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traumatic spondylolisthesis of the axis , or hangman 's fracture , is a common injury type of high cervical spine and the second most common fracture of axis .
it involves bilateral c2 pars interarticularis fracture with a variable degree of displacement of c2 on c3 vertebrae9,19 ) .
although most hangman 's fractures are treated conservatively2,20 ) , surgery is usually preferable in cases of highly unstable hangman 's fracture and fusion failure after rigid arthrodesis3,5,14,19,21 ) .
an anterior approach , however , does not address the detached posterior arch of c2 and instability remained during flexion and extension7 ) . among the different posterior approaches , direct repair of the pars fracture with a screw across the fracture line
although posterior c1-c3 wiring techniques have also been described , these techniques have required postoperative halo - thoracic immobilization14 ) .
posterior c1-c3 screw and rod fixation can offer good results in terms of alignment and stabilization of spine with a low level of pseudoarthrosis12 ) .
another posterior stabilization strategy uses a c2 pars screw connected to a c3 lateral mass screw .
this technique addresses the detached posterior arch of c2 by pinning the fractured pars while simultaneously addressing instability at the disc by immobilizing c2 relative to c3 .
therefore , posterior c2-c3 fixation more effectively stabilizes a hangman 's fracture than anterior cervical plating7 ) . in this study
, we review our clinical experience of posterior c2-c3 fixation for the 13 patients with unstable hangman 's fracture and evaluated the clinical and radiological outcomes with a literature review .
thirteen consecutive patients with unstable hangman 's fracture were enrolled who required posterior c2-c3 fixation using the polyaxial screw - rod system(depuy / synapse , switzerland ) between july 2007 and june 2010 .
all patients were classified and selected using classification of hangman 's fracture which was proposed by levine and edwards to evaluate15,16 ) .
type ii has unstable disc disruption and significant c2-c3 angulation and translation ( > 3 mm ) .
type iia is unstable due to flexion - distraction injury and has more angulation than type 2 without translation ( fig .
surgical stabilization was recommended in levine - edwards type iia and iii fractures with significant unstable dislocation .
surgical treatments were performed in patient who showed poor reduction or nonunion after rigid external orthosis , neurologic deficit or unstable combination fracture at the presentation .
dynamic plain radiographs were obtained on postoperative 1 day , 1 week , and then at 1 , 2 , 6 , and 12 months and computed tomographic ( ct ) evaluation was done at postoperative 12 months in all patients for evaluation of bone fusion .
the adequacy of fusion was determined at approximately four , six and 12 months postoperatively .
pseudoarthrosis was defined as a motion > 2.0 mm between the laminae at the base of the spinous processes between the upper and lowermost fixed and fused levels on the flexion / extension plain radiographs .
concurrently , clinical outcomes were evaluated using neck disability index ( ndi ) scores and visual analogue scale ( vas ) scores during preoperative and postoperative follow up period22 ) .
the measurement was assessed using a 10-point vas with endpoint anchors of no pain ( 0 points ) and severe pain ( 10 points ) .
the ndi questionnaire is comprised of 10 single items related to activities of daily living .
each item has six predefined response categories , coded 0 - 5 on an ordinal scale .
the scores reflected either the degree of neck pain or the degree of difficulty in performing certain actions due to neck pain . the lowest score ( 0 ) represented no problem or pain , whereas the highest score ( 5 ) represented maximum problems or pain .
the pre- and postoperative arm and neck symptom vas scores and ndi scores were compared using two - sample t tests paired for means . a p value of < 0.05 was regarded as significant .
the patient was carefully turned to the prone position and the patient 's head was placed in a mayfield cranial fixation device with fluoroscopic guidance to assess the spinal alignment as well as to localize the c2-c3 levels .
the lateral masses were exposed in a subperiosteal fashion to the lateral margins of the facet joints .
once the deformity was reduced , the lateral masses to be fused were decorticated with the drill .
great care was taken not to disturb the capsule at adjacent levels in order to prevent any iatrogenic instability .
pedicle screws were used at c2 and lateral mass screws were used at c3 under the c - arm guidance ( fig .
