Hamstring anterior cruciate ligament reconstruction: a comparison of bioabsorbable interference screw and endobutton-post fixation.

PURPOSE: The purpose of this study was to evaluate hamstring anterior cruciate ligament (ACL) reconstruction using aperture fixation with bioabsorbable interference screw (BIS) and distant fixation using EndoButton (Smith & Nephew, Andover, MA) and screw-post (ENDO). TYPE OF STUDY: Prospective nonrandomized clinical outcome study.
METHODS: Two groups of 15 patients who underwent autogenous hamstring ACL reconstruction with a minimum of 2 years' follow-up evaluation (mean 35 months) were included in the study. The BIS group underwent poly-L-lactic acid interference screw fixation at both femoral and tibial tunnels and the ENDO group underwent EndoButton fixation on the femoral side and screw-post fixation on the tibial side. Clinical evaluation included International Knee Documentation Committee (IKDC) and arthrometer measurements. Tunnel enlargement, screw integrity, graft integrity, and graft-tunnel interface were evaluated using radiographs and magnetic resonance imaging. Statistical analyses were performed using the Student t test, with significance set at 0.05.
RESULTS: All patients in both groups had functionally normal or near-normal IKDC scores. The average IKDC subjective knee form scores were 85 +/- 11 versus 81 +/- 17 (BIS v ENDO) and side-to-side KT differences were 3.2 +/- 2.6 mm versus 2.4 +/- 1.8 mm (P >.05). For both groups, tunnel enlargement was present on radiographs at both femoral and tibial sides (36% to 77%). Tunnel enlargement was more significant at the femoral tunnels (53% to 77%) than the tibial tunnels (36% to 42%). In the BIS group, magnetic resonance imaging revealed 9 partially degraded screws and 2 intact screws on the femoral side. On the tibial side, 4 partially degraded and 10 intact screws were seen. For both groups, the grafts have partial or complete incorporation at all tunnels. Tunnel enlargement measured on radiographs correlate well with measurements on magnetic resonance images.
CONCLUSIONS: Our results showed that rigid aperture fixation using BIS did not lead to significant differences in clinical outcome when compared with distant fixation using ENDO at 24 to 40 months follow-up evaluation. Significant tunnel enlargement was present in both groups, more pronounced on the femoral side. Magnetic resonance imaging findings showed that BIS were not degraded even at 2 to 4 years after surgery. LEVEL OF EVIDENCE: Level II.