Press-fit knee prosthesis shows good survivorship at up to 17 years postop

Investigators found no evidence of radiographic loosening in any knees and all radiolucent lines were nonprogressive.

A press-fit condylar-designed total knee arthroplasty prosthesis shows "excellent" survival at long-term follow-up of 14 to 17 years, according to a study by California researchers.

David J. Rodricks, MD, and colleagues at the Scripps Clinic in La Jolla, Calif., reviewed the long-term results for 160 knees of 134 patients implanted with the Press-Fit Condylar (PFC; Johnson & Johnson) total knee arthroplasty (TKA) prosthesis between November 1986 and September 1989. At the time of latest follow-up, 82 patients had died and one patient resided outside of the U.S. and was lost to follow-up. Thus the current analysis included data for 63 knees of 51 surviving patients.

In all cases, the surgeon cemented the femoral, tibial and patellar components in place.

Patients averaged 70.5 years at the time of their index operation and averaged 80 years at most recent follow-up.

Preoperative diagnoses included osteoarthritis in 134 knees, rheumatoid arthritis in 20 knees, post-traumatic arthritis in three knees and osteonecrosis in three knees.

At 15.8 years' mean follow-up, the surviving patients had a mean Knee Society score for function of 65 ± 29.1 points. But, "With the exclusion of six patients who were essentially unable to walk because of severe systemic disease, the mean functional score improved to 70," the authors noted.

"The mean Knee Society functional score ... was low (65 points), and we attribute this finding to the age of the patients at the time of follow-up and their inherent infirmity. In general, the functional score was more a reflection of the health status of individuals in that particular age-group and, as expected, was lower than what was previously reported after a shorter follow-up period," the study authors said.

Of the 63 surviving knees, none had severe pain, only six knees (10%) had moderate continuous pain or moderate occasional pain and four knees (6%) had mild or occasional pain when walking or climbing stairs, according to the study. The remaining 53 knees (84%) had either no pain or occasional pain, the authors noted.

Knee Society clinical scores were available for 34 knees of 27 patients, only one of whom had less than 90° range of motion.

Radiographic studies were available for 34 knees, of which 21 knees (62%) showed radiolucent lines. However, investigators found no evidence of radiographic loosening in any knees, and all radiolucent lines were nonprogressive, according to the study.

Excluding the one patient lost to follow-up, 11 of the 159 knees required exchange of at least one implant component by 17 years follow-up, yielding a 92.8% survival rate. The survival rate increased to 98% when revision for aseptic loosening was considered the endpoint.

"Only four tibial polyethylene inserts from the entire series were revised because of wear-related aseptic loosening," which translates to a 2.5% revision rate for this cause, the authors noted.

DePuy Orthopaedics, a division of Johnson & Johnson, currently markets the updated design to the PFC knee prosthesis, the PFC Sigma knee system.

For more information:
Rodricks DJ, Patil S, Pulido P, Colwell CW. Press-fit condylar design total knee arthroplasty. J Bone Joint Surg Am. 2007;89-A:89-95.