The response of articular cartilage in joint dislocation is not well documented. We have previously demonstrated that the rate of chondrocyte apoptosis increased with duration of joint dislocation with a significant increase after 1 hour. The purpose of our study was to determine if early joint reduction reduced the rate of chondrocyte apoptosis.

Southern Health animal ethics approval was obtained. 36 Sprague-Dawley rats underwent surgical dislocation of the left hip and the hip was reduced after 1, 2 or 4 hours. The rats were then killed at 1 or 8 weeks. Histological assessment of the femoral heads was performed with H+E and TUNEL stain to determine if the apoptotic index (proportion of apoptotic cells present per high magnification field (X 400)) alter after joint reduction in the short to medium term.

The mean apoptotic index in the non traumatized right hip was 0.044 ± 0.031 (control). After joint reduction of 1 week the mean apoptotic indices were 0.069 ± 0.023 (1 hr), 0.064 ± 0.031 (2 hr) and 0.138 ± 0.060 (4 hrs). After joint reduction of 8 weeks the mean apoptotic indices were 0.062 ± 0.028 (1 hr), 0.108 ± 0.109 (2 hrs) and 0.135 ± 0.035 (4 hrs).

Our results suggests that joint reduction within 1 hour prevents worsening of apoptotic index and that there is a population of delayed apoptosis if the joint is left dislocated for 2 hours. The apoptotic index does not recover after 8 weeks.