Magnetic expansion control system achieves cost savings compared to traditional growth rods: An economic analysis model

Alvin W. Su, Todd A. Milbrandt, A. Noelle Larson

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Study Design. Medical economic model with multi-way sensitivity analysis. Objective. To compare the direct costs of growing rod (GR) versus Magnetic Expansion Control System (MG) from a payer's perspective. We hypothesized that over time the MG will become more cost-effective. Summary of Background Data. Traditional GRs provide effective treatment, but require periodic lengthening surgery. MG allows rod lengthening in clinic, but the implant is expensive. The cumulative cost savings are not well understood. Methods. Index surgery, implant cost, lengthening procedure, and revision surgery due to implant failure or infection were identified as major parameters contributing to the cumulative cost. The "base," "low," and "high" values for the cost and the incidence of each parameter were determined by literature reports, health care database search, or expert consultation. The cumulative cost was compared annually during 5 years of follow-up. Marginal cost was defined as the cost of (GR-MG) for each cumulative year. Final cumulative cost and extreme case scenario at year 5 were assessed by deterministic sensitivity analysis. Results. MG resulted in higher cumulative cost at years 1 and 2, and became lower cost at years 3 through 5. The marginal cost at year 1 was a negative value of $16K, and trended toward positive values of $12K at year 3 and $40K by year 5. Sensitivity analysis revealed that in extreme case, MG could cost more, shown by a marginal cost of $26K by implementing the extreme values of the 3 parameters carrying highest variance: MGinfection management, GR-revision surgery, and GR-lengthening procedure. Conclusion. MG achieved cost neutrality to GR at 3 years after index surgery. This is the first medical economic study in the United States comparing the cost of GR versus MG and demonstrates potential cost-effectiveness of MG from payer's perspective if in place for more than 3 years.

Original languageEnglish (US)
Pages (from-to)1851-1856
Number of pages6
Issue number23
StatePublished - 2015


  • Cost analysis
  • Direct cost
  • Early-onset scoliosis
  • Growing rod
  • Magnetic Expansion Control System
  • Magnetic controlled rod
  • Medical decision making
  • Medical economic model
  • Spine
  • Spine complication
  • Spine deformity
  • Spine nonfusion surgery

ASJC Scopus subject areas

  • Clinical Neurology
  • Orthopedics and Sports Medicine


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