Accuracy and Feasibility of Ultrasound-Guided Intra-articular Injection of the Rat Hip Joint.

Intra-articular injection is frequently used as an effective diagnostic and treatment tool for hip joint diseases. However, the underlying treatment mechanism remains unclear because of a lack of experimental animal models. A challenge facing researchers is how to accurately and consistently perform injections involving animal hip joints. The purpose of this study, then, was to establish an ultrasound (US)-guided intra-articular (IA) injection technique using rat hip joints and to evaluate its accuracy and feasibility versus a fluoroscopy (FL)-guided technique. For this study, 20 US-guided and 20 FL-guided IA injections were administered to separate groups of Sprague-Dawley rats. For each procedure, 50 µL of iohexol was injected into the hip joint using a 25G needle. The US-guided injections were performed using a linear probe, and the FL-guided IA injections were performed using C-arm X-ray fluoroscopy. All injections were verified by computed tomography imaging. The number of successful injections and needle repositions per injection, as well as operating times, were recorded, and the rats were observed for complications for 10 d after the injections. Statistical analysis was used to compare US-guided and FL-guided techniques with significance set at p < 0.05. The success rate was markedly higher for the US-guided interventions (90%) than for the FL-guided interventions (75%) (p<0.05). The intervention time was shorter in the US-guided group (95.95 ± 8.376 s) than in the FL-guided group (110.70 ± 20.236 s) (p < 0.05), and the median number of needles repositioned per injection in the US-guided group (1.20 ± 0.41) was notably less than that in the FL-guided group (1.60 ± 0.68) (p < 0.05). A puncture site hematoma was noted in two rat hips (10%) the day after injection in the FL-guided group. Overall, the study indicated that ultrasound-guided intra-articular injection of the hip is a feasible, accurate and safe method for use in rats. This makes it a promising tool for diagnosing coxofemoral pain, producing hip osteoarthritis animal models and administering intra-articular medication.