Inclusion Criteria:  Patients scheduled for epidural nerve block for lower back pain Patients over 21 years of age Back pain lasting more than 6 months Patients with ineffective or insignificant effects of conventional drugs and nerve block for back pain Patients with spinal stenosis or disc herniation at the lumbar 4-5 or lumbar 5-sacral 1 level on MRI, and the cross-sectional area of the multifidus muscle at the lesion site is less than 5 cm2 when measured by ultrasound.  Exclusion Criteria:  When the degree of low back pain is 3 points or less on the 11-scale numeric rating scale (hereafter NRS) If lower back pain has rapidly worsened within the last week If you have other diseases that may cause low back pain: osteoarthritis of the hip joint, cancer, inflammatory arthritis, spondylitis, fibromyalgia, complex regional pain syndrome, herpes zoster, postherpetic neuralgia, etc. When a diagnostic epidural nerve block is planned In the case of receiving conservative treatment, procedure, or surgery other than oral drugs such as epidural nerve block or proliferation treatment for the treatment of lower back pain within 4 weeks of screening When the low back pain assessed by NRS decreased by more than 50% after epidural nerve block in screening If back surgery is planned within 3 months of the procedure When NRS and ODI measurements cannot be made When collagen injection is contraindicated (eg when allergic to swine) Pregnant women If you cannot read or agree to the consent form If you are unable to sign the consent form yourself