Pediatric Spine Foundation

Title: Proximal anchor fixation in magnetically controlled growing rods (MCGR): preliminary 2-year results of the impact of anchor location and density

Authors: Blake C. Meza, Suken A. Shah, Michael G. Vitale, Peter F. Sturm, Scott J. Luhmann, Pediatric Spine Study Group, Jason B. Anari

Journal: Spine Deformity

Date: March 18, 2020

Excerpt: When using MCGR, proximal spine anchors and greater anchor density impart superior deformity correction but do not significantly impact the risk of device complications.

Keywords: Proximal anchor, magnetically controlled growing rods (MCGR), early-onset scoliosis (EOS)

Summary:

Purpose

During the surgery to insert Magnetically Controlled Growing Rods (MCGR), device placement can be attached to the spine or ribs. Previous studies have found that in a similar device, Traditional rowing Rods (TGR), attaching to the rib has less chance for rod breakage and having 5 or more locations of attachment makes the risk of device migration or movement less likely. This study aims to review the impact of the location and number of anchors at the top of the device in the treatment of early onset scoliosis with MCGR.

Results

  • This study included 155 MCGR patients. Most patients with <5 attachments at the top of the device had spine-based anchors (74.7%), while a majority of those with =5 attachments at the top of the device were rib-based (51.4%).
  • Spine-based devices were associated with less kyphosis and better curve correction compared to rib-based devices. Overall, the difference in average patient curve correction was 6.8° (23.9° vs. 17.1°) for major curves, 5.5° (10.0° vs. 4.5°) for minor curves, and 10.7° for kyphotic curves.
  • A greater amount of attachments together (=5 attachments at the top) was found to have more major curve correction at 2 years (25.0° vs. 18.2°). Having =5 attachments at the top did not make the complication risk notably lower, including device movement where it was attached (8.4% vs. 7.7%).
  • Device movement was more common with rib-based devices (13.8% vs. 4.1%) and rod breakage was more common with spine-based devices (10.3% vs. 3.4%), however this trend was not notably different after statistical review.

Discussion Points

  • Spine-based devices had more improvement of spinal deformity.
  • Having =5 attachments at the top did not change the risk of complications; but it was associated with greater 2-year curve improvement.
  • The median follow-up time of patients in this study is less than 3 years. Future studies should continue to follow these patients to determine long-term outcomes and complications.