Biomechanical Roles of the Popliteomeniscal Fascicles and Meniscofibular and Meniscotibial Ligaments in Stabilizing the Lateral Meniscus Posterior Horn: A Cadaveric Study.

BACKGROUND

The posterolateral corner (PLC) structures restraining the mobility of the lateral meniscus posterior horn (LMPH) have been described in greater anatomic detail in recent years. However, biomechanical evidence regarding their functional role remains limited.

HYPOTHESIS/PURPOSE: The purpose was to investigate the biomechanical roles of the popliteomeniscal fascicles (PMFs), meniscofibular ligament (MFibL), lateral meniscotibial ligament (LMTL), and posterior meniscotibial ligament (PMTL) in stabilizing the LMPH. It was hypothesized that transecting the PMFs would increase mobility regardless of cutting order, that additional PLC transection would further increase instability, and that these injuries would alter knee kinematics.

STUDY

DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric knees were mounted on a 6 degrees of freedom robotic testing system. Sequential transections of the anterior PMF (aPMF), posterior PMF (pPMF), MFibL, LMTL, and PMTL were performed under 2 dissection protocols to compare the effect of cutting order between the aPMF and pPMF. LMPH anterior displacement under 10-N traction, tibial rotation during passive flexion-extension, and rotational laxity under ±5 N·m torque were measured. Differences among transection states were analyzed using linear mixed models with Bonferroni correction, with significance set at P < .05.

RESULTS

LMPH anterior displacement significantly increased from 6.3 mm in the intact state to 8.1 to 8.4 mm after transection of either the aPMF or pPMF (P = .007) and further increased to 10.2 mm after MFibL (P < .001) and 11.4 mm after PMTL (P < .001) transection. Passive flexion significantly shifted tibial rotation toward external rotation after aPMF or pPMF transections (P = .043). Internal rotation laxity increased from 32.6° in the intact state to 36.4° after combined PMF cuts (P = .001), 37.3° after MFibL transection (P < .001), and 40.2° after PMTL transection (P < .001), whereas the external rotation laxity did not significantly change.

CONCLUSION

Anterior movement of the LMPH occurred after transection of either the aPMF or pPMF, regardless of cutting order in the cadaveric model. Concomitant injury to other posterolateral structures, particularly the MFibL and PMTL, further increased this instability.

CLINICAL RELEVANCE: PLC structures restraining the LMPH may be important for detecting abnormal meniscal motion. Assessing not only the PMFs but also the MFibL and PMTL may improve diagnostic accuracy and treatment planning.