Abstract
Patients suffering from chronic mechanical low back pain secondary to multifidus dysfunction represent a unique and increasingly recognized subset of the overall chronic mechanical low back pain population. Neuromuscular inhibition and fatty infiltration of the dysfunctional multifidus muscle contribute to persistent pain, spinal instability, and disability that fail to resolve with conventional therapy. As of October 2024, the introduction of the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) code M62.85 provides formal classification of this disease entity and allows providers to diagnose this condition with a higher level of specificity. Permanently implanted restorative neurostimulation systems, of which the ReActiv8 device (Mainstay Medical) is currently the only US Food and Drug Administration (FDA)–approved technology (FDA Product Code QLK), directly target chronic low back pain associated with lumbar multifidus dysfunction to treat the underlying condition. This 2025 International Society for the Advancement of Spine Surgery guideline update (1) summarizes the high-quality clinical data supporting long-term efficacy and safety of restorative neurostimulation, including longitudinal outcomes from a 5-year pivotal study, randomized controlled trials, and other clinical studies, (2) updates all coding guidance to reflect current ICD-10 and FDA device status, and (3) reports on payer trends, including the recent positive Anthem Blue Cross Blue Shield coverage decision. The International Society for the Advancement of Spine Surgery reaffirms its support for coverage of implantable restorative neurostimulation by payers in appropriately selected patients, consistent with the demonstrated evidence.
Introduction
Since the 2023 International Society for the Advancement of Spine Surgery (ISASS) Statement,1 new International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) coding; long-term level I evidence; positive payer decisions; and expanded recognition of multifidus dysfunction’s prognostic and economic impact make an updated guideline essential to align coverage criteria with current science and practice.
Objective
The goal of this guideline recommendation is to provide an update to the ISASS 2023 guideline statement on surgical and device-based management of lumbar spine dysfunction, focusing on restorative neurostimulation for chronic low back pain associated with multifidus dysfunction.1 This update incorporates the emergence of ICD-10-CM M62.852 and new data, including long-term clinical outcomes and multiple real-world evidence studies, along with recent payer and coding developments, to offer comprehensive medical necessity and coverage guidance for US payers and providers for implantable restorative neurostimulation.
Device Neutrality
ISASS maintains a device-neutral position in all guideline statements. At the time of publication, the ReActiv8 system3 (Mainstay Medical; PMA P190021, Product Code QLK) is the only US Food and Drug Administration (FDA)-approved restorative neurostimulation technology for lumbar multifidus dysfunction. Future devices that obtain equivalent regulatory approval and demonstrate comparable safety and efficacy should be evaluated using the same evidence-based criteria.
Background
Chronic mechanical low back pain (CLBP) or nociceptive low back pain linked to multifidus muscle dysfunction is a treatment-resistant condition with a high personal and economic burden. Restorative neurostimulation targets the motor fibers of the medial branch of the dorsal ramus to elicit isolated lumbar multifidus contractions, aiming to restore neuromuscular control and spinal stability. This mechanism differs from ablative or sensory neuromodulation approaches.
Clinical Relevance
Lumbar multifidus muscle dysfunction is a structural and physiological driver of CLBP whose diagnosis and management have historically been underrecognized. The multifidus, as the principal stabilizer of the lumbar spine, is susceptible to neuromuscular inhibition due to injury, pain, and degenerative conditions, resulting in disuse, muscle atrophy, segmental instability, and recalcitrant symptoms that can fail conservative management and become chronic. Magnetic resonance imaging and ultrasound often reveal muscle fatty infiltration and degeneration in affected patients. Conservative therapies, including physical rehabilitation, injections, and medications, typically do not restore neuromuscular control or muscle quality when the inhibition reaches a chronic state. As a result, many patients progress to long-term opioid use and seek repeated palliative interventions, such as injections and ablations, which fail to address the underlying cause, leading to severe disability and excessive health care resource utilization. This distinction with palliative procedures is critical: whereas many existing therapies provide temporary symptom relief, restorative neurostimulation represents a proactive, disease-modifying approach that restores neuromuscular function. This places it in alignment with curative or corrective strategies rather than maintenance or masking approaches.
