Reliability and Validity of the Hook Test for Diagnosis of Distal Biceps Tendon Ruptures.

PURPOSE: Although the initial description of the distal biceps tendon (DBT) hook test (HT) reported 100% sensitivity (Sn) and specificity (Sp), subsequent retrospective series have demonstrated imperfect validity. The purpose of this investigation was to prospectively assess the validity and reliability of the HT for complete DBT ruptures. We aimed to determine the Sn/Sp and interrater reliability for the HT.

METHODS: A consecutive series of adult patients presenting to our outpatient clinics with an elbow complaint was prospectively examined. Patients were included if they had undergone advanced imaging (magnetic resonance imaging or ultrasound) that imaged the DBT and underwent DBT repair. There were four participating surgeons, all of whom were blinded to magnetic resonance imaging/ultrasound prior to performing the HT. To determine the Sn/Sp of the HT and advanced imaging, intraoperative findings served as the primary reference standard. The interrater reliability of the HT was calculated for cases in which a primary examiner (surgeon) and secondary examiner (physician assistant or resident) performed the HT.

RESULTS: Of 64 patients who had undergone advanced imaging, 28 (44%) underwent DBT surgery and were included in the assessment of Sn/Sp. The mean age was 49 years, and all patients were men. The Sn and Sp of the HT were 96% and 67%, respectively. Advanced imaging demonstrated 100% Sn and Sp. Twenty-five patients were evaluated by a primary and secondary examiner. The interrater reliability was substantial (Cohen kappa, 0.71).

CONCLUSIONS: The Sn and Sp of the HT were 96% and 67%, respectively, when assessed prospectively. Advanced imaging findings (magnetic resonance imaging/ultrasound) demonstrated 100% Sn and Sp. The HT can be performed reliably by examiners with varying experience levels. Considering the imperfect validity of the HT, we caution against the use of this examination alone to diagnose DBT ruptures.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.