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Techniques in pelvic resection
Techniques in Pelvic Resection Richard L. McGough, III, MD,* and Alan W. Yasko, MD† Resection of tumors of the bony pelvis is one of the more difficult procedures in orthopedic surgery. The depth of the operative field, complex three-dimensional anatomy, and ubiquitous presence of delicate surrounding structures makes these procedures both taxing and time consuming. Approaching pelvic resections requires both a thorough knowledge of the three-dimensional anatomy and a systematic approach to exposure and protection of the structures to be preserved. Because pelvic surgery is fraught with complications under the best of circumstances, deficiencies in either anatomy or approach can lead to devastating consequences. Although the specific order of dissection can be varied based on the dictates of the tumor, an organized approach follows a general direction from anterior to posterior, and from inside to outside. The abdominal wall dissection is performed first, and dissection of the vessels and femoral nerve often follows logically. This will lead the surgeon posteriorly to the sacroiliac joint and the sciatic notch. Completing the intrapelvic dissection allows identification of bony landmarks for osteotomy planning. The extrapelvic approach generally follows. A thoughtful, systematic, detail oriented approach can minimize both intraoperative blood loss and risk of iatrogenic injury to vital surrounding structures. Oper Tech Orthop 14:259-266 © 2005 Elsevier Inc. All rights reserved. KEYWORDS pelvis, innominate bones, surgical exposure, sacrum, pelvic resection, ilioinguinal, sacroiliac
T
he surgical management of tumors of the bony pelvis is a challenge for the orthopedic oncologist. As with tumors of the appendicular skeleton, limb-sparing techniques currently predominate among the varied procedures for the treatment for tumors of the pelvis. The extent of the exposure and the appropriate surgical planes of dissection are determined by the type of pelvic resection performed. The formal classification of the types of limb-sparing pelvic resections described by Enneking and Dunham in 1978 provides the basis for the surgical oncologic approaches to malignant tumors (Fig. 1).1 A limited resection, type I (iliac wing only), with osteotomies through the iliac neck and sacroiliac joint commonly can be performed with limited pubic or perineal exposure.2 On the contrary, resection of the entire hemipelvis (types I, II, III, IV) requires full pelvic exposure with a midline exposure of the sacrum as well. The type of resection and, therefore, exposure, is dictated by the tumor extent. For the purposes of this discussion, a full pelvic exposure will be detailed. The
*Department of Orthopaedic Surgery, The University of Pittsburgh School of Medicine, Pittsburgh, PA. †Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX. Address reprint requests to Alan W. Yasko, MD, Professor, Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 444, Houston, TX 77030. E-mail: [email protected]
1048-6666/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2004.11.002
components of the exposure pertinent to the anatomic region to be resected can be selected from their description
Surgical Preparation Preoperative Planning Attention to detail in the preoperative planning stage is critically important to the success of the surgery. Appropriate diagnostic imaging with computed tomography and/or magnetic resonance imaging (MRI) is necessary to delineate the bone and soft tissue extent of the tumor and its relationship to the major blood vessels, nerves, and pelvic viscera. Magnetic resonance imaging is indispensable for the evaluation of the relationship of tumor and intra- and extrapelvic structures. Key structures to note include the iliac vessels and femoral nerve anteriorly and the lumbosacral plexus posteriorly. The MRI also will demonstrate the extent of the tumor within the bone and in the adjacent soft tissues. The extent of intra- and extrapelvic muscle that will be resected can also be determined preoperatively. Computed tomography is complementary to the MRI and provides information regarding the tumor and superior pelvic bone detail.
Intraoperative Set-Up Although in most pelvic resections the peritoneum will not be entered, a standard bowel prep before surgery will decrease bacterial counts in the event of an inadvertent enter259
260 otomy and decrease the volume of bowel contents thereby improving the space available within the pelvis. The intraoperative set up for pelvic resection requires substantial monitoring and care. After anesthetic induction and appropriate endotracheal intubation, placement of ureteral stent(s) is beneficial to aid the identification of the ureter(s), to reduce the potential for injury. Appropriate invasive monitoring with both intravenous and intraarterial access should be obtained, and central venous lines should be strongly considered for both access and monitoring purposes. Patients undergoing limb-sparing pelvic resections generally should be positioned laterally. Although other positions may be suitable for less extensive resections, the “sloppy” lateral approach (abdominolateral sacral portion) facilitates exposure of both intra- and extra-pelvic structures from the contralateral pubic to the sacral midline (Fig. 2). The ipsilateral leg should be prepped so that it can be manipulated to facilitate exposure and reduce tension on hip musculature. Surgical draping must be performed with considerable care to ensure that the midline may be accessed both anteriorly and posteriorly. Special care is required in draping the perineum. Unless specific access is required to the anus or genitalia, they can be excluded generally from the surgical field. The use of surgical staples or sutures to secure drapes in the perianal or perineal area is advised, as adhesive methods often fail, exposing the surgical field to potential contamination.
Figure 1 Defined pelvic resection types. A type IV resection is resection of the sacral ala.
R.L. McGough and A.W. Yasko
Figure 2 Standard “leg-draped free” set-up for pelvic resections. Note that the available exposure extends well past the abdominal (and sacral, not shown) midlines. (Color version of figure is available online.)
Surgical Approach The extent of surgical approach depends on the site of the tumor and the level of resection through the bony pelvis. Classically, a utilitarian approach to the pelvis, utilizing a conventional posterior flap (Figs. 3 and 4) as described by Enneking and Dunham1 has been used for most pelvic resections. This approach is based on that used for an external hemipelvectomy (hindquarter amputation) it relies on the creation of a very large posterior flap, combined with extensions of the incision along the ilioinguinal region, as well as medially into the perineum (Fig. 3). Tumors arising in the anterior portions of the pelvis may require more extensive anterior exposure, whereas tumors arising posteriorly near the sacroiliac (SI) joint may need proximal or posterior extensions to expose more of the sacrum and lumbosacral junc-
Figure 3 Diagrammatic drawing of the anterior portion of the extended ilioinguinal approach. The lateral T extension, as well as pubic and perineal extensions, are demonstrated. The conventional posterior flap, or utilitarian incision, also is demonstrated.
Pelvic resection
Figure 4 Diagrammatic drawing of the posterior portion of the extended ilioinguinal approach. The posterior flap, posterior extension, and sacral extension also are demonstrated.
tion. The basic scheme, however, relies on variations in an extended ilioinguinal approach. The extended ilioinguinal approach closely follows the contour of the anterior bony pelvis. It begins in the posterior ilium, at approximately the posterior–superior iliac spine (Fig. 5A). The incision then curves along the iliac crest toward the anterior–superior iliac spine (Fig. 5C). The inguinal arm of the incision follows the inguinal ligament to the pubic
261 tubercle. It then transverses the lower abdomen along the center of the pubis. Three different extensions to this incision are performed commonly. The first extension is performed anteriorly, traversing across the midline to the contralateral pubis along the ilioinguinal line (Fig. 3). This is commonly used for tumors of the anterior pelvis, where full exposure of both pubic bodies is necessary for either wide resection of the tumor or for exposure of uninvolved bone for plate fixation in a pelvic reconstruction. This extension allows mobilization of the rectus abdominis muscle insertions to gain access to the midline pelvic visceral and contralateral hemipelvis. The second extension of the ilioinguinal approach is performed posteriorly. The incision for this extension proceeds transversely from the posterior–superior iliac spine to the midline (Fig. 4). A second incision can be created along the midline longitudinally at right angles to this arm that can be extended cephalad, caudad, or both to provide wide exposure to the lower lumbar spine and sacrum (Fig. 4). The sacral extension is very useful in tumors that involve the sacroiliac joint, providing complete exposure to the ipsilateral sacral ala and SI joint. If the lumbar spine does not need to be accessed above L5, the posterior extension can be curved gently to provide wide access to the ipsilateral SI joint and posterior sacral ala.
