The drill-bit diameter, transverse drill angle, and knee flexion angle can all affect femoral tunnel aperture morphology in medial portal drilling during ACL reconstruction. The relationship between drilling orientation and aperture morphology is critical knowledge for surgeons performing ACL reconstruction.

This study identified kinematic changes over time in both the ACL-injured and contralateral ACL-intact knees after ACL reconstruction. These kinematic adaptations could have important implications for postoperative care, including evaluating the optimal timing of return to sports and the development of bilateral neuromuscular rehabilitation programs that may improve patient outcomes and reduce reinjuries in both the short and long terms.

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These results may aid surgical planning, specifically for choosing a graft size and fixation angle that most closely matches the native anatomy and function across the entire range of knee motion.

Purpose To determine in vivo dynamic graft bending angle (GBA) in anterior cruciate ligament (ACL) reconstructed knees, correlate the angle to tunnel positions and tunnel widening, and evaluate the effects of two femoral tunnel drilling techniques on GBA. Methods Patients with an isolated ACL injury undergoing reconstruction were included from 2011 to 2012. Trans-portal techniques were used to create femoral tunnels. Tunnel locations were determined using 3D-CT. Tibio-femoral kinematics during treadmill walking and running were assessed using dynamic stereo X-ray analysis 6 months and 2 years postoperatively. The GBA was calculated from the 3D angle between the graft and femoral tunnel vectors at each motion frame. Cross-sectional area of femoral tunnels were measured at 6 months and compared to initial size to assess tunnel widening. Results A total of 54 patients were included. Use of flexible drills resulted in significantly higher GBA during walking (80.6° ± 7.8°; p<0.001) and running (80.5° ± 9.0°; p=0.025) than rigid drills (walking: 67.5° ± 9.3°, running: 74.1° ± 9.6°). It led to greater tunnel widening of 113.9±17.6 %, compared with rigid drills of 97.7±17.5 % (p=0.003). Femoral and tibial apertures were located in similar anatomic positions in both groups, but femoral tunnel exits were located more anteriorly (p<0.001) in the flexible drill group. Higher GBA was highly correlated with anterior location of femoral exits (r=0.63, p<0.001) and moderately correlated with greater tunnel widening (r=0.48, p<0.001). Conclusions High GBA was identified during dynamic activities after anatomic ACL reconstruction using a trans-portal femoral tunnel drilling technique. The GBA was greater when flexible drills were used. The high bending angle resulted from more anterior location of femoral tunnel exits, and correlated with early bone tunnel widening at 6 months. These results suggest that high GBA may increase stress on the bone-graft interface and contribute to greater tunnel widening after anatomic ACL reconstruction, although clinical impact should be further investigated. Level of Evidence Level III, retrospective comparative study