In recent literature, the fragility index (FI) has been used to evaluate the robustness of statistically significant findings of dichotomous outcomes. This metric is defined as the minimum number of outcome events to flip study conclusions from significant to nonsignificant. Orthopaedics literature is frequently found to be fragile with a median FI of 2 in 150 RCTs across spine, hand, sports medicine, trauma and orthopaedic oncology studies. While many papers discuss limitations of FI, we aimed to further characterize it by introducing the Fragility Likelihood (FL), a new metric that allows us to consider the probability of the event to occur and to calculate the likelihood of this fragility to be reached.

We systematically reviewed all randomized controlled trials in the Journal of Bone and Joint Surgery (Am) over 10 years. The FL was calculated with the following formula: A x B x C x 100% (A= FI; B = probability of the event in the group with the smallest number of events; C= probability of the non-event in the group with the highest number of events). A smaller FL demonstrates more robust results and conversely, a larger FL illustrates a higher likelihood of fragility being reached and more fragile the findings.

The median FI for the statistically significant outcomes was 2 (Mean: 3.8; Range 0-23). The median FL for the statistically significant outcomes was 11% (Mean: 22%, Range: 2%-73%). This means that the probability of reaching non-significance is only 11% when considering the probability of the event to occur. When comparing studies with the same FI we found the FL to range from 3% to 43%. This illustrates the large differences in robustness between trials with equal FI when the likelihood of the event was taken into consideration.

As orthopaedic studies are frequently reported as fragile, we found that by calculating the FL, studies may be more robust than previously assumed based off FI alone. By using the FL in conjunction with FI and p-values will provide additional insight into the robustness of the reported outcomes. Our results indicate that by calculating the FL, study conclusions are stronger than what the FI alone predicts. Although conducting RCTs in surgery can be challenging, we must endeavor to critically evaluate our results so we can answer important orthopaedic questions with certainty.

The National Institute of Clinical Excellence (NICE) published guidance for reducing the risk of venous thromboembolism (VTE) in January 2010. This guidance has had a significant impact on the management of all inpatients. It is now mandatory to risk assess every inpatient and commence appropriate treatment if indicated. The guidelines specifically exclude outpatients although NICE recognises' that lower limb cast immobilisation is a risk factor for VTE. The purpose of our study was to establish the current practice for the management of outpatients treated with lower limb casts in England.

The NHS Choices website lists 166 acute hospitals in England. A telephone audit was conducted in February 2011. A member of the on call orthopaedic team was asked: 1. Are you aware of the NICE guidelines for VTE prophylaxis? 2. In your department, outpatients treated with a lower limb cast, are they risk assessed for VTE? 3. If a patient undergoes Open Reduction Internal Fixation (ORIF) for an ankle fracture and is discharged wearing a cast, are they given VTE prophylaxis? 4. If yes - for how long are they treated?

Responses were obtained from 150 eligible hospitals (1 FY1, 28 FY2, 44 ST1-ST2, 76 ST3+, 1 Consultant). 62% of responders stated that they were aware of the NICE guidance. 40% of responders stated that outpatients were routinely risk assessed for VTE. 32% of responders stated that ankle fractures treated with an ORIF and discharged wearing a cast would receive VTE prophylaxis. The duration of treatment varied from 5 days, to 6 weeks, to removal of cast.

The management of patients treated with a lower limb cast is variable and inconsistent throughout England. Although there are no national guidelines for this patient group, the routine risk assessment of outpatients was higher than anticipated by the authors. We recommend that if VTE prophylaxis is commenced as an inpatient, then it should be continued until the cast is removed.