Abstract
Statement of purpose: To evaluate survivorship and knee function in patients who have undergone Kinematic Condylar Total Knee Replacement at a minimum of 15 years.
Methods: We evaluated all patients undergoing primary cemented TKR with the Kinematic Condylar implant (Howmedica), between January 1981 and December 1988. All operations were performed by a single surgeon through a medial parapatellar approach, with sparing of the PCL, all cemented and no patellae resurfaced.
Operation notes were analysed to confirm the type of procedure, underlying diagnosis, and thickness of tibial insert. Information was derived from patient records and postal questionnaire to all surviving patients, which included: WOMAC, SF-36, satisfaction scale and history of revision surgery.
Results: We have identified a total of 804 consecutive cases, 185 of these were bilateral giving a total of 619 patients. Mean age at implantation was 66 (range 17 to 83), with female:male ratio of 3:1. The underlying diagnosis was Osteoarthritis in 49%, and Rheumatoid Arthritis in 51% of patients.
As at September 2003 there were 153 patients (25%) still alive, using revision as an endpoint survivorship was 59.3% at a mean time since implantation of 17 years 8 months. Pain and function portions of the WOMAC questionnaire revealed mean scores of 37 and 47 out of 100.
Conclusion: This cohort has been shown to have 92% implant survivorship at ten years. We have shown that the survivorship deteriorates significantly between 10 and 17 years. Functional and pain scores after 17 years for patients with surviving implants were poor.
Survival was significantly better in females, no effect from pre-operative diagnosis was seen. 73% of these patients had 6mm tibial inserts, we postulate that the deterioration in survival is related to accelerated poly-ethylene wear beyond 10 years.
Correspondence should be addressed to Roger Smith, Honorary Secretary, BASK c/o Royal College of Surgeons, 35 – 43 Lincoln’s Inn Fields, London WC2A 3PN
