A six-week cast has been shown to be as effective as surgery for unstable ankle fractures

A six-week cast has been shown to be as effective as surgery for unstable ankle fractures

Wearing a cast for six weeks appears to be no less effective than surgery in healing unstable ankle fractures and poses less treatment-related damage, says a clinical study from Finland published byThe BMJToday.

About two-thirds of all ankle fractures involve a break in the fibula (outer ankle bone). They are known as Weber B fractures and cause the ankle joint to be either stable or unstable (with the risk of it falling out of alignment).

Surgery remains the main treatment for Weber B ankle fractures, which are considered unstable, although recent studies and guidelines increasingly support nonsurgical options in select patients.

To investigate this further, researchers wanted to assess whether cast immobilization is comparable (“non-inferior”) to surgery in adults with Weber B ankle fractures that are considered unstable.

They identified 126 participants aged 16 years or older with an unstable Weber B ankle fracture confirmed by an external rotation stress test at a trauma center at a specialized university hospital in Finland between January 2013 and July 2021.

Sixty-two participants were randomly assigned to conventional cast immobilization for six weeks and 64 were assigned to surgery followed by cast immobilization for six weeks.

Both groups had check-ups after two, six and twelve weeks and met with a physiotherapist after six and twelve weeks to accompany the rehabilitation.

After two years, participants were assessed using the Olerud-Molander Ankle Score (OMAS), a scale of 0 to 100 points, with higher scores indicating better healing. The non-inferiority margin was preset at a difference of 8 points between groups.

Further follow-up examinations included ankle function, pain, health-related quality of life, ankle mobility and radiographs. Treatment-related adverse events were also recorded.

In total, 121 of the 126 randomized participants completed the two-year follow-up. The mean OMAS score was 89 in the cast immobilization group and 87 in the surgery group (a mean between-group difference of 1.3 points).

No statistically significant differences were found between groups in any of the other outcomes, and overall there was less treatment-related damage with cast immobilization compared to surgery.

The authors acknowledge that their study was conducted from a single academic hospital, which may limit generalizability, and note the lack of consensus on the external rotation stress test to determine fracture instability. However, they say it was a robust analysis that achieved a high follow-up rate at two years - a time point generally considered sufficient to capture longer-term outcomes.

“Taken together, our results and those of previous studies demonstrate that a standard below-the-knee cast provides adequate stabilization of an isolated unimalleolar fibular fracture with congruent ankle interlocking.” [the bracket-shaped socket of the ankle],” they write.

“This further supports the evolving concept that treatment of ankle fractures should focus on obtaining and maintaining a congruent ankle joint using the most conservative means possible until fracture healing.”

This team deserves praise for conducting a robust study that addresses an important clinical question and will support treatment decisions and updates to clinical guidelines, British researchers say in a linked editorial.

They discuss some limitations, but collectively say that these and other studies "support much-needed advances in the evidence base for the treatment of ankle fractures and are a testament to the collaborative network of trauma and orthopedic health professionals, researchers, and, most importantly, patient participants."

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