Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation...

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Biomaterials Science

Background:

• Aseptic tibial loosening is a common failure mode in primary total knee arthroplasty (TKA).
• The exact mechanisms leading to aseptic loosening remain incompletely understood despite technological advancements.
• This study investigated the role of intraoperative knee motion during cement curing on tibial implant fixation.

Purpose of the Study:

• To test the hypothesis that knee motion during cement polymerization disperses lipids and weakens tibial fixation.
• To quantify the effect of motion on tibial implant pull-out strength.
• To compare fixation strength across different TKA implant designs.

Main Methods:

• A cadaveric study using 32 torso-to-toe specimens (64 knees) and four contemporary TKA designs.
• Tibial components were cemented using standard techniques.
• One knee per pair was immobilized during cement polymerization; the contralateral knee underwent gentle range of motion.

Main Results:

• The no-motion cohort exhibited significantly higher average pull-out strength (5,462 N) compared to the motion cohort (4,473 N) (P = .001).
• Significant variations in pull-out strength were observed between different implant designs within both cohorts.
• Failures at the implant-cement interface showed lower pull-out strength than bone failures.

Conclusions:

• Knee motion during cement polymerization significantly reduces tibial implant fixation strength in TKA.
• The detrimental effect of motion on fixation strength was consistent across all tested implant designs but varied in magnitude.
• Minimizing tibial component motion during cement curing is recommended to enhance fixation strength and potentially reduce aseptic loosening.