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Outcomes Related to the Use of Standard-Standard versus Standard-Offset Magnetically Controlled Growing Rods
Simon Blanchard1, Thomas A Coleman1, Jacob Jordan1
1Orthopedics Center, Children's Hospital of Philadelphia, Philadelphia, PA.
Background:
Magnetically controlled growing rods (MCGRs) are used to perform growth-friendly spinal deformity correction. A key variable that remains debated in determining the optimal use of MCGRs is the orientation of the rods: parallel to one another (standard-standard) versus antiparallel (standard-offset). This study aims to determine if the orientation of the rods has an impact on lengthening outcomes and complication rates.
Methods:
A retrospective analysis of an international multicenter prospective registry of early-onset scoliosis patients was conducted. Inclusion criteria were patients who underwent bilateral MCGR index surgery with available lengthening data for a minimum of 2 years. Lengthening analyses were discontinued following revision or exchange of the implants. Accumulated programmed and actual lengthening was recorded at the first visit, 2-year, and 5-year intervals following index surgery.
Results:
Six hundred sixty-eight patients met the inclusion criteria for the study, including 327 females (49%) and 341 males (51%) patients who were 8.0±1.9 years old at index surgery, with a mean major coronal curve of 74 degrees (18 to 134 degrees). Three hundred twenty-three (48%) patients received standard-standard and 345 (52%) patients received standard-offset MCGRs. Patients with standard-standard rods experienced complications at a similar rate to patients who received standard-offset rods [n=137 (42%) vs. n=128 (37%); P=0.161]. In terms of achieved lengthening, no differences were found across actuator orientations at the first lengthening, or in the achieved lengthening accumulated by patients who were still undergoing lengthening procedures at 2 or 5 years post-implantation.
Conclusions:
The lengthening achieved and complication risks are similar across rod orientations at 2 and 5 years. At 2 years post-index surgery, surgeons appear to be attempting to lengthen patients who receive standard-offset rods to a greater extent without any additional clinical benefit. Further investigation is needed to further elucidate the best practices of MCGR utilization and to determine which patients would benefit from one orientation compared with the other.
Level Of Evidence:
Level 3.
