Abstract:
Introduction: Low bone mineral density in patients undergoing lumbar spinal surgery with
screws is an especially difficult challenge because poor bone quality can severely compromise themaximum achievable purchase of the screws. Wide posterior approaches to the lumbarspine, exposing
lateral to the facet joints and onto transverse processes causes an additional degree of muscular damage
and blood loss not present with a simple laminectomy. A cortical bone trajectory (CBT) of the
pediclescrewhas been proposed as an alternative to prevent screw pullout and decrease the morbidity
Associated with the wide posterior approach to the spine. The CBT screw follows a lateral path in the
transverse plane and caudocephalad path in the sagittal plane. This technique has been advocated
because it is reportedly less invasive, improves screw−bone purchase and reduces neurovascular injury.
Materials and methods: Between January 2016 and March 2016, seven patients (2 men and 5
women) underwent transforaminal lumbar interbody fusion (TLIF) using the cortical bone trajectory
instead of traditional pediclescrew fixation for degenerative spondylolisthesis of the lumbar spine. The
cortical screws where placed with the assistance of the BrainLab Curve navigation systemand the
Siemens Artis Zee multi-purpose system.
Results: The average patient age was 63,5 years (range 55 – 72 years). Prior to surgery, all
patients underwent MRI, CT and DEXA scans. Low vertebral bone mineral density (osteoporosis and
osteopenia)was found in three cases. The L3 to S1 levels where instrumented. For the L3 and L4
pedicles, we used 5,5x35 mm polyaxial screws, for L5 - 6,5x35 mm screws. For S1 we used a different
trajectory of the screw, oriented to engage with the high-density bone by penetrating the S1 superior
endplate. This insertion technique allowed a larger 7,5 x 40 mm screw to be used, thus increasing the
stability of the instrumentation construct. We obtained good postoperative results in all seven cases.
Considerable improvement in both back and leg pain was achieved. In terms of complications, one case
of pedicle fracture at the insertion site on the facetectomy side occurred. No dural tear, superior facet
violation or screw misplacement where encountered. The mean operation time, radiation exposure and
blood loss was significantly less than in the traditional lumbar fusion surgery.
Conclusion: We present early clinical results of a new technique that appeared to have a better
fixation profile in laboratory testing. The CBT represents a good alternative option to obtain fixation for
the lumbar spine, even in case of low bone quality.
Description:
Department of Neurosurgery, Nicolae Testemitanu State University of Medicine and Pharmacy, Chisinau, Republic of Moldova, The 6th International Medical Congress for Students and Young Doctors, May 12-14, 2016