Figure 5 The extended ilioinguinal approach with surface landmarks. (A) Posterior view with posterior–superior iliac spine and T extension. (B) Lateral view with anterior–superior iliac spine. The T extension is positioned almost directly lateral in this case. (C) Anterior view with anterior–superior iliac spine and pubic tubercle marked. No substantial pubic exposure was required in this case. (Color version of figure is available online.)
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262 A third extension to the approach involves creating an arm perpendicularly from the iliac crest region of the incision laterally and posteriorly (Figs. 3 and 5B). This extension can facilitate the exposure of the proximal femur and hip joint, especially in large individuals. The take off of this arm from the ilioinguinal incision is variable and depends on several factors, including the location of the underlying pathology, the type of reconstruction planned, and the surgeon’s preference.3 With tumors near the sciatic notch, the extension that begins on the iliac brim superior to the greater trochanter, and extends somewhat posteriorly, may allow better visualization of the sciatic notch, as well as creation of a more extensive buttock flap. Likewise, tumors with extensive extrapelvic extension anteriorly may require a more anteriorly based incision to allow better exposure of the proximal thigh, hip joint, and adductor muscle compartment. If pelvic reconstruction is planned, a direct lateral or anterolateral extension will facilitate exposure of the hip joint both anteriorly and posteriorly. Because the soft tissues around the hip are often ample and well vascularized, an extension in this lateral direction will generally give sufficient exposure of both the sciatic notch and the anterior hip musculature, and is often the extension of choice unless oncologic circumstances dictate otherwise. Irrespective of the incision placement and extent, the superficial dissection should be performed with care to minimize trauma to the skin and soft tissues. Superficial wound complications are common in pelvic resections, and attention to detail may reduce this prevalence. Full-thickness flaps should be maintained and the subcutaneous tissue should not be undermined unless necessary to preserve oncologic margins. Once fasciocutaneous flaps have been developed, the exposure can then be widened without risking dermal vascularity. The superficial dissection can be performed in phases to minimize decreases in core body temperature associated with large surface area exposure. A systematic approach to any pelvic surgery to extirpate tumors of the bony pelvis is preferred to minimize blood loss during the tedious portion of meticulous dissection of critical neurovascular structures. Because the tumors are often large and immobile, portions of the dissection invariably will be difficult. The intrapelvic lumbosacral plexus and iliac vessel dissections along the pelvic sidewall often require deliberate dissection. Blood loss can be minimized by approaching the intrapelvic dissection before the extrapelvic dissection. Frequently, the inguinal portion of the exposure is performed first. For this approach, the patient is rolled to a more supine position, making anatomic relations more familiar. This also allows exposure of the iliac vessels and the femoral nerve, which are obviously two key structures. By exposing the neurovascular bundle at the pelvic brim early in the procedure, these structures can then be followed in a proximal/ posterior direction, allowing the exposure to proceed in a logical manner from anteriorly to posteriorly, and manipulating the patient’s position accordingly.
Anatomic Dissections The exposures described in this section can be performed in any order as dictated by the location of the tumor and surgeon preference. As previously described, a wide exposure is
necessary to avoid inadvertent injury of intrapelvic structures. A systematic approach should maintain intraoperative rhythm and limit bleeding.
Abdominal Wall Deep dissection through the abdominal wall is a standard ilioinguinal approach. After the fasciocutaneous flaps have been created, the external inguinal ring is identified. A blunt dissecting instrument can then be placed through the ring, superficial to the spermatic cord (if present), and the external oblique fascia can be incised in the direction of its fibers. In a woman, the round ligament may then be safely ligated and transected. The spermatic cord in the male should be gently retracted medially by using a Penrose drain. The floor of the inguinal canal is then visible. In performing the ilioinguinal exposure, a cuff of tissue should generally be maintained on top of the pubic rami, where possible. The fascial incisions should, however, be made as close to the inguinal ligament as possible to facilitate later closure. Tagging sutures left within the fascial layers can also aid in this. Care should be used in the division of the aponeurosis of the oblique abdominal muscles. The inferior epigastric artery and vein lie between the internal oblique and transversalis fasciae and often can be spared. This is desirable, as they are a primary blood supply to the rectus abdominis muscle. Medially, the rectus sheath and enthesis of the rectus must be divided from the pubic symphysis, allowing exposure to the retropubic space. Anteriorly, the femoral vessels are encountered laterally, and the circumflex iliac vessels lie along the iliac crest just deep to the insertion of the abdominal muscles. Several nerves are encountered in the superficial abdominal dissection. The ilioinguinal and anterior branch of the iliohypogastric nerves parallel the inguinal canal, and can be visualized after splitting the external oblique fascia. They may often be swept medially with the spermatic cord, and retracted with the abdominal wall and peritoneum. The genital branch of the genitofemoral nerve is encountered along the psoas major. It exits the fascia with the spermatic cord in the deep inguinal ring, and can therefore be retracted with these structures. The femoral branch is often ligated as the fascia is split lateral to the femoral ring. The lateral femoral cutaneous nerve of the thigh emerges from the deep fascia slightly anteriorly to the anterior–superior iliac spine and will be encountered as the abdominal wall dissection proceeds from the femoral triangle over the iliac crest (Fig. 6A). Preservation of this nerve often is possible and is certainly more likely if it is actively sought during abdominal wall dissection, and not inadvertently transected. Preservation of this structure is desirable, if possible, to prevent the occurrence of meralgia paresthetica.
Space of Retzius On completion of the abdominal exposure, the bladder is immediately evident in the surgical midline. The retropubic space of Retzius generally can be developed by blunt manual dissection and gentle retraction of the bladder posteriorly and superiorly. Manual dissection into the space of Retzius will lead to the confluence of the inferior pubic rami. At this point, the ability to palpate inferiorly will cease, as the blad-
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Figure 6 Intraoperative photograph of the superficial dissection. (A) The abdominal wall is retracted after being released from the iliac crest. The lateral femoral cutaneous nerve and iliacus are visible. (B) The iliacus has been freed from the inner table of the pelvis, allowing development of the posterior “middle” and “lateral” windows. (C) The iliacus is retracted medially. The sciatic notch is visible deep within the wound via the “lateral” window. (Color version of figure is available online.)
der is tethered inferiorly by the exiting urethra. The urethra penetrates the pelvic floor and sphincter urethrae immediately below the pubic rami. This region also requires gentle handling in males due to the plexus of vessels about the prostate, and to avoid urethral injury. Once the bladder is displaced posteriorly, and the pubic symphysis is identified, the dissection is carried laterally along the superior pubic ramus to widen the approach until the external iliac vessels are visualized.
