Sensitivity and specificity of waterbath ultrasound technique in comparison to the conventional methods in diagnosing extremity fractures.

Introduction: Point of care ultrasound (POCUS) has variable diagnostic accuracy in diagnosing fractures. Waterbath technique is a modification of the conventional ultrasound technique which may improve diagnostic accuracy by enhancing image quality. Authors studied the diagnostic accuracy of waterbath technique compared to the final diagnosis based on clinical examination and radiology in the identification of fractures of hand and foot.

Methods: Patients of >18 yrs. age with suspected distal hand and foot fractures presenting to the emergency department of a level 1 trauma center were recruited after informed consent. Unconscious and hemodynamically unstable patients, injuries >72 h old, open fractures, obvious deformities, and old fractures at the affected site were excluded. Cases were subjected to waterbath technique performed by an academic emergency medicine resident and relevant radiographs were ordered and interpreted by an orthopedic specialist. CT/MRI, if done in case of discrepancy, was interpreted by radiologist. The findings of both waterbath technique and radiology were blinded to each other and compared to the final diagnosis made by a cumulative assessment of clinical examination, radiographs, and CT/MRI of the discrepant cases.

Results: Waterbath technique identified fractures of hand and foot with sensitivity of 97% (95% CI 90%-100%), specificity 94% (95%CI 81%-99%), PPV 98% (95%CI 91%-99%), NPV 94% (95%CI 79%-98%), LR+ 17.5(95% CI 4.5-67.2), LR- 0.03(95% CI 0.01-0.12) and diagnostic accuracy 96% (95%CI 91%-99%).

Conclusion: This pilot study has demonstrated the utility of Waterbath technique in the diagnosis of fractures of hand and foot in adults in the ED setting. Future well designed studies are required to explore the potential of this novel technique in both adult and pediatric population.