34th Annual Scientific Meeting proceedings

Introduction
Meniscus injuries are highly prevalent in humans. The exact prevalence is difficult to ascertain due to the heterogeneous nature of the affected population. These injuries range from entirely asymptomatic degenerative tears incidentally identified during an MRI scan for other knee pathologies, to acute traumatic injuries that may involve not only a meniscal tear but also concomitant lesions, such as an anterior cruciate ligament (ACL) rupture. Broadly speaking, meniscal injuries can be categorized into two major groups: a degenerative group of meniscal tears, which often remain undetected for extended periods before causing sudden or slowly progressive pain, and traumatic meniscal injuries. The latter group is often of greater interest to surgeons for treatment.

The Meniscus
First, a brief overview of the meniscus's function and structure. The meniscus functions not only as a shock absorber between the femur and tibia but also enhances joint congruity and acts as a secondary knee stabilizer. Consequently, it is a crucial structure within the knee. It is important to note that the healing of meniscal tears following surgical repair (discussed in more detail later) is dependent on its healing capacity, specifically its vascularity. The meniscus is thus divided into three zones: white/white, red/white, and red/red zones, referencing their degree of vascularity, which indicates their healing potential. In other words, a tear in the white/white zone is unlikely to heal, even with a technically perfect repair. The general objective of meniscal injury treatment is to maximize the preservation of meniscal function; in essence, "save the meniscus." Unfortunately, this is not always feasible. Meniscectomy is considered, firstly, for the degenerative group and, lastly, for the acute trauma group. Subsequently, various meniscal repair techniques are reviewed.

Partial Meniscectomy
Historically, partial meniscectomy has been the most frequently performed orthopedic procedure. It is an arthroscopic procedure where the tear, located in the non-healing zone, is resected. The frequent performance of this procedure was often due to overdiagnosis and subsequent overtreatment of meniscal lesions as the cause of knee pain in the degenerative knee. We now understand that the degeneration itself (osteo arthrosis) is the cause of pain, not solely the meniscal tear. In other words, removing the meniscal tear in these patients will rarely improve symptoms. Sufficient evidence now supports this. Therefore, the primary treatment for a degenerative meniscal tear is maximally conservative, involving a combination of physical therapy, offloading, and possibly infiltration. The sole indication for surgical intervention in the form of partial meniscectomy for both degenerative and traumatic meniscal tears is mechanical impingement. This mechanical conflict is often well-described by the patient as knee locking due to a displaced fragment. This is frequently accompanied by knee joint effusion. These are unstable lesions and respond poorly to non-operative treatment.

In cases of traumatic meniscal tears, the principle of “save the meniscus” is maintained, leading to initial non-operative management, or consideration of meniscal repair to preserve maximal meniscal function. Meniscectomy in young, active, and athletic populations is maximally avoided due to the risk of premature gonarthrosis, with a relative risk of 3.47 in professional and non-professional soccer players (n = 1039). In this context, the role of meniscectomy has been definitively proven in Dr. Steven Claes’ study, which compared isolated ACL reconstruction with combined ACL reconstruction and meniscectomy, showing that after 10 years, the risk of gonarthrosis in the combined injury group was 50% versus 16% in the isolated group.

Meniscus Repair
When proceeding with meniscal repair, two significant limitations are considered. As previously mentioned, on one hand, the limited healing capacity due to restricted vascularity is associated with a higher risk of failure. On the other hand, the rehabilitation protocol after repair is slower and more gradual for the patient, aiming to maximize healing. Additionally, there is a difference in healing between lateral and medial meniscal tears. Lateral meniscal repair fails in just over 10% of cases, compared to nearly 30% for medial meniscal repair. This difference is thought to be related to better vascularity of the lateral meniscus. In recent decades, there has been a trend to accelerate rehabilitation protocols, even after complex repairs. In most cases, early active mobilization of the knee up to a maximum of 90° flexion and weight-bearing as tolerated is often allowed. The goal is a return to sport at 4 months post-operatively in case of isolated meniscal repair. Exceptions to this are precarious meniscal repairs such as bucket-handle tears and root refixations. In these cases, a non-weight-bearing period of 6 weeks is often prescribed. The technique used for meniscal repair depends on the type of tear. Tears in the posterior horn, whether lateral or medial, located in the red/white or red/red zones, are typically repaired with an All-inside device, where a suture with a knot is passed twice behind the meniscal capsule, allowing these knots to be tightened to approximate the tear. A second type of tear is a root tear, where the meniscal root detaches from its insertion. This completely compromises its function, analogous to springs detaching from a trampoline. Refixation of this root involves reattaching the root into a tunnel. This tunnel is positioned with a guide precisely at the desired reattachment site. Fixation of the sutures occurs anteriorly on the tibia with a button or a screw. These repairs are notoriously difficult to heal and often occur in an already degenerative knee, rarely having a traumatic origin. It is important to consider the patient's overall alignment. If a medial meniscal root tear is repaired in a knee with a concomitant pronounced varus alignment (leading to secondary medial overload), the chance of healing will be very low. Lastly, RAMP lesions, named after the typical skateramp shape that can be visualized when intact during arthroscopy. These types of tears occur in combination with ACL ruptures and have only been recognized as a distinct entity for just over a decade. Recall the secondary stabilizing function of the meniscus, which is critically important in this context. It has now been proven that if these tears are ignored and not fixed, the risk of recurrent ACL rupture after ACL reconstruction and a RAMP lesion increases by a factor of 8. Repair is performed with a non-absorbable suture via an extra posteromedial portal.

Take-Home Messages
Currently, there is a much more conservative approach to the management of meniscal injuries compared to the past. The general principle dictates a maximally sparing approach due to the vital function of the menisci in the knee. Only a locked knee or recurrent effusion are strict indications for surgical intervention in isolated degenerative meniscal tears. In case of traumatic meniscal tears, if the tear can be repaired and healing capacity allows, this is naturally preferred over meniscectomy. The type of repair then depends on the specific tear pattern. Unfortunately, such repairs sporadically fail; therefore, a strict rehabilitation protocol is adhered to after meniscal repairs to optimally safeguard long-term outcomes.