia who are 50 years of age or younger. LEVEL OF EVIDENCE: Therapeutic Level IV.

Computed Tomographic Osteolytic Analysis of a First-Generation Remelted Highly Cross-Linked Polyethylene in Total Hip Arthroplasty-At a Minimum of 15-Year Follow-Up.

BACKGROUND: Low polyethylene wear rate and low incidence of osteolysis have been reported after total hip arthroplasty (THA) using first-generation remelted highly cross-linked polyethylene (HXLPE). However, osteolysis has not been evaluated in long-term studies of these patients (15 years or more). The present study assessed computed tomography (CT) images to determine the incidence of osteolysis associated with HXLPE in THA during at least 15 years of follow-up. METHODS: We evaluated 105 primary THAs in 84 patients (77 women and 7 men). Mean follow-up was 15.9 years (range, 15-18 years). All THAs used a Longevity HXLPE liner and a 26-mm zirconia femoral head. Areas of osteolysis were identified from CT images using 3D and multiplanar reconstruction views. RESULTS: CT 3D multiplanar reconstruction images at 15-year follow-up showed no obvious osteolysis in the acetabulum or femur of any patient. No patients developed cup loosening or liner breakage. CONCLUSION: Our study indicates that first-generation remelted HXLPE liners do not increase the risk of osteolysis during 15-year follow-up and suggests that the wear particles from first-generation remelted HXLPE are less biologically active than those generated by conventional polyethylene devices.

Positive FABER distance test is associated with higher alpha angle in symptomatic patients.

PURPOSE: The purpose of this study was to determine the diagnostic value of the flexion abduction external rotation (FABER) distance test (FDT) for the diagnosis of cam-type femoroacetabular impingement (FAI) as defined by alpha angle. METHODS: For this study, 603 patients with symptomatic, unilateral femoroacetabular impingement were included. Patients with symptoms of hip instability, bilateral symptoms, bilateral surgery, or bilateral alpha angles over 55 were excluded from the analysis. A positive FDT was defined as a difference of 4 cm or more between hips. A pathological cam was defined as an alpha angle of 78° or greater. RESULTS: The average age was 36.4 ± 12 years, with 344 males and 259 females. Faber distance of the injured hip was correlated with age at surgery (rho = 0.148; p < 0.001). Alpha angle on the injured hip was positively correlated with injured hip FABER distance (rho = 0.276; p < 0.001). The average alpha angle in patients with a positive FABER distance test was 74° (SD = 11°) compared to 68° (SD = 8°) in patients with a negative distance test (p = 0.001). The sensitivity of the FDT to diagnose pathological cam was 0.848 (0.79-0.89) with a negative predictive value of 86% (81-90%). CONCLUSION: This study demonstrated that the FABER distance test is correlated with the alpha angle and is a good diagnostic exam for pathological cam-type FAI as defined by and alpha angle equal to or greater than 78°. CLINICAL RELEVANCE: FABER distance test is a simple test that can be used as a screening test to decide if FAI should be suspected and further testing is needed. LEVEL OF EVIDENCE: III.

Inversion of the acetabular labrum causes increased localized contact pressure on the femoral head: a biomechanical study.

PURPOSE: Although studies suggest that subchondral insufficiency fracture of the femoral head may cause rapidly progressive osteoarthritis of the hip, the mechanism of that relationship remains unclear. Our biomechanical study aimed to provide more data in this area by quantifying pressure distribution on the femoral head for normal and inverted hips and by determining the effects of labral inversion on pressure distribution across the joint, focusing on types of fracture under load. METHODS: We tested mid-sized fourth-generation composite femurs at 15° of adduction, and applied 1 mm/min of axial compressive force to the femoral heads until failure. Additionally, single loads (3000 N) were applied using Prescale film to investigate pressure distribution on the femoral head, with or without silicone rubber representing entrapment of an inverted acetabular labrum. RESULTS: In tests with an external load of 3000 N, the mean pressure for 10 × 5 mm of silicone rubber was 11.09 MPa, significantly greater (about 5.7-fold) than 1.94 MPa without silicone rubber. Different fracture patterns were observed with and without the 10 × 5 mm silicone rubber; when the 10 × 5 mm silicone rubber specimens were used, all eight cases showed fractures in the anterior femoral head. CONCLUSIONS: When silicone rubber representing an inverted acetabular labrum was placed between a hemispherical metallic platen and a composite bone model, the silicone rubber areas were subjected to extreme concentration of stress. The fractures that developed at the silicone rubber areas clearly represented subchondral fractures of the femoral head, rather than fractures of the femoral neck.

