Hemipelvectomy: Modified Surgical Technique and Clinical Experiences From a Retrospective Study Jonathan P. Bray, MVSc CertSAS, MACVSc, MSc (Clin Onc), Diplomate ECVS Veterinary Teaching Hospital, Massey University, Palmerston North, New Zealand
Corresponding Author Jonathan Bray, MVSc CertSAS, MACVSc, MSc (Clin Onc), Diplomate ECVS, Veterinary Teaching Hospital, Massey University, Private Bag 11‐222, Palmerston North, New Zealand. E‐mail: [email protected] Submitted November 2012 Accepted September 2013 DOI:10.1111/j.1532-950X.2013.12085.x
Objective: To report a technique for hemipelvectomy surgery in the dog and cat. Study Design: Descriptive report. Animals: Dogs and cats. Methods: To describe patient selection and an anatomically based surgical technique for hemipelvectomy. Results: Surgery of the pelvis requires detailed anatomic knowledge of the pelvic region. Hemipelvectomy is a major surgical procedure with potential for substantial hemorrhage because of transection through large muscle groups and proximity to major vessels. The anatomic dissection may enable better adherence to principles of compartmental resection of tumors and reduced patient morbidity. Conclusions: When performed with appropriate care, preoperative planning, and good anesthesia support, hemipelvectomy can be performed safely and is effective for radical excision of various tumor types arising from or near the pelvis.
Hemipelvectomy enables effective management of tumors or functional abnormalities (e.g. fracture malunion) involving the pelvis or associated soft tissues.1–6 Although an entire hemi‐ pelvis can be resected, partial pelvectomy is usually adequate for removing tumors involving the pelvis, coxofemoral joint, or proximal aspect of the thigh. Other than occasional case reports and a small case series of 9 dogs and cats,1,2,7 details on a surgical technique for hemipelvectomy in the dog and cat were not published until 2008.4 The authors described hemipelvectomy as “an involved and aggressive surgery,” with a dissection that must be tailored to each specific case. Recently, members of the Veterinary Society of Surgical Oncology completed a multi‐institutional retrospective study that described clinical details and outcome of a cohort of 100 dogs and cats that had hemipelvectomy surgery for neoplastic disorders.8 Although survival times for many malignant mesenchymal tumors were good, local tumor recurrence rates of 19% were observed, with recurrence being associated with an increased rate of death and reduced overall survival. High rates of local recurrence are also a feature of human hemipelvectomy surgery because of local extension of tumor into adjacent pelvic structures, microscopic foci of tumor in otherwise normal tissue and widespread invasion into major pelvic veins.6 These findings support the need for careful surgical planning to ensure tumor resection can be accomplished without encroaching into the peritumoral environment. In this paper, a modification of a technique for hemipelvectomy reported by Kramer et al is described and perioperative experience gained from a multi‐institutional study is reported. More precise anatomic dissection of the pelvic musculature should enable better compartmental excision of neoplasms.9
SURGICAL PLANNING Tumor Staging After mass identification by palpation or diagnostic imaging, complete oncologic examination is critical. Thorough clinical staging with thoracic imaging and abdominal ultrasonography,10 or a whole‐body CT, should be performed as most tumors affecting the pelvis have metastatic potential.8 Cytologic or histopathologic diagnosis of the tumor should be obtained by fine needle aspiration or tru‐cut biopsy. The surgeon should carefully consider the biopsy technique in relation to the subsequent surgery to ensure the biopsy tract can be safely removed. Imaging Assessment Anatomic compartments such as fascial planes and bony structures provide inherent barriers to tumor spread.9 With careful planning, hemipelvectomy can facilitate pelvic limb amputation with preservation of an intact anatomic compartment around the tumor. Much of the information necessary for surgical planning can be obtained by coaxial imaging (CT, MRI) and is an essential element of presurgical management (Fig 1) Whereas MRI provides superior information compared with CT for soft tissue structures and the extent of reactive zone surrounding the tumor,11 adequate information on tissue compartments and barriers can still be obtained to enable surgical planning with CT alone. It is important for the patient to be positioned in the scanner so that the pelvic limb maintains a neutral configuration typical of a standing animal. If the limb is placed in a “frog‐
Veterinary Surgery 43 (2014) 19–26 © Copyright 2013 by The American College of Veterinary Surgeons
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Figure 1 MRI images (axial T2W and sagittal STIR views) of a canine fibrosarcoma within the soft tissues of the caudal thigh. Note the large tumor size, and the extensive reactive zone of inflammation and edema that surrounds the tumor. A caudal external hemipelvectomy would be recommended for compartmental excision of the tumor to ensure the reactive zone is not breached and remains completely contained by the resected compartment of tissue.
leg,” it can become difficult to map out the anatomic boundaries of the limb in relative to the tumor. A neutral limb position ensures the flexor and extensor muscle compartments can be fully evaluated relative to the tumor, and allows tumor resection to be confidently planned. Anatomic Resection Each individual has a unique presentation in terms of tumor type, location, and extent so the precise surgical considerations will differ between each.4 In human surgery, the term “external hemipelvectomy” is used to describe a procedure that also includes amputation of the pelvic limb; “internal hemipelvectomy” is used when the limb is preserved.3,6,12 Using this nomenclature, there are 6 major categories for hemipelvectomy in dogs (Fig 2). Total External Hemipelvectomy. Removal of the ipsilateral pelvic limb and hemi‐pelvis to the level of the pubic symphysis; the ilial wing is elevated at the sacroiliac junction. Partial sacrectomy (up to one‐third of the sacral body) may also be performed if necessary (personal communication: Dr. Nick Bacon, 2010). This approach may be considered for tumors affecting the ilium, ischium, or pubis where resection of the entire skeletal compartment is necessary. Caudal External Hemipelvectomy. Removal of the ipsilateral pelvic limb, acetabulum, and ischium wing, extending from just caudal to the sacroiliac joint and medially to the level
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of the pubic symphysis. This approach preserves a small section of ilial wing and the site of origin for the sartorius muscle, which is ideal for the closure of the abdominal wall. This approach may be considered for soft tissue tumors located caudal to the femur (e.g. within the flexor muscles) or for peripheral nerve sheath tumors. From the VSSO retrospective study, these locations comprise most clinical presentations.8 Good access to the entire lumbosacral nerve plexus and intervertebral foramen is possible with this approach. Cranial External Hemipelvectomy. Removal of the ipsilateral pelvic limb, acetabulum, and ilial wing, extending to the level of the pubic symphysis. This approach is ideal for soft tissue tumors located cranial to the femur (i.e. within the extensor muscles). This approach preserves the site of origin of the semimembranosus/semitendinosus muscles, which may be used for closure of the abdominal defect. Cranial Internal Hemipelvectomy (Iliectomy). Reserved for tumors confined to the surface of the ilial wing or sartorius muscle. This approach can potentially be performed without requiring amputation of the pelvic limb, depending on the local extent of the tumor. Caudal Internal Hemipelvectomy (Ischiectomy). Reserved for tumors confined to the ischium or semimembranosus/semitendinosus muscles. This approach can potentially be performed without requiring amputation of the pelvic limb, depending on the local extent of the tumor.
