EFFECT OF FIXED FLEXION DEFORMITY ON RANGE OF MOTION FOLLOWING TOTAL KNEE ARTHROPLASTY

Abstract

Introduction Fixed flexion deformity (FFD) represents a challenge during total knee arthroplasty (TKA). Furthermore, controversy exists as to the fate of FFD following TKA.

Aims The aims of this study were to determine how fixed flexion behaves in relation to surgery, factors that may influence or correlate with FFD both preoperatively and following TKA and the effect of FFD on outcome at one year.

Patients and Methods 133 patients (41 males; 92 females) undergoing TKA were prospectively studied. The following data was recorded for each patient: age, gender, primary diagnosis, direction and magnitude of the pre-operative axial deformity, BMI, preoperative and one year Oxford Knee Scores (OKS), the active and passive range of motion (ROM) preoperatively, at the end of surgery and at three month and one year review. FFD was defined as forced passive extension (FPE) greater than zero degrees.

Results Sixty-six patients (50%) had a preoperative FFD (mean, 60). At the end of surgery, this measured 10, 80 at 3 months and 40 at one year. When comparing those with a preoperative FFD to those with no FFD, there was no significant difference when assessing age, BMI or preoperative OKS. Preoperative FFD was significantly more common in males although there was no significant difference in the magnitude of FFD at any stage between males and females. There was a significant improvement in FFD at one year. Patients with a preoperative FFD were found to have significantly less flexion both preoperatively and at one year. When comparing those with FFD at one year to those with no FFD, those with FFD were significantly older and had significantly less flexion. There was no significant difference in BMI, OKS or gender.

Conclusions There is a definite trend when assessing the change in FFD with time. Correction at the time of surgery would appear to be important. Residual FFD is associated with reduced flexion at one year.