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

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.

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.

Cohort study; Level of evidence, 2.

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).

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: R² = 0.893; biplane: R² = 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.

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.