ISAKOS Congress 2021

2021 ISAKOS Biennial Congress Paper

 

The Orientation of the Acromion is Not Associated with Different Asymmetric Posterior Glenoid Erosion Patterns

Alexander Otto, MD, Neufahrn, Bavaria GERMANY
Bastian Scheiderer, MD, Munich, Bavaria GERMANY
Julian Mehl, MD, Munich, Bavaria GERMANY
Elifho Obopilwe, ME, BSc, Farmington, CT UNITED STATES
Patrick J. Denard, MD, Medford, OR UNITED STATES
Anthony A. Romeo, MD, Burr Ridge, IL UNITED STATES
Augustus D. Mazzocca, MS, MD, Farmington, CT UNITED STATES

Department of Orthopaedic Surgery, UConn Musculoskeletal Institute, University of Connecticut, Farmington, CT, UNITED STATES

FDA Status Cleared

Summary

The variability of B2 glenoids and their association to the acromial orientation were assessed in 3D models that were reconstructed from CT scans.

Abstract

Background

Posterior glenoid wear remains a challenge in anatomic and reverse total shoulder arthroplasty (rTSA) due to an asymmetric erosion with altered retroversion. It has been suggested that orientation of the acromion influences glenohumeral joint reaction forces and thus the development of posterior glenoid erosion. The purpose of this study was to assess glenoid morphology and acromial orientation in posterior glenoid erosion patterns by utilizing 3D models.

Material And Methods

CT shoulder scans from three study centers of patients awaiting rTSA between 2017 and 2018 were converted into 3D models (Mimics©, 3-Matic©; Materialise©, Leuven, Belgium) and analyzed by two observers. Morphology, orientation and greatest depth of erosion, inclination, current retroversion and premorbid retroversion, surface areas of the glenoid, and external acromial orientation as well as posterior acromial slope were assessed. Measurements were compared by wear patterns, entities and gender.

Results

In the complete cohort of 68 patients (63.8 ± 10.0 years; 19 females, 49 males) a mean of 85.9° (± 22.2°) was observed for the glenoid erosion orientation. Additionally, a further distinct classification of the glenoid erosion as posterior-central (pc, N = 39), posterior-inferior (pi, N = 12), and posterior-superior (ps, N = 17) wear patterns was possible. These wear patterns significantly (P < 0.001) distinguished by erosion orientation (pc = 86.9° ± 12.0°, pi = 116.3° ± 10.3°, ps = 62.3° ± 18.9°). The greatest depth of erosion found was 7.3mm ±2.7mm in pc wear patterns (pc vs. pi: P = 0.03; pc vs. ps: n.s.; pi vs. ps: n.s.). Overall the observed erosion divided the glenoid surface into a paleoglenoid proportion of 48% (± 11%) and neoglenoid proportion of 52% (±12%). For the complete cohort, glenoid inclination was 85.4° (± 6.6°), premorbid glenoid retroversion was 80.7° (±8.1°), current glenoid retroversion was 73.4° (± 7.4°) with an estimated increase of 6.9° (±6.0°). Mean external acromial orientation was 118.2° (± 8.9°), and the mean posterior acromial slope was 107.2° (± 9.6°). There were no further significant differences if parameters were compared by wear patterns, entities and gender.

Conclusion

The current analysis was able to distinguish three significantly different orientated wear patterns (posterior-superior, -central, and –inferior) in shoulders demonstrating posterior wear on axillary imaging. No significant differences between the observed erosion patterns or any relevant correlations were found regarding the orientation of the acromion.

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