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 s tability is associated with an improved tibiofemoral relationship. We used stress radiographs to determine not only stability but also the tibiofemora l relationship in 15 patients who had a clinically successful anterior cruc iate ligament reconstruction. Their results were compared with those of 14 volunteers with normal knees. The average Lysholm score for the patients wa s 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 ve rsus 5.0 +/- 3.3 mm). However, with a posteriorly directed stress the tibia in the reconstructed knees did not translate posteriorly to the same exten t 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 cruci ate ligament reconstruction may result in reduced anteroposterior tibial tr anslation, accomplished, in part, through restraining posterior translation , leaving the tibia with persistent subluxation. Fibrosis and contracture o f the posterior structures may explain this phenomenon.