High incidence of tunnel widening after anterior cruciate ligament reconstruction with transtibial femoral tunnel placement

This study evaluated the incidence, amount, morphology and clinical significance of bone tunnel widening (TW) at a mean 5-year period after anterior cruciate ligament reconstruction (ACLR) with a transtibial drilling technique. Fifty-nine patients undergoing primary ACLR using quadrupled hamstring autografts, biodegradable transfemoral pins for femoral-sided and 2-mm oversized interference screws for tibial-sided graft fixation were followed up at a mean 61 months postoperatively. Patients were examined clinically and by MRI. Tunnel cross-sectional areas (CSA) were related to drill diameters, which were significantly correlated with radiographic tunnel sizes. Tunnel morphologies were assessed and their positions determined using an anatomical coordinate system. CSA had more than doubled in all segments measured (p < 0.0001) except at the femoral notch level. Greatest CSA increases were found at the femoral graft suspension point (122 %) and at the central tibial tunnel segment (134 %). 54 (92) and 56 (95 %) patients had significant TW, i.e., CSA increase of more than 50 %, in at least one tunnel segment femorally and tibially. Four different tunnel morphologies were observed, of which the linear type was most often encountered on either side. Mean side-to-side difference in anterior-posterior laxity was 1.0 +/- A 1.4 mm, while Lysholm, IKDC and Tegner acitivity scores were 90 +/- A 12, 84 +/- A 15 and 4 (1-9); clinical outcomes were not found to be correlated with tunnel sizes and morphologies as were tunnel positions and tunnel sizes. This study demonstrates that considerable TW occurs in virtually all patients in the mid term after ACLR using a transtibial drilling technique with 'high' femoral tunnel positions. Yet, neither amount nor morphology or tunnel position does affect knee stability or function.