Original ResearchAccuracy of pedicle screw placement in posterior lumbosacral instrumentation by computer tomography evaluation: A multi-centric retrospective clinical study

- L5 and S1 are not safe when inserting pedicle screws as expected.
- The incidences of high risk breach and inferomedial breach occur more in L5 and S1.
- The pedicles of L5 and S1 are special on their morphology.

BackgroundPedicle screw misplacement rates are relatively high with fluoroscopically guided techniques. However, breach rates in the 5th lumbar and the 1st sacral spines in conventional operations have not been specifically concerned because of their broad cross sections. It's a retrospective study to evaluate the accuracy and safety of pedicle screw placement in posterior lumbosacral instrumentation under CT scan with reconstruction.Materials and methods401 patients were evaluated under CT scan with reconstruction in 3 hospitals by 2 professional observers after posterior lumbosacral instrumentation including 152 3rd lumbar spines (L3), 219 4th lumbar spines (L4), 270 5th lumbar spines (L5) and 95 1st sacral spines (S1) with screws placed. Patients were followed for potential clinical symptoms.ResultsIn a total of 1467 instrumented pedicles, there were 371 pedicle breaches. Of these, the segment of the breached pedicles were L3: 91/301 (30.2%), L4: 126/436 (29.0%), L5: 132/539 (24.5%), S1: 22/191 (11.5%). For severe violation from L3 to S1, 8/91 (8.8%), 8/126 (6.3%), 19/132 (14.4%), 8/22 (36.4%) were confirmed respectively. Furthermore, the inferomedial breach sites quantified from L3 to S1 were 43/91 (47.3%), 74/126 (58.7%), 99/132 (75%), 19/22 (86.4%) respectively. And there were 9 cases of cerebrospinal fluid leakage and 3 cases of neurological deficit.ConclusionL3, L4 and L5 have no significant differences in pedicle breach rates. The incidences of high risk pedicle breach (grade III, grade IV) are higher in L5 and S1, and the breach sites are more common in the inferomedial wall of L5 and S1 than that of L3 and L4. Many surgeons took it for granted that L5 and S1 were safe when inserting pedicle screws, but they are not safe as expected actually.