35.1.1 The Clinical Effects of Bed Rest

Bed rest is the initial component of a nonoperative strategy for spine trauma and has been shown to be effective in selected cases, ^{1 ,​ 2} even if brief. ^{1 ,​ 3} Conversely, bed rest has not been shown to have substantial therapeutic value for nontraumatic degenerative pathologies (see Chapter 37). ^{4 ,​ 5} The efficacy of bed rest for the management of trauma relates in part to the fact that spontaneous remodeling of the spinal canal often occurs over time. ⁶ Bed rest enables this process. However, bed rest is associated with profound physiologic and biomechanical effects. Although the physiologic effects of bed rest are not directly related to spine biomechanics and associated principles, the desire to minimize adverse outcomes indeed makes them significant and thus worthy of discussion here. The adverse sequelae of bed rest include the following: (1) pneumonia and other pulmonary complications; (2) fluid retention; (3) problems associated with venous stasis (deep vein thrombophlebitis, pulmonary embolism); and (4) integument complications (e.g., pressure sores).

The pulmonary, fluid retention, and vascular complications of bed rest are all of clinical significance. The human body is not designed to be at rest in bed for prolonged periods of time. Therefore, illness-imposed bed rest should in general be limited. On the other hand, assumption of the upright posture by a quadriplegic patient, particularly in the postinjury period, is associated with decreased tidal volume and vital capacity. ⁷ This is particularly relevant during the ventilator weaning process. This fact alone may obligate a period of bed rest that is longer than desirable. Although early surgery in general is a positive factor regarding mobilization and ambulation, it may not be of assistance in this particular scenario. In fact, it may contribute to the physiologic and mechanical factors that impede ventilator weaning (Fig. 35.1).

Bed rest is associated with focal points of integument (skin) pressure. In a malnourished and insensate patient with integument vascular underperfusion, bed rest can result in pressure sores. Pressure sore location is a function of position, as well as a host of other factors. Assumption of the supine position results in pressure points on the elbows, dorsal thoracic region, occiput, heels, scapulae, and sacral region (Fig. 35.2a).

Assumption of the lateral decubitus position results in pressure points on the greater trochanter, ribs, shoulder, lateral knee, and lateral malleolus of the ankle (Fig. 35.2b). Furthermore, shoulder distortion, including dislocation, can result. Assumption of the sitting position concentrates pressure on the ischial tuberosity and heels (Fig. 35.2c). Skin traction can result in injury, as well. An example of this is related to traction in the sacral region as a result of a slumped posture (Fig. 35.2d). The end result of relative or complete inattention to integument care in an insensate patient can be devastating (Fig. 35.2e).

With this knowledge, the mechanical cause of a pressure sore can be determined, and strategies to manage or prevent it can be crafted. Obviously, the intermittent application of focal pressure can be achieved by limiting the time spent in any given position. This is the crux of all mechanical prevention and treatment strategies for pressure sores.

35.1.2 The Consequences of Patient Positioning

Intermittently turning the patient with an unstable spine can limit the aforementioned focal pressure applications. This positive effect must be weighed against the potential negative aspects of turning, such as an adverse effect on spine stability.

Turning, if performed without the application of distraction, compression, torsion, translation, or angular stresses to the spine, is theoretically beneficial, at least physiologically. Unfortunately, however, each of the aforementioned stresses can be applied to the spine during the turning process (Fig. 35.3). The application of distraction, compression, torsion, shear, or angular stresses to the spine can thus result in spine deformation and the potential for further neurologic injury.

35.1.3 Speciality Beds and Frames

The use of specialty beds and frames has significantly contributed to the surgeon’s ability to mobilize and position patients, both in and out of the operating room. This even includes the management of low back pain. ⁸ During the initial hospitalization, one of the most precarious time frames regarding the exacerbation of spinal cord injury is during intraoperative positioning of the patient. All of the aforementioned spine deformations can occur and are most likely to occur when the prone position is employed intraoperatively. The intraoperative prone position usually requires a 180-degree turn, with the potential for spine deformation and spinal cord injury (Fig. 35.4). Rigid fixation of the head to the chest, as with a halo or operative frame, does not prevent this. In fact, it may exaggerate spine deformation (see Chapter 36).

Continuous-motion rotating beds (e.g., kinetic treatment tables, or KTTs) can be used to decrease the pulmonary and psychiatric–cognitive complications associated with motionless bed rest. They may also facilitate skin care and minimize spinal motion. ⁹ Shear stresses may be applied to the spine and integument (Fig. 35.5) and may in fact be encouraged by the continuous-motion rotating bed strategy.

Uniform integument pressure beds, such as any of the variety of available “bead beds,” can pose a risk for spine deformation (Fig. 35.6). Alternating-pressure mattresses provide an alternative, but with marginal advantage. ¹⁰ Of note, the 45-degree sitting position is associated with substantially greater integument interface pressures than other positions. ¹⁰ Circle electric beds, which rely on head-over-foot turning, lessen the latter concerns but increase the risk for distraction and compression (Fig. 35.7) as well as hypotension during transient assumption of the upright posture.

Prone positioning in the intensive care unit or operating room can distribute skin pressure to a larger surface area (Fig. 35.8). In the operating room, turning the patient to the prone position can be achieved with frames, such as the Jackson table. The use of such turning and positioning adjuncts has been shown to be safer than manual turning techniques. ¹¹ It is emphasized that prone positioning has been associated with potentially catastrophic complications, such as respiratory arrest and spinal cord injury.