Reply

Abstract

We read Drs. Villaseñor-Ovies and Canoso's comments with interest. They make an interesting argument for the important role of the nondominant hand in performing joint injection. However, their interpretation of our study and their subsequent hypothesis that we introduced a bias by restricting use of the nondominant hand is incorrect, as it is based on an erroneous assumption.The sham ultrasound was not performed by the same doctor who was performing the CE-guided injection, but rather was performed by a third party holding an ultrasound probe near the injection site. The system was turned off and the screen was not visible to the patient. As the patients had no previous experience of an ultrasound-guided injection, they would have been blinded with regard to the technique used.The CE-guided injectors were allowed to practice their normal injection technique without any restraint and with the full use of both hands. In fact, they may have had an advantage, rather than a disadvantage, over standard injection technique. For purposes of localizing the injectate on a plain radiograph, the joint was injected with a much larger volume (6 ml for the knee, 4 ml for all other joints) than is usual in rheumatology practice. In smaller joints, such as the wrist and ankle, this may have led to an increased likelihood of some of the injectate reaching the joint cavity, thus being one of the causes of our CE-guided injectors' having a better accuracy rate than those published in other studies (1,2).To establish how well the blinding had worked, patients were asked during followup to report which method of guidance they thought they had received. Of these patients, 13.8% were unsure as to how the injection was guided, 70% thought they had received an ultrasound-guided injection, and 16% thought they had received a CE-guided injection. The agreement by kappa statistic between the actual method of guiding the injection and the method the patient thought they had received was 0.19, indicating poor agreement and confirming that the strategy used to blind patients to the method of guidance was successful.Despite CE-guided injections being performed using the clinician's usual technique and using a large injectate volume, ultrasound-guided injection by a much less experienced rheumatologist (9 months of rheumatology experience) had an accuracy rate of 83%, while CE-guided injections by more experienced rheumatologists (9 consultants with a median of 15.0 years of rheumatology experience [range 9-33 years] and 9 specialist registrars with a median of 3.0 years of rheumatology experience [range 1-8 years]) had an accuracy rate of 66% (a statistically significant difference). Experienced ultrasonographers can obtain close to 100% accuracy with real-time guidance (3), while experienced clinicians can, at best, achieve 66% accuracy using the 2-hand clinically guided technique.