Role of mitogen-activated protein kinases in hydrogen peroxide-induced cell death in osteoblastic cells.

Oxidative stress is known to induce cell death in a wide variety of cell types, apparently by modulating intracellular signaling pathways. However, the underlying mechanism by which oxidants induce cell death remains unclear. The present study was undertaken to determine the role of the mitogen-activated protein kinase subfamilies in hydrogen peroxide (H2O2)-induced cell death of osteoblastic cells. H2O2 resulted in a time- and dose-dependent cell death, which was, in part, attributed to apoptosis. H2O2-induced cell death was prevented by iron chelator, hydroxyl radical scavengers. But H2O2-induced cell death was not affected by 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase activation. H2O2 treatment caused a transient activation of extracellular signal-regulated kinase (ERK), followed by sustained activation. Cell death induced by H2O2 was prevented by PD98059, an inhibitor of ERK upstream kinase MEK1/2. But H2O2 induced a transient activation of p38 and c-Jun N-terminal kinase (JNK) without sustained activation and inhibitors of these kinses were not effective in preventing the cell death. H2O2 increased Bax expression and produced hyperpolarization of mitochondrial membrane potential and its effect was prevented by PD98059. The ERK activation and cell death induced by H2O2 were not dependent on the phosphorylation of epidermal growth factor receptor. Taken together, these findings suggest that the ERK signaling pathway plays an active role in mediating H2O2-induced apoptosis of osteoblasts and functions upstream of mitochondria-dependent pathway to initiate the apoptotic signal.

A posterior approach to primary total hip arthroplasty with soft tissue repair.

To determine whether repair of the posterior soft tissue structures affects dislocation rate, a comparison of the posterolateral approach with and without a posterior soft tissue repair in primary total hip arthroplasty was done. Between January 1993 and December 1998, 250 consecutive primary total hip arthroplasties (220 patients) without a posterior soft tissue repair followed by 96 consecutive primary total hip arthroplasties (83 patients) with a posterior soft tissue repair in the posterolateral approach were done. With the exception of a posterior soft tissue repair, all surgical procedures were done in the same manner. A dislocation rate of 6.4% in 250 hips without a posterior soft tissue repair in the posterolateral approach was reduced to 1% in 96 hips with a posterior soft tissue repair. The results were statistically significant. The current results indicate that the posterior structures should be preserved as much as possible and repaired to reduce dislocation in the posterolateral approach.

Radiologic change around bilateral femoral stems in nonHodgkin's lymphoma.

Bilateral pathologic femoral neck fractures caused by nonHodgkin's lymphoma occurred consecutively in a 66-year-old man. Spontaneous bony stabilization after initial extensive bone resorption around the femoral stems after hybrid total hip arthroplasties was observed. This is the first well-documented report on bone change around the femoral stems after bilateral total hip arthroplasties in pathologic femoral neck fractures caused by nonHodgkin's lymphoma.

Chronic radial head dislocation in children, Part 2: results of open treatment and factors affecting final outcome.

Fifteen elbows (3 congenital, 12 traumatic) in 14 children (mean age 9.5 years) with chronic radial head dislocation for at least 3 months (range 3-180 months) underwent radial head-sparing reconstructive surgery and were followed up at an average of 43.5 months postoperatively (range 12-105 months). At follow-up, the patients were evaluated radiographically and clinically using range-of-motion measurements and an elbow performance score based on four parameters (deformity, pain, motion, function). Ten cases had excellent results, two had good results, two had fair results, and one case had poor results. Scores at follow-up were evaluated with seven preoperative factors. Among those, the degree of preoperative carrying angle asymmetry associated with flexion contracture correlated significantly with the elbow scores. The most common complication was loss of pronation. The authors advocate radial head reduction and reconstruction in chronic radial head dislocations in children after obtaining informed consent from patient and parents.