Introduction: Minimally invasive expandable spacers such as CALIBER-L® (C-L) (Globus Medical, Audubon, PA), have the advantage of minimal insertion height as well as in-situ expansion. This may reduce the force on the vertebral endplate, otherwise caused by repeated impaction while inserting a traditional spacer.
Methods: Ten human lumbar ligamentous cadaveric spines, divided into two groups of five specimens each, were tested on 6DOF spine simulator in flexion-extension (FE), lateral bending (LB), and axial rotation (AR), using a load control protocol of ±6.5Nm. PLYMOUTH®(Globus Medical) and XLP®(Nuvasive, San Diego, CA) were the lateral plates(LP) used in group 1, and 2, respectively. A 360° fusion was simulated using BPS, unilateral pedicle screws (UPSips), spinous process fixation device (SPF) with C-L and LP. All the specimens were sequentially tested in 1) Intact; 2) C-L+BPS; 3) C-L+LP; 4) C-L+LP+UPSips; 5) C-L+LP+BPS; 6) C-L+LP+SPF.
Results: The C-L+PLY construct reduced ROM to 27%, 16.1%, and 50.1%, and the C-L+XLP construct reduced ROM to 23.3%, 22.3%, and 33.2% in FE, LB, and AR, respectively, compared to intact. In FE, ROM of the C-L+BPS construct was significantly higher than the C-L+PLY construct by 20.2%, and the C-L+XLP construct by 16.4%.(Figure 1).
Conclusions: The current biomechanical study showed that adding PLYMOUTH™ to CALIBER-L® significantly reduced range of motion. The addition of bilateral pedicle screws to CALIBER-L® demonstrated higher stability in flexion-extension, than adding a lateral plate. However, simulated 360° fixation with unilateral pedicle screws, CALIBER-L®, and PLYMOUTH™ showed similar biomechanical stability, to the construct built with bilateral pedicle screws. Similarly, the addition of spinous process fixation also showed significant stability similar to pedicular fixation. There was statistically no significant difference between the biomechanical stability of PLYMOUTH™ and XLP lateral plates, when added to CALIBER-L®.
Patient Care: CALIBER-L®, an expandable LLIF spacer may be highly advantageous in treating patients with collapsed disc, due to its minimal insertion height and in-situ expansion capability.Additionally,a lateral plate may strengthen the stability of the test construct.
Learning Objectives: The objective of the current study was two-fold :1) to compare the biomechanics of adding a lateral plate (LP) versus bilateral pedicle screws (BPS) to C-L; 2) to compare the biomechanical stability of the PLYMOUTH™ (Globus Medical) lateral plate versus the XLP® (Nuvasive, San Diego, CA) lateral plate.