Overview on Pelvic Resections: Surgical Considerations and Classifications

Transcription

1 13282_ON-17.qxd 3/22/09 10:45 AM Page 1 Chapter 17 Overview on Pelvic Resections: Surgical Considerations and Classifications Ernest U. Conrad III, Jason Weisstein, Jennifer Lisle, Amir Sternheim, and Martin M. Malawer BACKGROUND The pelvis is a relatively common anatomic location for metastatic and primary musculoskeletal tumors. Surgical resection is more challenging in the pelvis than in other locations because of the complex anatomy and the proximity to vital abdominal viscera and major blood vessels and nerves. Making decisions about surgical resectability of a tumor involves the assessment of possible osseous or neurovascular involvement, in addition to the possible involvement of adjacent viscera (ie, bowel, ureter, and bladder). Therefore, preoperative evaluation and extensive imaging are critical. Osseous resection and reconstruction usually are carried out adjacent to major nerves, beneath the iliac vessels, or adjacent to the bladder or bowel. Tumor surgery around the pelvis has the highest rate of complications, infections, and mechanical failure of all anatomic sites. ANATOMY (FIG 1) Pelvic Nerves Sciatic Nerve The sciatic nerve arises from L4, L5, S1, S2, and S3. The nerve emerges from the pelvis through the greater sciatic notch inferior to the piriformis muscle and enters the thigh lateral to the ischial tuberosity. In 10% of patients, the sciatic nerve penetrates the substance of the piriformis muscle. The sciatic nerve is accompanied by the inferior gluteal artery. It is essential to protect the sciatic nerve early in most procedures. Inside the pelvis, the nerve should be identified distally at the greater sciatic notch. Proximally, it should be picked up below the psoas muscle. The sciatic nerve is formed at the junction of the lumbar sacral plexus where these two trunks come together. Great care must be taken as the nerve exits the pelvis at the level of the greater sciatic notch not to injure the the accompanying inferior and superior gluteal nerves and arteries, because these supply the abductors as well as the gluteus maximus muscle. The gluteus maximus muscle is essential for closure of most pelvic resections. Femoral Nerve The femoral nerve arises from posterior divisions of the ventral rami of L2 and L3 and passes inferolaterally between the psoas and iliacus muscles. It passes over the superficial iliacus muscle to enter the proximal thigh underneath the inguinal ligament, just lateral to the superficial femoral artery. This nerve is almost always preserved during pelvic resections. It should be identified early during most procedures. The femoral nerve is identified in the space between the iliacus and psoas muscles as they exit the pelvis. The femoral nerve lies just below the fascia, bridging the interval between the two muscles, lateral to the femoral artery and vein. Obturator Nerve The obturator nerve, formed from the anterior branches of L2, L3, and L4, is the largest nerve formed from anterior divisions of the lumbar plexus. The nerve descends thru the iliopsoas muscle and courses distally over the sacral ala into the lesser pelvis, lying lateral to the ureter and under the internal iliac vessels. It then traverses the obturator foramen into the medial thigh, under the superior pubic ramus, dividing into anterior and posterior branches. This nerve is routinely transected during pelvic floor resections (type 3) due to its intimate proximity to the tumor. Lumbar Plexus Sensory Nerves The iliohypogastric (L1), ilioinguinal (L1), genitofemoral (L1, 2) and lateral femoral cutaneous nerves, which arises from L2 and L3, travel downward laterally along the iliopsoas muscle, pass underneath the lateral aspect of the inguinal ligament, and pass just distal and medial to the anterior superior iliac crest to innervate the anterolateral thigh. This nerve is sacrificed during most pelvic surgical procedures. Pelvic Vessels Aortic Bifurcation Descending the abdomen to the left of the vena cava, the aorta bifurcates at the level of L4 into common iliac vessels at the level of L4 L5. The common iliac bifurcates into internal and external iliacus vessels at the level of S1, the ala sacralis. The level of these bifurcations may vary, especially if the vessels are pushed by a large adjacent tumor mass. It is essential to identify two levels of bifurcations prior to any ligation: the aortic bifurcation and the common iliac bifurcation. Even the best surgeons have ligated the wrong vessels due to distorted anatomy. Such a misstep is especially possible with tumors that cross the midline. Preoperative evaluation with angiography is required for evaluation and preoperative to avert such an occurrence. Common Iliac Artery The common iliac artery must be identified early to correctly identify the aorta as well as the the internal iliac (hypogastric) artery. To the surgeon, the major anatomic features of the common iliac artery are as follows: No arterial branches arise from the artery (although the common iliac vein does have a major branch joining in, the iliolumbar vein) The bifurcation of the common iliac artery into the external and internal iliac arteries is at the exact level at which the ureter crosses on the adjacent peritoneal surface. The ureter is routinely identified at this location early in the retroperitoneal dissection. External Iliac Artery The external iliac artery contributes to the inferior epigastric artery and extends distally, as the superficial femoral artery, 1

