How much does depth matter? Magnetically controlled growing rod distraction directly influenced by rod tissue depth

Area of Science:

• Spine surgery
• Pediatric orthopedics
• Biomechanical engineering

Background:

• Magnetically controlled growing rods (MCGRs) offer innovative treatment for early-onset scoliosis (EOS).
• While MCGRs present advantages over traditional growing rods, understanding their limitations and potential complications is crucial.
• Tissue depth's influence on MCGR performance remains an area requiring further investigation.

Purpose of the Study:

• To investigate the impact of tissue depth on the lengthening accuracy of magnetically controlled growing rods (MCGRs) in EOS patients.
• To quantify the relationship between tissue depth and the achieved rod distraction.
• To identify factors influencing MCGR performance and potential complications.

Main Methods:

• Retrospective review of 72 patients with EOS treated using MCGRs.
• Ultrasound measurement of rod distraction to compare programmed versus actual lengthening.
• Analysis of tissue depths, achieved length, and complication rates.

Main Results:

• Rod lengthening was inversely proportional to tissue depth; a 1mm increase in depth reduced lengthening by 1.46% (standard) and 1.68% (offset).
• Deeper tissue correlated with less achieved lengthening, indicating a significant biomechanical effect.
• Complications occurred in 38.9% of patients, but tissue depth, age, sex, or BMI did not significantly predict them.

Conclusions:

• Tissue depth is a critical factor affecting magnetically controlled growing rod (MCGR) lengthening in early-onset scoliosis (EOS) treatment.
• Surgical planning for MCGR placement should consider tissue depth to optimize distraction and potentially mitigate complications.
• Further research may explore strategies to overcome the lengthening limitations imposed by deeper tissue depths.