Imagine you are sleeping soundly in your warm bed when a tingling in your arm awakens you. In a haze of sleep, you reposition your arm, roll over and fall back asleep. The tingling, the result of compression of a nerve or blood vessel, caused you to change positions to decrease pressure, maintain blood flow, stop pain and avoid injury. Patients undergoing surgical procedures who have had general, regional or sedation anesthesia cannot perform this function due to the loss of protective reflexes, making them susceptible to peripheral nerve and vessel injuries. Imagine the reaction of a patient awakening from surgery only to find an injury that might have been prevented. The circulating nurse collaborates with the anesthesia provider and the surgeon to position the surgical patient in a manner that prevents injury.1
Lower extremity nerves that are most susceptible to injury include the lumbosacral plexus, femoral nerve, common peroneal nerve, tibial nerve and the sciatic nerve. The associated vessels include the bilateral common iliacs, femoral, tibial and doralis pedis arteries. Understanding where these nerves and vessels are located is the first step in preventing their injury. The primary means of avoiding injury to these lower extremity nerves is to prevent stretch and pressure on these structures.2
Anatomic Considerations for the Lower Extremities: Ligaments and Nerves
The lumbosacral plexus is made of nerves from the ventral rami of T12 to L4 and branches to the femoral, obturator, ilioinguinal, iliohypogastric, genitofemoral and lateral femoral cutaneous nerves. The sacral plexus is made up of nerves from the ventral rami of the S1 to S3 spinal nerves and forms the sciatic, pudendal, posterior femoral cutaneous and muscular branches to the pelvis.2,3 The other most common injuries of this plexus are a result of flattening the natural spinal curves in the supine position, suture placement, compression when positioned laterally and ischemia from occlusive pressure over vessels.2
The sacroilliac ligaments bind the sacrum and pelvic bones to the hipbones. The ligaments measure about 1.5 to 2 inches of layered fibers that stabilize the lower spine. The sacrotuberous and the sacrospinous ligaments attach the sacrum to the lower angle of the pelvic bones and attach the ischial tuberosities. The ischium bears the weight of the upper torso when seated.2,3 The natural lower spinal curve terminates at the sacroiliac joint at the base of the lumbar vertebrae. Flattening or causing torsion of the natural lower spinal curve can cause severe postoperative pain that mimics sciatic pain. Extremes of flexure can result in tearing, or avulsion of the superior aspect of the hamstring muscle. Patients with existing coccygeal injury are susceptible to strain at the sacroiliac region.2,3,4
The femoral nerve is formed within the psoas major muscle by posterior divisions of the second, third and fourth lumbar nerves. It emerges from the lateral border of the psoas muscle to descend in the groove between the psoas and iliacus major muscles and enters the thigh by passing beneath the inguinal ligament lateral to the femoral artery and divides into multiple branches that include segments of the ilioinguinal nerve. This nerve serves the anterior muscles and skin of the thigh from the inguinal ligament to the knee.2,3
The femoral and ilioinguinal nerves can be injured by compression with self-retaining retractors during abdominal hysterectomy; pressure and stretch in lithotomy position with excessive hip abduction and external rotation; inadvertent suture placement; femoral artery cross-clamp-induced ischemia and high tourniquet pressure compressing the nerve.2
The sciatic nerve is made of two divisions that travel in the same sheath. These divisions are the tibial and peroneal nerves. The tibial nerve is made up of the anterior branches of L4 to S3, and the peroneal nerve is made up of the posterior branches of L4 to S3. This sheath leaves the pelvis through the greater sciatic foramen and descends posteriorly between the ischial tuberosity and the greater trochanter down the posterior thigh, where it divides into the tibial and common peroneal nerves at the level of the knee.3
Improper surgical positioning can injure the sciatic nerve. This injury occurs when the nerve is put under tension in the lithotomy position when the hip is flexed and the knee straightened or when the flexed hip and flexed knee are excessively rotated.3 Patients with peripheral vascular disease are at risk from gluteal ischemic pressure when positioned supine.5
Of the sciatic nerve branches, injury occurs most often in the common peroneal nerve, usually as a result of positioning during surgery.1-3 The common peroneal nerve is vulnerable to direct pressure at the fibular neck when surgery is performed in the lateral decubitus position or in lithotomy position with inadequate padding between the fibular neck and a stirrup or leg strap.2,4,5
Arterial Supply and Venous Drainage of the Lower Extremity
