Nerve injury associated with pelvic surgery

INTRODUCTION — Neural injury can be an unexpected and distressing complication of an otherwise successful operation. Pain, paresthesias, loss of sensation, and weakness are the most common symptoms.

The most common causes of nerve injury during pelvic surgery are:

●Transection from incision, trocar insertion, or thermal injury from electrosurgical devices

●Entrapment from ligation for control of bleeding, tissue reapproximation (eg, closure of retroperitoneum), or reconstructive pelvic surgery (eg, vaginal or bladder suspension procedures)

●Compression or stretching of the nerve from patient positioning, retractors, clamps, or hematoma

The degree of neural injury determines whether symptoms will be reversible or permanent. The typical manifestations are motor weakness and sensory deficit in the area of the involved nerve. However, transection or ligation injuries can result in pain.

This topic will focus upon injury to abdominal and pelvic nerves. The clinical presentation and diagnosis of peripheral nerve injuries are discussed in detail separately. (See "Overview of lower extremity peripheral nerve syndromes" and "Overview of upper extremity peripheral nerve syndromes".)

ANATOMY — The most common neuropathies associated with pelvic surgery involve the femoral, ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, obturator, and pudendal nerves. Individual nerve roots from S1 to S4 may be involved with vaginal or rectal surgery.

The nerve supplies to the pelvis (figure 1), perineum (figure 2A-B), and anterior abdominal wall (figure 3) are shown in the figures. (See "Anatomy of the abdominal wall", section on 'Nerves'.)

INCIDENCE — The incidence of nerve injury following pelvic surgery is approximately 2 percent [1,2]. Neuropathies associated with pelvic surgery are more often due to the position of the patient or retractor blades than to direct operative injury (eg, electrocautery, transection) [1,3,4]. The prevalence of postoperative neuropathy depends upon a number of factors, including the type of surgical procedure, surgical approach, patient position, and length of surgery.

The lithotomy position (eg, vaginal or rectal surgery) may result in sciatic, femoral, and peroneal neuropathies. Compartment syndromes have also been reported with prolonged lithotomy positioning. Many vaginal procedures involve suspending the prolapsed vagina to structures in the pelvis. Uterosacral suspension and sacrospinous ligament suspension of the vagina may produce neuropathies of the sacral nerve roots and pudendal nerve, respectively.

One large retrospective study of 1210 women undergoing a variety of gynecologic surgeries (<1 percent laparoscopic) identified 23 postoperative neuropathies [1]. The types and frequencies of injury were obturator nerve (9/23), ilioinguinal/iliohypogastric nerve (5/23), genitofemoral nerve (4/23), femoral nerve (3/23), and lumbosacral nerve plexus (2/23).

In a prospective study of 762 patients also undergoing various gynecologic procedures, femoral and lateral femoral cutaneous nerve injuries were the most common, occurring in 10 of 14 patients; bilateral neuropathies of these nerves were seen in approximately 30 percent of cases [2].

The exact incidence of neuropathies from vaginal surgery is unknown. However, the incidence of femoral neuropathy is estimated to be 10 percent, and peroneal neuropathy is estimated to be 4 percent, when transient symptoms are included. The incidence of nerve root symptoms associated with uterosacral ligament suspension is 3.8 percent.

TRANSECTION INJURIES FROM INCISIONS — The risk of transection injury varies with the type and location of the incision. A detailed discussion of the complications of abdominal incisions can be found separately. (See "Complications of abdominal surgical incisions".)

Longitudinal incisions — Longitudinal (also called vertical) incisions are associated with a low risk of nerve injury. Longitudinal incisions lateral to the rectus muscle or in the midline between its two halves transect only the most terminal portion of the abdominal wall nerves (figure 3). Thus, any paresthesias or rectus muscle paralysis will be minor.

Even if the incision is extended above the umbilicus, widespread loss of skin sensation does not occur, because sensory dermatomes in this area overlap (figure 4). However, loss of skin sensation in the immediate proximity of the scar may occur and can be annoying. With time, areas of numbness may recover some or all sensitivity, probably due to "recruitment" of overlapping nerves.

Transverse incisions — Preliminary data suggest that chronic pain occurs in 7 percent of women following a Pfannenstiel incision, likely due to entrapment of the iliohypogastric or ilioinguinal nerves [5].

