evolution of cervical spinal instrumentation has led to recent advancements in the treatment of complex spinal disorders stemming from numerous pathological processes . cervical fusions alone have more than doubled over the past decade and reached over 157,000 annual procedures in 2008 just in the united states alone . as a result , several authors previously alluded to varying biomechanical stressors at the cervicothoracic junction often necessitating extension of construct to the upper thoracic segments . however , pedicle screw fixation in upper thoracic vertebrae can be technically demanding as improper placement at t1 carries greater risk of canal encroachment and mediastinal compromise that lateral mass screws . consequently , safety and efficacy of thoracic screw insertion methods have been extensively described in the literature . these methods include free - hand placement , fluoroscopic guidance both with and without laminoforaminotomy , and computed tomography neuronavigation systems . fluoroscopic imaging of the upper thoracic spine , however , presents a challenge due to vertebral anatomy , patient size , interference from skull clamp or surgical table , and positioning difficulties . ct - guided systems are associated with substantial financial commitment and are not readily available at most community medical centers . in fact , a survey of spine surgeons in the uk and ireland found that only 14% of responders reported using some sort of spinal navigation equipment . additionally , both techniques increase radiation exposure to the patient and surgical team while often adding to overall surgical time . we propose a novel free - hand technique for instrumenting the pedicle of the first thoracic vertebra as a part of cervicothoracic fusion . this modification of the classic starting point and trajectory described elsewhere obviates the need for additional bone removal or expensive intraoperative imaging modalities while maintaining a high rate of successful screw placement compared to historical controls . we performed a retrospective review of 44 consecutive patients at our institution who underwent cervicothoracic fusion requiring t1 pedicle screws for any pathology between june 2009 and november 2012 . subaxial instrumentation consisted of lateral mass screws that were placed via standard techniques described elsewhere . if no deficits were identified , every patient underwent a cervical ct on post - operative day 1 . classification : grade 1 - screw completely within the vertebral body ( vb ) and pedicle , grade 2 - screw contained within pedicle - rib complex with screw tip within vb , grade 3 - screw tip located laterally or anteriorly to vb , grade 4 - screw tip perforated inferior or medial pedicle border , grade 5 - screw position that placed neural or vascular structures at risk and required removal or revision . post - operative ct scans were evaluated by three neuroradiologists as part of prospective work flow as well as by two neurosurgeons and two senior neurosurgical trainees . midline skin incision and subsequent subperiosteal dissection was used to gain exposure to cervicothoracic regions of interest . a decompressive laminectomy was performed where appropriate prior to instrumenting ; however , in no patient this was done for the purpose of localizing the t1 pedicle . the spinous process , lamina , and transverse processes of t1 were meticulously exposed in all cases . the classic starting point for the t1 pedicle screw has been described at the intersection of a line bisecting the transverse process and a line defining the lateral border of the pars . the new starting point for our free - hand method is more medial and superior . in order to expose the new starting point , electrocautery is used to define the c7/t1 articulation . in the medial - lateral direction , we first locate a point one - third of the way between the lateral border of c7 lateral mass and medial border of t1 lamina along the c7/t1 articulation [ figure 2 ] . a high speed burr is used to remove approximately 3 mm of bone from the inferior aspect of c7 lateral mass until the smooth cortical surface of the superior articular process of t1 is identified . a pilot hole drilled at the starting point on the t1 superior articular cortex delivers cancellous bone of the pedicle into view [ figure 3 ] . the 2 mm blunt , straight thoracic pedicle probe is used to cannulate the pedicle . in the cranial - caudal direction , the screw trajectory is perpendicular to the long axis of the t1 lamina [ figure 4 ] . in the medial - lateral direction , the trajectory parallels the angle between the tip of t1 spinous process and the contralateral starting point [ figure 5 ] . this trajectory stems from our observation that , in the axial plane , the geometry of the t1 vertebra from the tip of the spinous process to anterior aspect of body consistently resembles a parallelogram , with lateral borders defined by the two starting points . care is taken to appreciate perforation of cancellous bone the entire length of the pedicle and vertebral body . abrupt loss of resistance indicates a pedicle breach while an increase in resistance indicates the probe is against cortical bone and trajectory must be re - evaluated prior