Temporomandibular joint injections: interventional MR imaging demonstrates anatomical landmark approach to be inaccurate when compared to direct visualization of the injectant

Abstract

Sir, We read with interest the article from Dr. Parra and colleagues [1] published online 2010 March 4. The authors are to be congratulated on their efforts in the development of an imaging guidance technique with the intention to reduce the use of ionizing radiation in children [2]. However, the authors’ routine use of CT of the temporomandibular joints following needle placement exposes children to ionizing radiation and makes their technique less desirable than US alone or interventional MRI. Not least for this fact, the authors discuss interventional MRI as a co-existing technique for temporomandibular joint injections in children. We were, however, surprised about the omission of the citation reporting the technique of real-time MRI guidance for intra-articular injections of the temporomandibular joints resulting in an overall technical accuracy of 100%. We, therefore, wish to provide this necessary reference to the readers of Pediatric Radiology [3]. Dr. Parra and colleagues claim to have assessed the accuracy of US-guided injections “into the intra-articular compartment of the TMJ” [1]. This, however, requires visualization of the injectant for documentation of location and distribution of the delivered drug, which was not performed. Instead, successful or failed intra-articular injection was estimated by visualization of the needle tip on CT images obtained following US-guided needle placement by using an anatomical landmark approach. Injections were performed afterward, which leaves the rate of successful intra-articular drug delivery undetermined. This is of importance, because in our experience the landmark approach is inaccurate and results in a paraarticular location of the needle tip in up to 18% of targeted synovial compartments [3]. These published data were obtained by direct visualization of injections, which were performed after imaging verification of the needle tip in seemingly adequate location when using anatomical landmarks. Figure 1 illustrates a typical case. The authors’ data on US-guided injections of the temporomandibular joints provide evidence of the feasibility of needle guidance; however, no data providing conclusive evidence of the accuracy of US-guided injections into the intra-articular compartment of the TMJ were obtained. The authors wish to provide “reassurance of the accuracy” of their US method; however, we respectfully submit that the conclusion that this technique represents an accurate method is speculative and not firmly supported by their data. Electronic supplementary material The online version of this article (doi:10.1007/s00247-010-1836-y) contains supplementary material, which is available to authorized users. J. Fritz (*) : J. S. Lewin Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Baltimore, MD 21287, USA e-mail: jfritz9@jhmi.edu