Weightbearing radiographs accurately predict deep deltoid ligament injury in Weber B ankle fractures - a minimally invasive arthroscopic evaluation.

BACKGROUND

Differentiating Weber B/SER4a from SER4b fractures relies on weightbearing radiographs and gravity stress tests, assumed to reflect deep posterior tibiotalar ligament (dPTTL) integrity. This study assessed their diagnostic accuracy for dPTTL injury, with arthroscopy as the reference standard.

METHODS

We prospectively assessed 20 Weber B/SER4a-b fractures with a medial clear space ≥ 5.0 mm. Arthroscopy under local anesthesia evaluated dPTTL integrity, defined as tensioning and medial joint space closure during dorsiflexion.

RESULTS

Radiographically, 15 fractures were classified as SER4a, and five as SER4b. Arthroscopy revealed intact dPTTL in 14 of 15 SER4a cases, while all SER4b cases had ruptures. Weightbearing radiographs showed 83.3% sensitivity and 100.0% specificity for detecting dPTTL injury; the gravity stress test had 100.0% sensitivity but 0.0% specificity.

CONCLUSIONS

Stable weightbearing radiographs reliably indicate dPTTL integrity, while instability suggests dPTTL rupture.

LEVEL OF EVIDENCE: Level II, Cross-sectional study.