Primary bone graft stability after Latarjet surgery: biomechanical evaluation of a fixation technique with metal-free all-suture cerclage vs. cortical screws

Abstract

To reduce hardware-related complications in coracoid graft fixation to the anterior aspect of the glenoid, a metal-free Latarjet technique was recently introduced. The aim of this study was to compare the primary stability of a classic Latarjet procedure with two metal screws to a novel metal-free, all-suture cerclage method. It is hypothesized that fixation of the coracoid graft with two malleolar screws provides higher primary stability compared to an all-suture cerclage technique. This biomechanical in-vitro study was conducted on 12 fresh-frozen cadaveric shoulders (six matched pairs) with a mean donor age of 80 years (range, 67-89). Coracoid graft fixation was performed using a new all-suture cerclage technique (group A) or a classic Latarjet technique with two 4.5 mm malleolar screws (group B). The conjoint tendon was loaded with a static force of 10 N to simulate the sling effect. Graft loading with a probe head consisted of six ascending load levels (1. 10-50N, 2. 10-100N, 3. 10-150N, 4. 10-200N, 5. 10-250N, 6. 10-300N) with 100 cycles each at one Hertz. Relative motion of the bone graft to the glenoid was measured using an optic three-dimensional system. While loading the conjoint tendon with 10 N no difference in mean displacement of the bone-graft was found between both groups (p=0.144). During cyclic loading a significant difference in relative displacement for both groups was already detected in load level one (Group A: 2398,8 μm vs. Group B: 125,7 μm; p=0.024) and this trend continued with the following load levels (p<0.05). The study demonstrated that the innovative metal-free, all-suture cerclage fixation technique results in higher micromotion than the classic coracoid graft fixation with two malleolar screws. According to the present biomechanical investigation, shoulders treated with a metal-free all-suture cerclage technique might need adapted rehabilitation protocols to protect the construct and allow for graft healing.