A Review Paper Neurologic Injuries After Total Hip Arthroplasty Gabriel D. Brown, MD, Eli A. Swanson, MD, and Ohannes A. Nercessian, MD preservation of the connective-tissue elements of the Abstract nerve. Neurotmesis is complete disruption of the nerve Neurologic injuries are a potentially devastating com- resulting in permanent loss of function in the absence of plication of total hip arthroplasty (THA). Review of operative repair.19 the literature reveals that these injuries are uncom- mon. The reported incidence ranges from 0.08% to NATOMY 7.6%. The incidence in primary THA ranges from A 0.09% to 3.7% and in revision THA from 0% to 7.6%. Sciatic Nerve Reported etiologies include intraoperative direct The sciatic nerve arises from nerve roots L4 to S3 and is 20 nerve injury, significant leg lengthening, improp- composed of the peroneal and tibial divisions. These er retractor placement, cement extravasation, divisions typically travel together in a single sheath.21 cement-related thermal damage, patient position- The sciatic nerve exits the pelvis inferior to the piriformis ing, manipulation, and postoperative hematoma. muscle. It travels superficial to the external rotators and Risk factors include developmental dysplasia of the deep to the gluteus maximus muscle at the level of the hip, the female sex, posttraumatic arthritis, and revision hip joint. Distal to the ischial tuberosity, it courses medial surgery. However, no single risk factor has been consis- to the gluteal sling between the long head of the biceps tently reported to be significant, and many patients with femoris and the adductor magnus muscles. Branches from no known risk factors incur neurologic injuries. the tibial division innervate the hamstring muscles, except for the short head of the biceps, which is innervated by the evelopment of a peripheral nerve palsy after total hip arthroplasty (THA) is an uncommon but potentially devastating complication. The “Edwards and colleagues38 incidence in primary THA ranges from 0.09% to D3.7% and in revision THA from 0% to 7.6%1-17 (Table). reported that leg lengthening An understanding of this complication remains elusive. is a significant risk factor for Identification of patients at increased risk, and meticulous operative technique, can reduce the occurrence of this neurologic injury [of the frustrating complication. sciatic nerve].” Seddon18 categorized the extent of peripheral nerve injury on the basis of degree of anatomical and functional peroneal division. This is the only muscle innervated by disruption. Neuropraxia is local myelin damage with pre- the peroneal division above the level of the knee. At the served axon continuity, usually secondary to compression. level of the popliteal fossa, the sciatic nerve divides into Axonotmesis is loss of continuity of axons with variable the tibial and common peroneal nerves. The common peroneal nerve innervates the anterior and lateral compartments of the leg through the deep Dr. Brown is Senior Resident, Department of Orthopaedic and superficial peroneal nerves, respectively. The deep Surgery, New York Orthopaedic Hospital, Columbia University Medical Center, New York, New York. peroneal nerve innervates the tibialis anterior, extensor Dr. Swanson is Junior Resident, Department of Orthopaedic digitorum longus, extensor hallucis longus, and peroneus Surgery, Harbor UCLA Medical Center, Los Angeles, California. tertius muscles. The sensory branch innervates the inter- Dr. Nercessian is Associate Professor, Center for Hip and Knee space between the first and second toes. The superficial Replacement, Department of Orthopaedic Surgery, New York peroneal nerve innervates the peroneus longus and brevis Orthopaedic Hospital, Columbia University Medical Center, New York, New York. muscles. The sensory branches innervate the dorsum of the foot. The tibial nerve innervates the superficial and Address correspondence to: Gabriel D. Brown, MD, Department deep posterior compartment muscles and terminates as the of Orthopaedic Surgery, Columbia University Medical Center, medial and lateral plantar nerves. The tibial division of the 622 W 168th St, PH 11-1130, New York, NY 10032 (tel, 212-305- sciatic nerve is larger than the peroneal division and runs 5974; fax, 212-305-6193; e-mail, [email protected]). posterior to that division at the level of the hip. The nerve Am J Orthop. 