Injury to the axillary nerve after reverse shoulder arthroplasty: an anatomical study

Area of Science:

• Orthopedic surgery
• Neuroanatomy
• Biomechanical analysis

Background:

• Subclinical neurological lesions, especially axillary nerve involvement, frequently occur after reverse shoulder arthroplasty.
• Postoperative arm lengthening is a known risk factor for these neurological complications.

Purpose of the Study:

• To anatomically assess the relationship between the axillary nerve and prosthetic components post-reverse shoulder arthroplasty.
• To test the hypothesis that inferior glenosphere overhang increases axillary nerve risk.

Main Methods:

• Dissection of eleven fresh-frozen shoulder specimens previously treated with reverse shoulder arthroplasty via a deltopectoral approach.
• Basic science cadaver study to quantify nerve-implant proximity.

Main Results:

• The axillary nerve was consistently more than 15mm from the glenosphere.
• The anterior branch of the axillary nerve showed close contact with the posterior metaphysis or humeral implant (mean distance 5.2±2.1mm).
• Inferior glenosphere overhang averaged 6.0±4.3mm but did not correlate with nerve proximity.

Conclusions:

• Axillary nerve proximity to the posterior metaphysis or humeral implants is a potential risk factor for nerve injury after reverse shoulder arthroplasty.
• This study quantifies axillary nerve proximity to implants, offering crucial clinical insights.