2 13282_ON-17.qxd 3/22/09 10:45 AM Page 2 2 Part 4 ONCOLOGY Section III SPINE AND PELVIS Ureter The ureter originates from the renal pelvis at the level of L1 and courses in the retroperitoneum to the medial surface of the psoas major muscle, crossed by spermatic or ovarian vessels. The ureter crosses from lateral to medial on the surface of the peritoneum at the level of the common iliac bifurcation. This is a good landmark to identify the ureter during the initial retroperitoneal dissection. The ureter then courses medially at the level of the sciatic notch to insert into the trigone of the bladder. Corona Mortis The corona mortis is an anastomosis of the external iliac, inferior epigastric, and obturator vessels located in the retropubic region approximately 3 cm from the symphysis pubis. Laceration during an ilioinguinal approach can lead to extensive bleeding. The retroperitoneal space between pubis and bladder is called the space of Retzius. FIG 1 The bony pelvis and its relation to the major blood vessels, nerves, and visceral organs. (Courtesy of Martin M. Malawer.) into the femoral triangle, where it is a useful landmark in identifying neighboring structures. Internal Iliac Artery The internal iliac (hypogastric) artery descends from the lumbosacral articulation to the greater sciatic notch and branches into several arteries. The internal iliac artery and vein often are difficult to identify or ligate. The internal iliac artery lies on top of its vein, which often is large and is easily injured. The hypogastric vessels are routinely ligated in performing modified hemipelvectomies as well as many pelvic resections. ANTERIOR BRANCHES The obturator artery exits the pelvis via the obturator canal (beneath the superior pubic ramus). The inferior gluteal artery curves posteriorly between the first and second or second and third sacral nerves, then runs between the piriformis and coccygeus muscles or through the greater sciatic foramen into the gluteal region below the piriformis muscle. POSTERIOR BRANCHES The iliolumbar artery ascends posterior to the obturator nerve and external iliac vessels to the medial border of the psoas. It then divides into the lumbar branch, to the psoas and quadratus lumborum muscles and to the spinal cord, and an iliac branch, to the iliac, gluteal, and abdominal musculature. The iliac branch often is ligated during surgery. The superior gluteal artery runs posteriorly between the lumbosacral trunk and first sacral nerve and leaves the pelvis through the greater sciatic foramen superior and posterior to the piriformis muscle. Great care must be taken to preserve the gluteal vessels and nerves when performing types 1 and 2 pelvic resections. Inguinal Canal The anatomic confines of the inguinal canal are described as 4 cm from the deep inguinal ring to the subcutaneous ring. This deep ring is the direct inguinal space originating lateral to the epigastric vessels. Hesselbach s triangle is the indirect hernia space originating medial to the epigastric vessels. The inguinal contents vary by gender: In males, the spermatic cord contains the ductus deferens, testicular artery, pampiniform plexus, lymphatics, autonomic nerves, the ilioinguinal and genital branches of the genitofemoral nerve, the cremasteric artery and muscle, and the internal spermatic fascia. In females, the inguinal contents include the round ligament and the ilioinguinal nerve. The anterior inguinal wall is formed by the aponeurosis of the external oblique and internal oblique (lateral) muscles. The posterior inguinal wall runs medial to lateral and is formed by the reflected inguinal ligament, the inguinal falx, and the tranversalis fascia. The superior or cephalic inguinal wall is formed by arched fibers of the internal oblique muscle and the transverse muscle of the abdomen. The inferior or caudal inguinal wall is formed by the inguinal and lacunar ligaments. Boundaries Sciatic Notch The sciatic notch should be identified early in surgery, both internally and externally, to protect the sciatic nerve and gluteal pedicles. Osseous Boundaries The superior cephalad margin of the pelvis is defined by the ilium and the rim of the great sciatic notch. Posterior Margin The posterior margin of the pelvis is bounded by the piriformis muscle and the superior gluteal vessels and nerve. Posterior to the piriformis muscle, the internal pudendal vessels and nerve course medially off the sciatic nerve and the posterior femoral cutaneous nerve, anterior to the piriformis.

3 13282_ON-17.qxd 3/22/09 10:45 AM Page 3 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 3 Inferior Margin The sacrospinous and sactrotuberous ligaments are released during type 1 and 2 pelvic resections. INDICATIONS Recurrent Benign Tumors Major pelvic resections rarely are performed for benign bony tumors. Occasionally, following multiple recurrence or when tumors are limited to either the superior or inferior pubic rami, pelvic resection is indicated. Such benign tumors include large osteochondromas or any osteochondroma associated with multiple hereditary exostosis, due to the high risk of secondary chondrosarcoma. Osteoblastoma occuring in the ilium or periacetabulum Giant cell tumors or aneurysmal bone cysts have a predilection for the superior pubic ramus and supra-acetabulum. Primary Malignant Osseous Tumors Osteosarcoma Five percent of all osteosarcomas occur in the pelvis. Partial pelvic resection or hemipelvectomy (amputation) is required, usually following induction chemotherapy. Ewing sarcoma About 25% of all Ewing sarcomas occur in the pelvis. Surgical resection is required. Radiation therapy remains controversial in treating pelvic Ewing sarcoma. Resection should be performed only following induction chemotherapy. Chondrosarcoma Chondrosarcomas are the most common primary malignant bony tumors of the pelvis. They often are much larger than plain radiographs indicate. Further imaging with CT and MRI often demonstrates a very large myxomatous component. Metastatic Adenocarcinoma: Breast, Prostate, Renal, Lung, Colon Metastatic adenocarcinoma most commonly involves iliac or periacetabular sites. Most metastatic tumors to the pelvis are treated adequately with radiation therapy. Occasionally, there may be significant acetabular destruction with an impending pathological fracture that requires surgical reconstruction. Renal cell carcinoma (hypernephroma) metastases are an exception. These metastases often require surgical removal, either by resection or by curettage and cryosurgery. Preoperative embolization always is required for these vascular tumors to avoid severe bleeding during surgery. Soft Tissue Sarcomas Retroperitoneal soft tissue sarcomas are more common than intraperitoneal sarcomas and must be evaluated for gastrointestinal, genitouretal, vascular or peripheral nerve involvement. IMAGING AND OTHER STAGING STUDIES Plain Radiography Plain radiography (FIG 2) is of limited value in the assessment of pelvic girdle lesions. Images often are obscure and confusing. The pelvis, particularly the sacrum, is a difficult structure in which to recognize early bone lesions, and major bone lesions initially may be overlooked. For these reasons, there A B C D E FIG 2 A. Plain radiographs revealing a large lytic lesion of the right periacetabular region. On the basis of this radiograph, it appears that the cortices are intact. B. Anteroposterior plain radiograph of the pelvis, read as normal. C. Plain radiographs revealing a cartilage-forming lesion in the left ilium. On the basis of this study alone, it seems that this is an intraosseous lesion. Plain radiographs performed 24 hours after a CT-guided core needle biopsy of a sacral lesion (note the coil) (D) and after 6 weeks (E).

