Neuromuscular function after anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft.

BACKGROUND: The quadrupled autologous semitendinosus-gracilis graft is the first choice of many orthopaedic surgeons when reconstructing the anterior cruciate ligament. The effect that this procedure has on voluntary muscle control remains unclear. The purpose of this study was to evaluate the effect that anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft has on voluntary muscle control by assessing subjects' specificity of muscle action. METHODS: The voluntary muscle control of 10 people (seven males, three females) with acute, isolated ACL ruptures was assessed in the days prior to when they underwent anterior cruciate ligament reconstruction with quadrupled autologous semitendinosus-gracilis grafts and after they had returned to play in sports requiring quick changes of direction and jumping (approximately 6 months later). The experimental protocol included the use of an established target-matching protocol that requires subjects to produce and modulate force with fine control, electromyographic recordings from 11 muscles about the knee, and the use of circular statistics to calculate specificity indices that describe the degree of focus (specificity) associated with the activity pattern of each muscle. Data were analyzed by performing pre-surgery and post-return to sports side-to-side comparisons, as well as, pre-surgery to post-surgery ipsilateral comparisons. RESULTS: Diminished specificity of muscle action was observed in the activity patterns of most of the muscles of the subjects' anterior cruciate ligament deficient knees prior to surgery. The quadriceps muscles were particularly affected. Post-return to sports results indicated that voluntary muscle control had improved in most muscles. There was no significant difference in pre-surgery and post-return to sports semitendinosus and gracilis muscle control. The semimembranosus muscle displayed less specific muscle activity patterns following surgery, which may represent a compensation strategy for minor changes in neuromuscular function. CONCLUSIONS: Voluntary muscle control improved in most muscles following ACL reconstruction with semitendinosus-gracilis autografts. Semitendinosus and gracilis muscle control did not appear to be altered significantly by the procedure.