Biomechanical comparison of screw and anchor fixation methods for bone grafting in glenoid anterior defects in cadavers

In 1954 Latarjet described the surgical technique is still routinely used for the treatment of recurrent shoulder dislocations. Anchors is an alternative to the metal screw use in Latarjet procedures. The purpose of this study is to compare fixation ability of metalic implants/screw and anchors in Latarjet procedures. Bone defect was made in the anteroinferior part of the 12 fresh frozen cadaver glenoid cavity. Latarjet method was applied using 2 different fixation method. First group, fixed with two 3.5 mm glenoid and a 4.75 mm knotless anchors (DePuy Mitek Inc. Raynham, MA), while a 3.5 mm cannulated titanium Latarjet screws (Bristow-Latarjet Instability Shoulder System, DePuy Mitek Inc. Raynham, Ma) in the second group. Then the cadavers were placed in Universal Testing / Tensile testing Machine. To ensure complete initial contact, a load of 1 N was suspended directly to the graft, followed by a cyclic loading ranging between 5-150 N to the grafts and a static load enough to cause a 7 mm displacement from the starting point. Elongation, peak to peak displacement, stiffness and maximum load were analyzed using the SPSS program. When we examine the results of the analysis, the difference between the averages of elongation was not statistically significant (p> 0.05). That means, although the screw group is less displaced during cyclic loading, the averages of the elongation are similar. There was no statistically significant difference between the P-P displacement levels of either group when T-test analysis (P=0.926) was performed. There was no statistical significance difference between the groups'in terms of stiffness averages at 5 mm (P=0.487) using the T-test analysis. When evaluating the T-test analysis results of the maximum load amount in the two groups, no significant difference was discovered (P=0.406). Finally it is perhaps of greater advantage to use anchors adjacent to the joint because of its smallness in size and bioabsorbability and does not require future removal of the implant. In addition, there is no damage to the glenoid posterior cortex with the use of anchor, resulting less neurological/mechanical damage in this technique. Another important point to be noted is that artefacts resulting from screw could be avoided in situations where visualization examination for diagnostic purposes is required in the future. Key words: Shoulder instability, Latarjet method, screw complications, anchor