Effect of postoperative diet on condylar cartilage response to discectomy

Purpose: Recent studies have shown that metabolic and structural changes occur in the condylar cartilage after surgical removal of the articular disc. There is some evidence that these structural changes are less pronounced in animals provisioned with a soft diet after disc removal. This study was initiated to assess whether a soft diet after discectomy in growing rats also results in alterations in the composition or metabolic activity of the matrix of the condylar cartilage. Materials and Methods: In two identical experiments, 28 thirty-day-old female Sprague-Dawley rats underwent unilateral surgical removal of the articular disc (discectomy) and were then provisioned with either a soft, mushy diet or a diet of normal rat pellets. When they were killed 3 weeks later, the condylar cartilages were removed, weighed, pulse-labeled in organ culture with [³⁵S]-sulfate for 2 hours, and analyzed for sulfated glycosaminoglycan (GAG) content and [³⁵S]-sulfate uptake. Results: As in previous studies, tissue weights and hydration were increased, and sulfated GAG content and [³⁵S]-sulfate uptake decreased on the surgery side in animals fed a hard diet. Overall, fewer differences were present in the animals fed a soft diet, although tissue weights and hydration were still elevated on the discectomized side. Analysis of ratios of surgery/nonsurgery values in the hard diet versus the soft diet sample indicated that dietary consistency was a significant factor for tissue weights and [³⁵S]-sulfate uptake, but not for hydration or sulfated GAG content. Conclusions: These data suggest that discectomy exerts a more pronounced effect on growing animals fed a hard diet, although some changes also persist after discectomy in animals fed a soft diet.