General Session: Thoraco-Lumbar Degenerative

Presented by: C. Hill - View Audio/Video Presentation (Members Only)

Author(s):

K. Kim(1), R. Denhaese(2), C. Hill(3), K.B. Strenge(3), A. de Moura(4), P. Passias(4), R. Panchal(1), P. Arnold(5), C. Ferry(6), B. Ventimiglia(6), T. Glorioso(7), K. Martin(6), S. Martineck(8)

(1) UC Davis, Sacramento, CA, United States
(2) AXIS Neurosurgery and Spine, Williamsville, NY, United States
(3) Orthopaedic Institute, Paducah, KY, United States
(4) New York Spine Institute, New York, NY, United States
(5) University of Kansas, Kansas City, KS, United States
(6) Zimmer Biomet Spine, Broomfield, CO, United States
(7) University of Colorado - Denver, Denver, CO, United States
(8) Clinical Trials Consultant, Buffalo, NY, United States

Abstract

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 iatrogenic 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.

Materials and 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) 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: Mean age, sex, and BMI were comparable between cohorts. Anterior plating/fixation was used in 65% of ISPF cases and 66.7% of PSF cases. 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. Mean ODI improvement at 24mos was 18.7 and 15.4 for ISPF and PSF subjects, respectively (Fig.2). Mean SF-36 Mental/Physical score improvement at 24mos was 3.6/6.3 and -2.1/9.2 for ISPF and PSF subjects, respectively. Mean ZCQ Physical/Symptom score improvement at 24mos was 0.25/0.99 and 0.51/0.71 for ISPF and PSF subjects, respectively. Interbody fusion (score of BSF-3) was reported in 100% of ISPF and PSF subjects at 24mos.

Conclusions: Posterior fixation in ALIF, particularly at L5/S1, continues to fall out of favor given good outcomes reported with stand-alone application and the invasive nature of internal fixation. However, as this study shows, ISPF provides a significantly less invasive alternative to PSF 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 when addition posterior rigidity and sagittal correction is desired.

Fig 1. ALIF with ISPF at L5/S1 (24mos)

Fig 2. ODI Improvement from Baseline vs. Time