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Hemipelvectomy: Modified Surgical Technique
Figure 2 Hemipelvectomy techniques. External pelvectomy entails amputation of the ipsilateral pelvic limb, whereas internal hemipelvectomy enables functional limb sparing. (A) Total external hemipelvectomy; (B) caudal external hemipelvectomy; (C) cranial external hemipelvectomy; (D) cranial internal hemipelvectomy (iliectomy); (E) caudal internal hemipelvectomy (ischiectomy). (G) Middle internal or external hemipelvectomy (acetabulectomy). Although option B is perhaps the most common technique, consideration of tumor location and local invasiveness are important in surgical planning.
Middle Internal/External Hemipelvectomy (Acetabulectomy). Removal of the femoral head and acetabulum, often involving amputation of the ipsilateral limb. This approach is best reserved for tumors confined to the coxofemoral joint without extension into the surrounding tissues. In the cat, this approach has been described for management of fracture malunion causing fecal obstipation.1 Acetabulectomy could be performed without requiring amputation of the pelvic limb provided the tumor was confined completely to the coxofemoral joint, though some gait effect may be observed similar to femoral head ostectomy. Preoperative Considerations Hemipelvectomy is a major surgery with the potential for significant hemorrhage because of transection through large muscle groups and proximity to major vessels. Severe hemorrhage requiring transfusion or aggressive volume support may arise despite anatomic knowledge and sound surgical technique. Preparation of the patient for a potential blood transfusion should be made before surgery by perform-
ing a cross‐match or blood typing as appropriate for blood bank facilities available in the hospital. Anesthesia management should be performed as for a pelvic limb amputation with consideration for multi‐modal preemptive analgesia.13 Systemic opioids, in combination with either a morphine and/or lidocaine epidural, is effective in most instances. Non‐steroidal anti‐inflammatory drugs may be withheld until after the patient has recovered from surgery in case of hypotension during a prolonged surgery. Performing local nerve blocks with a combination of lidocaine and bupivacaine should be considered before transection of major nerves during surgery.10 In addition wound diffusion catheters may enable good postoperative pain relief.14 A negative suction drain can be used for managing dead space. A wide area of the limb and pelvic limb is prepared, extending medially to the level of the contralateral stifle, cranially to mid abdomen and dorsally across to the opposite coxofemoral joint. The anal canal should be evacuated and a purse string suture placed to protect against bowel evacuation during surgery. An indwelling urinary catheter should be placed to assist with recognition of the urethra during surgery.
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Hemipelvectomy is typically performed in lateral recumbency; however, oblique positioning may occasionally be helpful (e.g. for sciatic nerve root tumors requiring concurrent hemilaminectomy). When planning the incisions, consideration needs to be given to removing biopsy tracts, and to ensuring there is sufficient skin available for closure. Skin from the medial or lateral thigh, extending to the level of the stifle, ideally needs to be preserved to ensure a tension‐free skin closure can be accomplished. The location of the tumor, and/or the previous biopsy tract will usually determine which portion of skin can be preserved.
femoris muscle, and there are many musculocutaneous vascular branches penetrating into the hypodermis so this dissection is tedious. With the skin elevated, dissection continues caudally around the ischium, between the semitendinosus and ischiocavernosus muscles, staying medial to the sacrotuberous ligament. The muscles of the pelvic diaphragm (levator ani and lateral coccygeus) should remain in situ on the medial aspect of the dissection. The superficial gluteal muscle is transected along its length close to its dorsal origin. The lumbar fascia may also be incised cranially to expose the middle gluteal muscle (Fig 3). Limb Amputation
SURGICAL TECHNIQUE The following description outlines the dissection necessary for a total external hemipelvectomy or caudal external hemipelvectomy. Some extrapolation of the fundamental principles may be required if other variations of hemipelvectomy are required. The goal of surgery should be to completely excise the neoplasm with at least 1 intact fascial plane about the entire circumference of the tumor. Medial Dissection Dissection begins medially, with a curvilinear incision extending along the medial thigh from the inguinal fold to the ischium. The sartorius muscle (both cranial and caudal bellies) is transected at the level of the stifle and elevated en bloc from the limb, preserving its attachment on the ilial wing. The branch of the descending genicular artery is ligated as it passes ventral to the muscle distally. The superficial circumflex artery and vein may need to ligated more proximally to allow elevation of the muscle from the femoral artery. The muscle is kept moist by application of saline (0.9% NaCl) solution soaked swabs. The skin is elevated to expose the midline of the pubis using self‐retaining retractors to maintain exposure. The medial thigh muscles (adductor/gracilis/pectineus) are incised on the midline down to the pubic symphysis; a faint fascial aponeurosis defines the midline at this site. The abdominal muscles are cut as they insert on the pubis and retracted cranially, elevating the muscle from the ilial wing until the iliopsoas muscle is visible and the ventral surface of the ilial wing is palpable. The external iliac artery and vein are isolated and double ligated, before division. The iliopsoas muscles are isolated and transected with a scalpel blade. Typically, this can be performed as close to the tendinous insertion on the femoral neck as possible. The ventral surface of the ilial wing is exposed with periosteal elevators.
Dissection focus now shifts cranially to the previously exposed ventral surface of the ilial wing. If a total hemipelvectomy is being performed, the sacrum can be exposed and the ilium elevated by inserting an osteotome at the sacroiliac joint and separating with a mallet. If necessary, a small ventral edge of ilium needs to be osteotomized to preserve the origin of the elevated sartorius muscle. If a mid‐to‐caudal pelvectomy is being performed, the medial gluteal muscle can be partially elevated from the ilium to allow the ilium to be cut with an oscillating saw immediately caudal to the sacroiliac joint. The pubic symphysis is cut with an oscillating saw or osteotome (Fig 4). As the limb is gently elevated from the body, remaining medial muscle attachments will be exposed and can be gently incised. The internal obturator muscle may be an important medial barrier for some tumors that have penetrated into the pelvic canal via the obturator foramen. In this instance, care needs to be taken to ensure the tumor capsule is not breached and the internal obturator muscle is removed en bloc with the amputated limb (Fig 5). With the limb free of muscular attachments, it will now be tethered by nerve branches from the lumbosacral plexus only
Lateral Dissection A curvilinear skin incision is made on the lateral surface of the thigh, joining the previous medial incisions. The skin is elevated proximally to expose the lumbar fascia above the coxofemoral joint. The skin is in close contact with the biceps
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Figure 3 Dorsolateral dissection. The superficial gluteal and tensor fascia lata muscles ( ) are transected along its length close to its dorsal origin. The lumbar fascia may also be incised cranially to expose the middle gluteal muscle. The ischiocavernosus muscle is transected from its origin on the ischium ( ) (Dorsal view, with cranial to left of picture).
