Factors affecting biomechanical strength of Latarjet constructs: A systematic review and meta-regression

Abstract

Background The Latarjet procedure reduces recurrent glenohumeral instability but has potential hardware and graft complications. The procedure has been modified to use various screw types as well as suture buttons. Biomechanical studies have evaluated the effect of these implants on construct strength. With varying results it is unclear whether there is an optimal implant to use. Methods We conducted a systematic review of human cadaveric biomechanical studies evaluating Latarjet ultimate failure load. Two independent reviewers screened articles and included them after full text review. Additional factors including implants used, graft orientation, cortices engaged, drill diameter, and screw characteristics were recorded. Meta-regression was performed on the 145 specimens from eight studies that met inclusion criteria. Results Screw fixation resulted in a 396.8 N (95% CI, 149.8–643.7) N higher ultimate failure load against shear stresses than suture buttons (p = 0.002). There were no differences between implants for ultimate failure load against tensile forces. Tensile strength was significantly affected by drill diameter with each millimeter of increase reducing the mean ultimate failure load by 127.4 N (95% CI, 41.2–213.6) N (p = 0.004). Conclusions These results suggest that using screw fixation and minimizing drill diameter can obtain the maximum ultimate failure load against both shear and tensile forces in a Latarjet construct.

A Systematic Review of Screw and Suture Button Glenoid Augmentation Constructs

“…A recently published systematic review and meta-regression of the biomechanical strength of Latarjet constructs found that each millimeter increase in the screw diameter significantly reduced the ultimate failure load. 25 Alvi et al 1 did not find a significant difference between two 3.5-mm stainless steel cortical screws versus two 4.0-mm stainless steel partially threaded cancellous screws in the final load at failure. Similarly, Shin et al 48 did not find any differences among the screw types tested, all of which consisted of fixation with 2 screws.…”

“…4,41 In addition, a recent systematic review found that screws produce significantly greater ultimate failure loads than suture buttons when under shear forces. 25 Even though these biomechanical findings may suggest otherwise, clinical studies have reported similar union rates when the 2 constructs are compared, and the same review found suture buttons and screws to be comparable under tensile forces. It is possible that the preservation of bone and maximization of the cancellous contact area with the suture button technique, which may be lost because of greater micromotion, increase union rates.…”

“…2 Surgeons should also take into account screw diameter when performing screw fixation, as increases in the screw diameter can significantly reduce ultimate failure loads. 25 In addition, studies have reported that up to 42% of screws are too long, potentially placing the suprascapular nerve at risk for injuries. 7,23,26 Alternatively, short screws may compromise the stability of graft fixation, which may lead to graft migration or nonunion.…”

Primary Stability and Bone Contact Loading Evaluation of Suture and Screw based Coracoid Graft Fixation for Anterior Glenoid Bone Loss

“…6,15,50 Biomechanical investigations in glenohumeral instability models have shown that suture-based bone block fixation is comparable with screw fixation, although the reported stiffness is higher with screw fixation. 29,30,37,41,54 One reported key to stabilize these constructs is reproducible tensioning, which has been clinically reported to improve the bone block healing rate. 10,22…”

“…6,15,50 Biomechanical investigations in glenohumeral instability models have shown that suture-based bone block fixation is comparable with screw fixation, although the reported stiffness is higher with screw fixation. 29,30,37,41,54 One reported key to stabilize these constructs is reproducible tensioning, which has been clinically reported to improve the bone block healing rate. 10,22 Although suture-based constructs are promising for glenoid reconstruction, there is currently a lack of biomechanical data regarding the initial fixation strength and cyclic contact loading at the graft-glenoid interface after suturebased or screw fixation.…”