Retrospective study on the CT evaluation of accuracy of pedicle screw placement in posterior lumbosacral instrumentation

Abstract

Objectives To evaluate the accuracy of posterior pedicle screw placement in a multicentric retrospective clinical study and analyze the potential reasons of pedicle breaches. Methods From January 2014 to December 2014, 293 patients with conventional posterior pedicle screw instrumentation up to inclusion and exclusion criteria were recruited from 3 different hospitals. The operative levels included L4 in 219 cases, L5 in 270 cases and 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 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 280 pedicle breaches in a total of 1166 instrumented pedicles of 293 patients. The breach rates in different levels were listed as 29.0% (126/436) in L4, 24.5% (132/539) in L5 and 11.5% (22/191) in S1. There were no significant differences in pedicle breach rates between L4 and L5, while the breach rates in L4 and L5 were both significantly higher than those in S1. For severe violation from L4 to S1, 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 S1 were significantly higher than those of L4. Furthermore, the inferomedial breach rates quantified from L4 to S1 were 58.7% (74/126), 75% (99/132), 86.4% (19/22) respectively. The breach rates in the inferomedial wall of the L5, S1 pedicles were statistically higher than those of L4. Pedicle breach rates among 3 hospitals 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 2 cases of transient nerve root injuries. Conclusion There are no significant differences in pedicle breach rates between L4 and L5. However, pedicle breach rates in L4 and L5 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 L4. In addition, the incidences of pedicle breaches and related complications occurred more in lower-level hospitals. Key words: 【Key word】Lumbar vertebrae; Sacrum; Spinal fusion; Bone Screws