Fermin Suarez MS4
The Article: Berona, K., Abdi, A., Menchine, M., Mailhot, T., Kang, T., Seif, D., & Chilstrom, M. (2017). Success of ultrasound-guided versus landmark-guided arthrocentesis of hip, ankle, and wrist in a cadaver model. The American Journal of Emergency Medicine,35(2), 240-244. doi:10.1016/j.ajem.2016.10.056
The Idea: Joint arthrocentesis is an important procedure in an emergency medicine setting. While it is an important procedure used to diagnose and treat certain joint conditions, the procedure may be technically challenging in small and deep joints. Rheumatology literature has shown that utilizing ultrasound improved the accuracy in joint injections versus landmark guided joint injections. One study published in emergency medicine literature has shown that ultrasound guided joint aspiration improved the success rate compared to landmark guided techniques while another study comparing the success rate between ultrasound and landmark techniques in knee arthrocentesis showed no significant difference between the two. This study looked at the accuracy of diagnosing effusions in the hip, ankle, and wrist by emergency medicine residents, compared the success rate between ultrasound and landmark arthrocentesis in a cadaver model, and looked at the change in confidence levels in emergency medicine residents’ ability to diagnose an effusion and perform an arthrocentesis after undergoing a didactic session and cadaver lab practicum.
The Study: This was a prospective, non-blinded study using emergency medicine residents and a cadaver model. PGYs 1-4 were eligible to participate in the study if they completed both the didactic portion of the training program and the cadaver lab practicum. Nine study sessions were held with one cadaver and three residents per session. Cadavers were prepared by the study investigators, all of whom were ultrasound fellowship trained. Saline was injected into each joint using ultrasound guidance until an effusion was detected. Laterality of each effusion was randomized using a computer randomizer except in cases where the cadaver had open joints from surgical procedures. Study investigators used ultrasound to confirm only one side had an effusion and that the saline fluid was only present inside the joint. Investigators also made multiple superficial needle punctures in the joint bilaterally so residents could not use the needle puncture mark made when injecting saline in the joint during cadaver preparation. Prior to the cadaver lab, residents watched a 30-minute instructional video on how to diagnose joint effusions and how to perform arthrocentesis using ultrasound and landmark guidance. In the cadaver lab, residents were asked to identify if each joint had an effusion present or absent. After confirming an effusion was present in a joint, residents then performed either an ultrasound guided arthrocentesis or a landmark guided arthrocentesis. Residents performed both techniques on the joint, but which technique used first was randomized.
Outcome measures of the study:
sensitivity and specificity of ultrasound for diagnosis of joint effusion
whether the subject successfully aspirated joint fluid (defined as >1 mL of fluid aspirated) from joints with confirmed effusion
number of attempts to success (attempt defined as needle withdrawal from skin and reinsertion)
time to aspiration (defined as time from insertion of needle into skin to successful aspiration), subjects were given a maximum time of 5 minutes to perform a successful aspiration
Confidence before and after the session was recorded using a five-point scale (1 = strongly disagree and 5 = strongly agree) in response to statements such as “I am comfortable identifying a joint effusion using ultrasound for (hip/ankle/wrist)”
The Results: The final study results included 18 total subjects (3 PGY 1, 11 PGY 2, 3 PGY 3, and 1 PGY 4). The group of subjects had performed an average of 161 ultrasounds each. In total, the group had completed 2 hip, 9 ankle, and 3 wrist arthrocentesis. Due to cadaver limitations such as fluid leaking out of the joint, residents did not scan every joint to identify an effusion and did not attempt an arthrocentesis on every joint. A total of 101 joints were scanned (35 hips, 35 ankles, and 31 wrists) and a total of 50 joints had an effusion (18 hips, 18 ankles, and 14 wrists). The sensitivity and specificity in identifying the presence of absence of a joint effusion for all joints was 86% and 90%. Success rates for ultrasound and landmark guided arthrocentesis were 96% and 89% respectively and the difference was not statistically significant. Success rates were broken by joint but the difference in success was not significant for any joint. None of the outcome measures of the study had a statistically significant difference. There was a statistically significant increase in resident confidence in identifying a joint effusion with ultrasound after training and in performing both ultrasound arthrocentesis and landmark guided arthrocentesis.
The Takeaway: Due to the small sample size of eligible participants, it would have been difficult to see a statistically significant increase in success rates using ultrasound in performing an arthrocentesis. The study does provide an estimate on how many participants would be needed to detect a significant difference in success rates between the two methods using the success rates obtained in the study, but whether that size of a study is feasible is unclear. The study mentioned how using a cadaver model may have inflated the success rate of landmark guided arthrocentesis due to lack of concern for patient safety and discomfort. The one significant difference that was obtained in this study was the increase in resident confidence in identifying joint effusion using ultrasound and confidence in performing both ultrasound and land mark guided arthrocentesis but the study was not set up to evaluate for skill retention. Overall, this study showed how effective a formal didactic and cadaver session was in helping to teach a valuable and necessary emergency department procedure and it demonstrated how large the study size must be in order to detect a significant increase in success rates using ultrasound to perform arthrocentesis.