What is the Ideal Degree of Extension After Primary Total Knee Arthroplasty?

Abstract

Background: Few studies have examined flexion contracture at the time of primary total knee arthroplasty (TKA) or how flexion contracture changes over time. The purpose of this study was to assess the ideal degree of extension immediately after TKA and to document postoperative changes in extension and clinical outcomes over 5-year follow-up. Methods: This retrospective cohort study included 215 cases of primary TKA. Radiographic evaluations were performed on sagittal radiographs with the patient in the supine position and the knee in gravity and in passive extension using a stress device. Clinical outcomes were also measured. Four groups were defined on the basis of the extension angle during radiological evaluation: group 1, -10 degrees to 0 degrees; group 2, > 0 degrees to +5 degrees; group 3, > +5 degrees to +10 degrees; group 4, > +10 degrees in gravity. Results: There were statistically significant differences in passive extension and gravity extension angles in groups 1, 3, and 4 with time-dependent and time* group (passive vs gravity) analyses, but not in group 2. The flexion contracture angles over 10 degrees in gravity were decreased, although over 5 degrees of flexion contracture remained at the final follow-up. Clinical outcomes were worse in groups 1 and 4 at the final follow-up. Conclusion: An extension angle between 0 degrees and 5 degrees in the passive extension position immediately after TKA can be considered ideal up to 5 years of follow-up. Patients with flexion contracture greater than 5 degrees in passive extension and patients with hyperextension should be followed up to assess whether the condition will worsen. (C) 2017 Elsevier Inc. All rights reserved.