Developmental Dysplasia Treated With Cementless Total Hip Arthroplasty Utilizing High Hip Center Reconstruction: A Minimum 13-Year Follow-up Study.

BACKGROUND: The primary aim of this study was to determine the clinical outcomes at 13-year follow-up of patients diagnosed with developmental dysplasia of the hip and subsequently treated with total hip arthroplasty (THA). The secondary aim was to investigate the effect of hip center location on clinical outcomes and polyethylene wear. METHODS: We reviewed data from a consecutive series of 104 patients (123 hips) from a single center. Patients were treated with THA with the high hip center (HHC) technique using cementless acetabular shells and highly cross-linked liners. Radiographs were collected preoperatively and through 13-year follow-up to assess degree of dysplasia (Crowe classification), component positioning, occurrence of bone resorption, and polyethylene wear. The Harris Hip Score (HHS) was administered at 4 and 13 years. RESULTS: No patients were lost to follow-up, and one was revised for femoral loosening. Radiolucency was seen in 20% of patients and was not associated with HHC (P = .560). No patients developed osteolysis. The wear rate was low for all patients (mean: 3 ± 19 µm/y) and not associated with HHC (P = .852). The median 13-year HHS was 91.9 (interquartile range: 84.8-97.0). There was a statistically significant decline from the 4- to 13-year HHS (P < .001) for the Crowe II-IV group, although 82% of these patients remained above 80 points at 13 years. The nondysplastic and Crowe I group showed no longitudinal change in HHS (P = .243). CONCLUSION: This cup design and highly cross-linked polyethylene liner combination demonstrates excellent clinical outcomes, similar to THA for primary osteoarthritis, through 13-year follow-up in patients with various degrees of developmental dysplasia of the hip and HHC reconstructions.

Re-dislocation after revision total hip arthroplasty for recurrent dislocation: a multicentre study.

PURPOSE: Although most case of dislocations after total hip arthroplasty (THA) can be managed with conservative treatment, recurrent dislocation may require surgical intervention. This multicentre study was conducted to evaluate the re-dislocation rate after revision THA for recurrent dislocation, and to determine the risk factors for re-dislocation. METHODS: We retrospectively reviewed the 88 hips in 88 patients who underwent revision THA for recurrent dislocation at five institutions between 1995 and 2014. The mean patient age at surgery was 68.5 years and the mean follow-up period was 53.1 months. Multivariate logistic regression was performed to identify risk factors for re-dislocation. RESULTS: Sixteen hips in 16 patients (18.2 %) re-dislocated at a mean of 25.5 months (range, 1-83 months) after revision THA. Multivariate analysis identified osteonecrosis of the femoral head (odds ratio [OR] = 5.62 vs. osteoarthritis) and a femoral head size < 32 mm (OR = 3.86) as independent risk factors for re-dislocation. Eight hips required additional revision THA for re-dislocation. CONCLUSION: The re-dislocation rate after revision THA for recurrent dislocation remains high, suggesting the need for prevention measures. We recommend the use of a femoral head size ≥ 32 mm.

Tenosynovial giant cell tumors in unusual locations detected by positron emission tomography imaging confused with malignant tumors: report of two cases.

