| [Objective]: Hangman fracture is a common injury of upper cervicalspine. With the development of cervical pedicle screw fixation technique,Some authors advocated C2pedicle lag screw fixation with or withoutC3pedicle screw fixation for unstable Hangman fracture (C2Pars interarticu-laris fractures). Reduction of fracture could be achieved by C2pedicle lagscrew technique, As long as the C2Pars interarticularis does not presenthypoplasia, High-riding of vertebral artery, Or fracture fragments occupyingthe spinal canal or transverse foramen. Pedicle lag screw fixation includes twokinds of techniques that are full threaded screws with proximal reamingand half threaded screw without proximal reaming. It has been reported thatbilateral Pedicle fracture could occur at any site of the axis ring, And60%of the fractures were asymmetric. In1993, Starr found that the fractureline could involve the posterior wall of vertebral body besides the fracture ofPars interarticularis. Clinical observation found that the fracture end ofC2Pedicle fracture could smash, Tilt, Displace and rotate. However, Themajority of vertebral body did not fracture; If present, The fracture line onlyinvolve the posterior wall of the vertebral body. The influence of these fracturesites on the choice of lag screw was unclear. Because the risk of fixation withfull threaded lag screw technique is higher, Fixation without proximal reaming should be a good choice. The different parts of the fracture in theaxis ring required use of lag screw with different lengths of thread; Otherwise,Separation of Pars interarticularis, C2,3malunion, And even vertebral artery andspinal cord injury could occur. Therefore, This study included the image data ofa group of atlantoaxial fractures patients without hangman fracture to evaluatethis issue. Using64slice CT scan and three-dimensional reconstruction andC2vertebral pedicle (Pars interarticularis) screw design, We applied Ebraheimmethod to locate the insertion point of C2pedicle screws. The fracture sites ofaxial ring were divided into fracture of posterior wall of vertebral body, Isthmusfracture and fracture of front laminar. Through observing the distance fromthe fracture line to the front cortex of C2vertebral body, We can determine thelength of thread of the lag screw that was required in different parts of fracturein hangman fractures.[Methods]: We included image data from185Chinese Han patients withatlantoaxial injuries but without Hangman fracture (42cases of atlasfractures,94cases of odontoid process fracture,41cases of atlantoaxialdislocation,4cases of traumatic spondylolisthesis,4cases of C2,3hyperex-tension injury). They were admitted in the department of spinal surgery inspine surgery of the Affiliated Hospital of Luzhou Medical College from June2003to June2013, Including136males and49females. The average age was44.1years (range,22to73years). The average Height was166cm (range,149to183Height).According to X-ray films, CT scan, three-dimensional reconstruction and vascular imaging,11cases with narrowing of Parsinterarticularis of C2(width<4mm),6cases with high riding of vertebralartery,2cases with atlantoaxial rotatory dislocation,2cases with basilarinvagination and4cases with atlantoaxial infections and tumors wereexcluded. Finally, Image data of160cases was included to this study andthree-dimensional CT scan based screw trajectory designing was performed.We adopted Ebraheim method to determine the insertion point of the axislamina. The screw of vertebral pedicle selected in three-dimensional CT designwas analyzed in ADW4.4workstation and postprocessed by64row CT image.We simulated three types of fractures: the posterior wall fracture of vertebralbody（Group A）, ISthmus fracture（Group B） and front laminar fractures (GroupA). We measured the distance from screw point of C2vertebral pedicle to C2vertebral front cortex(namely the screw path length), The distance from screwpoint in C2vertebral pedicle to the position of every fracture line(namely thelength of screw required fracture line Proximal in Hangman fracture), Thedistance from different parts of fracture line distal to C2vertebral front cortex(namely the length of lag screw thread required fracture line distal inHangman fracture).[Results]: In this study,160measurement results of image data wereobtained: In the average male height of170±4.9cm; female Height average159±4.6cm; The left side of distance from screw point of C2vertebralpedicle to C2vertebral front cortex was22.1-31.8mm, with an average of27.4 ±2.6mm. The right side of distance was23.8-32.6mm, with an average of27.7±2.8mm.120cases were male. The left side of distance from screw pointof C2vertebral pedicle to C2vertebral front cortex was27.2-31.8mm, with anaverage of29.3±1.2mm. The right side of distance was26.5-32.6mm, with anaverage of28.6±2.1mm.40cases were female. The left side of distance fromthe screw point in C2vertebral pedicle to C2vertebral front cortex was22.1-27.6mm, with an average of24.8±2.5mm, and the right side of distancewas23.8-27.2mm, with an average of24.6±3.0mm. The statistical resultsshowed that the length of screw