Real-Time Biplane Versus Single-Plane US-guided Hip Joint Injection: A Single-Center Prospective Study

Background: Ultrasound (US)-guided hip joint injection is a cornerstone of musculoskeletal care, but conventional single-plane US presents a steep learning curve for novice operators. Real-time biplane US, which provides orthogonal imaging planes, may improve procedural accuracy and efficiency, yet its utility in hip injection remains understudied. Purpose: To compare procedural performance and learning curves between conventional single-plane US and real-time biplane US for hip joint injection, particularly in novice operators. Study Design: Cohort study; Level of evidence, 2. Methods: This prospective single-center study enrolled 70 consecutive patients (July 2024-December 2024) scheduled for US-guided hip injection, nonrandomly assigned to single-plane US (n = 35) or biplane US (n = 35) groups. All procedures were performed by a radiologist with 7 years of diagnostic US experience, limited previous US-guided interventional exposure, and no experience in hip joint injection. Primary outcomes were first-attempt success (successful intra-articular access and injection on the initial insertion without needle withdrawal or redirection) and final success (successful completion within no more than 2 insertion attempts). Secondary outcomes included puncture time, needle adjustments, operator confidence score, and complication. Learning curves were analyzed using cumulative sum (CUSUM) modeling for puncture time (seconds). Results: Compared with the single-plane group, the biplane group had significantly higher first-attempt success rate (48.6% vs 25.7%; relative risk [RR], 1.889 [95% CI, 1.103-3.648]; P = .048) and final success rate (91.4% vs 71.4%; RR, 1.280 [95% CI, 1.014-1.616]; P = .031). The biplane group also had shorter puncture time (median, 120 [interquartile range, IQR, 64-182] vs 153 [90- 234] seconds; P = .020), fewer needle adjustments (median, 1 [IQR, 0-2] vs 2 [0-3]; P = .008), and higher operator confidence score (median, 2 [IQR, 1-3] vs 1 [1-2]; P = .043). One minor complication occurred in the single-plane group. CUSUM analysis demonstrated cubic learning curves for both techniques (single-plane: R 2 = 0.893; biplane: R 2 = 0.979; both P < .05). Phase-specific analysis further showed that the advantage of biplane guidance was most pronounced during the learning phase, while shorter puncture time persisted after proficiency was achieved. Conclusion: In novice operators, real-time biplane US guidance was associated with higher procedural success, fewer needle adjustments, shorter puncture time, and faster early skill acquisition than conventional single-plane US for hip joint injection. Its greatest benefit was observed during the learning phase, although multicenter studies are needed to confirm generalizability.