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How Large a Study Is Needed to Detect TKA Revision Rate Reductions Attributable to Robotic or Navigated Technologies?
Matthew D Hickey1, Carolyn Anglin2, Bassam Masri3
1School of Biomedical Engineering, the University of British Columbia, Vancouver, BC, Canada.
Clinical Orthopaedics and Related Research
|August 5, 2021
Summary
Technology-assisted total knee arthroplasty (TA-TKA) may offer a small survival benefit, but detecting this requires very large randomized trials. The number needed to treat to prevent one revision is high, questioning broad adoption based on revision costs alone.
Area of Science:
- Orthopedic surgery
- Biomedical engineering
- Clinical trial design
Background:
- Robotic and navigated total knee arthroplasty (TKA) aim to improve component placement precision and implant survivorship.
- Despite enhanced precision, most comparative studies show no significant improvement in implant survival rates.
- The magnitude of potential benefits necessitates evaluating the required scale of randomized trials.
Purpose of the Study:
- To determine the necessary sample size and follow-up duration for randomized trials to detect small differences in survivorship between technology-assisted TKA (TA-TKA) and conventional TKA.
- To assess the clinical significance of potential survivorship improvements offered by TA-TKA.
Main Methods:
- A simulation study using estimated effect sizes from registry and clinical studies.
- Modeled 1.5 million simulated TKA cases with patient-specific factors and assigned coronal alignment precision.
- Conducted Monte Carlo simulations (3000 populations) to evaluate power across different cohort sizes and follow-up periods (1-25 years).
Main Results:
- Simulations indicated survivorship differences favoring TA-TKA of 1.4%–2.0% at 15 years.
- Detecting these differences requires 2500–4000 patients per arm in randomized trials with 80% power.
- The number needed to treat (NNT) to prevent one revision ranged from 1000 at 2 years to 50 at 15 years for the most precise interventions.
Conclusions:
- TA-TKA may offer a relative reduction in revision rates, but the absolute benefit is small and realized over a long follow-up period.
- Traditional randomized controlled trials (RCTs) would need excessively large patient numbers and long follow-up to demonstrate these small benefits.
- High NNTs suggest that broad adoption based solely on avoided revision costs may not be justified without considering system costs and patient risk factors.
