The MSA device of the LES (LINX^®, Torax Medical, Shoreview, MN) is made up of a series of magnetic beads that are interconnected by a titanium wire and allow for expansion depending to the applied pressure. The device is placed around the esophagogastric junction and applies magnetic force in order to enhance the antireflux barrier function[12]. When the beads are closed, this magnetic force is approximately 40 g, however when fully distanced they apply much less force, approximately 7 g. As a result, the device allows the bolus during swallowing to pass the esophagus and it also allows the release of elevated gastric pressure, which is associated with belching or vomiting. On the other hand, it is highly unlikely that during digestion or at rest, the stomach would generate enough force to open the device. Consequently, the LINX^® device augments the LES at rest and prevents inappropriate transient relaxation[13].

Regarding technical information, the LINX^® reflux management system is laparoscopically inserted at the level of the gastroesophageal junction, with the pharyngoesophageal ligament preserved. At rest, this innovative apparatus encircles the gastroesophageal junction resembling a “Roman arch” with each bead resting against its neighbor thus preventing esophageal compression. In addition, each magnetic bead can move independently of the alongside beads in an intention to imitate normal esophageal motility. This is of critical importance as this machine responds to the movements of the esophagus rather than restrains them thus averting compression that may lead to erosion. Also, it has displayed significant reproducibility, safe side effect profile and minimal disruption of anatomy. Moreover, after the procedure, fibrous tissue forms around the MSA device, outside the esophageal wall and the diaphragmatic crura, thus enabling removal without endangering esophageal damage[13]. The system is FDA approved for magnetic resonance imaging up to 1.5 T in new generation systems, while older versions are compatible with magnetic resonance imaging up to 0.7 T[14]. Patients usually stay in the hospital for 1 d, with some centers performing LINX^® as an outpatient procedure. Upon discharge, patients are instructed to return on a normal diet with frequent small volume meals, chew their meals well and discontinue any previous PPI therapy[13,15].

Non-obese patients with GERD confirmed by 24 h ambulatory pH monitoring and persisting symptoms after maximized medical therapy should be offered to proceed with the LINX^® surgical procedure[14]. Officially, BE exclusion in endoscopy and confirmation of normal esophageal motility in manometry, are considered strong requirements for MSA implantation. Regarding hiatal hernias (HH), those smaller than 3 cm are verified as a clear indication for the procedure[14,16].

Obesity [Body mass index (BMI) > 35 kg/m²] may prevent anticipated positive outcomes after LINX^® implantation[17]. Therefore, patients with obesity and confirmed GERD should be advised to lose weight before LINX^® becomes a viable option. Although FDA considered usage of LINX^® in large HH (> 3 cm) a “precautions”, increasing evidence exist that large HH are not a contraindication, therefore more studies are needed to better elucidate these results[18]. Moreover, if a HH greater than 3 cm is detected during the operation for LINX^® implantation, it is strongly recommended to repair it before device insertion[12]. Patients with advanced esophagitis or esophageal dysmotility are also excluded[13]. An allergy to titanium, stainless steel, nickel and ferrous materials is an indisputable barrier to LINX^® placement[14]. LINX is a relatively new treatment option in GERD, therefore many of the contraindications mentioned are a consequence of not extensively testing the safety and effectiveness of LINX in these patient groups. Thus, as LINX^® system is more and more implanted and evaluated, BE, larger HH and mild esophageal motility disorders are not considered as contraindications.

Concerning the studies presented in table 1, after excluding duplicate patient populations, our literature research revealed a total of 1539 MSA patients, with 1452 of them being followed up for a period ranging between 1 and 80 mo. Most studies (15/20) had a follow-up of over 12 mo. The mean age and BMI of patients ranged between 39.3-54 years and 24-28 kg/m², respectively. Seven studies were comparative between MSA and LF. These studies are additionally discussed in a different section bellow.

The mean OR time ranged between 27-73 min. A hospital length stay ranging between 13-100 h was reported. The most common complication was mild dysphagia, which occurred in 6%-83% of patients. In case of persistent dysphagia, balloon dilation was performed as an initial treatment approach, which occurred in 8% of patients. Additionally, in 2% of patients, device removal was required, due to dysphagia or recurrent heartburn/regurgitation or esophageal wall erosion. The device removal procedure occurred uneventfully in all of them. Regarding the results of MSA implantation as a therapeutic approach to GERD, between 75% and 100% of patients, depending on the study, stayed PPI free after surgery. Moreover, their DeMeester score ranged between 33.4 and 49.5 pre-operatively, while dropping to 11.2-15.6 post-operatively. The mean GERD health-related quality of life (GERD-HRQL) score pre-operatively was in the 11-27 range while post-operatively dropped in the 0-6 range.

