Micro-computed tomography analysis of the lumbar pedicle wall

Background Although the pedicle is routinely used as a surgical fixation site, the pedicle wall bone area fraction (bone area per unit area) and its distribution at the isthmus of the pedicle remain unknown. The bone area fraction at the pedicle isthmus is an important factor contributing to the strength of pedicle screw constructs. This study investigates the lumbar pedicle wall microstructure based on micro-computed tomography. Methods Six fresh-frozen cadaveric lumbar spines were analyzed. Left and right pedicles of each vertebra from L1 to L5 were resected for micro-computed tomography scanning. Data was analyzed with custom-written software to determine regional variation in pedicle wall bone area fraction. The pedicular cross-section was divided into four regions: lateral, medial, cranial, and caudal. The mean bone area fraction values for each region were calculated for all lumbar spine levels. Results The lateral region showed lower bone area fraction than the medial region at all spinal levels. Bone area fraction in the medial region was the highest at all levels except for L4, and the median values were 99.8% (95.9–100%). There were significant differences between the lateral region and the caudal region at L1, L2 and L3, but none at L4 and L5. The bone area fraction in the lateral region was less than 64% at all spinal levels and that in the caudal region was less than 67% at the L4 and L5 levels. Conclusions This study provides initial detailed data on the lumbar pedicle wall microstructure based on micro-computed tomography. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral and caudal walls.

Download Full-text

Confirmation of accuracy/inaccuracy of lumbar pedicle screw placement using postoperative computed tomography

Surgical Neurology International ◽

10.25259/sni_290_2021 ◽

2021 ◽

Vol 12 ◽

pp. 518

Author(s):

Mohamed M. Arnaout ◽

Magdy O. ElSheikh ◽

Mansour A. Makia

Keyword(s):

Computed Tomography ◽

Lumbar Spine ◽

Pedicle Screw ◽

Pedicle Screws ◽

Operative Intervention ◽

Screw Placement ◽

Lumbar Spine Surgery ◽

Pedicle Screw Placement ◽

Lumbar Pedicle ◽

Ct Studies

Background: Transpedicular screws are extensively utilized in lumbar spine surgery. The placement of these screws is typically guided by anatomical landmarks and intraoperative fluoroscopy. Here, we utilized 2-week postoperative computed tomography (CT) studies to confirm the accuracy/inaccuracy of lumbar pedicle screw placement in 145 patients and correlated these findings with clinical outcomes. Methods: Over 6 months, we prospectively evaluated the location of 612 pedicle screws placed in 145 patients undergoing instrumented lumbar fusions addressing diverse pathology with instability. Routine anteroposterior and lateral plain radiographs were obtained 48 h after the surgery, while CT scans were obtained at 2 postoperative weeks (i.e., ideally these should have been performed intraoperatively or within 24–48 h of surgery). Results: Of the 612 screws, minor misplacement of screws (≤2 mm) was seen in 104 patients, moderate misplacement in 34 patients (2–4 mm), and severe misplacement in 7 patients (>4 mm). Notably, all the latter 7 (4.8% of the 145) patients required repeated operative intervention. Conclusion: Transpedicular screw insertion in the lumbar spine carries the risks of pedicle medial/lateral violation that is best confirmed on CT rather than X-rays/fluoroscopy alone. Here, we additional found 7 patients (4.8%) who with severe medial/lateral pedicle breach who warranting repeated operative intervention. In the future, CT studies should be performed intraoperatively or within 24–48 h of surgery to confirm the location of pedicle screws and rule in our out medial or lateral pedicle breaches.

Download Full-text