Actuator pin fracture in magnetically controlled growing rods: two cases

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Pediatric spine deformities

Background:

• Magnetically controlled growing rods (MCGRs) are utilized for non-invasive treatment of early-onset scoliosis (EOS).
• These devices employ a telescopic actuator stimulated by an external remote controller for outpatient lengthening.
• MCGRs offer a less invasive alternative to traditional growing techniques for managing spinal deformities in children.

Observation:

• This report details two cases of MCGR failure attributed to lengthening pin fractures in dual-rod constructs.
• A 12-year-old boy experienced a "popping" sensation and grating, leading to the discovery of a fractured pin.
• Review of other patients revealed bilateral fractures in an asymptomatic girl, indicating a potential subtle failure mode.

Findings:

• The study identified lengthening pin fracture as a subtle cause of MCGR failure in dual-rod systems.
• Radiographic evaluation is essential for diagnosing this specific type of implant failure.
• Bilateral fractures were observed, suggesting a potential systemic issue with the implants or surgical technique.

Implications:

• Clinicians must maintain a high index of suspicion for implant failure in patients with suggestive symptoms or unsuccessful distractions.
• Prompt radiographic evaluation and review of prior imaging are recommended upon suspicion of MCGR failure.
• Regular radiographic follow-up (every 6 months) is advised for centers using ultrasound to monitor MCGR lengthening, ensuring implant structural integrity.