A Post-marketing Study to Evaluate a Novel Surgical Monitoring Technique Using the EARP Nerve Cuff in TLIF Surgery.

Evaluation Of A Novel Technique To Monitor Neurophysiological Activity During TLIF Surgery Using The Endoscopic Assisted Retropsoas (EARP) Nerve Cuff Electrode and Retractor With A Commercially Available Lumbar Spine Retractor System

The purpose of this study is to evaluate the differences (the effectiveness and the safety) between two different nerve and muscle monitoring devices currently available during a TLIF surgery.

The Endoscopic Assisted Retropsoas (EARP) Nerve Cuff Electrode and Retractor surgical and nerve monitoring tools will be used in addition to standard nerve monitoring tools during the surgery. The choice of standard nerve monitoring equipment is based on the decision of the surgeon and technologist and is not dictated by this study.

These tools will be compared with regards to safety and ability to accurately monitor the nervous system during the surgery.

Study Overview

• Status: Completed
• Conditions: Transforaminal Lumbar Interbody Fusion Surgery
• Intervention / Treatment: Device: Nerve Cuff and Retractor System

Detailed Description

The application of traditional SSEPs and tcMEPs to lumbar nerve root monitoring during TLIF surgery is both challenging and problematic. When applied to lumbar nerve root monitoring, SSEPs and tcMEPs unfortunately suffer in specificity, sensitivity, or both. A surgeon thus cannot confidently rely on these techniques to monitor nerve root function and must guess the likelihood of dysfunction.

Spontaneous EMG (sEMG) is also used to monitor nerve root activity. While sEMG is an excellent indicator of spinal nerve root manipulation, it is a poor diagnostic indicator of dysfunction. 90-95% of sEMG alerts are not associated with dysfunction yielding a high false positive rate and poor specificity, and postoperative deficits are often not associated with sEMG alerts yielding many false negatives and poor sensitivity. The primary utility of sEMG is to use as an indicator of manipulation, which prompts the acquisition of tcMEPs to assess function.

There is a clear need to take the guesswork out of monitoring the functional status of nerve roots at risk during lumbar decompressions and select interbody fusions. During TLIFs, the exiting nerve root is at risk as it courses obliquely across disc space encroaching on the surgical corridor. Standardly, a hand-held retractor is used to retract and protect the nerve root during disc space preparation, implant insertion or even simple decompression. This maneuver and retraction place a particular nerve root at risk, but again, traditional SSEP and tcMEPs are not ideal for monitoring that risk.

The EARP Nerve Cuff Electrode (Retropsoas Technologies) is a novel, Class II, device that is 510(k) cleared by FDA. It conducts electrical signals as a component of intraoperative neuromonitoring, is used with commercially available neuromonitoring systems, and does not stimulate or record the signal itself. The standard connectors at the proximal end interface with the neuromonitoring equipment. The distal nerve cuff electrode partially encircles and contacts the target nerve root. It uses a bipolar configuration to limit current spread. It is available in several inner diameters to accommodate variability in patient nerve root size anatomy.

The EARP Retractor is a Class I device used with a commercially available Retractor system and is only used as an additional 4th blade.

In TLIF surgery, the exiting nerve must be retracted to allow for sufficient access to the intervertebral disc space. The retraction is applied at the medial portion of the nerve root. The application of this retraction may produce activity in the nerve root and/or conduction changes in the nerve root due to temporary manipulation, compression, or ischemia related to the retraction.1

The objective of the study is to demonstrate the ability to safely monitor lumbar nerve root activity and function during retraction using an Endoscopic Assisted Retropsoas (EARP) Nerve Cuff Electrode and an EARP Retractor system during a standard Transforaminal Lumbar Interbody Fusion (TLIF), with improved specificity and sensitivity over traditional monitoring techniques.

