Functional comparison of posterior cruciate retention and substitution knee replacement

Thirty-eight matched pairs of osteoarthritic knees from patients who underwent primary total knee replacements with minimum 2 years of followup were studied to compare the functional outcome between a cruciate retention and posterior stabilized design with essentially identical articulation surfaces. Patients were matched for age, weight, gender, diagnosis, activity, deformity of the knee, type of tibial component, and duration of followup. The patients were evaluated functionally by three methods: the Knee Society scoring system; a self-administered questionnaire; and an activity rating based on distance walked. In addition, in vivo fluoroscopic examination was performed in 10 cruciate retention and 10 posterior stabilized knees to determine the functional knee kinematics. Results showed that by patient self-assessment, functional improvement was achieved in 35 (92%) cruciate retention knees and 36 (95%) posterior stabilized knees. There was no statistically significant difference between the two groups in the clinical evaluations. Fluoroscopic kinematics showed that the posterior stabilized knee experienced anteroposterior femorotibial translation more similar to the normal knee during normal gait and deep knee bend. These clinically equivalent results are not in agreement with the predicted better functional results of cruciate retained knees as determined by gait studies.