There is conflicting evidence about the merits of mobile bearings in total knee replacement, partly because most randomised controlled trials (RCTs) have not been adequately powered. We report the results of a multicentre RCT of mobile versus fixed bearings. This was part of the knee arthroplasty trial (KAT), where 539 patients were randomly allocated to mobile or fixed bearings and analysed on an intention-to-treat basis. The primary outcome measure was the Oxford Knee Score (OKS) plus secondary measures including Short Form-12, EuroQol EQ-5D, costs, cost-effectiveness and need for further surgery.

There was no significant difference between the groups pre-operatively: mean OKS was 17.18 (sd 7.60) in the mobile-bearing group and 16.49 (sd 7.40) in the fixed-bearing group. At five years mean OKS was 33.19 (sd 16.68) and 33.65 (sd 9.68), respectively. There was no significant difference between trial groups in OKS at five years (-1.12 (95% confidence interval -2.77 to 0.52) or any of the other outcome measures. Furthermore, there was no significant difference in the proportion of patients with knee-related re-operations or in total costs.

In this appropriately powered RCT, over the first five years after total knee replacement functional outcomes, re-operation rates and healthcare costs appear to be the same irrespective of whether a mobile or fixed bearing is used.

Cite this article: Bone Joint J 2013;95-B:486–92.

Purpose: To compare the survivorship, at 15 years, of cemented versus cementless fixation of press-fit condylar primary total knee replacements.

Methods: A prospective randomised consecutive series of 501 primary knee replacements received either cemented (219 patients, 277 implants) or cementless (177 patients, 224 implants) fixation. All operations were performed either by, or under the direct supervision of, a single surgeon (PJG). Patients were followed up to establish the rate of implant survival. No patients were lost to follow up. Revision was defined as further surgery, irrespective of indication, that involved replacement of any of the three original components. Life table analysis was used to assess survival. Cox’s proportional hazards regression analysis was used to compare the cumulative survival rates for the two groups.

Results: Altogether 44 patients underwent revision surgery (24 cemented vs. 20 cementless). 11 cases were revised secondary to infection, 26 were revised due to aseptic loosening and 7 cases were revised for other reasons (instability, anterior knee pain, polyethylene wear, patellar malallignment). At time of analysis a further 7 had revision planned.

For cemented knees 15-year survival=80.7% (95%CI, 71.5–87.4), 10-year survival=91.7 (95%CI, 87.1–94.8). For cementless knees 15-year survival=75.3% (95% CI, 63.5–84.3), 10-year survival=93.3% (95%CI, 88.4–96.2). There was no difference between these two groups.

When comparing the covariates (operation, sex, age, diagnosis, side), there was no significant difference between operation type (Hazard ratio=0.83 (95%CI, 0.45–1.52) p=0.545), side of operation (HR=0.58 (95%CI, 0.32–1.05) p=0.072), age (HR=0.97 (95%CI, 0.93–1.01) p=0.097), diagnosis (OA vs. non OA, (HR=1.25 (95%CI,0.38–4.12) p=0.718). However, there was a significant gender difference (Males vs. Females (HR=2.48 (95%CI, 1.34–4.61) p=0.004).

The worst case scenario was calculated to include those patients that have also been listed for revision. Cemented 15-yr survival = 78.3%, (95%CI, 68.9–85.4), cementless 15-yr survival = 72.0%, (95%CI, 59.9–81.5).

Conclusion: This single surgeon series, with no loss to follow up, provides reliable data of the revision rates of the most commonly used total knee replacement. The survival of the press-fit condylar total knee replacement remains good at 15 years irrespective of the method of fixation. This information is useful for strategic health authorities when establishing future requirements for revision knee surgery.

We have carried out a long-term survival analysis of a prospective, randomised trail comparing cemented with cementless fixation of press-fit condylar primary total knee replacements. A consecutive series of 501 replacements received either cemented (219 patients, 277 implants) or cementless (177 patients, 224 implants) fixation.

The patients were contacted at a mean follow-up of 7.4 years (2.7 to 13.0) to establish the rate of survival of the implant. The ten-year survival was compared using life-table and Cox’s proportional hazard analysis.

No patient was lost to follow-up. The survival at ten years was 95.3% (95% CI 90.3 to 97.8) and 95.6% (95% CI 89.5 to 98.2) in the cemented and cementless groups, respectively. The hazard ratio for failure in cemented compared with cementless prostheses was 0.97 (95% CI 0.36 to 2.6). A comparison of the clinical outcome at ten years in 80 knees showed no difference between the two groups.

The survival of the press-fit condylar total knee replacement at ten years is good irrespective of the method of fixation and brings into question the use of more expensive cementless implants.

We have analysed the Constant-Murley (1987) assessment for 25 patients with shoulder pathology. We found the score easy to use, with low inter- and intraobserver errors, but sufficiently imprecise in repeated measurements to give concern in its use for clinical follow-up of patients.

We have calculated 95% confidence limits for a single assessment to be within 16 to 20 points in most cases. In addition, we found that all our subjects with instability as their main problem scored within five points of the maximum; this suggests that the scoring method may need to be revised for use on these patients.