Hybrid Versus Cemented TKA Using the NexGen LPS Prosthesis

Condition(s) studied

Investigational drug(s) / intervention(s)

Total knee arthroplasty: Use of an uncemented femoral component or a cemented femoral component randomly assigned.

NEXGEN LPS total knee arthroplasty: Hybrid (non cemented femoral component, cemented tibial component) NEXGEN LPS total knee arthroplasty versus Cemented NEXGEN LPS total knee arthroplasty (both components are cemented).

Study summary

Early total knee arthroplasty (TKA) implant systems most frequently used an all-polyethylene cemented tibial component1. Based on finite-element analysis studies reporting superior force distribution compared with conventional all-polyethylene components, metal-backed tibial baseplates have dominated the TKA implant market since the middle of the 1980's2. These modular implants provided excellent long-term implant survivorship3.

As TKA became increasingly successful, younger patients increasingly became eligible. Increasing life expectancy has raised the concern that cemented TKAs may not withstand prolonged use, particularly in younger patients4. Patients younger than 65 years are projected to account for more than 50% of patients undergoing TKA by 2016 and to more than 50% of patients undergoing revision surgery by 2011. The number of total knee revisions in the United States is expected to increase from 38,300 in 2005 to 268,200 in 20305.

Many authors have reported excellent and equivalent results of cemented and cementless TKA6-8. Despite these encouraging reports, the major concern with cementless TKA has been the tibial component, and, therefore, the preference for many surgeons still remains to cement the tibial component9,10. The femoral component may be the most suitable for cementless fixation11-13. However, the best femoral method of fixation is still being discussed. Currently, the decision to cement or not to cement the femoral component is based on the surgeon's preference14.

The current study was designed to compare the hybrid NexGen LPS (Zimmer Inc, Warsaw, IN) and the cemented NexGen LPS. The purpose of this study is to establish whether the hybrid NexGen LPS leads to equally successful results as the cemented TKA gold standard

Eligibility

Primary outcome measure(s)

• Postoperative functional outcome as measured by the Knee and Osteoarthritis Outcome Score (KOOS) and compare if hybrid NexGen LPS TKA leads to equally successful results as the cemented NexGen LPS TKA. — 1 year
  The current study will be designed as equivalence trial. The amount of allowable difference is the margin that defines the "zone of indifference" within which the interventions are considered equivalent. The KOOS has a Minimally Clinically Important Difference (MCID) of 8 - 10 points, and the standard deviation in a cohort of TKA patients is ca. 15 points. The null hypothesis (of non-equivalence) of the study is that functional outcome at 10 years of follow-up in the hybrid group is not equal to the functional outcome at 10 years of follow-up in the cemented group, or: H: ϑ ≤ ϑ0 - δ1 or ϑ ≥ ϑ0 + δ1, versus the equivalence assumption that functional outcome at 10 years of follow-up in the hybrid group is equivalent to the functional outcome at 10 years of follow-up in the cemented group: K: ϑ0 - δ1 \< ϑ \< ϑ0 + δ1.

Trial sites (1)