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BACKGROUND Femoral nerve palsy is an uncommon but serious complication during the anterolateral approach for total hip arthroplasty. One of the reported reasons for femoral nerve palsy is retractor-induced intraoperative damage after retractor placement on the anterior wall of the acetabulum. The present study aimed to clarify the femoral nerve status during anterolateral approach total hip arthroplasty using motor-evoked potential analysis and to identify risk factors influencing the nerve status. METHODS From June 2019 to September 2020, 32 hips in 31 patients underwent primary total hip arthroplasty via the anterolateral approach. The integrity of the femoral nerve was tested by the motor-evoked potential at three time points: preoperatively as a control (first period), immediately after retractor placement on the anterior wall of the acetabulum (second period), and after the procedure (third period). In the second period, the hips were divided into the following two groups: a

Beta-tricalcium phosphate (β-TCP) is often used as a gap filler in open-wedge high tibial osteotomy (OWHTO). The aim of the present study was to investigate the effects of using β-TCP with different porosities on bone remodelling after OWHTO.Methods: We evaluated 29 knees in 26 patients that underwent OWHTO using β-TCP with porosities of 60% and 75% (combined group). A further 30 knees in 28 patients that underwent OWHTO using β-TCP with 60% porosity alone were allocated as a control group. In the combined group, a β-TCP block with 75% porosity was inserted into the gap at the cancellous bone site and a β-TCP block with 60% porosity was inserted into the medial cortical bone side. In the control group, a β-TCP block with 60% porosity was inserted into the osteotomy gap. The bone remodelling phases of the inserted β-TCP blocks were evaluated on standard anteroposterior radiographs using the modified van Hemert classification at 3 and 6 months post-operatively.The rate of satisfactory bone remodelling at the cancellous bone sites was 86.2% (25/29) in the combined group and 0% (0/30) in the control group at 3 months post-operatively (p0.05), progressing to 96.6% (28/29) in the combined group and 20% (6/30) in the control group at 6 months post-operatively (p0.05).The present study demonstrated that combined use of β-TCP with high and low porosities can significantly enhance bone formation. The combined use of artificial bones with different porosities is useful for early bone remodelling in OWHTO.

Some researchers have stated that magnetic resonance imaging (MRI) is useful for assessing the coracoacromial ligament (CAL) at the acromial undersurface. However, few studies have investigated the reliability and clinical significance of MRI findings for the CAL at the acromial undersurface. The purpose of this study was to determine the association between CAL thickness at the acromial undersurface and rotator cuff tear size.The CAL thickness at the acromial undersurface was evaluated in 182 patients with rotator cuff tears (mean age: 64.9 ± 8.4 years) using a 3.0-Tesla MRI system. The association between CAL thickness at the acromial undersurface and rotator cuff tear size determined by the DeOrio and Cofield classification (partial; small:1 cm; medium: 1-3 cm; and large or massive:3 cm) was analyzed statistically. The intraobserver and interobserver reliabilities for MRI measurements of CAL thickness at the acromial undersurface were determined by calculation of intraclass correlation coefficients and their 95% confidence intervals.The mean CAL thickness at the acromial undersurface was 2.7 ± 1.4 mm (range: 0-6.5 mm). Increasing rotator cuff tear size was significantly associated with decreasing CAL thickness at the acromial undersurface (The present study clarified that (1) MRI was a reliable tool for evaluation of CAL thickness at the acromial undersurface and (2) increasing rotator cuff tear size was significantly associated with decreasing CAL thickness at the acromial undersurface. These findings may assist toward understanding the progressive pathology in rotator cuff disease.

Patients scheduled for metal implant surgery in some facilities in Japan undergo preoperative metal patch testing (MPT). However, few studies have reported the impact of MPT results on scheduled surgery; therefore, the value of preoperative MPT remains unknown.In analysis 1,the preoperative MPT results requested by orthopedic surgeons from 4 institutions from 2014 to 2018 were retrospectively analyzed. In analysis 2, the medical records of all patients who underwent total hip arthroplasty, total knee arthroplasty, or total shoulder arthroplasty/reverse shoulder arthroplasty between 2014 and 2018 were collected. The number of patients who underwent MPT and their surgical results were analyzed.In analysis 1, MPT was performed on 72 patients during the study period. The overall MPT positivity rate was 26.4% for the entire cohort in analysis 1. In 4 out of 19 MPT-positive cases, the results of MPT changed the treatment plan to use alternative materials or cancel the surgery. In analysis 2, 1087 patients underwent total hip arthroplasty, total knee arthroplasty, and TSA/RSA; only 16 patients underwent MPT. Aseptic loosening occurred postoperatively in 3 patients (0.3%), none of whom had a history of allergy, and none underwent preoperative MPT.Metal allergy did not appear to be directly involved in aseptic loosening to any large or meaningful degree in our patient cohort. Only 1.5% of the patients underwent preoperative MPT; therefore, our results suggest this testing had limited benefit or utility. Further studies are needed to determine whether MPT is necessary in preparation for joint replacement.

