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Meniscal Repair with Anterior Cruciate Ligament Reconstruction
Introduction
Meniscus tears are commonly encountered in the setting of anterior cruciate ligament (ACL) injury. For decades, the importance of the meniscus was not recognized. Previously the standard treatment for meniscus tears was excision. While we have improved on returning patients to high-level activities after ACL injuries, posttraumatic osteoarthritis in the decades that follow reconstruction continues to be problematic. The meniscus is becoming increasingly recognized for its role in knee stability, dissipating forces across the femorotibial joint, and protecting the articular cartilage. Meniscus repair has been demonstrated to provide satisfactory outcomes at mid-term follow-up. It is important for surgeons to recognize injuries to the meniscus during ACL reconstruction (ACLR) and address tears that warrant treatment. Meniscal preservation should be of upmost importance in both preserving knee stability and preventing degeneration of the knee at long-term follow-up.
Epidemiology of Meniscus Tears in Anterior Cruciate Ligament Injury
Tears to the medial and lateral menisci frequently occur during acute ACL disruptions. Meniscus tears may also be observed during reconstruction in chronically ACL-deficient knees. Meniscal tears have been reported to be present in 41%–82% of acute ACL injuries and 58%–100% of chronic injuries. The incidence of meniscal tears increases with time between injury and reconstruction. The laterality of meniscal injury patterns appears to differ depending on the length of time between ACL disruption and reconstruction. Cipolla et al. demonstrated differences in meniscal tear patterns between acute ACL injuries and patients with chronic ACL deficiency. In a retrospective review of 1103 ACLRs, the authors attempted to define the natural history of meniscal injury in the setting of ACL disruption. They found that 59% of acute ACL injuries had lateral meniscal tears; medial meniscal tears were half as common (29%) in acute settings. The inverse was true in chronic ACL deficiency, as Cipolla reported a 42% rate of lateral meniscus tears and 74% rate of medial meniscus tears in chronically cruciate-deficient knees.
There appears to be certain patterns of meniscal tears that occur during ACL injury. Smith and Barrett prospectively described the location of meniscal tears found at the time of ACLR. They determined the posterior horn of either meniscus was involved in 94% of tears. Further, more than 99% of medial meniscal tears involved the posterior one-third of the meniscus. They also demonstrated that more than 60% of tears involved the peripheral zone of the meniscus and/or the meniscal-capsular junction. Tears have been reported to be longitudinal in nature in greater than 70% of cases. Further more, the incidence of both medial and lateral meniscal tears has been demonstrated to increase with delays in reconstruction. Therefore the most common meniscal tears that result from ACL injury would be a peripheral longitudinal tear located posteriorly and potentially involving the posterior horn.
Meniscus—Basic Science
Blood Supply
A comprehensive understanding of the normal blood supply to the menisci is important when considering meniscus repair. The implications of blood supply are important when considering the ability of these structures to heal after injury. The menisci receive blood supply from the superior, middle, and inferior geniculate arteries. Arnoczky and Warren evaluated the meniscal capillary plexus networks using India ink arterial injection techniques in cadavers aged 53–94 years. They determined that the adult meniscus only has vascularity present in the outer 10%–30% of the medial meniscus and 10%–25% of the lateral meniscus. Further more, they also concluded that anterior and posterior horn attachments retained a greater blood supply compared with the central one-third of each meniscus in the axial plane. Additionally, there appears to be an age-dependent relationship regarding meniscal vascularity, with younger patients having vascularity penetrating further from the meniscal circumference. Petersen and Tillman demonstrated that the meniscus is completely vascularized at 1 year; they describe a decrease in vascularity in the central one-third of the meniscus in the axial plane from age 1 year to age 18 years from 100% to 33%, and a decrease from age 18 to 50 years from 33% to 25%. They also reported that anterior and posterior horns of both menisci were well vascularized (100%) regardless of age. Therefore microvascular studies suggest there is ample blood supply to heal repairs involving the anterior or posterior horns and the peripheral one-third of the meniscus. It may be more reasonable to suggest younger patients have a slightly larger portion of vascularized menisci and may benefit from meniscal repair.
Load Transmittance
The medial and lateral menisci play important roles in transmitting forces across the knee. Preservation of torn menisci by repair is important, as the menisci protect the knee’s articular cartilage. The menisci increase the congruency of the knee joint and account for differences in tibial and femoral geometric differences. The medial meniscus is responsible for 50% of the load transmission through the medial joint at full extension, and 85% at 90 degrees of flexion. The lateral meniscus transmits 70% of the load across the lateral joint in full extension, and 85% in 90 degrees of flexion. The meniscus protects the articular cartilage in both compartments. Knees without menisci carry a fourfold relative risk of osteoarthritis at long-term follow-up. Meniscus repair and preservation are of upmost importance to protect articular cartilage after ACL injuries.
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