Humeral head sizing using extra-articular landmarks on conventional radiographs

Area of Science:

• Orthopedic surgery
• Radiology
• Biomechanical engineering

Background:

• Accurate humeral head (HH) sizing is essential for successful anatomic shoulder replacement in managing glenohumeral arthritis.
• Current templating methods may have limitations in precision and accessibility.

Purpose of the Study:

• To evaluate the accuracy and reliability of a novel three-point radiographic technique using non-articular landmarks for HH templating.
• To assess the precision of this method in predicting HH size and center of rotation (COR).

Main Methods:

• A basic science study involving five fresh adult cadaveric shoulders.
• Pre-operative and post-operative radiographs and 3-D CT scans were obtained.
• Measurements of HH size and COR were performed using articular surfaces and three extra-articular landmarks by two independent observers, twice each.

Main Results:

• The three-point method demonstrated excellent test-retest and inter-observer reliability (ICC > 0.996).
• The method predicted HH size within 1 mm of the implanted size, showing high accuracy.
• The calculated COR using this method was within 1.34 mm of the articular surface COR.

Conclusions:

• The three-point radiographic technique using extra-articular landmarks is a simple, cost-effective, and precise method for predicting HH size.
• This technique may be a valuable tool for HH templating in anatomic shoulder replacement, offering a small margin of error.