High inter-rater reliability, agreement, and convergent validity of Constant score in patients with clavicle fractures.
BACKGROUND
The Constant score (CS) has been the primary endpoint in most studies on clavicle fractures. However, the CS was not developed to assess patients with clavicle fractures. Our aim was to examine inter-rater reliability and agreement of the CS in patients with clavicle fractures. The secondary aim was to estimate the correlation between the CS and the Disabilities of the Arm, Shoulder and Hand score and the internal consistency of the 2 scores.


METHODS
On the basis of sample sizing, 36 patients (31 male and 5 female patients; mean age, 41.3 years) with clavicle fractures underwent standardized CS assessment at a mean of 6.8 weeks (SD, 1.0 weeks) after injury. Reliability and agreement of the CS were determined by 2 raters. The interclass correlation coefficient (ICC2,1), standard error of measurement, minimal detectable change, Cronbach α coefficient, and Pearson correlation coefficient were estimated.


RESULTS
Inter-rater reliability of the total CS was excellent (interclass correlation coefficient, 0.94; 95% confidence interval, 0.88-0.97), with no systematic difference between the 2 raters (P = .75). The standard error of measurement (measurement error at the group level) was 4.9, whereas the minimal detectable change (smallest change needed to indicate a real change for an individual) was 13.6 CS points. The internal consistency of the 10 CS items was good, with a Cronbach α of .85, and we found a strong correlation (r = -0.92) between the CS and Disabilities of the Arm, Shoulder and Hand score.


CONCLUSIONS
The CS was found to be reliable for assessing patients with clavicle fractures, especially at the group level. With high inter-rater reliability and agreement, in addition to good internal consistency, the standardized CS used in this study can be used for comparison of results from different settings.
Department of Orthopedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark. Electronic address: Ilija.ban@gmail.com.
Ilija
I
Ban
Department of Orthopedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark.
Anders
A
Troelsen
Physical Medicine and Rehabilitation Research-Copenhagen, Department of Physical Therapy, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark.
Morten Tange
MT
Kristensen
D000328:Adult; D002968:Clavicle / Q000293:injuries* / Q000601:surgery*; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D050723:Fractures, Bone / Q000145:classification / Q000601:surgery*; D006801:Humans; D008297:Male; D053580:Muscle Strength; D063868:Patient Outcome Assessment; D011446:Prospective Studies; D015203:Reproducibility of Results; D064232:Visual Analog Scale
Constant score; Inter-rater reliability; agreement; clavicle fractures; convergent validity; internal consistency