Latarjet Procedure: Biomechanical Evaluation of 2 Screw Coracoid Fixation

Kenny Chang; Oscar Covarrubias; Douglas Scott; David Paller; Andrew Green

doi:10.1016/j.jse.2024.03.035

Latarjet Procedure: Biomechanical Evaluation of 2 Screw Coracoid Fixation

J Shoulder Elbow Surg. 2024 May 4:S1058-2746(24)00318-5. doi: 10.1016/j.jse.2024.03.035. Online ahead of print.

Authors

Kenny Chang¹, Oscar Covarrubias², Douglas Scott³, David Paller², Andrew Green⁴

Affiliations

¹ Alpert Medical School, Brown University, Providence, RI, USA.
² Division of Shoulder and Elbow Surgery, Department of Orthopaedic Surgery, Alpert Medical School, Brown University, Providence, RI, USA.
³ Beaufort Orthopedic Sport and Spine, Hilton Head, SC, USA.
⁴ Division of Shoulder and Elbow Surgery, Department of Orthopaedic Surgery, Alpert Medical School, Brown University, Providence, RI, USA. Electronic address: agshoulder@aol.com.

PMID: 38710366
DOI: 10.1016/j.jse.2024.03.035

Abstract

Background: Coracoid nonunion is a relevant complication following the Latarjet procedure and is influenced by multiple factors, including the method of graft fixation.

Aims: The purpose of this study was to evaluate and characterize the biomechanical properties of various two-screw fixation constructs used for coracoid graft fixation in the Latarjet procedure.

Methods: Forty model scapulae (Sawbones Inc., Vashon, WA, USA) were used for this study. A 15 percent anterior inferior glenoid bone defect was created. The coracoid was osteotomized at the juncture of the vertical and horizontal aspects, transferred to the anterior-inferior edge of the glenoid, and fixed with either two 3.5 mm fully threaded cannulated cortical screws (FTCS), two 3.5 mm fully threaded solid cortical screws (FTSS), two 3.5 mm partially threaded cannulated screws (PTCS), or two 4.5 mm partially threaded malleolar screws (MS). Biomechanical testing was performed with an Instron materials testing machine (Instron Corp., Norwood, MA) by applying loads to the lateral aspect of the transferred coracoid graft. The constructs were preconditioned with non-destructive cyclical loading (0-20N) to determine construct stiffness. After 100 cycles of dynamic loading, the construct was loaded to failure to determine ultimate failure load, yield displacement, and mode of failure.

Results: All failures were associated with plastic deformation of the screws and coracoid graft fracture. There was a significantly lower initial stiffness for PTCS compared to MS (186±49.3 N/mm vs 280±65.5 N/mm, p=0.01) but no significant differences among the other constructs. There was no difference in ultimate failure load (p=0.18) or yield displacement (p=0.05) among constructs.

Conclusion: Two screw coracoid fixation of the coracoid in a simulated classic Latarjet procedure with 3.5 mm fully threaded cortical and cannulated screws is comparable to 4.5 mm malleolar screws in strength, stiffness, and displacement at failure. On the other hand, partially threaded 3.5 mm cannulated screws provide inferior fixation stiffness and could potentially affect clinical outcomes.

Keywords: Latarjet procedure; coracoid graft fixation; glenohumeral instability; glenoid bone loss; screw biomechanics.