Introduction: Interspinous process fixation (ISPF) has been proposed as a structurally viable alternative to posterior screw fixation when supplementing anterior lumbar interbody fusion (ALIF). Given its ability to provide robust sagittal stability through a minimally disruptive midline approach, ISPF complements the inherent axial and coronal stability of a stand-alone ALIF construct while diminishing posterior disruption. However, it is not well understood whether ISPF is suitable at L5/S1 given limited spinous process bone mass at the sacrum and increased shear forces. The objective of this analysis was to compare outcomes of subjects receiving ALIF with either ISPF or pedicle screw fixation (PSF) at L5/S1.
Methods: Data was collected as part of a prospective, randomized, controlled, multi-center study. All analysis subjects received single-level (L5/S1) ALIF with supplemental ISPF (n=20) (Fig. 1) or PSF (n=12) for degenerative disc disease and/or spondylolisthesis (Grade = 2). Posterior fixation selection was randomized. PSF technique was performed per investigator institutional standard-of-care. Anterior plating was permitted. Perioperative outcomes, patient reported outcomes, and radiographic outcomes were collected at 1.5, 3, 6, 12, and 24mos post-op.
Results: Demographics are summarized in Figure 2. No posterior hardware related complications were observed in either cohort perioperatively or during the follow-up period. No secondary revision surgeries were performed in either cohort. ISPF subjects experienced notably less operative time (44.5 vs. 88.0min), blood loss (56 vs. 161cc), incision length(s) (5.6 vs. 7.6cm), and fluoroscopy time (10.7 vs. 35.3sec) than PSF subjects during the posterior procedure. Patient report outcomes scores and interbody fusion outcomes are captured in Figures 3 to 5.
Conclusions: ISPF provides an efficient and minimally disruptive alternative to PSF with ALIF while supporting clinically advantageous outcomes out to 2-year follow-up. Despite proposed structural limitations at L5/S1, adjunctive ISPF with ALIF in single-level degenerative cases can be an effective solution.
Patient Care: Given the minimally disruptive nature of ISPF with ALIF, it has the potential to diminish intraoperative complication while still providing clinically robust stability and supporting quality long-term fusion and pain outcomes.
Learning Objectives: By the conclusion of this session, participants should be able to discuss/identify…
1) How does the novel ALIF+ISPF technique compare to traditional ALIF+PSF?
2) Patient demographics/pathologies for which the ALIF+ISPF technique may be advantageous
3) Potential limitations associated with the ALIF+ISPF technique