This study is a Phase 3, multicenter, non-randomized study to evaluate the safety and efficacy of the next-generation outpatient Magnetic Mini-Mover Procedure (3MP) in 15 patients aged 8-14 years for the correction of pectus excavatum ('sunken chest'). 3MP for pectus excavatum uses a magnetically coupled implant to pull the sternum forward and gradually remodel the deformed costal cartilage. The Funding Source for this trial is the FDA Office of Orphan Products Development (Grant #R01 FD003341).

Pectus excavatum is the most common congenital chest wall abnormality in children. The investigators have developed a novel method of achieving gradual deformation/reformation of chest wall cartilage. A magnetic force field is used to apply controlled, sustained force to promote biologic reformation of structural cartilage. A magnet is implanted on the sternum and secured through a 2-inch subxiphoid incision as a one-hour outpatient procedure. The magnet (and sternum) is pulled outward by another magnet suspended in a novel, low-profile, lightweight device previously molded to the patient's anterior chest wall. The low-profile, non-obtrusive anterior chest wall prosthesis is held in place by the force field between the two magnets.

In the single-center, FDA-funded trial (IDE G050196), the investigators tested proof of concept, safety and probable benefit of this procedure in 10. In this Phase III multicenter trial, the investigators will further test the safety and efficacy of the procedure in 15 otherwise healthy patients with moderate-to-severe PE, ages 8 to 14. The investigators will be using the next generation Magnetic Mini-Mover Magnimplant device (IDE G090006), a design the investigators believe is much improved in terms of safety and ease of implantation/explantation. Implantation of the Magnimplant will be accomplished in an outpatient procedure. The investigators will document the rate of correction by comparing chest X-ray measurement of the Pectus Severity Index prior to implantation, to that measured after the magnet is removed. Treatment will last 18-24 months, depending on correction and when the patient has completed his or her pubertal growth spurt, as documented by hand x-ray. Explant of the device will be accomplished in an outpatient procedure. The investigators will document safety with an EKG prior to implantation, one month post-implantation, and finally after the magnet is removed. The investigators will document efficacy by comparing pre- and post-treatment PSI, as well as by evaluating patient satisfaction with a post-procedure Quality of Life-type survey. Long-term follow-up will occur at 6, 12, 18, and 24 months after explantation.

Inclusion Criteria:

• Otherwise healthy male or female with pectus excavatum deformity
• Between 8 and 14 years of age (inclusive)
• Pectus Severity Index > 3.5 (normal 2.56). NOTE: A pectus severity index of 3.5 or greater qualifies as a moderate-to-severe deformity, and justifies operative intervention
• Ability to read, speak and understand English
• Onset of rapid growth of puberty documented by hand/wrist x-ray in early to mid-puberty (defined as bone age in females of 7-13 years, and males of 9-14 years)

Exclusion Criteria:

• Other congenital anomalies (including significant skeletal anomalies such as scoliosis, bony fusion involving the cervical vertebrae) not directly related to pectus excavatum
• Bleeding disorders
• Heart disease (including arrhythmia)
• Persons with active implantable medical devices (AIMD) such as pacemakers
• Persons with a relative(s) or close family friend(s) living within their households and having a pacemaker
• Persons with arteriovenous malformations
• Chest deformity more complicated than pectus excavatum (e.g., Poland syndrome)
• Persons for whom a foreign body implant would pose a risk (e.g., immunodeficiency)
• Persons at increased risk for general anesthesia (e.g., history of malignant hyperthermia)
• Respiratory conditions that have required steroid treatment (e.g., prednisone) in the last 3 years
• Pregnancy
• Inability to understand or follow instructions
• Refusal to wear the external brace
• Refusal to undergo monthly chest x-rays
• Inability or refusal to return to UCSF for biweekly follow-up visits for the first month after surgery, and monthly thereafter until explant.
• Inability to obtain pre-approval (authorization) from the patient's insurance carrier

The end results will be published in Journal of Pediatric Surgery June 2017

2 years