The authors present a new minimally invasive posterior thoracic and upper lumbar spinal approach, using midline-staged incision with bilateral dissection via the natural muscular cleavage plane between the spinalis and longissimus muscles for pedicle fixation. The aim was to clarify anatomy and compare results between this technique and the conventional paraspinal approach. An anatomic MRI study determined the position of the superficial aponeurosis of the spinalis-longissimus intermuscular cleavage plane with respect to the midline. The surgical procedure is described. A radiological and clinical study evaluated 24 patients divided into two comparative groups, operated on via the medial intermuscular or the paraspinal approach, for isolated A3 and B2 Magerl fracture between T2 and L2, without neurologic involvement. Pain, postoperative complications, reduction quality and esthetic satisfaction were assessed. MRI located the cleavage plane, which was consistently 11.01±0.9mm (range, 9.4−12.3mm) from the midline. In the “medial approach” group, hospital stay was significantly shorter, by 3 days, at 4±1.9 (range, 2−8 days) (p: 0.005); pain on VAS was 2 points lower at postoperative day 1 (2.1±1.4; range,≤1−4; p:0.032), and lower at discharge (0.3±0.6; range, 0−1; p: 0.001). The scar was considered esthetically very satisfactory. This easily performed and reproducible medial intermuscular approach showed low iatrogenesis, significantly improving postoperative course.