The restorative neurostimulation therapy delivers targeted bilateral motor stimulation to the lumbar multifidus via the medial branch of the dorsal ramus at L2. Restorative neurostimulation facilitates motor rehabilitation as the mechanism leading to pain relief and improved function, rather than merely masking symptoms for sustained pain relief, function improvement, and increased quality of life as demonstrated in 2 randomized controlled trials (RCTs),4,5 multiple real-world evidence clinical studies,6–8 and mechanism of action studies.9,10
Technical Description
Restorative neurostimulation (ReActiv8; Mainstay Medical) consists of a fully implantable device indicated for the treatment of adult patients with severe CLBP attributed to multifidus dysfunction. The system consists of an implanted pulse generator and 2 percutaneous leads, each placed adjacent to the L2 medial branch of the dorsal ramus at the L3 vertebral level.1 The indicated therapy includes two 30-minute stimulation sessions in which the patient controls the timing of the stimulation. The device delivers bilateral electrical pulses that induce functional contraction of the multifidus muscle. This enhances neuromuscular drive, progressively reversing inhibition and degeneration. The implantable device and leads are designed for chronic, multiyear stimulation and are controlled to minimize the risk of off-target stimulation or adverse events.
Summary of Clinical Evidence
Numerous clinical studies and reviews, including 2 RCTs and multiple real-world evidence studies, are summarized in the Table. The restorative neurostimulation therapy demonstrated safety, effectiveness, durability in 5-year follow-up, and reproducibility in 2 controlled trials and 4 real-world evidence studies. Six studies that reported at minimum 1-year results, 2 studies reported 5-year results, and several additional publications that studied the same patients longitudinally at various time intervals. All 6 studies achieved meaningful functional improvement and pain decrease, achieving minimal clinically important change for patients treated with restorative neurostimulation.
Summaries of published studies’ clinical findings related to restorative neurostimulation.
The 2 RCTs and scoping reviews are summarized below. The correlation of fatty infiltration in predicting surgical outcomes after spinal surgery used to treat other spinal pathologies is also reviewed, accentuating the clinical importance of restorative neurostimulation for addressing multifidus dysfunction. Additional studies, including a systematic review, are summarized in the Table.
Long-Term Efficacy (5-Year Pivotal Data)
The pivotal study was a prospective, multicenter, randomized, sham-controlled study enrolling patients with refractory CLBP and documented multifidus dysfunction who had failed conservative management.4 At a 5-year follow-up, 72% of patients sustained ≥50% reduction in back pain visual analog scale from baseline, 61% achieved ≥20-point Oswestry Disability Index improvement, and opioid use was reduced or eliminated in a large majority. Improvements were durable and consistent throughout 5 years, a landmark in neurostimulation device-based CLBP interventions.14
RESTORE Trial
The RESTORE trial was published in early 20255 as a multicenter RCT comparing restorative neurostimulation therapy treatment to Optimized Medical Management for treatment of CLBP. At the 12-month follow-up, patients randomized to the treatment group experienced a mean reduction of -19.7 points in Oswestry Disability Index, a −3.6 reduction in NRS back pain, and a +0.16 improvement in EQ-5D-5L quality of life. All primary and secondary endpoints were met vs Optimized Medical Management, and the safety profile was very favorable.5
Systematic Review
A recent systematic review synthesized data from RCTs, prospective cohorts, and registries, concluding that implantable restorative neurostimulation delivers consistent and clinically meaningful reductions in disability and pain with very low rates of device-related adverse events and broad clinical applicability for patients meeting inclusion criteria.13
Patient Compliance and Satisfaction
Equally important, restorative neurostimulation demonstrates high patient adherence, with real-world registry data confirming low explant rates and strong satisfaction scores. This distinguishes it from other implantable pain therapies, where compliance and tolerance may diminish long term.7
Economic Impact
Economic analyses, though limited, indicate that restorative neurostimulation may reduce overall spine care costs by lowering reoperation rates, minimizing chronic opioid dependence, and decreasing utilization of repeat injections and other palliative procedures. For payers, this positions restorative neurostimulation not only as clinically necessary but as a cost-offsetting intervention in appropriately selected patients.18,26
Correlation of Pre-existing Multifidus Fatty Infiltration and Patient-Reported Outcomes After Spine Surgery
The literature is replete with the negative effects of pre-existing multifidus fatty infiltration on patient-reported long-term outcomes. For patients undergoing laminectomy for stenosis, fusion, or lumbar total disc arthroplasty, the outcomes of these procedures are negatively impacted in the presence of fatty infiltration in the multifidus in comparison to patients who do not have this condition.27–30 Therefore, spine surgeons should be informed of this condition and consider restorative neurostimulation for the treatment of multifidus dysfunction in properly selected patients in the absence of clear surgical indications.1
Indications/Limitations of Coverage
Coverage Indications
Implantable restorative neurostimulation therapy is medically necessary in adult patients with all of the following:
Documented multifidus dysfunction, lumbar region (ICD-10 M62.85) confirmed by imaging (magnetic resonance imaging and/or ultrasound) findings, and clinical presentation.
