The patellar pubic percussion test: a simple bedside tool for suspected occult hip fractures

Purpose Patellar finger tapping produces a typical sound that can be detected by a stethoscope positioned on the pubic bone (patellar pubic percussion test (PPPT)). Characteristics of this sound are determined by continuity of bone between patella and pelvis. We hypothesized that a PPPT was able to detect overt hip fractures and occult hip fractures that may not be determined by a standard radiological examination. Methods Two independent observers performed a PPPT in patients with a suspected hip or pelvic fracture, just before a conventional radiograph (X-ray) was performed. The PPPT test was scored as negative (similar to contralateral side) or positive (different). Patients with a positive PPPT but with a negative X-ray underwent an additional CT scan. Results One hundred and ninety-one patients with suspected hip or pelvic fracture were included. A total of 161 patients (84%) were diagnosed with a fracture (hip, n = 142; pelvic, n = 19). An 85% sensitivity, a 70% specificity, a 0.94 positive predictive value, and a 0.47 negative predictive value of the PTTT were calculated. The inter-observer reliability (kappa) was 0.7. Eleven CT scans as indicated by a mismatch between PPPT (positive) and X-ray (no fracture) identified eight fractures (73%). A multivariate analysis demonstrated that a painful passive movement and the PPPT predicted a hip fracture. Conclusion The PPPT is a simple bedside diagnostic tool that is sensitive in detecting clinically straight forward hip fractures as well as occult hip fractures. The PPPT can support decision-making for additional radiological examinations in case of potential occult pelvis or hip fractures.