Is The "Sling Effect" of the Conjoint Tendon in Latarjet Procedures Real? A Systematic Review and Descriptive Synthesis of Controlled Laboratory and Comparative Clinical Studies.

Background: The Latarjet procedure is considered the gold standard for treating patients with anterior shoulder instability in the presence of critical glenoid bone loss. Proponents of the Latarjet contend that its efficacy is in-part attributable to the "sling effect" of the conjoint tendon; however, recent studies have demonstrated similar restoration of anterior stability in patients undergoing free bone block (FBB) procedures. The purpose of this systematic review was to evaluate the biomechanical and clinical evidence for the sling effect.

Methods: A systematic review was performed per PRISMA guidelines. PubMed/MEDLINE, EMBASE, Web of Science, and Cochrane were queried separately for (1) controlled laboratory studies comparing the restoration of anterior stability with and without an intact, tensioned conjoint tendon and (2) comparative clinical studies comparing patient outcomes after Latarjet versus a FBB procedure. A descriptive synthesis of the controlled laboratory studies and a quantitative meta-analysis of comparative clinical studies was performed.

Results: Six controlled laboratory studies and four comparative clinical studies were included. Four of the laboratory studies supported the presence of a sling effect, whereas two studies concluded there was no added effect; however, their data trended in favor of improved anterior stability with the sling effect. Meta-analysis of the four comparative clinical studies demonstrated no difference between Latarjet and FBB for any range of motion measure, outcome score, or the odds of recurrent instability (Odds ratio: 0.83, 95% confidence interval: 0.20-3.52), which is concordant with the findings of each individual study.

Conclusion: While both Latarjet and FBB procedures are efficacious in restoring stability, our critical review of the literature suggests that the reduction in anterior translation attributed to the "sling effect" in biomechanical cadaveric studies is not clinically relevant when sufficient anterior glenoid bone has been restored.