Gravitational stress views overestimate ankle instability and may commit patients to unnecessary surgery: a prospective series with 10 year follow up

N Heinz, H Hanif, K Bugler, A Duckworth, T White

Background: Distinguishing stable from unstable ankle fractures is key to successful ankle fracture management. Gravitational stress views (GSV) may be a convenient and less painful alternative to manual stress testing. The aim of this study was to assess whether this test accurately predicts ankle instability.

Methods: Patients presenting to a single trauma centre between 2011 and 2013 with an isolated fibula fracture and a an anatomically-aligned mortise on initial plain film radiographs were reviewed. After initial x-ray, patients underwent a gravity stress view. Measurements from plain film radiographs were recorded and analysed. Electronic case notes and National Imaging Archives were reviewed retrospectively at a minimum of 10 years post-injury. Patients were contacted to complete patient reported outcome measures (PROMS).

Results: One-hundred and forty-two (142) patients met the inclusion criteria and were included in the study. Mean initial film medial clear space (MCS) measurement was 3.46mm (1.0 to 6.0) compared to GSV MCS that was 4.9mm (2.0 to 8.8) (p<0.001). No patient underwent surgery and all patients had successful conservative management with anatomical union seen at their 6 week radiograph. No patient returned with a complication related to their ankle
fracture during the follow-up period. With a MCS acquired from GSV of >5mm, 65 patients would have undergone unnecessary surgical intervention. At MCS of >6mm, 26 patients would have undergone surgery unnecessarily and at a MCS of >7mm 10 patients would have had unnecessary surgery. To date, 50 patients have provided PROMs. Mean Olerud and Molander Score (OMAS) at 10 years was 86.63 (SD 23.27, 95% CI 79.47 - 93.79), Manchester Oxford Foot Questionnaire (MOXFQ) was 79.41 (SD 32.94, 95% CI 69.39 - 89.42) and Euroqol-5D-3L was 0.86 (SD0.22, 95% CI 0.79 - 0.93).

Conclusion: Stress views may over-diagnose instability in patients with an isolated fibula fracture in an otherwise normal initial radiograph.