PEMF is currently approved by the FDA for adjunctive treatment of lumbar/cervical spine fusion and for treatment of long-bone non-unions. Soft tissues are a potential new therapeutic application for PEMF due to pre-clinical studies showing a reduction of inflammatory markers following PEMF exposure. The aim was therefore to investigate the structural/functional effects of PEMFs on tendon-to-bone and tendon-to-tendon healing in a rotator-cuff (RC) and Achilles tendon (AT) repair model, respectively. RC study: Adult male rats (n=280), underwent bi-lateral supraspinatus tendon transections with immediate repair followed by cage activity until sacrifice (4, 8, and 16 weeks). Non-controls received PEMF for 1, 3, or 6 hours daily. AT study: Male rats underwent acute, complete transection and repair of the Achilles tendon (FULL, n=144) or full thickness, partial width injury (PART, n=160) followed by immobilization for 1 week. Sacrifice was at 1, 3, and 6 weeks. Outcome measures included passive joint mechanics, gait analysis, biomechanical assessments, histological analysis of the repair site and mCT (humerus) assessment (FULL only). RC study: Significant increases in modulus, stiffness, bone mineral content and improved collagen organization was observed for the PEMF groups. No differences in joint mechanics and ambulation were observed. AT study: A decrease in stiffness and limb-loading rate was observed for the PEMF groups for the FULL groups, whereas an increase in stiffness with no change in range-of-motion was seen for the PART groups. The combined studies show that PEMF can be effective for soft tissue repair but is dependent on the location of application.
The crescent sign is thought to be an early indicator of collapse in osteonecrosis of the femoral head. However, the formation mechanism of the crescent sign is still not quite clear. The purpose of this study was to utilize the two-dimensional finite element model analysis (FEA) technique to analyze mechanical function of different structures and intraosseous fluid in the femoral head under the stress of physiological loading. We wished to answer the following question: which structure or structures' failure are the main causes of collapse in osteonecrosis of the femoral head (ONFH)? Based on two femoral head specimens obtained during THA (one with osteonecrosis of the femoral head with crescent sign formation and the other with most of the cancellous bone eroded by tumor cells without collapse), three groups of ten models were designed. Group A were standard femoral heads composed of subchondral plate, cancellous bone, intraosseous fluid, and cortical bone with 50 mm in diameter, Group B included ONFH, and Group C was based on a tumor-eroded femoral head. Previously reported mechanical property parameters were used in the FEA calculation. The strain and Von Mieses stress mechanics parameters of fifteen points (with the same coordinates) in the junction between subchondral plate and cancellous bone were harvested and compared.Introduction
Methods
Multifocal osteonecrosis (ON) was defined by Mont et al. as a disease involving three or more anatomic sites. Few papers have been published on the Chinese experience. The purpose of this study was to characterize the experience with multifocal ON in order to make an earlier diagnosis for more patients with this disorder. From 2003 to 2008, thirty nine patients with multifocal ON were identified in our clinical practice. Among them, thirty seven patients were post-SARS rehabilitating patients and two patients were found in clinic. All patients had a history of high dose corticosteroid therapy. The diagnosis was done by magnetic resonance imaging (MRI) and radiographs. All patients were treated by drug or other joint-salvaging procedure. Three patients had bilateral total hip arthroplasties.Introduction
Methods
