Fig. 8.1
Patient in the lateral decubitus position
Pillows, blankets, or a gel donut are then placed beneath the patient’s head to support it in a neutral position. The patient’s eyes, especially the dependent eye, should be checked to ensure that they are free of pressure which could lead to postoperative blindness. The downward facing ear should be checked to ensure that it is not bent. The patient’s chest is then lifted, and a small axillary roll is placed beneath the patient’s upper ribs. The axillary roll functions to raise the patient’s chest off of the OR bed and remove mechanical compression of the neurovascular structures in the patient’s axilla. This will allow room for expansion of the chest wall during respiration, adequate blood flow to the dependent arm, and will prevent brachial plexus traction. If the axillary roll is placed too high, the roll itself could cause compression of the structures in the axilla which it is designed to protect. By palpating the radial artery pulse on the patient’s dependent arm, the surgeon can ensure that the axillary role is not impeding the blood flow through the axillary or brachial artery (Figs. 8.2 and 8.3).
Fig. 8.2
Image illustrating the proper placement of the patient’s arms and head in the lateral decubitus position. Note that the head is elevated so that the cervical spine remains in neutral alignment and that the eyes are free from external pressure
Fig. 8.3
Placement of the axillary roll in the lateral decubitus position. The roll is placed underneath the upper ribs and not within the axilla itself where it would cause direct compression of the axillary artery and brachial plexus
Next, the patient’s chest and abdomen are supported in the lateral position by tightening the draw sheet around chest rolls placed on either side of the patient. If a vacuum bean-bag positioning device is used, it should be molded around the patient’s body, and negative pressure should be applied to create a rigid structure. If the patient is female, care should be taken to ensure that her breasts are free and particularly that there is no pressure on the nipples.
The patient’s dependent arm, which is outstretched, is then supported by an armrest and padded with a foam or gel pad. By keeping this arm in supination, the ulnar nerve is protected as it passes through the cubital tunnel [5]. The upper arm is secured to an arm board with shoulder flexion ≤90° [6].
A foam or gel pad is placed under the dependent knee. This provides some protection to the common peroneal nerve as it crosses over the head of the fibula. A pillow is placed in between the patient’s legs and feet. Both legs are placed in slight flexion which provides stability to the patient’s pelvis and reduces tension on the psoas muscle and the nerves of the lumbar plexus. Another pad is placed under the patient’s feet. When positioning has been completed, Velcro safety straps are passed over the patient’s hip and shoulder to provide further stability. Three-inch silk tape may be used as well to increase stability, and some surgeons prefer to cross the tape over the patient’s legs as seen in Fig. 8.1. If the shoulder tape lays over the patient’s upper arm, the elbow and radial groove of the humerus should be avoided in order to prevent injury to the ulnar or radial nerves respectively [10, 11]. Padding may be placed under the tape to protect the patient’s skin.
Finally, the bed may be placed into slight flexion as described above based on the surgeon’s preference. If this maneuver is performed with the bed already in the reverse Trendelenburg position, the surgeon can ensure that the patient’s upper body remains parallel to the ground [10]. It has been suggested that increasing the amount of flexion of the bed results in higher skin-to-surface interface pressures and this may increase the likelihood of pressure ulcer formation or rhabdomyolysis [12]. Before beginning the case, fluoroscopy should be used to ensure that there will be proper visualization of the surgical target. For minimally invasive surgeries, it is critical to obtain good fluoroscopic images. To obtain a true lateral image, the C-arm is brought in perpendicular to the floor (90°). The table is then placed in Trendelenburg or reverse Trendelenburg until a true lateral image with linear endplates and superimposed pedicles is achieved. Following this, the C-arm is rotated so that it is parallel to the floor in order to obtain a cross-table AP image (0°). The left-right tilt of the table is adjusted until a true AP image with midline spinous processes and symmetric pedicles is achieved. This process may be especially complicated in patients with scoliosis where there is often axial rotation of the spinal segments; however, ensuring that the patient is in the true lateral position with good fluoroscopic images will help the surgeon to avoid inadvertently damaging the endplates, neural structures, and visceral or vascular structures anterior to the spine during lateral surgery (Fig. 8.4).
Fig. 8.4
Patient in the lateral decubitus position with the bed flexed. Note that the point of flexion is underneath the iliac crests which allows for an improved retroperitoneal exposure
8.3 Complications Associated with Patient Positioning
8.3.1 Pressure Ulcers
Pressure ulcers have been reported to occur in anywhere from 8.5 to 66 % of patients in the immediate postoperative period [6, 13–17]. Schultz et al. found that 89 out of 413 (21.5 %) surgical patients developed pressure ulcers over six postoperative days. These ulcers were primarily stage I and were more likely to occur in patients who were older, had diabetes, and who had smaller body mass [16]. The development of these ulcers is also related to the length of the surgery [5, 13].
Pressure ulcers occur when external pressure is so great that subcutaneous blood flow is compromised to the point where the skin and subcutaneous tissue hypoperfusion results in tissue ischemia and eventually necrosis. More specifically, ulcers occur when the external pressure exceeds the capillary filling pressure of ~32 mmHg. Longer operative times mean longer periods of hypoperfusion to pressure points and increase the likelihood of ulcer formation [6]. The most common sites of pressure ulcer formation are the sacrum, heels, ischium, and trochanter, and special attention should be paid to ensure that these areas are appropriately positioned and padded for surgery [5].
To prevent the formation of pressure ulcers during surgery in the lateral decubitus position, it is important for the surgeon to make sure that all dependent areas and boney prominences are properly padded after positioning. Ideally, the circulating nurse should also be vigilant during the procedure to ensure that the patient does not slip out of position underneath the drapes. Despite these precautions, if a patient develops pressure ulcers as a result of surgery, this should be disclosed to the patient and the wound should be cared for appropriately. Severe ulcers may require evaluation by a plastic surgeon.
8.3.2 Peripheral Nerve Injury
Perioperative peripheral nerve injury is reported to occur after 0.03–0.1 % of surgeries [9, 18, 19]. Possible mechanisms of peripheral nerve injury during spine surgery include direct compression, trauma, ischemia, stretch, or inflammatory processes [18]. Peripheral nerve injury may occur when the nerve is stretched beyond 5–15 % of its resting length [18, 20–22]. This in turn increases the intraneural pressure and leads to compression of the vasa nervosum resulting in decreased tissue perfusion and nerve fiber ischemia [20]. Similarly direct nerve compression may also lead to a reduction in perfusion pressure and subsequent nerve ischemia thereby slowing nerve fiber conduction [18, 23]. The most common site of perioperative peripheral nerve injury is the ulnar nerve which occurs in 0.5 % of patients undergoing noncardiac surgery [9, 24]. The ulnar nerve may be more prone to injury if there is a preexisting subclinical neuropathy. Abnormal nerve conduction has been observed in the contralateral ulnar nerve in patients who developed perioperative ulnar nerve injury [25]. Furthermore, ulnar nerve injury is more common in males. This may occur because men have a statistically larger coronoid process of the ulna, while women have increased fat over the medial aspect of the elbow [26]. Another common site of peripheral nerve injury during surgery is the brachial plexus. Brachial plexus injury more commonly involves the upper nerve roots [18]. In the lateral decubitus position, brachial plexus injury may occur if the axillary roll is place too high within the axilla itself causing injury due to direct compression. On the nondependent side brachial plexus injury may occur if the nondependent arm is hyper-abducted or if the head is tilted downward. Extreme elbow flexion or extension should also be avoided [18].
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