The Displaced Fleck Sign: Description of a Radiographic Finding Consistent with Grade III Thumb Ulnar Collateral...

Controversy exists regarding the optimal imaging modality (magnetic resonance imaging, ultrasound, stress radiographs) for identification of patients with grossly unstable thumb metacarpophalangeal (MCP) ulnar collateral ligament (UCL) injuries or Stener lesions. We characterize a radiographic sign for this purpose. The "displaced fleck sign" is a small avulsion fracture from the ulnar proximal phalanx base that is displaced proximal to the MCP joint line.

Patients with thumb UCL injuries evaluated by hand surgeons were identified at a single, tertiary institution. Patients who were skeletally immature, had chronic injuries (>3 months old), and those with MCP arthritis were excluded. Two attending hand surgeons independently reviewed radiographs to identify the displaced fleck sign. Presence/absence of a Stener lesion was extracted from operative notes.

Of 228 patients, 17 (7.5%) had a positive displaced fleck sign. Excellent interobserver reliability was observed (κ = 0.94). All 17 (100%) demonstrated gross instability with no end point in clinic, and all underwent surgical repair. Grade III ruptures were noted for all. Specifically, 14 (94.1%) had a Stener lesion, and one patient (7%) had a bony avulsion from the metacarpal. The displaced fleck sign had a positive predictive value of 100% for Grade III rupture and 94.1% for a Stener lesion.

Presence of a displaced fleck sign has implications for offering surgery to patients with thumb UCL injuries because of a high likelihood of a Stener lesion. When present, surgeons may consider proceeding with surgical repair without additional imaging and associated follow-up visits.

Prognosis IV.