2 ) . a rod was prepared to the appropriate length and contour that it would easily pass through the heads of all polyaxial screws .
once the rod was positioned , it was secured to the heads of the screws using outer nuts .
bony fusion was performed by packing allograft bone and demineralized bone matrix ( dbm ) into the facet joints , around the decorticated lateral masses lateral to the rod and laminae . during the entire procedure ,
the patient was carefully turned to the prone position and the patient 's head was placed in a mayfield cranial fixation device with fluoroscopic guidance to assess the spinal alignment as well as to localize the c2-c3 levels . the patient
the lateral masses were exposed in a subperiosteal fashion to the lateral margins of the facet joints .
once the deformity was reduced , the lateral masses to be fused were decorticated with the drill .
great care was taken not to disturb the capsule at adjacent levels in order to prevent any iatrogenic instability .
pedicle screws were used at c2 and lateral mass screws were used at c3 under the c - arm guidance ( fig .
a rod was prepared to the appropriate length and contour that it would easily pass through the heads of all polyaxial screws .
once the rod was positioned , it was secured to the heads of the screws using outer nuts .
bony fusion was performed by packing allograft bone and demineralized bone matrix ( dbm ) into the facet joints , around the decorticated lateral masses lateral to the rod and laminae . during the entire procedure ,
five patients with type iia hangman 's fracture and 8 patients with type iii hangman 's fracture were enrolled .
the mean follow - up period was 17.2 months ( range 12 to 32 months ) .
vas score was gradually decreased during the follow - up period and the mean vas score was decreased up to 2.070.8 at final follow - up .
this difference between preoperative and final follow - up vas score was statistically significant ( p<0.001 ) by paired t - test ( fig .
ndi was gradually decreased during the follow - up period and the mean ndi was decreased up to 22% points at final follow - up .
this difference between preoperative and final follow - up ndi score was statistically significant ( p<0.001 ) by paired t - test ( fig .
immediate postoperative ct scan was performed in the patient with screw malposition which showed suboptimal screw placement with wide fracture gap ( fig .
hangman 's fracture is the second most common fracture of the second cervical vertebra ( c2 ) .
it involves a bilateral arch fracture of the c2 pars interarticularis with variable displacement of c2 on c37 ) . among different classifications for hangman 's fracture ,
type i lesion is usually considered stable with no angulation and displacement on c2-c3 , whereas types ii , iia , and iii are usually considered unstable .
these unstable types are combined with the injury of the c2-c3 disc and the anterior longitudinal ligament . in type ii and type iii hangman 's fracture ,
extension forces have been implicated in the disruption of the anterior longitudinal ligament , posterior longitudinal ligament , and c2-c3 disc . in most cases of hangman 's fracture ,
rigid immobilizations such as halo - vest are used for cases of great displacement . in regard to the unstable hangman 's fracture , the treatment is still controversial .
pseudoarthrosis , anterior dislocation , angulation of c2 over c3 , and recurrent axial pain were observed in about 60% of the cases of types
ii , iia , and iii , which were primarily treated with conservative therapy10,11,20 ) . majority of authors recently suggest that the presence of discoligamentous injury on top of bony injury would require surgery .
another reason for surgery is the shortening the course of treatment3 - 4,19,21,24 - 25 ) .
the goals in the surgical treatment of types ii and iii hangman 's fracture are reduction , stabilization , and maintenance of alignment . surgical stabilization has been described in both anterior and posterior approaches . the anterior approach , which has the advantage of technical ease and a relatively short fusion construct , involves a c2-c3 discectomy with interbody fusion and plating16,25 )
. an anterior approach , however , does not address the detached posterior arch of c2 , and the anterior interbody fusion of c2-c3 alone is inefficient for 3 column discoligamentous injuries like types ii and iii hangman 's fracture . among the different posterior approaches , direct repair of the pars fracture with a screw across the fracture line
however , direct pars repair does not address instability at the disc . the main advantage of this technique is not having to sacrifice any normal motion of the c2 segment and fixating only the fractured bones of c2 .