The present study was performed to investigate the morphological characteristics of the calcaneofibular ligament (CFL) and evaluate its relationship to the anterior talofibular ligament (ATFL) in patients with lateral ankle ligament injury using 3-dimensional magnetic resonance imaging (3D-MRI). This retrospective study involved 35 patients with lateral ankle ligament injury and 24 patients without a history of ankle trauma and a bone abnormality as controls. Reconstructed 3D-MRI was used to classify the form of the CFL as curved, wavy, or straight. The presence/absence of continuity between the fibula and CFL was evaluated in the 35 patients with injury, who were divided into 2 groups (continuity and discontinuity groups). The number of fascicles in the ATFL and the continuity between the distal end of the fibula and the proximal end of the ATFL were then evaluated. Among the patients with injury, 54.3% had the curve type of CFL, 34.3% had the wave type, and 11.4% had the straight type. In the control group, 62.5% had the curve type, 37.5% had the wave type, and none had the straight type. Continuity between the fibula and CFL was seen in 88.6%, and discontinuity was seen in 11.4%. Additionally, 85.7% had double fascicles in the ATFL. Inferior fascicle discontinuity between the ATFL and fibula was found in 13.3% with a double-fascicle ATFL; in all of these patients, the form of the CFL was straight and exhibited inferior fascicle discontinuity. The straight form of CFL could be a 3D-MRI sign in the diagnosis of CFL and ATFL inferior fascicle injury.

Curved periacetabular osteotomy (CPO) is one of the periacetabular osteotomies for the treatment of acetabular dysplasia. Several complications have been described after CPO, however, there have been no reports on the leg length change (LLC). This study aimed to investigate the LLC after CPO and its impact on the clinical outcomes.This study was a retrospective review of 70 consecutive hips in 67 patients with symptomatic acetabular dysplasia who underwent CPO between March 2016 and April 2019. Preoperative and postoperative leg lengths were measured using anteroposterior radiographs, and the clinical outcomes were evaluated based on the Harris hip score (HHS) and Medical Outcomes Survey 36-item Short Form Health Survey (SF-36).The mean LLC (and standard deviation) after CPO was -0.08 ± 3.10 mm. The mean HHS significantly improved from 73.5 points to 91.9 points (P.001). The physical component and role component scores of SF-36 significantly improved from 35.1 to 46.1 (P.001) and from 39.5 to 47.0 (P.001), respectively. No significant differences were found between the preoperative and postoperative mental component scores of SF-36. In addition, among 70 hips, 35 hips exhibited leg length elongation (0 to plus 6.82 mm) after CPO, whereas 35 hips exhibited leg length shortening (0 to minus 6.23 mm). No significant differences were found in HHS and SF-36 between the leg elongation group and leg shortening group.The mean LLC after CPO was -0.08 ± 3.10 mm, and this change does not affect the postoperative clinical outcomes.

This study aimed to elucidate the relationship between ankle morphology and the size of non-trauma related osteochondral lesions of the talus (OLT), because approximately half the OLT found in children is of unknown origin.34 ankles in 30 skeletally immature children with OLTs who underwent preoperative magnetic resonance imaging (MRI) were evaluated. Parameters measured included area of the OLT, tibial axis-medial malleolus angle (TMM), malleolar width (MalW), and talar surface angle (TSA; defined as the angle between the line perpendicular to the mid-diaphysis of the tibia and the talar joint surface; medial inclination, positive). The ankles were divided into two groups: the trauma group had a history of injury and the idiopathic group had no history of injury. The correlation between lesion area and MRI parameters were evaluated in each group.Thirteen ankles in 13 patients comprised the trauma group, while 21 ankles in 17 patients were in the idiopathic group. Of the 17 patients in the idiopathic group, four had bilateral OLT. In the trauma group, MalW was significantly correlated with the area (r = 0.827, P = 0.0001). In the idiopathic group, TMM and MalW were significantly correlated with the area (r = 0.608, P = 0.003 and r = 0.566, P = 0.008). TSA was positively correlated with area in the idiopathic group (r = 0.516, P = 0.017), but negatively correlated with area in the trauma group (r = -0.609, P = 0.027). The other parameters showed no significant correlation.The size of non-trauma related OLTs may have been affected by an ankle morphology showing poor bone conformity, such as an open medial malleolus and inclined talar joint surface. In addition, the evaluation of the contralateral ankle joint may be crucial when patients with OLT have no specific history of trauma.

Background Curved periacetabular osteotomy (CPO) is performed via an anterior approach without detachment of the hip abductor muscles. This study aimed to evaluate the abductor muscle status shortly after CPO on magnetic resonance imaging (MRI). Methods We prospectively evaluated 38 hips in 38 patients 1 week and 3 months after CPO between October 2017 and July 2019. The status of the abductor muscles was assessed on MRI using the following criteria: grade 0, normal; grade I, strain/edema; grade II, partial tear; and grade III, complete tear. We also evaluated associations between muscle status and patients’ characteristics. Results One week after CPO, the gluteus maximus was classified as grade 0 in all patients. The gluteus medius was grade 0 in 84.2% of patients and grade I in 15.8%. The gluteus minimus was grade I in 55.3% of patients and grade II in 44.7%. Three months after CPO, both the gluteus maximus and gluteus medius were grade 0 in all patients, while the gluteus minimus was still grade I in 47.4%. There were no significant differences between patients with a grade 0 and grade I gluteus minimus at 3 months after CPO in patients’ characteristics (age and body mass index) or clinical scores (Harris Hip Score and Japanese Orthopedics Association score). Conclusion Both the gluteus minimus and medius showed abnormal appearances on MRI 1 week after CPO, whereas only the gluteus minimus showed abnormalities 3 months after CPO. This abductor muscle status did not affect the postoperative Harris Hip Score or Japanese Orthopedics Association score.

