Bone and Extended Pelvic Resections




BACKGROUND



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Most recurrent and locally advanced gynecologic malignancies carry a poor prognosis. Advances in multimodality management have improved local control and overall survival (OS).1,2,3 Historically, tumors invading the pelvic sidewall or involving the major vessels or nerves were considered inoperable. Early reports of central pelvic exenteration were discouraging and associated with high perioperative mortality (28%) and major complications (100%).4 Advances in several medical disciplines have resulted in greatly improved outcome and reduced morbidity and mortality in the management of these complex tumors. Increasingly effective chemotherapy and refinement in methods of radiation administration have rendered these large tumors, most of which had previous radiation therapy, amenable to wide surgical resection.



The use of modern imaging technology has improved our ability to accurately outline the anatomy of the tumors preoperatively and rule out distant metastases. Several studies have shown that obtaining negative surgical margins of resection is essential to local tumor control and improvement of OS.1 Preoperative medical assessment and management, expert anesthesia, and postoperative intensive care have reduced perioperative mortality to less than 5%.1,2,3 The majority of patients undergoing radical pelvic surgery including those with recurrent endometrial and cervical tumors have already had surgery and radiation therapy. Patients with locally advanced primary carcinomas and a minority with advanced primary or recurrent sarcomas may also be candidates for the type of radical pelvic surgery described in this chapter.




INDICATIONS AND CLINICAL APPLICATIONS



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This chapter describes the surgical management of a small group of tumors, which, due to their proximity to or invasion of bone, require bony pelvic resections in order to achieve a wide surgical margin. We also discuss management of tumors involving major vessels and nerves. Major sidewall soft tissue resections are discussed in Chapter 9.



Bony involvement occurs from extension of tumor growth into the periosteum by direct invasion or by spread through local vessels into the bone (local metastasis). In some cases, the tumors do not actually involve bone but are inseparable from it, such that a wide resection can only be accomplished by resecting the adjacent bone. Better understanding of the functional anatomy of the pelvis and our ability to reconstruct following major bony resections has made these procedures possible. Resection of the periacetabular area or the hip usually requires extensive reconstruction, while resection of the area above and below the hip may not.5 It should be emphasized that the number of patients who are suitable candidates following full local and systemic staging are few and that a multidisciplinary approach is essential to ensure a satisfactory outcome.




ANATOMIC CONSIDERATIONS



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A thorough knowledge of the topographic and functional anatomy of the pelvis is essential for surgeons embarking on these operations. Knowledge of the topographic anatomy ensures that the surgeon is familiar with important landmarks and relationships of various structures to each other, enabling safe and effective resections. Familiarity with functional anatomy allows the surgeon to decide whether surgery is feasible, if it would result in an acceptable quality of life, and whether soft tissue and bony reconstruction are necessary. This knowledge is also important when counseling patients preoperatively.



The true pelvis is tilted 60° anterior to the long axis of the body, so that on digital examination per rectum or vagina, the pubic bone, ischial spine, and tip of coccyx are in the same horizontal plane (Figure 10-1). These are landmarks that are also helpful intraoperatively. The lumbosacral nerve and sympathetic trunks will be found deep to the common iliac vessels anterior to the sacral ala (Figure 10-2). The ureter, adherent to the peritoneum, crosses the bifurcation of the common iliac arteries. The piriformis muscle is a key anatomic structure in the pelvis and can be readily identified (Figure 10-3). It lies above the palpable ischial spine and sacrospinous ligament, and it runs through the greater sciatic notch. The superior gluteal vessels and nerves pass above the piriformis to exit the pelvis and supply the abductor muscles of the hip. The sciatic nerve, inferior gluteal, and pudendal neurovascular structures lie anterior to the piriformis and pass posteriorly out of the pelvis above the sacrospinous ligament. The pudendal nerve and vessels curve over the ischial spine and enter the ischiorectal fossa. The anterior sacral foramina can be easily identified and their emerging sacral roots visualized. The obturator nerve lies on the sidewall of the pelvis lateral to the iliac vessels. It passes through the obturator foramen with the obturator vessels anteriorly and inferiorly.




Fig. 10-1.


Bony pelvis with ligaments.






Fig. 10-2.


Anterior view of pelvic inlet showing major neurovascular structures entering the pelvis.





The functions of the bony pelvis include supporting and protecting its contained viscera and neurovascular structures, and transmission of body weight to the lower limbs. It is a semirigid ring composed of the innominate bone (the entire fused ilium, ischium, and pubis) laterally and the sacrum posteriorly (see Figure 10-1). Anteriorly, the pubic bones join at the symphysis pubis, a relatively weak cartilaginous joint. Posteriorly, the innominate bone, often referred to as the hip bone, articulates with the sacrum through bilateral strong sacroiliac joints. This articulation extends from the S1 to the S3 segments. The sacroiliac joint is a complex one, consisting of a small synovial joint anteriorly, which allows minimal gliding motion. However, most of the articulation is composed of very strong ligaments that are both intra-articular and extra-articular. The posterior spinal pelvic ligaments are some of the strongest in the body. The articular surfaces of the joints are irregular and afford some stability, but overall stability is dependent on the strong sacroiliac ligaments. Removal of the inferior two-thirds of the sacroiliac joint requires surgical stabilization. The anterior symphysis pubis and posterolateral sacrospinous and sacrotuberous ligaments afford minor stability, and their removal usually causes little disability. Major resection of the innominate bone, which disrupts the transmission of weight from the spine to the lower limb, usually requires reconstruction.