Vascular Bundle and Obturator Foramen Proceeding laterally, the external iliac artery and vein are encountered. In the extra-pelvic region, these vessels are surrounded by the femoral sheath, which is confluent with the inguinal ligament. Dissection in this area should be performed with care, as numerous anastomotic branches occur. Systematic dissection should include secure ligation of all branches as they are encountered, to prevent inadvertent injury and hemorrhage. For the same reason, aggressive blunt or manual dissection in this area should be limited. As the iliac vessels are mobilized from the femoral sheath, a corona mortis or anastomosis between the external iliac and obturator vessels may be encountered. These anatomic variations have been observed in 8% to 30% of cadavers studied, and should be actively sought before the iliac vessels are lifted free of their sheath.
The vessels are easier to identify slightly caudad to the inguinal ligament, as the femoral sheath becomes thinner. The sheath should generally be opened from a caudad to cephalad direction, and the artery and vein dissected free from it. Working proximally, the inguinal ligament is then divided by necessity. Once the artery and vein are exposed proximal to the inguinal ligament, it is prudent to ensure vascular control by placing vessel loops around each structure, achieving a means to gain control in the event of inadvertent bleeding. The femoral sheath can then be left attached to the pubic ramus as a soft tissue margin. Retrograde dissection along the external iliac vessels within the pelvis along their medial aspect creates the plane between vessels and viscera. Once the vessels are mobilized to the level of the hypogastrics, medial retraction will allow improved exposure of the true pelvis and internal obturator ring anteriorly and pelvic sidewall posteriorly. The obturator internus and pelvic floor musculature may be visualized deep within the wound. Invariably, the obturator internus is excised with the resection specimen and requires no specific dissection. After the iliac vessels have been mobilized, the obturator neurovascular bundle may be exposed. The obturator vessels originate on the hypogastric vessels and traverse the true pelvis to the obturator ring. They generally require ligation both inside and outside the pelvis when it is necessary to include the
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anterior pelvis within the resection specimen to achieve adequate surgical margins.
Iliacus, Femoral Nerve, and Psoas The lateral plane of the intrapelvic dissection commonly is determined to be between the iliacus and psoas muscles. The femoral nerve is located in the plane between these two muscles, and can be found easily as the intermuscular interval is developed. Identification of the femoral nerve is followed by its mobilization proximally to the region of the posterior ilium and sacroiliac joint. Dissection cephalad to the pelvic rim is required for pelvic tumors that extend proximal from the posterior ilium. Development of the iliopsoas interval allows the psoas major muscle to be retracted medially with the genitofemoral nerve. This dissection facilitates access to the posterior pelvic “windows” similar to the anterior pelvic windows described in a standard ilioinguinal approach. The iliacus muscle originates on the inner portion of the iliac crest, fills the iliac fossa, and inserts with the psoas on the lesser trochanter (Fig. 6A). It provides an anatomic barrier between tumors of the innominate bone and the pelvic viscera. As such, it is generally resected with the ilium in pelvic resections. For benign disease involving the ilium or supra-acetabular region, the iliacus muscle may be elevated from its origin and retracted medially (Fig. 6B), creating a subperiosteal, lateral window (Fig. 6C). When the iliacus is used as a soft tissue margin, as in most pelvic resections, a middle window between the iliacus and psoas major allows access to the posterior ilium, anterior SI joint, sacral ala, and L5 nerve root, which courses along the sacral ala medial to the SI joint. The psoas muscle also may be retracted laterally, and a medial window developed. This allows access to the midline viscera, lumbosacral plexus, and sacral foramina. The psoas muscle fascia may be incised to facilitate its mobilization. The psoas muscle also may be resected segmentally to improve exposure. Psoas muscle transection or resection will connect the middle and medial windows, which will widen the posterior exposure, but at a cost of hip flexion power.
Anterior SI Joint and L5 Nerve Root Mobilization of the psoas major and femoral nerve posteriorly completes the anterior intrapelvic dissection, and allows exposure of both posterior and caudal structures. Once the psoas is mobilized, the L5 nerve root will be visualized anterior to the sacral ala (Fig. 7). The L5 root runs in a longitudinal direction adjacent to the SI joint and is the primary landmark for identification of the sacral ala. The L5 nerve root should be handled with extreme care during its dissection, as it is prone to neurapraxia even with gentle handling. A venous plexus predictably is encountered immediately anterior to the nerve. Ligation of the vessels will facilitate mobilization of the nerve. Proceeding caudally, we can note that the nerve will join with S1 to form the lumbosacral plexus and distally the sciatic nerve at the inner sciatic notch (Fig. 7). This dissection may be challenging when tumors arise in the posterior ilium with intrapelvic extension. The L5 nerve root cannot be retracted for any appreciable distance. However, its position must be carefully noted because the posterior osteotomy will be performed in its vicin-
Figure 7 Pelvic neural anatomy after the sacrum has been cut and the hemipelvis removed. The three major pelvic nerves are visible, along with the L5 root (anterior to the sacroiliac joint) contribution to the sciatic nerve. (Color version of figure is available online.)
ity. The location for the posterior osteotomy depends on the tumor’s extent on preoperative imaging studies. Often the posterior osteotomy is made through the sacral ala due to extension of tumor to the SI joint. In periacetabular tumors, however, a portion of the ilium can often be spared, and therefore the posterior osteotomy may be made through the posterior ilium lateral to or through the SI joint. The L5 nerve root runs across the SI joint inferiorly and passes laterally and superiorly through the greater sciatic notch.
Quadrilateral Lamina, Hypogastric Plexus, and Internal Sciatic Notch The deep dissection in the true pelvis is often the most challenging aspect of any pelvic resection. The intrapelvic dissection to expose the sciatic notch can be complicated by hemorrhage from the gluteal vessels. Access is restricted within the true pelvis. This is true, especially in male patients who generally have a much narrower pelvic outlet. The depth of the dissection and conical shape of the pelvis adds to the challenge of mobilizing the delicate neurovascular structures through the sciatic notch. The hypogastric artery and vein lie posteriorly along the pelvic floor, providing numerous small vessels to the pelvic viscera. Most important for orthopaedic surgeons are the superior and inferior gluteal vessels, which provide the blood supply to the posterior soft tissue flap. Inadvertent ligation, iatrogenic damage, or thrombosis to these vessels can compromise perfusion to the gluteal musculature. They can be ligated if necessary. The lumbosacral roots course posteromedially to the gluteal vessels. Caudally, the deep intrapelvic dissection along the pelvic sidewall and across the quadrilateral lamina generally is straight forward, and can often be performed bluntly. The internal iliac vessels generally have no branches to the pelvic sidewall. A large intrapelvic soft tissue mass arising from an acetabular tumor may compromise this dissection. Exposure of the posterior aspect of an intrapelvic mass may not be achievable until the pelvis is abducted following osteotomies. This dissection joins the anterior dissection at the obturator vessels.
