A Biomechanical Comparison of All-Inside Versus Transtibial Meniscus Root Repair Techniques

Background: Meniscus root tears are associated with chondral injury, early degenerative change, and a high conversion rate to total knee arthroplasty. It is well-established that meniscus root tears lead to decreased femorotibial contact area, increased peak contact pressures, and increased stress on the articular cartilage. Purpose: To evaluate the biomechanical characteristics of the all-inside meniscus root repair procedure and compare it with the previously described transtibial technique. Study Design: Controlled laboratory study. Methods: Nine paired cadaveric knees were prepared by removing skin, subcutaneous tissues, quadriceps muscles, patella, and patellar tendon, while leaving the capsule in place. Pressure-mapping sensors were inserted, and specimens underwent compressive loading to obtain peak pressures, mean pressures, and femorotibial contact area in the medial and lateral compartments. Tests were performed as static compression tests with the knee locked at 0 & DEG; of flexion. Compression testing was performed in 3 states: meniscus intact, meniscus root cut, and after meniscus root repair with an all-inside repair technique. Additionally, testing was completed on 9 pairs of cadaveric knees to compare stiffness and maximal load to failure between the all-inside and transtibial meniscus root repair techniques. Results: In the medial compartment, there were significant increases in median peak pressures and median mean pressures in the root cut state as compared with the intact state (+636 kPA [95% CI, 246 to 1026] and +190 kPA [95% CI, 49 to 330], respectively). All-inside meniscus root repair restored median peak pressures and median mean pressures to approach those of the intact meniscus (+311 kPA [95% CI, -79 to 701] and +137 kPA [95% CI, -3 to 277]). In the lateral compartment, there were also significant increases in median peak pressures and median mean pressures in the root cut state as compared with the intact state (+718 kPA [95% CI, 246 to 1191] and +203 kPA [95% CI, 51 to 355]). All-inside meniscus root repair restored median peak pressures and median mean pressures such that they were not significantly different from the intact state (+322 kPA [95% CI, -150 to 795] and +18 kPA [95% CI, -134 to 171]). There was no difference between repair techniques regarding load to failure (P = .896). Transtibial meniscus root repair had significantly more stiffness (mean & PLUSMN; SD, 24.8 & PLUSMN; 9.3 N/mm) as compared with the all-inside meniscus root repair technique (13.6 & PLUSMN; 3.8 N/mm, P = .015). Conclusion: All-inside meniscus root repair reduced median peak and mean pressures to those of the native intact meniscus with the knee in extension in the cadaveric model. When compared with a transtibial meniscus root repair technique, all-inside repair demonstrated decreased stiffness and a similar load to failure.