The healing effects on the biomechanical properties of joint capsular tissue treated with Ho : YAG laser: An in vivo rabbit study

Purpose: The objective of this study was to evaluate the healing response, after thermal treatment with a Ho:YAG laser, on the biomechanical propertie s of capsular soft tissue. Type of Study: Before and after trial. Methods: Forty-five New Zealand white rabbits were used in this study. A medial peri patellar retinacular thermal capsuloplasty using a Ho:YAG laser and a later al peripatellar retinacular release was performed on 1 knee of each rabbit. The contralateral knee served as a control and had a lateral release of th e retinaculum only. The temperature of the medial retinaculum was maintaine d at 55 degreesC +/- 5 degreesC during treatment. The medial peripatellar r etinaculum was evaluated at 0, 6, and 12 weeks postoperatively. Tensile tes ting of the medial retinaculum and a biomechanical assessment evaluating th e structural and material properties were performed. Results: The ultimate load (force) of the medial retinaculum was 70%, 56%, and 84% of control at 0, 6, and 12 weeks, respectively, after the procedure. The stiffness (force /deformation) of the medial retinaculum was 83% of control at 0 weeks, 54% at 6 weeks, and 85% at 12 weeks. The ultimate stress (force/area) of the me dial retinaculum also showed a significant reduction at 0 and 6 weeks posto peratively, 63% and 62% of control, respectively. By 12 weeks, the ultimate stress was 83% of control. Conclusions: Thermal treatment of the medial re tinaculum with a Ho:YAG laser results in soft tissue with significantly dim inished biomechanical properties after treatment. The results of this study suggest that a 12-week period of minimal stress on the capsular tissues sh ould follow a thermal capsuloplasty procedure.