Anatomical significance of a posterior horn of medial meniscus: the relationship between its radial tear and cartilage degradation of joint surface

Abstract

BackgroundTraumatic injury and surgical meniscectomy of a medial meniscus are known to cause subsequent knee osteoarthritis. However, the difference in the prevalence of osteoarthritis caused by the individual type of the medial meniscal tear has not been elucidated. The aim of this study was to investigate what type of tear is predominantly responsible for the degradation of articular cartilage in the medial compartment of knee joints.MethodsFive hundred and forty eight cadaveric knees (290 male and 258 female) were registered in this study. The average age of cadavers at death was 78.8 years old (range: 52-103 years). The knees were macroscopically examined and their medial menisci were classified into four groups according to types of tears: "no tear", "radial tear of posterior horn", "other types of tear" and "worn-out meniscus" groups. The severity of cartilage degradation in their medial compartment of knee joints was evaluated using the international cartilage repair society (ICRS) grading system. We statistically compared the ICRS grades among the groups using Mann-Whitney U test.ResultsThe knees were assigned into the four groups: 416 "no tear" knees, 51 "radial tear of posterior horn" knees, 71 "other types of tear" knees, and 10 "worn-out meniscus" knees. The knees with substantial meniscal tears showed the severer ICRS grades of cartilage degradation than those without meniscal tears. In addition, the ICRS grades were significantly severer in the "radial tear of posterior horn" group than in the "other types of tear" group, suggesting that the radial tear of posterior horn in the medial meniscus is one of the risk factors for cartilage degradation of joint surface.ConclusionsWe have clarified the relationship between the radial tear of posterior horn in the medial meniscus and the severer grade of cartilage degradation. This study indicates that the efforts should be made to restore the anatomical role of the posterior horn in keeping the hoop strain, when patients' physical activity levels are high and the tear pattern is simple enough to be securely sutured.

Meniscus root refixation technique using a modified Mason–Allen stitch

“…Such type of tear is biomechanically equivalent to a total meniscectomy [4,10]. The posterior portion of the medial meniscus carries a greater proportion of the load than does the anterior portion [11,25]. Hence, the early detection and repair of tears in the posterior medial meniscus root are important [10].…”

“…The load transmission function is maintained by the hoop strain mechanism of the meniscus and crucial to prevent degenerative changes [4,11]. A complete posterior medial meniscus root tear results in the failure of the hoop strain mechanism and a loss of the ability to resist extrusion under axial loading [17].…”

Transosseous Repair of Root Tears of the Lateral Meniscus: Operative Technique and Short-Term Clinical Follow-Up of 28 Patients

“…Furthermore, a higher rate of cartilage degradation associated with PLMRT has been reported [8] and increased contact pressures and decreased contact areas correlating with the existence of PLMRT have been demonstrated [20][21][22][23].…”

“…Therefore, repair of the ACL and effective stabilization of the meniscus root seem to be important to first prevent increased pressure on the lateral and medial compartment [24] and to secondary prevent cartilage degradation [8].…”

Patterns of Meniscal Damage Associated with Acute ACL Rupture

“…MMTs however, are more common in chronic ACL deficiency [10,12,14]. This difference in tear occurrence is usually attributed to the anatomic and functional differences that exist between the two menisci, especially in the ACL deficient knee, the lateral meniscus relatively loosely attached to the tibial plateau which allows it to be quite mobile, whereas the medial meniscus, is firmly attached to the tibia, especially at the posterior horn [12,16,17]. This firm attachment allows the medial meniscus to act as a knee stabilizer, a significant restraint to anterior tibial translation in the ACL deficient knee [18][19][20][21].…”