Lower extremity positioning requires knowledge of the vasculature of the lower pelvis and leg. The oxygen-saturated arterial blood supply bifurcates from the lower aorta into the internal and external iliac arteries. The superficial femoral arteries branch off laterally through the thigh into the popliteal artery at the knee. The deep femoral profunda arteries create three branches that run deep into the musculature of the upper thigh. The tibial arteries bifurcate below the knee and course distally through the anterior and posterior calf to the foot. The peroneal artery is the largest branch of the posterior tibial artery that supplies the ankle and terminates in the heel at the calcaneal artery. The foot is supplied by the plantar arteries that unite with the dorsalis pedis on the dorsum of the foot. The dorsalis pedis is also a continuation of the anterior tibial arterial supply. Compression and/or occlusion of the arterial supply not only causes tissue ischemia, but deprives the nerves of their blood supply.2,3,4
The venous drainage is equally important. Anatomically, the veins are critical for the return of blood that bears metabolic waste from living tissue. Occlusion of veins prevents the return of desaturated blood to the lungs for re-oxygenation and promotes accumulation of blood cells that lead to deep vein thrombosis within the vessel.1,2,5 A thrombus (clot) can become embolic and travel through the venous system via the vena cava directly into the right atrium of the heart. The force of the heartbeat causes the right ventricle to send the clot directly to the lungs. A clot in the lungs (pulmonary embolus) prevents the exchange of gases in the alveoli creating an obstacle to oxygenation and movement of the blood through the heart.2,5
The venous return from the lower extremity begins at the foot with the dorsal venous arch and moves up the anterior tibial vein. The movement of venous blood is very low pressure and requires some muscular contraction to move it along. The blood flows proximally through the tibial and popliteal veins to the saphenous and femoral veins where they join the iliac veins. The iliac veins converge with the vena cava and the blood flows into the right atrium and ventricle back to the lungs for oxygenation.2
Hemodynamic Considerations for Positioning the Lower Extremities
Patients undergoing lower extremity surgical procedures can have a variety of anesthetic approaches.2,3 Regional anesthesia, such as spinals or epidurals, have risk factors specific to the manner of administration, which are discussed later in this module.3,4
Patients under general anesthesia have a higher risk of neuro- or vascular compromise because of complete immobility, loss of natural protective reflexes, surgical positioning and the use of many types of surgical instruments.1-3 As a rule, the arterial system is monitored and controlled by several anesthetic agents. Blood volume and pressure can be modified with drugs. Usually, a paralytic agent is used so the patient’s breathing can be controlled.3 During induced surgical paralysis, body areas under pressure from body weight and positioning devices cannot shift or reposition to relieve tissue sensory deficits.2 Vascular stasis and compression of nerves can go uncorrected for prolonged periods of time, leading to permanent injury. Care must be taken to use positioning aids, such as gel pads, to provide an alternating pressure surface to relieve as much pressure as possible on the patient’s tissues.1,2
Another consideration involves the actual positioning process of moving the patient’s lower limbs. If the patient is positioned in a lateral position, care is taken to prevent the weight of the upper leg pressing on the lower leg.2 A pillow should be placed between the patient’s knees. The patient’s bony pelvis is under pressure from the weight of the torso. Use of a gel pad mattress offers some relief.2
Patients in a prone position have the potential for injury to the knees and dorsum of the foot. Gel kneepads or sheets can be used. The feet should have enough elevating padding at the dorsum to prevent the toes from resting on the mattress or extending over the foot of the OR bed. Other injuries could occur to the feet and toes if they are hanging off the OR bed when draped and a table or piece of equipment is pressed against them.1,2
Positioning a patient into the lithotomy position requires two people moving the legs simultaneously. The process is performed slowly after the anesthesia provider has given the “OK” to proceed.1,2 Both positioning personnel should grasp the patient’s ankle with one hand and the fleshy portion of the calf with the other. The legs should be held together and flexed slowly at the knees as the limb is lifted. As the legs are separated to place them into the stirrups, care is taken not to force any flexion movements or let the hip joint externally rotate.1,2,4-6 The legs are gently placed into the stirrups and secured.