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Hemipelvectomy: Modified Surgical Technique
should be injected with a long‐acting local anesthetic (e.g. a mixture of lidocaine and bupivacaine) proximal to the site of transection.13 For peripheral nerve sheath tumors, care is needed to map out all of the lumbosacral plexus and trace each nerve branch to the level of the intervertebral foramen at L6, L7, and S1 (Fig 6) Each nerve is then cut sharply as it enters the foramen. The remaining section of iliopsoas muscle may need to be elevated to expose the most cranial foramen. Closure
Figure 4 Ventral dissection. The sartorius muscle (both cranial and caudal bellies) has been elevated en bloc from its insertion at the level of the stifle and wrapped in saline solution soaked swabs to keep moist during the remaining dissection ( ). The medial thigh muscles (adductor/ gracilis/pectineus) have been incised on the midline to the pubic symphysis, which has been cut with an oscillating saw or osteotome ( ). During osteotomy, it is useful to place a periosteal elevator in the pelvic canal to protect the urethra and rectum.
so the assistant needs to support the weight of the limb. For most tumors, the nerves can be transected close to the limb; pudendal nerve branches (more caudally located) should be preserved where possible. Before transection, the nerve sheath
The wound is lavaged and any remaining bleeding vessels managed. If postoperative radiation is being considered, metal hemoclips should be placed about the periphery of the dissection field before closure.15 The sartorius muscle can be unwrapped from its moist swab and draped across the defect (Fig 7). It is then secured to the abdominal muscle, adductor (with bone tunnels to the symphysis if necessary) and pelvic diaphragm to close the exposed abdomen and pelvic canal. Muscular defects in the caudolateral abdominal wall and pelvic diaphragm usually exist after resection of the entire hemi‐ pelvis. In rare cases, a prosthetic mesh may be needed. Care is taken with the remaining closure of subcutaneous tissues and skin to manage the dead space. Placement of a wound diffusion catheter is advisable for management of pain. A decision to place a negative suction drain will depend on the amount of dead space after closure, and surgeon’s preference.
Surgical Variations When tumors originate from the caudal aspect of the pelvis and cross the pubic midline, it may be necessary to perform osteotomies through the obturator foramen on the opposite side
Figure 5 The internal obturator muscle ( ) being resected from the osteotomized pubis ( ), thereby preserving soft tissue for closure of the pelvic canal. In some cases; however, this muscle is an important medial barrier for tumors that have penetrated into the pelvic canal through the obturator foramen. In this instance, care needs to be taken to ensure the tumor capsule is not breached and the internal obturator muscle is removed en bloc with the amputated limb.
Figure 6 With the limb free of muscular attachments, it will now be tethered by nerve branches from the lumbosacral plexus only. ( ) The osteotomized edge of the ileum is shown ( ). For nerve sheath tumors affecting the sciatic nerve or other nerves of the lumbosacral plexus, total external hemipelvectomy is usually required to allow the nerve to be traced to the foramen.
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optimal to leave some muscular tissue and its nerve supply intact to prevent muscle atrophy and excessive bony prominence, and minimize the likelihood of pressure sores. Castration should also be considered for entire dogs, as the scrotum will be susceptible to injury after hemipelvectomy.8 Postoperative Complications. Postoperative complications after hemipelvectomy are infrequent, but include hemorrhage and hematoma formation, wound dehiscence, incisional hernia, seroma, infection, obstipation, pressure sores, urethral and rectal trauma or dysfunction, tumor recurrence.8 When proper precautionary measures are taken damage to the rectum or urethra is rare. Postoperative recovery is similar to pelvic limb amputations and associated with few concerns. Duration of hospitalization is typically 3–10 days.8
Figure 7 After wound lavage, the sartorius muscle ( ) can be unwrapped from its moist swab and draped across the defect. It is then sutured to the abdominal muscle, adductor (with bone tunnels to the symphysis if necessary), and pelvic diaphragm to seal the exposed abdomen and pelvic canal.
to obtain a wide enough margin. Even greater care must be taken to protect the urethra and rectum in such cases. Primary skin closure is usually possible; however, preoperative anticipation of potential challenges in skin closure will allow the surgeon to tailor the initial skin incisions to specific needs (e.g. preserve more skin laterally if a biopsy tract has to be removed on the medial aspect and vice versa). When preserving skin over the lateral and distal aspect of the femur it is sometimes helpful to perform the dissection such that some muscle fibers (e.g. from the biceps femoris) remain attached to the skin and a portion of the blood supply and nerve supply to the muscle is preserved (assuming that this does not compromise tumor margins). If simple closure is not possible, skin advancement techniques (e.g. skinfold flap, deep circumflex ilial axial pattern flap, and caudal superficial epigastric axial pattern flap) can be used depending on location. In people, myocutaneous flaps have been described to aid closure.16 Expected Outcomes. Clinical function after hemipelvectomy should be similar to that after pelvic limb amputation and is influenced by patient size, fitness, and agility. If lameness has been present before surgery, dogs and cats will usually accommodate their amputee status quickly, with most being mobile soon after surgery. Larger dogs may benefit from some supportive walking for 3–4 days until they gain confidence and coordination. Disruption to urinary or fecal continence is not expected; however, if an epidural was used, some urinary retention may be observed. Obstipation for several days to a week has been reported, especially after large resections.8 Cosmetic results for hemipelvectomy are similar to simple amputation. When the ischiatic tuberosity is preserved it is
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DISCUSSION Hemipelvectomy is an aggressive surgery that requires anatomic knowledge of the pelvic region; however, experience suggests that, when performed with care and good anesthesia support, it is not associated with a high degree of intraoperative or postoperative morbidity.1,2,4,7,8 The modified technique reported here allows muscles and related soft tissues of the pelvis to be transected at their sites of origin or insertion, or to be removed in toto without disruption. The rationale for this more anatomically directed dissection is 2‐fold: it limits morbidity, hemorrhage, and postoperative pain that may be associated with mid‐body transection of very large muscles in the thigh region,17,18 and perhaps more importantly, it achieves the objectives of compartmental excision of musculoskeletal sarcoma, described by Enneking.9 Used in human musculoskeletal tumor surgery, the Enneking staging system has been used to assist with surgical planning and prognostication of mesenchymal tumors affecting the limb, but has not achieved prominence in veterinary oncology.9 This staging system takes into account the histologic, clinical, and radiographic features of the tumor.18,19 Crucially, Enneking defined a substage classification based on the anatomic location of the lesion that recognizes the expansile and locally invasive growth characteristics of mesenchymal tumors. Anatomic compartments such as fascial planes and bony structures provide inherent barriers to tumor spread. According to Enneking, lesions can be categorized as either “intracompartmental” or “extracompartmental.” Intracompartmental lesions are confined to the boundaries of well‐ defined anatomic structures (i.e. bone, joint or a fascially defined compartment of a functional muscle group). Extracompartmental lesions arise from within or extended into extrafascial spaces, or planes that have no natural anatomical barriers to extension. Coaxial imaging is used to determine whether the lesion is anatomically confined to well‐delineated surgical compartments, or has spread into ill‐defined fascial planes and spaces.9 Resection margins are defined by the extent of the surgical margin relative to the pseudocapsule and surrounding reactive zone, and can be classified as “marginal,”