Background The Association Research Circulation Osseous (ARCO) presents the 2019 revised staging system of osteonecrosis of the femoral head (ONFH) based on the 1994 ARCO classification. Methods In October 2018, ARCO established a task force to revise the staging system of ONFH. The task force involved 29 experts who used a web-based survey for international collaboration. Content validity ratios for each answer were calculated to identify the levels of agreement. For the rating queries, a consensus was defined when more than 70% of the panel members scored a 4 or 5 rating on a 5-point scale. Results Response rates were 93.1%-100%, and through the 4-round Delphi study, the 1994 ARCO classification for ONFH was successfully revised. The final consensus resulted in the following 4-staged system: stage I—X-ray is normal, but either magnetic resonance imaging or bone scan is positive; stage II—X-ray is abnormal (subtle signs of osteosclerosis, focal osteoporosis, or cystic change in the femoral head) but without any evidence of subchondral fracture, fracture in the necrotic portion, or flattening of the femoral head; stage III—fracture in the subchondral or necrotic zone as seen on X-ray or computed tomography scans. This stage is further divided into stage IIIA (early, femoral head depression ≤2 mm) and stage IIIB (late, femoral head depression >2 mm); and stage IV—X-ray evidence of osteoarthritis with accompanying joint space narrowing, acetabular changes, and/or joint destruction. This revised staging system does not incorporate the previous subclassification or quantitation parameters, but the panels agreed on the future development of a separate grading system for predicting disease progression. Conclusion A staging system has been developed to revise the 1994 ARCO classification for ONFH by an expert panel-based Delphi survey. ARCO approved and recommends this revised system as a universal staging of ONFH.

Background Distal first metatarsal osteotomy is an option for operative treatment of mild to severe hallux valgus (HV) deformities. Minimally invasive distal linear metatarsal osteotomy (DLMO) provides good outcomes without avascular necrosis (AVN) of the metatarsal head. However, no reports have described the in vivo blood flow changes in the metatarsal head after osteotomy. This study was performed to evaluate the in vivo blood flow of the pre- and post-osteotomy metatarsal head in patients with HV using laser Doppler flowmetry and thus clarify the effect of minimally invasive distal first metatarsal osteotomy on the change in blood flow. Methods From April 2015 to October 2016, DLMO was performed on 13 feet with HV in 10 patients (2 men, 8 women). Blood flow measurements of the pre- and post-osteotomy first metatarsal head in all feet were performed by laser Doppler flowmetry. AVN was evaluated using plain radiographs at the final postoperative follow-up. Results The median pre- and post-osteotomy blood flow was 1.5 (0.97–1.95) and 1.46 (0.98–1.77) ml/min/100 g, respectively (median change in blood flow, 0.00; 95% CI, −0.23–0.13; P = 0.72). The rate of change in the blood flow was 0.0% (95% CI, −11.9%–8.7%; range, −28.6%–64.7%), and only three patients (23.1%) showed a decrease of ≥10%. The median pre- and post-osteotomy systolic blood pressure was 90 (84.5–97) and 93 (84.5–95) mmHg, respectively (median change in blood pressure, 0.00; 95% CI, −3.0–2.0; P = 0.82). The rate of change in the systolic blood pressure was 0.0% (95% CI, −3.1%–2.2%; range, −9.1%–24.0%). No radiographic evidence of AVN was present at the final follow-up. Conclusions No significant difference was found in the rate of change in blood flow pre- and post-osteotomy, suggesting that minimally invasive distal first metatarsal osteotomy does not influence blood flow of the metatarsal head.

Objectives The objective of this study was to describe the appearance of Subchondral insufficiency fracture (SIF) by computed tomography (CT). Methods Images of 52 consecutive patients diagnosed with SIF were retrospectively reviewed. CT was available for five patients (7 cases). Results Corresponding to a low-intensity band on MR images, a radiolucent or sclerotic band was observed on CT images. Conclusion The present study is the first to report CT findings of SIF. A radiolucent or sclerotic band was observed on CT images. The results of the present study provide useful information for diagnosis of SIF.

Background Curved periacetabular osteotomy (CPO) is a joint-preservation surgery to treat acetabular dysplasia. It is performed via an anterior approach with the osteotomy of the anterosuperior iliac spine (ASIS). One of the complications associated with CPO includes non-union of the osteotomy sites. However, all osteotomy sites including the ASIS have not been simultaneously evaluated. Therefore, we investigated: (1) the bone union status of all osteotomy sites; and (2) the predictors of non-union at one year after CPO based on computed tomography (CT). Hypothesis The bone union status may be different in each osteotomy site. Patients and methods This retrospective review included 147 hips of 124 patients with symptomatic acetabular dysplasia who underwent CPO from 2011 to 2018. At one year postoperatively, we evaluated the bone union status of all osteotomy sites: the ASIS, ischium, pubis, and ilium using CT and investigated the predictors for achieving bone union. Results Bone union was confirmed in both the ASIS and ilium in all cases. In contrast, ischial and pubic non-union was confirmed 15/147 hips (10.2%) and 42/147 hips (28.5%), respectively. The multivariate analysis revealed that the predictors of ischial non-union were both large width of the gap at the pubic osteotomy site and small postoperative acetabular roof obliquity, and that the predictor of pubic non-union was large width of the gap at the pubic osteotomy site. Discussion At one year after CPO, both the ASIS and ilium obtained complete bone union, while ischial and pubic non-union were observed. Large width of the gap at the pubic osteotomy site was the predictor of both ischial and pubic non-union. In CPO, sufficient bone union can be achieved at the ASIS and the ilium, while it is necessary to reduce the width of the gap at the pubic osteotomy site to prevent ischial and pubic non-union. Level of evidence IV; retrospective study.

