Unstable ankle fractures are commonly treated operatively. After operative reduction and fixation of the fractures, there are varying rehabilitation regimes that include non-weightbearing for 6 weeks with active range of motion exercise in a removal cast or brace, or early protected weightbearing in a rigid cast. Several papers reported that early weightbearing may decrease ankle stiffness, muscle and bone atrophy, and aids in early return to activities. However, early weightbearing may have the risk of displacement of the fixed fractures. Rehabilitation after operative treatment of an ankle fracture is still not clear. We hypothesized that the ankle function assessed on 12 months after operation of an ankle fracture with early weightbearing is not inferior to non-weightbearing but is superior to non-weightbearing with respect to time to return to normal daily life and time to full weightbearing.

This study is a noninferiority, randomized controlled trial of patients presenting to multiple centers.

The primary outcome measure is the Olerud-Molander scores assess on 12 months after operation of an unstable ankle fracture. The Olerud-Molander scores were compared between the experimental group (early weightbearing) and the control group (non-weightbearing) on 12 month follow-up examination.

The Olerud-Molander score is a most widely used validated scale to assess ankle function after an ankle fracture. It is a self-administered patient questionnaire with a score of zero (totally impaired) to 100 (completely unimpaired) and is based on nine different items: pain, stiffness, swelling, stair climbing, running, jumping, squatting, supports and work/activities of daily living.

The secondary objectives are to determine whether early weightbearing is superior to non-weightbearing with respect to time until return to normal daily life and time to full weightbearing.

Other objectives are to determine safety by assessing number of participants with adverse effect such as hardware failure, reduction loss, non-union, or delayed union in each group.

The sample size was determined using methods appropriate for noninferiority trials, assuming 90% power and a significance level of 0.05. To find out whether the early weightbearing is not inferior to nonweightbearing after operation of an ankle fracture, 192 patients were required to have 90% power that the lower limit of an one-sided 95% confidence interval for the difference between two treatments will be above the noninferiority margin of -8, adding 20% of assumed drop-out.

Determination of the noninferiority margin was based on clinical significance. In a previous study between early weightbearing versus nonweightbearing after an ankle fracture surgery, Simanski et al. reported that both groups showed good results in the Olerud-Molander score (87 vs. 79 points; p=0.25). In both groups, the majority of patients reached their preinjury level of activity. The difference in the Olerud-Molander score between the two groups was 8 points in favor of early weightbearing. Their study came from populations similar to our trial population and from interventions similar to those being studied in the current trial. We decided that the noninferiority margin at 8 points difference will be adequate to prove noninferiority of the experiment group (early weightbearing) over the control group (nonweightbearing).

If a subject had discontinued prior to completion of 12 months, the last observation is carried forward for the intent-to-treat analysis. Subjects who crossed over to the other treatment arm, for an example, patients in non-weightbearing group who weightbear early, are analyzed according to their initial group allocation for the intent-to-treat analysis. Additionally, an as-treated (per-protocal) analysis was also conducted on patients who completed the 12 months follow-up with the protocol assigned.

Inclusion Criteria:

• unstable ankle fracture requiring open reduction and internal fixation
• age between 18 and 65 years
• satisfactory reduction and stable fixation after operation.

Exclusion Criteria:

• open fractures
• comminuted fractures
• pathologic fractures
• Pilon fractures
• Trimalleolar fractures
• fracture dislocations
• Fractures requiring syndesmotic screw fixation
• Fractures with cartilage injuries or unstable fixation or any other conditions preventing from early weightbearing.
• Patients with diabetes or neuroarthropathy
• Patients with obesity (BMI >30, weight >100 kg)
• Any other conditions that are expected to prevent the patients from following the study protocol