Biomechanical analysis of lateral interbody fusion strategies for adjacent segment degeneration in the lumbar spine.
Surgical treatment of symptomatic adjacent segment disease (ASD) typically involves extension of previous instrumentation to include the newly affected level(s). Disruption of the incision site can present challenges and increases the risk of complication. Lateral-based interbody fusion techniques may provide a viable surgical alternative that avoids these risks. This study is the first to analyze the biomechanical effect of adding a lateral-based construct to an existing fusion.



The study aimed to determine whether a minimally invasive lateral interbody device, with and without supplemental instrumentation, can effectively stabilize the rostral segment adjacent to a two-level fusion when compared with a traditional posterior revision approach.



This is a cadaveric biomechanical study of lateral-based interbody strategies as add-on techniques to an existing fusion for the treatment of ASD.



Twelve lumbosacral specimens were non-destructively loaded in flexion, extension, lateral bending, and torsion. Sequentially, the tested conditions were intact, two-level transforaminal lumbar interbody fusion (TLIF) (L3-L5), followed by lateral lumbar interbody fusion procedures at L2-L3 including interbody alone, a supplemental lateral plate, a supplemental spinous process plate, and then either cortical screw or pedicle screw fixation. A three-level TLIF was the final instrumented condition. In all conditions, three-dimensional kinematics were tracked and range of motion (ROM) was calculated for comparisons. Institutional funds (<$50,000) in support of this work were provided by Medtronic Spine.



The addition of a lateral interbody device superadjacent to a two-level fusion significantly reduced motion in flexion, extension, and lateral bending (p<.05). Supplementing with a lateral plate further reduced ROM during lateral bending and torsion, whereas a spinous process plate further reduced ROM during flexion and extension. The addition of posterior cortical screws provided the most stable lateral lumbar interbody fusion construct, demonstrating ROM comparable with a traditional three-level TLIF.



The data presented suggest that a lateral-based interbody fusion supplemented with additional minimally invasive instrumentation may provide comparable stability with a traditional posterior revision approach without removal of the existing two-level rod in an ASD revision scenario.
Orthopedic Biomechanics Laboratory, Department of Orthopedic Surgery, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Davis Building Rm 6006, Los Angeles, CA 90048, USA. Electronic address: Melodie.Metzger@cshs.org.
Melodie F
MF
Metzger
Orthopedic Biomechanics Laboratory, Department of Orthopedic Surgery, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Davis Building Rm 6006, Los Angeles, CA 90048, USA.
Samuel T
ST
Robinson
Orthopedic Biomechanics Laboratory, Department of Orthopedic Surgery, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Davis Building Rm 6006, Los Angeles, CA 90048, USA.
Ruben C
RC
Maldonado
Medtronic Spinal Applied Research, Medtronic Spine, 2600 Sofamor Danek Dr, Memphis, TN 38132.
Jeremy
J
Rawlinson
Department of Neurological Surgery, Keck School of Medicine, University of Southern California, 1520 San Pablo St, Suite 3800, Los Angeles, CA 90033, USA.
John
J
Liu
Department of Neurological Surgery, Keck School of Medicine, University of Southern California, 1520 San Pablo St, Suite 3800, Los Angeles, CA 90033, USA.
Frank L
FL
Acosta
D001696:Biomechanical Phenomena; D001860:Bone Plates; D002102:Cadaver; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D065289:Pedicle Screws; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*
Adjacent segment disease; Biomechanics; Degeneration; LLIF; Lateral interbody fusion; Lumbar; Minimally invasive; Range of motion; Supplemental fixation