A transverse incision placed within the borders of the rectus muscles and 2 cm above the symphysis pubis results in minimal loss of neural function because the incision runs parallel to local nerves. However, dissection of the anterior rectus sheath, as required for the Pfannenstiel or Cherney incision, may injure terminal sensory nerve fibers of the anterior cutaneous branches of the iliohypogastric and ilioinguinal nerves and perforating branches of the epigastric vessels. In addition, efforts to obtain hemostasis of bleeding perforating vessels may injure the accompanying nerves. For these reasons, unnecessary transection and ligation of perforating vessels should be avoided. Injury to the terminal sensory branches of these nerves results in a small triangular area of numbness above the incision, with the apex of the triangle toward the umbilicus. The paresthesia in this area usually resolves within six months.

A transverse incision that extends beyond the lateral margin of the inferior rectus abdominis muscle fibers may injure the lateral cutaneous branches of the iliohypogastric and ilioinguinal nerves. A study on cadavers found that abdominal wall surgical sites below the level of the anterior superior iliac spine and approximately 5 cm superior to the pubic symphysis had the greatest potential for involving the ilioinguinal or iliohypogastric nerve [3]. When making a wide transverse incision, an attempt should be made to identify and avoid these nerves, which may be visible at the lateral edge of the incision.

A transverse incision that is placed too near the symphysis pubis may injure nerves that pass near the inguinal ligament and inguinal canal, such as the femoral, genitofemoral, lateral femoral cutaneous, ilioinguinal, and iliohypogastric nerves.

ENTRAPMENT INJURIES — Fascial closure and pelvic reconstructive surgery are common settings for nerve entrapment in pelvic surgery. Pain receptors, which are nonadaptive to repeated stimulation, have very low excitation thresholds when stimulated continuously, as by nerve entrapment [4]. Thus, pain is a common symptom of entrapment, in contrast to the numbness (sensory nerves) and loss of function (motor nerves) that occurs with transection. Entrapment may also result in partial or complete loss of function.

Early intervention is appropriate if entrapment is diagnosed since release of the entrapped nerve can restore normal sensory and motor function.

NEUROMA — A neuroma can form at the transected or traumatized edge of a nerve or at the site of nerve entrapment (eg, as a result of scar tissue). Neuromas are usually diagnosed several weeks to months following surgery, even though symptoms may begin early in the postoperative period. Persistent postoperative lower abdominal and groin pain should alert the surgeon to the possibility of iliohypogastric or ilioinguinal neuroma, especially following a transverse incision.

The clinical diagnosis can be made in a patient with pain and burning at the incision site, sensory impairment in the area of nerve distribution, referred pain to the groin or along the distribution of the nerve's sensory distribution, and pain elicited by percussion over the neuroma [6]. Relief of pain following nerve block supports the diagnosis, but false positives and negatives occur. (See "Anterior cutaneous nerve entrapment syndrome", section on 'Anesthetic, glucocorticoid injection'.)

Pain is often more of an issue for the patient than minor degrees of motor impairment. Pain from a neuroma may initially be managed medically with anti-inflammatory drugs and injection of local anesthetics. If these are ineffective, then excision of the affected nerve proximal to the site of the neuroma may be required [6]. Resection into the retroperitoneum and implantation of the proximal stump into muscle has been recommended to avoid recurrence of pain [6,7]. Neurolysis may be an option for treatment of nerves encased in scar tissue.

COMPRESSION INJURIES — Compression is typically caused by prolonged pressure against the nerve, usually by self-retaining retractors, prolonged positioning of the patient in stirrups, or malposition of the patient's arms. Hematomas can also cause nerve compression. The resulting neuropathy is due to ischemic injury from pressure on the vasa nervorum and is usually evident in the immediate postoperative period. Prolonged packing may also lead to compression injury.

SELECTED NEUROPATHIES

Iliohypogastric and ilioinguinal nerves — Iliohypogastric or ilioinguinal nerve injury may be caused by entrapment by sutures at the lateral poles of transverse fascial incisions for laparotomy, laparoscopic or open hernia surgery, direct trauma, or formation of a neuroma during the normal scarring/healing process. The ilioinguinal nerve seems to be at greatest risk; the iliohypogastric nerve seems to be involved less often but is often associated with ilioinguinal symptoms.

