Magnetic Mini-Mover Procedure to Treat Pectus Excavatum (3MP)

This is a medical research study. The study investigators have developed a method to gradually repair pectus excavatum (sunken chest) deformity by placing a magnet on the sternum (breastbone) and then applying an external magnetic force that will pull the sternum outward gradually. Potential candidates for this study are children and adolescents with a previously diagnosed congenital pectus excavatum (sunken chest) deformity who are otherwise healthy and are seeking corrective surgery for their condition. They will be residents of the U.S. and between the ages of 8 and 14 years of age. Potential candidates and their families will have already been counseled about this condition and about the standard way to repair this deformity. The purpose of this study is to test what effects, good and/or bad, placing an external/internal magnetic device has on correcting pectus excavatum deformity in children, and the safety of using such a device for treatment.

Pectus excavatum is the most common congenital chest wall abnormality in children. Surgical correction requires a big operation under general anesthesia which forces the sternum forward and holds it in place using a metal chest wall strut. Deformation of the chest wall under great pressure may result in complications and potential relapses as well as postoperative pain requiring hospitalization for regional and narcotic anesthesia for up to a week. An alternative principle for correction of chest wall and other deformities is gradual (bit-by-bit) correction using minimal force applied over many months (like moving teeth with orthodontic braces). The hypothesis of this study is that constant outward force on the deformed cartilage in pectus excavatum will produce biologic reformation of cartilage and correction of the chest wall deformity. The study investigators have developed a novel method of achieving gradual deformation/reformation of chest wall cartilage without the need for transdermal orthopedic devices or repeated surgeries. A magnetic force field is used to apply controlled, sustained force to promote biologic reformation of structural cartilage (the same principle as distraction osteogenesis). A magnet is implanted on the sternum and secured using a novel fixation strategy that can be accomplished through a 3-cm subxyphoid incision as a brief 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 external magnet allows individual adjustment in small increments of the distance (and, thus, force) and orientation of the force applied to the sternum. The low-profile, non-obtrusive anterior chest wall prosthesis is held in place by the force field between the two magnets. The study objectives are to test the safety and probable benefit of this procedure in 10 otherwise healthy, young patients, between 8 years and 14 years of age, who have chosen to have this deformity corrected using this novel technique rather than the standard Ravitch or Nuss techniques. We will document the rate of correction by chest imaging and measurement of the Pectus Severity Index. The study investigators will document safety and efficacy with an EKG prior to implantation, one month post-implantation, and finally after the magnet is removed, as well as patient and family satisfaction with a post-procedure Quality of Life-type survey.

A rare earth magnet encased in FDA-approved titanium will be implanted securely on the outer surface of the lower end of the sternum in patients with pectus excavatum. This is accomplished as an outpatient procedure, under brief general anesthesia. A 2-inch transverse skinline incision is made at the junction of the sternum and xyphoid and the space in front and behind the sternum is dissected bluntly. The titanium can containing the magnet is securely fixed to the sternum by screwing it into a titanium fixation disk in front of the sternum. The procedure takes 1/2-hour, and the patient can go home the same day. In another outpatient procedure, the Magnimplant is explanted 18 months after implantation.

An external orthotic device "Magnatract" which includes an external magnet in a removable brace is fitted specifically to the patient's chest wall deformity. A calibrated meter in the external device measures the force applied between the two magnets. When the patient and family are comfortable with the device and comfort and skin condition have been assessed, the patient will be allowed to take the Magnatract home and begin the process of gradually advancing the sternum forward as the abnormal costal cartilage is reformed.

Subject has EKG performed to measure baseline cardiac activity. Magnimplant is implanted. After one week, "Magnatract" is fitted. Chest x-ray and 2nd EKG performed 30 days post-implantation. Patient and parents complete QoL questionnaire 30d post-implantation. Patient seen weekly for first month post-implantation to assess comfort and skin condition. Thereafter, will be seen monthly. At each monthly visit, patient will have lateral and anterior-posterior chest X-rays to monitor sternal correction. At each visit data logger is downloaded to measure strength of pull since last visit and amount of wear-time. Magnimplant explanted 18 months later as 1/2-hr outpatient procedure. CT scan and third EKG performed after explanation. Patient and parents complete QOL questionnaires after explantation and 1 yr post-explantation.

EKG performed prior to implantation, one month post-implantation, and after explanation to evaluate whether magnetic field near the heart adversely affects cardiac activity. Outcome measure describes number of patients who experienced adverse change in EKG.

Outcome measure is number of patients who experienced permanent skin damage or discoloration due to external brace wear

Based on patient response to one-year post-explantation QoL questionnaire: How satisfied are you with the correction of your chest? Ratings: 5-very satisfied; 4-satisfied; 3-unsure; 2-dissatisfied; 1-very dissatisfied

Based on patient response to one-year post-explantation QoL statement: "I would recommend this treatment for pectus excavatum (sunken chest) to someone else with pectus excavatum." Ratings: 5-strongly agree; 4-agree; 3-unsure; 2-disagree; 1-strongly disagree

Compliance measured by average number of hours per day external device was worn by patient, as measured by the data sensor and logging device built into external prosthetic

Residents of the United States with previously diagnosed pectus excavatum who are referred to the UCSF Pediatric Surgery Service for evaluation and treatment will be considered for participation in this study. Only patients with moderate to severe pectus excavatum who meet all the inclusion criteria will participate. The patient and family will be fully counseled and consented about the risks and benefits of participation in the study, and will be asked to sign an informed consent reviewed and approved by the UCSF Committee on Human Research. Inclusion Criteria: Resident of the U.S.; Otherwise healthy male or female with pectus excavatum deformity; Between 8 and 14 years of age; Pectus Severity Index > 3.5 (normal 2.56); and Ability to read and speak English. 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; Inability to obtain pre-approval (authorization) from the patient's insurance carrier; and Inability or refusal to return to UCSF for weekly follow-up visits for the first month after surgery.

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