these techniques have helped surgeons adequately manage complex trauma , tumor , and degenerative pathologies .
hadra in 1890 described the use of wiring and graft techniques to perform the first spinal fusion procedures .
these techniques were standard until the start of modern cervical spinal fusion with roy - camille in the 1970s .
since this time there have been improvements in technique and implants , which have made the procedures safer , thus leading to increased adoption of instrumented cervical fusion . within the united states ,
approximately 150  000 cervical fusion procedures are performed each year . around 90% of cervical fusions
the use of plate and screw instrumentation for anterior cervical fusion has become a mainstay , so much so that in 2010 the american medical association combined 2 current procedural terminology codes into a comprehensive code .
the indications for cervical fusion are well established , based on an abundance of studies showing clinical and biomechanical efficacy . despite these studies there is a paucity of literature detailing the complications associated with cervical spinal fusion .
most studies are retrospective in design , contain a small numbers of patients , report single - institution data , relate to a single indication , or contain information with outdated procedures .
the overall complication rate for cervical fusion procedures is low , and these earlier studies may not reliably provide data on less common complications . while rare , screw backout or misplaced screws can lead to morbidity , the need for revision surgery , and increased costs .
we have conducted a retrospective multicenter case series study involving 21 high - volume surgical centers from the aospine north america clinical research network , selected for their excellence in spine care and clinical research infrastructure and experience .
medical records for 17  625 patients who underwent cervical spine surgery ( levels from c2 to c7 ) between january 1 , 2005 , and december 31 , 2011 , inclusive , were reviewed to identify occurrence of 21 predefined treatment complications .
the complications included reintubation requiring evacuation , esophageal perforation , epidural hematoma , c5 palsy , recurrent laryngeal nerve palsy , superior laryngeal nerve palsy , hypoglossal or glossopharyngeal nerve palsy , dural tear , brachial plexopathy , blindness , graft extrusion , misplaced screws requiring reoperation , anterior cervical infection , carotid artery injury or cerebrovascular accident , vertebral artery injuries , horner s syndrome , thoracic duct injury , tetraplegia , intraoperative death , revision of arthroplasty and , pseudomeningocele . trained research staff at each site abstracted the data from medical records , surgical charts , radiology imaging , narratives , and other source documents for the patients who experienced one or more of the complications from the list .
copies of case report forms were transferred to the aospine north america clinical research network methodological core for processing , cleaning , and data entry .
test was used to analyze changes in clinical outcomes at follow - up compared to preoperative status . a total of 12  903 cervical procedures qualified for screening for the complication of misplaced screw requiring reoperation .
there were 11 instances of misplaced screws requiring reoperation , for an incidence of 0.085% , translating to a rate of 8.5 per 10  000 cervical spine surgeries ( table 1 ) .
a total of 8887 cases screened were specifically only anterior procedures making the incidence 3/8887 ( 0.034% ) .
we do not have enough information on the remaining cases to make a determination of the incidence of misplacement of posterior screws requiring reoperation , but suspect it would a higher rate .
the average age of the patients was 53 years , and there were 4 female patients .
myelopathy and radiculopathy were the most common reasons for initial operation , 6/11 ( 55% ) and 5/11 ( 45% ) , respectively , with 1 patient having both symptoms .
importantly , there were no changes in the health - related quality - of - life metrics due to this complication .
there were no new neurologic deficits ; patients most often presented with pain , and screw backout was diagnosed on postoperative plain x - ray or computed tomography scan .
five of 11 ( 45% ) and 3/11 ( 27% ) patients were diagnosed within the original hospital admission or postoperative clinic follow - up , respectively , while we were unable to obtain these data on 3 cases .
the most common location for screw backout was c6 , 4/11 ( 36% ) ; 2 patients had screw backout at c2 .
patient 4 had aggressive removal of an osteophyte complex and an anterior cervical screw penetrated into the central canal ( figure 1a and b ) .
the patient had symptoms of right - sided proximal upper extremity weakness , which resolved with removal and revision of the c5 penetrating screw ( figure 1c ) .
( c ) postoperative lateral cervical spine x - ray demonstrating removal of misplaced c5 screw .
due to the risk and complexity associated with cervical spinal surgery , current techniques and approaches did not become popular until the mid-20th century .
advances in imaging , operative microscopes , and instrumentation have allowed cervical spinal surgery to progress to the current state . since 1891
when the first cervical fusion procedure was performed there have been sequential advances described by many authors to develop the early fixation techniques .
several biomechanical animal and cadaver studies have been performed during the rapid advancement in cervical spinal instrumentation over the past 30 years .
posterior instrumented fusion studies have consistently proven the stiffness of the constructs to be equal to or greater than that of an intact spine .
the most common failure in these studies was screw pullout at a predictable amount of force .
