Evaluation of tibial bone tunnel enlargement using MRI scan cross-sectional area measurement after autologous hamstring tendon ACL replacement.

The aim of this study was to evaluate tibial bone tunnel enlargement following four-strand hamstring tendon anterior cruciate ligament (ACL) reconstruction, using a new method of magnetic resonance imaging (MRI) assessment. Correlation with clinical outcome was also examined. In a prospective study following ACL reconstruction, 24 patients underwent MRI and clinical assessment, at a mean follow-up of 6.5 months. A four-strand semitendinosus and gracilis (STG) tendon graft with the polyester Soffix (Surgicraft Ltd) fixation device was placed via an instrument guided tibial tunnel and an over-the-top femoral route. Cross-sectional area (CSA) perpendicular to the long axis of the tibial tunnel was calculated digitally at three levels, using MRI. Clinical assessment included physical examination, Lysholm subjective self-evaluation score and KT 2000 arthrometric measurement. A mean CSA tibial tunnel enlargement of 33% was found. The mean side-to-side KT-2000 arthrometric difference was 1.66 mm and the mean Lysholm score was 92. We concluded that this previously unused MRI evaluation using digital direct CSA measurements provides a highly accurate method of tunnel assessment. We found no correlation between tibial tunnel enlargement, knee stability, joint function and patient satisfaction scores in the short term.