however , it can be used only in cases with minimal or no c2-c3 disc injury .
although posterior c1-c3 wiring techniques have also been described , these techniques require postoperative halo - thoracic immobilization4 ) .
polyaxial screw and rod fixation system has been developed and is widely used as a standard instrument . in this system ,
the screws can be placed first and the rod can be contoured in multiple planes . as a result ,
the screw?rod system is able to more effectively accommodate variations in size , spacing , and morphology of the lateral masses .
recent studies have also reported that the biomechanical comparison of stabilization techniques on hangman 's fracture and posterior c2-c3 screw and rod construction was found to be more effective on the stabilization of hangman 's fracture than anterior cervical plating and c2 pars screwing7 ) . in the same cadaver study ,
this technique provided significantly better biomechanical stability , especially during lateral bending and axial rotation compared with anterior c2-c3 plating .
first , it provides c2-c3 stabilization and restoration of the posterior elements of the axis .
second , the construct behaves similarly to the tension bands against flexion , lateral bending , and axial rotation2,7 ) .
pedicle screw fixation is a biomechanically stronger repair method and requires only a posterior approach1,17 ) .
in addition , pedicle screw instrumentation through a single stage posterior approach offered better biomechanical stability in 3 column spinal injury .
however , pedicle screw placement is technically demanding because of large individual variations in the pedicle dimensions and course of the vertebral artery .
therefore , the successful placement of cervical pedicle screws requires a 3-dimensional knowledge of the pedicle morphology to identify ideal screw axis accurately and to avoid neurovascular injury1,8,17 ) .
ct scanning with 3-dimensional reconstruction or an magnetic resonance image ( mri ) evaluation of the spine is essential for the detection of individual variations in the dimensions of the pedicle before surgery .
although posterior c2-c3 fixation for unstable hangman 's fracture offers biomechanical stability without additional treatment , there are some prerequisite conditions for achievement of good clinical and radiological results .
complete reduction and close adhesion of fracture gap should be achieved before the insertion of c2 screw . and , we have to press down the screw during insertion of c2 pedicular screw not to make fracture gap wide . even if complete reduction is not achieved before the insertion of pedicle screws , bicortical purchase of c2 pedicular screw , or posterior c1-c3 fixation ,
in the treatment of the patients with unstable hangman 's fracture , posterior c2-c3 fixation is an effective and curative treatments to achieve cervical spinal stability .
posterior c2-c3 fixation can offer high solid fusion rate and good clinical outcomes for axial neck pain .
although further studies are required to compare its clinical results with other posterior fixation , we cautiously suggest that the posterior c2 to c3 fusion can be considered for primary surgical treatment in patient with unstable hangman 's fracture when we can achieve complete reduction intraoperatively .
objectivethis is a retrospective review of 13 unstable hangman 's fractures who underwent posterior c2 - 3 fixation to describe clinical outcomes with a literature review.methodsthirteen patients for unstable hangman 's fracture were enrolled between july 2007 and june 2010 were included in this study . 
 the medical records of all patients were reviewed . 
 concurrently , clinical outcomes were evaluated using neck disability index ( ndi ) scores and visual analogue scale ( vas ) scores during preoperative and postoperative follow up period . 
 plain radiographs were obtained on postoperative 1day , 1week , and then at 1 , 2 , 6 , and 12 months . 
 ct was done at postoperative 12 months in all patients for evaluation of bone fusion . 
 the mean period of clinical follow - up was 17 months.resultsmean age were 43 years old . 
 bone fusion was recognized in all cases at the final follow - up . 
 the average preoperative vas score for neck pain was 8.31.1 , while the final follow - up vas score was 2.070.8 ( p<0.001 ) . 
 the average immediate postoperative ndi was 84% points and final ndi was 22% points ( p<0.001 ) . 
 there were one case of infection and 1 case of screw loosening.conclusionin the treatment of the patients with unstable hangman 's fracture , posterior c2-c3 fusions is effective and curative treatments to achieve cervical spinal stability .