Chondrocyte apoptosis in response to dislocation of the hip in the rat model.

Abstract

BACKGROUND: Joint dislocation is a traumatic event that can lead to osteoarthritis. The purpose of this paper is to study cartilage changes following prolonged joint dislocation for 1, 2 or 8 h. METHODS: Sprague-Dawley rats (n = 27) were used in this study. Surgical dislocation of the hip under anaesthesia was carried out on the animals. The joints remained dislocated for 1, 2 or 8 h. The joints were subsequently harvested and terminal deoxnucleotidyl transferase-mediated dUTP nick-end labelling testing was carried out to show chondrocyte apoptosis in the femoral head and acetabulum. Using this test, the apoptotic index, which is the proportion of apoptotic chondrocytes to total number of chondrocytes, was calculated. A comparison of apoptotic indices was made among the three groups. RESULTS: The mean apoptotic indices for the femoral head for the 1-, 2- and 8-h groups were 0.065 +/- 0.025, 0.162 +/- 0.031 and 0.201 +/- 0.030, respectively. There was a significant difference (P < 0.05) in the mean apoptotic indices between each of the three groups. For the acetabulum, the mean apoptotic indices were 0.046 +/- 0.012, 0.051 +/- 0.023 and 0.057 +/- 0.031 for the 1-, 2- and 8-h groups, respectively. There was no significant difference (P > 0.05) between each of the three groups. CONCLUSIONS: Dislocation of a joint causes chondrocyte apoptosis. There is a progressive increase in the apoptotic index with prolonged dislocation of the rat hip.