Summary

This cadaveric study analyzed the alteration in glenoid articular surface geometry using computed tomography reconstructions for each experimental simulation of intact and sequential glenoid bone loss conditions, and quantified the correction obtained with two common modifications of the coracoid transfer procedure (Classic Latarjet and Congruent-arc Latarjet) in anterior shoulder instability.

Abstract

Background

Glenoid bone defects alter the osseous anatomy of the glenoid and predispose to recurrent shoulder instability. The purpose of this study was to assess changes in glenoid articular surface geometry in intact and sequential anterior glenoid bone loss conditions (0%, 10%, 20%, 30% and 40%), and to evaluate the restoration obtained with two common bone reconstruction procedures (Classic Latarjet, and Congruent Arc Latarjet). We hypothesized that both procedures would result in complete restoration of the altered articular geometry for each level of sequential glenoid bone loss.

Methods

Anterior glenoid defects were simulated by creating sequential glenoid bone osteotomies (10%, 20%, 30%, 40%) in twelve human cadaveric scapulae. These were then divided into 2 groups of 6 each, and each defect was reconstructed using the Classic Latarjet (CL) and Congruent Arc Latarjet (CAL) procedures. A total of 108 computed tomography scans were performed on (a) intact scapulae (n=12), (b) after each simulation of bone loss (10%, 20%, 30%, 40%, n=48), and (c) after each reconstruction procedure (CL-10%, CAL-10%, CL-20%, CAL-20%, CL-30%, CAL-30%, CL-40%, CAL-40%. n=48). Glenoid articular geometry was analysed with computed tomography scans using 4 parameters (Glenoid Width, Area, Arc-length, and Version) in each experimental condition. Statistical analysis was used to quantify the progressive alteration, and to determine significant differences between intact glenoid parameters and each of the deficient and reconstructed glenoid groups.

Results

Glenoid width and area reduced significantly by approximately 2-2.5mm (overall 10mm from 0-40%) and 50-70 mm2 (overall 255 mm2 from 0-40%) respectively for every 10% increase in glenoid defect. Glenoid version changed by 1.5 to 3 degrees (overall 9 degrees from 0-40%)), and the arc-length at the lower glenoid changed by approximately 1.5 to 3 mm (overall 9 mm from 0-40%)) for every 10% increase in glenoid defect. Loss of glenoid width of 20% was adequately corrected by CL procedure, however, correction with CL was inconsistent at 30% and 40% defects. Glenoid area restoration at 30% defect was inconsistent after CL procedure, and was significantly undercorrected with 40% defect (p<0.05). Glenoid version restoration was inconsistent after CL procedure at 20%, 30%, and 40% defects. Similarly, arc-length restoration was inconsistent at 20% and 30% defects with CL procedure, and was significantly undercorrected with 40% defect (p<0.05). The Congruent arc Latarjet (CAL) procedure restored and overcorrected articular geometry parameters in all bone defects, however the restoration for area and arc-length was inconsistent in 40% glenoid defects.

Conclusion

Glenoid articular surface geometry was significantly altered with sequential increase in anterior bone defects from 0-40%. The classic Latarjet (CL) procedure provided consistent correction of most parameters in bone defects of 10% and 20% only. The Congruent arc Latarjet (CAL) procedure restored and overcorrected most articular geometry parameters even in 40% glenoid defects. Clinical relevance: Large glenoid bone defects (30-40%) represent a severe form of significant bone loss. Treatment algorithms for glenoid bone loss in anterior shoulder instability should incorporate specific reconstructive procedures that can restore the altered glenoid articular geometry.