Magnetic Mini-Mover Procedure for pectus excavatum IV: FDA sponsored multicenter trial.

PURPOSE: The Magnetic Mini-Mover Procedure (3MP) is a minimally invasive treatment for prepubertal patients with pectus excavatum. This multicenter trial sought to supplement safety and efficacy data from an earlier pilot trial. METHODS: Fifteen patients with pectus excavatum had a titanium-enclosed magnet implanted on the sternum. Externally, patients wore a custom-fitted magnetic brace. Patients were monitored closely for safety. Efficacy was determined by the Haller Index (HI) and satisfaction surveys. After 2 years, the implant was removed. RESULTS: Mean patient age was 12 years (range 8-14), and mean pretreatment HI was 4.7 (range 3.6-7.4). The device was successfully implanted in all patients. Mean treatment duration was 25 months (range 18-33). Posttreatment chest imaging in 13 patients indicated that HI decreased in 5, remained stable in 2, and increased in 6. Seven out of 15 patients had breakage of the implant's titanium cables because of fatigue fracture. Eight out of 13 patients were satisfied with their chest after treatment. CONCLUSION: The 3MP is a safe, minimally invasive, outpatient treatment for prepubertal patients with pectus excavatum. However, the magnetic implant design led to frequent device breakage, confounding analysis. The HI indicated mixed efficacy, although surveys indicated most patients perceived a benefit. STUDY TYPE/LEVEL OF EVIDENCE: Case series, treatment study. Level IV.

Magnetic mini-mover procedure for pectus excavatum III: safety and efficacy in a Food and Drug Administration-sponsored clinical trial.

PURPOSE: The magnetic mini-mover procedure (3MP) uses magnetic force to gradually remodel pectus excavatum deformity. A magnet is implanted on the sternum and coupled with an external magnetic brace. Under Investigational Device Exemption and Institutional Review Board approval, we performed a pilot study of safety, probable efficacy, and cost-effectiveness of this new treatment of an orphan disease using an implantable pediatric device. METHODS: Ten otherwise healthy patients, ages 8 to 14 years, with severe pectus excavatum (pectus severity index [PSI] > 3.5) underwent 3MP treatment (mean, 18.8 ± 2.5 months). Safety was assessed by postimplant and postexplant electrocardiograms and monthly chest x-rays. Efficacy was assessed by change in pectus severity index as measured using pretreatment and posttreatment computed tomographic scan. Cost of 3MP was compared with that of standard procedures. RESULTS: The 3MP device had no detectable ill effect. Device weld failure or malpositioning required revision in 5 patients. Average wear time was 16 h/d. Pectus severity index improved in patients in the early or mid puberty but not in patients with noncompliant chest walls. Average cost for 3MP was $46,859, compared with $81,206 and $81,022 for Nuss and Ravitch, respectively. CONCLUSION: The 3MP is a safe, cost-effective, outpatient alternative treatment for pectus excavatum that achieves good results for patients in early and midpuberty stages.

Magnetic mini-mover procedure for pectus excavatum II: initial findings of a Food and Drug Administration-sponsored trial.

PURPOSE: The Magnetic Mini-Mover Procedure (3MP) uses a magnetic implant coupled with an external magnet to generate force sufficient to gradually remodel pectus excavatum deformities. This is an interim report of the evolution of the 3MP during a Food and Drug Administration-approved clinical trial. METHODS: After obtaining Institutional Review Board approval, we performed the 3MP on 10 otherwise healthy patients with moderate to severe pectus excavatum deformities (age, 8-14 years; Haller index >3.5). Operative techniques evolved to improve ease of implantation. Patients were evaluated monthly by a pediatric surgeon and orthotist. Electrocardiograms were performed pre- and postoperatively. Sternal position was documented by pre- and postprocedure computed tomographic scan, interval chest x-ray, depth gauge, and interval photographs. RESULTS: There was no detectable effect of the static magnetic field on wound healing or cardiopulmonary function. No detectable injuries and minimal skin changes resulted from brace wear. Operative techniques evolved to include a custom sternal punch and a flexible guide wire to guide the posterior plate into position behind the sternum, reducing outpatient operating time to one-half hour. In 9 patients, the procedure was performed as an outpatient basis; and 1 patient was observed overnight. Three patients required evacuation of retained pleural air postoperatively, and 2 required an outpatient revision. A custom-fitted orthotic brace (Magnatract) was extensively modified to increase user friendliness and functionality while incorporating several novel functions: a screw displacement mechanism so patients can easily self-adjust magnetic force, a miniature data logger to measure force and temperature data every 10 minutes, and an interactive online Web portal for remote patient evaluation. All attempts to quantitate sternal position (radiographic, fluid volume, and depth gauge) were inadequate. Visual assessment remains the best indicator. CONCLUSIONS: In this interim report, the 3MP appears to be a safe, minimally invasive, outpatient, cost-effective alternative treatment of pectus excavatum. Outcomes will be reported upon the completion of this phase II clinical trial.

Magnetic Mini-Mover Procedure for pectus excavatum: I. Development, design, and simulations for feasibility and safety.

BACKGROUND/PURPOSE: Correction of pectus excavatum (PE) results in measurable improvement in lung capacity and cardiac performance as well as improved appearance and self-image. The Nuss and modified Ravitch approaches attempt to correct the chest wall deformity by forcing the sternum forward in 1 step and holding it in place using a metal strut. The initial operation requires extensive manipulation under general anesthesia and results in postoperative pain, requiring hospitalization and regional anesthesia. Pain and disability may last for weeks. Both procedures are expensive. A better principle would be a gradual bit-by-bit repair via small increments of pressure applied over many months. We developed the Magnetic Mini-Mover Procedure and applied this strategy to correct PE. METHODS: The Magnetic Mini-Mover Procedure uses magnetic force to pull the sternum forward. An internal magnet implanted on the sternum and an external magnet in a nonobtrusive custom-fitted anterior chest wall orthosis produce an adjustable outward force on the sternum. Outward force is maintained until the abnormal costal cartilages are remodeled and the pectus deformity is corrected. RESULTS: We implanted a magnet in human skeletons and measured the force applied to the sternum when the distance between the internal and external magnets was varied in increments. With the 2 magnets 1 cm apart, the outward force was adequate to move the sternum at least 1 cm. We also mapped the magnetic field in the two-magnet configuration and found that maximum field strengths at the surface of the heart and at the outer surface of the orthosis were at safe levels. CONCLUSIONS: The Magnetic Mini-Mover Procedure allows correction of PE by applying magnetic force over a period of months. Crucial questions raised during our design, redesign, and simulation testing have been satisfactorily answered, and we have received a Food and Drug Administration Investigation Device Exemption (G050196/A002) to proceed with a phase I to II clinical trial.