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“wide,” or “radical.” According to Enneking, a radical margin involves removal of a whole “compartment” (e.g. a single muscle, a group of muscles surrounding a central tumor, or the entire limb) ensuring the tumor is contained entirely within robust anatomic barriers. Results in people support the concept that surgical treatment of sarcomas by radical excision along defined anatomic or compartmental boundaries statistically improves local disease control compared with wide resection.20–24 These improved outcomes may be because of more complete removal of the entire “reactive zone” that surrounds the pseudocapsule of the sarcoma. The extent of this reactive zone is variable, but on MRI can be observed to extend 7–10 cm beyond the pseudocapsule (Fig 1).11,25 Isolated tumor nodules located several centimeters from the tumor capsule,25,26 may explain why local recurrences can develop after wide marginal excision. In a retrospective study,8 incomplete resection margins were reported after hemipelvectomy in almost a third of cases (29 dogs, 4 cats) and local tumor recurrence developed in 13/83 (16%) dogs and 2/16 (12.5%) cats. The high rates of incomplete resection for many tumors in our report may reflect large tumor size at the time of diagnosis, tumor location and some anatomic limits to resection; however, it is important to note that all contributing surgeons developed their own surgical approach for resection, because a description of the procedure had not been reported. Most surgeons adopted a “wide margin excisional” approach, with dissection maintaining a minimum 2 cm margin about the tumor (and 1 fascial plan deep to the tumor) wherever possible. This often resulted in dissection that involved transection through muscles surrounding the tumor, similar to the technique described by Kramer et al.4 Whether this approach influenced the high rate of incomplete resections and local recurrence could not be reliably determined from the data, but tumor‐free margins were achieved in all animals that had the anatomic dissection described in this report compared to rates of 25–50% recorded with approaches made by others (Bray J.P., unpublished data, 2013). Although this difference may be because of case selection and other confounders, there is sufficient evidence from other human to support a move to a “compartmental” rather than “wide margin” excision of sarcoma whenever possible.20–24,27 Some human surgeons have argued that strict adherence to Enneking’s compartmental model can result in unnecessary loss of function, particularly when metastatic disease is often the main cause of patient death for musculoskeletal sarcoma.3,6,28 In people, amputation and hemipelvectomy can be associated with substantial morbidity and long‐term survival is often limited by high rates of metastatic disease. For these reasons, “limb sparing” strategies (termed internal hemipelvectomy) are becoming an optimal goal if tumor location permits, with adjuvant radiotherapy or chemotherapy used to improve local control once excisions become more marginal.6,12,29 To date, veterinary studies indicate that dogs and cats tolerate hemipelvectomy well1,2,4,7,8; however, as amputation is commonly required, patient selection is limited to those that can tolerate ambulation on 3 limbs. Metastatic disease was a
Hemipelvectomy: Modified Surgical Technique
common cause of death after hemipelvectomy, occurring in 39/83 (47%) dogs and 2/16 (12.5%) cats.8 Taken overall, only about 50% of dogs with malignant mesenchymal tumors (i.e. hemangiosarcoma, osteosarcoma, chondrosarcoma, soft tissue sarcoma) remained alive 1 year after surgery.8 Therefore, although we work with adaptable and accommodating species, it is important that veterinary oncologic surgeons maintain clear objectives when performing aggressive oncologic resections such as hemipelvectomy. Continued review of technique and outcomes will be important to ensure that sacrifice of function (e.g. by amputation) is justified by improved survival and tumor control. Careful planning using information from preoperative imaging may occasionally reveal options for internal hemipelvectomy that ensure effective local control is achieved without sacrifice of limb function. Summarily, hemipelvectomy is a viable surgical procedure for management of a wide variety of tumor types located within the pelvis or thigh musculature. Tumors at this location are often very large at the time of diagnosis and on first impression it can seem unlikely that effective management can be achieved. Case selection for surgery is similar to pelvic limb amputation, if limb sacrifice is required. A technique for hemipelvectomy guided by accurate anatomic dissection of the pelvic limb enabled compartmental resection of most tumors with clean surgical margins and is not typically associated with a high degree of intraoperative or postoperative morbidity.
ACKNOWLEDGMENTS The author acknowledges the contributions of members of the Veterinary Society of Surgical Oncology who participated in the hemipelvectomy clinical study that led to the development of this report.
DISCLOSURE The author reports no financial or other conflict of interest related to this report.
REFERENCES 1. Kasa G, Kasa F: Partial hemipelvectomy in the cat and dog. Praktische‐Tierarzt 1986;67:498–499 2. Straw RC, Withrow SJ, Powers BE: Partial or total hemipelvectomy in the management of sarcomas in nine dogs and two cats. Vet Surg 1992;21:183–188 3. Beck LA, Einertson MJ, Winemiller MH, et al: Functional outcomes and quality of life after tumor‐related hemipelvectomy. Phys Ther 2008;88:916–927 4. Kramer A, Walsh PJ, Seguin B: Hemipelvectomy in dogs and cats: technique overview, variations, and description. Vet Surg 2008;37:413–419
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5. Krijnen MR, Wuisman PI: Emergency hemipelvectomy as a result of uncontrolled infection after total hip arthroplasty: two case reports. J Arthroplasty 2004;19:803–808 6. Wedemeyer C, Kauther MD: Hemipelvectomy—only a salvage therapy? Orthop Rev (Pavia) 2011;3:e4 7. Alexander J, Carb A: Subtotal hemipelvectomy in the dog. J Vet Orthop 1979;1:9–14 8. Bray JP, Worley DR, Henderson RA, et al: Hemipelvectomy: outcome in 84 dogs and 16 cats. A Veterinary Society of Surgical Oncology Retrospective study. Vet Surg. DOI:10.1111/j.1532‐ 950X.2013.12080.x 9. Enneking WF, Spanier SS, Goodman MA: A system for the surgical staging of musculoskeletal sarcoma. Clin Orthop Relat Res 1980;204:106–120 10. Ehrhart N: Soft‐tissue sarcomas in dogs: a review. J Am Anim Hosp Assoc 2005;41:241–246 11. Liu QY, Li HG, Chen JY, et al: [Correlation of MRI features to histopathologic grade of soft tissue sarcoma]. Ai Zheng 2008;27:856–860 12. Ham SJ, Schraffordt Koops H, Veth RP, et al: External and internal hemipelvectomy for sarcomas of the pelvic girdle: consequences of limb‐salvage treatment. Eur J Surg Oncol 1997;23:540–546
