Learning curves of two different techniques for the intra-articular injection of the knee joint under fluoroscopic guidance.

Aim: The aim of the study was to compare the learning curves of three beginner operators using two different techniques of intra-articular injection of the knee under fluoroscopic guidance with a superolateral approach.

Materials And Methods: In total, 177 consecutive patients (72 females (40.7%) and 105 males (59.3%), mean age 42.2 ± 15.0 years) scheduled for a computed tomography (CT) arthrography and without joint effusion on the lateral X-rays were enrolled. They underwent an intra-articular injection of the knee under fluoroscopic guidance with a superolateral approach. Patients were randomly assigned to three different operators, including a junior supervisor and two first-year residents in radiology who never performed an intra-articular injection of the knee before the present study. Procedures in lateral or supine position were randomly assigned to three operators.

Results: There was a higher rate of successful injections with the lateral position (92.1%) than with supine position (80.2%) (odds ratio (OR) 4.52, 95% confidence interval (CI) 1.46-14.0). A significant learning effect was observed for the supine position, while none was observed for the lateral position. Pain and time of fluoroscopy did not differ between the two procedures (p = 0.85 and p = 0.10, respectively). Junior supervisor had a higher rate of successful intra-articular injection compared with the other two operators (p = 0.0072). There was a statistically significant higher rate of extravasation with the supine position (66.3%) than with lateral position (19.7%) (p < 0.0001, OR 0.13, 95% CI 0.06-0.25).

Conclusion: The intra-articular injection of the knee under fluoroscopic guidance with the patient in lateral position is an easy technique for operators in training with a low rate of extravasation. Lateral position does not require a supplementary irradiation and does not increase the procedural pain. Personal operator's skill is an independent factor in determining the success of the training.