A flat posterior cruciate ligament reconstruction restores native knee kinematics, comparable to adouble-bundle reconstruction-A biomechanical robotic investigation. [biomechanics; posterior cruciate ligament, PCL; reconstruction; rectangular]

Deichsel A, Gellhaus F, Peez C, Raschke MJ, Martinovic M, Herbst E, Herbort M, Fink C, Kittl C

Abstract

Purpose: To biomechanically evaluate a flat posterior cruciate ligament(PCL) reconstruction utilizing rectangular femoral bone tunnels. Methods: Eight fresh‐frozen human knee specimens were tested in a six‐degrees‐of‐freedom robotic test setup. In each testing step, a force‐controlled test protocol was performed, including 89 N posterior tibialtranslation (PTT) in neutral, internal and external rotation, from 0 to 90° offlexion. After determining the native knee kinematics, the PCL was cut.Subsequently, a flat PCL reconstruction (PCLR) with a rectangular bonetunnel was performed, utilizing a quadriceps tendon autograft with a patellarbone block. After filling the bone tunnel, a single‐bundle PCLR without andwith femoral interference screw fixation, as well as a double‐bundlereconstruction, was performed. Statistical analysis was performed usingmixed linear models.Results: Cutting of the PCL led to significant (p ≤ .05) increases in PTT,from 0 to 90° of flexion, up to 10.7 mm, in comparison to the native state.After flat reconstruction and double‐bundle reconstruction, no significantdifference was found between the native and reconstructed state (p ≥ .05).The single‐bundle PCLR without interference screw showed significantlyincreased PTT in comparison to the native state in 30° (mean difference[MD] 3.3 mm; 95% confidence interval [CI] 1.3 – 5.2 mm; p < .001), 60° (MD4.4 mm; 95% CI 2.5–6.4 mm; p < .001) and 90° of flexion (MD 4.0 mm; 95%CI 2.1–6.0 mm; p < .001). The single‐bundle PCLR with additional interfer-ence screw showed significantly increased PTT in comparison to the nativestate only in 30° (MD 1.9 mm; 95% CI 0.05–3.8 mm; p = .01) Conclusion: Both a flat and a double‐bundle PCLR were able to restore thenative knee kinematics in all tested flexion angles. A single‐bundlereconstruction was not able to fully restore native kinematics, with onlysmall residual anteroposterior instability.