incision. PhD Thesis, Iowa, University of Iowa, 2009. http://ir. uiowa.edu/etd/90 18. Sadighi PJ, Woodworth CS: Muscle‐splitting thoracotomy. Am Surg 1998;64:370–371 19. Jawad M, Scully S: In brief: classifications in brief: Enneking classification: benign and malignant tumors of the musculoskeletal system. Clin Orthop Relat Res 2010;468:2000–2002 20. Stotter A, Fallowfield M, Mott A, et al: Role of compartmental resection for soft tissue sarcoma of the limb and limb girdle. Br J Surg 1990;77:88–92 21. Enneking WF, Spanier SS, Malawer MM: The effect of the anatomic setting on the results of surgical procedures for soft parts sarcoma of the thigh. Cancer 1981;47:1005–1022 22. Enneking WF, Spanier SS, Goodman MA: A system for the surgical staging of musculoskeletal sarcoma. Clin Orthop Relat Res 2003; 4–18 23. Azzarelli A: Surgery in soft tissue sarcomas. Eur J Cancer 1993;29A:618–623 24. Karakousis CP, Kontzoglou K, Driscoll DL: Anterior compartment resection of the thigh in soft‐tissue sarcomas. Eur J Surg Oncol 1998;24:308–312
13. Pascoe PJ: Perioperative pain management. Vet Clin North Am Small Anim Pract 2000;30:917–932
25. White LM, Wunder JS, Bell RS, et al: Histologic assessment of peritumoral edema in soft tissue sarcoma. Int J Radiat Oncol Biol Phys 2005;61:1439–1445
14. Abelson AL, McCobb EC, Shaw S, et al: Use of wound soaker catheters for the administration of local anesthetic for post‐ operative analgesia: 56 cases. Vet Anaesth Analg 2009;36:597–602
26. Voros D, Theodorou D, Ventouri K, et al: Retroperitoneal tumors: do the satellite tumors mean something? J Surg Oncol 1998;68:30–33
15. McEntee MC, Steffey M, Dykes NL: Use of surgical hemoclips in radiation treatment planning. Vet Radiol Ultrasound 2008;49:395–399
27. Calabrese L, Giugliano G, Bruschini R, et al: Compartmental surgery in tongue tumours: description of a new surgical technique. Acta Otorhinolaryngol Ital 2009;29:259–264
16. Senchenkov A, Moran SL, Petty PM, et al: Soft‐tissue reconstruction of external hemipelvectomy defects. Plast Reconstr Surg 2009;124:144–155
28. Kawaguchi N, Ahmed AR, Matsumoto S, et al: The concept of curative margin in surgery for bone and soft tissue sarcoma. Clin Orthop Relat Res 2004; 165–172
17. Xu J: Contribution of deep muscle tissue to ongoing pain and spontaneous activity of nociceptive pathways after plantar
29. Hugate R Jr., Sim FH: Pelvic reconstruction techniques. Orthop Clin North Am 2006;37:85–97
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Corresponding Author Jonathan Bray, MVSc CertSAS, MACVSc, MSc (Clin Onc), Diplomate ECVS, Veterinary Teaching Hospital, Massey University, Private Bag 11‐222, Palmerston North, New Zealand. E‐mail: [email protected] Submitted November 2012 Accepted September 2013 DOI:10.1111/j.1532-950X.2013.12085.x
Objective: To report a technique for hemipelvectomy surgery in the dog and cat. Study Design: Descriptive report. Animals: Dogs and cats. Methods: To describe patient selection and an anatomically based surgical technique for hemipelvectomy. Results: Surgery of the pelvis requires detailed anatomic knowledge of the pelvic region. Hemipelvectomy is a major surgical procedure with potential for substantial hemorrhage because of transection through large muscle groups and proximity to major vessels. The anatomic dissection may enable better adherence to principles of compartmental resection of tumors and reduced patient morbidity. Conclusions: When performed with appropriate care, preoperative planning, and good anesthesia support, hemipelvectomy can be performed safely and is effective for radical excision of various tumor types arising from or near the pelvis.
Hemipelvectomy enables effective management of tumors or functional abnormalities (e.g. fracture malunion) involving the pelvis or associated soft tissues.1–6 Although an entire hemi‐ pelvis can be resected, partial pelvectomy is usually adequate for removing tumors involving the pelvis, coxofemoral joint, or proximal aspect of the thigh. Other than occasional case reports and a small case series of 9 dogs and cats,1,2,7 details on a surgical technique for hemipelvectomy in the dog and cat were not published until 2008.4 The authors described hemipelvectomy as “an involved and aggressive surgery,” with a dissection that must be tailored to each specific case. Recently, members of the Veterinary Society of Surgical Oncology completed a multi‐institutional retrospective study that described clinical details and outcome of a cohort of 100 dogs and cats that had hemipelvectomy surgery for neoplastic disorders.8 Although survival times for many malignant mesenchymal tumors were good, local tumor recurrence rates of 19% were observed, with recurrence being associated with an increased rate of death and reduced overall survival. High rates of local recurrence are also a feature of human hemipelvectomy surgery because of local extension of tumor into adjacent pelvic structures, microscopic foci of tumor in otherwise normal tissue and widespread invasion into major pelvic veins.6 These findings support the need for careful surgical planning to ensure tumor resection can be accomplished without encroaching into the peritumoral environment. In this paper, a modification of a technique for hemipelvectomy reported by Kramer et al is described and perioperative experience gained from a multi‐institutional study is reported. More precise anatomic dissection of the pelvic musculature should enable better compartmental excision of neoplasms.9
SURGICAL PLANNING Tumor Staging After mass identification by palpation or diagnostic imaging, complete oncologic examination is critical. Thorough clinical staging with thoracic imaging and abdominal ultrasonography,10 or a whole‐body CT, should be performed as most tumors affecting the pelvis have metastatic potential.8 Cytologic or histopathologic diagnosis of the tumor should be obtained by fine needle aspiration or tru‐cut biopsy. The surgeon should carefully consider the biopsy technique in relation to the subsequent surgery to ensure the biopsy tract can be safely removed. Imaging Assessment Anatomic compartments such as fascial planes and bony structures provide inherent barriers to tumor spread.9 With careful planning, hemipelvectomy can facilitate pelvic limb amputation with preservation of an intact anatomic compartment around the tumor. Much of the information necessary for surgical planning can be obtained by coaxial imaging (CT, MRI) and is an essential element of presurgical management (Fig 1) Whereas MRI provides superior information compared with CT for soft tissue structures and the extent of reactive zone surrounding the tumor,11 adequate information on tissue compartments and barriers can still be obtained to enable surgical planning with CT alone. It is important for the patient to be positioned in the scanner so that the pelvic limb maintains a neutral configuration typical of a standing animal. If the limb is placed in a “frog‐
Veterinary Surgery 43 (2014) 19–26 © Copyright 2013 by The American College of Veterinary Surgeons
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Figure 1 MRI images (axial T2W and sagittal STIR views) of a canine fibrosarcoma within the soft tissues of the caudal thigh. Note the large tumor size, and the extensive reactive zone of inflammation and edema that surrounds the tumor. A caudal external hemipelvectomy would be recommended for compartmental excision of the tumor to ensure the reactive zone is not breached and remains completely contained by the resected compartment of tissue.
