Nerve stress during reverse total shoulder arthroplasty: a cadaveric study.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Neuroscience

Background:

• Neurologic lesions are a known complication following total shoulder arthroplasty.
• Traction injury is the primary cause of these neurologic lesions.
• Identifying surgical factors contributing to nerve stress during reverse total shoulder arthroplasty (RTSA) is crucial.

Purpose of the Study:

• To determine specific arm manipulations and surgical steps during RTSA that increase stress on nerves.
• To provide data to help surgeons minimize iatrogenic nerve injury during RTSA.

Main Methods:

• Nerve stress was quantified using a tensiometer on brachial plexus nerves in 10 cadaveric shoulders.
• Measurements were taken during various arm positions and surgical steps of RTSA.
• The influence of implant size (polyethylene humeral cup thickness) on nerve stress was also assessed.

Main Results:

• Internal rotation increased radial and axillary nerve stress; external rotation increased musculocutaneous, median, and ulnar nerve stress.
• Shoulder extension significantly increased stress on all measured nerves.
• Humeral and glenoid exposition were identified as high-risk steps, with extension exacerbating stress.
• Thicker polyethylene humeral cups correlated with increased nerve stress for most nerves.

Conclusions:

• Limiting shoulder extension during humeral preparation is essential.
• Careful technique is required during glenoid exposure to prevent nerve injury.
• Avoiding extreme rotational positions and oversized implants can reduce the risk of stretch-induced neuropathies in RTSA.