Nice guidelines recommend VTE prophylaxis to patients in below knee casts following foot and ankle surgery following risk assessment. The guidelines are controversial and BOFAS recommendations reiterate the risk factors but highlight poor evidence to support these guidelines. Implementation has been variable dependent on interpretation.

58 patients who underwent hindfoot procedures and were immobilised in a cast were identified. These patients were under the care of two consultants, one of whom anticoagulates with daily enoxaparin and one who does not, providing a de facto case-control design. The patients were followed up to identify those who subsequently suffered a DVT or PE, and the clinical circumstances.

2 cases of VTE events were noted in 58 patients undergoing foot and ankle surgery. Both were elective cases managed postoperatively in cast and treated with prophylaxic enoxaparin. Both of these presented to hospital with signs of VTE greater than 6 weeks following surgery after cast removal and discontinuation of enoxaparin. No patients were considered high risk according to NICE guidelines. None of the patients who received no thromboprophylaxis had a clinical DVT.

Within our study group we found that VTE thromboprophylaxis does not influence clinically evident VTE rates. Patients who developed VTE were not considered high risk by definition of NICE guidelines but only at increased risk due to their immobility. The VTE events were initiated while the patients were receiving thromboprophylaxis. The effectiveness of the guidelines in predicting patients who would benefit from chemoprophylaxis is questionable from this study.

NICE guidelines on VTE thromboprophylaxis have been received with some concerns. Although this investigation studied only a relatively small number of patients, it raises issues about the clinical effectiveness of the guidelines in foot and ankle patients.