Supination-external rotation ankle fractures: stability a key issue

Abstract

Stability is a key issue in treating supination-external rotation ankle fractures, but we do not know how it affects functional outcome and subsequent development of radiographic osteoarthritis. With a systematic literature review, we identified 11 clinical studies (Level IV evidence) published in peer-reviewed journals reporting on at least 10 ankles. Followup was at least 1 year. Two authors independently scored the quality of the studies using the modified Coleman Methodology Score; the mean score was 58 of 100, with substantial agreement between the two examiners. Four studies used a general health assessment questionnaire. Several literature limitations (debatable fracture stability criteria, few cohort studies with heterogeneous methodology, small patient numbers and limited followup in some studies) do not allow definitive conclusions. Of 213 stable fractures treated nonoperatively, 2.8% of ankles had radiographic osteoarthritis develop (18 years' mean followup) and 84% were free of symptoms. The incidence of radiographic osteoarthritis in 420 unstable fractures treated operatively was 20.9% at 5.5 years versus 65.5% at 6.8 years in 137 ankles treated nonoperatively. The complication rate in 355 operatively treated fractures was 10.4%. A medial malleolus fracture, female gender, older age, higher American Society of Anesthesiologists grade, smoking, and lower educational level negatively influenced general health outcome, physical function, and pain.

Level of evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

Initially, the anterior tibiofibular ligament fails (1) (Stage I) and then an oblique fracture of the fibula starting at the level of the ankle and passing posteriorly occurs (2) (Stage II; Lauge-Hansen [22]). This may remain nondisplaced or minimally displaced if the deforming force stops at this point and the mortise remains stable. This is the most common type of fracture, classified as supination-external rotation II (SER-II). Progression of the deforming force (talar rotation) causes posterior and proximal displacement of the fibular fracture. Further talar rotation results in a fracture of the posterior articular lip of the tibia (3) (Stage III), and as the talus leaves the mortise posteriorly, a medial injury occurs (4) (Stage IV) at the deltoid ligament (white arrow) or at the medial malleolus (black arrow).

Fig. 2A–B

(A) Anteroposterior and (B) lateral radiographs show an isolated distal fibula fracture with markedly increased medial joint space (between the talus and medial malleolus) indicative of failure of the deep deltoid ligament and fracture instability.

Fig. 3

The distribution of quality of the studies according to the CMS throughout the last three decades.

Fig. 4A–B

(A) A radiograph shows an isolated lateral malleolus fracture. Is it a stable injury or not? (B) A gravity stress radiograph shows a medial clear space opening greater than 5 mm and is indicative of an unstable fracture pattern.