Aim: To determine if a side-to-side difference in laxity occurs with anterior cruciate ligament (ACL) reconstruction utilizing a hamstring tendon and standard RCI (Smith and Nephew) interference screw fixation, and if this can be affected by the use of a reverse thread RCI screw in right-sided knees.

Methods: This was a prospective study of 80 patients undergoing right-sided ACL reconstruction with hamstring tendon autograft. Females were excluded in case of there being a sex difference in postoperative laxity with HT graft. The study group comprised of 36 males utilising standard RCI screws (STD) and 44 males utilising reverse-thread RCI screws (REV). The same technique was used on all patients and all procedures were carried out by the same surgeon. The patients were evaluated at six and 12 months following the surgery with KT1000, IKDC assessment, and Lysholm Knee Score.

Results: At the follow-up after 12 months, the average side-to-side differences using KT1000 testing were 2.0 mm (STD) and 1.0 mm (REV) using manual maximum, and 1.7 (STD) and 1.0 (REV) using KT20. Both results were statistically significant. In addition, 33% of the STD group had a manual maximum of ≥3mm compared with 11% of the REV group (p< 0.01). Accordingly, there was a higher incidence of grade I instability (Lachman) in the STD group (23% of STD group; 8% of REV group, p=0.04).

Conclusion: The use of a reverse-thread interference (RCI) screw for femoral fixation in right-sided hamstring tendon ACL reconstructions in males significantly decreased side-to-side laxity at the 12 month review when compared with standard RCI fixation.