path in both left and right sides in male patientshad no significant difference (P>0.05), And that in female patients had nosignificant difference neither(P>0.05). Therefore, we computed themeasurement data of fracture line on left and right side in male and femalepatients. The statistical results showed that distance from screw point in C2vertebral pedicle to C2vertebral front cortex in male patients was longer thanthat in female patients, and it was statistically different (P <0.05). Male patientsthan female patients with high height, male patients C2pedicle into the nailpoint to the C2vertebral cortex distance longer than the female patients,correlation analysis will be conducted screw channel height and the total lengthof the patient, statistics show whether male or female patient height and C2total length of nails were positively correlated.Therefore, The measurementsresults of screw path in male and in female patients were calculated separately.In the group of patients with the fracture line in the posterior wall of vertebral body, They included240measurement data in120cases of male. Thedistance from the screw point in C2vertebral pedicle to the fracture lineproximal to the posterior wall fracture of vertebral body (screw length) was14.8-19.1mm, with an average of16.7±1.5mm. The distance from the fractureline distal to the posterior wall fracture of vertebral body to C2vertebral frontcortex (screw thread length) was9.5-13.9mm, with an average of12.2±1.9mm.While for the80measurement data in40cases of female, the distance from thescrew point in C2vertebral pedicle to the fracture line proximal to the posteriorwall fracture of vertebral body (screw length) was13.2-15.0mm, with anaverage of14.8±1.7mm. The distance from the fracture line distal to theposterior wall fracture of vertebral body to C2vertebral front cortex (screwthread length) was7.5-12.0mm, with an average of9.7±1.9mm. The statisticalresults showed that the length of lag screw thread was shorter than that of screw,and the length of the screw or screw thread in male patients was always longerthan that in female patients (P <0.05).In the group of patients with the fracture line in isthmus, They included240measurement data in120cases of male. The distance from the screw pointin C2vertebral pedicle to the fracture line proximal to isthmus (screw length)was11.4-16.3mm, with an average of13.9±1.6mm. The distance from thefracture line distal to isthmus fracture to C2vertebral front cortex (screw threadlength) was11.3-17.9mm, with an average of14.6±1.8mm. While for the80measurement data in40cases of female, The distance from the screw point in C2vertebral pedicle to the fracture line proximal to isthmus (screw length) was10.7-15.0mm, with an average of12.6±2.1mm. The distance from the fractureline distal to isthmus fracture to C2vertebral front cortex (screw thread length)was10.5-13.3mm, with an average of11.7±1.1mm. The statistical resultsshowed that there was no significant difference between the length ofscrew thread and screw in vertebral pedicle, And the length of screw thread andscrew in male patients were longer than that in female patients(P <0.05).In group of patients with the fracture line in front lamina, They included240measurement data in120cases of male. The distance from the screwpoint in C2vertebral pedicle to the fracture line proximal to frontlamina (screw length) was7.5-13.0mm, with an average of9.9±1.7mm. Thedistance from the fracture line distal to front lamina to C2vertebral front cortex(screw thread length) was15.5-20.0mm, with an average of18.0±1.5mm.While for the80measurement data in40cases of female, The distance from thescrew point in C2vertebral pedicle to the fracture line proximal to front lamina(screw length) was8.2-12.0mm, with an average of9.4±1.9mm. The distancefrom the fracture line distal to front lamina to C2vertebral front cortex(screw thread length) was12.9-17.5mm, with an average of15.1±1.7mm. Thestatistical results showed that the length of lag screw thread of vertebral pediclewas longer than that of screw, And the length of screw thread and screw in malepatients was longer than that in female patients (P <0.05).[Conclusion]:①T he distal lag screwthread required for fracture patients of C2 pedicle was different according to fracture position, sex and the length of lagscrew thread.②In this study, The length of lag screw in C2vertebral pediclewas an average of29mm in male and25mm in female.③In the group ofpatients with the fracture line in the posterior wall of vertebral body, Thedistance from the fracture line distal to the posterior wall of vertebral body toC2vertebral front cortex was an average of12mm in male and10mm in female.In the group of patients with the fracture line in isthmus, The distance from thefracture line distal to isthmus to C2vertebral front cortex was an average of15mm in male and12mm in female. In group of patients with the fracture linein front lamina, The fracture line in the front of lamina distal to C2vertebralfront cortex was an average of18mm in male and15mm in female. |
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