For unimalleolar Weber B ankle fractures with a congruent mortise on initial radiographs but deemed unstable on external rotation stress testing, cast immobilization was found to be no worse than surgery in terms of functional outcomes at 2 years postinjury, based on the results of a randomized noninferiority trial—SUPER-FIN—published in BMJ by Tero Kortekangas, MD, PhD, of Oulu University Hospital, Finland, and colleagues.
About two-thirds of ankle fractures involve Weber B fractures of the lateral malleolus. Depending on the severity of the trauma and any associated soft tissue injury, these fractures can result in either a stable or unstable ankle.
“Surgery remains the main treatment for Weber B ankle fractures deemed unstable, despite recent trials and guidelines increasingly supporting nonoperative options in selected patients,” the researchers explained. However, beyond the lack of functional benefit over cast immobilization observed in this study, “patients should be advised that surgery carries a risk of treatment-related adverse events.”
Study Methods in Brief
The study was conducted at a specialist university hospital trauma center in Finland between January 16, 2013, and July 7, 2021. A total of 840 skeletally mature patients aged at least 16 years with an isolated Weber B fibula fracture on static radiographs were screened. After assessing fracture stability with a standard external rotation stress test under fluoroscopy, 126 with a congruent but unstable ankle mortise were randomly assigned to treatment.
The patients received either 6 weeks of conventional cast immobilization (n = 62) or surgery with open reduction and internal plate fixation followed by 6 weeks in a cast (n = 64). A total of 121 patients (96%) completed the 2-year follow-up.
The primary outcome measured was ankle fracture symptoms using the Olerud-Molander Ankle Score (OMAS), where higher patient-reported scores indicate better recovery, at 2 years. Secondary outcomes included ankle function, pain, health-related quality of life, ankle range of motion, and radiographic outcome. Treatment-related complications were also reported.
Cast vs Surgery Outcomes
In the primary intention-to-treat analysis, the mean OMAS was 89 with cast immobilization and 87 with surgery, yielding a between-group mean difference of1.3 points, meeting the predefined noninferiority margin of −8 points. No statistically significant between-group differences were found across any secondary outcome measures.
Radiographic nonunion was identified in one patient in each group. No participant in either group experienced loss of ankle mortise congruency during follow-up.
Within the surgery group, complications included one superficial wound infection, one case of delayed wound healing, and nine hardware removal procedures; among those undergoing hardware removal, two patients experienced postoperative infections—one deep and one superficial. Overall, treatment-related adverse events were more frequent in the surgical group.
The researchers concluded, “Together, our findings and those of previous studies show that a standard below-the-knee cast provides adequate stabilization of an isolated unimalleolar fibular fracture with a congruent ankle mortise. This lends further support to the evolving concept that the treatment of ankle fractures should focus on obtaining and maintaining a congruent ankle mortise until fracture union, using the most conservative means possible.”
Full disclosures can be found in the study.
Source: BMJ