BACKGROUND: A tenosynovial giant cell tumor (T-GCT) is a benign synovial tumor arising from the synovium, bursae, or tendon sheath. It can be intra- or extra-articular and localized or diffuse. Diffuse T-GCT is considered as a locally aggressive. Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose with computed tomography (FDG PET/CT) is widely used to differentiate malignant from benign tumors and to detect distant metastasis. However, FDG PET/CT is limited by false-positive findings. In this study, we present two cases of T-GCT that developed in unusual locations and were confused with malignant tumors. The final diagnoses were histologically confirmed as T-GCTs. CASE PRESENTATION: Case 1. A 45-year-old Japanese female presented with a left choroidal melanoma and an abnormal lesion adjacent to the first cervical (C1) lamina confirmed by a PET scan (maximum standardized uptake value [SUVmax] =9.9 g/ml). MRI of the neck also detected a soft tissue mass (14.6 × 7.7 × 7 mm) adjacent to the C1 lamina. The choroidal melanoma was treated by heavy carbon ion radiotherapy. Although the size of the C1 soft tissue tumor remained unchanged, a CT-guided biopsy confirmed the diagnosis of the neck mass as a T-GCT. Case 2. A 15-year-old Japanese male with multiple type 1 neurofibromatosis presented with a soft tissue mass (26.1 × 24.7 × 11.5 mm) of the extra-articular hip joint that was coincidentally detected by FDG PET/CT during examination of a mediastinal soft tissue mass. SUVmax of the mediastinal lesion was 2.6 g/ml and of the hip lesion was 12.8 g/ml. Thus, differentiation from a malignant tumor, such as a malignant peripheral nerve sheath tumor, was necessary. An open biopsy was performed, and the frozen section was diagnosed as T-GCT. The tumor was excised, and the final histological diagnosis confirmed T-GCT. CONCLUSION: T-GCT can show high FDG uptake, which might be confused with malignancy. Although MRI findings and location might help in the diagnosis of a T-GCT, careful assessment is mandatory, especially in unusual locations.

Squeaking and microcracks in a delta-delta ceramic coupling: pin-on-disc study.

There is a rising concern about squeaking in ceramic-on-ceramic total hip arthroplasty (THA). In pin-on-disc testing of a delta-delta coupling, we reproduced squeaking and observed microcracks on worn surfaces. We used a pin-on-disc machine and made discs and pins by cutting delta ceramic to a diameter of 40 mm (D-D). Cross-linked polyethylene was used for a comparison disc (D-P). We performed the same test using another D-D coupling specimen to confirm reproducibility. Squeaking in the D-D specimen was reproduced in wet conditions, though it was not found in the D-P specimen. Fast Fourier transform analysis showed a peak frequency for squeaking of 2794 Hz. The noise occurred at about 6.6 km of sliding distance. Scanning electron microscopy revealed that the worn surface of the pin in D-D at 10.8 km of sliding distance had some microcracks. However, there was no obvious damage to the worn surface of the pin in D-P at the same sliding distance. We confirmed the reproducibility of these findings, obtaining similar results, including squeaking, from another D-D coupling specimen. Our findings show that squeaking may occur in THA using delta ceramic bearings even if implants are placed to avoid extra-articular impingement of the femoral neck. Although the clinical relevance of microcracks is unknown, they may affect long-term outcomes in THA using delta ceramic bearings.

Outcomes After Labral Repair in Patients With Femoroacetabular Impingement and Borderline Dysplasia.

PURPOSE: To determine outcomes after labral repair in patients with borderline dysplasia and femoroacetabular impingement (FAI). METHODS: Patients with dysplasia treated between June 2005 and March 2009 were identified. The study included only patients aged 18 years or older (mean, 35 years; range, 18 to 69 years) whose affected hip had a Wiberg center-edge angle of 20° to 25° and who underwent primary hip arthroscopy performed by the senior author. RESULTS: One hundred two hips (100 patients, comprising 50 women and 50 men) underwent hip arthroscopy with labral repair with correction of FAI and capsular closure. Five hips were converted to total hip arthroplasty, and 7 required revision arthroscopy. Of 95 patients (representing 100 hips, 5 of which underwent total hip arthroplasty), 80 were monitored for a minimum of 2 years. At a mean follow-up point of 40 months, the preoperative modified Harris Hip Score had improved from a mean of 63.5 points (range, 20 to 98 points) to a mean of 84.9 points (range, 45 to 100 points) by the latest follow-up (P < .001). The mean score on the Western Ontario and McMaster Universities Arthritis Index improved from 25.3 (range, 0 to 60) to 9.7 (range, 0 to 59) (P < .001). The 12-Item Short Form Health Survey Physical Component Summary score also significantly improved (from 42.5 to 50.9, P = .001), whereas the 12-Item Short Form Health Survey Mental Health Component Summary score showed an insignificant improvement (from 52.4 to 54.1). CONCLUSIONS: This study showed that FAI and labral pathology can be successfully managed using hip arthroscopy, with capsular management, in patients with borderline dysplasia. Patients showed significant improvements in outcomes and high levels of satisfaction after hip arthroscopy. The need for subsequent procedures was similar to that in patients with just FAI and labral repair. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Does rotational acetabular osteotomy affect subsequent total hip arthroplasty?