A cadaver study described the usual course of these nerves along the abdominal wall [3]:

●Ilioinguinal − 3.1 cm medial and 3.7 cm inferior to the anterior superior iliac spine to 2.7 cm lateral to the midline and 1.7 cm superior to pubic symphysis

●Iliohypogastric − 2.1 cm medial and 0.9 cm inferior to the anterior superior iliac spine to 3.7 cm lateral to the midline and 5.2 cm superior to pubic symphysis

Trauma to these nerves is characterized by a triad of symptoms [8]:

●Sharp, burning, lancinating pain radiating from the incision to the suprapubic area, labia/scrotum, or thigh

●Paresthesia over these areas

●Pain relief after infiltration with a local anesthetic

Symptoms may occur soon after surgery or months to years later. Symptoms are aggravated by stretching, coughing/sneezing, and Valsalva maneuver. Examination may reveal trigger points, which cause lancinating pain when touched. If nerve block produces complete or substantial decrease in pain, neurectomy should be considered. More than 90 percent of patients had resolution of pain after neurectomy and excision of the involved nerve. Postoperative side effects were persistent numbness below the resected nerve [9].

Femoral nerve — Deep pelvic surgery, particularly abdominal hysterectomy, is the most common setting for femoral neuropathy [10]. The usual mechanism is compression of the femoral nerve against the pelvic sidewall as the nerve emerges from the border of the psoas muscle before exiting the pelvis at the inguinal ligament. Compression is caused by very deep or lateral placement of the retractor blades during pelvic surgery [10,11].

Risk factors for femoral nerve compression include [10]:

●Wide Pfannenstiel or Maylard incision

●Thin subcutaneous fat layer (body mass index ≤20 kg/m²)

●Operating time over four hours

●Poorly developed rectus muscles

●Narrow pelvis

●Use of self-retaining retractors, especially those associated with extreme lateral traction [12]

A trial in which women undergoing hysterectomy were randomly assigned to laparotomy with and without use of self-retaining retractors showed that the risk of nerve injury was significantly higher when self-retaining retractors were used (femoral neuropathy 7.5 versus 0.7 percent) [13]. Presumably, the position of and pressure exerted by handheld retractors are more variable during the course of surgery.

Femoral neuropathy occurs in as many as 10 percent of patients who undergo laparotomy [11]. It can be associated with both sensory and motor impairment and is manifested by anesthesia of the anterior and medial thigh and weakness in the quadriceps and iliopsoas muscles. Most femoral neuropathies resolve spontaneously. If they do not, significant disability may occur since the resulting weakness of hip flexion and knee extension impedes the patient's ability to climb stairs [14].

Femoral nerve injury is less common after vaginal surgery. However, hyperflexion of the thigh can cause kinking of the nerve under the inguinal ligament, resulting in femoral neuropathy [10,11].

Despite severe proximal femoral nerve injuries that required repairs with long grafts, femoral nerve repairs resulted in good functional recovery [15].

Femoral neuropathy is discussed in detail separately. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Femoral nerve'.)

Genitofemoral and lateral femoral cutaneous nerves — The genitofemoral and lateral femoral cutaneous nerves lie on the belly of the psoas muscle, lateral to the external iliac vessels. They are at risk of compression from retractor blades, which should be elevated away from this area to protect the nerves, and at risk of transection during dissection of the external iliac lymph nodes, mobilization of the iliac vessels, or removal of a large pelvic mass adherent to the pelvic sidewall.

Injury to the genitofemoral nerve causes anesthesia or paresthesia of the labia/scrotum and upper medial thigh without motor deficits.

Injury to the lateral femoral cutaneous nerve results in paresthesias and pain that radiate down the anterior and posterior-lateral aspect of the thigh toward the knee (as in meralgia paresthetica) [16]. A substantial decrease in pain after L1 and L2 nerve blocks supports the diagnosis. Genitofemoral neurectomy should be considered since most patients get complete pain relief with anesthesia in the nerve distribution as a minor side effect [17].

If uncorrected, sensory loss in the area of the anterior and lateral thigh may occur. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Lateral femoral cutaneous nerve'.)

Obturator nerve — The obturator nerve arises from the second, third, and fourth lumbar nerve roots (figure 5). The fibers then unite posterior to the psoas muscle and pass inferiorly over the sacrum or pelvic brim to the obturator canal [18]. The obturator nerve then bifurcates into anterior and posterior divisions. Both divisions innervate the thigh adductor muscles; the anterior division provides sensory input from the hip joint and anterior medial thigh and the posterior division from the knee.

