Biomechanical Effects of a Partial Undersurface Medial Meniscal Tear

Numerous studies have shown the biomechanical properties of the meniscus can be restored with repair. The aim of this study is to evaluate if partial undersurface tears of the medial meniscus encountered at the time of arthroscopy have any biomechanical impact on the contact area and peak pressure of the knee. Methods: Nine unmatched cadaveric knees were harvested. The knees were inspected for prior disease and then prepared for loading on an MTS hydraulic machine at 1800N at 0 degrees of flexion. A 1.5cm, 50% partial undersurface tear of the medial meniscus was simulated, starting posterior to the deep medial collateral ligament (MCL) and continuing towards the posterior horn. After the simulated tear the specimens were trialed at 1800N on the MTS machine. Contact area and peak pressure were recorded. Results: There was no difference in the contact area before or after the simulated tear on the medial meniscus. Medial contact area in mm2 was 286.2 in the control group vs. 294.7 in the tear group (p=0.441). Lateral contact area in mm2 was 400.3 in the control group, compared to 383.6 in the tear group (p=0.139).No difference in peak pressure before or after the simulated medial meniscus tear on the medial or lateral meniscus was demonstrated. Peak pressure on the medial meniscus was 3678.7KPa in the controls and 3545.8 in the tear group, with p=201. Peak pressure laterally was 5893.2KPa in controls vs. 5721.0 in tears with a p=953. Conclusion: Statistical analysis demonstrates no biomechanical difference in contact area or peak pressure when a medial undersurface partial meniscal tear is encountered during arthroscopy. It may be extrapolated from this data that is safe for a surgeon who encounters this type of tear to treat it non-surgically or without repair at the time of surgery. Matthew J Brown*, David Feiner and William Wind Department of Orthopaedic Surgery, University at Buffalo, USA Matthew J Brown, et al. Sports Medicine and Rehabilitation Journal Remedy Publications LLC. 2016 | Volume 1 | Issue 1 | Article 1002 2 at our institution. Nine unaltered fresh-frozen cadaveric knees were harvested from the Department of Anatomy Laboratory. Anteroposterior radiographs were taken, with any knee demonstrating radiographic signs of arthritis (joint-space narrowing, flattening of the condyles, osteophytes or chondrocalcinosis) being eliminated. The harvested knees were transected across the femur and tibia to isolate the knee joint and the knees were stripped of muscle, tendon, and patella, retaining the cruciate and collateral ligaments. An anterior capsulectomy was performed to grossly inspect the joint for any signs of meniscal or articular cartilage injury. The meniscofemoral and meniscotibial (coronary) ligaments were incised to allow placement of the Tekscan sensor (Tekscan, South Boston, Massachusetts). The sensor was placed beneath the medial meniscus and on top of the tibial plateau for better conformity. A transverse 10-mm drill hole was made in the distal tibia and then the medullary canal of the tibia was reamed. A threaded rod was placed through the tibial drill hole and then the tibia was potted in methyl methacrylate. The femoral medullary canal was also reamed and potted in methyl methacrylate cement. A drill hole was made through the femur in the sagittal plane to allow unconstrained varus/ valgus rotation during load testing. A custom stainless steel rod was inserted through the femoral hole and attached to the model 858 Mini Bionix load machine (MTS Systems Corp, Eden Prairie, Minnesota). The tibiofemoral joint surface was oriented parallel to the floor with the knee held in full extension and measured goniometrically at 0°c, constrained but allowing for varus/valgus angulations. An 1800N load was applied axially through the knee, consistent with prior studies and to simulate load during normal gait (2.5 times body weight of the average 70-kg individual), with the Tekscan 410-N knee sensor recording contact area and peak contact pressure (Figure 1) [10,11]. Knees were calibrated using an 1800-N load with that calibration file applied to the Tekscan data. The control knee contact area and peak contact pressure of medial or lateral tibiofemoral articulations were recorded over 3 trials. Subsequently, a meniscal tear was simulated with a microscalpel through the anterior capsulectomy. The simulated tear was made posterior to the deep MCL continuing posteriorly towards the posterior horn. The tears were standardized at 1.5cm in length and approximately 50% of the meniscal thickness. The knees were loaded onto the MTS with 1800N of axial load, and the peak contact pressure and contact area were again recorded as the average of three trials. Medial and lateral contact area and peak contact pressure were recorded for each knee preand posttear. Descriptive statistics are provided as mean ±standard deviation. Comparisons between groups were calculated with a 1-way analysis of variance. Tukey’s post hoc analysis was completed for all significant analysis of variance results to determine significant pairwise comparisons. A probability value of ≤.05 was considered statistically significant in all tests performed. All statistical analyses were performed with SPSS software (version 15.0, SPSS Inc, Chicago, Illinois). Results A total of nine knees were evaluated using the methods described above. No knees were eliminated during the course of study. The mean peak contact pressure and mean contact area measured in the medial and lateral compartments both before and after meniscal tear are presented in (Table 1). No significant difference in contact area or peak pressure was demonstrated in either medial or lateral compartments with a native meniscus compared to those with a created undersurface tear.