An increasing number of younger patients are now receiving a TKR2. According to one study, TKR utilization in persons younger than 60 years of age has increased more than 20-fold in 20 years2. Cemented TKR provides excellent early fixation, and has generally been considered as the gold standard for implant survivorship1. However, increased life expectancy and higher quality of life mean that younger patients put greater demand and stress on their prostheses1. There is, as a result, some debate as to the optimal TKR fixation in younger patients, with some evidence that the biological fixation afforded by cementless implants can deliver superior long-term results compared to cemented implants1. This meta-analysis of recently published RCTs examined the optimal mode of fixation in younger TKR patients.
Six RCTs met the inclusion criteria with 255 patients in the cemented groups and 229 in the cementless groups1. The RCTs were published between 2006 and 2014, and the duration of follow-up ranged from 2 to 16.6 years1.
Radiological outcomes & pain scores
According to the literature, progressive radiolucent lines in TKR can be associated with loosening, implant instability or migration1. In the present meta-analysis significantly better radiological outcomes were observed in the cementless groups than in the cemented groups (p = 0.034) 1.
Residual pain following TKR is a significant clinical problem, with up to 50% of patients reporting moderate to severe postoperative pain1. TKR studies have shown that “there is a close relationship between radiolucent lines and continual moderate knee pain1.” This relationship was evidenced in the current study, which reported significantly better pain scores following cementless TKR than cemented TKR (p = 0.005) 1. “The overall quality of evidence was high, which indicated that further research is unlikely to alter confidence in the effect estimate1.”
In explanation of these findings a subsequent publication suggested that the cementless components provide a stronger and more durable implant fixation, while the cemented components show signs of gradual mechanical loosening over time3. This loosening may be minor initially, but eventually leads to micromotion of the tibial component and pain3.
In the literature aseptic tibial loosening rates of 0 to 1% have been reported for cementless components compared to 1 to 12% in cemented components1. Interestingly in the current meta-analysis, no between group differences were observed for aseptic loosening1. Nor were there any significant differences in functional outcome (KSS) or post-operative complications including deep infection and reoperation1.
According to another RCT published in 20203, differences in function between cemented and cementless TKR are time-dependent. The authors noted that the cementless group maintained their median OKS and KSS at each interval whereas the same scores for the cemented group gradually decreased over time, with the difference becoming significant at the final follow-up (at minimum 11 years) 3. In this meta-analysis only 2 of the 6 RCTs included reported on follow-up beyond 11 years1. This may help to explain why there were no significant differences in function observed in the current study.