VALIDATION DATA

Potential users of OSS should note that the questionnaire is probably not suitable for post-operative patients (i.e. those having surgery to correct their shoulder instability) until 6 months post-op, as one question asks ‘during the past 6 months’.

The OSS has acceptable internal consistency with numerous studies in varying populations, reporting Cronbach’s α of 0.89 or more.

Test-retest reliability is reported to be acceptable:

• Impingement with or without rotator cuff tear or calcific tendinitis: Pearson’s correlation = 0.98.
• Impingement: weighted κ = 0.13 for item 1; weighted κ values for other items = 0.44 to 0.79.
• Patients with shoulder pain/dysfunction after surgery for breast cancer (Spanish OSS): ICC = 0.974
•  Patients with nonspecific shoulder pain (Chinese OSS): ICC =0.97

An MDC of 3.15 points was reported in a study of Polish patients post rotator cuff surgery, whereas an MDC of 7.18 was reported in a study of Brazilian patients with degenerative or inflammatory shoulder conditions.

20 out-patients with shoulder problems were interviewed about their shoulder problems. Using interview transcripts and established questionnaires, a 22-item questionnaire was drafted and tested in interviews with 20 new patients. They also completed a second copy of the questionnaire inviting extra comments. The questionnaire was modified following piloting. The revised version was tested on two further groups of patients until its final form was established. This version contained 12 items, each of which has five response categories.

Factor analysis of the Persian OSS found a two-factor solution that explained 61.6% of the variance, which is consistent with the OSS being a two-dimensional outcome measure assessing pain and function. Principal component analysis of the Chinese OSS found a one-factor structure that accounted for 54.2% of the total variance.

EFA and CFA demonstrated that, in addition to single summary scales usage, separate information on pain and self-reported disability/function can be extracted in a meaningful way, as subscales, from the OSS: Dawson J, Harris KK, Doll H, Fitzpatrick R, Carr A. A comparison of the Oxford shoulder score and shoulder pain and disability index: factor structure in the context of a large randomized controlled trial. Patient Relat Outcome Meas. 2016;7:195-203.