Structure and function of the healing medial collateral ligament in a goatmodel

In this study knee joint function with a healing medial collateral ligament (MCL) at six weeks was examined with a robotic/universal force-moment sens or testing system during the application of two loading conditions: (1) 5 N m valgus moment and (2) 67 N anterior load. Additionally the structural pro perties of the femur-MCL-tibia complex and the mechanical properties of the MCL substance were determined by uniaxial tensile tests. The histological appearance of the healing MCL was also observed. At 30 degrees and 60 degre es of knee flexion, valgus rotation of the healing knee was significantly i ncreased compared to the sham. The in situ force in the healing MCL was sig nificantly lower (34 +/- 17 N vs 54 +/- 12 N) at the same flexion angles (5 0 +/- 10 N vs 62 +/-7 N). The anterior translation of the knee had returned to normal values at 30 degrees and 60 degrees of knee flexion. However, no differences could be found between the corresponding in situ forces in the healing MCL at all flexion angles examined during application of an anteri or load. The stiffness of the healing group (52.5 +/- 19.4 N/mm) was signif icantly lower than the sham group (80.3 +/- 26.4 N/mm) (p < 0.04). The modu lus of the healing group was also significantly decreased (p < 0.05), The f indings suggest that the tensile properties of the healing goat MCL and val gus knee rotation have not returned to normal at six weeks after an isolate d MCL rupture, however, anterior translation appeared to return to sham lev els. (C) 2001 Biomedical Engineering Society.