Background Curved periacetabular osteotomy (CPO) is a joint-preservation surgery to treat acetabular dysplasia. It is performed via an anterior approach with the osteotomy of the anterosuperior iliac spine (ASIS). One of the complications associated with CPO includes non-union of the osteotomy sites. However, all osteotomy sites including the ASIS have not been simultaneously evaluated. Therefore, we investigated: (1) the bone union status of all osteotomy sites, and (2) the predictors of non-union at one year after CPO based on computed tomography (CT). Hypothesis The bone union status may be different in each osteotomy site. Patients and Methods This retrospective review included 147 hips of 124 patients with symptomatic acetabular dysplasia who underwent CPO from 2011 to 2018. At one year postoperatively, we evaluated the bone union status of all osteotomy sites: the ASIS, ischium, pubis, and ilium using CT and investigated the predictors for achieving bone union. Results Bone union was confirmed in both the ASIS and ilium in all cases. In contrast, ischial and pubic non-union was confirmed 15/147 hips (10.2 %) and 42/147 hips (28.5 %), respectively. The multivariate analysis revealed that the predictors of ischial non-union were both large width of the gap at the pubic osteotomy site and small postoperative acetabular roof obliquity, and that the predictor of pubic non-union was large width of the gap at the pubic osteotomy site. Discussion At one year after CPO, both the ASIS and ilium obtained complete bone union, while ischial and pubic non-union were observed. Large width of the gap at the pubic osteotomy site was the predictor of both ischial and pubic non-union. In CPO, sufficient bone union can be achieved at the ASIS and the ilium, while it is necessary to reduce the width of the gap at the pubic osteotomy site to prevent ischial and pubic non-union. Level of evidence IV; retrospective study.

Background Although several morphological abnormalities or variances of the hip joint have been proposed to be associated with hip joint degeneration, few studies have investigated any radiological features in patients with transient osteoporosis of the hip (TOH). The purpose of this study is to evaluate the morphological variances of the hip joint in TOH patients radiographically. Methods The TOH group consisted of 31 hips in 31 patients. Age- and gender-matched asymptomatic hips in patients with unilateral osteonecrosis of the femoral head were served as controls. Radiographs and MRI were utilized to examine the following parameters: acetabular dysplasia, acetabular overcoverage, acetabular retroversion, and asphericity of the femoral head–neck junction. Also, localization of the main bone marrow edema (BME) lesion was investigated. Results TOH patients had a significantly higher incidence of acetabular retroversion (52% with a positive cross-over sign and 29% with posterior wall deficiency) than the controls (13%, P = 0.0023; 6%, P = 0.043, respectively), which was also confirmed by smaller acetabular anteversion angles on axial MRI. In addition, TOH patients tended to show asphericity of the anterior femoral head–neck junction compared to controls (39% vs. 13%, P = 0.040). In 90% of the TOH patients, the main BME lesion was located in the subchondral area of the superior portion of the femoral head, and 77% of the lesion were recognized as a band-like pattern in MRI. Conclusions Acetabular retroversion and asphericity of the femoral head–neck junction were more commonly observed in TOH patients compared to controls. The main BME lesion was most frequently located in the superior portion of the femoral head.

Background Transtrochanteric anterior rotational osteotomy (ARO) for osteonecrosis of the femoral head (ONFH) can preserve for a long-time collapsed femoral head. Progressive collapse of anteriorly-transposed necrotic lesion leads to secondary arthritic changes and clinical failure. Critical factors influencing collapse of the transposed necrotic lesion after ARO remain largely unknown. Therefore, we performed a retrospective study of ARO to determine: (1) if preoperative collapse influences collapse of the transposed necrotic area, (2) if any other factor may influence collapse of the transposed necrotic area. Hypothesis We hypothesized the degree of preoperative femoral head collapse influences progressive collapse of the transposed necrotic lesion after ARO. Materials and methods We reviewed 47 hips in 42 patients with ONFH treated with ARO between 2000 and 2005 with a mean follow-up of 11.4 years (10–14 years). The occurrence of progressive collapse of the transposed necrotic lesion after ARO was examined using lateral radiographs taken at least once every year after ARO. The following factors were statistically analyzed: age, sex, body mass index, Harris Hip Score (HHS), preoperative level of collapse, extent of the necrotic lesion and postoperative intact ratio (ratio of the transposed intact articular surface of the femoral head). Results Progressive collapse of the transposed necrotic lesion (progressive collapse group) was seen in 17 hips (36%) during a mean period of 1.8 years (0.5–3.7 years) after ARO, which has developed within 4 years in all cases. Preoperative level of collapse in the progressive collapse group (4.4 ± 1.4 mm) was significantly larger than that in the non-progressive collapse group (2.1 ± 1.0 mm), which was independently associated with progressive collapse of the transposed necrotic lesion in multivariate analysis (P