CLBP with failed ≥6 months of comprehensive, guideline-driven conservative management.
No clear indications for spine surgery (eg, progressive neurologic deficit, spinal instability, and severe stenosis).
Older than 18 years.
Limitations of Coverage
Exclusions apply if any of the following apply:
Severe spinal instability or deformity requiring surgical reconstruction.
Contraindications to lead or pulse generator implantation.
Active infection or coagulopathy.
Coding
ICD-10-CM Diagnosis Coding
M62.85: Dysfunction of multifidus muscles and lumbar region.
FDA Device Coding
Product Code QLK: Stimulation of nerves that innervate muscles to treat or aid in the management of chronic, intractable lower back pain.3
Current Procedural Terminology Coding
Current procedural interventions can be reported using the following codes:
64590: Insertion of replacement of peripheral, sacral, or gastric neurostimulator pulse generator or receiver, requiring pocket creation and connections between the electrode array and the pulse generator or receiver.
64555 × 2: Percutaneous implantation of neurostimulator electrode array; peripheral nerve (excludes sacral nerve).
Payer Policy Trends
Since the adoption of ICD-10-CM code M62.85, payers have shifted in their approach to multifidus dysfunction. The coding specificity has enabled precise patient identification, and accumulating long-term data has reinforced payer confidence. Regional and national carriers have issued positive coverage determinations or initiated policy revisions, reflecting growing recognition of restorative neurostimulation as medically necessary. Anthem Blue Cross Blue Shield’s 2025 decision marking restorative neurostimulation as medically necessary for defined patient populations signals a broader shift across payers. Other commercial payers and certain Medicare Administrative Contractors are also covering.
Limitations of Evidence
Current evidence is strongest in non-surgical patients with mechanical/nociceptive pain and confirmed multifidus dysfunction; further study is warranted in postsurgical and neuropathic populations.
While long-term clinical outcomes are well documented, economic analyses remain limited and should be expanded to strengthen cost-effectiveness assessments.
Conclusion
Patients with CLBP due to multifidus muscle dysfunction represent a high-need population with limited effective treatment options. Restorative neurostimulation—delivered by an implantable system designed to re-activate the lumbar multifidus muscle—is now supported by multiple level I RCTs, long-term follow-up extending to 5 years, and real-world evidence studies demonstrating consistent, durable improvements in pain, disability, opioid use, and quality of life. With the addition of ICD-10-CM coding (M62.85) to define this condition and with expanding payer recognition, restorative neurostimulation has matured into a validated, durable, and economically relevant therapy. ISASS affirms that coverage criteria should align with this body of evidence and urges payers to adopt positive policies enabling appropriate patient access. As with all guidelines, ISASS will continue to review emerging data, including physiological markers and economic analyses, to ensure guidance remains evidence based, patient focused, and fiscally responsible.
Acknowledgment
The authors thank Frank Phillips for his review of this guideline.
Footnotes
Funding The authors received no financial support for the research, authorship, and/or publication of this article.
Disclosures Morgan P. Lorio and Kai-Uwe Lewandrowski have nothing to report. William Lavelle reports grants/contracts from Abryx, Cerapedics, Empirical Spine, Medtronic, Spinal Kinetics, Vertebral Technologies, 3 Spine, Synergy, and Orthofix (all paid to institution); consulting fees from 4-Web and DePuy Spine; patents for DePuy Spine; serving on the Innovasis Scientific Advisory Board, Vertiflex Advisory Board, and TruSpine Medical Advisory Board; and stock/stock options from 4-Web and Expanding Innovations. David Essig reports consulting fees from SI-Bone, DePuy, and Stryker. James Yue reports royalties/licenses from Royal Biologics, consulting fees from High Ridge Spine and Elliquence, payment/honoraria from Arthrex and Abbott, participation on a Data Safety Monitoring Board or advisory board for Medtronic and Intrinsic Spine, and serving as a CPT panel delegate for ISASS. John Ratliff has nothing to report. Anthony DiGiorgio reports grants or contracts from DePuy Synthes (to the Charles Koch Foundation) and Florida Essential Healthcare Partnerships; support for attending meetings and/or travel from the American Association of Neurological Surgeons; and a leadership or fiduciary role for the San Francisco Marin Medical Society, the California Association of Neurological Surgeons, and the International Society for the Advancement of Spine Surgery. Richard Kube has nothing to report. Kris Radcliff reports royalties/licenses from Globus; consulting fees from Stryker, Centinel Spine, and Spineology; and participation on a data safety monitoring board or advisory board for Premia Spine. Christopher I. Shaffrey reports support from the ISSG Foundation (payment to institution); grants/contracts from the Department of Defense and the NIH (payment to institution); royalties/licenses and consulting fees from Nuvasive, Medtronic, and SI Bone; serving as president of the CSRS, which provided support for travel and hotel for meetings; and stock/stock options from Nuvasive and Proprio.
