Meniscal Radial Tears

Introduction

Approximately 40% to 70% of the load transmitted through the knee is done by the menisci. The mechanical load absorption ability of the menisci is to convert axial load into circumferential hoop stress. The menisci also play a major role in maintaining knee stability. The integrity of the meniscal belt is thus fundamental to preserve correct knee kinematics and avoid degenerative changes of the joint.

Meniscal tears are common in young athletes. Meniscectomy can cause mid- to long-term morbidities, including the early onset of osteoarthritis. Radial tears disrupt the circumferential fibres of the meniscus, which are the major collagen fibres within the meniscus that create resistance to hoop stresses. These lesions lead to a significant mean increase in contact pressure and a decrease in contact area like after a subtotal meniscectomy. ^, Repair of meniscal radial injuries is the treatment of choice with the aim of restoring joint kinematics and contact pressures and delaying the development of osteoarthritis.

The goal of this chapter is to report the existing knowledge regarding meniscal radial tears, including the anatomy and biomechanics, diagnosis, surgical treatment methods and results.

Pathoanatomy and Biomechanics

Radial tears of the menisci can involve either the lateral or the medial meniscus, in stable knees (isolated) or in association with a lesion of the cruciate ligaments. Biomechanical studies have reported the importance of meniscal repair for radial tears of the lateral meniscus.

Bedi et al. tested contact pressures associated with radial tears involving 30%, 60% and 90% of the width of the medial meniscus. Radial tears involving 90% of the meniscal width were associated with a significant increase in contact pressures, whereas those involving 30% and 60% of the meniscal width were not. Subsequent meniscectomy lead to a further increase in contact pressure compared with that seen in association with the 90% radial tear. Lee et al. tested contact pressures in cadaveric knees with radial tears involving 50% and 75% of the width of the posterior part of the medial meniscus and those in knees with partial meniscectomy and complete medial meniscectomy. Radial tears involving 50% and 75% of the width of the posterior part of the medial meniscus, partial meniscectomy, and complete medial meniscectomy were associated with significant increases in contact pressures that correlated with the depth of the tear and amount of resection. Peak contact pressure in knees with complete meniscectomy increased by 136% compared with those in knees with an intact meniscus.

Diagnosis

Patients often have pinpoint joint line pain at the location of a radial meniscus tear. The clinical examination of meniscal radial tears can be challenging. The history is often traumatic with a twisting injury after a jump. Symptoms are scarce and include joint effusion and pain over the same compartment. Symptoms on the lateral side can be masked by associated anterior cruciate ligament (ACL) and/or medial collateral ligament (MCL) tears.

Imaging is mandatory, and magnetic resonance imaging (MRI) is considered to be the gold standard. MRI features of radial tears include the ghost meniscus in the midbody portion, defined as the absence of identifiable meniscus on a given coronal or sagittal image or the visible triangular form of the meniscus but with high signal replacing the normal dark meniscal signal, with normal meniscus seen on the immediately adjacent images; a high signal in axial views perpendicular to the axis of the meniscus body, indicating a disruption of the meniscus, and a truncated triangle sign, defined as the abrupt termination of the normal triangular meniscal contour at its tip on a sagittal or coronal image; and a cleft sign, defined as a linear, vertical high signal extending through the meniscus on a coronal or sagittal image ( Fig. 17.1 ).

Surgical Treatment

Radial tears of the menisci are considered to be complex lesions, and there is a high risk of partial or extended meniscectomy if the lesion is entirely removed. Given the suboptimal outcomes and high reoperation rates, especially in high-demand individuals, there has been increased interest in repairing radial meniscus tears. The senior author feels that meniscus repair should be the only option for these tears. ^,

Patient preparation, positioning, and arthroscopic knee balance are not specific. The optimal position to repair a midbody or posterior horn lateral meniscus for a medial radial lesion is the figure-of-four position and with the knee in 10 degrees of flexion. Depending on the evaluation of the tear pattern, repair techniques include suture anchors and side-to-side pull-out sutures (all inside, outside in).

Branch et al. reported a biomechanical study comparing four different constructs of inside-out or all-inside meniscal repair of radial tears. They concluded that complex all-inside repair constructs had significantly higher failure loads than a conventional, simple inside-out suture repair construct for repair of radial meniscal tears. Buckley et al. compared three different techniques including transtibial and hybrid techniques. The results showed equivalence of biomechanical testing and strength between the two techniques. Stender et al. evaluated two outside-in techniques using complex sutures (hashtag, crosstag) and concluded that they were able to limit displacement into the suture and to significantly increase load to failure compared with classic horizontal sutures.

