Fixed- vs. variable-angle humeral neck cut in anatomic total shoulder arthroplasty: a randomized controlled trial

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiographic Analysis

Background:

• Variable neck-shaft angle (NSA) components aim to replicate normal anatomy in total shoulder arthroplasty (TSA).
• Assessing whether fixed-NSA or variable-NSA prostheses better restore premorbid glenohumeral joint anatomy is crucial for implant design.

Purpose of the Study:

• To compare the radiographic restoration of premorbid glenohumeral joint anatomy using fixed-NSA versus variable-NSA prostheses in anatomic TSA.

Main Methods:

• A randomized controlled trial involved 50 patients undergoing primary anatomic TSA, randomized to fixed-NSA (n=24) or variable-NSA (n=26) groups.
• Preoperative and postoperative radiographs were analyzed for NSA, head thickness, tuberosity-to-head height, head offset, articular arc, greater tuberosity offset, and center of rotation (COR).

Main Results:

• Both groups showed superior migration of the center of rotation (COR) postoperatively.
• Humeral head offset decreased significantly in the fixed-NSA group and approached significance in the variable-NSA group.
• No significant differences were found between the fixed-NSA and variable-NSA groups in the net change of key anatomical parameters from premorbid measurements.

Conclusions:

• Both fixed-NSA and variable-NSA anatomic TSA humeral components effectively restore premorbid anatomy.
• Radiographic evaluation indicates comparable anatomical restoration between fixed and variable NSA prostheses in TSA.