Usefulness of the nutrient foramen of lamina for insertion of thoracic pedicle screws.

STUDY DESIGN

A cadaveric study.

OBJECTIVE

To determine the utility of the nutrient foramen on the lamina in thoracic pedicle screw fixation.

SUMMARY OF BACKGROUND DATA

Recent studies have examined the portal of entry for pedicle screws. Unfortunately, there is no distinct anatomic marker, and the portal of entry usually depends on the surgeon's preference.

METHODS

This study investigated the nutrient artery foramen on the lamina from fourth to eighth thoracic vertebrae after partial laminectomy of 7 cadaveric spines. A 2-mm Steinmann pin was inserted as follows: vertical insertion on the right nutrient foramens and a 10-degree caudal on the left nutrient foramens. Radiographs and computed tomography were obtained and the relationship between the Steinmann pin and pedicle were analyzed.

RESULTS

There were 44 nutrient artery foramens (63%, 44/70). Among them, 31 foramens (70%, 31/44) were on the right. On the lateral radiographs, the right pins were inserted parallel within the upper end plate and the left pins were inserted within the vertebral body in T4 and T5. For T6 to T8, the right pins were inserted below the upper end plate and the left pins were inserted below the center of the vertebral body. On the computed tomography axial scan, 17 degrees of medialization for T4 to T7 and 5 degrees for T8 was possible when the size of pedicle screw for human is considered.

CONCLUSIONS

The nutrient artery foramen on the lamina of thoracic vertebrae is useful for inserting the thoracic pedicle screw.