Retrospective Study On The CT Evaluation Of Accuracy Of Pedicle Screw Placement In Posterior Lumbosacral Instrumentation

Objectives:It’s a multi-centric retrospective clinical study to evaluate the accuracy of posterior pedicle screw placement under CT scan with reconstruction in lumbosacral segments and analyze the potential reasons.Methods:From January 2014 to December 2014,401 patients with conventional posterior pedicle screw instrumentation up to inclusion and exclusion criteria were recruited from 3 different hospitals.The operative levels included the 3rd lumbar spines(L3)in 152 cases,the 4th lumbar spines(L4)in 219 cases,the 5th lumbar spines(L5)in 270 cases and the 1st sacral spines(S1)in 95 cases.The screw positions in the pedicles were verified by 2 professional observers independently under computed tomography reconstruction within 24 hours to 48 hours postoperatively.The locations and grades of breached pedicles were recorded in each segment and related factors were analyzed.Pedicle breach rates in 3 hospitals and different pathologies were stratified and analyzed as well.All patients were followed up and neurological deficits as well as other postoperative complications were registered.Results:There were 371 pedicle breaches in a total of 1467 instrumented pedicles of 401 patients.The breach rates in different levels were listed as:30.2%(91/301)in L3,29.0%(126/436)in L4,24.5%(132/539)in L5 and 11.5%(221/191)in S1.There were no significant differences in pedicle breach rates between L3,L4 and L5,while the breach rates in L3,L4 and L5 were all significantly higher than those in S1.For severe violation from L3 to S1,8.80%(8/91),6.3%(8/126),14.4%(19/132)and 36.4%(8/22)were confirmed respectively.The incidences of high risk pedicle breach(grade Ⅲ&grade Ⅳ)of L5 and Si were significantly higher than those of L3 and L4.Furthermore,the inferomedial breach rates quantified from L3 to S1 were 47.3%(43/91),58.7%(74/126),75%(99/132)and 86.4%(19/22)respectively.The breach rates in the inferomedial wall of the L5,Si pedicles were statistically higher than those of L3 and L4.Pedicle breach rates among 3 hospitals and different pathologies varied while the characteristics of the locations,the grades and the segments of breached pedicles were similar to overall results in each hospital.There were 9 cases of cerebrospinal fluid leakage and 3 cases of transient nerve root injuries.Conclusion:There are no significant differences in pedicle breach rates between L3,L4 and L5.However,pedicle breach rates in L3,L4 and L4 are statistically higher than those in S1.The incidence of high risk pedicle breach and inferomedial wall breach of L5 and S1 are significantly higher than that of L3,L4.In addition,the incidences of pedicle breaches and related complications occurred more in lower-level hospitals and degenerative disease.Although pedicle breach errors may occur,resulting in rare but severe complications,they should be taken into consideration seriously,as well.