The Radial Synergy Test: An Aid to Diagnose de Quervain's Tenosynovitis.

BACKGROUND: Diagnosis of de Quervain's tenosynovitis is made clinically. Finkelstein's and Eichoff's tests are commonly utilized examination maneuvers. Their specificity has been questioned due to a propensity to provoke pain in asymptomatic patients. Using the principle of synergism, the novel radial synergy test takes advantage of isometric contraction of the first dorsal compartment with resisted abduction of the small finger.

METHODS: Electromyography was performed on 3 authors and the first dorsal compartment sampled during the maneuver. Sensitivity evaluation was performed via retrospective chart review for patients diagnosed with de Quervain's from 2013 to 2018. Inclusion criteria were documented radial synergy test, Eichoff's test, and ≥90% pain relief after lidocaine/corticosteroid injection. We enrolled 222 patients with 254 affected extremities. Specificity evaluation was performed via a prospective cohort of volunteers undergoing radial synergy and Eichoff's tests. Inclusion criterion was lack of preexisting wrist pain. Score > 0 on Visual Analog Scale was considered positive. We enrolled 48 volunteers with 93 tested extremities.

RESULTS: Electromyography revealed positive recruitment of the first dorsal compartment. Sensitivity of the radial synergy test was inferior to Eichoff's test (97% vs 91%, relative risk [RR] = 0.93 [95% confidence interval [CI] = 0.89-0.97], P < .01). Specificity of the radial synergy test was superior to Eichoff's test (99% vs 74%, RR = 1.33 [95% CI = 1.18-1.51], P < .001).

CONCLUSIONS: We describe and evaluate the radial synergy test, a novel examination maneuver to aid the diagnosis of de Quervain's. This serves as an adjunct for future diagnostic evaluations with its high specificity.

LEVEL OF EVIDENCE: Level II, diagnostic study.