leg,” it can become difficult to map out the anatomic boundaries of the limb in relative to the tumor. A neutral limb position ensures the flexor and extensor muscle compartments can be fully evaluated relative to the tumor, and allows tumor resection to be confidently planned. Anatomic Resection Each individual has a unique presentation in terms of tumor type, location, and extent so the precise surgical considerations will differ between each.4 In human surgery, the term “external hemipelvectomy” is used to describe a procedure that also includes amputation of the pelvic limb; “internal hemipelvectomy” is used when the limb is preserved.3,6,12 Using this nomenclature, there are 6 major categories for hemipelvectomy in dogs (Fig 2). Total External Hemipelvectomy. Removal of the ipsilateral pelvic limb and hemi‐pelvis to the level of the pubic symphysis; the ilial wing is elevated at the sacroiliac junction. Partial sacrectomy (up to one‐third of the sacral body) may also be performed if necessary (personal communication: Dr. Nick Bacon, 2010). This approach may be considered for tumors affecting the ilium, ischium, or pubis where resection of the entire skeletal compartment is necessary. Caudal External Hemipelvectomy. Removal of the ipsilateral pelvic limb, acetabulum, and ischium wing, extending from just caudal to the sacroiliac joint and medially to the level
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of the pubic symphysis. This approach preserves a small section of ilial wing and the site of origin for the sartorius muscle, which is ideal for the closure of the abdominal wall. This approach may be considered for soft tissue tumors located caudal to the femur (e.g. within the flexor muscles) or for peripheral nerve sheath tumors. From the VSSO retrospective study, these locations comprise most clinical presentations.8 Good access to the entire lumbosacral nerve plexus and intervertebral foramen is possible with this approach. Cranial External Hemipelvectomy. Removal of the ipsilateral pelvic limb, acetabulum, and ilial wing, extending to the level of the pubic symphysis. This approach is ideal for soft tissue tumors located cranial to the femur (i.e. within the extensor muscles). This approach preserves the site of origin of the semimembranosus/semitendinosus muscles, which may be used for closure of the abdominal defect. Cranial Internal Hemipelvectomy (Iliectomy). Reserved for tumors confined to the surface of the ilial wing or sartorius muscle. This approach can potentially be performed without requiring amputation of the pelvic limb, depending on the local extent of the tumor. Caudal Internal Hemipelvectomy (Ischiectomy). Reserved for tumors confined to the ischium or semimembranosus/semitendinosus muscles. This approach can potentially be performed without requiring amputation of the pelvic limb, depending on the local extent of the tumor.
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Figure 2 Hemipelvectomy techniques. External pelvectomy entails amputation of the ipsilateral pelvic limb, whereas internal hemipelvectomy enables functional limb sparing. (A) Total external hemipelvectomy; (B) caudal external hemipelvectomy; (C) cranial external hemipelvectomy; (D) cranial internal hemipelvectomy (iliectomy); (E) caudal internal hemipelvectomy (ischiectomy). (G) Middle internal or external hemipelvectomy (acetabulectomy). Although option B is perhaps the most common technique, consideration of tumor location and local invasiveness are important in surgical planning.
Middle Internal/External Hemipelvectomy (Acetabulectomy). Removal of the femoral head and acetabulum, often involving amputation of the ipsilateral limb. This approach is best reserved for tumors confined to the coxofemoral joint without extension into the surrounding tissues. In the cat, this approach has been described for management of fracture malunion causing fecal obstipation.1 Acetabulectomy could be performed without requiring amputation of the pelvic limb provided the tumor was confined completely to the coxofemoral joint, though some gait effect may be observed similar to femoral head ostectomy. Preoperative Considerations Hemipelvectomy is a major surgery with the potential for significant hemorrhage because of transection through large muscle groups and proximity to major vessels. Severe hemorrhage requiring transfusion or aggressive volume support may arise despite anatomic knowledge and sound surgical technique. Preparation of the patient for a potential blood transfusion should be made before surgery by perform-
ing a cross‐match or blood typing as appropriate for blood bank facilities available in the hospital. Anesthesia management should be performed as for a pelvic limb amputation with consideration for multi‐modal preemptive analgesia.13 Systemic opioids, in combination with either a morphine and/or lidocaine epidural, is effective in most instances. Non‐steroidal anti‐inflammatory drugs may be withheld until after the patient has recovered from surgery in case of hypotension during a prolonged surgery. Performing local nerve blocks with a combination of lidocaine and bupivacaine should be considered before transection of major nerves during surgery.10 In addition wound diffusion catheters may enable good postoperative pain relief.14 A negative suction drain can be used for managing dead space. A wide area of the limb and pelvic limb is prepared, extending medially to the level of the contralateral stifle, cranially to mid abdomen and dorsally across to the opposite coxofemoral joint. The anal canal should be evacuated and a purse string suture placed to protect against bowel evacuation during surgery. An indwelling urinary catheter should be placed to assist with recognition of the urethra during surgery.
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Hemipelvectomy is typically performed in lateral recumbency; however, oblique positioning may occasionally be helpful (e.g. for sciatic nerve root tumors requiring concurrent hemilaminectomy). When planning the incisions, consideration needs to be given to removing biopsy tracts, and to ensuring there is sufficient skin available for closure. Skin from the medial or lateral thigh, extending to the level of the stifle, ideally needs to be preserved to ensure a tension‐free skin closure can be accomplished. The location of the tumor, and/or the previous biopsy tract will usually determine which portion of skin can be preserved.
femoris muscle, and there are many musculocutaneous vascular branches penetrating into the hypodermis so this dissection is tedious. With the skin elevated, dissection continues caudally around the ischium, between the semitendinosus and ischiocavernosus muscles, staying medial to the sacrotuberous ligament. The muscles of the pelvic diaphragm (levator ani and lateral coccygeus) should remain in situ on the medial aspect of the dissection. The superficial gluteal muscle is transected along its length close to its dorsal origin. The lumbar fascia may also be incised cranially to expose the middle gluteal muscle (Fig 3). Limb Amputation
SURGICAL TECHNIQUE The following description outlines the dissection necessary for a total external hemipelvectomy or caudal external hemipelvectomy. Some extrapolation of the fundamental principles may be required if other variations of hemipelvectomy are required. The goal of surgery should be to completely excise the neoplasm with at least 1 intact fascial plane about the entire circumference of the tumor. Medial Dissection Dissection begins medially, with a curvilinear incision extending along the medial thigh from the inguinal fold to the ischium. The sartorius muscle (both cranial and caudal bellies) is transected at the level of the stifle and elevated en bloc from the limb, preserving its attachment on the ilial wing. The branch of the descending genicular artery is ligated as it passes ventral to the muscle distally. The superficial circumflex artery and vein may need to ligated more proximally to allow elevation of the muscle from the femoral artery. The muscle is kept moist by application of saline (0.9% NaCl) solution soaked swabs. The skin is elevated to expose the midline of the pubis using self‐retaining retractors to maintain exposure. The medial thigh muscles (adductor/gracilis/pectineus) are incised on the midline down to the pubic symphysis; a faint fascial aponeurosis defines the midline at this site. The abdominal muscles are cut as they insert on the pubis and retracted cranially, elevating the muscle from the ilial wing until the iliopsoas muscle is visible and the ventral surface of the ilial wing is palpable. The external iliac artery and vein are isolated and double ligated, before division. The iliopsoas muscles are isolated and transected with a scalpel blade. Typically, this can be performed as close to the tendinous insertion on the femoral neck as possible. The ventral surface of the ilial wing is exposed with periosteal elevators.
