Glenoid neck length in a healthy population and its association with scapular notching.

BACKGROUND

Scapular notching is a radiographic finding associated with the use of a reverse shoulder prosthesis. The morphological characteristics of the glenoid neck have been scarcely explored as a relevant factor in relation to scapular notching. The objective of this study is to measure the length of the glenoid neck in a three-dimensional CT reconstruction of a healthy population and to simulate the scapular notching free range of motion for the "long neck" and for the "short neck" groups.

METHODS

CT scans of 214 shoulders were reviewed, excluding incomplete, poor quality, or altered studies. 100 CT scans were finally processed. The mean age was 51.7 years (SD 19.4; range, 15-84 years), with 49 female and 51 male patients. For each of the scapulae, four morphometric measurements were obtained: anterior glenoid neck (AGN), middle glenoid neck (MGN), posterior glenoid neck (PGN) and alternative posterior glenoid neck (aPGN). Using 3D software, we simulated a reverse shoulder prosthesis, and the scapular notching free range of motion was registered. Differences between measurements were evaluated with an unpaired t-test using StataIC16®. P-values < 0.05 were considered significant. The intraobserver and interobserver correlation was evaluated with the intraclass correlation coefficient.

RESULTS

The AGN measured 7.43 ± 2.52 mm (range, 1.72-13.3 mm); MGN measured 8.05 mm ± 1.93 (range, 2.92-13.2 mm); PGN measured 7.26 ± 2.6 mm (range, 2-13.4 mm); and aPGN measured 8.97 ± 2.3 mm (range, 4.08-15.4 mm). The scapular notching free range of motion for the "long neck" group was 74.98° ± 7.35 (range, 55-83°) and for the "short neck" group, it was 62.93° ± 6.84 (range, 45-70°) (p = 0.0004).

CONCLUSIONS

Measurement of posterior glenoid neck length exhibits excellent reliability and reproducibility, as well as being associated to the scapular notching free range of motion.

STUDY

DESIGN

Basic, retrospective, CT images research.