Deviation Analysis of Atlantoaxial Pedicle Screws Assisted by a Drill Template

FEATURE ARTICLE 

Deviation Analysis of Atlantoaxial Pedicle Screws Assisted by a Drill Template

Yong Hu, MD; Zhen-Shan Yuan, MD; Christopher K. Kepler, MD, MBA; Todd J. Albert, MD; Hui Xie, MD; Jian-Bing Yuan, PhD; Wei-Xin Dong, MD; Cheng-Tao Wang, PhD

• Orthopedics
• May 2014 - Volume 37 · Issue 5: e420-e427
• DOI: 10.3928/01477447-20140430-51

Abstract

Although C1–C2 pedicle screw fixation provides an excellent fusion rate and rigid fixation, this technique has a potential risk. It is essential to develop an accurate screwing method to avoid this neurovascular injury. To develop and validate the accuracy of a novel navigational template for C1–C2 pedicle screw placement in cadaveric specimens, computed tomography scans with 1-mm-wide cuts were obtained of 32 cadaveric cervical specimens. The authors developed 64 three-dimensional full-scale templates that were created by computer modeling with a rapid prototyping technique from the computed tomography data. Drill templates were constructed with a custom trajectory for each level and side. The drill templates were used to guide the establishment of a pilot hole for screw placement. The average distances between ideal and actual entry points of the C1 pedicle screws in the x, y, and z axes were 0.16±0.46 mm, 0.11±0.52 mm, and −0.01±0.54 mm, respectively, on the left side and 0.11±0.49 mm, 0.01±0.56 mm, and −0.09±0.59 mm, respectively, on the right side. The average distances between ideal and actual entry points of the C2 pedicle screws in the x, y, and z axes were 0.05±0.54 mm, 0.20±0.59 mm, and −0.06±0.58 mm, respectively, on the left side and 0.17±0.55 mm, 0.1±0.58 mm, and −0.01±0.49 mm, respectively, on the right side. Factors related to human error and imprecision are responsible for most malpositioning of instrumentation. The rapid prototyping drill template for C1–C2 screw placement is described to minimize human error, although it introduces error related to computer software and variation in manufacturing.

Aunque la fijación de tornillo pedículo C1 -C2 proporciona una tasa de fusión excelente y fijación rígida , esta técnica tiene un riesgo potencial. Es esencial para desarrollar un método de atornillado preciso evitar esta lesión neurovascular . Desarrollar y validar la exactitud de una plantilla de navegación novedosa para C1 -C2 colocación de tornillos pediculares en especímenes cadavéricos , la tomografía computarizada con 1 - mm de ancho cortes se obtuvieron de 32 muestras cervicales de cadáveres . Los autores desarrollaron 64 tridimensionales plantillas a escala real que fueron creados por modelos de computadora con una técnica rápida de prototipos a partir de los datos de la tomografía computarizada . Plantillas de perforación se construyeron con una trayectoria personalizada para cada nivel y lado. Las plantillas de perforación se utilizan para guiar la creación de un agujero piloto para la colocación del tornillo . Las distancias medias entre puntos de entrada ideales y reales de los tornillos pediculares C1 en los ejes x, y, z fueron 0,16 ± 0,46 mm , 0,11 ± 0,52 mm , y -0,01 ± 0,54 mm, respectivamente , en el lado izquierdo y 0,11 ± 0,49 mm , 0,01 ± 0,56 mm , y -0,09 ± 0,59 mm, respectivamente , en el lado derecho . Las distancias medias entre puntos de entrada ideales y reales de los tornillos pediculares C2 en los ejes x, y, z fueron 0,05 ± 0,54 mm , 0,20 ± 0,59 mm , y -0,06 ± 0,58 mm, respectivamente , en el lado izquierdo y 0,17 ± 0,55 mm , 0,1 ± 0,58 mm , y -0,01 ± 0,49 mm, respectivamente , en el lado derecho . Factores relacionados con el error humano y la imprecisión son responsables de la mayor mala posición de la instrumentación . La plantilla de perforación rápida de prototipos para C1 -C2 colocación del tornillo se describe para minimizar el error humano , si bien introduce error relacionado con los programas informáticos y la variación en la fabricación

The authors are from the Department of Spinal Surgery (YH, Z-SY, HX, W-XD), Ningbo No. 6 Hospital, Ningbo, China; the Department of Orthopaedic Surgery (CKK, TJA), Thomas Jefferson University & Rothman Institute, Philadelphia, Pennsylvania; and the Institute of Biomedical Manufacturing and Life Quality Engineering (J-BY, C-TW), School of Mechanical and Power Energy Engineering, Shanghai Jiaotong University, Shanghai, China.

The authors have no relevant financial relationships to disclose.

The authors thank Dr Zheng-da Shi for his assistance with the CT data collection.

Correspondence should be addressed to: Yong Hu, MD, Department of Spinal Surgery, Ningbo No. 6 Hospital, 1059 Zhongshan East Rd, Ningbo 315040, China ( huyong610@163.com).

Received: July 25, 2013

Accepted: November 08, 2013

 

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