Pelvic resection
Hip Flexors and Hip Joint With the intrapelvic dissection near completion, attention can be turned to the extrapelvic dissection. Although providing outstanding intrapelvic exposure, an extended ilioinguinal approach does not necessarily provide adequate extrapelvic exposure for all patients. Clear exposure of the hip joint, external obturator region, sciatic nerve, and sciatic notch may require a lateral extension of the ilioinguinal incision as previously described. After fasciocutaneous flaps are created, the proximal anterior thigh is exposed through release of the origins of the tensor fascia lata and sartorius muscles, and will reveal the direct head of the rectus femoris. The rectus femoris can be tagged and transected, revealing the anterior hip capsule, which may be incised along the femoral neck if an intraarticular resection is to be performed and at its base along the intertrochanteric line for extra-pelvic resections. The deep medial dissection along the inferior margin of the femoral neck exposes the extra-pelvic portion of the iliopsoas tendon, which may be preserved or transected as defined by the surgical margins. Dissection of the femoral vessels in the thigh may be required, depending on the tumor location, but they should be completely mobilized. The adductor muscle origins are released sequentially. Extrapelvic ligation of the obturator neurovascular bundle is performed more easily after the pelvic osteotomies have been made and the hemipelvis can be elevated from the wound.
Buttock, Posterior SI Joint, Paraspinal Musculature, and External Sciatic Notch Unless the gluteus maximus is involved with extrapelvic tumor, it should be elevated from the posterior ilium and sacrum with the fasciocutaneous flap, improving blood supply to the area. The flap is developed posteriorly to the posterior– superior iliac spine, thus releasing the entire gluteus maximus origin. Releasing its insertion can extend the exposure inferiorly along the course of the sciatic nerve. After release of the maximus origin, dissection can be continued posteriorly along the posterior aspect of the ilium where the quadratus lumborum muscle can be transected near its insertion onto the posterior ilium. The medial dissection along the posterior ilium will reveal the L5 transverse process. The dissection can then be turned caudally and the iliolumbar ligament transected providing exposure of the posterior SI joint and sacral ala. The superior aspect of the posterior osteotomy site then can be marked. The gluteus medius and minimus cover the outer table of the pelvis in a manner similar to that of the iliacus on the inside. Generally, some portion of the abductor muscles is retained as a soft tissue margin on the outer table of the ilium. The extent of gluteal musculature that can be preserved depends on the extrapelvic soft tissue extension of the tumor. The piriformis can be divided revealing the greater sciatic notch, gluteal vessels and sciatic nerve. The remaining short external rotators of the hip can be released near the femur if necessary. Sciatic notch exposure establishes access to the pudendal nerve and vessels that can be identified passing over the sacrospinous ligament and into the lesser sciatic notch. The sacrospinous ligament is transected sharply and the posterior portion of Alcock’s canal can be developed.
265 Further dissection along the ischium and inferior pubic ramus often requires elevation of the resection specimen. To mobilize the ischium, the hamstring origins are released from the ischial tuberosity.
Osteotomies The sequence and timing of the pelvic osteotomies are predicated on the particular needs of the surgeon to gain access to specific areas of the pelvis to complete the resection. Because of the conical shape of the pelvis, one or more osteotomies can be performed to allow better mobilization of the specimen and therefore better visualization of deep structures. The pelvis is highly vascular; however, and cuts through the innominate bone and sacrum often can initiate continuous bleeding. Delivery of the specimen from the wound and the application of hemostatic agents usually control bleeding along the bony surfaces. The location of the anterior pelvic osteotomy depends on the extent of tumor within the anterior pelvis. Classically it is made through the fibrocartilage disc of the pubic symphysis, although the level can be extended across midline through the contralateral pubis or obturator foramen. In sectioning the symphysis pubis, blunt dissection is performed through the Space of Retzius, and a plane is developed between the bone and the arcuate ligament inferiorly. The urethra lies only a few millimeters beneath the arcuate ligament, so dissection is kept as close to the bone as possible, as long as this is oncologically safe. A blunt Satinsky clamp is then introduced into the developed plane, and bluntly passed from inside the pelvis to outside, being careful to stay close to the pubis. A Gigli saw is then used to transect the pelvic ring anteriorly. The anterior cut can allow increased hemipelvic motion through the SI joint, and may improve posterior exposure. For this reason, it may be performed earlier in the procedure if the posterior pelvic exposure is particularly difficult to achieve. The pelvis also must be freed at the hip joint. This may involve disarticulation of the femoral head for intraarticular resections or osteotomy of the base of the femoral neck for extraarticular resections. The level of the femoral neck transection is predicated on evidence of intraarticular extension of tumor. Osteotomy of the femoral neck allows the proximal femur to be retracted laterally, and improves anterior extrapelvic exposure. The posterior pelvic osteotomy can be performed through the sacral ala or SI joint depending on the extent of the tumor. The L5 nerve root provides a consistent landmark to guide the placement of the osteotomy either medial or lateral to the L5 nerve. Adequate exposure of the osteotomy site must be achieved both inside and outside the pelvis. The full extent of the SI joint from its cranial to caudal aspect should be visualized so the course of the L5 nerve root can be protected along its course into the sciatic notch (Fig. 7). The posterior osteotomy is performed usually from within the pelvis. When all three osteotomies are completed the hemipelvis can often be lifted or rotated to allow bone wax to be placed on the cut surfaces.
Pelvic Floor, Adductor Muscles, and Hamstring Origin Completing the pelvic osteotomies allows the hemipelvis to be mobilized to a much greater degree, allowing improved
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266 dissection of the perineal structures. Care should be taken to avoid overly vigorous pelvic retraction, as the femoral nerve is often stretched across the pelvic brim, and can easily develop a neurapraxia. Internal rotation of the pelvis allows improved posterior exposure, and the hamstring origin and sacrotuberous ligament can be sharply transected using this maneuver. The pudendal nerve is mobilized along the inferior pubic ramus, and allowed to fall medially. Likewise, flexion of the bone in the sagittal plane brings the adductors and pelvic floor musculature into better view. These can then be sectioned, and the obturator bundle can be ligated, if not previously done outside the pelvis. The pelvic floor is the most difficult portion to visualize. Care must be taken when dissecting medially along the inferior pubic ramus, as the urethra can be damaged inadvertently. The hemipelvis can be gently lifted and disengaged from the femoral nerve and iliac vessels. This brings the remaining pelvic floor into view, allowing safe transection and removal of the hemipelvis.
Pelvic Reconstruction and Closure After the bony specimen is removed, it is examined grossly. Bone margins can be inspected visually. Hemostasis will be required, and should be obtained in a systematic and thorough manner. Bleeding from the hypogastric and gluteal vessels can often be encountered. The perivesicle vasculature is a common source of bleeding that is difficult to control. Pelvic bone reconstruction can be accomplished using a number of methods. Prosthetic, alloprosthetic, and osteoarticular reconstructive methods have all been described. The
techniques, indications, and complications of these methods are beyond the scope of this work. Suction drains should be placed within the deep pelvic space, as well as more superficially, depending on the reconstruction used. Closure of the deep fascia must be meticulous to avoid complications. The fascia of the thigh musculature is closed directly to the fascia of the abdominal muscles, creating a new, nonanatomic, myofascial wall. Poor soft tissue closure will lead to dehiscence, a major cause of complications including seroma formation, infection, and abdominal hernias. If adequate closure of dead space cannot be accomplished due to soft tissue resection requirements, plastic surgical flap coverage should be considered at the time of primary closure.
Conclusion Pelvic resections are difficult, time-consuming operations that carry the risk of significant intraoperative morbidity. They require knowledge of the pelvic anatomy, a systematic surgical approach, and meticulous surgical technique to minimize complications.