Aiolfi et al[37], conducted a meta-analysis of the 7 comparative studies mentioned in the literature. This 2018 study included a total number of 1211 patients, 686 MSA and 525 LF. There was no incidence of death in either group; however postoperative morbidity was more frequent among patients who underwent LF (0-3% in the MSA group and 0-7% in the LF group). The operative time was longer for the LF group compared to MSA group (42-73 min in the MSA group and 76-118 in the LF group). Severe dysphagia treated with endoscopic dilatation occurred in 9.3% of MSA patients and 6.6% of LF patients, a difference though not statistically significant. In addition, their results demonstrated a strong association between MSA and less bloating symptoms (P < 0.001), a greater ability to vomit (P < 0.001) and belch (P < 0.001). There was no statistically significant difference between PPI suspension and reoperation rates[37]. Similarly, in another meta-analysis of 6 comparative studies conducted in 2019, statistically significant differences occurred only in belching and bloating, whereas there were no statistically significant differences in GERD-HRQL, PPI suspension and dysphagia[38].

Aiming to examine the safety profile of the MSA device, Lipham et al[39], designed a study which analyzed all the available data of the first 1000 patients who underwent MSA at 82 institutions worldwide. Median implant duration was 274 d and the results showed that intra/perioperative complications occurred in 0.1% of patients, 1.3% needed readmission and endoscopic dilations were noted in 5.6% of patients. Furthermore, 3.4% of patients were re-operated, but no reoperation for device removal was performed emergently and there was no intraoperative complication or conversion into laparotomy. No device migrations or malfunctions were noted and erosion occurred in one patient (0.1%). The overall event rates were low and this analysis confirms the safety of this device and the MSA technique[39].

In the same direction, Smith et al[40] developed a subsequent study collecting data from the Manufacturer and User Facility Device Experience database between 2012 and 2016. The study included a total number of 3283 patients. Overall incidence of device removal was 2.7% while 88% of the removals occurred within 2 years after surgery, with no complications[40]. In addition, a single-center cohort study estimated the device’s safety examining reoperations for MSA removal out of 164 patients who underwent LINX^® implantation. In total, 11 patients (6.7%) were explanted for a variety of reasons mostly between 12 and 24 mo after the index procedure. The main symptom indicating need for device removal was recurrence of heartburn or regurgitation in 46%. During device removal surgeons also performed partial fundoplication and there were no conversions to laparotomy or long-term complications[41].

Upon some years of clinical application, recent studies considered and evaluated the efficacy and safety of alternative surgical strategies. Tatum et al[42] collected data of 182 patients who underwent MSA with the LINX^® device at a single center between December 2012 and November 2016. Minimal hiatal dissection (MHD) at the diaphragmatic hiatus was used as the operative technique for MSA between December 2012 and September 2015 (n = 96), whereas all patients (n = 86) between September 2015 and 2016 were managed with obligatory dissection (OD). Mean follow-up time was 554 d for MHD group and 374 for OD group and mean hernia size according to intraoperative measurements was 0.77 cm for the MHD group compared to 3.95 cm for the OD group. At 1-year follow-up, both groups showed similar results in postoperative dysphagia; however, recurrent GERD symptoms were more frequent after MHD compared to OD (16.3% vs 3.6%, respectively). Recurrent hiatal hernia of 2 cm or greater occurred in 11.5% of patients in the MHD group, while no patient in OD group presented with this complication. Consequently, the study strongly indicated that OD of the hiatus during implantation of the device with crural closure has more favorable outcomes and results in decreased recurrence of GERD symptoms and hiatal hernia[34]. Moreover, Alnasser et al[42] focused on the need to obtain alternative access to implant the LINX^® devices for patient with certain criteria; the authors described two cases that underwent MSA through left thoracotomy due to previous abdominal surgeries. They highlighted that a trans-thoracic approach is a feasible, alternative strategy for MSA[42].

Laparoscopic Sleeve Gastrectomy in bariatric patients has been associated with new-onset or worsening of GERD symptoms[43]. In general, a BMI > 35 kg/m² is negatively associated with excellent/good outcomes in MSA implantation[17]. However, upon losing weight, bariatric surgery patients become suitable candidates for LINX^® procedure. Although our literature research revealed only 3 studies with a total of 33 bariatric patients (26 on follow-up) being assessed, the results seem very promising. The clinical and demographic characteristics of bariatric patients with MSA devices are presented in Table 2.

The most common bariatric procedure was laparoscopic sleeve gastrectomy (LSG). The mean BMI of bariatric patients upon MSA implantation was reported to be 30.1 and 33 in two studies, with one of them reporting a BMI upper limit of 44, which is over the usual indications[45,46]. Moreover, one of the studies implementing LINX^® on 13 LSG patients reported 100% satisfaction and a drop of GERD-HRQL score from 17-18 to 5-6[44]. In addition, although the vast majority of patients (28/33) had undergone LSG prior to MSA implantation, 1 out of 3 studies reported 4 Laparoscopic Roux-en-Y Gastric Bypass patients and 1 Duodenal Switch patient. The study reported 100% patient satisfaction rates[46]. For a better delineation of these results, further studies, with larger patient populations, are needed.

