Deriving the East Riding Elbow Rule (ER2): a maximally sensitive decision tool for elbow injury

To derive a maximally sensitive decision rule for clinical practice to rule out the need for x-ray examination after elbow injury in adults and children.

Emergency department patients with acute elbow injury were recruited. Practitioners used their usual judgement to assess whether x-ray examination was required. Radiographs were reported on by radiologists blind to clinical assessment. Patients not x-rayed were followed-up at 7 days by telephone interview, and those with ongoing pain were recalled for assessment. Recursive partitioning was used to derive a maximally sensitive decision tool. Inter-rater variability for significant discriminators was subsequently evaluated by a cohort of 20 emergency department clinicians.

492 patients were recruited (May 2006-November 2008): 50.4% were male; 26.8% were children; 444 (90.2%) had an x-ray; 167 (37.6%) showed abnormality. A follow-up telephone interview was conducted with 28; none were recalled. Thirteen could not be contacted, none of whom returned within 3 months. Sixteen patients with fractures were able to fully extend their elbow. The sensitivity of elbow extension alone was 84% (95% CI 77% to 88%), with specificity of 54% (95% CI 53% to 58%). A 100% sensitive (95% CI 97% to 100%) decision rule for adults (n=348) was derived based on (1) inability to fully extend the elbow, (2) tenderness over radial head, olecranon or medial epicondyle, and (3) presence of bruising (specificity 24% (95% CI 19% to 30%)). A similar rule for children could not be derived.

A simple and highly sensitive clinical decision rule for adult elbow fracture was derived in our cohort. A validation study in a second population is now required. At present, we are unable to recommend a rule-out strategy for elbow injuries in children.