INTRODUCTION: Rotational acetabular osteotomy (RAO) has 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. We evaluated the effect of previous RAO on the outcome of THA performed for degenerative arthritis secondary to DDH, comparing outcomes for patients with THA and prior RAO versus outcomes for patients with THA and no prior RAO. MATERIALS AND METHODS: At an average follow-up point of 8.2 years (range 7-11 years), we compared outcomes in dysplastic hips for 22 hips (group R) in patients who underwent THA after successful RAO with outcomes for a well-matched control group of 30 hips in patients who underwent primary THA (group C) during the same period. RESULTS: Both groups had similar midterm results. No acetabular or femoral components exhibited loosening or revision in either group. Harris hip scores (HHSs) at the most recent follow-up had not been compromised by RAO, and there were no significant differences in intraoperative blood loss and operative time between the two groups. Although there was a tendency toward superolateral placement of the acetabular component in group R, there were no significant differences in the mean steady-state linear and volumetric wear rates between the two groups. There were no infections, dislocations, intraoperative fractures, damaged nerves, or deep vein thromboses in either group. CONCLUSIONS: Our midterm results demonstrated that RAO does not lead to higher revision rates, compromised HHSs, or shortened survivorship in eventual THA for DDH.

Bone remodeling after a mean of 10 years in diaphyseal cortical defects repaired with femoral revision using bypass fixation of extensively porous-coated stems with high stiffness.

INTRODUCTION: Femoral component revisions with extensively porous-coated stems have shown promising clinical results, although there are still concerns over stress-shielding. MATERIALS AND METHODS: We retrospectively reviewed data for 18 patients undergoing femoral component revisions with extensively porous-coated stems with high stiffness. The average length of follow-up was 10 years (range 6-13.7 years). RESULTS: Radiographic evidence of a bone-ingrown stem was present in 94 % of the hips, and stable fibrous fixation was present in only one hip, but no hips were considered unstable. There was mild stress-shielding in 15 hips, moderate stress-shielding in one hip, and severe stress-shielding in two hips. In one of the latter two hips, stress-shielding was progressive even 8 years after revision surgery. In 12 (92 %) of the 13 hips in which bypass fixation for diaphyseal cortical defects was used, there was good remodeling. CONCLUSIONS: We suggest that femoral component revision using extensive porous-coated stems is a useful option that may allow for healing of diaphyseal cortical defects.

Inversion of the acetabular labrum triggers rapidly destructive osteoarthritis of the hip: representative case report and proposed etiology.

The pathophysiology of rapidly destructive osteoarthritis (OA) of the hip is unknown. This study documented cases of inversion of the acetabular labrum, which has clinicoradiologic features similar to those of initial-stage rapidly destructive hip OA. Our study was based on a prospective review of data for 9 patients with rapidly destructive hip OA. Intraoperative findings showed that the anterosuperior portion of the acetabular labrum had inverted into the articular space, along with many fragments of articular cartilage, in all patients. Subchondral insufficiency fractures of the femoral heads were seen just under the inverted labra in 8 of the 9 patients. Inversion of the acetabular labrum may be involved in rapid joint-space narrowing and subchondral insufficiency fracture in rapidly destructive hip OA.

Retrieval analysis of new-generation yttria-stabilized zirconia femoral heads after total hip arthroplasty.

Zirconia femoral heads were introduced for total hip arthroplasty (THA) with the expectation of lower polyethylene (PE) wear and better clinical results. Because several studies reported poor survivorship of yttria-stabilized zirconia-PE THA, we investigated a new-generation yttria-stabilized zirconia head (diameter, 26 mm) manufactured by NGK Spark Plug. We retrieved six zirconia heads at revision THA after they had been in place for a mean of 8.6 years and measured their surface roughness and mean monoclinic content. Although their mean monoclinic content was higher than that of the unused head, surface roughness in the implanted heads was as low as that of the unused head, indicating that wear reduction may be possible with the selection of a suitable zirconia femoral head.

