Introduction. Subchondral insufficiency fracture (SIF) needs to be differentiated from osteonecrosis. The purpose of this study was to evaluate the imaging and histopathological findings of patients 60 years or older with radiological evidence of subchondral collapse of the femoral head. Methods. We reviewed 77 consecutive hips in 56 patients aged 60 years or older, which showed subchondral collapse on radiographs. According to the shapes of low-intensity bands on T1-weighted images of magnetic resonance imaging (MRI), the patients were divided into 2 groups. Group A showed a concavity of the articular surface: characteristic appearances of osteonecrosis, and Group B showed an irregular convexity of the articular surface: characteristic appearances of SIF. Results. Thirty-four patients (60.7%) were categorized as Group A and 22 patients (39.3%) as Group B. All the cases in Group A had a history of corticosteroid intake or alcohol abuse. In Group B, the proportion of women as well as unilateral involvement was significantly higher than those in Group A. In 30 cases with histopathological examination, 16 were in Group A and 14 were in Group B. All the cases in Group A demonstrated characteristic features of osteonecrosis. In Group B, the band on T1-weighted images corresponded to viable reparative tissue including granulation tissue and fracture callus, which are characteristic histological findings in SIF. Conclusion. The results of this study suggest that the patient's clinical features as well as the shapes of the low-intensity bands on T1-weighted images provide a clinically concise tool for the differentiation of SIF from osteonecrosis

The use of retrograde femoral intramedullary nails in children for deformity correction is controversial. It is unknown if the injury to the central part of the growth plate results in premature bony union, leading to limb deformities or discrepancies. The aim of this study was to assess physeal healing and bone growth after insertion of a retrograde femoral nail thorough the centre of the physis in a skeletally immature experimental porcine model. Eleven immature pigs were included in the study. One leg was randomised for operation with a retrograde femoral nail (diameter 10.7 mm), whilst the non-operated contralateral remained as control. All nails were inserted centrally in coronal and sagittal plane under fluoroscopic guidance, and the nails spanned the physis. The nails were removed at 8 weeks. Both femora in all animals underwent MRI at baseline (pre-operatively), 8 weeks (after nail removal) and 16 weeks (before euthanasia). Femoral bone length was measured at 5 sites (anterior, posterior, central, lateral and medial) using 3d T1-weighted MRI. Growth was calculated after 8 weeks (growth with nail) and 16 weeks (growth without nail). Physeal cross-sectional area and percentage violated by the nail was determined on MRI. Operated side was compared to non-operated. Corresponding 95% confidence intervals were calculated. No differences in axial growth were observed between operated and non-operated sides. Mean growth difference was 0,61 mm [−0,78;2,01] whilst the nail was inserted into the bone and 0,72 mm [−1,04;1,65] after nail removal. No signs of angular bone deformities were found when comparing operated side to non-operated side. No premature bony healing at the physis occurred. Histology confirmed fibrous healing. Mean physeal violation was 5.72% [5.51; 5.93] by the femoral nail. The insertion of a retrograde femoral nail through the centre of an open physis might be a safe procedure with no subsequent growth arrest. However, experiments assessing the long term physeal healing and growth are needed

