The Aspen MIS Fusion System versus Pedicle Screw Fixation, A Comparison of Supplemental Posterior Fixation in ALIF and LLIF: Intraoperative Outcomes in a Prospective Randomized Multi-Center Trial

Presented at SMISS Annual Forum 2014
By Kee Kim MD
With

Disclosures: Kee Kim MD A; Lanx Inc., B; Zimmer Biomet Spine.

Introduction:
Spinal arthrodesis with supplemental non-segmental posterior fixation is a viable surgical treatment for patients presenting with pain secondary to neural compression, abnormal motion, and/or instability. The Aspen^® MIS Fusion System (Biomet Spine, LLC (by its subsidiary Lanx, Inc.)) offers an interspinous process fixation (ISPF) option aimed to address iatrogenic risks and the limitations associated with other forms of posterior fixation, particularly pedicle screw fixation (PSF), considered the current gold standard. Aspen^® System (AS) requires minimal soft tissue disruption and limited bony intrusion to achieve rigid fixation. However, no study has prospectively compared the AS, or any ISPF system, to PSF.

Aims/Objectives:
To compare the intraoperative outcomes of subjects undergoing single-level anterior (ALIF) or lateral (LLIF) lumbar interbody fusion supplemented with either the AS or PSF.

Methods:
Multi-center, prospective, randomized clinical study involving 103 patients were conducted. The enrollment randomization ratio was 2:1, AS to PSF subjects. Sixty five patients received the AS and 38 patients received PSF. PSF approach was performed according to surgeon preference. Intraoperative estimated blood loss (EBL), surgical time, patient length-of-stay (LOS), fluoroscopy time, and incision length(s) was recorded and stratified by treatment type for simple comparison using a linear mixed model, which included a random intercept accounting for within-site correction.

Results:
Average age of the AS and PSF subjects was 50.4 and 53.0 respectively. The male to female ratio for AS and PSF subjects was 35:30 and 11:27 respectively, AS subjects experienced significantly less EBL, surgical time, fluoroscopy exposure, and incision length than PSF subjects. with respect to the posterior approach. Intraoperative outcomes pertinent to the interbody approach alone did not significantly differ between treatment groups. LOS also did not significantly differ between treatment groups. Only fluoroscopy time significantly differed between treatments (AS < PSF) for the cumulative surgical procedure. 36.2% of AS subjects and 47.4% of PSF subjects experienced at least one adverse intraoperative event; ten of these were device-related (AS, n=4; PSF, n=6). Serious device-related adverse events per surgery occured at a rate of 0.03 (n=2) with the AS versus 0.05 with PSF (n=2).

Conclusions:
Aspen^® MIS Fusion System is less invasive intraoperatively with a lower incidence of adverse events than PSF when supplementing ALIF or LLIF.