anterior plating studies have strongly guided the development of each type of system and have shown continued improvement in the efficacy of constructs .
the advancements and improvements in cervical spinal instrumentation would be expected to decrease the rate of hardware - related complications .
the overall complication rate of cervical spinal surgery is estimated to be 0.2% to 17.8% .
after 30 days , the most common complication is related to instrumentation dislodgement , breakage , or both , and occurs in 2% to 25% of cases of spinal fusion procedures .
reoperation rate for instrumented spinal fusions is reported between 2% and 25% , with the majority related to pseudoarthrosis .
the majority of information is based on case reports , retrospective reviews , and small series of patients .
there are few recent articles addressing the rate of screw backout or misplacement requiring reoperation , and many older studies include the use of unrestricted devices that permitted screw backout .
fehlings et al prospectively collected 302 cervical spondylotic myelopathy patients and found a perioperative complication rate of 15.6% , with 11.6% minor and 7.0% major perioperative risk .
three patients had instrumentation malposition / migration for a rate of 1% in the perioperative period .
three patients had instrumentation / graft migration or instrumentation failure , making the risk of delayed hardware complications 1.1% .
of 195 anterior cervical plating procedures , 5 ( 2.6% ) required reoperation for hardware failure .
al used the marketscan database and identified 13  662 patients who underwent anterior or posterior cervical fusion for degenerative disc disease .
the rate of any complication excluding dysphagia was 12.3% and 17.8% for anterior and posterior approaches , respectively .
there is , however , no specific mention of the reason for reoperation in the study . in 2011 , katonis et al reported on 1662 consecutively placed lateral mass screws .
screw pullout occurred in 3 ( 1.3% ) patients , but they did not mention if these patients required reoperation or if the system was a screw - plate or polyaxial screw - rod implant system .
the report also mentioned 11 ( 0.6% ) screws had a suboptimal trajectory but no patient required reoperation for removal or replacement of hardware .
al barbarawi et al had 2 screw pullout cases out of 430 lateral mass screw - rod fixation cases . two ( 4.0% ) cases were found to have screw pullout in the study by kim et al using yoon s method .
kasimatis et al included 74 patients from 1990 to 2005 who underwent anterior cervical treatment of cervical spine trauma in their study looking at complications .
screw backout was reported in 4 ( 5.4% ) cases , all of which were unrestricted backout plates .
seven cases ( 9.5% ) had  less - than - ideal  positioning of the construct with only one case requiring reoperation because of a malpositioned screw being completely in the intervertebral space .
veeravagu et al looked at the marketscan database from 2006 and 2010 and found in 28  777 patients a reoperation rate of 9.13% and 10.7% for single - level and multilevel anterior cervical fusion , respectively .
unfortunately , their data did not include data about the rate of reoperation related specifically to hardware failure .
shapiro et al found no screw pullout when using locking screw fixation in 246 consecutive anterior cervical fusion cases .
several reports exist in the literature of screw pullout resulting in dysphagia and sometimes erosion into the gastrointestinal tract .
they continue to document the incidence of screw pullout related to misplacement to be uncommon , but can result in complications with serious morbidity and increased costs .
coe et al performed a systematic review of lateral mass screw fixation , and implant removal was defined as a surgical procedure to correct malpositioned screws , screw breakout , or loosening .
reoperation as defined was necessary for 27 ( 1.2% ) of 2185 screws placed in 294 patients across 5 studies .
limited information was available to determine the number of patients with screw misplacement that did not require reoperation .
there was also insufficient information within the screening population to determine the number of screws placed for comparison .
the screening population was divided into anterior only and posterior or anterior / posterior combined groups .
this does not allow for calculation of the incidence of posterior misplacement requiring revision , and it can only be speculated that this number would be much higher than the rate for anterior alone procedures .
the advancements and improvements in cervical spinal instrumentation would be expected to decrease the rate of hardware - related complications .
the overall complication rate of cervical spinal surgery is estimated to be 0.2% to 17.8% .
after 30 days , the most common complication is related to instrumentation dislodgement , breakage , or both , and occurs in 2% to 25% of cases of spinal fusion procedures .
reoperation rate for instrumented spinal fusions is reported between 2% and 25% , with the majority related to pseudoarthrosis .
the majority of information is based on case reports , retrospective reviews , and small series of patients .
there are few recent articles addressing the rate of screw backout or misplacement requiring reoperation , and many older studies include the use of unrestricted devices that permitted screw backout .
fehlings et al prospectively collected 302 cervical spondylotic myelopathy patients and found a perioperative complication rate of 15.6% , with 11.6% minor and 7.0% major perioperative risk .
three patients had instrumentation malposition / migration for a rate of 1% in the perioperative period .
three patients had instrumentation / graft migration or instrumentation failure , making the risk of delayed hardware complications 1.1% .
of 195 anterior cervical plating procedures , 5 ( 2.6% ) required reoperation for hardware failure .