The blood in the leg veins can rapidly autotransfuse the patient’s cardiovascular system, causing changes in the vital signs if the limbs are raised too quickly. Moving one leg at a time can cause lower back strain over the sacroiliac joint.2,5 When the procedure is completed, the legs are slowly lifted from the stirrups, knees slightly flexed, legs brought together, then lowered. The process of moving the legs out of the stirrups too quickly can create a hemodynamic shift causing hypotension.2,5
Mechanisms of Injury During Positioning
The five most common mechanisms for nerve and vessel injuries include: stretch, compression, ischemia, metabolic issues and surgical section.2,3 Stretch and compression can be avoided by proper positioning. Stretch can be prevented by positioning the patient while he or she is awake, before being returned to a position that facilitates induction of anesthesia. If a position is uncomfortable while the patient is awake, it can cause injury when maintained for a long period of time under anesthesia.3 If the patient experiences discomfort while awake, injury can occur if the nerve(s) or vessel(s) is compressed for extended time periods. Proper padding of bony areas, minimizing the time that a tourniquet is inflated and preventing OR personnel from leaning on the patient will help avoid pressure injuries.1,2
Lithotomy position is associated with changes in intracompartmental pressure in the lower extremities, depending on the method used to support the legs.6 Leg support with stirrups attached to the OR bed employs three different types of table attachments.2 The first type is the knee-crutch stirrup. This type is commonly found in urology suites.2 The legs are positioned with the knees supported with the feet dependent. The full weight of the leg is balanced on the knee compartment. If pressure is placed on the knee or calf to support the lower extremity (using stirrups and a knee support device), it can result in pressure on the vessels and nerves within the compartment and can cause vascular or nerve injury.2,6
The second type of leg holder used is the sling, or “candy cane” stirrup. The upright posts of the stirrups are mounted on the sides of the OR bed at the level of the patient’s hips.2 When placed in the sling stirrups, the knees are bent in toward the patient’s abdomen and the feet are placed in sling-straps that hold the bottom of the foot and the posterior ankle to raise the legs.2,3 Extreme flexion at the hip can result in ilioinguinal nerve damage by crush injury.2 The pressure is distributed at the level of the foot and ankle. Elevating the lower extremity using a sling support at the ankle decreases pressure at the knee, but places the weight of the leg on the sole of the foot and ankle. The feet must be well padded to prevent nerve damage that can result in permanent foot drop.1,2,3 Care is taken to avoid allowing the lateral aspect of the legs to rest against the upright post of the stirrup frame. This can result in serious peroneal nerve injury from pressure.2
The third type of leg holder is a boot-style, known by several names, such as “Yellow Fin,” “Lloyd-Davies” or “Allen” stirrups.2 The boot-type stirrup supports the leg from the inferior aspect of the knee along the calf and under the length of the foot. The weight of the leg is evenly distributed. These stirrups are commonly used for longer surgical procedures where the abdomen and the perineum must be accessed.2,6 The levels of the legs in lithotomy during the surgical procedure can vary from low (even with the OR bed) to high with the legs and feet elevated into the air.2
Constant external compression applied by antithromboembolism stockings does not decrease intracompartmental pressure in the lower extremities. The use of intermittent external compression (e.g., sequential compression devices), however, reduces this pressure increase and decreases the likelihood of nerve or vessel injury from increased intracompartmental pressure.2,3
Compartment Syndrome Associated With Lower Extremity Positioning
Each muscle group of the lower extremity is enclosed in fascia, which is a tough, fibrous connective tissue. Fascia is minimally flexible and does not expand in response to abnormal swelling of encased muscle tissue. In addition to nerve, vessel or superficial tissue damage, swelling in the fascial compartments of the lower extremity can lead to permanent muscle destruction known as compartment syndrome.2,6 Compartment syndrome can be caused by crushing, bleeding into tissue, vessel obstruction by a clot or prolonged pressure during periods of immobility under anesthesia. Patients with blood dyscrasia and anticoagulant therapy are at risk. Patients who have been in lithotomy greater than three hours should be evaluated for compartment syndrome postoperatively.2,6
