Determination of pre-arthropathy scapular anatomy with a statistical shape model – Part II: shoulder osteoarthritis.

Hypothesis and Background: Shoulder osteoarthritis can be divided in different glenoid types (A, B, C and D) and subtypes. The aim of this study was to investigate if there is an association between the pre-arthropathy scapular anatomy, shoulder osteoarthritis and different glenoid types and subtypes. Methods: Using principal component analysis, a statistical shape model (SSM) of the scapula was constructed from a dataset of 110 computed tomography (CT) scans. These subjects formed the control group. Next, CT scan images of 117 patients with osteoarthritis were classified according to the modified Walch classification. A complete three-dimensional (3D) scapular bone model was created for every patient, and using the SSM, a reconstruction of their pre-arthropathy scapular anatomy was performed. Automated 3D measurements were performed in both the patient and control group to obtain glenoid version and inclination, critical shoulder angle (CSA), posterior acromial slope (PAS), lateral acromion angle (LAA), scapular offset and the rotational alignment of the coracoacromial complex. These parameters were compared between controls, osteoarthritis patients, glenoid types and subtypes. Results: Mean version and inclination for the control group was 6° retroversion and 8° superior inclination (both SD ± 4°). The mean CSA, PAS, coracoid-posterior acromion angle, posterior acromion- scapular plane angle and fulcrum axis ratio was 30° (SD ± 4°), 64° (SD ± 8°), 116° (SD ± 9°), 55° (SD ± 7°) and 46% (SD ± 4%) respectively. Osteoarthritis patients had a significant lower CSA, posterior acromion-scapular plane angle, coracoid-posterior acromion angle and fulcrum axis ratio (27°, 50°, 111°, 44%, all P< 0.001). We found a significant difference between the control group and the respective glenoid types for the following parameters; mean CSA and coracoid-posterior acromion angle for A glenoids (27°, P= 0.001 and 111°, P=0.007), mean version, CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle and fulcrum axis ratio for B glenoids (11°, 27°, 71°, 111°, 49°, 43%, all P< 0.001), mean version, CSA and posterior acromion-scapular plane angle for D glenoids (2°, P= 0.002, 26°, P= 0.003 and 48°, P= 0.007). Discussion: There seems to be an association between pre-arthropathy scapular anatomy and shoulder osteoarthritis. A small lateral extension and less posterior rotation of the acromion is associated with shoulder osteoarthritis and is present in almost all types and subtypes of glenoid morphology. Furthermore, B and D glenoids are associated with a more and, respectively less pronounced pre-arthropathy glenoid retroversion. Keywords: shoulder osteoarthritis, glenoid types, scapular anatomy, SSM, glenoid version, CSA, PAS Level of evidence: III

Publication year:2021

BOF-keylabel:yes

IOF-keylabel:yes

BOF-publication weight:3

CSS-citation score:1

Authors from:Higher Education

Accessibility:Open