Morphometric measurement of the lumbosacral spine for minimally invasive cortical bone trajectory implant using computed tomography.
OBJECTIVE
The cortical bone trajectory (CBT) is a novel lumbar pedicle screw trajectory. The aim of this study was to conduct a detailed morphometric measurement of the lumbosacral spine for CBT pedicle screw, using the inferior facet of the cephalad level as a bony landmark.


METHODS
The three-dimensional computed tomography (3D-CT) scans of 86 adults who underwent examination of the lumbosacral spine were studied. The distances from the starting point to the inferior, lateral and medial border of the inferior facet of the cephalad level were measured. The angles formed between the screw trajectory and the sagittal plane, the superior endplate of the vertebral body and the posterior margin of the pars interarticularis were defined as the transverse angle (TA), cephalad angle 1 (CA1) and cephalad angle 2 (CA2), respectively.


RESULTS
The distances from the inferior border of inferior facet to the starting point from L1 to S1 were 8.9, 6.3, 4.1, 2.9, 1.4 and 0 mm, respectively. The distances from the medial border of the inferior facet to the starting point from L1 to S1 were between 3 and 4 mm. TA from L1 to S1 was 9.0°, 9.6°, 11.3°, 13.5°, 15.5°, and 8.2°, respectively. CA1/CA2 from L1 to S1 was 26.7°/38.7°, 26.0°/38.7°, 26.9°/38.0°, 24.4°/37.2°, 22.9°/35.1° and 18.4°/47.8°, respectively. The maximum screw diameters from L1 to S1 were 4.8, 5.1, 6.1, 6.8, 7.8, and 6.1 mm, respectively. Twenty-five millimeter can serve as a safe maximum length of CBT pedicle screws.


CONCLUSIONS
The inferior facet of the cephalad level is an attractive bony landmark for establishing a starting point of CBT for minimally invasive spine surgery.
Department of Orthopaedic Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88 Jiefang Road, Hangzhou, Zhejiang, China. zhanghua068@zju.edu.cn.
Hua
H
Zhang
Department of Orthopaedic Surgery, University of California at Los Angeles, 10833 Le Conte Avenue, 76-143 CHS, Los Angeles, CA, USA.
Remi Musibau
RM
Ajiboye
Orthopaedic Spine Surgery, UCLA School of Medicine, 1250 16th Street, Suite 3145D, Santa Monica, CA, USA.
Arya Nick
AN
Shamie
Department of Orthopaedic Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88 Jiefang Road, Hangzhou, Zhejiang, China.
Qionghua
Q
Wu
Department of Orthopaedic Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88 Jiefang Road, Hangzhou, Zhejiang, China.
Qixin
Q
Chen
Department of Orthopaedic Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88 Jiefang Road, Hangzhou, Zhejiang, China.
Weishan
W
Chen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D065289:Pedicle Screws; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000601:surgery; D013123:Spinal Fusion / Q000379:methods*; D014057:Tomography, X-Ray Computed; D055815:Young Adult; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging
Cortical bone trajectory; Facet; Lumbosacral spine; Pedicle