Functional comparison of posterior cruciate retention and substitution knee replacement

Thirty-eight matched pairs of osteoarthritic knees from patients who underw ent primary total knee replacements with minimum 2 years of followup were s tudied to compare the functional outcome between a cruciate retention and p osterior stabilized design with essentially identical articulation surfaces . Patients were matched for age, weight, gender, diagnosis, activity, defor mity of the knee, type of tibial component, and duration of followup, The p atients were evaluated functionally by three methods: the Knee Society scor ing system; a self-administered questionnaire; and an activity rating based on distance walked. In addition, in vivo fluoroscopic examination was perf ormed in 10 cruciate retention and 10 posterior stabilized knees to determi ne the functional knee kinematics. Results showed that by patient self-asse ssment, functional improvement was achieved in 35 (92%) cruciate retention knees and 36 (95%) posterior stabilized knees. There was no statistically s ignificant difference between the two groups in the clinical evaluations. F luoroscopic kinematics showed that the posterior stabilized knee experience d 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 crucia te retained knees as determined by gait studies.