Functional analysis of untreated and reconstucted posterior cruciate ligament injuries

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Abstract
Twenty patients with old ruptures of the PCL were analyzed. Ten patients were untreated, and ten patients had reconstruction of the PCL with the medial head of the gastrocnemius. The patients' gait was analyzed using high speed photography, footswitches, electro myography, and force plate. Patients were studied while walking, running, and stair-climbing. A Cybex muscle strength evaluation was also performed. Clini cally, all patients had moderate to severe posterior instability. Five of the 20 patients also had posterolat eral instability. Cybex testing showed quadriceps defi cits in both reconstructed and untreated groups when comparing involved and uninvolved limbs. The recon structed group also had deficits on hamstring Cybex testing. Footswitch data showed only minimal abnor malities. Gait velocity of walking was 91% of normal with a normal cadence. There was no significant differ ence in the single limb support times between the involved and uninvolved limbs in walking, fast walking, or running. The photometric data showed a tendency for increased knee flexion during the midstance phase of the gait cycle in comparing involved and uninvolved limbs. The knee flexion angles during midstance were similar in the patients with posterior instability when compared to the patients with the additional postero lateral instability. Force plate data showed decreased foot-floor reaction in the untreated group during termi nal stance while walking. Similar findings were found in the reconstructed group during running. Electromyo graphic analysis showed early activation of the gastroc nemius-soleus complex during the stance phase of the gait cycle. This was postulated as a compensation mechanism to stabilize the foot-ankle-tibia complex in the face of quadriceps weakness and posterior insta bility.

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