References 1. Enneking WF, Dunham WK: Resection and reconstruction for primary neoplasms involving the innominate bone. J Bone Joint Surg 60A:731746, 1978 2. Bickels J, Malawer M: Pelvic resections (internal hemipelvectomies), in Malawer MM, Sugarbaker PH (eds): Musculoskeletal Cancer Surgery. Dordrecht, The Netherlands, Kluwer, 2001, pp 405-414 3. Conrad EU, Springfield D, Peabody TD: Pelvis, in Simon MA, Springfield D (eds): Surgery for Bone and Soft-Tissue Tumors. Philadelphia, PA, Lippincot-Raven, 1998, pp 323-341
T
he surgical management of tumors of the bony pelvis is a challenge for the orthopedic oncologist. As with tumors of the appendicular skeleton, limb-sparing techniques currently predominate among the varied procedures for the treatment for tumors of the pelvis. The extent of the exposure and the appropriate surgical planes of dissection are determined by the type of pelvic resection performed. The formal classification of the types of limb-sparing pelvic resections described by Enneking and Dunham in 1978 provides the basis for the surgical oncologic approaches to malignant tumors (Fig. 1).1 A limited resection, type I (iliac wing only), with osteotomies through the iliac neck and sacroiliac joint commonly can be performed with limited pubic or perineal exposure.2 On the contrary, resection of the entire hemipelvis (types I, II, III, IV) requires full pelvic exposure with a midline exposure of the sacrum as well. The type of resection and, therefore, exposure, is dictated by the tumor extent. For the purposes of this discussion, a full pelvic exposure will be detailed. The
*Department of Orthopaedic Surgery, The University of Pittsburgh School of Medicine, Pittsburgh, PA. †Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX. Address reprint requests to Alan W. Yasko, MD, Professor, Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 444, Houston, TX 77030. E-mail: [email protected]
1048-6666/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2004.11.002
components of the exposure pertinent to the anatomic region to be resected can be selected from their description
Surgical Preparation Preoperative Planning Attention to detail in the preoperative planning stage is critically important to the success of the surgery. Appropriate diagnostic imaging with computed tomography and/or magnetic resonance imaging (MRI) is necessary to delineate the bone and soft tissue extent of the tumor and its relationship to the major blood vessels, nerves, and pelvic viscera. Magnetic resonance imaging is indispensable for the evaluation of the relationship of tumor and intra- and extrapelvic structures. Key structures to note include the iliac vessels and femoral nerve anteriorly and the lumbosacral plexus posteriorly. The MRI also will demonstrate the extent of the tumor within the bone and in the adjacent soft tissues. The extent of intra- and extrapelvic muscle that will be resected can also be determined preoperatively. Computed tomography is complementary to the MRI and provides information regarding the tumor and superior pelvic bone detail.
Intraoperative Set-Up Although in most pelvic resections the peritoneum will not be entered, a standard bowel prep before surgery will decrease bacterial counts in the event of an inadvertent enter259
260 otomy and decrease the volume of bowel contents thereby improving the space available within the pelvis. The intraoperative set up for pelvic resection requires substantial monitoring and care. After anesthetic induction and appropriate endotracheal intubation, placement of ureteral stent(s) is beneficial to aid the identification of the ureter(s), to reduce the potential for injury. Appropriate invasive monitoring with both intravenous and intraarterial access should be obtained, and central venous lines should be strongly considered for both access and monitoring purposes. Patients undergoing limb-sparing pelvic resections generally should be positioned laterally. Although other positions may be suitable for less extensive resections, the “sloppy” lateral approach (abdominolateral sacral portion) facilitates exposure of both intra- and extra-pelvic structures from the contralateral pubic to the sacral midline (Fig. 2). The ipsilateral leg should be prepped so that it can be manipulated to facilitate exposure and reduce tension on hip musculature. Surgical draping must be performed with considerable care to ensure that the midline may be accessed both anteriorly and posteriorly. Special care is required in draping the perineum. Unless specific access is required to the anus or genitalia, they can be excluded generally from the surgical field. The use of surgical staples or sutures to secure drapes in the perianal or perineal area is advised, as adhesive methods often fail, exposing the surgical field to potential contamination.
Figure 1 Defined pelvic resection types. A type IV resection is resection of the sacral ala.
R.L. McGough and A.W. Yasko
Figure 2 Standard “leg-draped free” set-up for pelvic resections. Note that the available exposure extends well past the abdominal (and sacral, not shown) midlines. (Color version of figure is available online.)
Surgical Approach The extent of surgical approach depends on the site of the tumor and the level of resection through the bony pelvis. Classically, a utilitarian approach to the pelvis, utilizing a conventional posterior flap (Figs. 3 and 4) as described by Enneking and Dunham1 has been used for most pelvic resections. This approach is based on that used for an external hemipelvectomy (hindquarter amputation) it relies on the creation of a very large posterior flap, combined with extensions of the incision along the ilioinguinal region, as well as medially into the perineum (Fig. 3). Tumors arising in the anterior portions of the pelvis may require more extensive anterior exposure, whereas tumors arising posteriorly near the sacroiliac (SI) joint may need proximal or posterior extensions to expose more of the sacrum and lumbosacral junc-
Figure 3 Diagrammatic drawing of the anterior portion of the extended ilioinguinal approach. The lateral T extension, as well as pubic and perineal extensions, are demonstrated. The conventional posterior flap, or utilitarian incision, also is demonstrated.
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Figure 4 Diagrammatic drawing of the posterior portion of the extended ilioinguinal approach. The posterior flap, posterior extension, and sacral extension also are demonstrated.
tion. The basic scheme, however, relies on variations in an extended ilioinguinal approach. The extended ilioinguinal approach closely follows the contour of the anterior bony pelvis. It begins in the posterior ilium, at approximately the posterior–superior iliac spine (Fig. 5A). The incision then curves along the iliac crest toward the anterior–superior iliac spine (Fig. 5C). The inguinal arm of the incision follows the inguinal ligament to the pubic
261 tubercle. It then transverses the lower abdomen along the center of the pubis. Three different extensions to this incision are performed commonly. The first extension is performed anteriorly, traversing across the midline to the contralateral pubis along the ilioinguinal line (Fig. 3). This is commonly used for tumors of the anterior pelvis, where full exposure of both pubic bodies is necessary for either wide resection of the tumor or for exposure of uninvolved bone for plate fixation in a pelvic reconstruction. This extension allows mobilization of the rectus abdominis muscle insertions to gain access to the midline pelvic visceral and contralateral hemipelvis. The second extension of the ilioinguinal approach is performed posteriorly. The incision for this extension proceeds transversely from the posterior–superior iliac spine to the midline (Fig. 4). A second incision can be created along the midline longitudinally at right angles to this arm that can be extended cephalad, caudad, or both to provide wide exposure to the lower lumbar spine and sacrum (Fig. 4). The sacral extension is very useful in tumors that involve the sacroiliac joint, providing complete exposure to the ipsilateral sacral ala and SI joint. If the lumbar spine does not need to be accessed above L5, the posterior extension can be curved gently to provide wide access to the ipsilateral SI joint and posterior sacral ala.
