ECU Instability with Longitudinal Interfascicular Separation: Outcomes of Repair and Reconstruction with a Retrograde Posterior Interosseous Artery Fascial Flap.

INTRODUCTION: Unstable extensor carpi ulnaris (ECU) tendons with longitudinal interfascicular separation and loss of concentric integrity (LIS-Loci) are rare and not previously reported in the literature. Seven cases were identified in a retrospective study over a 4-year period.

METHODS: A retrospective study was performed on all patients who had surgery to stabilize the ECU tendon. The ECU tendon was repaired, and the ECU sheath was reconstructed with a retrograde posterior interosseous artery (PIA) "sliding" fascial flap.

RESULTS: When compared with preoperative measures, pronation and supination strength were significantly increased by 79.2% and 59.0%, respectively. Furthermore, there was a significant reduction in Disabilities of the Arm, Shoulder and Hand (DASH) scores (71.9%), Patient-Rated Wrist Evaluation (PRWE; 67.4%), and Visual Analog Pain Scale (VAS) score on use (70.2%). These injuries are part of a global injury to the wrist. Six cases had concurrent pathologies, including dorsal peripheral tear of the triangular fibrocartilage complex and scapholunate instability. Associated pathologies were repaired arthroscopically during the same procedure. Only one case had an isolated LIS-Loci. There were no recurrent instabilities or revisions.

DISCUSSION: LIS-Loci of the ECU tendon are rare conditions, and there have been no prior reports of this in the literature. This is the first description of the use of a retrograde PIA fascial fat flap to reconstruct the ECU sheath following longitudinal interfasciculation and loss of concentric integrity of the ECU tendon.

LEVEL OF EVIDENCE: Level III.