This is a prospective, non-randomized multi-center study to evaluate intraoperative neuromonitoring results in subjects who undergo eXtreme Lateral Interbody Fusion (XLIF) surgery at any number of levels inclusive of L4-5.

Subjects will present with degenerative conditions in the lumbar spine that are amenable to surgical treatment and will be screened prior to study enrollment. Subjects will undergo neuromonitoring during the XLIF operation, as per standard care. They will then be re-evaluated immediately after surgery and at the first standard postoperative follow-up visit (6 weeks) to assess for presence of new neural deficit. If a new neural deficit is identified, the patient will be followed per the Investigator's standard follow-up schedule until symptoms have resolved (or are deemed permanent).

A total of 300 subjects will be enrolled in this study from multiple centers. The subjects will have degenerative conditions of the lumbar spine with planned treatment including XLIF surgery. The following eligibility criteria are designed to identify existing clinic patients for whom study under this protocol is considered appropriate. All subjects must meet the inclusion/exclusion criteria below in order to be considered for enrollment.

Inclusion Criteria:

• Persistent back and/or leg pain unresponsive to conservative treatment for at least six (6) months, unless surgical treatment is clinically indicated earlier
• Indicated for extreme lateral interbody fusion at any number of levels inclusive of L4-5
• At least 18 years of age at the date of written informed consent
• Able to undergo surgery based on physical exam, medical history and surgeon judgment
• Willing and able to return for post-treatment exams according to the follow-up called for in the protocol
• Signed and dated informed consent form

Exclusion Criteria:

• Patient has a mental or physical condition that would limit the ability to comply with study requirements
• Patient is a prisoner
• Patient is involved in active litigation relating to the spine (worker's compensation claim is allowed if it is not contested)
• Patient has an underlying neurological disease or neurological deficit that is not associated with the condition for which he/she is seeking surgical intervention (e.g., diabetic peripheral neuropathy)
• Patient is participating in another clinical study that would confound study data

Study population will consist of patients from participating site locations.