Bone plug versus Suture-Only Fixation of Medial Meniscus Allograft Transplantation. Biomechanical Study

OBJECTIVES: Our objective was to evaluate the contact load characteristics of medial meniscus allograft transplantation performed by bone-plug versus soft-tissue suture-only fixation in cadaveric knees. Our null hypothesis was that there would not be significant differences between the two fixation groups with regard to load contact pressures and distribution. METHODS: Experimental laboratory study in nine fresh-frozen human cadaveric knees (mean age 46.3 years, range 41-50; 5 female). None had cartilage, ligament or meniscal lesions as evaluated by XR and MRI exam. Fresh-frozen, size- and side-matched medial meniscus allografts were obtained based on XR measurements (Pollard method). The knees were secured in a load apparatus where rotation, flexion, extension and tilt were adjusted to ensure correct knee alignment during loading. The tibiofemoral joint surface was oriented parallel to the floor while the femur was placed in three positions: 0, 30 and 60 degrees. A 700N load was applied axially through the knee. Mean and Peak Contact Pressure and contact area were measured with an I-scan pressure sensor-4011 (Tekscan, Boston / MA) placed underneath the medial meniscus through a small capsular incision. The same protocol was applied for each condition: native meniscus, meniscectomy, meniscal allograft transplantation with bone plug (MAT-bone) and with suture-only fixation (MAT-suture). Two measurements were taken under each testing condition. Meniscus transplants were first secured with bone plugs and capsular sutures, and measurements taken. Then, the bone plugs were carefully removed from the meniscal roots and the recipient slots in the tibial plateau filled with cement. The roots were then re-secured with trans-tibial suture-only fixation. The results of mean and peak contact stress and contact area were compared between intact, meniscectomized, MAT-bone and MAT-suture using analysis of variance (ANOVA). The level of significance was set at lower than p0.05. RESULTS: Meniscectomy significantly increased mean contact pressure and the contact area was significant reduced in comparison with the native condition at 0,30 and 60 degrees (p.001). Although the peak contact pressure was higher in the meniscectomy group, it was not statistically significant. Suture-only fixation resulted in slightly higher contact pressure and smaller contact area than bone plug fixation. No significant differences were found for mean and peak contact pressures and contact area between MAT-bone and MAT-suture. Also, regardless of technique, no significant differences were found between transplanted meniscus and native condition. The only exception occurred in 0 degrees of flexion, where MAT-suture demonstrated a statistically significant smaller contact area when compared with the native meniscus (p.016). CONCLUSION: This study demonstrated that meniscal allograft transplantation can restore load parameters close to the native condition. No significant differences were detected between bone-plug and soft-tissue fixation. This study is unique in utilizing size-matched meniscal transplants and using the same transplant for bone plug and suture-only fixation, thus reducing confounding factors.