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Popliteus Bypass and Popliteofibular Ligament Reconstructions Reduce Posterior Tibial Translations and Forces in a Posterior Cruciate Ligament Graft

Abstract
Purpose—To measure the abilities of popliteus tendon (POP) and popliteofibular ligament (PFL) graft reconstructions to limit posterior tibial translations and alter forces in a PCL graft reconstruction after posterior cruciate ligament (PCL) and lateral collateral ligament (LCL) reconstruction.

Methods—Fifteen fresh frozen cadaveric knees underwent anterior-posterior (AP) laxity testing
with 200 N of applied anterior and posterior tibial force. Forces in the native PCL were recorded
during passive extension from 120° to 0° with an applied 100-N posterior tibial force. The popliteus
tendon was released at its femoral origin, the PFL and LCL were cut, and the PCL was sectioned,
creating a combined grade 3 PCL and posterolateral corner injury. The PCL was reconstructed with
a single-bundle inlay graft tensioned to restore intact knee laxity to within 1 mm at 90°, and the LCL
was reconstructed with an anatomically placed graft. Testing was repeated with POP and PFL
posterolateral reconstructions in addition to the PCL and LCL reconstructions.

Results—PCL + LCL grafts alone matched intact knee laxities between 20° and 90° of flexion;
mean laxity was 3.5 mm greater than intact at 0° and 2.2 mm greater at 10°. The addition of a POP
reconstruction to PCL + LCL reconstructions significantly reduced AP laxities from −2.4 mm (0°
flexion) to −1.4 mm (90° flexion). Mean laxities with POP and PFL grafts were not significantly
different from the intact knee or from each other. Mean PCL graft forces with the PCL + LCL
reconstructions alone were not significantly different than those with the native PCL. Mean PCL
graft forces with POP and PFL reconstructions were not significantly different from each other; both
means were significantly less than those for the PCL + LCL reconstructions alone at flexion angles
greater than 55°.

Conclusions—After PCL and LCL reconstruction, the popliteus bypass and popliteofibular ligament reconstructions not only eliminated excessive posterior laxity and returned the knee to a normal laxity profile but also resulted in substantial decreases in PCL graft forces. Clinical Relevance—These results provide further rationale for reconstructing torn posterolateral structures with a grade 3 posterolateral injury in combination with a PCL reconstruction.
Keywords
Posterior cruciate ligament; Posterolateral corner; Biomechanics; Popliteus; Popliteofibular
ligament; Lateral collateral ligament

Authors

Sung-Jae Kim, Andri MT Lubis2*†
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