Placement of intra-articular injection verified by the backflow technique.

OBJECTIVE: To develop and to assess a simple, inexpensive method for ascertaining, without any imaging procedure, the intra-articular placement of the needle in the knee for intra-articular injections.
METHODS: Outpatients referred for intra-articular treatment with "dry" symptomatic knee osteoarthritis were included in this prospective study. "Dry" knee disease was defined as a knee without any clinically detectable effusion. Once intra-articular positioning of the needle considered adequate using the backflow technique, contrast solution was injected using the same needle without changing its position and immediately afterwards lateral and anterior-posterior X-rays were taken to assess the needle position.
RESULTS: Of the 32 of 33 cases with obtained backflow, the needle was correctly placed in all cases. In the remaining case, the needle was extra-articularly positioned. The concordance between the two techniques using the Cohen's Kappa was 1 [CI 95%: 0.22-1].
CONCLUSION: The backflow technique allows to accurate the intra-articular placement of the needle for "dry" knee joints injection. This technique can be proposed as a learning tool as well as a daily practice technique to ascertaining intra-articular knee injections without using fluoroscopy with injection of contrast material. Further studies are needed to assess the technique for other joint injections.