Wear comparison between conventional and highly cross-linked polyethylene against a zirconia head: a concise follow-up, at an average 10 years, of a previous report.

We previously reported the results of wear comparison at a minimum of 5 years between highly cross-linked polyethylene (HXLPE) and conventional polyethylene (PE) against a zirconia femoral head. We now report the mean wear at 10 years for 52 patients (56 hips) of the original cohort of 61 patients (65 hips) who had undergone primary total hip arthroplasty at our hospital between November 1999 and August 2000. The mean steady-state linear wear rate of HXLPE was 0.045 mm/y, compared with 0.080 mm/y for conventional PE (P=.0003). The incidence of osteolysis was 25% in the conventional PE group compared with 0% in the HXLPE group. Our study demonstrated that the steady-state wear rate for HXLPE remains significantly lower than that for conventional PE against a zirconia femoral head at a mean of 10 years after implantation.

Cementless anatomic total hip femoral component with circumferential porous coating for hips with developmental dysplasia: a minimum ten-year follow-up period.

Anatomic femoral components are optimized for primary osteoarthritis, and few long-term results for their use are available for developmental dysplasia of the hip (DDH). We reviewed 135 uncemented total hip arthroplasties in which an anatomic femoral component was used in 106 patients with DDH, excluding femurs with neck-shaft angles of >160° and femurs with anteversion of >50°. The mean age of patients at surgery was 49.4 years (range, 33-66 years), and the mean duration of follow-up was 13.5 years (range, 10-18 years). No osteoporotic femurs were included in our study group. Despite 18 acetabular revisions, no femoral component was removed for any reason. No femoral loosening was seen at the final follow-up examination. An anatomic femoral component with circumferential porous coating can produce good clinical and radiologic findings in young patients with good bone quality who have DDH without excessive femoral deformity.

Osteonecrosis development in a novel rat model characterized by a single application of oxidative stress.

OBJECTIVE: To investigate the relationship between transient oxidative stress and the development of osteonecrosis in a rat model. METHODS: A total of 160 male Wistar rats (24 weeks old) were injected only once with the pro-oxidant DL-buthionine-(S,R)-sulfoximine (BSO) (500 mg/kg given intraperitoneally) and were killed 12 hours (group A), 1 day (group B), 3 days (group C), 4 days (group D), 5 days (group E), 7 days (group F), or 14 days (group G) after administration (n = 20 per group). Twenty untreated rats were used as a control group (group N). Femurs were examined histopathologically for the presence of osteonecrosis, and reduced glutathione (GSH) in liver tissue was measured as an index of oxidative stress. RESULTS: GSH decreased rapidly after BSO administration. Significant decreases were noted in groups A and B as compared to group N (P < 0.0001 and P = 0.0007, respectively), confirming the development of transient extreme oxidative stress soon after BSO administration. The histopathologic study revealed osteonecrosis in 10% of the rats in group E, 35% of the rats in group F, and 40% of the rats in group G. CONCLUSION: Transient extreme oxidative stress was confirmed to induce osteonecrosis in this model. Since preparation of this model is extremely simple and because rats are well suited to genetic studies, this model may be of use in elucidating the pathophysiology of femoral head osteonecrosis in future studies.

Wear comparison between a highly cross-linked polyethylene and conventional polyethylene against a zirconia femoral head: minimum 5-year follow-up.

Highly cross-linked polyethylene (HXLPE) was developed to reduce wear of articular bearing surface in total hip arthroplasty patients. Several studies have shown reduced wear of HXLPE compared with conventional polyethylene; however, these studies had used HXLPE in combination with a Co-Cr metal head. The purpose of this study was to compare the 5-year in vivo wear of HXLPE with that of conventional PE using a zirconia femoral head. Forty-five hips with a Trilogy HXLPE (Zimmer, Warsaw, Ind) were matched and compared with a control group of 20 conventional Trilogy PE hips. The 2-dimensional linear wear rate was significantly less in the HXLPE group between 1 and 5 years postoperation (P < .001). The results show that HXLPE reduces short-term polyethylene wear against not only a Co-Cr head but also a zirconia head.

Should the well-fixed, uncemented femoral components be revised during isolated acetabular revision?

