Surgical Incisions, Positioning, and Retraction

Chapter 169 Surgical Incisions, Positioning, and Retraction



A variety of ventral and dorsal incisions are used to gain access from the upper cervical to the lower sacral spine. Appropriate positioning plays an important role in minimizing blood loss and providing adequate exposure of the spine. Tissue retraction plays an equally important role. Table 169-1 presents an overview of approaches and corresponding incisions. This chapter focuses on surgical decisions, patient positioning, and retraction techniques to avoid complications during surgery.


TABLE 169-1 Classification of Surgical Approaches and Commonly Used Incision Types







































































































































































Region Exposure Incision
High Cervical Spine
Dorsal approaches Suboccipital craniectomy C1–2 laminectomy Dorsal midline
  Lateral transcondylar approach Hockey-stick, retromastoid
Ventral approaches Transoral approach Midline pharynx
  Median labiomandibular glossotomy Median lower lip, mandible, tongue
  Transthyroidal approach Transverse below hyoid bone
  Ventrolateral retropharyngeal approach T-shaped submandibular or hockey-stick
Lateral approaches SCM may be cut L-shaped incision below mastoid process
Subaxial Cervical Spine (C3-T1)
Dorsal approaches Laminoforaminotomy for cervical disc disease Dorsal paramedian
  Laminectomy Dorsal midline
  Laminoplasty Dorsal midline
Ventral approaches Ventromedial approach Parallel to skin crests or SCM
  Ventrolateral approach–medial to the carotid artery Parallel to SCM
  Ventrolateral approach–lateral to the carotid artery Parallel to SCM
Cervicothoracic Junction (C7-T3)
Dorsal approaches Laminectomy Dorsal midline
Ventral approaches Lower ventral-medial cervical approach Parallel to SCM
  Transsternal approach T-shaped; extending midsternum
  Transmanubrial approach T-shaped; or parallel to SCM extending midsternum
  Transverse supraclavicular approach Parallel to clavicle
  Transaxillary extrapleural approach Subaxillary, parallel to T3 rib
  Transpleural-transthoracic approach Parallel to T3 rib
Thoracic and Thoracolumbar Spine
Dorsal approaches Thoracic laminectomy Dorsal midline
  Transpedicular approach Dorsal midline
  Costotransversectomy Curved to one side paramedian
  Lateral extracavitary approach Curved to one side paramedian or hockey-stick
  Dorsal en bloc total spondylectomy Dorsal midline
Ventral approaches Transpleural thoracotomy Parallel to rib
  Transdiaphragmatic approach Flank incision
  Ventrolateral retroperitoneal approach Flank incision
Lumbar and Lumbosacral Spine
Dorsal approaches Lumbar laminectomy Dorsal midline
  Paraspinal approach Paramedian
  Lateral extracavitary approach Paramedian
Ventral approaches Extreme lateral interbody fusion approach or ventrolateral transpsoatic approach Lateral lumbar
  Pelvic brim extraperitoneal approach Lower flank incision
  Transperitoneal approach Midline/horizontal subumbilical laparotomy incision
Sacrum
Dorsal approaches Dorsal approach Dorsal midline
Ventral approaches Retroperitoneal approach U-shaped suprapubic incision
  Transperitoneal approach Midline subumbilical laparotomy incision

SCM, sternocleidomastoid muscle.



Patient Positioning


Appropriate patient positioning in the operating room is optimally determined by the combined efforts of the surgeon and the neuroanesthetist.



Sitting Position


An advantage of the sitting position is that it directs blood away from the surgical site (Fig. 169-1). The risk of air embolism, however, is a major disadvantage. Furthermore, if the patient is quadriplegic (with a decrease in sympathetic tone), the resulting hemodynamic changes and hypoperfusion associated with the sitting position may compromise the perfusion of the spinal cord. Therefore, the sitting position requires a competent anesthetist as well as right atrial and pulmonary artery catheterization, Doppler ultrasound heart monitoring, and end-tidal CO2 monitoring.






Retractors


Three major types of retractors are used in spinal surgery: hand-held retractors, patient-mounted self-retaining retractors, and table-mounted self-retaining retractors. Because intraoperative radiographs are commonly used in spinal surgery, radiolucent retractors may be very helpful.



Transoral Retractors


Self-retaining retractors are usually necessary to maintain an open mouth and to depress the tongue. Self-retaining retractor rings are fixed on the upper and lower teeth (Fig. 169-3). Table-mounted retractors are attached to the operating table to retract both the palate and the tongue. These retractors may also hold the neck in a fixed position; thus, they may eliminate the need for additional skeletal traction.







