Fig. 1.

This 63-year-old female with history of instrumented fusion at L5/S1 some 30 years prior was referred to our spine center with immobilizing low back pain and bilateral, radicular lower extremity pain (VAS back 7/10, VAS leg 7/10, Oswestry Disability Index (ODI) 26.7/100%, Core Outcome Measures Index (COMI) Back score 6.9/10) owing to adjacent segment disease with spinal stenosis and failed extended conservative treatment. There are anatomical peculiarities with a singular pelvic kidney ventral to the lumbar spine and tortuous arterial vessels between the psoas muscle and the discal compartment at the L4/5 level, rendering both an anterior and lateral approach to the L4/5 segment unsafe. (A) Preoperative standing x-ray, showing the misplaced L5 screws violating the L4/5 disc space with degenerative spondylolisthesis. Her pelvic incidence is 69° (Roussouly type-4 geometry), requiring a total lumbar lordosis (LL) of 65° and LL of 39°–42° between L4 and S1. Her actual lordosis between L4 and S1 was 21.7° (illustrated in red). (B) After screw placement and bilateral facetectomy the spondylolisthesis reduction is performed, but the segment cannot be opened widely at this time. C: The 4mm chisel is taken to perforate the ALL in a safe region without proximity to blood vessels (Video 1). (D) Then, the ALL is resected from both sides with the 2 mm Kerrison punch until retroperitoneal fat is visualized (Video 2). (E) Now, the segment gets very mobile and can be opened as wide as desired with the Chiari interbody spreader. (F) After graft insertion and placement of the cage, posterior compression is applied until the desired degree of segmental lordosis is restored. In this patient, the 3-month postoperative x-ray shows restoration of 43.3° of LL between L4 and S1 (illustrated in red). The patient experienced no complications and was recovering well (VAS back 0/10; VAS leg 0/10; ODI 13.3/100%; COMI Back score 3.0/10).