NATURAL HISTORY OF FIXED FLEXION DEFORMITY FOLLOWING TOTAL KNEE ARTHROPLASTY- A PROSPECTIVE STUDY

Abstract

Introduction: Stiffness following total knee arthroplasty is a disabling problem resulting in pain and reduced function. Prevalence is not well defined and although various treatment modalities including manipulation, arthrolysis and revision surgery has been proposed with varying degrees of success for reduced flexion, these Methods: are deemed to be of limited value in fixed flexion deformity (FFD). There is limited literature on the natural history of FFD which is important to the decision process. The aim of our study was to evaluate the natural course of FFD following primary total knee arthroplasty.

Methods: Prospective review of a consecutive series of 1768 patients who underwent primary total knee arthroplasty over a 7 year (2001 to 2008) period. Demographic data included post-operative range of motion; type of prosthesis used, treatment modalities for stiffness and the final range of motion were recorded. FFD was defined as class 1(hyperextension to 0), Class 2 (1–10 degrees), Class 3(11–20 degrees) and Class 4(> 20 degrees).

All patients were reviewed by an independent reviewer (senior physiotherapist). All patients were followed from 6 weeks post surgery until FFD completely resolved or improved to patient satisfaction. Patients with infection, stiffness treated with manipulation or revision surgery were excluded from the study. Patients lost to follow-up were noted.

Results: Of the 1768 patients evaluated, 180 (10.2%) presented with a FFD. A total number of 18 patients were excluded from the study and 16 were lost to follow up. None (0%) were class 1, 134 (91.8%) were class 2, 10 (6.9%) were class 3 and 2 (1.4%) were class 4. The FFD group had a mean age of 60.5. Follow up period ranged from 1.3 to 63.3 months and the FFD improved from a mean of 8.16 degrees to 0.15 degrees (p< 0.001). In 94.5% patients the FFD completely resolved (i.e. < 5 deg) at a mean of 9.76 months. In the remaining 5.5% of patients, FFD improved from a mean of 16.4 to 6.9 degrees at a mean follow up of 15.5 months and was found to cause no functional deficit.

Conclusion: The overall prevalence of fixed flexion deformity is 10.2 % with only 0.7% in Class 3 and Class 4, which is comparable with the literature. The majority of patients will see a resolution of their fixed flexion deformity in less than 10 months with routine post operative physiotherapy. The small number of patients left with a residual FFD did not appear to suffer a functional deficit. Patients found to have a post operative FFD should be reassured and encouraged to participate in a standardised post operative physiotherapy regime.