The quantitative anatomy of the laminas of the spine.

Study Design: This study evaluated the dimensions of the laminas from C2 to L5 using adult spine specimens.

Objectives: To provide a set of quantitative data for the laminas from C2 to L5.

Summary Of Background Data: Anatomic evaluation of the pedicle and facet joint in the spine has been extensively reported. No detailed studies of the laminas from the cervical to the lumbar spines exist.

Methods: Thirty-seven spines from C2 to L5 were directly evaluated for this study. Anatomic evaluation of the laminas included the laminar height, width, thickness, and angulation.

Results: In general, the measurements were greater in male specimens than in female specimens, although significant differences (P < 0.05) between male and female specimens were noted in only three measurements. The greatest laminar height was at T11 (25.1 +/- 2.5 mm), and the least was at C4 (10.4 +/- 1.1 mm). The greatest laminar width was at L5 (15.7 +/- 2.0 mm), and the least was at T4 (5.8 +/- 0.8 mm). Laminar widths in the cervical region were slightly more than those in the thoracic region. The greatest laminar thickness was at T2 (5.0 +/- 0.2 mm), whereas the least was at C5 (1.9 +/- 0.6 mm). Laminar thickness tended to increase in the upper thoracic region and to decrease slightly in the lower thoracic region. The mean laminar thickness of the lower cervical region was least in the whole spine. The widest angle was at C3 (116.1 +/- 8.8 degrees) and T7 (112.3 +/- 8.0 degrees) and the narrowest was at C2 (99.1 +/- 8.0 degrees) and L3 (99.9 +/- 6.3 degrees). The slope angles of the laminas varied from 97.8 +/- 3.0 degrees at T9 to 129.0 +/- 7.5 degrees at L3.

Conclusions: Surgical placement of sublaminar instruments may benefit from this quantitative study through the use of the provided anatomic parameters of the laminas.