Editor’s Note This article is a product of the Policy and Advocacy Committee of the International Society for the Advancement of Spine Surgery (ISASS) and is being published as an official communication of the ISASS Board of Directors. It did not undergo the standard review process of the journal but instead was reviewed, revised, and vetted under the authority of the society's Board.
- This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2025 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.
References
- 1.↵Lorio M , Lewandrowski K-U , Coric D , Phillips F , Shaffrey CI . International Society for the Advancement of Spine Surgery statement: restorative neurostimulation for chronic mechanical low back pain resulting from neuromuscular instability. Int J Spine Surg. 2023;17(5):728–750. 10.14444/8525
- 2.↵Centers for Disease Control and Prevention . ICD-10-CM Code for Dysfunction of the Multifidus Muscles, Lumbar Region M62.85. CDC.Gov . October 1, 2024. https://www.cdc.gov/nchs/data/icd/topic-packet-september-2023-final.pdf.
- 3.↵US Food and Drug Administration . P190021 ReActiv8 Implantable Neurostimulation System. FDA Premarket Approval (PMA) Database . June 22, 2020. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?id=P190021.
- 4.↵Gilligan C , Volschenk W , Russo M , et al . An implantable restorative-neurostimulator for refractory mechanical chronic low back pain: a randomized sham-controlled clinical trial. Pain. 2021;162(10):2486–2498. 10.1097/j.pain.0000000000002258
- 5.↵Schwab F , Mekhail N , Patel KV , et al . Restorative neurostimulation therapy compared to optimal medical management: a randomized evaluation (RESTORE) for the treatment of chronic mechanical low back pain due to multifidus dysfunction. Pain Ther. 2025;14(1):401–423. 10.1007/s40122-024-00689-0
- 6.↵Ardeshiri A , Shaffrey C , Stein KP , Sandalcioglu IE . Real-world evidence for restorative neurostimulation in chronic low back pain-a consecutive cohort study. World Neurosurg. 2022;168:e253–e259. 10.1016/j.wneu.2022.09.104
- 7.↵Thomson S , Williams A , Vajramani G , et al . 5-year longitudinal follow-up of patients treated for chronic mechanical low back pain using restorative neurostimulation. Reg Anesth Pain Med. 2025:rapm-2025-106899. 10.1136/rapm-2025-106899
- 8.↵Huang AJ , Yull D , Yau Y-H , et al . A clinical care pathway for patients with chronic mechanical low back pain having restorative neurostimulation for multifidus muscle: description, patient compliance, clinical outcomes, and satisfaction in the first two years. Neuromodulation. 2025;28(4):558–566. 10.1016/j.neurom.2024.12.004
- 9.↵James G , Ahern BJ , Goodwin W , Goss B , Hodges PW . Targeted multifidus muscle activation reduces fibrosis of multifidus muscle following intervertebral disc injury. Eur Spine J. 2024;33(6):2166–2178. 10.1007/s00586-024-08234-5
- 10.↵James G , Ahern B , Goodwin W , Goss B , Hodges P . ISSLS prize in basic science 2025: structural changes of muscle spindles in the multifidus muscle after intervertebral disk injury are resolved by targeted activation of the muscle. Eur Spine J. 2025;34(5):1600–1613. 10.1007/s00586-025-08646-x
- 11.↵Marx RG , Wilson SM , Swiontkowski MF . Updating the assignment of levels of evidence. J Bone Joint Surg Am. 2015;97(1):1–2. 10.2106/JBJS.N.01112
- 12.↵Wright JG . A practical guide to assigning levels of evidence. J Bone Joint Surg Am. 2007;89(5):1128–1130. 10.2106/JBJS.F.01380
- 13.↵Copley S , Batterham A , Shah A , et al . Systematic review and meta-analysis of stimulation of the medial branch of the lumbar dorsal rami for the treatment of chronic low back pain. Neuromodulation. 2024;27(8):1285–1293. 10.1016/j.neurom.2024.08.002