cole et al used the marketscan database and identified 13  662 patients who underwent anterior or posterior cervical fusion for degenerative disc disease .
the rate of any complication excluding dysphagia was 12.3% and 17.8% for anterior and posterior approaches , respectively .
there is , however , no specific mention of the reason for reoperation in the study . in 2011 , katonis et al reported on 1662 consecutively placed lateral mass screws .
screw pullout occurred in 3 ( 1.3% ) patients , but they did not mention if these patients required reoperation or if the system was a screw - plate or polyaxial screw - rod implant system .
the report also mentioned 11 ( 0.6% ) screws had a suboptimal trajectory but no patient required reoperation for removal or replacement of hardware .
al barbarawi et al had 2 screw pullout cases out of 430 lateral mass screw - rod fixation cases . two ( 4.0% ) cases were found to have screw pullout in the study by kim et al using yoon s method .
kasimatis et al included 74 patients from 1990 to 2005 who underwent anterior cervical treatment of cervical spine trauma in their study looking at complications .
screw backout was reported in 4 ( 5.4% ) cases , all of which were unrestricted backout plates .
seven cases ( 9.5% ) had  less - than - ideal  positioning of the construct with only one case requiring reoperation because of a malpositioned screw being completely in the intervertebral space .
veeravagu et al looked at the marketscan database from 2006 and 2010 and found in 28  777 patients a reoperation rate of 9.13% and 10.7% for single - level and multilevel anterior cervical fusion , respectively .
unfortunately , their data did not include data about the rate of reoperation related specifically to hardware failure .
shapiro et al found no screw pullout when using locking screw fixation in 246 consecutive anterior cervical fusion cases .
several reports exist in the literature of screw pullout resulting in dysphagia and sometimes erosion into the gastrointestinal tract .
they continue to document the incidence of screw pullout related to misplacement to be uncommon , but can result in complications with serious morbidity and increased costs .
coe et al performed a systematic review of lateral mass screw fixation , and implant removal was defined as a surgical procedure to correct malpositioned screws , screw breakout , or loosening .
reoperation as defined was necessary for 27 ( 1.2% ) of 2185 screws placed in 294 patients across 5 studies .
limited information was available to determine the number of patients with screw misplacement that did not require reoperation .
there was also insufficient information within the screening population to determine the number of screws placed for comparison .
the screening population was divided into anterior only and posterior or anterior / posterior combined groups .
this does not allow for calculation of the incidence of posterior misplacement requiring revision , and it can only be speculated that this number would be much higher than the rate for anterior alone procedures .
this study represents the largest series to analyze and tabulate the incidence of screw backout or misplacement requiring reoperation following cervical spine surgery .
the data suggest this is a very rare adverse event , despite the widespread use of cervical fixation . due to the methodology of this study
, there is a potential for underestimation of screw misplacement requiring reoperation within this series of patients .
this potential for underreporting is more likely to occur in the case of posterior cervical fusion as this could not be calculated based on this study .
the data therefore represents a lower limit for the incidence of screw misplacement requiring reoperation .
patients suffering this complication require hardware revision , but do not usually suffer neurologic sequelae .
meticulous technique and thorough knowledge of the relevant anatomy are the best means of preventing this complication .
 study design : a multicenter , retrospective case series.objective:in the past several years , screw fixation of the cervical spine has become commonplace . for the most part , 
 this is a safe , low - risk procedure . while rare , screw backout or misplaced screws can lead to morbidity and increased costs . 
 we report our experiences with this uncommon complication.methods:a multicenter , retrospective case series was undertaken at 23 institutions in the united states . 
 patients were included who underwent cervical spine surgery from january 1 , 2005 , to december 31 , 2011 , and had misplacement of screws requiring reoperation . 
 institutional review board approval was obtained at all participating institutions , and detailed records were sent to a central data center.results:a total of 12  903 patients met the inclusion criteria and were analyzed . 
 there were 11 instances of screw backout requiring reoperation , for an incidence of 0.085% . 
 there were 7 posterior procedures . 
 importantly , there were no changes in the health - related quality - of - life metrics due to this complication . 
 there were no new neurologic deficits ; a patient most often presented with pain , and misplacement was diagnosed on plain x - ray or computed tomography scan . 
 the most common location for screw backout was c6 ( 36%).conclusions : this study represents the largest series to tabulate the incidence of misplacement of screws following cervical spine surgery , which led to revision procedures . 
 the data suggest this is a rare event , despite the widespread use of cervical fixation . 
 patients suffering this complication can require revision , but do not usually suffer neurologic sequelae . 
 these patients have increased cost of care . 
 meticulous technique and thorough knowledge of the relevant anatomy are the best means of preventing this complication . 
Introduction
Methods
Results
Discussion
Incidence of Complications
Conclusions