• Study Type: Interventional
• Enrollment (Actual): 5
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19107
      • Rothman Orthopaedic Institute
    • Pittsburgh, Pennsylvania, United States, 15212
      • Allegheny-Singer Research Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Undergoing TLIF between L2-S1

Exclusion Criteria:

• Requiring TLIF surgery only at the L5-S1 level
• Acute lumbar spine trauma requiring immediate intervention
• Allergy or contraindication to propofol
• Lower extremity amputation
• Significant lower extremity edema noted on clinical exam
• Current treatment with chemotherapy, radiation, or immunosuppression
• Pregnant, or plans on becoming pregnant in the near future
• History of allergy to titanium, platinum, aluminum, stainless steel, or silicon

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Undergoing a single-level or two-level TLIF between L2-S1; During the surgery, the standard monitoring devices and the EARP monitoring study devices and techniques will be used.	Device: Nerve Cuff and Retractor System; Endoscopic Assisted Retropsoas (EARP) Nerve Cuff Electrode and an EARP Retractor system to safely monitor lumbar nerve root activity and function during a standard Transforaminal Lumbar Interbody Fusion (TLIF).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of patients that experience an Adverse Device Effect (ADE)	Adverse device effect (ADE) - Adverse event (AE) judged by the clinician related to the use of an investigational devices. This includes any AE resulting from insufficient or inadequate instructions for use or the deployment, implantation, installation, or operation, or any malfunctioning of the investigational devices and any event resulting from use error or from unintentional misuse of the investigational devices.	From enrollment through the end of the follow-up assessment at week 6
Ability of EARP System to alert the surgeon to nerve irritation during surgery compared to standard IONM monitoring techniques	Signal amplitude at baseline, during initial retraction, and maintenance of retraction will be analyzed for changes using a 50% decrease as a surgeon alert. IONM assessments using traditional electrodes: SSEPs, tcMEPs and tfMEP. IONM assessments using EARP cuff: cuff SSEPs, cuff tcMEPs, and cuff tfMEPs.	During the TLIF surgery.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the specificity and sensitivity of alerts to neurological deficits.	Evaluate the sensitivity and specificity of alerts to neurological deficits (by modality and overall). This will include neurological deficits noted on exams as well as a surrogate measure of deficit defined as an alert which resolves with relaxation of retraction.	From time of surgery through the end of the follow-up assessment at week 6
Assess monitorability of muscles/nerves	Compare the number of evaluable muscles during the surgery by modality and overall.	During the TLIF surgery.
Assess the change from baseline to end of surgery for each muscle and modality	Assess the lower extremity motor deficits post-surgery based on the ipsilateral lower extremity motor exam performed at Baseline, Post-Surgery, and at the 6-week follow-up visit.	From enrollment through the end of the follow-up assessment at week 6

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the set-up time required for standard IONM monitoring	Time for needle placement, tcMEP Baseline acquisition, tfMEP Baseline acquisition, and needle removal will be calculated and compared to set-up of EARP Nerve Cuff	During the TLIF surgery
Analyze sEMG activity and any correlations to MEP data and patient-specific characteristics	Analyze sEMG activity and any correlations to MEP data and patient-specific characteristics	From enrollment through the end of the follow-up assessment at week 6
Characterize retraction, relaxation and release data	Characterize retraction, relaxation and release data for the EARP Device	During the TLIF surgery
Evaluate total emergence time for anesthetic regimen	Evaluate total emergence time for anesthetic regimen	During the TLIF surgery

Collaborators and Investigators

• Sponsor: Retropsoas Technologies, LLC
• Investigators: Study Director: Nicholas Poulos, MD, Retropsoas Technologies, LLC

Study record dates

Study Major Dates

• Study Start (Actual): June 7, 2024
• Primary Completion (Actual): December 1, 2025
• Study Completion (Actual): December 1, 2025

Study Registration Dates

• First Submitted: January 3, 2024
• First Submitted That Met QC Criteria: January 3, 2024
• First Posted (Actual): January 12, 2024

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: TLIF Surgery
• Other Study ID Numbers: EARP-1-1001

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data that underlie the results reported in publications, after deidentification (text, tables, figures, and appendices).
• IPD Sharing Time Frame: Beginning 9 months and ending 36 months following article publication.

IPD Sharing Access Criteria

Investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose.

For individual participant data meta-analysis.

Information can be accessed by contacting the Sponsor directly (contact info TBD)

• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes