The influence of tibial fixation on tunnel enlargement after hamstring tendon anterior cruciate ligament reconstruction.

The retrospective study was designed to evaluate tibial-tunnel enlargement after anterior cruciate ligament reconstruction with hamstring autograft. Forty-three patients (43 knees) were enrolled, among whom a spiked washer was used for the tibial side fixation in 20 knees (Group SW) and the WasherLoc was used in 23 knees (Group WL). After an average 16 (range 12-32) months' follow-up, the distance between the sclerotic margins of the tibial tunnel was measured at the joint level, and 1 and 2 cm distal to the joint level on the lateral view radiographs, from which the tibial-tunnel enlargement at each point (E1, E2, and E3 respectively) was determined. Anterior knee laxity was also measured using a KT-1000 or KT-2000 arthrometer at follow-up. E1, E2, and E3 were 2.3+/-1.3 mm (mean+/-standard deviation), 1.8+/-0.8 mm, and 1.5+/-0.8 mm respectively in Group SW, and 2.6+/-1.0 mm, 2.6+/-1.2 mm, and 2.9+/-1.6 mm in Group WL. Group WL had a larger mean value than Group SW at each level of measurement, with a statistically significant difference in E2 and E3. Fifty percent of the tunnels were the cone type in Group SW, whereas reversed cone-type tunnels were the most common (39%) in Group WL. The side-to-side difference in anterior knee laxity was -0.6+/-5.2 mm in Group SW and 1.8+/-9.0 mm in Group WL, which was significantly different between the groups. No statistical relationship was found between tunnel enlargement and side-to-side difference in anterior knee laxity in Group SW, whereas there was a slight negative correlation between E1 or E2 and anterior knee laxity in Group WL. It is possible that there is greater tension applied to the graft when the WasherLoc is used, which creates larger compressive forces on the posterior wall of the tibial tunnel by the graft. This was probably the reason for the greater tunnel enlargement and the high incidence of the reversed cone-type tunnel in Group WL.