General Session: Spinal Innovation
Presented by: C. Hill - View Audio/Video Presentation (Members Only)
C. Hill(1), K.B. Strenge(1), R. DenHaese(2), C. Ferry(3), B. Ventimiglia(3), T. Glorioso(4), K. Martin(3), S. Martineck(5)
(1) Orthopaedic Institute, Paducah, KY, United States
(2) AXIS Neurosurgery and Spine, Williamsville, NY, United States
(3) Zimmer Biomet Spine, Broomfield, CO, United States
(4) University of Colorado - Denver, Denver, CO, United States
(5) Clinical Trials Consultant, Buffalo, NY, United States
Introduction: A high iliac crest is often a contraindication for lateral lumbar interbody fusion (LLIF) at L4/5 due to an obstructed direct lateral trajectory. While mild obstruction can typically be overcome with a modified trajectory and patient/bed positioning, obstruction up to/exceeding the inferior L4 endplate can render the technique geometrically infeasible. However, it has been proposed that use of angled instrumentation and a retractor possessing an intradiscal shim and cephalad/caudal blade manipulation capabilities may help overcome such anatomical limitations. The objective of this analysis was to assess a lateral access system (Timberline Lateral Fusion System, Zimmer Biomet Spine; Figure 1), possessing the aforementioned features and capabilities, in accommodating high-crested L4/5 subjects. Intraoperative metrics and complication profiles, as well as follow-up outcomes, were compared between high-crested and non-obstructed subjects.
Methods: Data was retrospectively collected from a prospective study. All analysis subjects underwent LLIF with posterior instrumentation (pedicle screw or interspinous process fixation) at L4/5 for the treatment of spondylolisthesis (≤ Grade 2) and/or degenerative disc disease. 19 high-crested and 26 unobstructed subjects were assessed. The iliac crest (operative side only) was considered 'high' if obstructing up to/exceeding the inferior L4 endplate. Iliac crest height was determined via pre-operative A/P and lateral radiographs. Intraoperative outcomes (interbody approach only), complication profiles, and patient reported follow-up outcomes (1.5, 3, 6, 12, and 24mos) were reported.
Results: Intraoperative metrics were comparable between cohorts. Outcomes were as follows (high-crested vs. unobstructed): OR Time: 53.4 vs. 45.6min; Fluoroscopy Time: 63.5 vs. 71.8sec; Blood Loss: 34.9 vs 33ml; Incision Lengths: 4.6 vs. 4.6cm. No intraoperative complications explicit to the interbody procedure were reported in either group. One high-crested subject required a secondary surgical intervention due to a vertebral fracture at an adjacent level. Both groups demonstrated significant decreases in ODI scores from baseline out to 24mos. Mean ODI score improvement at 24mos was 23.3 and 24.0pts for high-crested and unobstructed subjects, respectively. ZCQ and SF-36 outcome trends were consistent with those observed with ODI outcomes.
Conclusions: The lateral access system assessed in this study demonstrated an ability to accommodate high-crested L4/5 subjects and supported outcomes similar to those of unobstructed subjects. These findings support the ideal that a high iliac crest at L4/5 is not an immediate contraindication for LLIF. Use of proper angled instrumentation and a retractor capable of intradiscal anchoring can help mitigate anatomical/geometrical limitations when a direct lateral trajectory isn't available.
Fig 1. Angled Cage Insertion Instrumentation
Fig 2. ODI Improvement vs. Time