Figure 5 The extended ilioinguinal approach with surface landmarks. (A) Posterior view with posterior–superior iliac spine and T extension. (B) Lateral view with anterior–superior iliac spine. The T extension is positioned almost directly lateral in this case. (C) Anterior view with anterior–superior iliac spine and pubic tubercle marked. No substantial pubic exposure was required in this case. (Color version of figure is available online.)
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262 A third extension to the approach involves creating an arm perpendicularly from the iliac crest region of the incision laterally and posteriorly (Figs. 3 and 5B). This extension can facilitate the exposure of the proximal femur and hip joint, especially in large individuals. The take off of this arm from the ilioinguinal incision is variable and depends on several factors, including the location of the underlying pathology, the type of reconstruction planned, and the surgeon’s preference.3 With tumors near the sciatic notch, the extension that begins on the iliac brim superior to the greater trochanter, and extends somewhat posteriorly, may allow better visualization of the sciatic notch, as well as creation of a more extensive buttock flap. Likewise, tumors with extensive extrapelvic extension anteriorly may require a more anteriorly based incision to allow better exposure of the proximal thigh, hip joint, and adductor muscle compartment. If pelvic reconstruction is planned, a direct lateral or anterolateral extension will facilitate exposure of the hip joint both anteriorly and posteriorly. Because the soft tissues around the hip are often ample and well vascularized, an extension in this lateral direction will generally give sufficient exposure of both the sciatic notch and the anterior hip musculature, and is often the extension of choice unless oncologic circumstances dictate otherwise. Irrespective of the incision placement and extent, the superficial dissection should be performed with care to minimize trauma to the skin and soft tissues. Superficial wound complications are common in pelvic resections, and attention to detail may reduce this prevalence. Full-thickness flaps should be maintained and the subcutaneous tissue should not be undermined unless necessary to preserve oncologic margins. Once fasciocutaneous flaps have been developed, the exposure can then be widened without risking dermal vascularity. The superficial dissection can be performed in phases to minimize decreases in core body temperature associated with large surface area exposure. A systematic approach to any pelvic surgery to extirpate tumors of the bony pelvis is preferred to minimize blood loss during the tedious portion of meticulous dissection of critical neurovascular structures. Because the tumors are often large and immobile, portions of the dissection invariably will be difficult. The intrapelvic lumbosacral plexus and iliac vessel dissections along the pelvic sidewall often require deliberate dissection. Blood loss can be minimized by approaching the intrapelvic dissection before the extrapelvic dissection. Frequently, the inguinal portion of the exposure is performed first. For this approach, the patient is rolled to a more supine position, making anatomic relations more familiar. This also allows exposure of the iliac vessels and the femoral nerve, which are obviously two key structures. By exposing the neurovascular bundle at the pelvic brim early in the procedure, these structures can then be followed in a proximal/ posterior direction, allowing the exposure to proceed in a logical manner from anteriorly to posteriorly, and manipulating the patient’s position accordingly.
Anatomic Dissections The exposures described in this section can be performed in any order as dictated by the location of the tumor and surgeon preference. As previously described, a wide exposure is
necessary to avoid inadvertent injury of intrapelvic structures. A systematic approach should maintain intraoperative rhythm and limit bleeding.
Abdominal Wall Deep dissection through the abdominal wall is a standard ilioinguinal approach. After the fasciocutaneous flaps have been created, the external inguinal ring is identified. A blunt dissecting instrument can then be placed through the ring, superficial to the spermatic cord (if present), and the external oblique fascia can be incised in the direction of its fibers. In a woman, the round ligament may then be safely ligated and transected. The spermatic cord in the male should be gently retracted medially by using a Penrose drain. The floor of the inguinal canal is then visible. In performing the ilioinguinal exposure, a cuff of tissue should generally be maintained on top of the pubic rami, where possible. The fascial incisions should, however, be made as close to the inguinal ligament as possible to facilitate later closure. Tagging sutures left within the fascial layers can also aid in this. Care should be used in the division of the aponeurosis of the oblique abdominal muscles. The inferior epigastric artery and vein lie between the internal oblique and transversalis fasciae and often can be spared. This is desirable, as they are a primary blood supply to the rectus abdominis muscle. Medially, the rectus sheath and enthesis of the rectus must be divided from the pubic symphysis, allowing exposure to the retropubic space. Anteriorly, the femoral vessels are encountered laterally, and the circumflex iliac vessels lie along the iliac crest just deep to the insertion of the abdominal muscles. Several nerves are encountered in the superficial abdominal dissection. The ilioinguinal and anterior branch of the iliohypogastric nerves parallel the inguinal canal, and can be visualized after splitting the external oblique fascia. They may often be swept medially with the spermatic cord, and retracted with the abdominal wall and peritoneum. The genital branch of the genitofemoral nerve is encountered along the psoas major. It exits the fascia with the spermatic cord in the deep inguinal ring, and can therefore be retracted with these structures. The femoral branch is often ligated as the fascia is split lateral to the femoral ring. The lateral femoral cutaneous nerve of the thigh emerges from the deep fascia slightly anteriorly to the anterior–superior iliac spine and will be encountered as the abdominal wall dissection proceeds from the femoral triangle over the iliac crest (Fig. 6A). Preservation of this nerve often is possible and is certainly more likely if it is actively sought during abdominal wall dissection, and not inadvertently transected. Preservation of this structure is desirable, if possible, to prevent the occurrence of meralgia paresthetica.
Space of Retzius On completion of the abdominal exposure, the bladder is immediately evident in the surgical midline. The retropubic space of Retzius generally can be developed by blunt manual dissection and gentle retraction of the bladder posteriorly and superiorly. Manual dissection into the space of Retzius will lead to the confluence of the inferior pubic rami. At this point, the ability to palpate inferiorly will cease, as the blad-
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Figure 6 Intraoperative photograph of the superficial dissection. (A) The abdominal wall is retracted after being released from the iliac crest. The lateral femoral cutaneous nerve and iliacus are visible. (B) The iliacus has been freed from the inner table of the pelvis, allowing development of the posterior “middle” and “lateral” windows. (C) The iliacus is retracted medially. The sciatic notch is visible deep within the wound via the “lateral” window. (Color version of figure is available online.)
der is tethered inferiorly by the exiting urethra. The urethra penetrates the pelvic floor and sphincter urethrae immediately below the pubic rami. This region also requires gentle handling in males due to the plexus of vessels about the prostate, and to avoid urethral injury. Once the bladder is displaced posteriorly, and the pubic symphysis is identified, the dissection is carried laterally along the superior pubic ramus to widen the approach until the external iliac vessels are visualized.
Vascular Bundle and Obturator Foramen Proceeding laterally, the external iliac artery and vein are encountered. In the extra-pelvic region, these vessels are surrounded by the femoral sheath, which is confluent with the inguinal ligament. Dissection in this area should be performed with care, as numerous anastomotic branches occur. Systematic dissection should include secure ligation of all branches as they are encountered, to prevent inadvertent injury and hemorrhage. For the same reason, aggressive blunt or manual dissection in this area should be limited. As the iliac vessels are mobilized from the femoral sheath, a corona mortis or anastomosis between the external iliac and obturator vessels may be encountered. These anatomic variations have been observed in 8% to 30% of cadavers studied, and should be actively sought before the iliac vessels are lifted free of their sheath.
