Sagittal placement of the femoral component in total knee arthroplasty predicts knee flexion contracture at one-year follow-up

Flexion contracture has been shown to impair function and reduce satisfaction following total knee arthroplasty (TKA). The aim of this study was to identify modifiable intra-operative variables that predict post-TKA knee extension. Data was collected prospectively on 95 patients undergoing total knee arthroplasty, including pre-operative assessment, intra-operative computer assisted surgery (CAS) measurements and functional outcome including range of motion at one year. Patients were divided into two groups: those with mild flexion contracture (> 5A degrees) at the one-year follow-up and those achieving full extension. The sagittal orientation of the distal femoral cut differed significantly between groups at the one-year follow-up (p = 0.014). Sagittal alignment of greater than 3.5A degrees from the mechanical axis was shown to increase the relative risk of a mild flexion contracture at one-year follow-up by 2.9 times, independent of other variables. Increasing the sagittal alignment of the distal femoral cut more than 3.5A degrees from the mechanical axis is an independent risk factor for clinically detectable flexion contracture one year from index procedure.