Biomechanics of Lateral Interbody Spacers: Going Wider for Going Stiffer

Abstract

This study investigates the biomechanical stability of a large interbody spacer inserted by a lateral approach and compares the biomechanical differences with the more conventional transforaminal interbody fusion (TLIF), with and without supplemental pedicle screw (PS) fixation. Twenty-four L2-L3 functional spinal units (FSUs) were tested with three interbody cage options: (i) 18 mm XLIF cage, (ii) 26 mm XLIF cage, and (iii) 11 mm TLIF cage. Each spacer was tested without supplemental fixation, and with unilateral and bilateral PS fixation. Specimens were subjected to multidirectional nondestructive flexibility tests to 7.5 N·m. The range of motion (ROM) differences were first examined within the same group (per cage) using repeated-measures ANOVA, and then compared between cage groups. The 26 mm XLIF cage provided greater stability than the 18 mm XLIF cage with unilateral PS and 11 mm TLIF cage with bilateral PS. The 18 mm XLIF cage with unilateral PS provided greater stability than the 11 mm TLIF cage with bilateral PS. This study suggests that wider lateral spacers are biomechanically stable and offer the option to be used with less or even no supplemental fixation for interbody lumbar fusion.

Lateral lumbar interbody fusion with unilateral pedicle screw fixation for the treatment of adjacent segment disease: a preliminary report

“…In addition to indirectly decompressing the neural structures through interbody distraction, Marchi et al have recently published that stand alone lateral interbody fusion was associated with a 91% successful fusion rate (13). In a biomechanical cadaveric study, Pimenta et al have found that a 18 mm extreme lateral interbody cage (XLIF) with unilateral pedicle screw provided greater stability than the 11 mm transforaminal lumbar interbody cage with bilateral pedicle screws (14). Treatment of ASD with LLIF allows for preservation of the anterior and posterior longitudinal ligaments, which preserves stability.…”

In Which Patients Is It Possible to Perform Standalone Lateral Lumbar Interbody Fusion Without Cage Subsidence?

“…Lumbar interbody fusion performed with lateral implants has been shown to be biomechanically superior to other constructions, 4,5 as the larger diameter hollow spacers appear to be favorable for engaging the peripheral margins of the end plate. 6 The good stiffness achieved with lateral wide implants enables standalone constructions to be performed in some cases.…”

“…For this reason, a stand-alone construction can provide good stabilization, comparable to a TLIF supplemented with pedicle screws. 4 Good results and complications from non-supplemented LLIF have been reported; [7][8][9][10][11] however, the ideal indication is not clear. Cage settling and vertebral body fracture are potential and significant complications.…”

“…Some study groups have recently discovered that the use of wider LLIF cages results in more stable biomechanical constructions 4 and decreased subsidence rates. 12,14,17 Based on this data, the use of 22mm or even wider cages is now recommended.…”

“…[1][2][3] Biomechanical features of LLIF constructions provide better rigidity than other constructions. 4,5 It uses large diameter, hollow spacers that can engage the peripheral margins of the endplate, the design and positioning of which seems to be superior to others. 6 In conventional lumbar fusion techniques, the interbody cage is always supplemented by internal fixation.…”