Are the long term results of a high-flex total knee replacement affected by the range of flexion?

Abstract

Purpose: The purpose of this study was to examine the effect of deep flexion on the long-term durability of a high-flex ceramic implant in total knee arthroplasty.

Methods: Five hundred and five consecutive knees replaced with a Bi-Surface knee system (Kyocera Medical, Osaka, Japan) were divided into two groups according to the range of flexion by 135° postoperatively. Comparison of implant durability was made between the high- and low-flexion groups after a minimum ten year follow-up.

Results: With revision for any surgery as the end point, the survival rates at ten years were 95.5% and 96.2% in the high- and low-flexion group, respectively (p = 0.63). With revision for mechanical failure as the end point, survival rates were 98.7% and 98.5%, respectively (p = 0.94).

Conclusion: Implant survival rate was similar for both groups. Deep flexion seemed not to affect long-term durability.

Fig. 1

Posterolateral view of the Bi-Surface knee system. The unique ball-and-socket joint is seen in the midposterior portion of the tibiofemoral joint

Fig. 2

Mean range of flexion and standard deviation (SD) over time for both groups. The red line with square dots (■) and the blue line with triangles (▲) indicate high- and low-flexion groups, respectively. Asterisk (∗) and dagger (†) indicate statistical significance (p < 0.05) for time periods and between groups, respectively

Fig. 3

a, b Survival rates with revision for any surgery or radiographic failure as the end point (a) and with revision for mechanical failure as the end point (b). Red and blue lines indicate high- and low-flexion groups, respectively. No significant differences were found

Fig. 4

a, b Survival rates with revision for any surgery or radiographic failure as the end point (a) and with revision for mechanical failure as the end point (b), divided into small increments. No significant differences were found