Cervical pedicle morphometry in a Latin American population

Abstract

The goal of this study was to conduct a detailed computed tomography (CT) assessment in the Brazilian population of the screw starting point, trajectory, and dimensions of pedicle in the cervical spine.Two hundred consecutive patients were retrospectively evaluated using cervical spine CT, with imaging reconstruction of each cervical vertebrae in the axial plane with 2 mm, and in sagittal reconstructions with 3 mm. Parameters in axial plane included the pedicle width (PW), pedicle axis length (PAL), pedicle transverse angle (PTA), and the distance from the entry point to the point between the lamina and spinous process (DEP). Measurements in the sagittal plane involved the pedicle height (PH) and the pedicle sagittal angle (PSA).The mean PW and PH were smaller in females than in males in all cervical vertebrae, but there were no significant differences of PTA among genders. PSA ranged from 15.2° to 23.7°. Mean values of PAL and DEP had a tendency to decrease from the proximal to distal cervical vertebrae. PW was <4 mm in 7.5% of men (C3) and 25% of women (C3), and <4.5 mm in 20% (C3 male) and 66% (C3 female). The intra- and inter-observer reliability were very good for the tomographic measurement of PW, and good for PH. For PAL, the intraobserver reliability was good, but the interobserver reliability varied from moderate to good. Considering PTA and PSA, the intraobserver reliability was good, but the interobserver reliability moderate for PTA and poor or fair for PSA. DEP measurements showed poor intraobserver reliability, and poor or moderate interobserver reliability.Our results presented similar trend of previous studies, but the frequency of patients with PW <4.5 mm in our population is higher, suggesting an increased risk during the attempting of transpedicular screw technique.

Accuracy of a patient‐specific 3D printed drill guide for placement of cervical transpedicular screws

“…A minimum cervical pedicle width of 4.5-5 mm has been recommended for placement of 3.5 mm screws in humans, thus limiting the SDPWR to a maximum of 0.7-0.78. [11][12][13] The mean SDPWR was therefore similar to the recommendations established in humans for 3.5 mm, 2.7 mm, and 2.4 mm screws in the current study, with SDPWR approximating 0.74, 0.76, and 0.79, respectively. Placement of smaller screws would have reduced the risk of vertebral canal breach but would have compromised implant strength.…”

“…10 A minimum pedicle width of 4.5 mm is recommended for placement of 3.5 mm CPS, although 5 mm was required in one study. [11][12][13] In dogs, Watine et al assessed the implantation corridors through the vertebral bodies of 86 C2-C6 vertebrae. The majority (68.6%) of these corridors measured less than 2.5 mm in diameter in dogs weighing on average 22 kg.…”

Estudo morfométrico do atlas

“…A anatomia do atlas de nossa população pode diferir de outras, assim os parâmetros anatômicos de C1 devem ser estudados para verificar se a fixação da massa lateral pode ser realizada e aceita como técnica padrão. Da mesma forma que outras diferenças anatômicas foram previamente descritas na literatura quando comparadas diferentes raças e etnias, 17 acreditamos que os dados obtidos em estudos prévios devem ser utilizados com cautela, pois podem não ser universalmente aceitos. Mesmo que estudos sobre as características da anatomia cirúrgica do atlas utilizando espécimes cadavéricos tenham sido realizados, ainda existe controvérsia com relação à trajetória e ao ponto de entrada ideal do parafuso de massa lateral de C1.…”

Easy method to simplify “freehand” subaxial cervical pedicle screw insertion

“…[ 1 10 11 12 13 14 15 ] The wide variability of pedicle size in cervical region complicates the choice of standard bony landmarks, necessary to determine the optimal screw entry point. [ 16 17 18 ] According to the anthropometric data the “safest” vertebrae for SCPS are C6 and C7, due to the larger diameter of pedicles,[ 1 3 11 16 17 18 19 ] besides, more than 95% of C7 vertebrae do not contain a vertebral artery. [ 20 ] “Most dangerous” vertebrae for SCPS are C3–C5, the risk of neurovascular injury is much higher due to smaller diameter and steep slope of axis of the pedicle.…”