The sidewall of the true pelvis is largely lined by the obturator internus, which is covered by the dense pelvic fascia. A tendinous fascial arch extending from the ischial spine posteriorly to the pubis anteriorly along this muscle forms the origin of the pelvic floor muscles. These muscles support the pelvic and abdominal viscera, especially during periods of increased intraabdominal pressure. They also surround the vagina, bladder neck, and rectum, acting as an adjuvant sphincter. When resecting the pelvic floor muscles, surgical reconstruction using muscle flaps from the abdomen and thigh help restore these important functions.



Ligation of the internal iliac (hypogastric) vessels is well tolerated (see Figure 10-3). Resection of the common or external iliac arteries requires reconstruction. Ligation or resection of the common or external iliac veins usually results in lower limb edema. Venous reconstruction is typically not successful, but early postoperative pressure bandaging can control subsequent lower limb swelling.




Fig. 10-3.


Pelvic sidewall showing sacral plexus and major vessels.





The autonomic nerves lie in the pelvic plexus adjacent to the internal iliac arteries and their branches (see Figure 10-3). They are composed of the parasympathetic fibers from the second, third, and fourth sacral nerves, and the sympathetic fibers from the sympathetic trunks entering the pelvis from the lower thoracic and upper lumbar spine. These nerves supply the bladder, rectum, and reproductive organs. Parasympathetic fibers are motor to rectal and bladder detrusor muscles and relax their sphincters. Sympathetic fibers contract sphincters and constrict vessels. These nerves can be destroyed with sacral and posterior pelvic resections, resulting in bowel incontinence, bladder obstruction, and loss of sexual function.



The femoral, sciatic, and obturator nerves are the major spinal nerves supplying the lower limbs (see Figure 10-2). The obturator nerve adducts the thigh and its sacrifice results in only mild disability. Resection of the sciatic or femoral nerves does result in significant disability. The sciatic nerve supplies the hamstring muscle, all the muscles of ankle and toe flexion, and sensation to the leg below the knee and foot, with the exception of a small pretibial area which is supplied by the saphenous branch of the femoral nerve. The femoral nerve supplies the quadriceps muscles, which extend the knee and stabilize the leg when walking. It also supplies sensation to the anterior and medial thigh and pretibial areas. Patients can walk when either nerve is excised; however, removal of both nerves results in such disability that limb salvage is usually contraindicated.



Resection of the sacral plexus above the piriformis muscle results in significantly more ambulatory disability than resections below this muscle, as the gluteal nerves that supply the abductor muscles of the hip will be sacrificed (see Figure 10-2). This results in loss of lateral hip stabilization, in addition to the loss of ankle and foot motion. The pudendal nerve exits the pelvis lateral to sciatic and gluteal nerves at the top of the ischial spine. It immediately enters the ischiorectal fossa supplying motor function to the pelvic floor, lower vagina, anal canal, and urethra. Every effort should be taken to preserve this nerve.




PREOPERATIVE PREPARATION



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Box 10-1 KEY SURGICAL INSTRUMENTATION




  • Osteotome and oscillating saw



  • Self-retaining retractor



  • Long pelvic instruments



  • Electrocautery with long tip



  • Peripheral nerve stimulator




A detailed preoperative history and physical examination must be carried out by all involved surgeons. Patients with poor performance status and significant comorbidity should not be subjected to these procedures until the status is satisfactorily upgraded. Objective neurologic findings in the lower limbs such as loss of peripheral nerve function or loss of bowel and/or bladder function usually indicate invasion of nerve, which will necessitate their removal en bloc with the tumor. In selected patients at high risk of prolonged postoperative bleeding, which may constitute a contraindication to anticoagulation, preoperative insertion of an inferior vena caval filter may be prudent.



Imaging of the pelvis including plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) scans are essential to study the extent of the tumor and plan surgery. It is also necessary to rule out systemic extrapelvic metastases in these patients using positron emission tomography (PET)/CT scans before considering surgery. Recent data have shown that PET/MRI had greater diagnostic confidence and inter-reader agreement than either MRI or PET/CT in patients with recurrent gynecologic cancers.6




SURGICAL PROCEDURE



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Box 10-2 MASTER SURGEON’S PRINCIPLES




  • Obturator nerve may be excised with little disability



  • Unilateral resection of either the femoral or sciatic nerve is possible with satisfactory postoperative ambulatory function



  • Resection of the sacral plexus above the piriformis muscle results in significantly greater ambulatory disability than resection below it



  • Pudendal nerve preservation is important if resection not indicated



  • Resection of the common or external iliac artery requires reconstruction



  • Disruption of the hip and periacetabular pelvis should be reconstructed




Pelvic Bone Resections



Curative surgery for localized pelvic tumors can only be accomplished with a wide resection with negative pathologic margins (R0 resection). In suitable cases, all or parts of the hemipelvis (innominate bone) and surrounding soft tissue can be resected while preserving a functional lower limb below.



Pelvic bone resections have been classified into four types based on the structures removed (Figure 10-4)7,8:





  1. Type I: ilium



  2. Type II: periacetabular



  3. Type III: ischium and pubis



  4. Type IV: sacral ala





Fig. 10-4.


Types of pelvic resections: Type I (ilium), Type II (periacetabular), Type III (ischium and pubis), Type IV (sacra ala).





Each type can be extended to include adjacent areas. Complete resection of the innominate bone with sacral ala is classified as a Type I, II, III, and IV resection. This is also known as an extended internal hemipelvectomy.



Technique



The surgical approach to the pelvis is done through an iliofemoral incision with an ilioinguinal and perineal extension (Figure 10-5).9 Any part or all of this incision is used depending on the area being resected. Resection Types I and II can be carried out through the iliofemoral portion alone while exposure of the pubic body and rami require the ilioinguinal portion.

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Jan 12, 2019 | Posted by in GYNECOLOGY | Comments Off on Bone and Extended Pelvic Resections
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