The obturator nerve may be injured with passage of a trocar through this area (eg, for placement of a transobturator tape or passage of a vascular graft) or during pelvic lymph node dissection in the obturator fossa [18]. During dissection of the obturator fossa, the obturator nerve should be identified. Procedures associated with obturator nerve injury include excision of endometriosis, paravaginal defect repair with dissection in the space of Retzius, and obturator bypass [10]. (See "Surgical management of stress urinary incontinence in females: Transobturator midurethral slings", section on 'Groin pain'.)

If unilateral obturator nerve injury occurs, numbness of the inner thigh and minor ambulatory problems will be noted due to weakened adduction of the thigh. Diagnosis of obturator nerve injury is made clinically [18]. Imaging studies do not contribute to the diagnosis. Injection of local anesthetic for a nerve block can be both diagnostic and therapeutic.

Repair of a freshly transected obturator nerve using microsurgical technique and postoperative physiotherapy often results in complete motor recovery [10]. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Obturator nerve'.)

Peroneal nerve — The most common site of injury of the common fibular nerve is just below the knee, where the nerve wraps around the lateral aspect of the fibula, immediately before dividing into its deep and superficial branches (figure 5). Excessive external pressure at this site is frequently caused by prolonged lying, such as during surgery or lengthy hospitalization. Crossing the legs, protracted squatting, and leg casts also can cause compression at this site. Stretch injuries are also possible.

The clinical presentation of common fibular neuropathy at the fibular neck is usually acute foot drop (difficulty dorsiflexing the foot against resistance or gravity). Patients describe the foot as limp; there is a tendency to trip over it unless they compensate by flexing the hip higher when walking, producing what is called a "steppage" gait. Patients may also complain of paresthesias and/or sensory loss over the dorsum of the foot and lateral shin (superficial peroneal nerve territory) [19]. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Fibular (peroneal) nerve'.)

Pudendal nerve — The pudendal nerve arises from the second, third, and fourth sacral nerve roots, exits the pelvis through the greater sciatic foramen, then reenters the pelvis via the lesser sciatic foramen to enter the pudendal canal (Alcock's canal), a fascial sheath on the medial aspect of the obturator internus muscle [20]. The nerve passes behind the lateral third of the sacrospinous ligament and posterior to the ischial spine, which is also the attachment for the arcus tendineus fasciae pelvis. At this point, it is at risk of entrapment or injury during sacrospinous ligament fixation or pelvic reconstructive procedures during which sutures are placed in the arcus tendineus fasciae pelvis.

Symptoms include perineal and vulvar/scrotal pain, which worsens in the seated position [21]. The diagnosis is made clinically; imaging and electroneuromyographic studies do not contribute to the diagnosis [22]. Diagnostic criteria have been inconsistent. A set of criteria for diagnosis has been proposed (Nantes criteria) but needs further validation [23]. These criteria are (1) pain in the area innervated by the pudendal nerve (ie, ipsilateral clitoris/penis, distal urethra, labia/scrotum, perineum, and anus), (2) pain is increased while sitting, (3) the patient is not awakened by pain, (4) no sensory loss on clinical examination (sensory deficits are suggestive of a sacral nerve root lesion), and (5) resolution of pain with administration of pudendal nerve block. (See "Pudendal and paracervical block".)

Surgical decompression is the preferred treatment and can relieve pain even two years after initial surgery [20,24,25]. Other approaches to treatment include the use of pads that avoid perineal pressure while seated, medications used for treating chronic pain, or pudendal nerve stimulation or injection with local anesthetic [21].

Isolated nerve roots S1-S4 — Injury to individual S1-4 nerve roots can give rise to neuropathic symptoms, which include postoperative sharp buttock pain and numbness that radiates down the center of the posterior thigh to the popliteal fossa.

A review of 182 uterosacral ligament suspension procedures identified seven women (3.8 percent) who manifested such symptoms within 24 hours of their surgical procedure [26]. These symptoms appear to be related to the placement of uterosacral ligament suspension sutures. Removal of the sutures produced immediate reduction of symptoms. Women may also improve with gabapentin and narcotic therapy, but 12 to 14 weeks are required to resolve the symptoms [27]. (See "Pelvic organ prolapse in women: Surgical repair of apical prolapse (uterine or vaginal vault prolapse)", section on 'Uterosacral ligament suspension'.)

