Accuracy of Injection Into the First Dorsal Compartment: A Cadaveric Ultrasound Study.

Abstract

To determine the accuracy of ultrasound-guided (UG) injections compared with anatomic landmark-guided (AL) injections in the first dorsal compartment (FDC) with the hypothesis that ultrasound guidance would increase the accuracy of injection. We randomized 43 above-elbow cadaveric specimens to receive latex dye injections into the FDC via a UG or AL technique. If ultrasound imaging identified a septated FDC, the needle was redirected and a portion of the dye was injected around the extensor pollicis brevis (EPB) tendon. Specimens were dissected and data collected regarding the location of the dye and presence of a septated FDC. Fisher exact test was used to calculate the difference in accuracy rates of injections. All 21 specimens injected via UG and all 22 specimens injected via the AL technique demonstrated dye within the FDC. Eight of 21 specimens in the UG group and 6 of 22 specimens in the AL group demonstrated a septated FDC upon dissection. Ultrasound was able to identify 6 of 8 specimens accurately with a septated FDC, representing a sensitivity of 75% and specificity of 92%. Six of 8 specimens with a septated FDC in the UG group versus 2 of 6 specimens with a septated FDC in the AL group demonstrated dye infiltration around the EPB. Dye was noted in the subcutaneous tissues in 2 of 21 specimens in the UG group versus 2 of 22 specimens in the AL group. The UG- and AL-based injections both had excellent dye infiltration into a portion of the FDC. Ultrasound-guided injections had a higher observed infiltration rate in EPB subcompartments than the AL technique, but could not be statistically confirmed to be different. Ultrasound is unlikely to increase the accuracy of injections into an unseptated FDC. It may aid in injection of a septated FDC; however, that remains to be statistically demonstrated.