DOS 2016

DOS Kongressen 2016 ·

239

The Critical Shoulder Angle is Associated with

Osteoarthritis in the Shoulder but not Rotator Cuff

Tears. A retrospective case control study

Arnar Oskar Bjarnison, Thomas Juul Sørensen, Thomas Kallemose, Kristoffer W.

Barfod

Department of Orthopedics, Zealand University Hospital; Department of

Orthopedics, Zealand University Hospital; Clinical Orthopaedic Research

Hvidovre, Copenhagen University Hospital Hvidovre ; Department of

Orthopedics, Zealand University Hospital

Background:

In 2013 Moor et al introduced the concept of the critical shoul-

der angle (CSA) and suggested that an abnormal CSA was a leading factor in de-

velopment of Rotator Cuff Tear (RCT) and Osteoarthritis of the shoulder (OA).

Purpose / Aim of Study:

The purpose of the study was to test if the CSA was

associated with RCT and OA. The study hypothesis being that people having a

CSA > 35° were at increased risk of developing RCT and people with a CSA <

30° were at increased risk of developing OA.

Materials and Methods:

The study was performed as a retrospective case-

control study following the STROBE guidelines. 97 patients with RCT and

87 patients with OA constituted the two groups of cases. The controls were

matched 3:1, by age and sex, from a population of 795 patients with humeral

fractures. The CSA was measured as described by Moor et al. in 2013. Sample

size calculation showed a need for 71 cases and 213 controls. Analysis of the

relation with CSA for RCT and OA was done by logistic regression. Models were

fitted separately for RCT and OA and used the controls matched to the respec-

tive cases.

Findings / Results:

The mean CSA in the RCT group was 33.9° and in the

matched control group 33.6°. The Odds Ratio for developing RCT for people

with a CSA above 35° was 1.12 (p=.63). The mean CSA in the OA group was

31.1° and in the matched control group 33.3°. The Odds Ratio for developing

OA for people with a CSA below 30° was 2.25 (p=.002).

Conclusions:

This study did not find any association between CSA and RCT but

did show association between CSA and OA with a 2.25 Odds Ratio of develop-

ing OA given the patient had a CSA below 30°. The results does not support

the suggested praxis of shaving away the lateral border of the acromion in order

to make the CSA smaller as it might increase the risk of developing OA without

decreasing the risk of developing RCT.

No conflicts of interest reported

190.