Background
Surgical indications for All-Inside-Suture (AIS) technique, in which the repair is completed within the joint, is widely performed these days with the improvement of surgical instruments, though Inside-Out (IO) technique is a gold standard in meniscal repair. AIS repair has the advantage of directly suturing the torn meniscus. However, the biomechanical differences of these techniques are still not fully clarified. This study aimed to compare the resultant force (RF) through the meniscus after AIS technique with the RF after IO technique using lateral meniscus (LM) longitudinal tear model in the experimental setting. Our hypothesis was that both techniques would equivalently restore RF through the LM at time zero.
Methods
Nine fresh-frozen porcine knees were tested using a 6-degree of freedom (DOF) robotic simulator. The lateral femoral condyle was osteotomized so that the lateral meniscus could be accessed precisely and was fixed with two screws, which was defined as the intact. Axial load of 300-N was applied to the knee joint at 30°, 60°, and 90° of knee flexion, and the forces and the path of the knee joint were recorded. After detaching the femoral condyle, a 15mm longitudinal tear was created at the half-width of the lateral meniscus in the middle to posterior segments. Next, the LM tear was repaired by IO or AIS techniques and the same tests were performed. After testing for both repair techniques, the sutures were removed and the test was also conducted for the knee only with the tear. Finally, the LM was totally dissected, and the obtained paths were reproduced to calculate the RF through the meniscus using the principle of superposition in each meniscal condition (intact, IO, AIS, and tear).
Results
At 30° of knee flexion, RFs in intact, IO, AIS, and tear conditions were 85.6±55.4 N , 77.1±52.9 N, 80.1±35.1 N, and 58.7±43.4 N, respectively. Although there were no statistical differences, RF in tear condition was lower than those in intact, IO, and AIS conditions, while RFs in IO and AIS conditions were almost equal to that of intact without difference between each other. The similar results were observed at 60° and 90° of flexion.
Conclusion
In the repair of the LM longitudinal tear, both the IO and AIS techniques equivalently restored the RF through the LM at time zero. Both techniques are excellent options for LM longitudinal tear repair, and their indications could be selected according to the site of meniscus injury.