Background: The conventional approach for lumbar fixation involves subperiosteal muscle dissection, and disruption of normal blood and nerve supply of the back muscles. Different transmuscular approaches, have been described for better preservation of normal neurovascular structures. This leads to less muscle damage and at- rophy and consequently less postoperative pain. Purpose: Compare between transmuscular approach and conventional approach for lumbar spine fixation. Study Design: A prospective comparative study carried at Neurosurgery Department, Zagazig University, during the period from February 2018 to February 2019. Patients and methods: 60 patients with degenerative lumbar instability were included in this study and randomly assigned to one of the two groups, Group A (transmuscular group) and Group B (conventional group). Outcome was assessed, using postoperative Visual Analogue Score (VAS) for back pain, change in pre and postoperative levels of Creatine Phospho-Kinase (CPK), and the postoperative change in the cross-sectional area of multifidus muscle, measured using axial CT cuts. Results: As regards the hospital stay, it was 1.5 days less in Group A than Group B (P<0.001). The serum CPK increased by only 3 folds in Group A in comparison to 15 folds increase in Group B, indicating less muscle damage (P<0.001). Postoperative Visual Analogue Scale (VAS) for back pain was higher in Group B than Group A (P<0.001). Decrease in cross-sectional muscle area in Group B (40%) was more than the decrease in cross- sectional area in Group A (10%), (P<0.001), which means more muscle atrophy in Group B than in Group A. Conclusion: Using the transmuscular approach for lumbar spine fixation is a more conservative approach, than the conventional approach, with less muscle atrophy, better preservation of anatomy, and less postoperative pain.