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. 2023 Oct;51(12):3211-3216.
doi: 10.1177/03635465231197661. Epub 2023 Sep 21.

Correlation of Acromial Morphology With Risk and Direction of Shoulder Instability: An MRI Study

Justin W Arner  1 , Philip-Christian Nolte  2 , Joseph J Ruzbarsky  2 , Thomas Woolson  2 , Matthew T Provencher  2 , James P Bradley  1 , Peter J Millett  2
Affiliations

Correlation of Acromial Morphology With Risk and Direction of Shoulder Instability: An MRI Study

Justin W Arner et al. Am J Sports Med. 2023 Oct.

Abstract

Background: The influence of bony morphology on the development of posterior shoulder instability is not well known.

Purpose: To determine if acromial morphology, as measured on magnetic resonance imaging (MRI), is associated with posterior or anterior shoulder instability.

Design: Cross-sectional study; Level of evidence, 3.

Methods: MRI measurements of posterior acromial coverage (PAC), posterior acromial height (PAH), posterior acromial tilt (PAT), and anterior acromial coverage (AAC) were completed for 3 separate matched groups who underwent surgical intervention: posterior instability, anterior instability, and a comparison group of patients who underwent arthroscopic surgery for snapping scapula. Inclusion criteria were patients with recurrent instability <40 years of age without multidirectional instability, glenoid bone loss >13.5%, or glenoid retroversion >10%.

Results: Overall, 37 patients were included in each group. PAC was significantly less in the posterior instability group than in the anterior instability and comparison groups (68.3° vs 88.7° vs 81.7°; P < .001). PAH was significantly greater in the posterior group than in the anterior instability group (11.0 mm vs -0.1 mm; P < .001) and comparison group (0.7 mm; P < .001). There was no difference between the posterior and anterior groups in terms of PAT or AAC (P = .45 and P = .05, respectively). PAT was significantly smaller in the posterior instability group than the comparison group (55.2° vs 62.2°; P = .026). The anterior and comparison groups were not significantly different in PAH or PAT (P = .874 and P = .067, respectively) but were significantly different in AAC (P = .026).

Conclusion: A higher and flatter posterior acromion, as measured on preoperative MRI, appears to be associated with patients who require arthroscopic capsulolabral repair due to posterior shoulder instability. This information may help clinicians to both diagnose and predict the need for operative intervention for patients with posterior labral tears.

Keywords: acromial morphology; magnetic resonance imaging; posterior shoulder instability; shoulder instability.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: J.W.A. has received research support from Arthrex and DJO and hospitality payments from Mid-Atlantic Surgical Systems and Smith & Nephew. P.-C.N. has received support for education from Arthrex. M.T.P. has received consulting fees and royalties from Arthrex, consulting fees and honoraria from Joint Restoration Foundation Inc, consulting fees from Zimmer Biomet Holdings, honoraria from Flexion Therapeutics Inc, and royalties or license from Arthrosurface Inc and Anika Therapeutics. J.P.B. has received royalties and consulting fees from Arthrex and DJO. P.J.M. has received consulting fees and royalties from Arthrex. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

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