Please assess the completion status of the following clinical trial:

Trial Title: Aspen Spinous Process Fixation System for Use in PLF in Patients With Spondylolisthesis

Study Design Characteristics:
- Allocation: None
- Intervention Model: None
- Observational Model: COHORT
- Primary Purpose: None
- Time Perspective: PROSPECTIVE
- Masking: None
- Phase: None
- Number of Arms: None

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).

- Gender: ALL
- Minimum Age: 50 Years
- Maximum Age: 80 Years
- Healthy Volunteers: f

Study Arms:
- Aspen Spinous Process Fixation Device (Type: None): The Aspen device provides supplemental posterior fixation for fusion

Based on this trial design, predict the completion outcome and termination type (if applicable).