Highlights • We report a periprosthetic fracture following the use of a discontinued prosthesis. • Marked bone ongrowth on the thrust plate made it difficult to remove. • A long distally fixed intramedullary stem was selected for revision. • Sufficient implant preparation based on precise preoperative planning is necessary., Introduction The thrust plate hip prosthesis (TPP; Zimmer, Winterthur, Switzerland) is a hip prosthesis that is no longer in production. Few reports have focused on periprosthetic fractures following total hip arthroplasty (THA) with the use of a TPP. Presentation of case We report a 57-year-old woman with a periprosthetic femoral fracture 13 years after THA with the use of a TPP. A plain radiograph showed a displaced subtrochanteric fracture of the right femur just below the distal tip of the lateral plate without implant loosening. She underwent revision surgery with a long distally fixed intramedullary stem in conjunction with a plate and cable system. Three months after surgery, bone union was confirmed using radiography and the patient was clinically asymptomatic. Discussion We encountered three major problems while planning surgical treatment, these being, discontinuation of the TPP system, loss of proximal femoral cancellous bone, and difficulties with the type of subtrochanteric fracture. After considering these problems, we planned revision surgery using a long distally fixed intramedullary stem in conjunction with a plate and cable system. Conclusion This case shows that sufficient implant preparation based on precise preoperative planning is necessary to obtain good clinical results for the surgical treatment of periprosthetic femoral fractures following THA with the use of a TPP.

Background Glucocorticoid usage, a leading cause of osteonecrosis of the femoral head (ONFH), and its prevalence was reported in 25%-50% of non-traumatic ONFH patients. Nevertheless, there have been no unified criteria to classify glucocorticoid-associated ONFH (GA-ONFH). In 2015, the Association Research Circulation Osseous addressed the issue of developing a classification scheme. Methods In June 2017, a task force was set up to conduct a Delphi survey concerning ONFH. The task force invited 28 experts in osteonecrosis/bone circulation from 8 countries. Each round of the Delphi survey consists of questionnaires, analysis of replies, and feedback reports to the panel. After 3 rounds of the survey, the panel reached a consensus on the classification criteria. The response rates were 100% (Round 1), 96% (Round 2), and 100% (Round 3), respectively. Results The consensus on the classification criteria of GA-ONFH included the following: (1) patients should have a history of glucocorticoid use >2 g of prednisolone or its equivalent within a 3-month period; (2) osteonecrosis should be diagnosed within 2 years after glucocorticoid usage, and (3) patients should not have other risk factor(s) besides glucocorticoids. Conclusion Association Research Circulation Osseous established classification criteria to standardize clinical studies concerning GA-ONFH.

Highlights • We report a transient epiphyseal lesion of femoral head after hip dislocation. • On MRI performed two days after dislocation, no bony injuries were observed. • Hip pain and a transient epiphyseal lesion appeared four months after dislocation. • Hip pain and a transient lesion disappeared after two-month conservative therapy. • Prolonged rest after the injury may contribute to an insufficiency fracture., Introduction We experienced a rare case in which magnetic resonance imaging (MRI) showed a transient epiphyseal lesion of the femoral head four months after traumatic hip dislocation. To our knowledge, there have been no previously published reports on the development of such transient lesions after traumatic hip dislocation involving no abnormalities just after dislocation. Presentation of case We report a 22-year-old man who showed a transient epiphyseal lesion of the femoral head after traumatic hip dislocation. On MRI performed two days after dislocation, no bony injuries were observed around the hip joint. Four months after dislocation, the patient suddenly experienced right hip pain without any new trauma or injury. A low-intensity band convex to the articular surface was apparent above the epiphyseal scar on T1-weighted imaging, and bone marrow edema was observed around the band lesion on short-tau inversion recovery imaging. Following a two-month period of non-surgical conservative therapy, the patient’s hip pain resolved and the low-intensity band was no longer observed on follow-up MRI. Discussion Although the detailed pathogenesis of this transient changes was unclear, we speculate that prolonged rest after traumatic hip dislocation may contribute to bone insufficiency, resulting in an insufficiency fracture of the femoral head. Conclusion This study suggests that transient epiphyseal lesions of the femoral head may occur in patients with a history of traumatic hip dislocation associated with an adapted long-term rest.

Purpose To assess the distributions of stress, strain, and fractured areas using a finite element model (FEM), and examine the osteoclastic activity histopathologically in osteonecrosis of the femoral head. Methods Three femoral heads were obtained during hip arthroplasty for femoral head osteonecrosis. One sample with a normal area, two samples with a non-sclerotic boundary without collapse (Type 1), two samples with a non-collapsed sclerotic boundary (Type 2), and two samples with a collapsed sclerotic boundary (Type 3) were collected from each femoral head for the FEM and histopathological analyses. FEM was performed using CT data, and the distributions of von Mises equivalent stress, octahedral shear stress, octahedral shear strain, and simulated fractured area were evaluated. Furthermore, the osteoclast count at the boundary was compared for each type. Results In normal and Type 1 samples, the distributions of von Mises equivalent stress, octahedral shear stress, octahedral shear strain, and the fractured area were equally concentrated along the whole analytical range; however, in the Type 2 and 3 samples, they were concentrated along the thickened bone trabeculae at the boundary, which corresponded to the fractured area. Histopathologically, a significantly increased osteoclast number was observed only at the collapsed sclerotic boundary. Conclusion These results demonstrated that both shear stress and shear strain tend to be concentrated on thickened bone trabeculae at the boundary. Fracture analyses revealed that the boundary of sclerotic changes, which results from the repair process, may be the starting point of the fracture. Additionally, the osteoclastic activity increases after collapse.