The mechanism of compartment syndrome is a repetitive cycle. Muscle tissue becomes ischemic under pressure, causing plasma to seep out of the capillaries. This increases fluid loss from the arterial circulation into the surrounding muscle tissue, causing even further swelling. Despite the changes in circulation, arterial pulses may appear unchanged.2,6 If the pressure is not relieved, muscles, vessels and nerves will infarct and decay. Postoperative patients with a positioning injury caused in the OR may take several hours to manifest the syndrome. If the patient had regional anesthesia, the process can delay the diagnosis when no verbalization of discomfort is made.2,3 ,6
Signs and symptoms of compartment syndrome include complaints of burning and extreme deep ache in the muscle group in the patient with intact sensory perception.6 Flexion and extension of the limb will cause increased pain. The extremity may have a localized enlargement and tenseness with a firmness that does not depress when pressure is applied. Compartment syndrome that goes untreated can lead to muscle breakdown (rhabdomyolysis) and the release of myoglobin into the cardiovascular system.2,6 The myoglobin is passed into the major organ systems, causing multi-system organ failure and death. Urinalysis reveals dark, brownish urine with free myoglobin.2,6
Compartment syndrome is treated surgically with long linear incisions along the length of the fascial covering of the muscle group (fasciotomy) to manually release the pressure.2,6 The incisions are left open for prolonged periods of time, sometimes weeks or months, thus requiring antibiotic therapy. Many of these incisions require skin grafts for complete tissue coverage. Muscle tissue does regenerate to a large degree, but vessels and nerves can suffer irreparable destruction.2,6
Patients Who Are at Risk for Lower Extremity Injury
Metabolic diseases such as diabetes can also cause neuropathies. It is important to assess a patient’s medical, surgical and social history and document pre-existing neuropathies or peripheral vascular disease when planning perioperative care.3 Additional risk factors for neurological or vascular compromise include the use of anticoagulants, nicotine, oral contraceptives or hormone replacement therapy (estrogens), pregnancy, sepsis or history of previous DVT.2,3,6
Extremes of body weight and length of surgery also increase risk of lower extremity nerve and vessel injury, especially when the patient undergoes surgery in the lithotomy position.3 ,4
Regional anesthesia, such as a spinal or epidural, has been a potential cause of nerve damage. Documentation serves as a record of what steps were taken in a patient’s care and when the need to examine that care arises.1-3 Documentation and checklists serve another important purpose: to remind the provider of steps that need to be taken in a patient’s care.3 Documentation not only provides a record of the steps taken, but it also focuses attention on specific aspects of patient positioning that prevent injury to the lower extremities.4
AORN (The Association of periOperative Registered Nurses) recommends six practices with regard to positioning the patient in a perioperative setting.1 Outcomes of these guidelines include optimal exposure of the surgical site, proper access for airway management, proper ventilation, proper monitoring access for anesthesia personnel, physiological safety of the patient and maintenance of patient dignity by controlling unnecessary exposure. The six practices are:1
1. Preoperative assessment for positioning needs should be made before transferring the patient to the procedure bed. The preoperative interview should include questions to determine patient tolerance to the planned position. The OR nurse should assess both patient and intraoperative factors. Patient factors include age, body build, skin condition, nutritional status, preexisting conditions and mobility limits. Intraoperative factors include anesthetic concerns, length of the planned procedure and position required for the planned procedure.
