Comparison of tunnel expansion, isometric muscle strength and clinical condition after anterior cruciate ligament reconstruction with single- or dual-bundle: Randomized, prospective 8 years follow up study

Thirty-one patients who suffered anterior cruciate ligament (ACL) injury and underwent ACL reconstruction (16 single-bundle, 15 double-bundle) with ENDOBUTTON between November 2007 and March 2008 were included in the study. Isokinetic and concentric strength measurements of the quadriceps and hamstring muscles at the 6th month and 8th year were made using a Biodex 3 device at angular velocities of 60°/sec, 120°/sec and 180°/sec. The peak torque and peak torque to body weight ratios were recorded. 3D-CT scans of the joints were performed on the 2nd, 3 rd and 6th month and 8th year. CT slices were divided into six equal parts marking the distance between the femoral and tibial tunnels with the most distant part of the knee joint as L1, and with the entry point on the knee joint as L6. The tunnel length was measured in millimeters and perpendicularly to the tibial axis in the sagittal and coronal planes. Tunnel cross-sectional areas were also measured in mm2 using the same device on axial reconstructions. Clinical evaluations on the 8th year were performed with the IKDC, Tegner and Lysholm knee scoring systems and laxity in the patients was evaluated with the anterior drawer test. Posterolateral tunnel widening was analyzed with the repeated measures ANOVA technique whereas two-way mixed ANOVA was employed in evaluating the anteromedial tunnel widening. Three-way ANOVA was used in assessing the Biodex results and comparison of the scoring systems results were done with the t-test. RESULTS: No difference was found between the groups in terms of IKDC, Lysholm and Tegner scores and anterior drawer test results at the 8th year follow-up (p>0.05). Points where significant amounts of tunnel widening were observed are shown in Table 1. On evaluation of the anteromedial bundles alone, it was observed that double-tunnel reconstruction led to greater widening. No significant difference was found between the groups in terms of muscle strength in the 8th year assessments, however, there was a statistically significant difference between the preoperative and 6th month results (p<0.05). Patients in both groups had better results at the 8th year follow-up when compared to their preoperative and 6th month results. The results of our study confirmed significant amounts of widening at parts of the femoral tunnel close to the knee joint in patients treated with single-bundle or double-bundle ACL reconstruction. However, there is no difference between the groups in terms of clinical results and isometric muscle strengths in the long term. DISCUSSION: It has been suggested that the tunnel widening will lead to failure of the reconstruction. It is hypothesized that, in double-bundle reconstruction, the tunnels will widen more and finally coalesce, which in turn, will result in failure of the reconstruction. In our study, we found no evidence pointing out to a coalescence of the tunnels in the long term. We believe the greater widening in the anteromedial bundle in the double-tunnel surgery vs. the single-tunnel method is due to the smaller diameter of the graft and its greater mobility