Significant evidence exists that trauma to a joint produced by a single impact load below that which causes subchondral bone fracture can result in permanent damage to the cartilage matrix, including surface fissures, loss of proteoglycan, and cell death. Limited information exists, however, on the effect of a varying impact stress on chondrocyte biophysiology and matrix integrity. Based on our previous work, we hypothesized that a stress-dependent response exists for both the chondrocyte's metabolic activity and viability and the matrix's hydration. This hypothesis was tested by impacting bovine cartilage explants with nominal stresses ranging from 0.5 to 65 MPa and measuring proteoglycan biosynthesis, cell viability, and water content immediately after impaction and 24 hours later. We found that proteoglycan biosynthesis decreased and water content increased with increasing impact stress. However, there appeared to be a critical threshold stress (15-20 MPa) that caused cell death and apparent rupture of the collagen fiber matrix at the time of impaction. We concluded that the cell death and collagen rupture are responsible for the observed alterations in the tissue's metabolism and water content, respectively, although the exact mechanism causing this damage could not be determined.

No abstract

Fixation of periprosthetic supracondylar femur fractures with a locking plate provided satisfactory results in nondiabetic patients. Diabetic patients seem to be at high risk for healing complications and infection.

The treatment of long bone nonunions and fractures with osseous defects is challenging. The results of 26 patients with either a persistent long bone nonunion or an osseous defect after an open fracture were reviewed. Each patient was treated with debridement of devitalized tissue, open reduction and internal fixation, and bone grafting using a mixture of autogenous iliac crest bone graft and medical grade calcium sulfate. The current study evaluated the union rate and associated complications for treatment of these injuries using this protocol. Each nonunion was confirmed intraoperatively, and healing was determined clinically by the patients' return to full activities without pain and radiographically by the presence of bridging trabeculae. Complications included persistent nonunion (four patients), wound drainage (five patients), wound drainage and cellulitis (one patient) and cellulitis alone (one patient). Using this treatment protocol, 22 patients (85%) achieved healing after one surgery and an additional two patients (92%) achieved healing after a second surgery. Medical grade calcium sulfate increases the volume of graft material, facilitates bone formation, and is safe in the treatment of nonunions and fractures with osseous defects.