2. Positioning devices should be readily available, clean and in proper working order before placing the patient on the procedure bed. Properly functioning equipment and devices contribute to patient safety and help provide adequate exposure of the surgical site. Selection criteria for positioning equipment includes its availability in a variety of sizes and shapes; durability; ability to maintain normal capillary interference pressure (32 mmHg or less); resistance to moisture and microorganisms; radiolucency; fire resistance; non-allergenic properties; ease of use; cleaning; storage and retrieval; and cost-effectiveness.
3. The perioperative nurse should actively participate in monitoring patient body alignment and tissue integrity based on sound physiological principles. Use of the proper number of personnel for patient positioning decreases the risk of positioning injury. Catheters, tubes and cannulas can be accidentally pulled out if too few personnel are used. Maintaining proper body alignment and supporting the extremities also decreases the chance of injury during and after positioning.
4. After positioning, the perioperative nurse should evaluate the patient’s body alignment and tissue integrity. This evaluation should include, but not be limited to, the respiratory, circulatory, neurological, musculoskeletal and integumentary systems. Unusual findings in any of these areas can lead to lower extremity nerve injury if not corrected.
5. Documentation of surgical positioning should be consistent with AORN’s “Recommended practices for documentation of perioperative nursing care.” This documentation includes the nursing assessments, interventions and treatments, and evaluations of the quality of the care delivered. Documentation of care activities provides a picture of the care delivered and its outcomes.
6. Policies and procedures related to positioning should be developed and reviewed annually, revised as necessary and be available in the practice setting. These policies and procedures should include, but not be limited to: assessment and evaluation criteria and documentation; anatomic and physiological considerations; safety interventions; documentation of patient position or repositioning, positioning devices and personnel positioning the patient, and positioning device care and maintenance.
Careful positioning, along with knowledge of anatomy and careful documentation, can greatly reduce the incidence of lower extremity nerve and vascular injury in the OR.
EDITOR’S NOTE: Don Beissel, RN, MSNA, RN, CRNA, was the original author of this educational activity, but has not had the opportunity to influence the content of this current version.
OnCourse Learning guarantees the content of this educational activity is free from bias.
Nancymarie Phillips, PhD, RNFA, CNOR(E), is professor of perioperative education for nurses and technologists at Lakeland Community College, Kirtland, Ohio.
1. AORN. Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc.; 2014;183-208, 481-499.
2. Phillips NM. Berry and Kohn’s Operating Room Technique. 12th ed. St. Louis, MO: Elsevier; 2013;489-495, 501, 596, 783.
3. American Society of Anesthesiologists Task Force on Prevention of Perioperative Peripheral Neuropathies. Practice advisory for the prevention of perioperative peripheral neuropathies: an updated report by the American Society of Anesthesiologists Task Force on prevention of perioperative peripheral neuropathies. Anesthesiology. 2011;114(4):741-754. doi: 10.1097/ALN.0b013e3181fcbff3.
4. Bouyer-Ferullo S. Preventing perioperative peripheral nerve injuries. AORN J. 2013; 97(1):110-124.
5. Operating room risk management: patient positioning. ECRI Institute Web site. https://www.ecri.org/Documents/RM/ORRM_TOC/ORRM_Surgery_PatientPositioning.pdf. Published August 2011. Accessed November 10, 2014.
6. Bauer E, Koch N, Janni W, Bender G, Fleisch M. Compartment syndrome after gynecologic operations: evidence from case reports and reviews. Eur J Obst Gynecol. 2014;173(2):7-12.