Tender et al. Journal of Medical Case Reports 2011, 5:454 http://www.jmedicalcasereports.com/content/5/1/454 center of the L5 vertebral body (for the two-level case). The trajectory was further adjusted as the guide pin or hand drill or both were advanced through the bone by turning the bevel of the guide pin in the desired direc- tion or controlling the back of the hand drill. Initially, a volumetric discectomy was performed by using specially designed cutting-loop devices and disc extractors. Next, bone graft (a mixture of INFUSE recombinant human bone morphogenetic protein-2 [Medtronic Sofamor Danek], tricalcium phosphate, and autograft harvested during the trajectory creation) was inserted to promote interbody fusion. The threaded axial rod was advanced along the guide pin through S1 and into the L5 vertebral body. The superior aspect of this threaded rod, designed to engage the L5 vertebral body, had a wider thread pitch than the inferior S1 por- tion of the device, allowing intervertebral distraction by a reverse lag-type screw action. Once the axial rod was engaged into L5, the pedicle screw caps were partially loosened, and the axial rod was used to prevent loss of reduction. The rod was further advanced into the L5 vertebral body. By anchoring the rod and releasing the posterior percutaneous pedicle screw caps, distraction of the involved interspace combined with maintenance of reduction was achieved. By design, the axial rod can provide minimal (1 to 2 mm), medium (2 to 4 mm), or maximum (4 to 6 mm) distraction of the spinal inter- space upon insertion. We used either minimal or med- ium distraction axial rods to further indirectly decompress the neural foramina (Figure 3). The proce- dure was extended in a similar fashion to L4 in one patient with L4-5 and L5-S1 disease (Figure 4). Once the axial rod was advanced to its final position, the pedi- cle screw caps were tightened and the three small wounds were closed in layers. The first case was of a 46-year-old Caucasian man who presented with a four-year history of axial low back pain and radiculopathy that was described as 7 out of 10 on average and as 10 out of 10 at its worst on an 11- point Likert scale, of mechanical type (exacerbated by Page 3 of 6 standing or walking for extended periods of time and improved by lying down), and refractory to extensive conservative treatment. During a physical examination, our patient showed no sensory-motor deficits. Lumbar MRI showed a grade 2 spondylolisthesis at L5-S1 with endplate Modic changes and severe bilateral foraminal stenosis. The operative time was 197 minutes, and blood loss was minimal (50 mL). Treatment with the AxiaLIF System reduced the spondylolisthesis to grade 1. Our patient was ambulatory after surgery and reported relief from back pain (maximal pain severity of 10 at pretreatment to 3 at post-treatment), resolution of radicular symptoms (10 to 1), improvements in back function (68% to 15% on the Oswestry Disability Index), and no complications. Our patient was discharged from the hospital two days after the procedure. To confirm the adequate placement of the instrumentation and to accurately evaluate the final constructs, a computed tomography scan was obtained after the operation (Fig- ure 5). Wide indirect neuroforaminal decompression and solid fixation constructs were achieved. Successful fusion, defined as no motion at the treated segment on flexion/extension radiographs and evidence of bone growth between the adjacent vertebral bodies on recon- structed computed tomography images, was demon- strated at one-year follow-up (Figure 6). The second case was a 51-year-old Caucasian female who presented with a 10-year history of axial low back pain and a one-year history of radiculopathy. The pain was described as 9 out of 10 on average and 10 out of 10 at its worst, of mechanical type, and refractory to conservative treatment. During a physical examination, our patient showed no sensory-motor deficits. Lumbar MRI showed a grade 2 spondylolisthesis at L5-S1 with severe bilateral foraminal stenosis. The operative time was 173 minutes, and blood loss was minimal (50 mL). Treatment with the AxiaLIF System reduced the spon- dylolisthesis to grade 0. Our patient was ambulatory after surgery and reported relief from back pain (10 to 2), resolution of radicular symptoms (10 to 1), Figure 3 Intraoperative lateral fluoroscopic images of L5-S1 spondylolisthesis reduction and distraction (case 1). The grade 2 spondylolisthesis (left) is reduced to grade 1 by using the percutaneous pedicle screws (middle), and the L5-S1 interspace is further distracted by using the anterior axial rod.