Patients with fixed flexion deformity after total knee arthroplasty do just as well as those without: ten-year prospective data

Range of motion (ROM) is an important outcome variable after total knee arthroplasty (TKA). This may be compounded by a pre-existing fixed flexion deformity (FFD). We therefore examined the long-term outcomes of patients with a flexion deformity undergoing TKA compared to those without a preoperative fixed flexion deformity. Participants who had undergone TKA at our centre between 1989 and 2002 were examined preoperatively, one, five and ten years after TKA (Kinemax PS; Howmedica, Rutherford, NJ, USA). Examining those with a preoperative FFD of greater than ten degrees with complete ten year follow-up data revealed 77 individuals. Seventy seven age, sex and body mass index matched patients were identified and the effect of TKA on indices of knee function (fixed flexion, maximum flexion, total ROM and Knee Society score (KSS) in both groups were analysed using repeated measures ANOVA. A significant difference between the groups with respect to fixed flexion (p < 0.001), total ROM (p = 0.001) and KSS (p < 0.001) was observed between baseline and year one suggesting that those with a preoperative FFD improved more than those without. A significant difference with regard to fixed flexion was also observed between years one to five (p = 0.001) and just failed to reach statistical significance between five to ten years (p = 0.052) between the groups. This study demonstrates that patients with a preoperative fixed flexion deformity show continued improvement in their fixed flexion up to ten years post arthroplasty and have similar outcomes to those with no preoperative fixed flexion.