Magnetic Sphincter Augmentation (Linx Reflux Management System) for Treating Gastroesophageal Reflux Disease

Proprietary names: Linx® Reflux Management System (Models LX and LXM)

Generic names: magnetic esophageal ring implant, magnetic sphincter augmentation (MSA) device, gastroesophageal reflux implant, lower esophageal sphincter augmentation device

Gastroesophageal reflux occurs when the lower esophageal sphincter (LES) malfunctions and allows gastric acid into the esophagus.1 When reflux becomes chronic and causes symptoms, clinicians classify it as gastroesophageal reflux disease (GERD).2 GERD's most common symptoms are dysphagia, heartburn, regurgitation, and chest pain that may mimic cardiac pain. Most patients experience nighttime symptoms, which are often severe enough to interfere with sleep.3 Over time, acid reflux can cause bleeding and ulceration of the esophageal lining.1 The resulting scars can form strictures, which cause difficulty swallowing.1 GERD can also lead to Barrett's esophagus, a condition in which cells similar to the intestinal lining replace esophageal cells. These abnormal cells can develop into adenocarcinoma of the esophagus in a very small proportion of cases.1

Multiple factors may contribute to GERD onset.1,4 Anatomic disruption of the LES region due to a hiatal hernia, delayed gastric emptying, or increased abdominal pressure resulting from pregnancy or obesity can cause GERD by putting additional stress on the LES. Several medications (beta-agonists, nitrates, calcium channel antagonists, anticholinergics, progesterone) can also contribute by inducing LES relaxation. Diet does not play a role in LES malfunction; however, spicy or fatty foods, caffeine, alcohol, and smoking promote stomach acid production and may exacerbate GERD symptoms.1,4

GERD treatment depends on symptom severity. Clinicians typically treat patients experiencing moderate symptoms with medical therapy consisting of lifestyle modifications (e.g., avoidance of trigger foods, smoking cessation, weight loss) and anti-acid pharmacotherapy, such as proton pump inhibitors (PPIs).2 Clinicians consider PPIs (omeprazole, lansoprazole, esomeprazole) the preferred first-line GERD treatment.5 Other GERD medications include alkaline anti-acids (e.g., aluminum hydroxide, magnesium carbonate) and anti-secretory histamine-2 receptor antagonists (e.g., ranitidine, cimetidine, famotidine).4

Clinicians typically classify GERD as medically refractory if symptoms are still present after a two- to three-month medical therapy course.6 An estimated 10% to 40% of patients still have symptoms despite medical therapy; however, many of these patients have underlying conditions such as irritable bowel syndrome or gastroesophageal dismotility.1,7,8 Surgical treatments with varying levels of invasiveness are options for patients with primary GERD that does not respond to PPIs.1,7 The standard surgical treatment is Nissen fundoplication, in which surgeons wrap the upper part of the stomach around the LES to strengthen the sphincter.1,9. Another surgical option is magnetic sphincter augmentation (MSA) using the Linx Reflux Management System (Torax Medical, Inc., Shoreview, NN, USA), a laparoscopically placed implant intended to enhance LES function. If needed, surgeons can also repair an existing hiatal hernia during either fundoplication or MSA.9,10

Three minimally invasive technologies that address GERD are also available, but consensus is lacking on their role in the GERD clinical management pathway (see Complementary and Competing Technologies section for details).11-13 Proponents of transoral fundoplication, endoscopic LES thermotherapy, and LES neurostimulation intend these interventions as alternatives to long-term medication use in patients with chronic symptoms that respond at least partially to PPIs.11,14-17 Because these treatments involve anatomic or physiologic reinforcement of LES function, they might also constitute an alternative to fundoplication for treating refractory GERD.11,18 Nonetheless, endoscopic interventions do not allow correction of hiatal hernias that frequently underlie GERD and may not be useful in most cases of medically refractory GERD.

Richter et al. (1992)19 estimate 25% to 40% of people in the United States experience symptoms of GERD at some point in their lives and about 7% to 10% experience symptoms daily. These data may underestimate the actual number of people with GERD because many people manage symptoms with over-the-counter medications without consulting a physician. GERD occurs in all age groups, but prevalence increases in people age 40 years or older.20 Men and women are affected equally.20 Research indicates that GERD is highly prevalent in patients with obesity and that GERD prevalence has increased during the past two decades and will likely continue to increase because of the obesity epidemic.20,21 Based on results of cross-sectional and prospective studies, experts estimate that symptoms persist in about 30% (10% to 40%) of patients that take a standard once-a-day dose of PPI medication.22-25 Moreover, a large U.S. epidemiologic study (nearly 250,000 patients) reported that approximately 10% of patients with refractory GERD take a twice-a-day PPI dose.26

According to a 2014 systematic review including 29 epidemiologic surveys, GERD rates range between 18.1% and 27.8% in North America, 8.8% and 25.9% in Europe, 2.5% and 7.8% in East Asia, and 8.7% and 33.1% in the Middle East and are close to 11.6% in Australia and 23% in South America.27 The authors estimate GERD incidence to be approximately 5/1,000 person-years in the United States and the United Kingdom. The authors also concluded that GERD prevalence has increased in all regions since 1995.27

The Linx Reflux Management System is an implanted device intended for treating patients with medically refractory GERD.28 The Linx system consists of two single-use components: a series of titanium beads with magnetic cores connected by wires (i.e., the implant) and an esophagus sizing tool.28 The implant is placed around the distal esophagus so the magnetic attraction between the beads helps keep the LES closed. Pressure from swallowing is intended to overcome the magnetic attraction, stretching the device apart, and allowing food and liquid to pass normally.28 Clinicians can adjust the implant length by adding or removing beads to fit the patient's esophagus circumference.29

Surgeons place the Linx implant during a laparoscopic procedure, which generally lasts less than an hour.28 Patients require general anesthesia.28 First, the surgeon exposes the gastroesophageal junction and uses the esophagus sizing tool to determine the appropriate implant size (i.e., number of beads) for each patient.29 The surgeon then assembles the beads, wraps the implant around the outer muscle layer of the esophagus at the LES, and joins the ends of the implant using its suture tails.28 Patients typically go home the same day or within 48 hours without dietary restriction, and they usually resume nonstrenuous physical activity within a couple of days after surgery.28 Because the implant can trigger metal detectors or pose a hazard during high-intensity MRI (see Safety section), clinicians...