Biologic Injection For Adults With Lumbar Disc Herniation

The goal of this clinical trial is to find out whether adding a bone-marrow aspirate concentrate (BMAC) injection during surgery can improve recovery in adults undergoing lumbar microdiscectomy for a lumbar disc herniation. The main questions it aims to answer are: * Does the BMAC injection lead to better disc tissue health after surgery (as seen on MRI scans)? * Does the BMAC injection lead to greater improvement in pain and disability compared to surgery alone? Participants will be adults aged 18 and older who are scheduled for lumbar microdiscectomy surgery. Researchers will compare one group of participants receiving the standard-of-care surgery plus the BMAC injection with another group receiving the same surgery without the injection to see if the injection offers added benefit. Participants will: * Have surgery (microdiscectomy) with or without the injection. * Complete pain and disability questionnaires at several times over 2 years. * Undergo MRI scans at baseline and follow-up to assess disc structure and tissue health. * Provide samples of leftover disc or bone-marrow tissue (as applicable) from surgery for analysis.