Introduction. Subchondral insufficiency fracture of the femoral head (SIF) often occurs in osteoporotic elderly patients. Patients usually suffer from acute hip pain without any obvious antecedent trauma. Radiologically, a subchondral fracture is seen mainly in the superolateral portion of the femoral head. The T1-weighted magnetic resonance (MR) images show a low-intensity band in the subchondral area of the femoral head, which tends to be irregular, disconnected, and convex to the articular surface. This low-intensity band in SIF was histologically proven to correspond to the fracture line with associated repair tissue. Some cases of SIF resolve after conservative treatment, while others progress until collapse, thereby requiring surgical treatment. The prognosis of SIF remains unclear. This study investigated the risk factors that influence the prognosis of SIF based on the progression of the collapse. Methods. Between June 2002 and June 2008, seventeen patients diagnosed as SIF were included in this study. Sequential radiographs were evaluated for the presence of progression of the collapse. The clinical profiles, including the age, body mass index (BMI), follow-up period and Singh index were examined. The morphological characteristics of the low intensity band on the T1-weighted magnetic resonance images were also examined, with regard to the band length, band thickness and band length ratio; which is defined as a proportion of the band length to the weight-bearing portion of the femoral head. Results. Radiographically, a progression of the collapse was observed in 8 of 17 (47.1%) patients. The band length in patients with progression of the collapse (mean: 22.6 mm) was significantly larger than that in those without progression of the collapse (mean: 12.3 mm; P < 0.05). The band length ratio in patients with progression of the collapse (mean: 73.3 %) was also significantly higher than that in those without progression of the collapse (mean: 42.3 %; P < 0.01). No significant differences were seen in the other variables (the age, BMI, follow-up period, Singh index, and band thickness). Conclusion. One of the important differential diagnoses in determining SIF may include osteonecrosis. The shape of the low signal intensity band on the T1-weighted MR images is one of the characteristic findings in SIF: namely, it is generally irregular, serpiginous, convex to the articular surface, and often discontinuous. This low-intensity band is generally surrounded by bone marrow edema. Histopathologically the band in SIF represents the fracture line with associated repair tissue. On the other hand, in osteonecrosis, since the low-intensity band represents repair tissue, it is generally smooth and circumscribes all of the necrotic segments. In this study, the prognosis of SIF varied even though all the patients received similar non-operative treatments. If the prognosis for SIF can be predicted at the early stage, it would allow the design of optimal treatments in each patient. In this preliminary investigation, both the band length and band length ratio were demonstrated to be useful when selecting the optimal treatment for SIF

Summary Statement. Simulated increases in body weight led to increased displacement, von Mises stress, and contact pressure in finite element models of the extended and flexed knee. Contact shifted to locations of typical medial osteoarthritis lesions in the extended knee models. Introduction. Obesity is commonly associated with increased risk of osteoarthritis (OA). The effects of increases in body weight and other loads on the stresses and strains within a joint can be calculated using finite element (FE) models. The specific effects for different individuals can be calculated using subject-specific FE models which take individual geometry and forces into account. Model results can then be used to propose mechanisms by which damage within the joint may initiate. Patients & Methods. Twelve subject-specific FE models (Abaqus 6.11) of three normal healthy subjects were created by combining geometry (3T T1-weighted MRI scans processed using Mimics 13.0, Geomagic Studio 11, and SolidWorks 2010) and load cases (Vicon and AMTI motion analysis data processed within AnyBody Technology Version 3.0 and Matlab R2007a). Model geometry included the femur and tibia (rigid bodies), tibial cartilage and femoral cartilage (E = 12 MPa, ν = 0.45), and menisci (E. circumferential. = 120 MPa, ν. circumferential. = 0.2; E. axial/radial. = 20 MPa, ν. axial/radial. = 0.3). The tibia was held fixed while loads were applied to the centre of mass of the femur. Frictional contact (µ = 0.02) was modelled between soft tissues. Of the twelve models, six were of extended knees and six were of mid-range flexed (∼50°) knees. Each of these six models represented a paired set: a “normal” model and an “increased-load” model. In the flexed knee “increased-load” models, loads were doubled; in the extended knee “increased-load” models, loads were increased to a standard 2000 N compressive load across the joint (approximately three to four times larger than the original loads). Maximum displacements, von Mises stresses, and contact pressures on the articulating tibial cartilage and femoral cartilage surfaces were calculated; results of the “normal” and “increased-load” models were compared. Results. Increasing the applied loads increased the maximum displacements, von Mises stresses, and contact pressures. Contact shifted anteriorly in the extended knee models to typical locations of medial OA cartilage lesions. No contact shift occurred in the flexed knee models; contact remained in typical locations of lateral OA cartilage lesions, but the contact area extended in all directions, and displacements, stresses, and pressures increased. Discussion/Conclusion. Comparing the “normal” and “increased-load” results suggested two potential mechanical mechanisms involved in osteoarthritic cartilage lesion development. Contact shifted to areas of previously-unloaded cartilage in the extended knee “increased-load” models. Cartilage has regional material properties, with stiffer cartilage in areas of frequent contact and loading; shifting contact to areas of less-stiff cartilage could damage the cartilage and lead to degenerative diseases such as OA. Contact did not shift in the flexed knee “increased-load” models. Instead, the displacements, stresses, and pressures increased while the centres of contact remained relatively stationary. If these contact variables increase beyond a threshold magnitude, the cartilage could be damaged, potentially leading to OA