4 13282_ON-17.qxd 3/22/09 10:45 AM Page 4 4 Part 4 ONCOLOGY Section III SPINE AND PELVIS A B C FIG 3 A. CT showed extensive bone destruction and extension of the tumor to the pelvis and the right gluteal region. B. CT of the pelvis revealed a large destructive lesion of the sacrum. C. CT shows an extensive tumor on the medial aspect of the ilium with destruction of the inner table and extension of the pelvis. (A,B: Courtesy of Martin M. Malawer; C: Reprinted with permission from Cancer: Principles and Practice of Oncology, 5th ed. Philadelphia: Lippincott Williams & Wilkins, 1997;38.3: ) should be a low threshold for performing further imaging, especially for initial screening and the postoperative evaluation of reconstructions. CT and MRI CT with intravenous contrast and three-dimensional reconstruction is the optimal technique for assessing the extent of bone involvement and destruction, the osseous anatomy, and the relation between the tumor and the major blood vessels of the pelvis (FIG 3). It is valuable for depicting any distortion of the pelvic anatomy, and aiding in the evaluation of the tumor to decide whether it is resectable. Chest CT is essential for staging purposes in evaluation for pulmonary metastases. MRI with constrast is critical for imaging soft tissue (ie, vessels, nerve, muscle) and osseous involvement. MRI is the optimal modality for imaging soft tissue and marrow involvement. It is attractive for assessment of osseous disease and sacral involvement, and may be helpful with the serial assessment of neoadjuvant (induction) therapy. Bone Scan Three-phase bone scan is used to rule out systemic metastasis and to assess the focal osseous involvement and tumor vascularity in the initial flow phase. A decrease in vascularity after induction chemotherapy may indicate response to treatment. Angiography Angiography is mandatory for determining the vascular anatomy that often is distorted by large pelvic tumors (FIG 4). It is essential to determine the level of the various bifurcations preoperatively and to rule out vascular involvement by the tumor. Embolization of the tumor blood supply before surgery is helpful in minimizing blood loss, especially with vascular tumors and tumors with sacral involvement. Venography The pelvic veins always are much larger than their arterial counterparts. Preoperative venography is used to rule out tumor (mural) thrombi, a common finding in chondrosarcomas and osteosarcomas. Their presence may change the planned surgical approach. FDG-PET Fluorine-18 2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) may be useful in assessing the grade of malignancy, evaluating response to neoadjuvant chemotherapy, and monitoring for local recurrence. Positron emission tomography (PET) combined with CT or MR is useful for co-registered imaging. PET CT scans are useful in early detection of small recurrences. It plays only a minimal role in preoperative planning in determining the extent of surgical resection. Biopsy The purpose of biopsy is to yield a valid tumor diagnosis (benign vs. malignant), tumor grade (high vs. low grade), and FIG 4 Preoperative angiography and embolization of the metastatic lesion shown in Fig 3A. (Courtesy of Martin M. Malawer.)

5 13282_ON-17.qxd 3/22/09 10:45 AM Page 5 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 5 tumor subtype (eg, leiomyosarcoma vs. malignant fibrous histiocytoma). Biopsies may be performed by either open or needle technique. Because open biopsy for pelvic tumors is an extensive procedure, needle biopsy especially CT-guided needle biopsy always is performed initially for both metastatic and primary pelvic tumors. Biopsy technique should follow established guidelines for incision placement within the line of eventual resection, minimize contamination of normal tissues (eg, achieve adequate hemostasis at biopsy closure), and retrieve an adequate specimen for frozen section diagnosis. The biopsy should avoid the gluteal and groin areas, because they are potential sources for flaps for skin closure after anterior and posterior hemipelvectomy, if necessary. Use of the utilitarian surgical incision for open biopsy is recommended. Anatomic Considerations Evaluation of the full anatomic extent of a pelvic tumor cannot be based on a single imaging modality. Combined data, gained from two or more imaging modalities, allow a realistic appreciation of the exact anatomic extent. Even when that information is available, however, the full extent of a pelvic tumor often is underestimated preoperatively. Review of any imaging study of the pelvis, because of the numerous anatomic details, must be performed very methodically. The authors review the structures from the back (midsacral region) and follow the pelvic girdle to the front (symphysis pubis), as described in the following paragraphs. Sacrum, Sacral Alae, and Sacroiliac Joint Most patients who undergo extended hemipelvectomy, which necessitates transection of the sacrum through the ipsilateral neural foramina, regain function of the gastrointestinal and genitourinary tracts. Adding a contralateral compromise of the sacral nerve root will create a severe dysfunction. Tumors that penetrate the sacrum and cross the midline are considered unresectable because of the involvement of bilateral nerve roots (FIG 5). The tumor can be resected, but the morbidity outweighs the questionable oncologic benefit from surgery. The common iliac vessels are just anterior to the sacral ala, and any cortical breakthrough by a tumor in that site may be FIG 5 High-grade chondrosarcoma of the right sacrum, ilium, and periacetabular region, encasing the ipsilateral sacral foramina. Wide excision would necessitate resection through the contralateral sacral foramina, resulting in an unacceptable functional impairment. (Courtesy of Martin M. Malawer.) expected to extend directly to the blood vessels. The sacroiliac (SI) joint is a key anatomic landmark. The major nerves and blood vessels are medial to it; therefore, any tumor or pelvic resection lateral to the SI joint may be expected not to violate the major neurovascular bundle. Involvement of the SI joint must be documented prior to surgery by using the combination of CT, MRI, and bone scan. Major Pelvic Blood Vessels and Structures The common iliac artery bifurcates along the sacral ala, and the ureter crosses the bifurcation on each side. Large tumors around the sacral ala commonly displace and occasionally invade these structures. The mere presence of a major blood vessel or a pelvic viscus involvement is not an indicator of unresectability. Direct tumor involvement is rare. If necessary and curative resection is planned, both structures can be excised en bloc with the tumor and then can be repaired with a graft. However, when a compound resection (bony pelvis and viscus resection) is anticipated, the patient must be informed, and surgical assistance and necessary equipment must be prepared in advance. Sacral Plexus Current imaging techniques cannot accurately identify nerves. Nerve involvement, therefore, is assumed on the basis of the pain pattern, physical examination, and the presence of the tumor in close proximity to a site in which a major nerve or plexus is usually located. Clinical evidence of femoral or sciatic nerve dysfunction usually means direct tumor involvement. In most cases the presence and extent of nerve involvement is established only at the time of surgery. Sacral plexus invasion by tumor has the same significance in terms of resectability as tumor invasion of the sacrum; bilateral involvement is an indicator of unresectability. Sciatic Notch and Nerve The sciatic notch is the site of pelvic osteotomy in resections of the ilium or periacetabular region and in modified hemipelvectomy. CT establishes tumor extension to the sciatic notch, a tight space through which the sciatic nerve and superior gluteal vessels and nerve pass (FIG 6). The piriformis muscle, which divides the sciatic notch, is a key structure, because the sciatic nerve exits the pelvis underneath it and the superior gluteal artery exits the pelvis above it. The patency of the superior and inferior gluteal arteries, which supply the gluteal vasculature, is established by angiography. Adequate blood supply of the gluteal region is a major consideration in flap design, and the artery must be preserved in any pelvic resection, if oncologically feasible. The artery is located only a few millimeters from the periosteum of the sciatic notch roof, and it should be dissected carefully. Ilium The inner aspect of the bone is covered by the iliacus muscle, which originates from the iliac crest. The iliacus is pushed by a growing bone sarcoma and serves as a major barrier to direct extension of tumor to the anatomic structures of the pelvis. Therefore, the iliacus can be used as a safe oncologic margin for resection. In contrast, metastatic carcinomas to the pelvis tend to invade the covering muscle layer in their early growth stage, and a surgical plane between the tumor and nearby structures cannot be easily defined (FIG 7). Although any pelvic organ

