Midfoot fractures: Patterns of injury and predictors of stability.

Background: Lisfranc injuries describe a spectrum of midfoot and tarsometatarsal joint (TMTJ) trauma ranging from purely ligamentous to multiple fracture-dislocations. Lisfranc injuries represent 0.2 % of all fractures and are seen predictably, with mechanisms involving a fall from height, crushing, or torsion. Diagnosis can be challenging, with approximately 20 % of cases being missed, and relies upon clinical acumen and proficient image interpretation. Whilst multiple classification systems have described Lisfranc injuries using a 3-column concept, these add zero prognostic value and are therefore rarely used clinically. Furthermore, existing literature on diagnosis and management is limited to retrospective small series.

Methods: We present a review of 161 midfoot injuries, with the aim of highlighting characteristics of radiological instability and indication for operative management. CT scans and weight-bearing and non-weight-bearing X-rays were reviewed for features of joint instability. These features included metatarsal base, cuneiform and cuboid fractures, tarsometatarsal joint subluxation or dislocation and C1-MT2 diastasis. The subsequent "stable" and "unstable" injury groups were then compared to identify statistically significant indicators for instability.

Results: Avulsion and intra-articular fractures of the medial, middle, or lateral column were all suggestive of instability. Although these appeared in multiple combinations, 95 % involved the middle column. Concomitant inter-cuneiform and cuboid fractures were additional indicators of instability. In cases of uncertain midfoot instability, weight-bearing radiographs were of value with 14.2 % demonstrating a diastasis of C1-MT2 >2 mm.

Conclusion: We propose the need for a new classification of midfoot injuries which emphasises the diagnosis of instability and guides surgical management. We propose that, based on non-weight-bearing X-ray and CT scans, these injuries can be initially classified as "stable", "unstable", or "stability uncertain". Weight-bearing X-rays are a safe and reliable method of detecting instability in the "stability uncertain" group. Fractures of the medial column and cuneiform on initial imaging were suggestive of midfoot instability.