Comparison of diagnostic accuracy of point-of-care ultrasonography and X-ray of bony injuries of the knee

Abstract

Purpose: We aimed to compare the accuracy of point-of-care ultrasonography (POCUS) and X-ray (XR) in the diagnosis of knee bone fractures and fracture characteristics in cases of injuries to the knee.

Methods: The study was conducted in the emergency department (ED) of a tertiary hospital between March 2017 and March 2019. It included patients who presented to the ED with isolated knee injuries, were suspected to have a bony lesion based on clinical examinations, and were ultimately referred for XR. Five emergency physicians (EPs) who had at least three years of ED experience participated in the study. Before the study, these EPs received training on knee examination and radiographic investigation of the knee joint. They were also trained on how to assess the knee joint using POCUS. The knee bones, patella, femur, tibia, and fibula were evaluated. A POCUS examination of the knee bones was carried out according to the eight-step Kozaci Protocol.

Results: This study included 92 patients with knee trauma. The mean age of the patients was 34 ± 16 years (6-55 years). Using POCUS and XR, fractures were detected in 40 (43%) and 32 patients (35%), respectively. Relative to XR, for detecting fractures, POCUS showed sensitivity, specificity, positive predictive value, and negative predictive value of 97%, 85%, 78%, 98%, respectively, and the kappa value was 0.774. POCUS examination revealed hematoma and edema in the soft tissue in 34 (37%) patients and hemarthrosis in 33 patients (36%).

Conclusion: XR is the first and most widely used imaging modality to identify fractures of the knee bone trauma. However, POCUS examination can successfully diagnose bony lesions of the knee in patients with stable vital signs and without life-threatening injuries. It can also easily diagnose hematoma and hemarthrosis. Therefore, POCUS can be used as a diagnostic tool in emergency situations where XR is not available.

Keywords: Diagnosis; Emergency department; Fracture; Knee injury; Point-of-care ultrasound; Soft tissue POCUS; X-ray.