Approaches



Dorsal Approaches to the Upper Cervical Spine




Lateral Transcondylar Approach


The lateral transcondylar approach is also termed the extreme lateral transcondylar approach or the far lateral approach. With this approach, it is possible to reach the lower clivus, the ventral foramen magnum, and the craniovertebral junction without significant retraction of the lower brainstem, the cervical spinal cord, or the cerebellum.


The sitting, lateral park-bench, or prone position may be used. In the prone position, the head should be turned to the side of the lesion (at least 20 degrees), and a rigid three-pin head holder should be used. The sitting position provides an excellent exposure, but it carries the risk of air embolism.


The lateral position is a viable option, because the cerebellum falls away from the operating site and venous drainage is optimized. If a modified park-bench position is preferred, the head is rotated downward, flexed, and tilted away from the shoulder.


A straight dorsolateral incision may be used, although an inverted J-shaped incision is preferred (Fig. 169-9). This incision begins at the mastoid process, extends rostrally and medially, and then extends caudally in the midline to the level of C6. Because the occipital muscles cover the craniectomy after the use of an inverted J-shaped incision (compared with a linear incision placed over a craniectomy), this incision is useful in preventing postoperative cerebrospinal fluid leakage.



Hooks are useful for retracting the bulky cervical musculature. A self-retaining cerebellar retractor works well.


One of the most difficult aspects of this operation is the development of a dissection plane along the lateral aspect of C1 and C2 without causing injury to the vertebral artery or associated venous structures.


To avoid the introduction of occipitocervical instability, it is recommended not to remove more than one half of the occipital condyle. The roots of C2 may be sectioned. Only a slight retraction of the vertebral artery, if any, is usually necessary. The cerebellum and the brainstem should not be retracted.


Salas et al.4 have defined four varieties of dorsolateral craniocervical approaches. The transfacetal approach is used to treat extradural and intradural lesions ventral to the upper cervical spinal cord. The retrocondylar approach is performed for intradural lesions that are located predominantly lateral or ventrolateral to the spinomedullary region or to expose the extradural portion of the vertebral artery. The partial transcondylar approach is performed to treat lesions that are located predominantly ventral to the spinomedullary junction. The complete transcondylar approach is performed to treat extradural lesions. The extreme lateral transjugular approach is performed to supplement the traditional lateral transtemporal approach for the treatment of jugular foramen lesions.



Ventral Approaches to the Upper Cervical Spine



Transoral Approach


A standard placement is to have the surgeon at the side and the anesthetic equipment and anesthetist at the head of the patient. Alternatively, the anesthetic equipment may be placed at the foot, and the surgeon may be at the head of the patient. The patient is positioned supine, and intubation is performed with a small endotracheal tube, which is securely fastened. Intubation when the patent is awake may be necessary if the spine is unstable. Slight extension facilitates the approach.


Although tracheotomy is not routinely used, an elective tracheotomy should be considered if the mouth does not allow adequate space for an endotracheal tube within the operating field.


Because the predominant difficulty with the transoral approach is the depth and narrowness of the operative field, a self-retaining retractor is imperative. Retraction of the uvula is also frequently necessary (see Fig. 169-3).


The soft palate may be held away from the surgical trajectory by a retractor or by suturing its border with the uvula to the dorsal palate. Alternatively, a rubber catheter may be passed through the nose and into the mouth. The distal tip of the catheter is sutured to the uvula, and upward traction is applied by gently pulling the catheter through the nose.


An incision is made in the midline of the dorsal pharynx after infiltration with a local anesthetic containing epinephrine to decrease oozing from the pharyngeal walls. The incision is carried along the tubercle of the atlas to the prominence of the C2-3 disc space. The incision may be extended, if needed, onto the soft palate and to one side of the uvula.


After dissection of the ventral surfaces of the atlas and axis laterally, a second self-retaining retractor is held to open the dorsal pharyngeal wall along the long axis of the spine. Stay sutures may be used to provide lateral retraction (see Fig. 169-1).


This surgery is relatively straightforward. Once the pharyngeal mucosa and prevertebral muscles have been cleared away, this approach offers an excellent view of the upper ventral cervical spine, which is relatively avascular.






Ventrolateral Retropharyngeal Approach


The ventral retropharyngeal approach provides access to structures from the clivus to the third cervical vertebrae without entering the oral cavity.3,1114 The advantages of this approach are lowered risks of infection and more extensive exposure of the upper cervical spine.


The patient is positioned supine, and if the incision is on the right side, the head is turned to the left. Moderate extension of the head facilitates the approach to the upper cervical structures.