to further advancement . a ball - tipped probe is then carefully inserted to investigate the integrity of the tract . if a pedicle violation is suspected , the trajectory can be corrected with the straight pedicle probe . subsequently , the pedicle is prepared to a depth of 15 - 20 mm with a tap that is 0.5 mm smaller than the potential screw . a ball - tipped probe is once again introduced to confirm the integrity of the tract . once satisfied with the bony confines of the tract , a 3.5 or 4.5 mm titanium screw is inserted to a predetermined depth of 24 - 28 mm based on preoperative imaging . care must be taken to maintain the correct trajectory with screw insertion to avoid breaching the cortical margins of the developed tract . top : an image demonstrating the difference between the classic starting point and one proposed in this report . bottom : location of the t1 pedicle with respect to adjacent superficial bony landmarks an illustration ( top ) and a model ( bottom ) demonstrating the location of the starting point in the medial to lateral projection top left : medial to lateral orientation of the proposed starting point with respect to c7/t1 articulation . top right : high speed drill is used to removing the inferior few millimeters of c7 lateral mass . bottom left : the smooth cortical surface of t1 superior articular facet if uncovered once drilling is complete . bottom right : high speed drill is used to break the cortex to deliver the cancellous bone of the t1 pedicle a model ( top left ) , an illustration ( bottom left ) , and post - operative ct scan ( right ) demonstrating the cranial - caudal trajectory of the t1 pedicle screw . the screw is inserted perpendicular to the long axis of the t1 lamina a model ( top left ) and an illustration ( top right ) showing the parallelogram orientation of t1 vertebra . the medial - lateral screw trajectory is parallel to the angel between the tip of spinous process and contralateral starting point . bottom left : a model demonstrating a phantom screw inserted according to the proposed trajectory . bottom right : a post - operative ct scan showing a t1 pedicle screw following the proposed trajectory after successful placement of thoracic screws , subaxial instrumentation is completed . a detailed neurological examination is performed in pacu in the immediate post - op period . midline skin incision and subsequent subperiosteal dissection was used to gain exposure to cervicothoracic regions of interest . a decompressive laminectomy was performed where appropriate prior to instrumenting ; however , in no patient this was done for the purpose of localizing the t1 pedicle . the spinous process , lamina , and transverse processes of t1 were meticulously exposed in all cases . the classic starting point for the t1 pedicle screw has been described at the intersection of a line bisecting the transverse process and a line defining the lateral border of the pars . the new starting point for our free - hand method is more medial and superior . in order to expose the new starting point , electrocautery is used to define the c7/t1 articulation . in the medial - lateral direction , we first locate a point one - third of the way between the lateral border of c7 lateral mass and medial border of t1 lamina along the c7/t1 articulation [ figure 2 ] . a high speed burr is used to remove approximately 3 mm of bone from the inferior aspect of c7 lateral mass until the smooth cortical surface of the superior articular process of t1 is identified . a pilot hole drilled at the starting point on the t1 superior articular cortex delivers cancellous bone of the pedicle into view [ figure 3 ] . the 2 mm blunt , straight thoracic pedicle probe is used to cannulate the pedicle . in the cranial - caudal direction , the screw trajectory is perpendicular to the long axis of the t1 lamina [ figure 4 ] . in the medial - lateral direction , the trajectory parallels the angle between the tip of t1 spinous process and the contralateral starting point [ figure 5 ] . this trajectory stems from our observation that , in the axial plane , the geometry of the t1 vertebra from the tip of the spinous process to anterior aspect of body consistently resembles a parallelogram , with lateral borders defined by the two starting points . care is taken to appreciate perforation of cancellous bone the entire length of the pedicle and vertebral body . abrupt loss of resistance indicates a pedicle breach while an increase in resistance indicates the probe is against cortical bone and trajectory must be re - evaluated prior to further advancement . a ball - tipped probe if a pedicle violation is suspected , the trajectory can be corrected with the straight pedicle probe . subsequently , the pedicle is prepared to a depth of 15 - 20 mm with a tap that is 0.5 mm smaller than the potential screw . a ball - tipped probe is once again introduced to confirm the integrity of the tract . once satisfied with the bony confines of the tract , a 3.5 or 4.5 mm titanium screw is inserted to a predetermined depth of 24 - 28 mm based on preoperative imaging . care must be taken to maintain the correct trajectory with screw insertion to avoid breaching the cortical margins of the developed tract . top : an image