2008;37(4):191-197. Copyright Quadrant HealthCom gradually rotates until the tibial division runs medial to Inc. 2008. All rights reserved. the peroneal division at the posterior aspect of the thigh. April 2008 191 Neurologic Injuries After Total Hip Arthroplasty Table. Incidence of Reported Nerve Palsies in Primary and Revision Total Hip Arthroplastya No. of No. of Palsies No. of No. of Palsies in No. of Total No. of Primary in Primary Revision Revision Study Patients Palsies (%) Cases Cases (%) Cases (%) Cases (%) Amstutz & colleagues1 88 6 (7.6%) — — 88 6 (7.6%) Beckenbaugh & Ilstrup2 300 4 (1.3%) 253 — 47 — Buchholz & Noack3 3948 75 (1.9%) 3855 — 93 — Eftekhar & Stinchfield4 700 9 (1.3%) 556 — 144 — Farrell & colleagues5 27,004 47 (0.17%) 27,004 47 (0.17%) — — Johanson & colleagues6 5667 34 (0.6%) — — — — Lazansky7 501 3 (0.6%) 403 — 98 — Lubinus8 1350 28 (2.1%) — — — — Moczynski & colleagues9 237 4 (1.3%) 155 — 82 — Murray10 808 15 (1.9%) 557 10 (1.8%) 251 5 (2.0%) Navarro & colleagues11 1000 8 (0.8%) 630 3 (0.5%) 370 5 (1.4%) Nercessian & colleagues12 7133 45 (0.5%) — — — — Nercessian & colleagues13 1287 1 (0.08%) 1152 1 (0.09%) 135 0 (0%) Robinson & colleagues14 316 2 (0.63%) — — — — Schmalzried & colleagues15 2355 43 (1.8%) 1661 21 (1.3%) 694 22 (3.2%) Weber & colleagues16 2012 14 (0.7%) 2012 14 (0.7%) — — Wilson & Scales17 108 4 (3.7%) 108 4 (3.7%) — — aDash (—) indicates data not available. These divisions do not exchange any neural tissue, which the pelvis through the obturator canal at the superolateral aspect accounts for the numerous anatomical variants noted in of the obturator foramen. The obturator nerve innervates the the literature. adductor muscles and provides sensory innervation to a small The reported incidence of anatomical variation in the sci- region on the medial aspect of the thigh. Along its course, it atic nerve is 15% to 30%.20,22-24 Pokorny and colleagues25 traverses the quadrilateral surface of the acetabulum. found an atypical anatomical relationship between the sci- atic nerve and the piriformis muscle in 20.9% of cadaveric Superior Gluteal Nerve dissections. The most common variation was division of The superior gluteal nerve arises from nerve roots L4 to the sciatic nerve into tibial and peroneal nerves above the S1, exits the pelvis through the greater sciatic notch, and piriformis muscle, with one branch traveling through and the innervates the tensor fascia lata, gluteus minimus, and other superior to the muscle. gluteus medius muscles. It travels with the superior gluteal The common peroneal division is injured more often artery deep to the gluteus maximus and medius but super- than the tibial division is, because of the distal tether- ficial to the minimus. There is a 3- to 5-cm “safe zone” ing of the terminal branches15 and the superficial fibular proximal to the greater trochanter.30,31 The superior gluteal arcade at the level of the knee. In addition, the peroneal nerve travels with the sciatic nerve opposite the posterior division is more vulnerable to compression because of superior acetabular quadrant. The acetabular thickness is fewer but larger-caliber nerve bundles with less inter- 25 mm or more in this region, permitting safe placement posed connective tissue. The result is more tightly packed of screws.32 fascicles, in comparison with the tibial division, which has smaller-caliber bundles with abundant connective INJURY INCIDENCE tissue.26-28 Finally, in accord with Laplace’s law,29 the Sciatic Nerve larger-caliber nerve bundles of the peroneal division are The reported incidence of sciatic nerve palsy associ- at higher risk for compression. ated with THA ranges from 0.05% to 1.9%.5,9-17,33 In a series of 27,000 cases of primary THA, Farrell and Femoral Nerve colleagues5 reported a 0.05% incidence of sciatic nerve The femoral nerve arises from nerve roots L2 to L4, passes palsy. Murray10 reported an incidence of 0.1% in 808 through the psoas muscle, and then runs between the iliacus cases, with the event occurring in a revision case, while and psoas muscles. It enters the thigh as the most lateral struc- Navarro and colleagues11 reported an incidence of 0.1% ture in the femoral triangle. The femoral nerve innervates the in 1000 cases, with the event occurring in a primary case. quadriceps mechanism and provides sensory innervation to Nercessian and colleagues12 evaluated 7133 patients and the anteromedial aspect of the thigh and calf. reported a sciatic nerve palsy rate of 0.08%, with 1 case occurring in a revision procedure and 5 cases occurring Obturator Nerve in primary procedures. Schmalzried and colleagues15 The obturator nerve arises from nerve roots L2 to L4, runs reported an incidence of 1.5% in 2355 primary and revi- within the posterior aspect of the psoas muscle, and emerges at sion cases, and Wilson and Scales17 reported an incidence the sacral ala. It continues along the iliopectineal line and exits of 1.9% in 108 primary cases. Hurd and colleagues34 192 The American Journal of Orthopedics® G. D Brown et al reported no cases of sciatic nerve injury in 752 patients in Weber and colleagues16 in their series of 2012 cases report- whom the gluteus maximus insertion was released, com- ed 1 incident of obturator nerve injury, in a primary case. pared with 3 (0.4%) of 804 patients in whom the gluteus maximus tendon was left intact. Weber and colleagues16 Superior Gluteal Nerve prospectively evaluated 30 THA cases, 70% of which To our knowledge, no cases of injury to the superior glu- showed electromyographic (EMG) evidence of neuro- teal nerve have been reported in the literature.