Dissection focus now shifts cranially to the previously exposed ventral surface of the ilial wing. If a total hemipelvectomy is being performed, the sacrum can be exposed and the ilium elevated by inserting an osteotome at the sacroiliac joint and separating with a mallet. If necessary, a small ventral edge of ilium needs to be osteotomized to preserve the origin of the elevated sartorius muscle. If a mid‐to‐caudal pelvectomy is being performed, the medial gluteal muscle can be partially elevated from the ilium to allow the ilium to be cut with an oscillating saw immediately caudal to the sacroiliac joint. The pubic symphysis is cut with an oscillating saw or osteotome (Fig 4). As the limb is gently elevated from the body, remaining medial muscle attachments will be exposed and can be gently incised. The internal obturator muscle may be an important medial barrier for some tumors that have penetrated into the pelvic canal via the obturator foramen. In this instance, care needs to be taken to ensure the tumor capsule is not breached and the internal obturator muscle is removed en bloc with the amputated limb (Fig 5). With the limb free of muscular attachments, it will now be tethered by nerve branches from the lumbosacral plexus only
Lateral Dissection A curvilinear skin incision is made on the lateral surface of the thigh, joining the previous medial incisions. The skin is elevated proximally to expose the lumbar fascia above the coxofemoral joint. The skin is in close contact with the biceps
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Figure 3 Dorsolateral dissection. The superficial gluteal and tensor fascia lata muscles ( ) are transected along its length close to its dorsal origin. The lumbar fascia may also be incised cranially to expose the middle gluteal muscle. The ischiocavernosus muscle is transected from its origin on the ischium ( ) (Dorsal view, with cranial to left of picture).
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should be injected with a long‐acting local anesthetic (e.g. a mixture of lidocaine and bupivacaine) proximal to the site of transection.13 For peripheral nerve sheath tumors, care is needed to map out all of the lumbosacral plexus and trace each nerve branch to the level of the intervertebral foramen at L6, L7, and S1 (Fig 6) Each nerve is then cut sharply as it enters the foramen. The remaining section of iliopsoas muscle may need to be elevated to expose the most cranial foramen. Closure
Figure 4 Ventral dissection. The sartorius muscle (both cranial and caudal bellies) has been elevated en bloc from its insertion at the level of the stifle and wrapped in saline solution soaked swabs to keep moist during the remaining dissection ( ). The medial thigh muscles (adductor/ gracilis/pectineus) have been incised on the midline to the pubic symphysis, which has been cut with an oscillating saw or osteotome ( ). During osteotomy, it is useful to place a periosteal elevator in the pelvic canal to protect the urethra and rectum.
so the assistant needs to support the weight of the limb. For most tumors, the nerves can be transected close to the limb; pudendal nerve branches (more caudally located) should be preserved where possible. Before transection, the nerve sheath
The wound is lavaged and any remaining bleeding vessels managed. If postoperative radiation is being considered, metal hemoclips should be placed about the periphery of the dissection field before closure.15 The sartorius muscle can be unwrapped from its moist swab and draped across the defect (Fig 7). It is then secured to the abdominal muscle, adductor (with bone tunnels to the symphysis if necessary) and pelvic diaphragm to close the exposed abdomen and pelvic canal. Muscular defects in the caudolateral abdominal wall and pelvic diaphragm usually exist after resection of the entire hemi‐ pelvis. In rare cases, a prosthetic mesh may be needed. Care is taken with the remaining closure of subcutaneous tissues and skin to manage the dead space. Placement of a wound diffusion catheter is advisable for management of pain. A decision to place a negative suction drain will depend on the amount of dead space after closure, and surgeon’s preference.
Surgical Variations When tumors originate from the caudal aspect of the pelvis and cross the pubic midline, it may be necessary to perform osteotomies through the obturator foramen on the opposite side
Figure 5 The internal obturator muscle ( ) being resected from the osteotomized pubis ( ), thereby preserving soft tissue for closure of the pelvic canal. In some cases; however, this muscle is an important medial barrier for tumors that have penetrated into the pelvic canal through the obturator foramen. In this instance, care needs to be taken to ensure the tumor capsule is not breached and the internal obturator muscle is removed en bloc with the amputated limb.
Figure 6 With the limb free of muscular attachments, it will now be tethered by nerve branches from the lumbosacral plexus only. ( ) The osteotomized edge of the ileum is shown ( ). For nerve sheath tumors affecting the sciatic nerve or other nerves of the lumbosacral plexus, total external hemipelvectomy is usually required to allow the nerve to be traced to the foramen.
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optimal to leave some muscular tissue and its nerve supply intact to prevent muscle atrophy and excessive bony prominence, and minimize the likelihood of pressure sores. Castration should also be considered for entire dogs, as the scrotum will be susceptible to injury after hemipelvectomy.8 Postoperative Complications. Postoperative complications after hemipelvectomy are infrequent, but include hemorrhage and hematoma formation, wound dehiscence, incisional hernia, seroma, infection, obstipation, pressure sores, urethral and rectal trauma or dysfunction, tumor recurrence.8 When proper precautionary measures are taken damage to the rectum or urethra is rare. Postoperative recovery is similar to pelvic limb amputations and associated with few concerns. Duration of hospitalization is typically 3–10 days.8
Figure 7 After wound lavage, the sartorius muscle ( ) can be unwrapped from its moist swab and draped across the defect. It is then sutured to the abdominal muscle, adductor (with bone tunnels to the symphysis if necessary), and pelvic diaphragm to seal the exposed abdomen and pelvic canal.
