The ECU synergy test: an aid to diagnose ECU tendonitis

Chronic dorsal ulnar-sided wrist pain challenges even the most experienced physicians. The close anatomic proximity and the possibility of coexistent injuries can render physical examination maneuvers ambiguous, making it difficult to discern between intra-articular and extra-articular pathology. Using the principle of synergism, we describe the extensor carpi ulnaris (ECU) synergy test as a novel means for diagnosing ECU tendonitis and document its benefit in the clinical setting.

A retrospective chart review was performed, identifying adult patients experiencing greater than 4 months of dorsal ulnar-sided wrist pain. Physical examination findings, results of magnetic resonance imaging (MRI) and/or wrist arthroscopy, and clinical outcomes were compiled.

Fifty-five patients met inclusion criteria. Twenty-one patients (group 1) had no pain with the synergy test but had exams suggesting ulnar-sided intra-articular pathology. All had ulnar-sided intra-articular pathology on MRI and/or arthroscopy. Eleven patients (group 2) had positive synergy tests and no pain with the remainder of the exam. All had greater than 90% pain relief after ECU tendon sheath injection; 5 patients remained pain free. Six patients experienced temporary improvement and had MRI evaluation, confirming the diagnosis of isolated ECU tendonitis in 5 of the 6 patients. The remaining 22 patients (group 3) had positive synergy tests and exams that suggested concomitant ulnar-sided intra-articular pathology. After ECU sheath injection, 5 patients had persistent discomfort with either lunotriquetral ballottement or triangular fibrocartilage complex compression. All 5 patients had ulnar-sided intra-articular pathology confirmed by MRI and/or arthroscopy. Seventeen patients had greater than 90% pain relief after injection. Of these, 7 patients remained asymptomatic at latest follow-up, confirming the diagnosis of ECU tendonitis. Ten patients had recurrent symptoms, of which 6 patients demonstrated ulnocarpal pathology by MRI and/or wrist arthroscopy.

By differentiating between intra-articular and extra-articular pathology, the ECU synergy test composes part of a clinical algorithm that minimizes the need for wrist MRI and diagnostic arthroscopy.

Diagnostic II.