The vessels are easier to identify slightly caudad to the inguinal ligament, as the femoral sheath becomes thinner. The sheath should generally be opened from a caudad to cephalad direction, and the artery and vein dissected free from it. Working proximally, the inguinal ligament is then divided by necessity. Once the artery and vein are exposed proximal to the inguinal ligament, it is prudent to ensure vascular control by placing vessel loops around each structure, achieving a means to gain control in the event of inadvertent bleeding. The femoral sheath can then be left attached to the pubic ramus as a soft tissue margin. Retrograde dissection along the external iliac vessels within the pelvis along their medial aspect creates the plane between vessels and viscera. Once the vessels are mobilized to the level of the hypogastrics, medial retraction will allow improved exposure of the true pelvis and internal obturator ring anteriorly and pelvic sidewall posteriorly. The obturator internus and pelvic floor musculature may be visualized deep within the wound. Invariably, the obturator internus is excised with the resection specimen and requires no specific dissection. After the iliac vessels have been mobilized, the obturator neurovascular bundle may be exposed. The obturator vessels originate on the hypogastric vessels and traverse the true pelvis to the obturator ring. They generally require ligation both inside and outside the pelvis when it is necessary to include the
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anterior pelvis within the resection specimen to achieve adequate surgical margins.
Iliacus, Femoral Nerve, and Psoas The lateral plane of the intrapelvic dissection commonly is determined to be between the iliacus and psoas muscles. The femoral nerve is located in the plane between these two muscles, and can be found easily as the intermuscular interval is developed. Identification of the femoral nerve is followed by its mobilization proximally to the region of the posterior ilium and sacroiliac joint. Dissection cephalad to the pelvic rim is required for pelvic tumors that extend proximal from the posterior ilium. Development of the iliopsoas interval allows the psoas major muscle to be retracted medially with the genitofemoral nerve. This dissection facilitates access to the posterior pelvic “windows” similar to the anterior pelvic windows described in a standard ilioinguinal approach. The iliacus muscle originates on the inner portion of the iliac crest, fills the iliac fossa, and inserts with the psoas on the lesser trochanter (Fig. 6A). It provides an anatomic barrier between tumors of the innominate bone and the pelvic viscera. As such, it is generally resected with the ilium in pelvic resections. For benign disease involving the ilium or supra-acetabular region, the iliacus muscle may be elevated from its origin and retracted medially (Fig. 6B), creating a subperiosteal, lateral window (Fig. 6C). When the iliacus is used as a soft tissue margin, as in most pelvic resections, a middle window between the iliacus and psoas major allows access to the posterior ilium, anterior SI joint, sacral ala, and L5 nerve root, which courses along the sacral ala medial to the SI joint. The psoas muscle also may be retracted laterally, and a medial window developed. This allows access to the midline viscera, lumbosacral plexus, and sacral foramina. The psoas muscle fascia may be incised to facilitate its mobilization. The psoas muscle also may be resected segmentally to improve exposure. Psoas muscle transection or resection will connect the middle and medial windows, which will widen the posterior exposure, but at a cost of hip flexion power.
Anterior SI Joint and L5 Nerve Root Mobilization of the psoas major and femoral nerve posteriorly completes the anterior intrapelvic dissection, and allows exposure of both posterior and caudal structures. Once the psoas is mobilized, the L5 nerve root will be visualized anterior to the sacral ala (Fig. 7). The L5 root runs in a longitudinal direction adjacent to the SI joint and is the primary landmark for identification of the sacral ala. The L5 nerve root should be handled with extreme care during its dissection, as it is prone to neurapraxia even with gentle handling. A venous plexus predictably is encountered immediately anterior to the nerve. Ligation of the vessels will facilitate mobilization of the nerve. Proceeding caudally, we can note that the nerve will join with S1 to form the lumbosacral plexus and distally the sciatic nerve at the inner sciatic notch (Fig. 7). This dissection may be challenging when tumors arise in the posterior ilium with intrapelvic extension. The L5 nerve root cannot be retracted for any appreciable distance. However, its position must be carefully noted because the posterior osteotomy will be performed in its vicin-
Figure 7 Pelvic neural anatomy after the sacrum has been cut and the hemipelvis removed. The three major pelvic nerves are visible, along with the L5 root (anterior to the sacroiliac joint) contribution to the sciatic nerve. (Color version of figure is available online.)
ity. The location for the posterior osteotomy depends on the tumor’s extent on preoperative imaging studies. Often the posterior osteotomy is made through the sacral ala due to extension of tumor to the SI joint. In periacetabular tumors, however, a portion of the ilium can often be spared, and therefore the posterior osteotomy may be made through the posterior ilium lateral to or through the SI joint. The L5 nerve root runs across the SI joint inferiorly and passes laterally and superiorly through the greater sciatic notch.
Quadrilateral Lamina, Hypogastric Plexus, and Internal Sciatic Notch The deep dissection in the true pelvis is often the most challenging aspect of any pelvic resection. The intrapelvic dissection to expose the sciatic notch can be complicated by hemorrhage from the gluteal vessels. Access is restricted within the true pelvis. This is true, especially in male patients who generally have a much narrower pelvic outlet. The depth of the dissection and conical shape of the pelvis adds to the challenge of mobilizing the delicate neurovascular structures through the sciatic notch. The hypogastric artery and vein lie posteriorly along the pelvic floor, providing numerous small vessels to the pelvic viscera. Most important for orthopaedic surgeons are the superior and inferior gluteal vessels, which provide the blood supply to the posterior soft tissue flap. Inadvertent ligation, iatrogenic damage, or thrombosis to these vessels can compromise perfusion to the gluteal musculature. They can be ligated if necessary. The lumbosacral roots course posteromedially to the gluteal vessels. Caudally, the deep intrapelvic dissection along the pelvic sidewall and across the quadrilateral lamina generally is straight forward, and can often be performed bluntly. The internal iliac vessels generally have no branches to the pelvic sidewall. A large intrapelvic soft tissue mass arising from an acetabular tumor may compromise this dissection. Exposure of the posterior aspect of an intrapelvic mass may not be achievable until the pelvis is abducted following osteotomies. This dissection joins the anterior dissection at the obturator vessels.
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Hip Flexors and Hip Joint With the intrapelvic dissection near completion, attention can be turned to the extrapelvic dissection. Although providing outstanding intrapelvic exposure, an extended ilioinguinal approach does not necessarily provide adequate extrapelvic exposure for all patients. Clear exposure of the hip joint, external obturator region, sciatic nerve, and sciatic notch may require a lateral extension of the ilioinguinal incision as previously described. After fasciocutaneous flaps are created, the proximal anterior thigh is exposed through release of the origins of the tensor fascia lata and sartorius muscles, and will reveal the direct head of the rectus femoris. The rectus femoris can be tagged and transected, revealing the anterior hip capsule, which may be incised along the femoral neck if an intraarticular resection is to be performed and at its base along the intertrochanteric line for extra-pelvic resections. The deep medial dissection along the inferior margin of the femoral neck exposes the extra-pelvic portion of the iliopsoas tendon, which may be preserved or transected as defined by the surgical margins. Dissection of the femoral vessels in the thigh may be required, depending on the tumor location, but they should be completely mobilized. The adductor muscle origins are released sequentially. Extrapelvic ligation of the obturator neurovascular bundle is performed more easily after the pelvic osteotomies have been made and the hemipelvis can be elevated from the wound.
