Acromial and Scapular Spine Fractures following Reverse Total Shoulder Arthroplasty-A Systematic Review of Fixation Constructs and Techniques

Variations in the Anatomic Morphology of the Scapular Spine and Implications on Fracture After Reverse Shoulder Arthroplasty

INTRODUCTION

This study evaluates the role of anatomic scapular morphology in acromion and scapular spine fracture (SSAF) risk after reverse shoulder arthroplasty (RSA).

METHODS

Twelve scapular measurements were captured based on pilot study data, including scapular width measurements at the acromion (Z1), middle of the scapular spine (Z2), and medial to the first major angulation (Z3). Measurements were applied to 3D-CT scans from patients who sustained SSAF after RSA (SSAF group) and compared with those who did not (control group). Measurements were done by four investigators, and the intraclass correlation coefficient was calculated. Regression analysis determined trends in fracture incidence.

RESULTS

One hundred forty-nine patients from two separate surgeons (J.L., A.M.) were matched by age and surgical indication of whom 51 sustained SSAF after reverse shoulder arthroplasty. Average ages for the SSAF and control cohorts were 78.6 and 72.1 years, respectively. Among the SSAF group, 15 were Levy type I, 26 Levy type II, and 10 Levy type 3 fractures. The intraclass correlation coefficient of Z1, Z2, and Z3 measurements was excellent (0.92, 0.92, and 0.94, respectively). Zone 1 and 3 measurements for the control group were 18.6 ± 3.7 mm and 3.2 ± 1.0 mm, respectively, compared with 22.5 ± 5.9 mm and 2.0 ± 0.70 mm in the SSAF group, respectively. The fracture group trended toward larger Z1 and smaller Z3 measurements. The average scapular spine proportion (SSP), Z1/Z3, was significantly greater in the control 6.20 ± 1.80 versus (12.60 ± 6.30; P < 0.05). Regression analysis showed a scapular spine proportion of ≤5 was associated with a fracture risk <5%, whereas an SSP of 9.2 correlated with a 50% fracture risk.

DISCUSSION

Patients with a thicker acromions (Z1) and thinner medial scapular spines (Z3) have increased fracture risk. Understanding anatomic scapular morphology may allow for better identification of high-risk patients preoperatively.

Outcomes of conservative treatment of acromial and scapular spine stress fracture post reverse shoulder arthroplasty: a systematic review with meta-analysis

INTRODUCTION

Acromial and scapular spine stress fractures are common complications post reverse shoulder arthroplasty. A systematic review with meta-analysis was conducted to evaluate the clinical outcomes of conservatively treated acromial and scapular spine stress fractures post reverse shoulder arthroplasty in comparison to nonfracture control.

METHODS

Embase, MEDLINE, and Web of Science were searched on September 9, 2022, using various terms related to fracture, acromion, scapula, and reverse shoulder arthroplasty. Meta-analysis using a random effects model was performed on common outcome scores. Risk of bias was assessed using the Joanna Briggs Institute tools for case-controlled studies. Sensitivity analysis was performed for imputed standard deviations and studies with <20 participants.

RESULTS

Thirteen studies with a total of 339 fracture and 3142 control patients were included in the systematic review. Meta-analysis was performed on 12 studies assessing active forward flexion, abduction, external rotation, Constant-Murley score, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, pain score, Simple Shoulder Test, and Single Assessment Numeric Evaluation. Fracture patients experienced significantly poorer functional outcome compared with control patients when the fractures were managed conservatively. Levy III fractures tend to experience worse outcomes. Pain score did not demonstrate a statistically significant difference between the fracture and nonfracture cohort.

DISCUSSION

Currently, literature regarding surgical management is lacking, partially because of a dearth of high-quality literature but also hindered by a lack of standardized techniques. This review was limited by inclusion of studies of low evidence, small sample sizes, and inconsistency in outcome measurement and follow-up period. Overall, patients with acromial and scapular spine stress fractures treated conservatively are expected to have reduced shoulder function compared to nonfracture patients, with the spine of scapula fracture patients suffering the poorest outcomes. Future studies should aim to use the same sets of outcomes parameters to assess the patients at fixed time intervals and report outcomes stratified by Levy classification. This will enable interinstitutional collaboration and pooling of results.

Mitigating Fracture of the Acromion and Scapular Spine After Reverse Shoulder Arthroplasty: A Critical Analysis Review of Patient and Surgical Risk Factors

LEVEL OF EVIDENCE

Level V. Narrative Review. See Instructions for Authors for a complete description of levels of evidence.

The Evolution of Reverse Total Shoulder Arthroplasty-Where Do We Stand and What Comes Next?

Over 35 years ago, the pioneer Paul Grammont from Lyon published his ideas of a reversed semi-constraint prosthesis improving the moment arm of the deltoid by medializing the center of rotation and lengthening of the arm and thus increasing deltoid muscle tension [...].