6 13282_ON-17.qxd 3/22/09 10:46 AM Page 6 6 Part 4 ONCOLOGY Section III SPINE AND PELVIS A FIG 6 The sciatic notch is a tight space through which the sciatic nerve and superior and inferior gluteal vessels and nerves pass. The sciatic nerve exits the notch underneath the piriformis muscle, and the superior gluteal vessels exit the notch above it. (Courtesy of Martin M. Malawer.) can be infiltrated by a tumor, structures that are anterior and posterior to the flare of the muscle (ie, sacral plexus, sciatic notch and nerve, femoral vessels and nerve, bladder, and prostate) are at greater risk for direct tumor extension. Extension to Pelvic Viscera Direct involvement of a pelvic viscus by a pelvic girdle tumor is rare. Left-sided tumors are more likely to involve a component of the gastrointestinal tract because of its close proximity to the pelvic girdle at that point. A rectal tube is inserted preoperatively during any pelvic resection to facilitate identification of the rectum during dissection. Acetabulum and Hip Joint Wide resection of any bone tumor in the periacetabular region, unlike a resection of the ilium or the pubis, imposes a major impairment on the function of the hip joint. It usually necessitates en bloc resection of the proximal femur and a complex prosthetic reconstruction. Pubis The neurovascular bundle passes within the femoral triangle just anterior to the superior pubic ramus. Tumors extending to or arising from the pubic ramus are in close proximity to the femoral artery, vein, and nerve. In addition, the urethra passes straight underneath the symphysis pubis. Vulnerable structures such as a major blood vessel, nerve, or a viscus must be identified and mobilized before resection. By identifying and isolating crucial srtuctures, the surgeon avoids iatrogenic injury during dissection. Establishing the relation of these vulnerable structures to the tumor allows the surgeon to decide whether to proceed with a limb-sparing procedure or perform an amputation, make the necessary preparations for a vascular graft (if needed), and perform a safe resection. B FIG 7 A. The iliacus muscle (arrows) is pushed by a growing bone sarcoma and serves as a barrier to direct extension of the tumor to the pelvic viscera. High-grade sarcoma of the left ilium pushing the iliacus muscle (arrows) toward the midline. B. Metastatic carcinomas (arrows) to the pelvis tend to invade the covering muscle layer. (Courtesy of Martin M. Malawer.) SURGICAL MANAGEMENT Preoperative Planning Restaging studies Preoperative planning is crucial to obtain an optimal oncologic and functional surgical result. Imaging studies are crucial in addressing the following questions: location and extent of the tumor, the type of pelvic resection that is necessary for adequate removal of the tumor, involvement of critical adjacent structures in the tumor mass (ie, ureter, aorta, inferior vena cava, bladder), and the type of reconstruction that can be achieved. Plain radiographs, CT scans, MRI scans, bone scans, and 3D-CT angiographs are obtained to access the extent of osseous and soft tissue involvement in all anatomic planes. The status of crucial adjacent structures bladder, colon, ureter, inferior vena cava, sacral alar, and possible lumbar extent is reviewed. Using angiography and venography, preoperative embolization is considered, and anatomic distortion and vessel occlusion and venous thrombus are assessed. Consider possible need for prophylactic ureteral stents if there is evidence of preoperative ureteral obstruction or displacement. Medical and anesthesia personnel are consulted to assess medical risk, preoperative laboratory studies, and transfusion needs (eg, prepare red blood cell count, cryo, platelets, and plasma). A risk of major blood loss during surgery is assumed, often equal to one total body transfusion ( 7% body weight in kg). Bowel preparation before surgery and ICU reservation also should be considered.

