The clinical and functional outcomes after total knee arthroplasty (TKA) are generally very favorable. The 15% to 20% of subpar patient-reported outcomes are usually related to persistent pain. Orthopaedic researchers have exhaustively investigated patient factors and technical considerations to address dissatisfaction in this minority population of TKA patients.
Meanwhile, the orthopaedic community has focused on prosthetic design in its attempts to incrementally improve outcomes for the 80% to 85% of generally satisfied TKA patients. Clearly documenting those incremental improvements often requires elegant study design. That’s what we see in the January 6, 2021 issue of The Journal, where Kim et al. report findings from a randomized trial in which 2 different knee-implant designs were compared in the same patients after primary simultaneous bilateral TKA.
Each of the 50 patients (49 of them women) received a posterior-stabilized design in 1 knee and an ultracongruent prosthesis in the other. Kim et al. selected the Forgotten Joint Score (FJS) as the primary outcome. The FJS is a 12-item questionnaire that assesses patient awareness of the artificial joint during daily activities. At 2 years, the researchers found no between-knee differences in FJS. The ultracongruent knees showed more anteroposterior laxity and less femoral rollback than the posterior-stabilized knees, but there were, again, no between-group differences in following measures:
- Range of motion
- Knee Society and WOMAC scores
- Side Preference and patient satisfaction
The ultracongruent advancement in prosthetic design does not appear to offer clinically important advantages over the posterior-stabilized design. But if additional TKA patients can be recruited into studies using clever and effective experimental designs like this one, the future is bright for more robust assessments of the incremental impact of prosthetic design on functional and clinical outcomes.
Click here to view an Infographic summarizing this study.
Marc Swiontkowski, MD