Recovery of Chondrocyte Metabolic Activity after Thermal Exposure

Abstract

Background The relationship between temperature elevation and thermal exposure time during thermal chondroplasty has implications for cell viability and subsequent articular cartilage function. Purpose To characterize cartilage metabolic changes after exposure to thermal stress and to determine whether changes seen acutely are reversible. Study Design Controlled laboratory study. Methods Human cartilage was exposed to a 45°, 50°, or 55°C bath for up to 3 minutes. Untreated control specimens were analyzed with each group. Viability and metabolic capability of treated and untreated specimens were evaluated immediately or 1 week after thermal stress by using methylthiotetrazole conversion, 3H-serine incorporation into protein, and 35S-sulfate incorporation into newly synthesized proteoglycan. Results Nonarthritic and arthritic articular cartilage metabolic activity declined with increasing thermal exposure. Articular cartilage displayed a recovery from thermal stress after exposure to the 50°C but not the 55°C bath. Arthritic cartilage displayed increased sensitivity with higher temperatures. Conclusions Understanding of the increased sensitivity to thermal stress of arthritic articular cartilage may be helpful in thermally based treatments. Clinical Relevance Further correlation with the temperatures attained during thermal chondroplasty will be necessary to confirm the clinical relevance of these in vitro observations to the use of radiofrequency energy devices to treat partial-thickness chondral lesions.