SLR - October 2016 - Julie Rosner

A Novel Algorithm for Isolated Weber B Ankle Fractures: A Retrospective Review of 51 Nonsurgically Treated Patients

Reference: Holmes JR, Acker WB 2nd, Murphy JM, McKinney A, Kadakia AR, Irwin TA.  A Novel Algorithm for Isolated Weber B Ankle Fractures: A Retrospective Review of 51 Nonsurgically Treated Patients. J Am Acad Orthop Surg. 2016 Sep; 24(9): 645–52.

Scientific Literature Review

Reviewed By: Julie Rosner, DPM
Residency Program: Chino Valley Medical Center

Podiatric Relevance: Weber B ankle fractures that result from a supination external rotation (SER) mechanism are the most common ankle fracture pattern. There is controversy regarding the optimal manner in clinically and radiographically distinguishing between an SER-II and SER-IV equivalent injury as they can appear similar on non-weightbearing radiographs. It is widely accepted that SER-II injuries without medial injury can be successfully treated nonsurgically and thus avoid the risks of an open procedure. This study investigated the use of initial gravity stress radiographs with subsequent weightbearing radiographs to determine the stability of an SER-II injury. The study also investigated the outcomes of a treatment protocol that allowed for immediate functional protected weightbearing of SER-II injuries at one year post injury.   

Methods: A retrospective observational case series was performed on 51 patients with nonsurgical SER-II injuries. Patients were evaluated clinically and with gravity stress radiography of the ankle mortise of the injured limb and contralateral limb. Radiographs were evaluated for medical clear space (MCS), and patients with MCS > 7mm were excluded. Patients were permitted to be weightbearing as tolerated in a pneumatic fracture boot. Clinical and radiographic evaluation was performed at each follow-up appointment. If there was a noted displacement at subsequent visits, the patient underwent surgical intervention. Patients were also assessed on a number of outcome measures, including Foot and Ankle Ability Measure for Activities of Daily Living (FAAM/ADL), Olerud-Molander Ankle score (OMA), American Orthopaedic Foot and Ankle Society (AOFAS) Hindfoot score and the visual analog scale. Excellent outcome was defined as a score of ≥90 (FAAM/ADL, AOFAS, OMA) or VAS < 3.

Results: The majority of patients with SER-II injuries that were treated nonsurgically had heavily skewed outcomes. The VAS score was positively skewed, and the AOFAS, FAAM/ADL, OMA were negatively skewed. More than 70 percent of patients achieved an excellent outcome. There were no significant differences based on the degree of MCS widening and no significant outcome for any of the outcome measures. The mean MCS on initial presentation lateral gravity stress radiograph was 4.42 mm. Thirty-one percent of patients had MCS between 5.0 and 7.0mm on initial gravity stress views.  The medial clear space decreased throughout the course of the study; however, this was not significant. Fracture union rate was 100 percent clinically although 15.6 percent of patients did not achieve complete radiographic union. 

Conclusions: Through this study, the authors were able to justify their treatment protocol for SER-II fractures. Initial gravity stress and subsequent serial weightbearing radiographs provide an accurate method for determining if fractures can be safely treated nonsurgically with protected weightbearing. The study calls into question the use of a MCS measurement of 4 or 5mm as the threshold to determine surgical versus nonsurgical intervention, as 31 percent of patients with a MCS > 5.0 were successfully treated nonsurgically.The study was not without limitations and recognizes the need for long-term follow-up.

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