Introduction: Concerns of backside wear have made the use of the all polyethylene tibial component a viable choice in primary total knee arthroplasty. This study compares the results of two groups, one with a modular tibial component and one with an all polyethylene tibial component.

Materials: Between 1986 and 1995, 670 patients underwent total knee arthroplasty using one design with a PCL retaining prosthesis. 500 patients in this group were implanted with a modular tibial component and 170 an all polyethylene tibial tray. The groups were comparable in sex and age (74.1 years for the metal trays and 75.8 years for the all polyethylene components.). The average follow up is 83.9 months for the metal tray group and 74.8 months for the all poly tibial group. The arthroplasties were evaluated annually using the Knee Society guidelines.

Results: The postoperative Knee Society Score were 74.5 (metal) and 73.9 (all polyethylene). Joint specific scores for the all polyethylene were slightly higher at 89.9 compared to 88.5 for the metal tray group. Revision rates were 1.8% (3 cases in the polyethylene group) and .8% for the metal group (8 cases). The 3 revisions in the all polyethylene group were for late infections while 5 of the 8 in the metal group demonstrated polyethylene wear/osteolysis.

Discussion and conclusions: The clinical results of the all polyethylene group are equal the modular tibial tray group. Because of the excellent radiographic results and non-existent mechanical failure rate to date, the all polyethylene group also provides an opportunity to reduce wear debris with subsequent osteolysis.

Introduction: The purpose of this paper is to present the results of a prospective study involving one stem design used in primary total hip arthroplasty with three different surface enhancements to include a simple textured geometry, a plasma sprayed coating and an hydroxyapatite (HA) coating.

Methods: Between 1990 and 1994, 138 patients underwent primary THA using a simple femoral component. Thirty-eight patients received a textured geometry while 50 were implanted with a HA coated stem and 50, a plasma sprayed stem. The hips were evaluated annually both clinically and radiographically. The results are reported using the Harris Hip Score and the Engh radiographic scale to determine the level of bone ingrowth and type of fixation.

Results: The average length of follow up is 8 years 11 months (range: 6 to 10 years). The average postoperative Harris Hip scores were 81.0% for the textured stems, 89.6 for the HA coated stems and 85.7 for the plasma sprayed stems. The revision rates are 13.2% for textured stems, 0% for HA and 5.4 % for plasma sprayed. Radiographic results show that fixation of the 3 surface coatings to be optimal in 100% of HA, 88.2% in plasma sprayed and 84.2% in textured.

Discussion and conclusion: At this point in the study, it is obvious that the coating enhancement of choice is hydroxyapatite. The next step in this research will be to match the HA coated stems with a comparable porous coated stem of the same design for further comparison.

The aim of the present study was to assess the outcome of revision surgery, using semiconstrained implants, in the management of tibiofemoral instability complicating primary total knee arthroplasty.

Between Feb 1987 and Oct 2000, 177 primary, unconstrained, surface replacement total knee arthroplasties were revised at our institution. Instability was the commonest reason for revision surgery and accounted for 22.6 % of overall revisions. Excluding tertiary referrals, instability necessitated revision surgery in 0.31% of 1918 primary total knee arthroplasties performed ‘in-house’ during the same period.

The results of 17 revision total knee arthroplasties using semiconstrained prostheses are presented. Six operations were performed for sagittal plane instability, 5 for coronal and 6 for multiplanar instability. 10 revisions were performed using the PFC ‘stabilised plus’ prostheses, and a further 7 with TC3 prostheses. 17 patients (13 F: 4 M), aged 48–83 years (average 67.8 years) underwent revisions, between 9–132 m from the date of the index arthroplasty. At an average follow-up of 36m, the Knee Society score had risen from 31.2 points preoperatively to 60.9 at last follow-up (LFU) [Joint score from 47.5 preop to 81.5 at LFU/Function score: from 14.4 to 39.7 at LFU]. Radiolucency rates were insignificant and at LFU no joints showed evidence of osteolysis, implant subsidence or polyethylene wear. One unresurfaced patella spontaneously fractured 10m postoperatively and one patella showed persistent subluxation. There were no other significant complications.

The present short term study attests to the efficacy of semi-constrained implants in the revision of unstable primary arthroplasties. However, in the longer term, implant longevity remains undetermined.