Nervi erigentes — The nervi erigentes arise from the ventral rami of S2-S4 and provide parasympathetic innervation to the hindgut. Injury during pelvic surgery is thought to be due to nerve stretching from retraction, thermal damage from electrocautery, ischemia from disruption of local blood supply, or inflammation from surgical trauma [28]. Disruption of pelvic parasympathetic activity can lead to rectal, urinary, or erectile dysfunction (eg, radical prostatectomy).

Brachial plexus — The brachial plexus is formed by the ventral rami of the lower cervical and upper thoracic nerve roots. These divide into trunks, division, cords, branches, and nerves (figure 6). The brachial plexus provides cutaneous and muscular innervation to the upper extremity with the exception of the trapezius muscle and a small area of skin near the axilla (figure 7). (See "Upper extremity nerve blocks: Techniques", section on 'Innervation: Upper extremity'.)

Disruption of any portion of the brachial plexus by compression, stretching, pressure-induced ischemia, or transection can result in motor or sensory dysfunction. Specific clinical syndromes are reviewed in detail elsewhere. (See "Brachial plexus syndromes".)

DIAGNOSIS — The diagnosis of focal nerve injury in this body region is made primarily through clinical history and examination. Knowledge of peripheral nerve anatomy (figure 4) allows for a specific diagnosis to be made in most cases. Except for the femoral and obturator nerves, all of the nerves discussed above are predominantly or completely sensory in function. Most of these nerves are not accessible to routine clinical neurophysiological methods, although a well-described method exists for studying the lateral femoral cutaneous nerve. The femoral and obturator nerves are not commonly studied physiologically, and although this test is possible, it is not necessary to establish a diagnosis. Imaging studies are not useful for diagnostic purposes but serve a role in establishing etiology, such as to evaluate for the presence of a nerve compressing hematoma.

PREVENTION OF NERVE INJURY — Attention to patient position is a key factor in prevention of nerve injuries during pelvic surgery. It is also useful at the preoperative assessment to note any preexisting neurologic dysfunction (sensory and motor) or limitations to motion, especially those relating to arthritic or artificial joints. This serves as a baseline for comparison to postoperative performance status.

Avoid patient malposition — Pressure necrosis and neuropathy can occur from patient position. This is an area of medicolegal concern for the surgeon and should not be delegated to others.

Sciatic and femoral nerve injuries can result from placement of patients in the lithotomy position (figure 5). Stretching of the sciatic nerve occurs from hip flexion with knee extension or external hip rotation and knee flexion [11]. Femoral neuropathy has been attributed to nerve compression at the inguinal ligament (particularly in very thin patients) and stretching of the nerve by hip abduction and external rotation.

The following interventions help to minimize nerve trauma in the lithotomy position [11]:

●There should be minimal abduction and external hip rotation.

●The hips, lateral fibulas, posterior thighs, and heels should be padded.

●The hips and knees should be moderately flexed and securely supported.

●The weight of the lower extremities should be directed toward the soles of the feet.

●Knee stirrups should be adjusted so that tissue is not folded over metal and the stirrup edges do not cut into the calf (eg, peroneal nerve), posterior thigh, or low on the Achilles tendon.

The presence of artificial or arthritic joints may prevent optimal positioning. Symmetric placement of the legs will not always be possible in these patients.

Once the patient has been draped, further movement or positioning of the limbs should be avoided. While stirrups designed for adjustments during a procedure are available, they must be moved very carefully and the safety of the newly positioned limb confirmed before proceeding. Care must be taken to prevent hyperextension or stretching (figure 5).

Supine patients should be positioned to prevent their heels and arms from contacting hard surfaces. The risk of compression injuries can be minimized by padding the area between the elbow and arm board and the area under the heels.

If the arms are placed adjacent to the body, care should be taken to ensure that the fingers do not overlap or lie within movable table sections (amputation can occur). The position of the arm should be secure; serious soft tissue and bony injury can occur if an improperly supported arm falls or the surgeon inadvertently leans against an arm and pushes it into hyperextension. For this reason, tucking one or both of the arms against the patient's side is advisable.

If the arms are placed at an angle to the body, the upper extremities should not extend more than 90º from the woman's side. Brachial plexus injury can result from hyperextension and is more likely during laparoscopy but can occur during laparotomy. Shoulder restraints can also cause compression of the brachial plexus if the patient is placed in deep Trendelenburg; this may be avoided by placing the restraints laterally on the acromioclavicular joint [29]. (See "Overview of upper extremity peripheral nerve syndromes", section on 'Brachial plexopathy' and "Overview of upper extremity peripheral nerve syndromes", section on 'Ulnar nerve syndromes'.)

