aspen spinous process fixation system for use in plf in patients with spondylolisthesis

Conditions: Spondylolisthesis

Summary: the purpose of this clinical investigation is to evaluate the clinical outcomes of subject with spondylolisthesis undergoing posterolateral fusion (plf) surgery utilizing the aspen™ spinous process fixation system. the aspen™ device will be evaluated using oswestry disability index (odi) improvement and success of fusion.

evaluate the clinical outcomes of subject with spondylolisthesis undergoing posterolateral fusion (plf) surgery utilizing the aspen™ spinous process fixation system. the aspen™ device will be evaluated using oswestry disability index (odi) improvement and success of fusion.

Eligibility criteria:
inclusion criteria: * age between 50 and older * diagnosis of mild segmental instability on standing radiography lateral film defined as degenerative spondylolisthesis ≤ 4mm in dynamic imaging (i.e., flexion/extension) * scheduled for an elective single-level posterior decompression and posterolateral fusion using aspentm spinous process fixation system * oswestry disability index (odi) v 2.1 score \>30% * failed at least 3 months of conservative care (non-surgical) or has clinical signs of neurological deterioration * signed informed consent form exclusion criteria: pre-operative * marked degenerative spondylolisthesis (\>4mm) * lesions requiring surgery involving two levels * prior surgery at index level or adjacent level * prior spinal fusion surgery * isthmic or lytic spondylolisthesis * incompetent or missing posterior arch at the affected level (e.g. complete laminectomy, pars defect) * requires complete laminectomy at level of surgery * facet joints at implant level are absent or fractured * vertebral body compromise or acute fracture at implant level * body mass index (bmi) ≥ 35 * known allergy to titanium * osteoporosis: score (simple calculated osteoporosis risk estimation) will be used to screen subjects requiring dexa. subjects with t-score \< -2.5 will be excluded * paget's disease, osteomalacia, or any other metabolic bone disease * use of medications or any drug known to potentially interfere with bone/soft tissue healing (e.g. chronic systemic steroids) * planned use of additional segmental fixation (eg. facet screws, anterior/lateral plating, anchored cages) * use of bone morphogenetic protein (bmp)\* * unlikely to comply with the follow-up evaluation schedule * in the opinion of the investigator, subject has history of chemical substance dependency or significant psychosocial disturbance that may impact the outcome or study participation * active participation in a clinical trial of another drug or device * active systemic infection or any other health condition that would preclude surgery * history of invasive malignancy, except if the subject has received treatment and displayed no clinical signs and symptoms for at least five years * pregnant or planning to become pregnant during study participation * involvement in active litigation related to back problems at the time of screening * direct involvement in the execution of this protocol * pre-existing conditions that could interfere with the evaluation of outcome measures (e.g. musculoskeletal, neuromuscular, etc.) intra-operative exclusion * intra-operative visualization of a \> 4mm spondylolisthesis not previously noted radiographically * any change in the surgical procedure that violates the inclusion/exclusion criteria. (eg. switching to double level procedure; placing pedicle screws as posterior fixation).