Anatomy and Ultrasound-Guided Injection of the Medial Branch of the Dorsal Ramus of the Cervical Spinal Nerves in the Horse: A Cadaveric Study

Objective The aim of this study was to describe the anatomy of the nerves supplying the cervical articular process joint and to identify relevant anatomical landmarks that could aid in the ultrasound-guided location and injection of these nerves for diagnostic and therapeutic purposes. Study Design Twelve cadaveric equine necks were used. Five necks were dissected to study the anatomy of the medial branch of the dorsal ramus of the cervical spinal nerves 3 to 7. Relevant anatomical findings detected during dissections were combined with ultrasonographic images obtained in one other neck. Six additional necks were used to assess the accuracy of ultrasound-guided injections of the medial branch with blue dye. Results Each examined cervical articular process joint, except for C2 to C3, presented a dual nerve supply. The articular process joints were found to be in close anatomical relationship with the medial branch of the dorsal ramus of the cervical spinal nerve exiting from the intervertebral foramen at the same level, and with the medial branch of the dorsal ramus of the cervical spinal nerve exiting from the intervertebral foramen one level cranial to the articular process joint of interest. A total of 55 nerves were injected under ultrasonographic guidance, 51 of which were successfully stained. Conclusion The current study provided new detailed information regarding the innervation of the cervical articular process joint. The medial branches of the dorsal rami of the cervical spinal nerves were injected with an accuracy that would be of clinical value. Our study offers the foundations to develop new diagnostic and therapeutic techniques for pain management in cervical articular process joint arthropathy in horses.

A new anatomic zone division within the human cervical spinal canal

Background: Anatomic details are important for identifying the origin and anatomic basis of symptoms in patients with cervical spondylosis. However, very little quantitative data has been reported. In an effort to provide an anatomic basis for the examination of cervical spondylosis mechanisms, we characterized the morphologic features of cervical spinal nerve rootlets and defined different zones of the human cervical spinal canal.Methods: In 10 cadaveric cervical cords from C2 to T1, we defined three zones bilaterally from the midline (zones I-III) and two zones from cranial to caudal (zones P and IP) on the coronal plane within the cervical spinal canal. We measured each anatomic zone, including 1) horizontal widths of zones I, II and III; 2) the length of the cervical spinal segment at the ventral rootlets (LV); 3) the pedicle height (zone P) and interpedicle height (zone IP); and 4) the distance between the superior margin of the pedicle and the exit of the uppermost ventral nerve rootlet (PN). Results: The horizontal widths of zone I tended to decrease gradually from C4 to C8 (p=0.98). The width of zone II at C4 was significantly less than that at other levels (p=0.008). The width of zone III increased from C4 to C8 and was significantly greater at C7 and C8 than at C4, C5, and C6 (p=0.032). Pedical and interpedical heights were not significantly different at different levels (p=0.365 and 0.240, respectively). LV values at C4 and C8 were smaller than those at C5, C6, and C7 (p=0.001). At C4, the uppermost ventral rootlet was at approximately the same height as the C3 pedicle, whereas at C8, the uppermost ventral rootlet was at the same level as the inferior part of the C6 pedicle. Ventral intradural intersegmental connections were found in three of 20 (15%) intersegments (two specimens).Conclusions: These anatomic zones may be useful for diagnosing cervical spondylosis and guiding anterior decompression surgery.