For physiotherapists working in orthopedics and trauma, the management of Weber B fibula fractures remains a frequent topic of debate. Specifically, the treatment pathway for fractures that appear congruent on static radiographs but demonstrate instability under external rotation stress testing has historically leaned toward surgical intervention. However, new high-quality evidence challenges this dogma. The SUPER-FIN trial, a randomized non-inferiority clinical trial published in the BMJ in January 2026, provides compelling data suggesting that conservative management may be just as effective as open reduction and internal fixation (ORIF).
The Clinical Dilemma: Stress-Positive Weber B Fractures
Isolated distal fibula fractures (Weber B) are the most common ankle fractures. While fractures with obvious mortise incongruence require surgery, the “grey zone” involves fractures that sit anatomically on initial X-rays but open up under fluoroscopic stress tests. The prevailing assumption has been that this instability warrants stabilization to prevent post-traumatic arthritis and ensure optimal function. The SUPER-FIN investigators sought to determine if cast immobilization is non-inferior to surgery for this specific subgroup of patients.
Study Methodology
This pragmatic trial was conducted at a specialist university hospital trauma center in Finland. The researchers screened 840 skeletally mature patients. Of these, 126 patients met the specific criteria: an isolated Weber B fracture with a congruent mortise on initial static imaging, but proven instability (widening) during an external rotation stress test. Participants were randomized into two groups:
- Surgical Group (n=64): Open reduction and internal plate fixation followed by cast immobilization for six weeks.
- Conservative Group (n=62): Conventional cast immobilization alone for six weeks.
The primary outcome measure was the Olerud-Molander Ankle Score (OMAS) at the two-year follow-up mark. Secondary outcomes included ankle range of motion, pain levels, quality of life, and radiographic outcomes.
Key Findings: Non-Inferiority Confirmed
The results of the SUPER-FIN trial strongly support the efficacy of non-operative management. At the two-year follow-up, 121 participants (96%) completed the study. The mean OMAS was 89 in the cast immobilization group compared to 87 in the surgery group. The mean difference of 1.3 points confirmed that cast immobilization was non-inferior to surgery. Furthermore, there were no statistically significant differences between the groups regarding secondary outcomes such as ankle function, pain, or range of motion.
Complications and Harms
One of the most significant takeaways for clinicians is the safety profile. While functional outcomes were similar, the surgical group faced a higher burden of treatment-related adverse events. In the surgery group, complications included superficial wound infections, delayed wound healing, and notably, nine patients required secondary procedures for hardware removal. Two of those hardware removal cases developed subsequent postoperative infections. By contrast, the cast group avoided these surgical risks entirely, with only one participant in each group showing radiographic evidence of non-union.
Implications for Physiotherapy Practice
These findings suggest a potential paradigm shift in referring and rehabilitating unstable Weber B fractures. For physiotherapists, this evidence supports a conservative approach for patients with stress-positive but statically congruent fractures. It highlights that avoiding the trauma of surgery and hardware implantation does not compromise long-term ankle function. Rehabilitation protocols for these patients can proceed with confidence that non-operative healing yields excellent OMAS scores without the associated risks of surgical site infections or future hardware removal surgeries.
References
Kortekangas, T., Lehtola, R., Leskelä, H. V., Taimela, S., Ohtonen, P., Savola, O., Järvinen, T. L. N., & Pakarinen, H. (2026). Cast immobilisation versus surgery for unstable lateral malleolus fractures (SUPER-FIN): randomised non-inferiority clinical trial. BMJ (Clinical research ed.).
