The role of pre-operative computed tomography in operative planning for ankle fractures involving the posterior malleolus

E. Harris, S. Bennet, P.W. Robinson, S.R. Mitchell, M. Jackson, J.A. Livingstone

Background: CT scans are increasing being utilised in preoperative planning to delineate the exact morphology of posterior malleolar fractures. We examined the influence of CT scans on patient positioning, surgical approach and method of fixation in posterior malleolar ankle fractures.

Methods: A retrospective analysis of 121 primary ankle fractures involving the posterior malleolus presenting to a University Teaching Hospital were identified between January 2012 and December 2014. Fracture morphology was assessed with the Haraguchi classification for all cases undergoing CT. Differences in patient positioning, surgical approach and method of fixation were compared between posterolateral oblique and medial extension type posterior malleolar fractures. Statistical analysis was performed with the chi-square test.

Results: 88 ankle fractures involving the posterior malleolus received a CT scan. 51 (58%) had a type 1: posterolateral oblique injury, 32 (36%) a type II: medial extension injury, and 5 (6%) a type III: shell type injury. A lateral or sloppy lateral position was favoured in 21 of the 36 (58%) posterolateral oblique fractures managed surgically, compared to 11 of the 31 (35%) medial extension fractures (P< 0.05). Posterolateral oblique injuries were treated exclusively through posterolateral approaches whilst 16 (52%) medial extension injuries were approached through a posteromedial incision (P< 0.05). Medial extension fractures with a 'two part' appearance readily required fixation with a posteromedial plate (48%) which was not clinically necessary in the posterolateral group (P< 0.05). Shell type injuries were managed conservatively.

Conclusions: Pre-operative CT scans can provide essential clinical information which may influence the patient position, surgical approach and method of fixation in patients with a posterior malleolar fractures, in particular the presence of a medial extension injury.

Implications: We advocate CT scans for all posterior malleolar ankle fractures to distinguish between posterolateral oblique and posteromedial injuries to aid pre-operative surgical planning.