Alentorn-Geli et al. made a systematic review of biomechanical studies and concluded that there were no conclusive data to suggest that inside-out or outside-in techniques had better load to failure or stiffness, less displacement or different site of failure compared with all-inside repair. Thus, according to biomechanical data, the technique should be based on the surgeon’s experience and preference.

Some techniques are listed next, but this is not an exhaustive presentation of all techniques available in the literature ( Fig. 17.2 ).

Repair With Transtibial Tunnels

A two-tunnel transtibial pull-out repair technique has been described, derived from root repair techniques, because of its theoretical ability to restore tibiofemoral contact pressures and contact area. This type of fixation has several advantages, including a significant decrease in the gap distance at the repair site. By anchoring the meniscus to the tibia, transtibial sutures decrease the dissipating forces produced by the femur onto the meniscus. Finally, the release of biological factors near the tear site as a result of tunnel drilling may have beneficial effects.

Repair With Side-to-Side Sutures Outside In

In repair with outside-in side-to-side sutures the synovial and meniscal abrasion is performed with a shaver, with the purpose of improving the vascular supply. ^, The method makes use of two 18G spinal needles traversing the meniscus with two no. 0 PDS (polydioxanone) sutures. The first needle is placed from the outside to pierce through the capsule to the desired area of the meniscus repair. Once the needle is placed, no. 0 PDS is passed across the spinal needle and anteriorly retrieved from the anterior portal with a grasper; a small incision is also made at the area of the needle down to the capsule. This is repeated with a second needle placed on the opposite side of the lesion (horizontal suture). Once both no. 0 PDS sutures are passed through the meniscus and delivered to the anterior portal, a ‘shuttle relay’ is made with one of the sutures, leaving only one suture with two strands outside. Then the two strands are tied over the capsule. A second suture is performed using the same principles.

Repair With Side-to-Side Sutures All Inside

For the hashtag technique (the author’s preferred technique), the sutures are placed horizontally to the medial and lateral edges of the tear over the vertical mattress sutures. Placed on each side of the tear, the vertical mattress sutures are positioned such that when combined with the horizontal sutures (hashtag) and the cross sutures (crosstag), they theoretically serve as a ripstop to increase the strength and stability of the repair, similar to a modified Mason-Allen suture. The vertical mattress sutures are then placed 3 mm and 6 mm from the meniscal rim and 3 mm from the tear. The horizontal and oblique sutures are placed over the vertical mattress sutures at 3 mm and 6 mm from the meniscal rim and 3 mm from the tear.

Postoperative Management

Although there is no consensus regarding the postoperative protocol of meniscal radial repair, it is well known that the strain is increased with weight bearing. Additionally, flexion increases the tensile forces on the repaired radial tear. Therefore a hinged knee brace and toe-to-touch weight bearing are recommended for 6 weeks. Weight bearing and flexion greater than 90 degrees are allowed 6 weeks after surgery.

After 5 weeks, the use of the brace can be discontinued and the patient may begin full knee range of motion (beyond 90 degrees of flexion) and full weight bearing. Sport-specific drills are allowed around 3 months after surgery. Full return to sport involving pivoting, squatting, twisting and running is typically allowed at 5 to 6 months after the operation based on the progression of each particular patient.

Results

In a systematic literature review, Moulton et al. reported on the clinical outcomes of six studies (55 patients) at a mean follow-up of 36 months. Clinical outcomes were good, although a lack of data did prompt some concern regarding long-term degeneration of the joint. There are many reports on meniscal healing as assessed by MRI; however, MRI assessment remains difficult because signal changes at the repair site cannot be distinguished between scar tissue, healing and a recurrent/unhealed tear. ^, In contrast, arthroscopic assessment enables evaluation of synovial coverage on the repair site and stability using probes. Because of this, second-look arthroscopy has been considered the gold standard for evaluating the healing status of repaired menisci. A few studies have reported on second-look arthroscopy after repair of complete radial tears. A summary of all studies reporting anatomical results using second look arthroscopies is provided (Table 17.1) .

TABLE 17.1

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