Intradural Neuroanatomy in the Cervical Spinal Canal: Importance of a New Anatomic Zone Division and Accurate Assessment of Neural Compression in Myeloradiculopathy Patients.

A dissection-based study of 10 embalmed human cadavers. To provide an anatomic basis to examine the underlying mechanisms of cervical spondylosis. Detailed anatomical quantitative data of cervical spine is limited in current literature. Ten cervical spines from C2 to T1 were obtained. We defined three zones from midline to lateral part (zone I, II, and III) and two zones from cranial to caudal (zone P and zone IP) on the coronal plane within the cervical spinal canal. Quantitative anatomy of the zones at different cervical segments were measured including: (1) horizontal widths of zone I, II, and III; (2) length of the cervical spinal cord segment at the ventral rootlets (LV); (3) the pedicle height (PH, zone P) and the inter-pedicle height (IPH, zone IP); (4) the distance between the superior margin of pedicle and the exit of the uppermost ventral nerve rootlet (PN). The value of zone II at C4 was significantly less than that at other levels. The value of zone III increases from C4 to C8, and the values at C7 and C8 were significantly higher than those at C4, C5, and C6. PHs and IPHs were not significantly different between different levels. The values of LV at C4 and C8 were smaller than those of C5, C6, and C7. The value of PN showed an increasing trend. At C4, the uppermost ventral rootlet was at about the same height as C3 pedicle, while C8 uppermost ventral rootlet was at the same level as the inferior part of C6 pedicle. Ventral intradural intersegmental connections were found in three intersegments out of 20 intersegments. The current definition of anatomic zones may be useful for an accurate diagnosis of cervical spondylosis and a safe and effective anterior decompression surgery. Level of Evidence: N/A.