High BMI increases rates of non-union in hind and mid-foot arthodesis

J. Allport, J. Ramaskandhan, M. Siddique

Background: Arthrodesis is used to treat arthritis and deformity in a range of hind and midfoot joints. The affect of BMI on rates of non-union remains unclear from current evidence. We have analysed our cohort of patients to further examine this relationship.

Methods: 381 primary joint arthrodeses (in 277 patients) were identified from a single surgeon´s logbook. Case notes were reviewed to gather demographic data including BMI. Patients were divided into obese (BMI >30) and normal (BMI< 30). Primary outcome was clinical union as diagnosed by the treating physician at the time, based on clinical and radiological review.

Results: 190 joints were classed as obese and 191 as normal. There were no significant differences in baseline demographics or rates of smoking. There was a significantly higher rate of non-union amongst the obese group (7.9%) than the normal group (2.6%), P-Value 0.030. There was no difference in rates of deep infection or delayed union.

Conclusion: Previous literature has not been conclusive on the impact of BMI on non-union rates. Data from our cohort supports a role of obesity in the development of non-union. The majority of patients are advised to remain non-weightbearing in cast immobilisation post-operatively. It is not clear if our findings are as a result of a physiological or biomechanical cause.