Biomechanical Consequences of a Tear of the Posterior Root of the Medial Meniscus: Similar to Total Meniscectomy

• Published in: Journal of bone and joint surgery. American volume Vol. 90; no. 9; pp. 1922 - 1931
• Main Authors: Allaire, Robert, Muriuki, Muturi, Gilbertson, Lars, Harner, Christopher D
• Format: Journal Article
• Language: English
• Published: Boston, MA Copyright by The Journal of Bone and Joint Surgery, Incorporated 01-09-2008; Journal of Bone and Joint Surgery Incorporated
• Subjects: Adult; Analysis of Variance; Biological and medical sciences; Biomechanical Phenomena; Biomechanics. Biorheology; Cadaver; Diseases of the osteoarticular system; Female; Fundamental and applied biological sciences. Psychology; Humans; Injuries of the limb. Injuries of the spine; Knee Joint - surgery; Male; Medical sciences; Menisci, Tibial - surgery; Middle Aged; Pressure; Stress, Mechanical; Suture Techniques; Tibia - surgery; Tibial Meniscus Injuries; Tissues, organs and organisms biophysics; Traumas. Diseases due to physical agents; Biomechanics; Orthopedic surgery; Treatment; Meniscectomy; Posterior; Break; Semilunar cartilage
• ISSN: 0021-9355; 1535-1386
• DOI: 10.2106/JBJS.G.00748

BackgroundTears of the posterior root of the medial meniscus are becoming increasingly recognized. They can cause rapidly progressive arthritis, yet their biomechanical effects are not understood. The goal of this study was to determine the effects of posterior root tears of the medial meniscus and their repairs on tibiofemoral joint contact pressure and kinematics.MethodsNine fresh-frozen cadaver knees were used. An axial load of 1000 N was applied with a custom testing jig at each of four knee-flexion angles0°, 30°, 60°, and 90°. The knees were otherwise unconstrained. Four conditions were tested(1) intact, (2) a posterior root tear of the medial meniscus, (3) a repaired posterior root tear, and (4) a total medial meniscectomy. Fuji pressure-sensitive film was used to record the contact pressure and area for each testing condition. Kinematic data were obtained by using a robotic arm to record the position of the knees for each loading condition. Three-dimensional knee kinematics were analyzed with custom programs with use of previously described transformations. The measured variables were axial rotation, varus angulation, lateral translation, and anterior translation.ResultsIn the medial compartment, a posterior root tear of the medial meniscus caused a 25% increase in peak contact pressure compared with that found in the intact condition (p < 0.001). Repair restored the peak contact pressure to normal. No difference was detected between the peak contact pressure after the total medial meniscectomy and that associated with the root tear. The peak contact pressure in the lateral compartment after the total medial meniscectomy was up to 13% greater than that for all other conditions (p = 0.026). Significant increases in external rotation and lateral tibial translation, compared with the values in the intact knee, were observed in association with the posterior root tear (2.98° and 0.84 mm, respectively) and the meniscectomy (4.45° and 0.80 mm, respectively), and these increases were corrected by the repair.ConclusionsThis study demonstrated significant changes in contact pressure and knee joint kinematics due to a posterior root tear of the medial meniscus. Root repair was successful in restoring joint biomechanics to within normal conditions.Clinical RelevanceThis study provides a biomechanical rationale for surgical repair of posterior root tears of the medial meniscus. Clinical studies are required to define the appropriate patient population for, and to determine the clinical efficacy of, surgical treatment of this injury.