Background Reconstructing both coracoclavicular ligaments following acromioclavicular dislocation has recently been reported to restore the function of the acromioclavicular joint better than traditional procedures. Knowing the appropriate position and orientation of the bone tunnels and the potential risks of neurovascular injuries leads to safe reconstruction. We aimed to answer the following questions: what is the difference in the accurate clavicular bone tunnel positions (BTPs) during coracoclavicular ligament reconstruction between sex, and what are the potential risks for neurovascular injuries? Hypothesis The BTPs differ by sex at the site of coracoclavicular ligament reconstruction. Patients and methods We introduced two Kirschner wires into 25 cadaver shoulders (17 male, 8 female), one through the insertion center of the trapezoid ligament and one through the conoid ligament, and measured the distance from the respective Kirschner wire insertion points to the bony landmarks of the clavicle and the oblique angle of each Kirschner wire. The shortest distance from the insertion point of each Kirschner wire to the suprascapular nerve and artery was also measured. Results While the distance from the acromioclavicular joint to the respective Kirschner wire insertion points tended to be longer in males, the ratio of these insertion points to total clavicle length was constant. Other measurements for respective Kirschner wire insertions to the bony landmarks and neurovascular structures were comparable, as were abduction and retroversion angles. The distance from the suprascapular nerve to the insertion point of the conoid ligament at the coracoid process was 13.8 ± 4.0 mm, while the distance from the suprascapular artery was 7.1 ± 3.3 mm. Discussion Appropriate position and orientation of the bone tunnels, and the ratio of the BTPs to the total clavicular length, aid surgeons in performing the reconstruction. The conoid ligament insertion on the coracoid was just proximal to the suprascapular artery, so surgeons should be careful with conoid insertion. Level of evidence V, cadaver study.

Highly cross-linked polyethylene (HXPE) in total hip arthroplasty (THA) has been shown to significantly decrease wear rates compared with conventional polyethylene (CPE). However, crosslinking, thermal treatment and oxidation can decrease the mechanical properties of PE, and several cases of fracture of remelted HXPE liners were reported. We present, for the first time, unexpected failures of THA with the use of annealed HXPE liners in two patients occurring at 7 and 8 years after operation. Operative findings revealed dislocated liners from the metal shell and a fracture of the superior rim at the rim-dome junction in both liners. Scanning electron microscopy showed that the cracks initiated at the rim and propagated toward the articular surface. Both liners showed generally a low amount of oxidation (less than 1.00) at the articular surface and low wear rates; however, oxidation at the rim was relatively higher (mean 1.55). These findings suggested that decreased mechanical properties at the rim-dome junction due to cross-linking, annealing and oxidation might have been caused breakage of the HXPE liners after a long implantation time, although the annealed HXPE achieved low degree of wear.

This study investigated the radiological factors that correlated with progression of collapse and joint space narrowing after transtrochanteric posterior rotational osteotomy (PRO) for osteonecrosis of the femoral head.This study reviewed 51 hips in 47 patients with a mean follow-up of 11 years (5-20). The subjects included 29 males and 18 females with a mean age of 34 years (12-54) at the time of surgery. The 51 hips were divided into two groups based on the radiological outcome (group I: evidence of progression of collapse and/or joint space narrowing, group II: no evidence of either progression of collapse or joint space narrowing). Both clinical and radiological factors were analyzed by both univariate and multivariable analyses.Six hips were categorized as group I and 45 hips were categorized as group II. The postoperative intact ratio and preoperative stage were significantly correlated with the radiological outcome in both univariate (P 0.0001, P = 0.006) and multivariate (P = 0.0014, P = 0.0039) analysis. The cutoff point for the postoperative intact ratio (the minimum ratio required to prevent both progression of collapse and joint space narrowing) was 36.8 %.The results of this study indicate that the postoperative intact ratio is one of the main influences on progression of collapse and/or joint space narrowing after PRO, and should be at least 36.8 %. An increased awareness of this critical ratio would be useful for planning the optimal use of this procedure.

Acetabular retroversion is observed in hips after various pediatric hip diseases. This study sought to examine the frequency of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease and its correlation with the prominence of the ischial spine.We retrospectively investigated the version and morphological features of the acetabulum using pelvic radiographs after Legg-Calvé-Perthes disease (107 affected hips treated non-operatively and 72 unaffected hips from the contralateral side). The diagnosis of acetabular retroversion was made based on the presence of a positive cross-over sign on anteroposterior pelvic radiographs. The correlation between the presence of a positive cross-over sign and modified Stulberg classes, the onset age of Legg-Calvé-Perthes disease, radiographic parameters for acetabular dysplasia and the prominence of the ischial spine were examined.The prevalence of a positive cross-over sign was 49.5 % (45 of 91 hips) in affected hips and 45.8 % (33 of 72 hips) in unaffected hips. Hips with a positive cross-over sign were significantly coexistent bilaterally. The prevalence of prominence of the ischial spine in the positive cross-over sign group was 71.4 % in the affected side and 81.8 % in the unaffected side, indicating a significant correlation between the cross-over sign and the prominence of the ischial spine in both affected and unaffected hips. The positive cross-over sign did not have any correlation with the parameters for acetabular dysplasia and the onset age, however, had a significant correlation with the severity of the femoral head deformity.High prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease was demonstrated. Symmetric acetabular deformity and the coexistence of prominence of the ischial spine suggested the effects of the Legg-Calvé-Perthes disease lesions on the skeletal development of the whole pelvis. Further follow-up is needed to clarify the pathological significance of acetabular retroversion after Legg-Calvé-Perthes disease.