INTRODUCTION: The results of isolated acetabular revision performed in 35 patients (36 hips) were monitored from 3 to 10 years. All femoral components were well fixed and not removed or revised during index surgery. METHOD: All revision acetabular implants were cementless, using a porous-coated hemispheric cup with or without bone graft. There were no cases of femoral component radiographic or clinical failure. For some cases, we performed bone grafting to focal osteolysis of the proximal femur around the cementless stem. RESULTS: Bone incorporation occurred in 12 hips (overall 14). The mean pre- and postoperative Harris Hip Scores were 49 and 80, respectively. The findings suggest that isolated acetabular revision using a cementless porous-coated hemispheric cup can be performed without removing or revising a stable, well-fixed, uncemented femoral component if there is no concern about dislocation. CONCLUSION: We demonstrated that isolated acetabular revision is feasible and that grafting to the osteolytic femoral defects is a worthwhile procedure to restore bone stock.

A Novel Minimally Invasive Spherical Periacetabular Osteotomy: Pelvic Ring Preservation and Patient-Specific Osteotomy by Preoperative 3-Dimensional Templating.

BACKGROUND: Spherical periacetabular osteotomy (SPO) is a novel osteotomy involving splitting the teardrop, using patient-specific preoperative planning, and requiring only a 7-cm skin incision. We report preoperative planning methods and short-term results of SPO. METHODS: In preoperative planning, computed tomography (CT) images were imported into 3-dimensional templating software. The radius of the curved chisel was mapped to pass through the teardrop, the infracotyloid groove of the ischium, and the area between the anterior superior iliac spine and the anterior inferior iliac spine. The osteotomy height and the predicted depth of osteotome insertion were measured, and those values were reproduced during surgery. We performed a retrospective analysis of data on 52 consecutive patients (55 hips) with hip dysplasia who underwent SPO and were followed for at least 2 years: 27 hips had Tönnis grade 0, 21 had grade 1, and 7 had grade 2. The mean age at surgery was 38 years (range, 17 to 56 years). The rotated bone fragment and iliac crest were fixed with absorbable screws. Statistical analysis was performed with the paired t test. RESULTS: The mean (range) of the lateral center-edge and sourcil angles were 6.0° (-20° to 18°) and 26.0 (13° to 38°), respectively, before surgery and 30.0° (15° to 43°) and 3.8° (-4° to 27°), respectively, after surgery (p < 0.001). However, 11 hips (20%) showed a loss of correction of bone rotation (<3 mm) or the sourcil angle (<3°). Radiographs showed bone union in all hips within 3 months after the surgery. Early second surgery related to absorbable screws was performed in 2 hips. No patient had required conversion to total hip arthroplasty at the time of writing. Clinical scores were significantly improved at the 2-year follow-up (p < 0.001). Paresthesia of the lateral femoral cutaneous nerve area was very common but had resolved in 92% of the patients at the 2-year follow-up. CONCLUSIONS: SPO is a novel minimally invasive periacetabular osteotomy that has the potential disadvantage of early loss of correction (observed in 20% of the hips in the present study) but may provide the benefit of decreasing the risk of nonunion at the pubis osteotomy site. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Prevention of steroid-induced osteonecrosis by intravenous administration of vitamin E in a rabbit model.

BACKGROUND: We focused on vitamins with marked antioxidant potency to see whether their use might prevent the development of steroid-induced osteonecrosis. METHODS: Fifteen Japanese white rabbits weighing about 3.5 kg were injected once into the right gluteal muscle with methylpred-nisolone (MPSL) 40 mg/kg (S group). In addition, 10 other rabbits received consecutive daily intravenous injections of vitamin E 50 mg/kg, starting from the day of MPSL administration (E group). All animals were killed 2 weeks after MPSL administration, and femurs were extracted and stained with H&E. Blood levels of reduced glutathione (GSH) were also measured. RESULTS: In the S group the osteonecrosis development rate was 93%, in contrast to 0% in the E group (P < 0.01). Also, GSH levels in the S group abruptly decreased from the first day after MPSL administration, whereas in the E group, the decline in GSH levels was significantly suppressed on days 1 and 3 after MPSL administration (P< 0.05). CONCLUSIONS: Vitamin E administration significantly inhibited steroid-induced oxidative stress. The results of this study suggest that the administration of vitamin E may be a novel and simple method to prevent the development of steroid-induced osteonecrosis.