Biomechanical Comparison of Inside-Out and All-Inside Meniscal Repair in Controlling the Peripheral Gap and Extrusion of the Lateral Meniscus With a Complete Radial Tear: A Cadaveric Study Using a Robotic Simulator.

Background: Although both the classical inside-out and all-inside techniques are performed for the repair of complete radial tears, which should be the standard technique is, to the authors' knowledge, controversial considering the clinical outcomes and biomechanical studies. There are no biomechanical studies of repairs of the lateral meniscus (LM) evaluating the peripheral side gap (peripheral gap) of the radial tear site and extrusion of the LM, which seems to be important in the treatment of radial tears. Purpose: To compare the inside-out and all-inside meniscal repair techniques by evaluating the peripheral gap and extrusion of the LM with complete radial tear using a 6 degrees of freedom robotic system and fresh-frozen cadavers. Study Design: Controlled laboratory study. Methods: This study was performed using 6 fresh-frozen cadaveric knee specimens, a robotic testing system, and ultrasound evaluation. Ultrasound evaluations were performed to measure peripheral gaps and extrusions. The first ultrasound evaluation under 5 N·m of valgus load was performed on the knee at 30° and 90° of flexion. After a complete radial tear at the midsegment of the LM was created, a second ultrasound evaluation under valgus load was performed. Finally, all-inside and inside-out meniscal repairs done with 1 horizontal suture were performed on the same knee in a randomized order. Subsequently, the third and fourth ultrasound evaluations under valgus load were performed. Results: The peripheral gap of the inside-out meniscal repair technique was significantly smaller than that of all-inside meniscal repairs at knee flexion angles of 30° and 90° (6.0 vs 11.5 mm and 5.6 vs 10.9 mm [both Conclusion: The inside-out meniscal repair technique showed less peripheral gap and extrusion of the LM in a complete radial tear than the all-inside meniscal repair. Inside-out repair may be advantageous for radial tears over all-inside repair because only inside-out repair can tighten the peripheral side of the radial tear. Clinical Relevance: The LM with a complete radial tear should be repaired using the inside-out technique.