Transtrochanteric anterior rotational osteotomy for osteonecrosis of the femoral head should be performed to obtain34% of the ratio of transposed intact posterior articular surface to the acetabular weight-bearing area. Therefore, the presence of acetabular dysplasia is unfavorable in obtaining this ratio. Between 1999 and 2005, we performed the modified Spitzy shelf acetabuloplasty combined with anterior rotational osteotomy for three patients (four hips) with acetabular dysplasia. In this study, we retrospectively evaluated the midterm results of this combined surgery.Patients comprised one man and two women with a mean age of 29 years at the time of surgery. Mean follow-up was 7.5 years. The average preoperative Harris hip score of 65.5 points increased to an average of 79.3 points at the latest follow-up. None of the hips required conversion to total hip arthroplasty during the follow-up periods. The average postoperative intact ratio without a shelf procedure was 23%, and with a shelf procedure, this ratio increased to be 58%. As a result, collapse progression was not observed in any of the four hips.Our results suggest that anterior rotational osteotomy combined with shelf acetabuloplasty may be a surgical option for osteonecrosis of the femoral head with acetabular dysplasia. Further studies with a larger patient population are necessary to clarify appropriate indications and limitations of this combined surgery.

Background Transtrochanteric anterior rotational osteotomy (ARO) is joint-preserving surgery for patients with osteonecrosis of the femoral head (ONFH). During ARO, femoral neck-shaft varus angulation by changing intertrochanteric osteotomy plane is often designed to obtain a sufficient post-operative intact ratio. However, the effect of intertrochanteric osteotomy plane on post-operative femoral anteversion has not been well examined. Therefore we performed a simulation study of ARO to determine how intertrochanteric osteotomy plane and pre-operative femoral anteversion affect both femoral neck-shaft varus angle and post-operative femoral anteversion. Hypothesis Both femoral neck-shaft varus angle and post-operative femoral anteversionare predicted by intertrochanteric osteotomy plane and pre-operative femoral anteversion in ARO. Materials and methods Using CT-data obtained from 10 hips in 10 patients with ONFH, ARO was simulated. On anteroposterior view, basic intertrochanteric osteotomy line (AP-view line) was defined as the perpendicular line to the femoral neck axis. On lateral view, basic intertrochanteric osteotomy line (lateral-view line) made through the cut surface of greater trochanter was defined as the perpendicular line to the lateral axis of the femur. By changing either AP-view or lateral-view line, 49 ARO models/hip were produced, in which femoral neck-shaft varus angle and post-operative femoral anteversion were assessed. Results With increase in the vertically-inclined degree of AP-view line, both neck-shaft varus angle and post-operative femoral anteversion increased. With increase in the posteriorly-tilted degree of lateral-view line, neck-shaft varus angle increased, whereas post-operative femoral anteversion decreased. The approximation equations based on the multiple regression analyses were as follows: neck-shaft varus angle ≈ vertically-inclined degree of AP-view line × 0.9 + posteriorly-tilted degree of lateral-view line × 0.8 + pre-operative femoral anteversion × 0.7; post-operative femoral anteversion ≈ vertically-inclined degree of AP-view line × 1.1–posteriorly-tilted degree of lateral-view line × 0.8. Discussion The post-operative morphology of proximal femur was nearly defined by intertrochanteric osteotomy plane with pre-operative femoral anteversion, which is useful for pre-operative planning in terms of both achieving asufficient post-operative intact ratio and maintaining femoral anteversion. Level of evidence Level IV case series without control group.

When treating osteonecrosis of the femoral head (ONFH), it is important to define the site and size of necrotic lesions, in general based on the detection of the demarcating area. Although a plain radiograph is routinely performed, it does not always make the lesion clear, especially in early stage cases. On the other hand, magnetic resonance (MR) imaging usually detects the necrotic lesion more clearly even at the early stage [1, 2], and therefore MR imaging is widely used in both the diagnosis and the selection of treatment for ONFH [3, 4].

The purpose of this study was to quantify the effects of femoral offset and head size on range of motion (ROM) after total hip arthroplasty. Modular prostheses were implanted into 11 cadaveric hips using a posterolateral approach and tested for ROM with 3 different offsets and 5 different femoral head sizes. Increasing the femoral offset to 4 and 8 mm resulted in 21.1 degrees and 26.7 degrees of improved flexion, and 13.7 degrees and 21.2 degrees of improved internal rotation, respectively. The ROM improved in a head size-dependent manner primarily because of increasing the jumping distance of the femoral head rather than delaying any impingement. In contrast, the effectiveness of femoral offset was driven by delayed osseous impingement.

A 49-year-old woman had suffered from a left hip pain. Radiographs showed a focal loss of radiodensity in the left femoral head and neck, and magnetic resonance imaging revealed a bone marrow edema in the femoral head. She was diagnosed as transient osteoporosis of the hip and was treated conservatively. Three years later, right hip pain occurred. Based on the imaging appearances, she was diagnosed as transient osteoporosis of the hip in the right and was treated conservatively. Five years after the onset of right hip pain, she suffered from a recurrent right hip pain. Imaging findings were similar to those obtained 5 years before. Five months after the onset of pain, both hip pain and imaging abnormalities disappeared by the same treatments as the previous episodes. This case was considered to have recurrent transient osteoporosis of the hip.

