International Orthopaedics - 2026-04-23 - Journal Article
Anterior deltoid atrophy after reverse shoulder arthroplasty: a preliminary prospective study on surgical approach and neurophysiological correlates.
Lopiz Y, Rodrígiez-González A, Ossuna-Juntadez E, García-Fernández C, Martín-Albarrán S, Marco F
Topics
Key Takeaway
Anterior deltoid atrophy occurred in 41.9% of RTSA patients and was significantly more common with the superolateral approach than deltopectoral (72.7% vs. 25%, p=0.021), with a 22° deficit in anterior flexion in affected patients.
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Summary
This prospective single-center study evaluated anterior deltoid atrophy incidence, its association with surgical approach and axillary nerve injury, and its functional impact in 31 patients undergoing RTSA for rotator cuff arthropathy via deltopectoral (n=20) or superolateral (n=11) approach. Atrophy was present in 42% overall, with the superolateral approach carrying nearly three times the rate (72.7% vs. 25%, p=0.021); critically, acute postoperative axillary nerve injury rates did not differ between atrophy and non-atrophy groups (23.1% vs. 22.2%, p=NS), implicating mechanical rather than neurogenic aetiology. Patients with atrophy achieved 115° versus 137° anterior flexion at 12 months (difference 22°, Cohen's d=0.87), though this did not reach statistical significance (p=0.066), likely due to underpowering.
Key Limitation
The small, unequal sample size (20 DP vs. 11 SL) prevents definitive conclusions about the 22° flexion difference and precludes multivariate analysis to control for confounders such as preoperative atrophy, tear chronicity, or surgeon-specific technique variation.
Original Abstract
PURPOSE
To assess the incidence of anterior deltoid atrophy following reverse total shoulder arthroplasty (RTSA) for rotator cuff arthropathy (RCA), to investigate its association with the surgical approach and neurophysiological injury of the anterior branch of the axillary nerve, and to determine its impact on postoperative shoulder flexion.
METHODS
Prospective observational cohort study of 31 patients (mean age 77.9 ± 5.4 years; 85% female) with RCA undergoing RTSA at a single tertiary centre (2014-2017). Two approaches were used: deltopectoral (DP, n = 20) and superolateral (SL, n = 11). Neurophysiological evaluation (electroneurography + quantitative needle EMG) of the axillary and suprascapular nerves was performed preoperatively and at three and six months postoperatively by a single experienced neurophysiologist. Anterior deltoid atrophy was assessed at 12 months using a pre-specified standardised clinical inspection protocol: visible anterior deltoid contour concavity at rest, confirmed on active elevation against gravity, graded as present or absent by a single blinded examiner. Convergent support was provided by the observed difference in shoulder flexion between groups and by the EMG data. Shoulder flexion and the Constant-Murley Score (CMS) were recorded at baseline and 12 months.
RESULTS
Preoperative axillary nerve injury was present in 77.4% of patients, predominantly affecting the anterior branch (48.4%). Acute postoperative axillary nerve injury occurred in 25.8% of the overall cohort. At 12 months, anterior deltoid atrophy was identified in 13/31 patients (41.9%), with a significantly higher rate in the SL group (72.7% vs 25%; p = 0.021). The rate of acute postoperative injury to the anterior axillary nerve branch did not differ significantly between patients with and without deltoid atrophy (23.1% vs 22.2%; p = n.s.). Patients with atrophy achieved a mean anterior flexion of 115° (SD 8.7°) versus 137° (SD 7.4°) in those without (difference 22°; 95% CI 1.5-31.2; p = 0.066; Cohen's d = 0.87). Both groups improved significantly from baseline.
CONCLUSION
Anterior deltoid atrophy is common after RTSA (42%) and is significantly associated with the superolateral approach. The absence of a neurophysiological correlate is consistent with a mechanical aetiology related to deltoid reinsertion technique, although causality cannot be established from this observational study. These findings generate a testable hypothesis warranting prospective evaluation of bony acromial flap reinsertion in future comparative studies.