Does Lumbar Interbody Cage Size Influence Subsidence? A Biomechanical Study

Abstract

Study Design. An experimental laboratory-based biomechanical study. Objective. To investigate the correlation between cage size and subsidence and to quantify the resistance to subsidence that a larger cage can provide. Summary of Background Data. The assumption that a bigger interbody cage confers less subsidence has not been proven. There was no previous study that has shown the superiority of lateral cages to bullet cages in terms of subsidence and none that has quantified the correlation between cage size and subsidence. Methods. A cage was compressed between two standardized polyurethane foam blocks at a constant speed. Four sizes of bullet cages used for transforaminal lumbar interbody fusion (TLIF) and six sizes of lateral cages used for lateral lumbar interbody fusion (LLIF) were tested. The force required for a 5 mm subsidence, axial area of cages, and stiffness were analyzed. Results. A larger cage required a significantly higher force for a 5 mm subsidence. Longer bullet cages required marginal force increments of only 6.2% to 14.6% compared to the smallest bullet cage. Lateral cages, however, required substantially higher increments of force, ranging from 136.4% to 235.7%. The average force of lateral cages was three times that of bullet cages (6426.5 vs. 2115.9 N), and the average stiffness of the LLIF constructs was 3.6 times that of the TLIF constructs (635.5 vs. 2284.2 N/mm). There was a strong correlation between the axial area of cages and the force for a 5 mm subsidence. Every 1 mm2 increment of axial area corresponded to approximately 8 N increment of force. Conclusion. Cage size correlated strongly with the force required for a 5 mm subsidence. The LLIF constructs required higher force and were stiffer than the TLIF constructs. Among bullet cages, longer cages only required marginal increments of force. Lateral cages, however, required substantially higher force. Level of Evidence: N/A

Initial multi-centre clinical experience with prone transpsoas lateral interbody fusion: Feasibility, perioperative outcomes, and lessons learned

“…Lateral interbody fusion (LIF) is a well published procedure which boasts important clinical advantages including the opportunity to effect an inherently biomechanically stable fusion environment [1] , [2] , [3] , [4] , with excellent disc and foraminal height restoration [ 5 , 6 ], and quick recovery owed to reduced morbidity of the minimally invasive (MIS) retroperitoneal access [ 7 , 8 ]. LIF as traditionally described is performed with the patient in the lateral decubitus position, coronally bent over a breaking table to gain access to the lumbar spine at levels L4–5 and above [9] .…”

The Feasibility of 3D Intraoperative Navigation in Lateral Lumbar Interbody Fusion: Perioperative Outcomes, Accuracy of Cage Placement and Radiation Exposure

“…[1][2][3][4][5][6][7][8][9] Among the reasons for the increasing popularity of the lateral approach to the lumbar spine is the large working window allowing for thorough preparation of the disc space and insertion of an interbody cage which spans the apophyseal ring, decreasing the risk of subsidence compared to posterior approaches to interbody fusion. 10,11 Furthermore, the ability to place a large interbody cage to restore disc height and achieve indirect central and foraminal decompression without direct visualization of the neural elements spares the morbidity and complication profile of the posterior approach. [12][13][14][15][16][17][18] However, due to the possibility of approach-related complications including lumbosacral plexus injury, intraoperative radiographic guidance and neuromonitoring are of paramount importance.…”

Clinical and radiographic outcomes of hybrid graft in patients with Modic changes undergoing transforaminal lumbar interbody fusion

“…Cage subsidence (CS) is one of the complications that results in gradual loss of disc height (DH) and segmental lordosis (SL). Previous studies have suggested that CS is associated with osteoporosis, excessive distraction of the intervertebral space, and damage to the endplate [7][8][9][10]. Modic changes (MCs) in the lumbar endplate and subendplate bones on magnetic resonance imaging (MRI) images are classified into three types: MCs-1 is considered as the inflammatory phase or edema phase; MCs-2 is considered as the fatty phase or yellow marrow phase; MCs-3 is considered as the osteosclerosis phase.…”