Rona et al[47] reviewed a series of 192 patients with a median follow-up time of 20 months. Among these patients 52 (27%) presented with a large hiatal hernia (≥ 3 cm). These patients reported reduced postoperative PPI’s use compared to patients with smaller hernias (9.6 vs 26.6 %, respectively) and the mean GERD-HRQL score was improved (3.6 vs 5.6, respectively). In both groups, the majority of patients reported complete resolution of GERD symptoms[47]. The authors also analyzed and published the recurrent rate of hiatal hernia in a total of 47 patients with large (> 3 cm) hiatal hernia who were managed with laparoscopic repair combined with MSA. GERD-HRQL score was improved (from 20.3 to 3.1) and resolution of reflux symptoms was achieved in 97% of patients. Recurrence of HH occurred in 2 patients (4.3%) at a mean of 18 mo postoperatively[48]. In the same direction, Buckley et al[18] reviewed 200 patients with HH who were treated with MSA. 78% of patients appeared with hiatal hernia ≥ 5 cm and most of them (83%) were managed with non-permanent mesh reinforcement of the hiatus. Postoperatively, GERD-HRQL scores were significantly decreased (from 26 at baseline to 2) and complete cessation of PPI use was achieved in 94% of patients. Consequently, the authors indicated that hernia size does not affect the safety and efficacy of MSA[18].

A randomized controlled trial of 152 patients compared the MSA procedure with double-dose PPI medication for the treatment of moderate-to-severe GERD. Study inclusion criteria were participants aged > 21 years, having moderate-to-severe GERD and taking a daily single dose of PPI therapy for at least 8 wk. The rest of the inclusion criteria were similar to the typical indications of MSA implantation. The active seeking of participants for alternative, surgical treatments was a prerequisite. The results of the study indicated that the MSA implantation is superior to increased PPI medication, and patients with moderate-to-severe GERD should be recommended MSA implantation instead of double PPI doses[49].

Esophageal erosion is regarded as the most dreadful complication of the LINX^® procedure. A study collected data from 9453 device implantations all over the world. The data were obtained from the device manufacturer, Torax Medical and included records of devices implanted until 2017. The risk of esophageal erosion from the device increased from 0.05% at 1 year to 0.3% at 4 years. All of the devices were removed successfully, and in a median follow-up of 1.9 mo, 24/29 patients had returned to baseline and were symptom free[50].

Although many studies evaluating the safety and efficacy of LINX have emerged, our literature research revealed only two studies assessing the cost-effectiveness of MSA[35,51]. The first study retrieved data from 2 institutions and compared MSA with LNF regarding surgical admission charges. It concluded that the increased cost of MSA is completely counteracted by its shorter operative time and length of stay ($48491 vs $50111, P = 0.506)[35]. The second study retrieved data from patients in Western and Central Pennsylvania, the Lehigh Valley, West Virginia, and the border areas of eastern Ohio[51]. The cost analysis revealed that MSA has a higher same-day procedural payer cost than LNF ($13522 vs $13388, P = 0.02), which may partially be offset by a decreased need for hospital stay in MSA. Furthermore, in a follow-up of 12 mo, a higher reduction in disease-related costs was observed in the MSA group compared to the LNF group (65.9% vs 46%, P = 0.0001).

Gastroesophageal reflux disease (GERD) refers to the reflux of stomach contents causing troublesome symptoms and/or complications. When medical therapy is insufficient, surgical therapy is needed and, until now, Laparoscopic Fundoplication (LF) is the gold-standard method.

Magnetic sphincter augmentation (MSA) using the LINX^® reflux management system has recently appeared and questions standard treatments.

The purpose of this review is to investigate the device’s safety and efficacy in resolving GERD symptoms.

Our systematic review based on the PRISMA guidelines. From inception to September 2019, we searched Medline, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL databases.

Overall, a total of 35 studies were included in a total of 2511 MSA patients. Post-operative proton-pump inhibitor (PPI) cessation rates reached 100%, with less bloating symptoms and a better ability to belch or vomit in comparison to LF. Special patient groups (e.g., bariatric or large hiatal-hernias) had promising results too. The most common postoperative complication was dysphagia ranging between 6% and 83%. Dilation due to dysphagia occurred in 8% of patients with typical inclusion criteria. Esophageal erosion may occur in up to 0.03% of patients. Furthermore, a recent trial indicated MSA as an efficient alternative to double-dose PPIs in moderate-to-severe GERD.

The findings of our review suggest that MSA has the potential to bridge the treatment gap between maxed-out medical treatment and LF. However, further studies with longer follow-up are needed for a better elucidation of these results.

MSA with the LINX^® device is considered a safe procedure with excellent results. When compared with the gold standard, LF, MSA seems to have similar efficacy and safety profiles. Nonetheless, it also has some distinct advantages. These include shorter operative time, less technical variability, less interventions on the normal anatomy, less bloating symptoms and a better ability to belch or vomit. Moreover, promising results comparing the MSA procedure with double-dose PPIs in moderate-to-severe GERD exist. Overall, the results of our review enforce the notion that the MSA procedure has the potential to bridge the treatment gap between maxed-out dose of medical treatment and LF.