Total knee arthroplasty at 15-17 years: does implant design affect outcome?

Abstract

Purpose: A study was conducted to compare minimum 15-year survivorship and outcome of the Genesis I and II implants for total knee arthroplasty (TKA).

Methods: We retrospectively reviewed 245 consecutive TKA implanted between January 1995 and October 1997. Genesis I was implanted in 156 knees and Genesis II in 89 knees.

Results: At 15-17 years, 75 patients (31%) had died, 28 patients (11%) were lost to follow-up and 11 TKA were revised (4.6%), including ten Genesis I (6.4%) and one Genesis II (1.1%); 131 TKA (53%) were available for follow-up. Cumulative survivorship was 92.4% at 15.7 years. Survival in patients <69 years at surgery was lower (88.0%) compared with patients ≥69 years (98.5%; p = 0.023). In patients <69 years, Genesis I survival (84.3%) was worse compared with Genesis II (97.1%) (p = 0.018). Polyethylene (PE) Insert thickness ≤11 mm had significantly better survivorship (97.1%) compared with PE >11 mm (56.7%) (p < 0.0001) CONCLUSIONS: At a minimum of 15 years, the overall (92.4%) survivorship of Genesis TKA was good, with excellent (98.1%) survivorship of the Genesis II design. Revision rates were higher with Genesis I in the younger age group and with insert thickness >11 mm, possibly due to longer shelf life of less frequently used sizes.

Fig. 1

Polyethylene (PE) thickness of medial and lateral compartments measured on anteroposterior radiographs. The estimated amount of linear wear was calculated by deducting the measured thickness, corrected for magnification, from the initial PE thickness, as disclosed by the manufacturer

Fig. 2

All patients: dead, lost, revised and available for 15–17 years’ follow-up in the global population and in the Genesis I (Gen I) and Genesis II (Gen II) cohorts

Fig. 3

Survivorship in the Genesis I group was 90.1 % at 15.5 years [95 % confidence interval (CI) 88.0 – 92.2) and in the Genesis II group 98.1 % at 15.0 years (95 % CI 97.8 – 98.3). The difference was not statistically significant (Log rank 3.136; p = 0.077)

Fig. 4

Total knee arthroplasty (TKA) survival in patients <69 years (overall median age) at surgery was significantly worse [88.0 % at 15.4 years; 95 % confidence interval (CI) 85.8 – 90.4] compared with patients ≥69 years at surgery (98.5 % at 15.9 years; 95 % CI 97.4 – 99.6); p = 0.023

Fig. 5

Survival with polyethylene (PE) thickness >11 mm [56.7 % at 14.0 years; 95 % confidence interval (CI) 49.5–62.9] was significantly worse compared with PE thickness ≤11 mm (97.1 % at 15.9 yearsl; 95 % CI 96.5 –97.7); p < 0.0001