Magnetically activated growing rods can be lengthened externally with the patient awake in the outpatient setting. Reproduced from Cahill PJ, Pahys JM, Van Bosse HJP, Samdani A: Placement of Bilateral Magnetically Activated Growing Rods (video) Rosemont, IL, American Academy of Orthopaedic Surgeons, 2015.

AAOS Now

Published 1/1/2016
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Peter Pollack

An Attractive Alternative: Magnetic Growing Rods

Study looks at cumulative costs of scoliosis treatment over 5 years
"Most orthopaedic surgeons who treat patients with early onset scoliosis use traditional growing rods, which allow for spinal growth and deformity control," said Todd Milbrandt, MD, addressing members of the Scoliosis Research Society during their 2015 annual meeting. "However, such systems require regular surgical lengthening, which may be linked with increased risk of infection and additional stress to the patient.

"The use of magnetic growing rods allows for rod lengthening in clinic, but the implant is very expensive and cumulative cost savings are not well understood," he continued. "A recent French study projected that the cost between the magnetic growing rods and traditional growing rods may be similar about 4 years after implant, and we hypothesized that this may be true in the United States as well."

To investigate the issue, the research team developed a medical economic model that combined implant cost, index surgery, lengthening surgery, implant failure, and infection as the major components of the cumulative treatment cost. In addition, they invented a three-way sensitivity analysis to address a "worst case" cost scenario for each implant type.

"We used literature, database information, and expert consults to determine the direct costs," explained Dr. Millbrandt.

Initial charges
For the index procedure, the researchers estimated the cost to payers to be approximately $38,000 for the magnetic rod system and $9,000 for traditional growing rods. The cost of lengthening surgery was estimated to be $10,000. The research team compared cumulative costs each year through 5-year follow-up. Costs for infection management were based on published literature and expert opinion. They defined marginal cost as the estimated cumulative cost of traditional growing rods minus the estimated cumulative cost of magnetic growing rods.

"The initial costs of surgery are significantly larger for magnetic rods compared to traditional rods," said Dr. Millbrandt. "Also, if revision surgery is necessary, it is more expensive to replace one rod in the magnetic rod system compared to traditional rods. However, over time, the difference in the cost of lengthenings favored the use of magnetic rods.

"Based on our model, costs would be significantly higher for the magnetic rod system in year 1. By year 2, the cost levels become much more even; by year 3, magnetic rods are less expensive than traditional rods, and by years 4 and 5, the difference in cost to payers significantly favors the use of magnetic rods."

Dr. Milbrandt noted, however, that in the "worst-case" scenarios, magnetic growing rods could be associated with greater cost in the longer-term.

Magnetically activated growing rods can be lengthened externally with the patient awake in the outpatient setting. Reproduced from Cahill PJ, Pahys JM, Van Bosse HJP, Samdani A: Placement of Bilateral Magnetically Activated Growing Rods (video) Rosemont, IL, American Academy of Orthopaedic Surgeons, 2015.
Before and after radiographs showing impact of lengthening. Reproduced from Cahill PJ, Pahys JM, Van Bosse HJP, Samdani A: Placement of Bilateral Magnetically Activated Growing Rods (video) Rosemont, IL, American Academy of Orthopaedic Surgeons, 2015.

"With traditional growing rods, it's the lengthening surgeries that add up," he said. "With magnetic rods, the cost of revision surgery is higher, and that can offset the difference. Using our three-way sensitivity analysis to examine the worst-case scenario, we determined that magnetic rods would be $26,000 more expensive than traditional rods."

Variability, perspectives
Dr. Milbrandt pointed out several limitations to the study. The research team found substantial variability in certain costs as reported in existing literature, making cost assessment difficult. In addition, a lack of published data meant that some costs had to be estimated. Finally, little published evidence exists on complications when using magnetic growing rods.

"In addition," he said, "this research reflects a payer's perspective. It does not cover societal costs such as children's missing schooldays, parents' taking off work, and traveling. However, from the payer's perspective, the magnetic system achieves cost neutrality at about 3 years after the index surgery. Thereafter, magnetic rod systems become more cost-effective than traditional growing rod systems."

Dr. Milbrandt's coauthors are Alvin W. Su, MD, PhD, and A. Noelle Larson, MD. Disclosure information for the authors can be accessed at www.aaos.org/disclosure

Peter Pollack is electronic content specialist for AAOS Now. He can be reached at ppollack@aaos.org

Bottom Line

  • Although magnetic rods are initially more expensive, the reduced cost of lengthenings appears makes them more cost-effective than traditional growing rods over time.
  • In a "worst-case" revision situation, however, the higher cost of magnetic rod revision surgery favors traditional rods.
  • This study estimated expense from a payer perspective and did not address societal costs.

References:

  1. Jevsevar DS, Brown GA, Cummins DS, Donnelly P. Viscosupplementation for Osteoarthritis of the Knee: A Systematic Review of the Evidence. J Bone Joint Surg. [need to complete when online after 12/16]
  2. Slavin RE. Best-evidence synthesis: an alternative to meta-analytic and traditional reviews. Educ Res. 1986;15(9):5–11.
  3. Rutjes AW, Jüni P, da Costa BR, Trelle S, Nüesch E, Reichenbach S. Viscosupplementation for osteoarthritis of the knee: a systematic review and meta-analysis. Ann Intern Med. 2012 Aug 7;157(3):180–191.
  4. Colen S, van den Bekerom MP, Mulier M, Haverkamp D. Hyaluronic acid in the treatment of knee osteoarthritis: a systematic review and meta-analysis with emphasis on the efficacy of different products. BioDrugs. 2012 Aug 1;26(4):257–268
  5. Jevsevar D. The Importance of Clinical Significance in AAOS Clinical Practice Guidelines, AAOS Now, May 2013.

Additional Information:
Magnetic Expansion Control System Achieves Cost Savings Compared to Traditional Growth Rods: An Economic Analysis Model