Proper positioning of orthopaedic patients on the operating table is important to prevent injury. However, despite their unique symptoms, medical problems, and physical characteristics, these patients are typically positioned using standard surgical positions. Each position can expose various nerves to potential for injury, and it is important to be aware of them while positioning the patient.

Lateral position risks
The most common injuries associated with the lateral position—used in both shoulder arthroscopy and hip arthroplasty—are neurapraxias of the brachial plexus. Neurapraxia can result either from excessive traction of the surgical extremity or from prolonged pressure on the contralateral axilla. To prevent this, the axillary roll should be placed caudad to the axilla, on the rib cage, and not in the axilla. If the axillary roll migrates into the axilla, undue pressure on the brachial plexus on the dependent side can potentially occur.

Another potential injury is radial nerve palsy of the nonsurgical arm. For nonshoulder surgery, when the patient is in the lateral decubitus position, the “up arm” is often positioned on a lateral arm board. Incorrect positioning, lack of padding, a combination of both, or settling of the patient’s body can cause the radial nerve to be compressed by the edge of the arm board at the bend of the elbow.

A “bean bag” may be used to stabilize patients while positioning them in the lateral decubitus position. During positioning and throughout the procedure, attention should be paid to the hard edges of the bean bag to ensure that the soft tissues of the lower extremity aren’t at risk for compartment syndrome and that unnecessary pressure is not being exerted on the upper extremity, which could cause neuropathy.

Lower leg peroneal nerve injury may also occur when the patient is in the lateral position due to direct compression of the fibular head against the operating table. It is imperative to properly pad bony prominences such as the fibular head, greater trochanter, and ankles on the dependent side. Placing pillows between the knees and ankles will also help prevent saphenous nerve injury. Awareness of excessive flexion and extension of the hip in a lateral position is necessary to avoid lumbar plexus or sciatic nerve injury by stretching.

The use of an anterior hip support in the lateral position helps to stabilize the patient, but is also a potential source of neurapraxia. When applied, this device may place undue pressure against either pubic symphysis or the anterior superior iliac spine, particularly if the latter is not properly padded. More significantly, if the hip support is improperly positioned, it can cause occlusion of large blood vessels.

Recently, cases of femoral artery occlusion have been reported in obese patients being treated in the lateral position for femoral neck fractures. In each case, the dependent lower limb became mottled and cool with increased capillary refill after the anterior and pelvic support apparatus was applied. When the support was removed, the symptoms resolved.

Prone position
The prone position is most often used in orthopaedic surgery for spine procedures (Fig. 1). Peripheral nerve injury is possible and the brachial plexus is susceptible to injury in several places when the patient is in the prone position. Pressure on the humeral head can compress the brachial plexus if the patient’s arms are hyperabducted; the brachial plexus can also be compressed against the first rib secondary to excessive force on the clavicle.

In positioning the upper extremity, the arms at the shoulders must be in 90 degrees or less abduction, the elbow in 90 degrees flexion, and the forearms pronated. Positioning patients on devices with posts, such as the Jackson frame, may cause compression of the femoral nerve or lateral femoral cutaneous nerve. Because the face, breasts, and genitalia are at particular risk for compression injury, careful attention must be paid to the initial positioning, with frequent checks to ensure that shifting has not caused damage.

Postoperative visual loss (POVL) is one of the most feared complications of using the prone position. Although POVL does not occur frequently, it can have devastating consequences. Most POVL is not due to incorrect positioning; central retinal artery occlusion due to direct pressure on the eye accounts for only a small fraction of POVL incidents. Most POVL cases are secondary to ischemic optic neuropathy, the exact mechanism of which is unknown. It has, however, been associated with the prone position, Mayfield pin headholder use, anesthetic duration greater than 6 hours, and blood loss greater than 1 liter.

The following strategies may potentially decrease the incidences of POVL:

• Use staging to avoid surgical procedures longer than 6 hours.
• Carefully position the patient and frequently check his or her eyes.
• Slightly elevate the patient’s head (10 degrees to 15 degrees) to reduce periorbital edema.
• Maintain the patient’s mean arterial blood pressure within 20 percent of preoperative values.
• Maintain the patient’s hematocrit levels at 25 or higher.

Conclusion
As physicians, we must maximize the benefits and minimize the risks that patients face on the operating table. Vigilance, communication, and careful planning are necessary whether the procedure is seemingly simple or overwhelmingly complex. No matter how thoughtful our approach, however, complications and unexpected outcomes do occur. Therefore, we must strive to achieve the best possible surgical experience for every patient.

Sarah Gerken, MD, is an assistant professor in the Department of Anesthesiology at the University of Toledo Medical Center

Editor’s Note: Articles labeled Orthopaedic Risk Manager (ORM) are presented by the Medical Liability Committee under the direction of David H. Sohn, JD, MD, ORM editor.

Articles are provided for general information and are not legal advice; for legal advice, consult a qualified professional.

Email your comments to feedback-orm@aaos.org or contact this issue’s contributors directly.

Editor’s Note: This is the second of two articles on preventing injuries due to positioning during orthopaedic surgery. This article covers risks for the lateral and prone positions; the first article covered the supine and beach chair positions (See “Preventing Positioning Injuries: An Anesthesiologist’s Perspectives,” AAOS Now, January 2013).