Buttock, Posterior SI Joint, Paraspinal Musculature, and External Sciatic Notch Unless the gluteus maximus is involved with extrapelvic tumor, it should be elevated from the posterior ilium and sacrum with the fasciocutaneous flap, improving blood supply to the area. The flap is developed posteriorly to the posterior– superior iliac spine, thus releasing the entire gluteus maximus origin. Releasing its insertion can extend the exposure inferiorly along the course of the sciatic nerve. After release of the maximus origin, dissection can be continued posteriorly along the posterior aspect of the ilium where the quadratus lumborum muscle can be transected near its insertion onto the posterior ilium. The medial dissection along the posterior ilium will reveal the L5 transverse process. The dissection can then be turned caudally and the iliolumbar ligament transected providing exposure of the posterior SI joint and sacral ala. The superior aspect of the posterior osteotomy site then can be marked. The gluteus medius and minimus cover the outer table of the pelvis in a manner similar to that of the iliacus on the inside. Generally, some portion of the abductor muscles is retained as a soft tissue margin on the outer table of the ilium. The extent of gluteal musculature that can be preserved depends on the extrapelvic soft tissue extension of the tumor. The piriformis can be divided revealing the greater sciatic notch, gluteal vessels and sciatic nerve. The remaining short external rotators of the hip can be released near the femur if necessary. Sciatic notch exposure establishes access to the pudendal nerve and vessels that can be identified passing over the sacrospinous ligament and into the lesser sciatic notch. The sacrospinous ligament is transected sharply and the posterior portion of Alcock’s canal can be developed.
265 Further dissection along the ischium and inferior pubic ramus often requires elevation of the resection specimen. To mobilize the ischium, the hamstring origins are released from the ischial tuberosity.
Osteotomies The sequence and timing of the pelvic osteotomies are predicated on the particular needs of the surgeon to gain access to specific areas of the pelvis to complete the resection. Because of the conical shape of the pelvis, one or more osteotomies can be performed to allow better mobilization of the specimen and therefore better visualization of deep structures. The pelvis is highly vascular; however, and cuts through the innominate bone and sacrum often can initiate continuous bleeding. Delivery of the specimen from the wound and the application of hemostatic agents usually control bleeding along the bony surfaces. The location of the anterior pelvic osteotomy depends on the extent of tumor within the anterior pelvis. Classically it is made through the fibrocartilage disc of the pubic symphysis, although the level can be extended across midline through the contralateral pubis or obturator foramen. In sectioning the symphysis pubis, blunt dissection is performed through the Space of Retzius, and a plane is developed between the bone and the arcuate ligament inferiorly. The urethra lies only a few millimeters beneath the arcuate ligament, so dissection is kept as close to the bone as possible, as long as this is oncologically safe. A blunt Satinsky clamp is then introduced into the developed plane, and bluntly passed from inside the pelvis to outside, being careful to stay close to the pubis. A Gigli saw is then used to transect the pelvic ring anteriorly. The anterior cut can allow increased hemipelvic motion through the SI joint, and may improve posterior exposure. For this reason, it may be performed earlier in the procedure if the posterior pelvic exposure is particularly difficult to achieve. The pelvis also must be freed at the hip joint. This may involve disarticulation of the femoral head for intraarticular resections or osteotomy of the base of the femoral neck for extraarticular resections. The level of the femoral neck transection is predicated on evidence of intraarticular extension of tumor. Osteotomy of the femoral neck allows the proximal femur to be retracted laterally, and improves anterior extrapelvic exposure. The posterior pelvic osteotomy can be performed through the sacral ala or SI joint depending on the extent of the tumor. The L5 nerve root provides a consistent landmark to guide the placement of the osteotomy either medial or lateral to the L5 nerve. Adequate exposure of the osteotomy site must be achieved both inside and outside the pelvis. The full extent of the SI joint from its cranial to caudal aspect should be visualized so the course of the L5 nerve root can be protected along its course into the sciatic notch (Fig. 7). The posterior osteotomy is performed usually from within the pelvis. When all three osteotomies are completed the hemipelvis can often be lifted or rotated to allow bone wax to be placed on the cut surfaces.
Pelvic Floor, Adductor Muscles, and Hamstring Origin Completing the pelvic osteotomies allows the hemipelvis to be mobilized to a much greater degree, allowing improved
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266 dissection of the perineal structures. Care should be taken to avoid overly vigorous pelvic retraction, as the femoral nerve is often stretched across the pelvic brim, and can easily develop a neurapraxia. Internal rotation of the pelvis allows improved posterior exposure, and the hamstring origin and sacrotuberous ligament can be sharply transected using this maneuver. The pudendal nerve is mobilized along the inferior pubic ramus, and allowed to fall medially. Likewise, flexion of the bone in the sagittal plane brings the adductors and pelvic floor musculature into better view. These can then be sectioned, and the obturator bundle can be ligated, if not previously done outside the pelvis. The pelvic floor is the most difficult portion to visualize. Care must be taken when dissecting medially along the inferior pubic ramus, as the urethra can be damaged inadvertently. The hemipelvis can be gently lifted and disengaged from the femoral nerve and iliac vessels. This brings the remaining pelvic floor into view, allowing safe transection and removal of the hemipelvis.
Pelvic Reconstruction and Closure After the bony specimen is removed, it is examined grossly. Bone margins can be inspected visually. Hemostasis will be required, and should be obtained in a systematic and thorough manner. Bleeding from the hypogastric and gluteal vessels can often be encountered. The perivesicle vasculature is a common source of bleeding that is difficult to control. Pelvic bone reconstruction can be accomplished using a number of methods. Prosthetic, alloprosthetic, and osteoarticular reconstructive methods have all been described. The
techniques, indications, and complications of these methods are beyond the scope of this work. Suction drains should be placed within the deep pelvic space, as well as more superficially, depending on the reconstruction used. Closure of the deep fascia must be meticulous to avoid complications. The fascia of the thigh musculature is closed directly to the fascia of the abdominal muscles, creating a new, nonanatomic, myofascial wall. Poor soft tissue closure will lead to dehiscence, a major cause of complications including seroma formation, infection, and abdominal hernias. If adequate closure of dead space cannot be accomplished due to soft tissue resection requirements, plastic surgical flap coverage should be considered at the time of primary closure.
Conclusion Pelvic resections are difficult, time-consuming operations that carry the risk of significant intraoperative morbidity. They require knowledge of the pelvic anatomy, a systematic surgical approach, and meticulous surgical technique to minimize complications.
References 1. Enneking WF, Dunham WK: Resection and reconstruction for primary neoplasms involving the innominate bone. J Bone Joint Surg 60A:731746, 1978 2. Bickels J, Malawer M: Pelvic resections (internal hemipelvectomies), in Malawer MM, Sugarbaker PH (eds): Musculoskeletal Cancer Surgery. Dordrecht, The Netherlands, Kluwer, 2001, pp 405-414 3. Conrad EU, Springfield D, Peabody TD: Pelvis, in Simon MA, Springfield D (eds): Surgery for Bone and Soft-Tissue Tumors. Philadelphia, PA, Lippincot-Raven, 1998, pp 323-341