SLR - November 2016 - Katherine R. Schnell

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: Katherine R. Schnell, DPM
Residency Program: Regions Hospital/ Health Partners Institute for Education and Research, Saint Paul, MN

Podiatric Relevance: Weber B ankle fractures are usually due to supination-external rotation (SER) mechanism. This pattern is the most common of the Lauge-Hansen classifications and accounts for 85 percent of all ankle fractures. In order to differentiate SER IV from SER II injuries, medial ankle instability is assessed and can be seen on radiographs as a fracture of the medial malleolus or medial clear space widening. SER-IV injuries with deltoid ligament injury can also be referred to as as SER-IV equivalent injury. It may be challenging to evaluate SER-II and SER-IV equivalent injuries. Also, physical exam is not entirely reliable for deltoid injuries. Manual and stress radiographs have been used, but there continues to be variability on when surgical intervention is necessary. Most of the time, on a mortise view with medial clear space, >4 or 5 mm will warrant surgery. There still seems to be variation on other techniques used to evaluate the deltoid ligament, including MRI and ultrasound. What surgeons agree on is that those injuries that result in an unstable medial ankle are treated surgically. For the most part, the shift has been from conservative to operative, but there are complication rates as high as 10 percent. This paper highlights a protocol of workup, including WB and gravity stress radiographs, along with conservative treatment options for 51 patients with one-year follow-up.

Methods: This was a retrospective review of 51 patients who were referred to an orthopaedic clinic within two weeks of injury with the diagnosis of Weber B ankle fracture with normal mortise on NWB radiographs. If widening was noted on initial NWB radiographs, surgical intervention was recommended. If no widening was seen, stress views and WB ankle views were taken. WB radiographs were also taken of the uninjured side. The medial clear space (MCS) was measured on the radiographs, and if this was >7, they were excluded from the study and surgical treatment was recommended. They were also excluded if the MCS was 2 mm or greater than the SCS (superior clear space) or if the MCS was >2 mm compared to the contralateral side. If MCS was <7, the patients were offered operative or nonoperative management, which consisted of WBAT in a fracture boot for six weeks followed by WBAT in a lace-up brace with low-impact activities (biking, swimming). They had WB radiographs (AP, lateral, mortise) taken at one week, two weeks and 12 weeks, and they evaluated SCS and MCS. If at any time they had MCS >7, surgical intervention was recommended. At 12 weeks, they were released without any restrictions and followed up in one year. AOFAS , VAS, OMA (Olerud-Molander Ankle) Score, and FAAM (foot and ankle ability measure for activities of daily living) Score were evaluated. A score of >90 for AOFAS, OMA and FAAM and VAS <3 was defined as an excellent outcome.

Results: From November 2010 to June 2013, 108 patients were referred for Weber B ankle fractures. Ten of these patients were treated surgically. Others were excluded due to bilateral injuries. Many were lost to follow-up and 51 patients had one-year follow-up. There was one patient who initially was being treated conservatively who at his one-week follow-up then had lateral fibular displacement but still no MCS widening. He elected to proceed with surgery at that time. At one year post-op, AOFAS score was 93.2, FAAM was 93.2, OMA was 91 and VAS was 0.57. The mean gravity stress MCS was 4.42 mm at initial presentation of the injured ankle. On follow-up at one week, it was 2.81 mm, at 12 weeks, it was 2.66 mm, and at one year follow-up, the MCS was 2.64 mm. Only four patients had a MCS >4 mm, and all but one patient had a decrease in their MCS. Union rate of the fracture at one-year follow-up was 100 percent clinically, but 15.6 percent of patients had a visible fracture line on x-rays.

Conclusions: Initial WB ankle radiographs are predictive of stability in isolated Weber B ankle fractures. They conclude that the threshold of 4 or 5 mm for MCS widening on gravity stress radiographs may be overestimating instability because their MCS was 4.42 mm and that conservative weightbearing in a below-knee fracture boot may be an alternative treatment option worth considering. 

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