7 13282_ON-17.qxd 3/22/09 10:46 AM Page 7 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 7 Orthotic brace is fabricated preoperatively for postoperative use. Colostomy planning and training must be considered if there is left colon involvement, or large left-sided pelvic tumors, both of which can be detected preoperatively with contrast-enhanced CT and colonoscopy. Appropriate prosthetic implants (eg, total hip replacement vs. saddle prosthesis), bone allograft, or other implants must be ordered. Positioning At the time of surgery all patients should have a Foley catheter and a rectal tube placed. The rectum is sutured closed around the rectal tube to avoid iatrogenic contamination during the operative procedure. During surgery the surgeon may palpate the balloon of the Foley catheter in the bladder and the rectal tube through the wall of the rectum, to assist in proper identification of these structures. This is especially helpful with large pelvic tumors, especially those on the left side. Type 1 resection (iliac ): the patient is positioned in the lateral decubitus position with an anterior tilt to allow posterior access (FIG 8A D). Type 2 resection (periacetabular): the patient is positioned in the lateral decubitus position for access to both the anterior and posterior pelvis (FIG 8E,F). A B C D E F G FIG 8 Type 1 pelvic (ilium) resection can be either partial (A), in which only part of the ilium is transected, or complete (B). Partial (C) and complete (D) type 1 resections. E. Type II pelvic (periacetabular) resections. Reconstruction was performed with a saddle prosthesis. F. Type II pelvic resection. G I. Type III pelvic (pubic) resection. These resections may include the superior pubic ramus (G), inferior pubic ramus, or both rami (H). I. Type III pelvic resection. H I

8 13282_ON-17.qxd 3/22/09 10:46 AM Page 8 8 Part 4 ONCOLOGY Section III SPINE AND PELVIS hamstrings from the ischium, the lateral margin of the sacrum, and the entire buttock. The most useful approach to pelvic biopsy or resection is the utilitarian pelvic incision. All or part of the incision can be used for adequate exploration and resection of the majority of pelvic girdle tumors. Significant concern exists regarding the possible extracompartmental implantation of tumor cells following biopsy or resection of a pelvic tumor, procedures that are difficult to perform under optimal hemostatic conditions. Unnecessary biopsies must, therefore, be avoided. If biopsy is indicated, the proper technique and a suitable approach must be chosen. The biopsy tract must be positioned along the line of the future utilitarian incision, remote from the major neurovascular bundle and the abductors. CT-guided core needle biopsy is considered to be an accurate and safe diagnostic tool in the diagnosis of musculoskeletal tumors and is the modality preferred by the authors. The utilitarian incision may be used for hemipelvectomy by continuing the distal portion of the primary incision posteriorly around and behind the thigh and bringing it anteriorly along the inferior pubic ramus to the symphysis, thus encircling the thigh but still allowing the large posterior flap to be used for primary wound closure. FIG 9 The utilitarian pelvic incision. (Courtesy of Martin M. Malawer.) Type 3 resection (pelvic floor): The patient is positioned supine with the lower extremity flexed and abducted to provide exposure of the retroperitoneal space, the femoral triangle, the perineum, the symphysis pubis, and the ischiorectal space (FIG 8G I). Approach The utilitarian pelvic incision is indicated (FIG 9). The incision begins at the posterior inferior iliac spine and extends along the iliac crest to the anterior superior iliac spine. It is separated into two arms: one is carried along the inguinal ligament up to the symphysis pubis; the other turns distally over the anterior thigh for one-third the length of the thigh and then curves laterally just posterior to the shaft of the femur below the greater trochanter and follows the insertion of the gluteus maximus muscle. Reflection of the posterior gluteus maximus flap exposes the retrogluteal space, the proximal third of the femur, the sciatic notch, the sciatic nerve the sacrotuberous and sacrospinous ligaments, the origin of the Type 1 Resection: Iliac Resection The incision for an iliac resection is ilioinguinal, following the iliac crest and curving posteriorly at the level of the sacroiliac joint. It then follows the length of the sacroiliac joint combined with a lateral incision to expose the outer portion of the ilium, sciatic notch, and retrogluteal space Type 2 Resection: Periacetabular Resection A combination of an anterior retroperitoneal approach and lateral anterior incision along the femur that curves posteriorly is used for a periacetabular resection. A lateral, posterior-based fasciocutaneus flap, called a gluteal flap, is then raised. This permits easy access and visualization of the retrogluteal space; hip joint, sciatic notch, sciatic nerve, and ischium, as well as the supra-acetabular area needed for the superior osteotomy. Type 3 Resection: Pelvic Floor and Pubic Region Three incisions are required for a resection of the pelvic floor and pubic region. The main incision is the retroperitoneal (ilioinguinal) incision to permit retroperitoneal exploration and mobilization of the major vessels and nerves.two longitudinal incisions are required to develop a distal-based flap of the anterior thigh so as to expose the femoral triangle as well as the adductors attaching to the obturator foramen. One incision follows the perineal crease; the second begins at the lateral portion of the ilioinguinal incision at the level of the anterior superior iliac spine. TECHNIQUES Type 1: Iliac Resection The patient is placed in the lateral decubitus position with a posterior tilt. The utilitarian pelvic incision is used. Its ilioinguinal component is advanced medially to the symphysis pubis, and its posterior arm is brought to the level of the sacroiliac joint (TECH FIG 1A,B). All muscle attachments, with the exception of the iliacus and gluteus minimus and portions of the gluteus medius, which are resected en bloc with the tumor, are removed from the iliac crest. The abdominal wall musculature, the sartorius muscle, and the tensor fasciae latae muscle are transected from the iliac crest and reflected away from the ilium. The rectus femoris muscle remains intact. The iliotibial band is transected from its origin from the iliac crest and reflected posteriorly along with the gluteus maximus. Large fasciocutaneous flaps are raised and reflected medially and posteriorly.