Avoid prolonged lithotomy position — The risk of peroneal or tibial nerve injury or the development of a compartment syndrome increases when patients are in the lithotomy position for more than four hours. For procedures extending beyond four hours, the surgical team should consider repositioning the patient into a supine position for 20 to 30 minutes to try to avoid these complications [30]. The patient can then be placed back in the lithotomy position, if necessary.

Peroneal nerve injury is characterized by foot drop, instability in dorsiflexion and inversion of the foot, and numbness of the lateral leg and dorsum of the foot (see 'Peroneal nerve' above). Signs of tibial nerve injury consist of difficulty with plantar flexion and toe extension and sensory loss at the back of the leg and sole of the foot.

Clinical manifestations of a developing compartment syndrome consist of pain disproportionate to findings on physical examination and weakness and hypesthesia of the foot and/or leg and possibly reduced pedal pulses. Compartment syndrome is a surgical emergency. Prompt consultation with a qualified surgeon (general, vascular, orthopedic) is important because delayed treatment can lead to permanent sensory or motor loss and, in serious cases, tissue loss [31]. (See "Acute compartment syndrome of the extremities".)

Avoid extreme Trendelenburg position — Brachial plexus injury is among the top three causes of peripheral neurapraxia associated with pelvic surgery under general anesthesia. Case reports implicate steep Trendelenburg position as a risk factor for brachial plexus injury. Steep Trendelenburg (30 to 45º) is most often needed during robotic-assisted laparoscopic pelvic surgery (eg, prostatectomy, hysterectomy).

Shoulder braces are typically used during patient positioning in steep Trendelenburg to keep the patient from sliding from the table. Care should be taken not to place them too medial, which can cause direct compression of nerve roots C5 and C6, or too lateral, which can cause stretching of the divisions of the plexus [32].

A gel-padded sheet, spanning the length of the patient's body, with a head support, can be used to reduce the risk of brachial plexus injury associated with prolonged steep Trendelenburg position. Alternatively, ankle cuffs can be used to prevent patient movement [33].

When brachial plexus injury occurs, management is largely conservative. Electromyography may be needed to provide specific information on the site of injury [34]. The management of brachial plexus palsies is discussed in detail elsewhere. (See "Brachial plexus syndromes".)

Attention to the surgical incision — The following techniques can reduce the risk of nerve injury during laparotomy:

●Use of a midline longitudinal incision is less likely to disturb abdominal nerves than a transverse incision. However, all of the advantages and disadvantages of longitudinal incisions need to be considered when choosing an incision for an individual patient. (See "Incisions for open abdominal surgery".)

●A short transverse incision placed within the borders of the rectus muscles and 3 cm above the symphysis pubis results in minimal loss of neural function. If it is necessary to extend the incision, curving it cephalad, rather than continuing in a straight line, may help avoid injuring the iliohypogastric and ilioinguinal nerves [10].

●Avoiding use of cautery on the perforating branches of vessels helps to avoid injury to the terminal sensory nerve fibers, which typically run alongside these vessels. Severe nerve injuries have also resulted from extensive use of cautery on the posterior lateral pelvic side wall.

●Some surgeons recommend suturing only the external oblique aponeurosis to prevent nerve injury; however, wide, deep sutures during closure may still entrap nerves.

During laparoscopy, avoidance of port-site incisions below the anterior superior iliac spine will avoid injury to the ilioinguinal and iliohypogastric nerves. (See 'Iliohypogastric and ilioinguinal nerves' above.)

Attention to retractors — Lateral retractor blades should not compress the psoas muscle. Use of the shortest blade that effectively retracts the abdominal wall minimizes the risk of this complication. In thin patients, rolled laparotomy packs placed between the retractor and the anterior abdominal wall can be helpful. If possible, avoiding an extended transverse incision is also useful because it precludes positioning the retractor very far laterally. Blade position should be inspected upon placement and reinspected periodically during long cases, with relief of pressure, especially if a self-retaining retractor is being used. (See 'Femoral nerve' above.)

Other — The surgeon and assistants should not lean or place heavy objects on the patient, as these actions may cause a compression or stretch injury. As an example, when the patient is in the lithotomy position for vaginal surgery, leaning against the patient's leg could cause excessive external rotation of the hip, leading to sciatic nerve injury.