demonstrating the difference between the classic starting point and one proposed in this report . bottom : location of the t1 pedicle with respect to adjacent superficial bony landmarks an illustration ( top ) and a model ( bottom ) demonstrating the location of the starting point in the medial to lateral projection top left : medial to lateral orientation of the proposed starting point with respect to c7/t1 articulation . top right : high speed drill is used to removing the inferior few millimeters of c7 lateral mass . bottom left : the smooth cortical surface of t1 superior articular facet if uncovered once drilling is complete . bottom right : high speed drill is used to break the cortex to deliver the cancellous bone of the t1 pedicle a model ( top left ) , an illustration ( bottom left ) , and post - operative ct scan ( right ) demonstrating the cranial - caudal trajectory of the t1 pedicle screw . the screw is inserted perpendicular to the long axis of the t1 lamina a model ( top left ) and an illustration ( top right ) showing the parallelogram orientation of t1 vertebra . the medial - lateral screw trajectory is parallel to the angel between the tip of spinous process and contralateral starting point . bottom left : a model demonstrating a phantom screw inserted according to the proposed trajectory . bottom right : a post - operative ct scan showing a t1 pedicle screw following the proposed trajectory after successful placement of thoracic screws , subaxial instrumentation is completed . a detailed neurological examination is performed in pacu in the immediate post - op period . between june 2009 and november 2012 , 44 consecutive patients underwent a posterior cervicothoracic instrumented procedure with pedicle screws placed to at least t1 . for all cases , t1 pedicle screws were inserted utilizing the above - described technique . there were 21 males and 23 females in the study and the mean age of the patient cohort was 60.9 years . there were 87 total t1 pedicle screws included in the final analysis [ table 1 ] . one patient underwent c2 to t2 fixation with placement of only a unilateral left t1 pedicle screw due to right t1 pedicle fracture . a c3-t1 fusion was the most common construct , placed in 30 ( 68.2% ) patients . there were no new neurologic deficits or returns to the operating room secondary to hardware placement . heary grade 1 placement occurred in 72 ( 82.8% ) screws , grade 2 in 4 ( 4.6% ) screws and grade 3 in 9 ( 10.3% ) screws . all grade 2 and 3 screws breached by < 2 mm with one grade 3 screw breaching 2 - 4 mm laterally . two screws ( 2.3% ) were grade 4 placements , breaching medially by less than 2 mm [ figure 6 ] . seventy - six screws ( 87.4% ) terminated within the t1 vertebral body . at last right t1 pedicle screw ( top ) and left t1 screw ( bottom ) breached medially by less than 2 mm . as multilevel cervical instrumented fusions have become increasingly common over the past decade , many surgeons have adapted the practice of extending posterior cervical constructs past the cervicothoracic junction ( ctj ) . key aspects include traversing the ctj to a neutral vertebra for longer cervical fusions and the avoidance of ending constructs at the ctj . the t1 facet joint is oriented in the coronal plane , and limits motion in flexion and extension more than at the cervical joints . at all thoracic levels , the medial pedicle cortex is two to three times thicker than the lateral cortex conferring added strength against pedicle breach . additionally , t1 pedicle screws have greater pull - out strength and impart enhanced stability of three - column fixation to cervical constructs when compared to lateral mass screws alone . yet another consideration supporting extension of posterior cervical constructs to t1 level is the difficulty of instrumenting the pedicle at c7 , thus presenting the option of skipping c7 altogether if necessary . pedicle screw accuracy rates in the present series are similar to slightly higher than historical controls , without the use of additional imaging or navigation . in our study of these , 85 ( 97.7% ) were heary grade 1 - 3 , with two grade 4 placements . of note , 72 ( 82.8% ) t1 screws inserted were contained completely within the pedicle and vb . furthermore , there were no clinically significant screw misplacements as defined by neurologic deficit or returns to or , further supporting the safety and efficacy of our method . kim and colleagues reviewed placement of 577 thoracic pedicle screws , with 36 ( 6.2% ) screws demonstrating moderate cortical perforation , 10 ( 1.7% ) of which violated the medial pedicle cortex . after a 10 year follow - up however , no patients in their series demonstrated any evidence of neurologic , visceral , or vascular complications , leading the authors to conclude that free - hand method of placement was accurate , reliable , and safe . the authors reported the range of thoracic free - hand screws that were contained within the pedicle to be 69 - 94% . placement accuracy specifically for upper thoracic pedicle screws has also been reviewed by several groups . the accuracy for screws completely within the pedicles was 70.9% , 81% , and 89% , respectively . of 90 pedicle screws placed from c7 to t2 , 87 ( 