An assessment of proximal humerus density with reference to stemless implants.

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Radiology

Background:

• Advancements in shoulder arthroplasty include stemless humeral components relying on trabecular bone fixation.
• Understanding regional bone density variations in the proximal humerus is crucial for optimizing stemless implant design.

Purpose of the Study:

• To map the regional variations in bone density within the proximal humerus using computed tomography (CT) scans.
• To provide data for the development of improved stemless humeral implant fixation strategies.

Main Methods:

• CT scans from 98 subjects were analyzed.
• The proximal humerus trabecular-canal was divided into 13 slices and 5 subsections (central, anterior, posterior, medial, lateral).
• Average apparent bone density (ρAVG) was quantified in each subsection.

Main Results:

• Bone density varied significantly with slice depth, subsection, and gender, with interactions involving osteoarthritic condition.
• Densities were highest in slices closest to the resection plane and decreased distally.
• The central subsection showed lower density than peripheral sections; the medial subsection was densest.
• Male subjects exhibited significantly higher bone density than female subjects.

Conclusions:

• The apparent bone density of the proximal humerus' trabecular-canal is not uniform.
• Stemless implant designs targeting higher density bone should utilize peripheral regions within the first 15-20 mm below the humeral head resection plane.