A single investigator reviewed fourteen patients who had been treated at a single site between January 2022 and May 2022. Consecutive patients diagnosed with degenerative lumbar disc disease between L1 and the sacrum were not randomized; all underwent an instrumented interbody fusion and received the optimized CBM (VIA Form+, VIVEX Biologic, Inc., Atlanta, Georgia) as a stand-alone bone graft replacement when used with an interbody device. This study received IRB approval (HIRB-2023-13).
Stand-alone bone graft substitute
In this clinical study, the optimized CBM was used without any autogenous grafts including local bone or bone marrow aspirate. The CBM contained three key components that are considered essential bone formation: an osteoconductive matrix from cancellous bone chips (100–300 um), an osteoinductive potential achieved from demineralized cortical bone and an endogenous cellular content with potential for osteogenic differentiation [11–14, 16]. Through aseptic processing, donor bone is separated into two components: viable cell-rich cancellous bone and cortical bone that is demineralized to accentuate growth factors. Cells attached to cancellous bone chips express markers linked with those identified as mesenchymal stem cells and osteoblasts [19]. These cell rich grafts are frozen and protected using a proprietary non-DMSO cryoprotectant [18]. This novel processing results in a 92% viability of cells with expanded cells demonstrating osteogenic potential that was confirmed by in vitro assessment of alkaline phosphatase activity [20].
Inclusion criteria
All patients had clinical complaints of low back pain and radiating leg pain that was unresponsive to a minimum of eight weeks of nonoperative treatment that included immobilization, traction, modalities, medications, and physical therapy. In addition to recurrent or persistent complaints of pain, all patients had an objective neurologic deficit that included one or more of the following: an asymmetric deep tendon reflex, a sensory deficit in a dermatomal pattern, or motor weakness. All patients had a correlative neuroradiographic study. Smoking status and presence of diabetes, osteoporosis, and obesity were recorded for all patients. Patients were not treated surgically if they had a chronic medical condition that required medication, such as steroids or nonsteroidal anti-inflammatory medications that could interfere with fusion.
Patients were included in this study required plain radiographic findings documenting single- or two-level degenerative lumbar disc disease, and they had undergone an additional confirmatory MRI scan. Patients with up to a Grade one spondylolisthesis were also included.
Surgical technique
The CBM was used exclusively as a bone graft replacement. The CBM was placed in the disc space and in the intradiscal implant. Pedicle screws were inserted through a minimally invasive percutaneous technique. Following surgery, all patients are encouraged to ambulate immediately after surgery and physical activities were advanced at the discretion of the attending surgeon. An external lumbar orthosis was used at the preference of the attending surgeon.
Patient Demographics
Patients with single- or two-level degenerative disc disease of the lumbar spine and associated radiculopathy were treated by a posterior lumbar interbody fusion (PLIF) (fourteen levels) or extreme lateral interbody procedure (XLIF) (three levels) using a titanium interbody implant, pedicle screw fixation and the advanced CBM allograft bone graft substitute. Patient age, gender, smoking status, and comorbidities were assessed.
Clinical and Radiographic Follow-up
All patients were examined at three, six, and twelve months; four patients were followed out to eighteen months. All clinical outcomes were assessed by the attending physician; however, clinical outcomes were not assessed through patient derived questionnaires. Neurological physical examination was conducted at each follow up clinical visit. Neurological success was defined as maintenance or improvement in three objective clinical findings: sensory, motor, and reflex testing.
Neutral anteroposterior and lateral radiographs were obtained at each visit. Dynamic flexion-extension lateral radiographs were taken at six, twelve, and eighteen months. Sagittal plane angulation was measured on neutral lateral radiographs and determined by Cobb’s criteria. Intradiscal distraction and subsidence was measured by assessing the vertical distance between the midpoints of the adjacent vertebral endplates. Intradiscal motion and implant migration was assessed on the dynamic radiographs. All radiographs were reviewed by an independent physician. A successful fusion was defined by three criteria. The first was uninterrupted bridging bone across the instrumented disc space through either the interbody implants or around the implants. At the host bone implant interface, there were no radiolucent lines around more than 50% of either implant. In addition, on dynamic flexion extension radiographs there was less than 5° of angular motion and less than 3 mm of translation.
Adverse Events
All patients were monitored for the presence of adverse events during the surgical procedure and during routine or unanticipated office visits. All complications were documented, including additional surgical procedures, spinal injections, and hospital readmissions.