9 13282_ON-17.qxd 3/22/09 10:46 AM Page 9 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 9 TECHNIQUES B A C D TECH FIG 1 A. Incision and surgical approach. The entire utilitarian incision is used for type I resection. The posterior fasciocutaneous flap exposes the entire retrogluteal area: the sciatic notch, the sciatic nerve, the abductor muscles, and the hip joint. This approach provides a good exposure of the retroperitoneal space as well as the posterior retrogluteal area and permits a safe resection of the ilium. The ilioinguinal component is advanced medially to the symphysis pubis and posteriorly to the sacrum (B). C. Posterior exposure and muscle releases. The abdominal wall musculature is transected off of the iliac crest. The sartorius and tensor fascia lata muscles are transected from their tendinous insertions and reflected distally. The rectus femoris muscle remains intact. Large fasciocutaneous flaps are raised and reflected medially and posteriorly. The iliotibial band is transected from its origin from the iliac crest and reflected posteriorly along with the gluteus maximus. D. Anterior (retroperitoneal) exposure. The retroperitoneal space is easily exposed and explored through the ilioinguinal component of the incision. The plane between the iliacus and the psoas muscle is developed with caution, because the femoral nerve lies in that space. The psoas muscle and the femoral nerve are reflected medially, and the iliacus muscle is transected through its substance. The femoral nerve is preserved. (continued)

10 13282_ON-17.qxd 3/22/09 10:46 AM Page Part 4 ONCOLOGY Section III SPINE AND PELVIS TECHNIQUES E G F TECH FIG 1 (continued) E. Posterior exposure and release of gluteal muscles. The retrogluteal area is exposed. The gluteus maximus muscle is released from the iliotibial band and from the femur and reflected posteriorly. The sciatic nerve is identified and preserved. All of the remaining abdominal muscles are released from the wing of the ilium. The gluteus medius muscle is transected through its substance, 2 to 3 cm distal to the inferior border of the tumor. It is important to try to save as much muscle belly as possible. F. Supra-acetabular osteotomy and sacroiliac disarticulation. A malleable retractor is inserted through the greater sciatic notch, along the inferior border of the inner table, and out just underneath the anterior superior iliac spine, to protect the pelvic viscera. The ilium is transected above the hip capsule, leaving the origin of the rectus femoris muscle and the roof of the acetabulum intact. Care is taken not to enter the hip joint. Insert: The sacroiliac joint is opened from within the pelvis. The iliac vessels must be mobilized and retracted before attempting to open the sacroiliac joint. G. Soft tissue reconstruction. The gluteus medius muscle is sutured to the abdominal wall musculature with the ipsilateral lower extremity in abduction. Dacron tape must be used to reinforce this reconstruction. The suture line also is reinforced by oversewing the tensor fascia lata and sartorius muscles. (Courtesy of Martin M. Malawer.) The plane between the iliacus and the psoas muscle is developed cautiously, because the femoral nerve lies in that space. The psoas muscle and the femoral nerve are reflected medially, and the iliacus muscle is transected through its substance (TECH FIG 1C). The external iliac artery, which lies against the lower margin of the ilium, gives off no major branches along the inner table of the ilium; ligation of large blood vessels is not required, therefore, in type I pelvic resection. Most tumors of the ilium break through the outer table and push the gluteus medius muscle laterally. The gluteus medius muscle is transected through its substance, 2 to 3 cm distal to the inferior border of the tumor (TECH FIG 1D,E). It is important to try to save as much muscle belly as possible because that will be the major component in soft tissue coverage of the pelvic content and will be necessary for reconstruction of the abductor mechanism. Osteotomy of the ilium is performed using a malleable retractor, which is inserted through the greater sciatic notch, along the inferior border of the inner table, and out just underneath the anterior superior iliac spine, to protect the pelvic viscera (TECH FIG 1F). The ilium is transected as shown by the dotted line in the figure, leaving the origin of the rectus femoris muscle and the roof of the acetabulum intact. Osteotomy of the posterior aspect of the ilium is then performed; a malleable retractor is positioned through the greater sciatic notch, along the posterior border of the ilium, and parallel to the ipsilateral sacral ala (insert, Tech Fig 1F). The most important component of soft tissue reconstruction is the attachment of the proximal rim of the gluteus medius muscle to the abdominal wall musculature. Even if the entire gluteus medius muscle was spared, the attachment of these two muscle groups, which are not

