Introduction

We have carried out a 15 year survival analysis of a prospective, randomised trial comparing cemented with cementless fixation of press-fit condylar primary total knee replacements.

We report the results of a prospective randomised controlled clinical trial assessing the radiosterophotogrametric analysis (RSA), clinical and radiological performance of a metal backed and an all-polyethylene tibial cruciate retaining, condylar design, PFC-TKA up to twenty four months.

65 patients were recruited, of which 41 patients were randomised. There were 20 metal backed and 21 all-polyethylene. None were lost to follow-up. There were no significant inter-group demographic differences. We found a significant increase in SF-12 and Oxford knee scores after surgery in both groups. No significant difference was found between the groups in the RSA, SF-12, Oxford Knee score, radiological alignment and range of movement at 6, 12 or 24 months. At 2 years one metal backed implant showed translational migration > 1mm. No all polyethylene implant migrated > 1mm. Further analysis identified possible progressive subsidence of the metal backed implants compared to all-polyethylene implants, although the magnitude of this difference was very small.

We conclude that in the uncomplicated primary total knee arthroplasty, all polyethylene PFC-_ tibial prostheses had equivalent performance to the metal backed counterpart, using RSA as the primary assessment instrument at 24 months. We found no differences between the two designs as assessed by the secondary instruments: SF-12, Oxford knee score, alignment and range of movement at 24 months. Should half of all primary total knee replacements performed in the UK receive an all-polyethylene tibial implant, the estimated annual cost saving would be 21 million pounds per annum.

Cementless fixation for total knee arthroplasty (TKA) has been proposed as an alternative to cemented for several reasons, of which the most important is the possibility of increased survival. The purpose of this study was to compare the ten-year survival of TKA in a unique prospective randomised trial of cemented versus cementless fixation.

A consecutive series of patients was randomised to undergo either cemented or cementless Press-Fit Condylar (PFC®) TKA. There were 219 patients (277 TKA) in the cemented group and 177 (224 TKA) in the cementless group. There were no significant differences in age, gender or diagnosis between the two groups.

A single surgeon (PJG) performed or directly supervised all operations. The prosthesis used in all cases was the posterior-cruciate-retaining PFC® knee replacement system. Independent clinical review was performed at six months, annually until five years, and finally at ten years after surgery. Using revision surgery as the end-point, logrank analysis was used to compare the ten-year survival of the two groups.

The mean interval of follow-up was 6.3 years (range, 2.0–11.7). At the last review, 104 patients (138 TKA) had died, without need for revision. All patients were traced and there was no loss to follow-up. In the cemented group, seven arthroplasties were revised; five for infection and two for exchange of polyethylene inserts. Ten-year survival was 96.5% (95% CI, 90.9–98.7%). In the cementless group, six arthroplasties were revised; three for aseptic loosening, one for infection, one for instability and one resizing for anterior knee pain. The ten-year survival was 96.6% (95% CI, 89.6–98.9%). There was no significant difference in the survival of the two groups.

The long-term survival of cementless PFC® TKA is not significantly different from their cemented counterparts. The use of less expensive cemented implants, therefore, can make a significant impact on health resource planning.