The choice of lumbar interbody fusion approach influences adjacent segment motion in a cadaveric model, according to new research published in the journal Spine, the findings of which also showed that lateral lumbar interbody fusion had the least adjacent segment motion.
The study, published by Piyanat Wangsawatwong (Barrow Neurological Institute, St. Joseph’s Hospital and Medical Centre, Phoenix, USA) et al, was designed to investigate the differences in adjacent segment mobility among three types of lateral interbody fusion (LIF) technique: lateral lumbar interbody fusion (LLIF), transforaminal lumbar interbody fusion (TLIF), and posterior lumbar interbody fusion (PLIF).
According to the researchers, previous studies have concluded that LLIF, TLIF, and PLIF with posterior pedicle screw-rod fixation (PSR) “provide equivalent stability in cadaveric specimens and are comparable in fusion rate and functional outcome”.
However, long-term complications, such as adjacent segment degeneration associated with each type of interbody device, “are currently unclear” and “little is known about the biomechanical effects of interbody fusion technique on the mobility of adjacent segments”, they add.
Normalised range of motion (ROM) data at the levels adjacent to L3–L4 PSR fixation with the three different types of lumbar interbody fusion approaches were analysed in the study. Intact (n= 21) and instrumented (n= 7) L2–L5 cadaveric specimens were tested multidirectionally under pure moment loading (7.5 Nm). Analysis of variance of adjacent segment ROM among the groups was performed. Statistical significance was set at p<0.05.
Findings showed that normalised ROM was significantly greater with PLIF than with LLIF in all directions at both proximal and distal adjacent segments (p≤0.02) except for axial rotation at the distal adjacent segment (p=0.07).
TLIF also had greater normalised ROM than LLIF during lateral bending at the proximal adjacent segment (p=0.008) and during flexion, extension, and lateral bending at the distal adjacent segment (p≤0.03). Normalised ROM was not significantly different between PLIF and TLIF.
Speaking to Spinal News International, Wangsawatwong said: “Previously, most of the studies about the differences of LIF techniques focused on the fusion level stability. This study demonstrated that the adjacent segment stability is also influenced by the LIF techniques.
“We hypothesised that the differences between LIF procedures, including inherent tissue dissection, the shapes and sizes of interbody devices, and their placement affect the alignment of the fusion segment, which could affect the motion of adjacent segments.
“Although the etiology and progression of adjacent segment disease remains the focus of much research, it is plausible that changes in adjacent segment stability may be a risk factor for longer term progression and development of adjacent segment disease. Increased segmental range of motion for example, may increase or alter intervertebral disc stress in a manner that is adverse to biological health.”