11 13282_ON-17.qxd 3/22/09 10:46 AM Page 11 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 11 anatomically connected, creates a significant tension, which can be reduced by placing the lower extremity in abduction. The suture line is reinforced with the tensor fasciae lata and sartorius muscles with 3-mm Dacron tape (TECH FIG 1G). Closure of the muscle layer must be meticulous, because poor healing and wound dehiscence will expose the abdominal and pelvic contents and will be difficult to manage. Optional Reconstruction It is not necessary to reconstruct the resultant bony defect, although allograft reconstruction has been reported. For iliac osseous reconstruction, allograft should be thawed with permanent/tissue culture. Gram stain has a high rate of false positives and should be avoided. Cut the allograft after careful sizing and orientation and fix with a 4.5-mm reconstruction plate. Use intraoperative radiographs to confirm screw placement. Two deep soft drains (anterior and posterior) are placed deep to the fascial closure. Type 2: Periacetabular Resection The patient is in the lateral decubitus position with posterior tilt to maximize anterior dissection. The utilitarian incision is used to expose both the anterior (internal) and posterior (extrapelvic) aspects of the pelvis. The ilioinguinal incision is used to develop the retroperitoneal plane, and the posterior gluteus maximus fasciocutaneous flap is used to develop the retrogluteal space. The iliac vessels are mobilized first, and the hypogastric artery is identified and ligated. The sciatic and femoral nerves are identified and protected. The level of osteotomy through the ilium is identified from within the pelvis, as are the superior pubic rami. Identification of the superior pubic rami requires mobilization of the external iliac and femoral vessels as they cross the ramus (TECH FIG 2). A large posterior myocutaneous flap is developed with the gluteus maximus muscle. The gluteus maximus muscle is detached from the iliotibial band and femur to enable it to be retracted posteriorly. This exposes the retrogluteal space: the ilium, sciatic notch, sciatic nerve, and hip joint. The ischium is identified through the posterior incision and is osteotomized above the level of the biceps femoris tendon insertion. Complete removal of the periacetabulum requires release of the sacrospinous ligament and some of the pelvic floor musculature. An ilioinguinal incision is used with a separate posterolateral hip incision for hip exposure and replacement, posterior column osteotomy, and exposure of the sciatic nerve. Three types of osteotomies may be used for periacetabular resection: (1) supra-acetabular osteotomy; (2) superior pubic ramus osteotomy; and (3) ischial osteotomy. TECHNIQUES A B C D E F TECH FIG 2 A. Plain radiograph showing an extremely high-grade malignant fibrous histiocytoma arising from the superior and inferior pubic ramus involving the entire obturator foramen, pelvic floor, and medial and supra-acetabular aspect of the acetabulum (solid arrows). B. Gross specimen following type II/type III pelvic resection. C. Gross specimen following a complete internal hemipelvectomy (type I/type II/type III pelvic resection). D. Radiograph of the resected specimen showing complete involvement of the hemipelvis. The defect superiorly was created by an open biopsy. E. Gross specimen of a combination type II/type III pelvic resection. F. Gross specimen following a type III pelvic resection. A large tumor mass is seen arising from the obturator internus muscle (solid arrows). A, acetabulum; IL, portion of the ilium; IP, inferior pubic ramus and pubis; P, the entire pelvic floor, including the superior and inferior pubic ramus; SP, superior pubic ramus; SY, symphysis pubis. (Courtesy of Martin M. Malawer.)

12 13282_ON-17.qxd 3/22/09 10:46 AM Page Part 4 ONCOLOGY Section III SPINE AND PELVIS TECHNIQUES A total hip exposure is used to identify the sciatic nerve and posterior column. The procedure is begun with dissection of the external rotators and osteotomy of the femoral neck, per total hip procedure. Cut the femoral neck at the standard neck length (1.0 cm proximal to the lesser trochanter). Incise the hip capsule peripherally with dissection of the sciatic nerve proximally to the sciatic notch. The anterior and posterior columns are exposed to allow osteotomy of the acetabulum. Posterior column osteomy requires careful exposure and retraction of the sciatic nerve and gluteal vessels. Reconstruction After Type 2 Resection Several choices are available for reconstruction following a type 2 resection: composite allograft; saddle reconstruction (Link, America); partial pelvic prosthesis (Stryker, Mahwah, NJ); various reconstruction rings with large phlanges; and ischiofemoral arthrodesis. Each has unique techniques, complications, functional deficits, and results. Composite Allograft Acetabular Reconstruction Femoral component: ream and place the uncemented femoral component through the posterior lateral approach before proceeding with iliac osteotomy resection. Acetabulum: ream the allograft for the acetabular component and place the acetabular component (cement and screws) into the allograft to confirm graft and acetabular orientation in situ with radiography before screw or cement fixation. Check acetabulum positioning with radiographs before and after fixation or cementation. Orient the iliac graft before confirming the acetabular orientation, and fix the graft with a reconstruction plate and screws. Use an extended polyethylene acetabular rim and consider a large femoral head (32 36 mm) to improve postoperative stability. Closure. Using the inguinal ligaments, reconstruct the abductors, especially if a trochanteric osteotomy was done. Perform pelvic closure at the iliac crest and inguinal canal with wound drainage catheters. Type 2: Resection and Reconstruction with Saddle Prosthesis Notchplasty (Tech Fig 3A C) A notch is created in the remaining ilium using a highspeed burr. The notch should be placed in the thickest region of the remaining bone (usually medial). Preparation of the Proximal Femur The proximal femur is prepared as for a standard femoral component. The intramedullary canal of the proximal femur is reamed to accept the largest-diameter stem and allow for a 2-mm circumferential cement mantle. Once reaming is completed, and the appropriate-sized stem (diameter and length) is selected, a distal femoral cement plug is inserted to a depth of 2 cm below the tip of the selected femoral stem. The femoral canal then is irrigated with saline and packed with gauze. Once the cement (polymethylmethacrylate) is prepared, the gauze is removed, and the femoral prosthesis is cemented within the proximal femur. Trial Reduction A reduction using trial components is critical in assessing accurate length of the base component (intercalary segment) and determining optimum soft tissue tension (TECH FIG 3D K). The base component length should be determined by the distance between the ilium and femoral neck cuts, because the length indicated on the base component is the total length from the notch of the saddle to the femoral collar. The base component should be selected so that reduction is barely possible and there is minimum play in the reduced joint. The surgeon should be able to reattach the abductor mechanism to its anatomic position on the osteotomized greater trochanter. A trial reduction also can determine areas where the saddle component may impinge on the existing notch during intraoperative range of motion. These areas can be further contoured with a high-speed burr to prevent impingement, which may result in limited motion or dislocation. Hip motion (flexion to at least 90 degrees, extension to 30 degrees, abduction to 45 degrees, adduction to neutral, and rotation) should be possible without evidence of impingement or dislocation. Abductor Mechanism Reconstruction The osteotomized greater trochanter and abductors are reattached to their original location using cables. If the greater trochanter was included in the resected specimen, the abductor mechanism is reattached to the prosthesis using 3-mm Dacron tapes or a cable system. Soft tissue tension and prosthetic stability are again tested once the abductor mechanism reconstruction is complete. The piriformis and short external rotator muscles are brought forward and reattached to the proximal femur (or prosthesis). The gluteus maximus muscle is then reattached to its insertion using nonabsorbable suture (TECH FIG 3L N). Pelvic closure involves attachment of the inguinal canal and abdominal wall to the symphysis pubis and lateral iliac crest. Soft tissue tension and prosthetic stability are tested again once the abductor mechanism reconstruction is complete. The piriformis and short external rotator muscles are brought forward and reattached to the proximal femur (or prosthesis). The gluteus maximus is then reattached to its insertion using nonabsorbable suture. For high type II pelvic resections, reconstruction should be carried out with a partial pelvic prosthesis (Stryker, Mahwah, NJ). Type 3 Resection: Pelvic Floor A utilitarian pelvic incision with a perineal extension is used (three-incision approach).