For osteoarthritis hips due to severe acetabular dysplasia such as Crowe type 3 or 4, placement of the socket is a difficult procedure in total hip arthroplasty. Because the acetabular bone stock is poor, suitable location for the socket is very limited with respect to achieving good coverage with the host bone. A 51-year-old woman who had an osteoarthritis hip with a large leg length discrepancy due to severe acetabular dysplasia required total hip arthroplasty. The purpose of the total hip arthroplasty was to improve the hip disorder as well as to reduce the leg length discrepancy to achieve good gait function. We present technical solutions to aid the surgeons in placing the acetabular socket at the proper location by using computed tomography–based navigation system.

We investigated the outcome of the contralateral hip in patients with rapidly destructive arthrosis of the hip after total hip arthroplasty. Twenty-four patients were included, and the mean duration of radiographic follow-up was 7.0 years (range, 3.8-17.8 years). To assess the capable parameters for predicting the development of osteoarthritis, we evaluated the receiver operating characteristic curves. Three (12.5%) of 24 patients developed osteoarthritis and underwent total hip arthroplasty within 3.8 to 6.5 years. In these 3 patients, both the acetabular-head index and the center-edge angle were significantly lower than those in patients without osteoarthritis (P < .005). Based on the receiver operating characteristic curves, both an acetabular-head index of less than 72% and a center-edge angle of less than 16 degrees were considered to be associated with the development of osteoarthritis.

Some animal studies and magnetic resonance imaging studies suggest that there may exist a relationship between abnormal lipid metabolisms and osteonecrosis. The purpose of this study was to examine the size of bone marrow fat cells in the early osteonecrosis femoral head using autopsy specimens. We compared the size of bone marrow fat cells in the viable areas in the following three autopsy groups: the early osteonecrosis group (4 femoral heads); the steroid-administered group (without osteonecrosis) (n = 10), and the normal group (n = 19). In addition, after adjusting for age and sex, the size of bone marrow fat cells was compared using multiple regression analysis. The size of bone marrow fat cells was significantly larger in the early osteonecrosis group (84.7+/-5.5 microm) than in both the steroid-administered group (75.3+/-4.3 microm) and the normal group (76.3+/-4.9 microm) (p

Background Transtrochanteric anterior rotational osteotomy (ARO) for osteonecrosis of the femoral head (ONFH) can preserve for a long-time collapsed femoral head. Progressive collapse of anteriorly-transposed necrotic lesion leads to secondary arthritic changes and clinical failure. Critical factors influencing collapse of the transposed necrotic lesion after ARO remain largely unknown. Therefore, we performed a retrospective study of ARO to determine: 1) if pre-operative collapse influences collapse of the transposed necrotic area, 2) if any other factor may influence collapse of the transposed necrotic area. Hypothesis We hypothesized the degree of pre-operative femoral head collapse influences progressive collapse of the transposed necrotic lesion after ARO. Materials and methods We reviewed 47 hips in 42 patients with ONFH treated with ARO between 2000 and 2005 with a mean follow-up of 11.4 years (10–14 years). The occurrence of progressive collapse of the transposed necrotic lesion after ARO was examined using lateral radiographs taken at least once every year after ARO. The following factors were statistically analyzed: age, sex, body mass index, Harris Hip Score (HHS), pre-operative level of collapse, extent of the necrotic lesion and post-operative intact ratio (ratio of the transposed intact articular surface of the femoral head). Results Progressive collapse of the transposed necrotic lesion (progressive collapse group) was seen in 17 hips (36 %) during a mean period of 1.8 years (0.5–3.7 years) after ARO, which has developed within 4 years in all cases. Pre-operative level of collapse in the progressive collapse group (4.4 ± 1.4 mm) was significantly larger than that in the non-progressive collapse group (2.1 ± 1.0 mm), which was independently associated with progressive collapse of the transposed necrotic lesion in multivariate analysis (P Discussion The current study suggests that progressive collapse of the transposed necrotic lesion after ARO depends mainly on the pre-operative level of collapse (cutoff point = 2.98 mm). Level of evidence IV; retrospective case series.

Background During transtrochanteric rotational osteotomy (RO), it is important to preserve the posterior column artery (PCA), which is generally located in the adipose tissue underneath the quadratus femoris muscle (QF). If there is a defect in the QF, the risk of injuring the PCA, subsequently resulting in total necrosis of the femoral head, may increase. Therefore we investigated (1) the frequency of defects of the QF at the time of RO, (2) clinical outcome of RO based upon a defect of the QF. Hypothesis The presence of defects of the QF at the time of RO could be detected pre-operatively by magnetic resonance imaging. Methods RO was performed in 124 hips between 2001 and 2010. In all, 95 of the hips were in male patients and 29 in female patients. The mean age was 45.4 years (range: 11–61 years) at the time of surgery and MRI was performed before RO in all cases. We retrospectively evaluated the progression of a collapse through 3 years after RO. Results MRI showed a defect in the QF in four hips (3.2 %) (two males, two females), all of which were confirmed intraoperatively. Among the four patients, one (25 %) underwent total hip arthroplasty because of varus deformity of the osteotomy site due to total necrosis of the femoral head 1 year after RO. The 120 hips with a normal QF showed no evidence of total necrosis or progression of necrosis of the femoral head, indicating that the presence of defects of the QF may increase the risk of poor survivorship of this procedure. Conclusions Defects of the QF have been reported to occur in 1–2 % of all patients, whereas in our study the incidence in ON was approximately 3 %. In ON patients with QF defects, pre-operative MRI evaluation of the QF appears to be important when planning RO, followed by a carefully performed surgical procedure. Level of evidence IV retrospective case series without control group.