The upper transverse portion of a T-shaped incision is made just under the mandible. The vertical portion of the incision meets the sternocleidomastoid muscle caudally (Fig. 169-12A). Another option is a V-shaped incision (Fig. 169-12B).13



This ventral retropharyngeal approach may be called retrovascular or prevascular surgery (Fig. 169-13).15 Prevascular surgery involves an access medial to the carotid sheath and traverses the same fascial planes as in the ventrolateral lower cervical spine surgery12 (see Fig. 169-13B). It allows adequate spinal cord decompression up to the clivus and reconstruction of the anterior column of the spine with strut grafts and internal fixation.



The dissection is medial to the sternocleidomastoid muscle and the carotid artery. The submandibular gland may be resected. The facial, lingual, hypoglossal, and superior laryngeal nerves should be identified and protected. After rostral and lateral retraction of these nerves, the hyoid bone and hypopharynx may be retracted medially.


After the platysma muscle is incised, the inferior division of the facial nerve and submandibular gland may be divided. The carotid sheath is identified and protected. The dorsal belly of the digastric muscle is traced and transected near its tendon. To retract the larynx, the stylohyoid muscle is transected. The hypoglossal nerve is identified and protected. The retropharyngeal space is opened and bluntly dissected. After retraction of the longus colli muscles, a self-retaining retractor is positioned.1,13 It may be difficult to place a self-retaining retractor in this opening. A table-mounted system may be useful in this region.



Lateral Cervical Approach


Some authors refer to the lateral cervical approach as a retrovascular variant of the ventral retropharyngeal approach.12 It is an anatomically complex access that requires sternocleidomastoid muscle eversion; exposition of the spinal accessory nerve and medial mobilization of the jugular vein, vagus nerve, carotid artery, vertebral artery, and cranial nerves XII, IX, VII16 (Fig. 169-14). Although it provides a true lateral access to the upper cervical spine, only limited access is obtained, and neither grafting nor extensive bony decompression can be achieved. It is also noted to have a significant association with vertebral artery damage.17



The major difference between a ventrolateral retropharyngeal approach and a straight ventral retropharyngeal approach is that the exposure is lateral to the carotid sheath.14,17,18


The supine or lateral position is used. The neck is extended, and the head is turned maximally. Skeletal traction or a three-point head fixator may be used.


A hockey-stick incision is fashioned along the ventral border of the sternocleidomastoid muscle. The incision begins behind the ear, proceeds caudally over the mastoid process, and extends below the mandibular angle toward the midline (Fig. 169-12C).


The external jugular vein is ligated and divided. The sternocleidomastoid muscle is divided transversely below the mastoid process. The occipital artery is also ligated. The greater auricular and accessory nerves are identified and protected. A dissection plane is developed dorsal to the carotid sheath and the retropharyngeal space.16


This approach may be fashioned for primary tumors of the upper cervical spine (Fig. 169-15).




Dorsal Approaches to the Subaxial Cervical Spine





Ventral Approaches to the Subaxial Cervical Spine



Ventromedial Approach


Exposure of the disc space and vertebral body is usually accomplished by a ventromedial approach.2225 The patient is positioned supine with the head and neck neutral or slightly extended. Extension of the upper cervical region, with chin retraction, is helpful to reach the C2-3 level. Extension of the midlower cervical region is helpful to reach the high thoracic region. The head is turned away from the surgeon. In the setting of severe cervical stenosis, extreme extension of the cervical spine may cause spinal cord damage and therefore should be avoided.


The sternocleidomastoid muscle is the surface incision landmark for the ventral approach. Either a transverse or a longitudinal incision is appropriate (see Fig. 169-14). Rengachary26 suggests a longitudinal incision for patients with a short neck and kyphotic deformity. The incision begins below the angle of the mandible, extends forward toward the hyoid bone, extends caudally over the sternocleidomastoid muscle, and terminates in the suprasternal notch (see Fig. 169-14).26


A transverse incision may be used for patients with short necks and limited pathology, whereas a longitudinal incision parallel to the sternocleidomastoid muscle may be used for long thin necks with more extensive pathology. Right-handed surgeons may prefer to use right-sided incisions, although it is usually optimal to approach the patient from the side opposite the most prominent pathology. After the incision of the platysma muscle, the sternocleidomastoid muscle is freed from its attachments.


The carotid sheath is easily identified under the muscle. Both may be retracted laterally by the surgeon’s fingers (Fig. 169-16A). Rostrally, the 12th cranial nerve and, caudally, the recurrent laryngeal nerve should be avoided. Other structures that cross the wound transversely may be sacrificed if necessary. These include the inferior and superior thyroid veins and arteries, the facial veins, and the inferior belly of the omohyoid muscle. Injury to the superior laryngeal and superior thyroid artery should be avoided.


Aug 31, 2016 | Posted by in NEUROLOGY | Comments Off on Surgical Incisions, Positioning, and Retraction
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