96.7% ) were classified as grade 1 . the classic starting point for the t1 pedicle screw as described by kim et al . is at the intersection of a line bisecting the transverse process and a line defining the lateral border of the pars . a more medial starting point facilitates visualizing the  parallelogram  , as previously described , which is crucial for medial - lateral trajectory of the proposed method . medial breaches occurred with just two of our screws , both less than 2 mm and asymptomatic , despite a more medial starting position . in the medial - lateral direction , the trajectory parallels as the angle between the tip of the t1 spinous process and the contralateral starting point . in the cranial - caudal direction the steep trajectory appears to be sufficient to compensate for starting higher on the pedicle as evidenced by no superior pedicle breaches in our cohort . utilization of bony landmarks as opposed to predetermined angles for screw trajectory equips this approach with an inherent mechanism to adjust for anatomic variability as compared to alternative approaches . the ctj is not easily imaged with fluoroscopy in the lateral position as surrounding bony structures obstruct direct view . moreover , determining entry point in ap view is challenging secondary to patient anatomy , skull clamp , surgical table , and positioning . hence , removing the need for imaging allows for less radiation exposure to the patient and surgical team while potentially decreasing the operative duration by eliminating fluoroscopy set - up time . moreover , the present method does not necessitate any additional bone removal or laminotomy windows . we also experienced less difficulty with rod contouring when connecting long cervicothoracic segments as the more medial screw head position at t1 is in line with lateral mass instrumentation . the novel free - hand method eliminates the need for expensive navigation equipment that is not readily available at most institutions . additionally , these systems may prolong surgical times and the price of utilizing an operating suite has been estimated at $ 93 per minute . the operational cost of intraoperative fluoroscopy can reach as much as $ 233.35 per case ( 2011 , us$ ) . there were also no clinical outcome measures recorded except that no patient returned to the operating room for screw reposition or experienced a new neurological deficit throughout the duration of the study . lastly , no cadaveric biomechanical investigations were performed with respect to t1 screw pull out strength utilizing this method . our modification of the classical starting point and trajectory maintains a high accuracy rate of successful screw placement in a safe , cost - effective fashion . it obviates the need for additional bone removal and imaging while maintaining a high rate of successful screw placement compared to historical free - hand methods . this technique allows for the potential expansion of the surgical armamentarium by encompassing more complex cervicothoracic procedures , especially at community medical centers with limited resources .
summary of background data : multilevel posterior cervical instrumented fusions are becoming more prevalent in current practice . 
 biomechanical characteristics of the cervicothoracic junction may necessitate extending the construct to upper thoracic segments . however , fixation in upper thoracic spine can be technically demanding owing to transitional anatomy while suboptimal placement facilitates vascular and neurologic complications . 
 thoracic instrumentation methods include free - hand , fluoroscopic guidance , and ct - based image guidance . 
 however , fluoroscopy of upper thoracic spine is challenging secondary to vertebral geometry and patient positioning , while image - guided systems present substantial financial commitment and are not readily available at most centers . 
 additionally , imaging modalities increase radiation exposure to the patient and surgeon while potentially lengthening surgical time.materials and methods : retrospective review of 44 consecutive patients undergoing a cervicothoracic fusion by a single surgeon using the novel free - hand t1 pedicle screw technique between june 2009 and november 2012 . 
 a starting point medial and cephalad to classic entry as well as new trajectory were utilized . 
 no imaging modalities were employed during screw insertion . 
 postoperative ct scans were obtained on day 1 . 
 screw accuracy was independently evaluated according to the heary classification.results:in total , 87 pedicle screws placed were at t1 . 
 grade 1 placement occurred in 72 ( 82.8% ) screws , grade 2 in 4 ( 4.6% ) screws and grade 3 in 9 ( 10.3% ) screws . 
 all grade 2 and 3 breaches were < 2 mm except one grade 3 screw breaching 2 - 4 mm laterally . 
 only two screws ( 2.3% ) were noted to be grade 4 , both breaching medially by less than 2 mm . 
 no new neurological deficits or returns to operating room took place postoperatively.conclusions:this modification of the traditional starting point and trajectory at t1 is safe and effective . 
 it attenuates additional bone removal or imaging modalities while maintaining a high rate of successful screw placement compared to historical controls .