and Uwe Spetzger1
Department of Neurosurgery, Klinikum Karlsruhe, Karlsruhe, Baden-Württemberg, Germany
The anterior standard approach is the most frequently used surgical approach to the cervical spine. It is suitable for discectomy as well as for corpectomy with anterior plating. The posterior approach allows laminectomy and fusion as well as open-door laminoplasty. When performing the anterior approach, it is possible to use anatomical landmarks (hyoid bone, thyroid cartilage, tuberculum caroticum) already when starting with the skin incision. During the posterior approach, it is only possible to identify the midline with the help of the spinous processes. The spinous processes of C2 and C7 are usually longer than the spinous processes of C3 to C6; thus, they can be used as anatomical landmarks.
8.1 Anterior Approach, Discectomy, Cage Implantation and Total Disc Replacement
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8.1.1 Anterior Approach to the Cervical Spine and Discectomy
The operation is performed in supine position with the head in a slightly extended position. By adjusting the operating table, the patient’s head should be placed higher than the heart to avoid venous congestion and thus increased venous bleeding in the spinal canal during surgery. A fluoroscope is integrated in the operative setup and covered with sterile drapes.
The skin incision starts in the midline and is about 4 cm long (Fig. 8.1). It should be placed in a skinfold to achieve an optimum cosmetic result after surgery. When performing multilevel surgery (three or more levels), most surgeons prefer a longitudinal incision over the anterior edge of the sternocleidomastoid muscle. In case of good anatomical conditions, it is possible to use the transverse standard incision for three-level surgery as well.
Skin incision for an anterior approach to C4/5
It is possible to identify certain cervical levels by anatomical landmarks before the skin incision:
C2/3: mandibular angle
C3/4: hyoid bone
C4/5: upper edge of the thyroid cartilage
C5/6: lower edge of the thyroid cartilage
C6/7: middle between lower edge of the thyroid cartilage and sternum
After dissection and incision of the platysma, the superficial fascia is dissected and incised medially to the sternocleidomastoid muscle (Figs. 8.2, 8.3 and 8.4). Afterwards the common carotid artery is identified by using blunt dissection of the straight cervical muscles (Figs. 8.5 and 8.6). Then the neurovascular bundle of the neck (common carotid artery, internal jugular vein, vagus nerve) is lateralised. Finally, the hypopharynx (above C5) or the trachea and oesophagus, respectively, are medialised (Fig. 8.7). After the visualisation of the anterior aspect of the cervical spine, the prevertebral fascia is incised and dissected. For identification of the level C5/6, palpation of the tuberculum caroticum is helpful (Fig. 2.2).
Incision of the platysma
Exposure of the superficial fascia
Incision of the superficial fascia
Medialising of the straight cervical muscles
Exposure of the common carotid artery
Medialising of the hypopharynx
Exposure of the ventral surface of the cervical spine
The surgical field is exhibited by self-holding soft tissue retractors (Fig. 8.9). Afterwards the identification of the right level is verified using a fluoroscope. Then, Caspar pins (Caspar et al. 1989) are screwed into the vertebral bodies of the affected level (Fig. 8.10 and 8.11). This step is also checked with the fluoroscope. Afterwards the distractor is put on the pins and fixed. A slight distraction is applied until the anterior longitudinal ligament is tensed (Fig. 8.12).
Self-holding soft tissue retractor
Screwing in a Caspar pin into the superior vertebral body
Screwing in a Caspar pin into the inferior vertebral body
Introducing of the Caspar distractor. Small image: fluoroscopic image of the Caspar pins, lateral view
Under microscopic view, the anterior longitudinal ligament is incised and resected (Fig. 8.13). Now, loose disc material can be removed with a forceps (Fig. 8.14). The discectomy is completed with a sharp spoon. During this process, remnants of the disc as well as the hyaline cartilage are removed from the endplates without perforating the bony endplates of the adjacent vertebrae (Fig. 8.15).
Incision of the anterior longitudinal ligament at the height of the intervertebral disc
Start of the discectomy with a forceps
Completion of the discectomy with a sharp spoon
The resection of posterior osteophytes and the microsurgical decompression of the spinal cord can be achieved by using either a Kerrison punch or a high-speed drill (Fig. 8.16). When using a fluted ball tool with the drilling system, the resection of osteophytes can be done fast, but there is a higher risk for injuring the dural or even the spinal cord. Therefore, this option should be chosen by very experienced surgeons only. Using a diamond drill is an alternative with a lower risk of dural injury, but the higher temperature during the drilling procedure has to be taken into account. When using a diamond drill, it is crucial to use enough irrigation and to interrupt drilling from time to time to avoid thermal damage of neural structures. The resection of osteophytes by drilling increases the likelihood of heterotope ossification and consecutive bony bridging of the treated level. This fact has to be taken into account when implanting a prosthesis.
Resection of posterior osteophytes with a diamond drill
Afterwards the posterior longitudinal ligament is perforated with a filigree nerve hook and resected with a 2-mm Kerrison punch (Fig. 8.17). By doing so the spinal canal is decompressed step by step since it is possible to resect thickened ligaments and bone behind vertebral bodies and in the neuroforamina (Fig. 8.18). The decompression is checked under fluoroscopy with a nerve hook (Fig. 8.19). When using the Kerrison punch for resection of posterior osteophytes, it is crucial to bear in mind that this leads to an additional space occupation by the instrument with consecutive worsening of a pre-existing myelopathy. Compared to drilling, the use of the Kerrison punch is a bit more time-consuming, and it has the potential disadvantage of venous bleedings from cancellous bone that can be stopped by the heat resulting from using a diamond drill.
Resection of the posterior longitudinal ligament with a Kerrison punch
Decompression of the right neuroforamen with a Kerrison punch
Checking the decompression with a nerve hook. Small image: lateral fluoroscopy after application of contrast agent into the intervertebral disc space
After the resection of the posterior longitudinal ligament and posterior osteophytes, the distraction of the vertebral bodies is slightly increased, and the trial head of the cage or prosthesis is inserted to determine the size of the definite implant (Fig. 8.20). Finally, the implant is inserted and the distraction is taken away (Fig. 8.21). Before that, the effect of the decompression and the right depth of the implant can be assessed by application of a contrast agent into the intervertebral disc space and the epidural space, respectively (Fig. 8.22). Afterwards, the wound is closed layer by layer.
Insertion of the trial head to determine the size of the final implant
Implantation of a dynamic cervical implant DCI™. Small image: lateral fluoroscopic view of the implant
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