Biomechanics of posterior instrumentation in L1-L3 lateral interbody fusion: Pedicle screw rod construct vs. transfacet pedicle screws.
BACKGROUND
The use of pedicle screws is the gold standard for supplemental posterior fixation in lateral interbody fusion. Information about the performance of transfacet pedicle screws compared to standard pedicle screws and rods in the upper lumbar spine with or without a lateral interbody fusion device in place is limited.


METHODS
Fifteen fresh frozen human cadaveric lumbar spine segments (T12-L4) were studied using standard pure moment flexibility tests. Specimens were divided into two groups to receive either bilateral transfacet pedicle screws (n=8) or bilateral pedicle screws (n=14). Stability of each motion segment (L1-L2 and L2-L3) was evaluated intact, with posterior instrumentation with an intact disc, with posterior instrumentation and a lateral interbody fusion device in place, and following cyclic loading with the interbody device and posterior instrumentation still in place. Both raw values of motion (range of motion, lax zone and stiff zone) and normalized mobility (ratios to intact) were analyzed for each case.


RESULTS
In terms of immediate stability, transfacet pedicle screws performed equivalent to similarly sized pedicle screws, both with intact disc and with lateral interbody fusion device in all directions of loading. Stability following cyclic loading decreased significantly during lateral bending and axial rotation.


CONCLUSIONS
Posterior fixation with transfacet pedicle screws provides equivalent immediate stability to similarly sized pedicle screws. However, in the presence of a lateral interbody fusion device, pedicle screws seem to resist loosening more and may be a better option for fusion in the upper lumbar spine.
Department of Clinical Biomedical Sciences, Charles E. Schmidt College of Medicine at Florida Atlantic University, Boca Raton, Fort Lauderdale, FL, USA; Less Exposure Surgery Specialists Institute (LESS Institute), Fort Lauderdale, FL, USA. Electronic address: Kingsleychin@gmail.com.
Kingsley R
KR
Chin
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA.
Anna G U
AG
Newcomb
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA.
Marco T
MT
Reis
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA.
Phillip M
PM
Reyes
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA.
Grace A
GA
Hickam
Less Exposure Surgery Specialists Institute (LESS Institute), Fort Lauderdale, FL, USA.
Josue
J
Gabriel
Less Exposure Surgery Specialists Institute (LESS Institute), Fort Lauderdale, FL, USA.
Fabio J R
FJ
Pencle
Less Exposure Surgery Specialists Institute (LESS Institute), Fort Lauderdale, FL, USA.
Roger D
RD
Sung
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA.
Neil R
NR
Crawford
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods
Facet screw; Lateral interbody; Less Exposure Surgery; Lumbar biomechanics; Lumbar fusion; Pedicle screw