Kinematic analysis of the posterior cruciate ligament, part 2: a comparison of anatomic single- versus double-bundle reconstruction.

BACKGROUND A more thorough understanding of the posterior cruciate ligament (PCL) has led to an increase in awareness and treatment of complex PCL injuries. Controversy exists about whether PCL reconstruction (PCLR) using an anatomic single-bundle (aSB) or anatomic double-bundle (aDB) technique is the most effective. HYPOTHESIS An aDB PCLR provides significantly better anterior-posterior and rotatory knee stability compared with an aSB PCLR and more closely recreates normal knee kinematics. STUDY DESIGN Controlled laboratory study. METHODS A total of 18 match-paired, cadaveric knees (mean age, 54.8 years; range, 51-59 years; 5 male and 4 female pairs) were used to evaluate the kinematics of an intact PCL, an aSB and aDB PCLR, and a complete sectioned PCL. A 6 degrees of freedom robotic system was used to assess knee stability with a 134-N applied posterior tibial load, 5-N·m external and internal rotation torques, 10-N·m valgus and varus rotation torques, and a coupled 100-N posterior tibial load and 5-N·m external rotation torque at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120°. RESULTS The aDB PCLR had significantly less posterior translation than the aSB PCLR at all flexion angles of 15° and greater. The largest difference in posterior translation was seen at 105° of flexion, where the aSB PCLR had 5.3 mm (P = .017) more posterior translation than the aDB PCLR. The aDB PCLR also had significantly less internal rotation than the aSB PCLR at all tested angles of 90° and greater. Neither reconstruction was able to fully restore native knee kinematics. CONCLUSION An aDB PCLR more closely approximated native knee kinematics when compared with an aSB PCLR. Specifically, the aDB PCLR demonstrated significantly more restraint to posterior translation at flexion angles between 15° and 120° and less internal rotational laxity at high flexion angles 90° to 120°. CLINICAL RELEVANCE Comparison of the 2 reconstruction techniques illustrates the time-zero kinematic advantage imparted by the addition of the posteromedial bundle reconstruction. The benefit is most pertinent for resistance to posterior translation across a full range of flexion and rotational stability beyond 90° of knee flexion.