Purpose: Complete distal biceps tendon ruptures (DBTRs) require prompt surgical management for optimal functional and aesthetic outcome. Waiting for confirmatory diagnostic imaging can often delay timely surgical referral of these injuries. The need exists for a valid and reliable diagnostic tool to expedite appropriate referrals for surgery.

Method: Based on the hypothesis that complete distal biceps tendon rupture leads to an objectively measurable increase in the “biceps crease interval” (BCI) due to proximal retraction of the musculotendinous complex, three independent examiners established “normal” biceps crease intervals (N-BCI) for 80 males (average age = 43 years) with no history of biceps injury. Given acceptable inter-rater reliability (ICC > 0.70), a mean N-BCI value was established and a normal biceps crease ratio (N-BCR) between right and left arms was calculated. Correlations with arm dominance, biceps circumference, and age were determined. Diagnostic N-BCI and N-BCR thresholds were applied to 23 consecutive patients presenting with a possible complete DBTR to determine the diagnostic value of the BCI Test. A definitive diagnosis was confirmed at surgery and/or by radiographic imaging.

Results: The BCI Test had acceptable inter-rater reliability (ICC= 0.794, p = < 0.001). The mean N-BCI for both dominant and non-dominant arms was 4.8 +/− 0.6 cm. The mean N-BCR was 1.0 +/− 0.1. Applied to an injured population, using a diagnostic threshold of two standard deviations above “normal” values (BCI > 6.0 cm, BCR > 1.2), the BCI Test had a sensitivity of 92% and a diagnostic accuracy of 93%.

Conclusion: The BCI Test is an objective, valid and reliable test that can be used by clinicians to facilitate rapid diagnosis and surgical referral of suspected complete DBTRs.