SLR - March 2019 - Jack Levenson

Immediate Weightbearing Protocol for the Determination of Ankle Stability in Patients with Isolated Distal Fibular Fractures

Reference: Bonness EK, Siebler JC, Reed LK, Lyden ER, Mormino MA. Immediate Weightbearing Protocol for the Determination of Ankle Stability in Patients with Isolated Distal Fibular Fractures. J Orthop Trauma. 2018 Oct;32(10):534–537.

Scientific Literature Review

Reviewed By: Jack Levenson, DPM
Residency Program: New York Presbyterian/Queens, Flushing, NY

Podiatric Relevance: Several methods have been developed to determine the stability of the ankle mortise in isolated distal fibular fractures, such as acute manual stress testing and/or gravity stress testing. It is the authors’ contention that such stress testing may be unnecessary and in fact yield false positive results, ostensibly potentiating the need for otherwise avoidable operative treatment. Offered is an immediate protected weightbearing (WB) protocol for isolated distal fibular fractures in which initial nonweightbearing (NWB) films reveal an intact medial clear space (MCS, <4 mm) or a difference of <1 mm in relation to the superior clear space. These patients would then undergo weightbearing radiography ~ one week post injury to assess for ankle instability using the parameters as aforementioned.

Methods: This is a retrospective case series assessing an immediate WB protocol in isolated distal fibular fractures without MCS widening on initial NWB radiographs. Eighty-two patients met this inclusion criteria, none of whom underwent any type of stress testing and instead were instructed to WB immediately in a functional walking boot. WB radiographs were then obtained one week post injury with MCS widening 4 mm indicative of an unstable fracture necessitating operative treatment; <4 mm indicative of a stable fracture and conservative management. Outcome measures included the percentage of patients deemed to have unstable fractures using this method vs. stable fractures, as well as average MCS widening in these populations at initial NWB radiographs and one-week WB radiographs.

Results: All 82 patients were managed with immediate WB. Only two patients (3 percent) had an MCS >4 mm on one-week WB radiographs, with an initial MCS of 3.82 ± 0.18 and a one-week WB MCS of 4.30 ± 0.09. Both patients went onto ORIF without complication. Seventy-seven patients were diagnosed with stable fractures with initial NWB MCS of 3.17 ± 0.59 and a one-week WB MCS of 2.81 ± 0.55. All these patients went onto full bony union, with a mean MCS measuring 2.76 ± 0.51 mm on final radiographs. The average patient age was 48 years; 57 percent were female, and 43 percent were male. Average follow-up was 15.8 weeks. 

Conclusion: Assessment of ankle fracture instability in isolated distal fibular fractures remains unclear. Studies have reported anywhere from 37 to 65 percent of isolated distal fibular fractures to be radiographically unstable under external stress. Weber et al concluded only 9 percent of these fractures to be truly unstable. In concordance, MRI studies have shown only 10 percent of patients with stress positive ankle fractures truly have deltoid disruption. Other studies have shown just a 2.9 percent correlation between positive external stress tests and weightbearing stress one week later and excellent AOFAS scores with nonoperative treatment. Similarly, this study aimed to obviate the need for stress testing in the emergency or acute care setting with an alternative immediate weightbearing protocol for assessment of ankle fracture instability utilizing WB radiographs one week post injury. Obvious pitfalls to this study include its retrospective design as well as the absence of functional outcome scores.

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