1mon.qxd 2/2/04 10:26 AM Page 73 REVIEW Current Overview of Neurovascular Structures in Hip Arthroplasty: Anatomy, Preoperative Evaluation, Approaches, and Operative Techniques to Avoid Complications John-Paul H. Rue, MD* Nozomu Inoue, MD, PhD* Michael A. Mont, MD† A major neurovascular injury during total hip arthroplasty (THA) is uncom- Educational Objectives mon. Nevertheless, these are worri- some due to their devastating conse- As a result of reading this article, physicians should be able to: quences. As more THAs are performed 1. Identify the bony, vascular, and neural anatomy that is relevant to the each year, the chances of this potential- surgeon performing total hip arthroplasty. ly life- or limb-threatening injury 2. Describe the common approaches to avoid neurovascular complica- increase.1 It is crucial for the orthope- tions. dic surgeon to have a thorough under- 3. Discuss the appropriate clinical work-up of these patients. standing of the anatomy of the region 4. Describe the various neurovascular complications and how to handle and the potential complications. them. This article reviews the exposures to the acetabulum for simple and complex primary THA, as well as revision cases, with particular attention to the neu- ischium, and pubis (Figure 1). The Damage to any of these vessels by rovascular anatomy of the region. acetabulum is located at the junction of retraction, drilling, reaming, or dissec- these three bones. These bones unite tion can cause massive hemorrhage, ANATOMY anteriorly at the pubic symphysis and which can lead to exsanguination with- Bone posteriorly to the sacrum to form a ring in minutes. The three-dimensional pelvic anato- of bone, which connects the torso to the The common iliac artery divides at my is complex and often hard to under- lower limbs. the L5-S1 vertebral disk. The anterior stand. Several vital vascular and viscer- division, the external iliac artery, con- al structures are contained within and Vascular Structures tinues distally to become the common immediately around the bony pelvis. The proximity of the major vessels femoral artery, whereas the posterior The bony pelvis is formed by the ilium, to bone, and therefore their risk for division becomes the internal iliac injury during acetabular surgery, artery. The internal iliac artery branch- varies. Knowledge of vessel location is es again into a posterior division, From the *Department of Orthopedic Surgery, The Johns Hopkins Medical Institutions, and important because extensive exposure which gives rise to the superior gluteal †Sinai Hospital of Baltimore, Center for Joint of the acetabulum may be required for artery, and an anterior division, which Preservation & Reconstruction, Baltimore, Md. complex revision THA. gives off the obturator artery before Drs Rue, Inoue, and Mont have not declared The major vascular structures locat- dividing into the inferior gluteal artery any industry relationships. ed within and around the pelvis are the and internal pudendal artery. Reprint requests: Michael A. Mont, MD, Sinai Hospital of Baltimore, Center for Joint internal and external iliac, femoral, The external iliac artery and vein are Preservation & Reconstruction, 2401 W Belvedere internal pudendal, obturator, and supe- immobile and lie close to the pelvis, Ave, Baltimore, MD 21215. rior and inferior gluteal vessels. and thus are at highest risk for injury in www.orthobluejournal.com 73 1mon.qxd 2/2/04 10:26 AM Page 74 ORTHOPEDICS JANUARY 2004 VOL 27 NO 1 1 2 Figure 1: Schematic showing the intrapelvic bony anatomy of the acetabular region. Abbreviation: ASIS=anterior superior iliac spine. Figure 2: Schematic showing the excessively long screws on the quadrilateral intrapelvic surface relative to the iliac arterial system. (Reprinted with permission from Wasielewski RC et al. Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am. 1990; 72:501-508. Copyright © 1990. The Journal of Bone and Joint Surgery Inc.) THA (Figure 2). The external iliac vein 6 mm and the pudendal vessels an aver- interval between the gluteus medius has been shown to lie within 7 mm of age of 12 mm from the posterior col- and minimus muscles. It is generally the anterior column of the pelvis at the umn. Both, however, are mobile and well protected as long as the dissec- anterior inferior iliac spine and within well protected by a layer of fat.3,4 The tion does not extend Ͼ5 cm above the 4 mm at the acetabular dome. The medial and lateral femoral circumflex greater trochanter.5 The inferior external iliac artery is at less risk due to arteries arise from the deep femoral gluteal nerve is rarely injured because its thicker intima and increased dis- artery and are vulnerable to retractors it inserts into the gluteus maximus tance from the bone. It lies within 10 placed near the femoral neck. proximal and medial to the area, mm of the bone at the anterior inferior which is split during the posterior iliac spine