TREATMENT — Conservative therapy is warranted in most cases. Most stretch injuries will resolve spontaneously with proper supportive care, and many entrapment injuries will resolve if the offending suture is rapidly absorbed. If nerve compression due to suture misplacement or hematoma can be identified, correction may be curative. If the surgeon immediately recognizes a transaction, direct end-to-end repair should be considered by an appropriate specialist. However, unless repair is immediate, functional recovery of purely sensory nerves is quite poor, and symptomatic treatment is indicated instead. Compressive neuropathies, whether or not axon loss has occurred, are also best treated by watchful waiting.

A variety of medications have been used to treat pain related to sensory nerve lesions. These include tricyclic antidepressants, and anticonvulsants. Both GABA antagonists and serotonin and norepinephrine specific reuptake inhibitors are effective in patients with painful generalized neuropathies and may be effective in focal lesions as well.

Patients with compression or stretch-related injuries from retraction or operative position can benefit from physiotherapy and avoiding positions that worsen nerve compression [11].

SUMMARY AND RECOMMENDATIONS

●Nerve injury associated with pelvic surgery – Entrapment, compression, transection, or stretching of nerves can result in postoperative neuropathy. The most common neuropathies associated with pelvic surgery involve the femoral, ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, obturator, and pudendal nerves. (See 'Introduction' above and 'Anatomy' above.)

●Transection injury – The risk of transection injury varies with the type and location of the incision.

•Longitudinal (also called vertical) incisions are associated with a low risk of nerve injury. (See 'Longitudinal incisions' above.)

•Transverse incisions that extend beyond the rectus abdominis, involve extensive dissection of the anterior rectus sheath, or are too near the symphysis pubis are more likely to result in neuropathy. (See 'Transverse incisions' above.)

●Iliohypogastric and ilioinguinal nerve injury – Injury of iliohypogastric or ilioinguinal nerves may occur from entrapment of the nerves by sutures at the lateral poles of transverse fascial incisions, direct nerve trauma, neuroma formation, or from neural constriction caused by the normal scarring/healing process. The characteristic triad of symptoms is (1) sharp, burning, lancinating pain radiating from the incision to the suprapubic area, labia/scrotum, or thigh, (2) paresthesia over these areas, and (3) pain relief after infiltration with a local anesthetic. (See 'Iliohypogastric and ilioinguinal nerves' above.)

●Femoral nerve injury – Pelvic surgery, especially hysterectomy, is the most common cause of iatrogenic femoral neuropathy. It results from excessive deep or lateral placement of the retractor blades during abdominal surgery or faulty patient positioning during vaginal surgery. Thin patients and those with a narrow pelvis or poorly developed rectus abdominis are at increased risk. (See 'Femoral nerve' above.)

●Neuroma – A neuroma should be suspected in a patient with pain and burning at the incision site, sensory impairment in the area of nerve distribution, referred pain to the groin or along the distribution of the nerve's sensory distribution, and pain elicited by percussion over the neuroma. (See 'Neuroma' above.)

●Genitofemoral and lateral femoral cutaneous nerve injury – Injury to the genitofemoral nerve results in anesthesia or paresthesia of the labia majora/scrotum and upper medial thigh, without motor deficits. Injury to the lateral femoral cutaneous nerve results in paresthesias and pain that radiate down the anterior and posterior-lateral aspect of the thigh toward the knee. If uncorrected, sensory loss in the area of the anterior and lateral thigh may occur. (See 'Genitofemoral and lateral femoral cutaneous nerves' above.)

●Prevention – We suggest the following interventions to minimize the risk of nerve injury during pelvic surgery:

•Avoid hyperextension and flexion when positioning the patient, and use padding to minimize compression (Grade 2C). (See 'Avoid patient malposition' above.)

•Avoid lateral extension of transverse incisions beyond the border of the rectus muscles (Grade 2C). When additional room is needed, curve the incision cephalad. (See 'Attention to the surgical incision' above.)

•Retractors should not compress the psoas muscle. Use of short blades or placement of a laparotomy pack between the blade and abdominal wall reduce the risk of femoral nerve compression. In addition, the blades should be reinspected periodically during long cases, with periodic relief of pressure, especially when self-retaining devices are being used (Grade 2C). (See 'Attention to retractors' above.)

•Identify the obturator nerve when performing extensive dissection in the obturator fossa, and confirm its integrity after surgery in this area (Grade 2C). (See 'Obturator nerve' above.)