Summary

Lateral meniscus centralization can improve the knee stability of ACL reconstructed knee accompanied with lateral meniscus dysfunction due to irreparable meniscus defect.

Abstract

Lateral meniscus (LM) disorders are one of the factors which cause residual rotational instability after anterior cruciate ligament reconstruction (ACLR) (Musahl V, AJSM 2010). There are several types of irreparable meniscus disorders, one of which is a massive meniscal defect. Recently, a LM function restoring technique called “arthroscopic centralization” was reported (Koga H, Arthroscopy 2016). This method can be applied to a meniscus that is irreparable by conventional methods, and can prevent the osteoarthritis in a rat medial meniscus defect model (Ozeki N, J Orthop Sci 2017). The purpose of this study was to investigate whether LM centralization contributes to ACLR knee rotational stability in human knee. The hypothesis of this study is that LM centralization would improve the stability of ACL reconstructed knees including pivot shift phenomenon.
Ten fresh-frozen human cadaveric knees were tested using a robotic system under two loads: (1) an 89-N anterior tibial (AT) load and (2) a simulated pivot-shift load under combined 7-Nm valgus and 5-Nm internal rotation torque. Anatomic ACL reconstruction was performed with an 8-mm-diameter hamstring graft which was fixed at 40 N at 30° of flexion. The LM states were (a) intact, (b) massive middle segment meniscus defect (def LM) and (c) centralized LM. The massive LM defect was defined as 20% of LM anteroposterior length and created arthroscopically via accessory lateral portal. Arthroscopic centralizations were performed as previously reported by utilizing two 1.4-mm anchors with a #2 suture (Koga H, Arthroscopy 2016). The knee states tested were (1) intact ACL/ intact LM, (2) reconstructed ACL/ intact LM, (3) reconstructed ACL/ def LM, and (4) reconstructed ACL/ centralized LM. The data were statistically evaluated by one-way ANOVA with the level of significance set at p < 0.05.
Under AT loading, anterior tibial translation (ATT) increased significantly after ACLR + LM defect compared to ACLR + intact meniscus, and decreased significantly after ACLR + centralized LM compared to ACLR + LM defect at both 15° and 30° of knee flexion. Under simulated pivot-shift loading, coupled ATT increased significantly with ACLR + LM defect compared to ACLR + intact meniscus and decreased significantly with ACLR + centralized LM compared to ACLR + intact meniscus and ACLR + LM defect (p<0.05) at FE, 15° and 30° of knee flexion.
In conclusion, the LM centralization can improve ATT and residual pivot shift phenomenon of ACL reconstructed knee accompanied with lateral meniscus dysfunction due to massive meniscus defect. In cases involving irreparable LM injury during ACL reconstruction, it should be considered to apply arthroscopic centralization for avoiding residual rotational instability.