and within 7 mm at the Neuroanatomy approach to the acetabulum. The obtu- acetabular dome. The common femoral The primary nerves of the region are rator nerve runs with the obturator artery lies anterior and medial to the the sciatic, femoral, inferior and superi- vessels.6 hip capsule. Only the iliopsoas lies or gluteal, and obturator. The most The most common nerve injury dur- between the vessel and capsule at this common nerve injury during THA is to ing THA is to the sciatic nerve.7 point. The femoral vein lies medial to the peroneal division of the sciatic Several reasons exist, some of which the artery and is thus less likely to be nerve, followed by superior gluteal, remain conjectural. It has been postu- injured. The obturator vessels also are obturator, and femoral nerves. Injury to lated that these are common because of at risk, lying fixed within 1 mm of the these structures can lead to loss of the sciatic nerve anatomic location. In bony surface at the quadrilateral sur- function and poor outcomes. a review of normal computed tomogra- face, with their only protection being The femoral nerve is the most later- phy (CT), the sciatic nerve was found the interposition of the obturator inter- al structure within the femoral trian- to lie closest to the posterior column of nus muscle. gle. It lies on the psoas muscle belly at the pelvis at the acetabular dome, at an At the sciatic notch, the superior the approximate midpoint between the average of 9 mm. It also was shown to gluteal vessels are at greatest risk, lying anterior superior iliac spine and pubic be more protected at the ischial spine, an average of 5 mm from the notch. tubercle. Its relationship to the acetab- as the short external rotator muscles Injury to the superior gluteal artery as a ulum is anterior, thus it is primarily at are interposed between the nerve and complication of THA is rare, but has risk during capsule dissection rather bone at this point; the nerve was an been reported.2 At the ischial spine, the than during reaming or drilling. The average 15 mm away from the ischial inferior gluteal vessels lie an average of superior gluteal nerve traverses the spine.3 74 www.orthobluejournal.com 1mon.qxd 2/2/04 10:26 AM Page 75 RUE ET AL REVIEW 3 4 Figure 3: The acetabular quadrant system. The quadrants are formed by the intersection of lines A and B. Line A extends from the anterior superior iliac spine through the center of the acetabulum to the posterior aspect of the fovea, dividing the acetabulum in half. Line B is drawn perpendicular to line A at the mid-point of the acetabulum, dividing it into four quadrants: anterior-superior, anterior-inferior, posterior- superior, and posterior-inferior. Abbreviation: ASIS=anterior superior iliac spine. (Reprinted with permission from Wasielewski RC et al. Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am. 1990; 72:501-508. Copyright © 1990. The Journal of Bone and Joint Surgery Inc.) Figure 4: External view of intrapelvic vessels in the quadrilateral region with superimposed acetabular quadrant system as described by Wasielewski RC et al.3 Quadrant System bone and close proximity of the vessels of the posterior wall. It is the most com- The acetabular quadrant system to bone in that region (Figure 4). monly used approach for THA in the described by Wasielewski et al3 is use- United States. The patient is placed in ful for determining the location of APPROACHES the lateral position. Because the planned acetabular screw fixation in The anterolateral and posterior approach involves splitting of the glu- THA to avoid neurovascular complica- approaches are the most common sur- teus maximus in line with its fibers, no tions. The quadrants are formed by gical approaches to the acetabulum internervous plane is present. The sci- drawing a line from the anterior superi- during THA. Both approaches offer atic nerve is protected by the short or iliac spine through the center of the excellent visualization of the acetabu- external rotators after they are detached acetabulum and bisecting that line at lum. Comparing lateral- and posterior- from their insertions on the femur and the center of the acetabulum to form oriented approaches, lateral approaches reflected medially (Figure 5). four equal quadrants. The line from the offer better exposure, although posterior Damage to the inferior gluteal artery anterior superior iliac spine to the cen- approaches are more popular. The ilioin- is the main vascular risk of the posteri- ter of the acetabulum serves as the guinal and anterior (extended ilio- or approach. This vessel has many dividing line between anterior and pos- femoral) approach are described as intramuscular branches, which often terior, and the bisecting line as the divi- these approaches are often used for are cut when the gluteus maximus is sion between superior and inferior more extended exposures.5 In general, split, and they must be identified and (Figure 3).