Introduction. In osteonecrosis of the femoral head (ONFH), progression of collapse is influenced by a repair reaction, especially bone resorptive activity, around the necrotic bone. Alendronate is a potent inhibitor of bone resorption by inhibiting osteoclast activity. We performed a clinical study to test if systemic alendronate treatment would prevent the development of collapse in patients with ONFH. Methods. Thirty-three hips in 22 ONFH patients with initial ARCO Stage 1 to 3 were included. Fourteen patients (20 hips) received daily administration of oral alendronate 5mg/day (alendronate group) and 8 patients (13 hips) did not receive alendronate administration (Control group). Baseline investigations included anteroposterior and lateral plain radiographs, T1-weighted magnetic resonance imaging (MRI), and biochemical markers (urinary NTX and serum BAP). Examination of the biochemical markers were repeated at 3, 6, and 12 months, and MRI imaging was repeated at 12 months. At 3 years, clinical symptoms and findings on plain radiographs were compared between the 2 groups. Advancement of ARCO stages or increase of collapse by more than 2 mm were considered as development of collapse. Results. At baseline, there were no significant differences regarding patients' age, distribution of gender, etiology, ARCO radiographic stage, and extent of necrosis between the 2 groups. In the alendronate group, there was an early decrease of osteoclast activity (NTX) and osteoblastic activity (BAP) at 3 months, with significantly larger decrease in NTX (43%) than BAP (21%) at 12 months. At 3 years, development of collapse was observed in 7 hips (54%) of the Control group, and in 3 hips (15%) of the alendronate group. Hip pain was noted in 9 hips (69%) of the Control group, and in 6 hips (30%) of the alendronate group. There was a significant difference oncollapse development and occurrence of hip pain between the two groups (p<0.05). Signal change around the necrotic region on serial MRI images during the first 1 year was observed in 54 % of the Control group, and only 11% of the alendronate group. Conclusion. Alendronate therapy decreased biochemical markers, especially osteoclast activity, after an early period from start of administration. Several clinical studies have shown promising short-term results for prevention of collapse in ONFH by administration of bisphosphonates. The present study showed a significant preventing effect of collapse development by administration of alendronate which was maintained for 3 years of treatment. Low incidence of signal change on serial MRI images may also reflect decrease of repair activity in the alendronate group. Further studies with longer follow-up, larger numbers of patients, and randomized administration of the drug among patients are required., However, alendronate administration may become one of the effective conservative treatments which might obviate the need for osteotomy or replacement surgery in some populations of ONFH patients

Objectives

The objectives of this study were: 1) to examine osteophyte formation, subchondral bone advance, and bone marrow lesions (BMLs) in osteoarthritis (OA)-prone Hartley guinea pigs; and 2) to assess the disease-modifying activity of an orally administered phosphocitrate ‘analogue’, Carolinas Molecule-01 (CM-01).

Objectives

An experimental piglet model induces avascular necrosis (AVN) and deformation of the femoral head but its secondary effects on the developing acetabulum have not been studied. The aim of this study was to assess the development of secondary acetabular deformation following femoral head ischemia.

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection.

The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair.