Nonanatomic Tibial Tunnel Placement for Single-Bundle Posterior Cruciate Ligament Reconstruction Leads to Greater Posterior Tibial Translation in a Biomechanical Model

Abstract

To determine the effect of varying proximal-distal tibial tunnel placement on posterior cruciate ligament (PCL) laxity. Nine matched pairs (18 total) of cadaveric knees (mean age 79.3 years, range 60 to 89), were studied. The specimens from each pair were randomly divided into 2 groups based on tibial tunnel placement: (1) anatomic tunnel and (2) proximal nonanatomic tunnel. A 150-N cyclic posterior tibial load was applied using a Materials Testing System machine at 0°, 30°, 60°, and 90° of knee flexion. Each specimen completed 50 cycles at a rate of 0.2 Hz at each knee flexion angle. In 10 specimens, a static 250-N posterior tibial load was applied at 90° of knee flexion. Posterior tibial translation was recorded. Load to failure for all specimens was recorded. With application of a 150-N posteriorly directed cyclic force, the anatomic tunnel group had significantly less posterior tibial translation (millimeters, mean [standard deviation (SD)]) than the proximal nonanatomic tunnel group at 0°, 30°, 60°, and 90° of knee flexion: 1.1 (0.3) v 1.5 (0.4), P= .031; 1.1 (0.6) v 2.2 (0.9), P= .019; 0.9 (0.4) v 2.0 (0.6), P= .001; 0.9 (0.6) v 2.9 (0.7), P < .001, respectively. The anatomic tunnel group also demonstrated significantly less posterior tibial translation (millimeters, mean [SD]) than the nonanatomic tunnel group at 90° with a static 250-N posteriorly directed force applied (P <.05): 2.3 (1.3) v 6.1 (2.3), P= .016. Four pairs were excluded from the 250-N results because of prior load to failure testing. Anatomic tibial tunnel placement re-creating the tibial origin of the PCL results in significantly less posterior tibial translation than proximal nonanatomic tibial tunnel placement. Correct placement of the tibial tunnel during PCL reconstruction is essential for avoidance of posterior laxity. Anatomic tibial tunnel placement during PCL reconstruction may ensure a more stable reconstruction.