- 14.↵Gilligan C , Volschenk W , Russo M , et al . Five-year longitudinal follow-up of restorative neurostimulation shows durability of effectiveness in patients with refractory chronic low back pain associated with multifidus muscle dysfunction. Neuromodulation. 2024;27(5):930–943. 10.1016/j.neurom.2024.01.006
- 15.↵Ardeshiri A , Amann M , Thomson S , Gilligan CJ . Application of restorative neurostimulation for chronic mechanical low back pain in an older population with 2-year follow up. Reg Anesth Pain Med. 2025;50(3):231–236. 10.1136/rapm-2023-105032
- 16.↵Tieppo Francio V , Westerhaus BD , Carayannopoulos AG , Sayed D . Multifidus dysfunction and restorative neurostimulation: a scoping review. Pain Med. 2023;24(12):1341–1354. 10.1093/pm/pnad098
- 17.↵Thomson S , Williams A , Vajramani G , et al . Restorative neurostimulation for chronic mechanical low back pain - three year results from the United Kingdom post market clinical follow-up registry. Br J Pain. 2023;17(5):447–456. 10.1177/20494637231181498
- 18.↵Shaffrey C , Gilligan C . Effect of restorative neurostimulation on major drivers of chronic low back pain economic impact. Neurosurgery. 2023;92(4):716–724. 10.1227/neu.0000000000002305
- 19.↵Sayed D , Grider J , Strand N , et al . The American Society of Pain and Neuroscience (ASPN) evidence-based clinical guideline of interventional treatments for low back pain. J Pain Res. 2022;15:3729–3832. 10.2147/JPR.S386879
- 20.↵Chakravarthy K , Lee D , Tram J , et al . Restorative neurostimulation: a clinical guide for therapy adoption. J Pain Res. 2022;15:1759–1774. 10.2147/JPR.S364081
- 21.↵Gilligan C , Volschenk W , Russo M , et al . Three-year durability of restorative neurostimulation effectiveness in patients with chronic low back pain and multifidus muscle dysfunction. Neuromodulation. 2023;26(1):98–108. 10.1016/j.neurom.2022.08.457
- 22.↵Mitchell B , Deckers K , De Smedt K , et al . Durability of the therapeutic effect of restorative neurostimulation for refractory chronic low back pain. Neuromodulation. 2021;24(6):1024–1032. 10.1111/ner.13477
- 23.↵Gilligan C , Volschenk W , Russo M , et al . Long-term outcomes of restorative neurostimulation in patients with refractory chronic low back pain secondary to multifidus dysfunction: two-year results of the ReActiv8-B pivotal trial. Neuromodulation. 2023;26(1):87–97. 10.1016/j.neurom.2021.10.011
- 24.↵Thomson S , Chawla R , Love-Jones S , et al . Restorative neurostimulation for chronic mechanical low back pain: results from a prospective multi-centre longitudinal cohort. Pain Ther. 2021;10(2):1451–1465. 10.1007/s40122-021-00307-3
- 25.↵Deckers KJ , De Smedt KL , Mitchell B , et al . Restorative neurostimulation for refractory chronic low back pain: two-year results from the ReActiv8: a clinical trial. Spine J. 2017;17(10):S257. 10.1016/j.spinee.2017.08.182
- 26.↵Hejazi A , Willis C , Ye X , et al . The relationship of PROMIS physical function scores and healthcare resource utilization in patients treated for chronic low back pain. Interv Pain Med. 2024;3(4):100522. 10.1016/j.inpm.2024.100522
- 27.↵Guven AE , Schönnagel L , Chiapparelli E , et al . Relationship between lumbar foraminal stenosis and multifidus muscle atrophy. Spine (Phila Pa 1986). 2025;50(10):702–706. 10.1097/BRS.0000000000005113
- 28.↵You KH , Cho M , Lee JH . Effect of muscularity and fatty infiltration of paraspinal muscles on outcome of lumbar interbody fusion. J Korean Med Sci. 2023;38(20):e151. 10.3346/jkms.2023.38.e151
- 29.↵Zhu F , Jia D , Zhang Y , et al . Moderate to severe multifidus fatty atrophy is the risk factor for recurrence after microdiscectomy of lumbar disc herniation. Neurospine. 2023;20(2):637–650. 10.14245/ns.2346054.027
- 30.↵Burkhard MD , Chiapparelli E , Hambrecht J , et al . Multifidus degeneration: the key imaging predictor of adjacent segment disease. Global Spine J. 2025;15(4):2348–2358. 10.1177/21925682241300085
