Introduction: Interspinous process fixation (ISPF) has received increased consideration as a minimally disruptive adjunct to circumferential spinal arthrodesis; however, it is still unclear whether ISPF can support long-term healing outcomes similar to those supported by pedicle screw fixation (PSF). The objective of this study was to prospectively compare the outcomes of subjects receiving anterior (ALIF) or lateral (LLIF) interbody fusion with adjunctive ISPF or PSF.
Methods: All subjects received single-level interbody fusion (ALIF or LLIF) with supplemental ISPF (n=66) or PSF (n=37) for the treatment of degenerative disc disease and/or spondylolisthesis. The randomization ratio was 2:1, ISPF to PSF subjects. The PSF approach (MIS/open; uni/bilateral) and interbody approach (ALIF or LLIF) were per investigator institutional standard-of-care. Perioperative outcomes, patient reported outcomes, and fusion outcomes were collected through 24mo. Outcomes through 12mo. are reported here. Note: 2-year outcomes to be available at time of presentation. Analysis was performed using a linear mixed model (p<0.05).
Results: No statistically significant differences were observed between cohorts with respect to change in patient reported outcome scores (ODI, SF-36, ZCQ, and NRS/VAS) from baseline to 1.5, 3, 6, or 12months. ISPF subjects did demonstrate a greater mean ODI decrease across all follow-up time points.
BSF interbody fusion scores demonstrated comparable (p=0.33) outcomes between cohorts. 92% of ISPF subjects exhibited bone formation between the ISPF device plates bridging the spinous processes.
Two ISPF subjects and four PSF subjects required a secondary surgical intervention in which the investigator indicated possible relation to posterior fixation.
Conclusions: ISPF subjects demonstrated clinically advantageous trends across all follow-up metrics, achieving significant reduction in all patient reported outcomes and exhibiting quality bone formation in both the anterior and posterior aspects.
Patient Care: Should the long-term outcomes achieved with ISPF compare similarly to those with PSF, it would indicate ISPF as a potentially more efficacious solution in posterior fixation. Given its minimally disruptive nature and ease of placement, patients would have the potential to experience less iatrogenic complication while achieving comparable or favorable long-term outcomes.
Learning Objectives: By the conclusion of this session, participants should be able to discuss/identify…
1) Outcome trends achieved with adjunctive ISPF in circumferential fusion
2) Patient demographics/pathologies for which ISPF may be advantageous
3) Similarities and differences between outcomes achieved with adjunctive ISPF or PSF