Fixed tibial subluxation after successful anterior cruciate ligament reconstruction.

Anterior cruciate ligament reconstruction results in improved function and stability in many patients. However, it is not known whether the improved stability is associated with an improved tibiofemoral relationship. We used stress radiographs to determine not only stability but also the tibiofemoral relationship in 15 patients who had a clinically successful anterior cruciate ligament reconstruction. Their results were compared with those of 14 volunteers with normal knees. The average Lysholm score for the patients was 94. None of the patients had more than 3 mm of side-to-side difference on KT-1000 arthrometer testing. Maximal anteroposterior tibial translation as measured by stress radiography was slightly increased in the reconstructed knees but was not statistically significantly different (6.6 +/- 3.2 mm versus 5.0 +/- 3.3 mm). However, with a posteriorly directed stress the tibia in the reconstructed knees did not translate posteriorly to the same extent as did the control knees, resulting in a significant difference in tibial position (-1.2 +/- 3.0 mm versus -4.0 +/- 3.3 mm). Surgical anterior cruciate ligament reconstruction may result in reduced anteroposterior tibial translation, accomplished, in part, through restraining posterior translation, leaving the tibia with persistent subluxation. Fibrosis and contracture of the posterior structures may explain this phenomenon.