13 13282_ON-17.qxd 3/22/09 10:46 AM Page 13 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 13 A B C TECHNIQUES E D G F TECH FIG 3 A. Photograph following a periacetabular resection showing the remaining ilium (il), the sciatic nerve (S), the greater trochanteric osteotomy (G), and the femoral head. B. Intraoperative photograph demonstrating the creation of the deep notch (large arrows). C. Reduction of the saddle prosthesis into the iliac notch (IL). The notch (solid arrows) must be as deep as the saddle and permit approximately 45 degrees of flexion and extension, as well as abduction and adduction. D. Surgical exposure using the utilitarian pelvic incision. E. A large posterior fasciocutaneous flap based medially permits the release of the gluteus maximus. F. Schematic diagram of the mobilization of the periacetabular structures and the three osteotomies that are necessary for a complete resection of the acetabulum. G. Schematic of the close-up view of the superior pubic ramus osteotomy. (continued)

14 13282_ON-17.qxd 3/22/09 10:46 AM Page Part 4 ONCOLOGY Section III SPINE AND PELVIS TECHNIQUES H I J K L M N TECH FIG 3 (continued) H. Schematic diagram of the infra-acetabular osteotomy. I. A notch is made in the supra-acetabular roof or remaining ilium for the saddle prosthesis to sit in. J. Schematic diagram of the saddle prosthesis reduced into the notch. K. Schematic diagram of the saddle prosthesis following a periacetabular resection for sarcoma and radical curettage for a large acetabular metastasis. Postoperative radiographs and CT scans demonstrating common postoperative radiographic findings. L. AP radiograph of the pelvis with a saddle prosthesis in place. M. A 45-degree oblique radiograph of the affected side of the pelvis. N. CT scan showing a typical saddle prosthesis in good position. AB, abductor muscles; G, gluteal muscles; IC, iliacus muscle; S, sciatic nerve. (A C, L N: Courtesy of Martin M. Malawer; D K, reprinted with permission from Malawer M. Reconstruction following resection of primary periacetabular tumors. Semin Arthroplasty 1999;10: ) The patient is positioned with the ipsilateral hip slightly elevated. The ilioinguinal component of the utilitarian pelvic incision with a lateral and perineal (medial) extension is used (see Tech Fig 1G). This incision allows exposure and mobilization of the femoral vessels and nerve through a distal-based anterior flap. Perineal extension of the incision is used to expose the ischium, which is resected through the ischiorectal fossa when the resection is performed for a large pubic lesion. Large myocutaneous flaps are raised. The spermatic cord is reflected medially. The inguinal ligament is transected from its pubic insertion and reflected laterally. The neurovascular bundle (ie, the femoral artery, vein, and nerve) is retracted laterally, exposing the origin of the adductor magnus and pectineus muscles, which is transected off the pubis and reflected distally. Using the lateral component of the incision, the origins of the hamstrings, adductors, and gracilis are transected off the ischium and reflected distally (TECH FIG 4). The first malleable retractor is placed behind the symphysis pubis, in front of the bladder. The second malleable retractor is placed behind the superior pubic ramus and in front of the inferior pubic ramus, medial or lateral to the ischium, depending on the required oncologic margins (TECH FIG 4C).

15 13282_ON-17.qxd 3/22/09 10:46 AM Page 15 Chapter 17 OVERVIEW ON PELVIC RESECTIONS: SURGICAL CONSIDERATIONS AND CLASSIFICATIONS 15 TECHNIQUES A B C TECH FIG 4 Incision. A. The ilioinguinal component of the utilitarian pelvic incision with a modified perineal extension are used. B. Schematic of the three osteotomies required to remove the pelvic floor. C. Transection of the symphysis pubis, superior pubic ramus, and ischial osteotomy. (Courtesy of Martin M. Malawer.) Osteotomy through the symphysis pubis and pubic rami is performed. It is important to smooth the sharp bony edges, especially those that lie against the bladder. Surgical wounds around the groin are notoriously associated with a high incidence of dehiscence and infection. Meticulous wound closure with adequate drainage is, therefore, mandatory. Continuous suction is required for 3 to 5 days. Perioperative intravenous antibiotics are continued until the drainage tubes are removed. Postoperative mobilization with weight-bearing as tolerated is allowed. Rarely, reconstruction of the pelvic floor with Marlex (CR Bard, Cranston, RI) mesh is required. Type 4 Resection: Hemipelvic Table 1 describes hemipelvic resection, along with other techniques. Combined, extended full pelvic dissection from symphysis pubis to sacroiliac joint is required. Complete dissection of the sciatic notch, the hip joint, the sciatic nerve, and the femoral vessels is required. Pelvic reconstruction is more challenging because of the need for fixation at the sacrum and symphysis pubis and the difficulty in orienting a pelvic graft. Some surgeons do not recommend reconstruction but accept 3 inches of shortening and the use of a pelvic longleg brace. A large amount of intraoperative blood loss and hemipelvic graft fixations present significant surgical challenges.