to obtain a wide enough margin. Even greater care must be taken to protect the urethra and rectum in such cases. Primary skin closure is usually possible; however, preoperative anticipation of potential challenges in skin closure will allow the surgeon to tailor the initial skin incisions to specific needs (e.g. preserve more skin laterally if a biopsy tract has to be removed on the medial aspect and vice versa). When preserving skin over the lateral and distal aspect of the femur it is sometimes helpful to perform the dissection such that some muscle fibers (e.g. from the biceps femoris) remain attached to the skin and a portion of the blood supply and nerve supply to the muscle is preserved (assuming that this does not compromise tumor margins). If simple closure is not possible, skin advancement techniques (e.g. skinfold flap, deep circumflex ilial axial pattern flap, and caudal superficial epigastric axial pattern flap) can be used depending on location. In people, myocutaneous flaps have been described to aid closure.16 Expected Outcomes. Clinical function after hemipelvectomy should be similar to that after pelvic limb amputation and is influenced by patient size, fitness, and agility. If lameness has been present before surgery, dogs and cats will usually accommodate their amputee status quickly, with most being mobile soon after surgery. Larger dogs may benefit from some supportive walking for 3–4 days until they gain confidence and coordination. Disruption to urinary or fecal continence is not expected; however, if an epidural was used, some urinary retention may be observed. Obstipation for several days to a week has been reported, especially after large resections.8 Cosmetic results for hemipelvectomy are similar to simple amputation. When the ischiatic tuberosity is preserved it is
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DISCUSSION Hemipelvectomy is an aggressive surgery that requires anatomic knowledge of the pelvic region; however, experience suggests that, when performed with care and good anesthesia support, it is not associated with a high degree of intraoperative or postoperative morbidity.1,2,4,7,8 The modified technique reported here allows muscles and related soft tissues of the pelvis to be transected at their sites of origin or insertion, or to be removed in toto without disruption. The rationale for this more anatomically directed dissection is 2‐fold: it limits morbidity, hemorrhage, and postoperative pain that may be associated with mid‐body transection of very large muscles in the thigh region,17,18 and perhaps more importantly, it achieves the objectives of compartmental excision of musculoskeletal sarcoma, described by Enneking.9 Used in human musculoskeletal tumor surgery, the Enneking staging system has been used to assist with surgical planning and prognostication of mesenchymal tumors affecting the limb, but has not achieved prominence in veterinary oncology.9 This staging system takes into account the histologic, clinical, and radiographic features of the tumor.18,19 Crucially, Enneking defined a substage classification based on the anatomic location of the lesion that recognizes the expansile and locally invasive growth characteristics of mesenchymal tumors. Anatomic compartments such as fascial planes and bony structures provide inherent barriers to tumor spread. According to Enneking, lesions can be categorized as either “intracompartmental” or “extracompartmental.” Intracompartmental lesions are confined to the boundaries of well‐ defined anatomic structures (i.e. bone, joint or a fascially defined compartment of a functional muscle group). Extracompartmental lesions arise from within or extended into extrafascial spaces, or planes that have no natural anatomical barriers to extension. Coaxial imaging is used to determine whether the lesion is anatomically confined to well‐delineated surgical compartments, or has spread into ill‐defined fascial planes and spaces.9 Resection margins are defined by the extent of the surgical margin relative to the pseudocapsule and surrounding reactive zone, and can be classified as “marginal,”
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“wide,” or “radical.” According to Enneking, a radical margin involves removal of a whole “compartment” (e.g. a single muscle, a group of muscles surrounding a central tumor, or the entire limb) ensuring the tumor is contained entirely within robust anatomic barriers. Results in people support the concept that surgical treatment of sarcomas by radical excision along defined anatomic or compartmental boundaries statistically improves local disease control compared with wide resection.20–24 These improved outcomes may be because of more complete removal of the entire “reactive zone” that surrounds the pseudocapsule of the sarcoma. The extent of this reactive zone is variable, but on MRI can be observed to extend 7–10 cm beyond the pseudocapsule (Fig 1).11,25 Isolated tumor nodules located several centimeters from the tumor capsule,25,26 may explain why local recurrences can develop after wide marginal excision. In a retrospective study,8 incomplete resection margins were reported after hemipelvectomy in almost a third of cases (29 dogs, 4 cats) and local tumor recurrence developed in 13/83 (16%) dogs and 2/16 (12.5%) cats. The high rates of incomplete resection for many tumors in our report may reflect large tumor size at the time of diagnosis, tumor location and some anatomic limits to resection; however, it is important to note that all contributing surgeons developed their own surgical approach for resection, because a description of the procedure had not been reported. Most surgeons adopted a “wide margin excisional” approach, with dissection maintaining a minimum 2 cm margin about the tumor (and 1 fascial plan deep to the tumor) wherever possible. This often resulted in dissection that involved transection through muscles surrounding the tumor, similar to the technique described by Kramer et al.4 Whether this approach influenced the high rate of incomplete resections and local recurrence could not be reliably determined from the data, but tumor‐free margins were achieved in all animals that had the anatomic dissection described in this report compared to rates of 25–50% recorded with approaches made by others (Bray J.P., unpublished data, 2013). Although this difference may be because of case selection and other confounders, there is sufficient evidence from other human to support a move to a “compartmental” rather than “wide margin” excision of sarcoma whenever possible.20–24,27 Some human surgeons have argued that strict adherence to Enneking’s compartmental model can result in unnecessary loss of function, particularly when metastatic disease is often the main cause of patient death for musculoskeletal sarcoma.3,6,28 In people, amputation and hemipelvectomy can be associated with substantial morbidity and long‐term survival is often limited by high rates of metastatic disease. For these reasons, “limb sparing” strategies (termed internal hemipelvectomy) are becoming an optimal goal if tumor location permits, with adjuvant radiotherapy or chemotherapy used to improve local control once excisions become more marginal.6,12,29 To date, veterinary studies indicate that dogs and cats tolerate hemipelvectomy well1,2,4,7,8; however, as amputation is commonly required, patient selection is limited to those that can tolerate ambulation on 3 limbs. Metastatic disease was a
Hemipelvectomy: Modified Surgical Technique
common cause of death after hemipelvectomy, occurring in 39/83 (47%) dogs and 2/16 (12.5%) cats.8 Taken overall, only about 50% of dogs with malignant mesenchymal tumors (i.e. hemangiosarcoma, osteosarcoma, chondrosarcoma, soft tissue sarcoma) remained alive 1 year after surgery.8 Therefore, although we work with adaptable and accommodating species, it is important that veterinary oncologic surgeons maintain clear objectives when performing aggressive oncologic resections such as hemipelvectomy. Continued review of technique and outcomes will be important to ensure that sacrifice of function (e.g. by amputation) is justified by improved survival and tumor control. Careful planning using information from preoperative imaging may occasionally reveal options for internal hemipelvectomy that ensure effective local control is achieved without sacrifice of limb function. Summarily, hemipelvectomy is a viable surgical procedure for management of a wide variety of tumor types located within the pelvis or thigh musculature. Tumors at this location are often very large at the time of diagnosis and on first impression it can seem unlikely that effective management can be achieved. Case selection for surgery is similar to pelvic limb amputation, if limb sacrifice is required. A technique for hemipelvectomy guided by accurate anatomic dissection of the pelvic limb enabled compartmental resection of most tumors with clean surgical margins and is not typically associated with a high degree of intraoperative or postoperative morbidity.
ACKNOWLEDGMENTS The author acknowledges the contributions of members of the Veterinary Society of Surgical Oncology who participated in the hemipelvectomy clinical study that led to the development of this report.
DISCLOSURE The author reports no financial or other conflict of interest related to this report.
REFERENCES 1. Kasa G, Kasa F: Partial hemipelvectomy in the cat and dog. Praktische‐Tierarzt 1986;67:498–499 2. Straw RC, Withrow SJ, Powers BE: Partial or total hemipelvectomy in the management of sarcomas in nine dogs and two cats. Vet Surg 1992;21:183–188 3. Beck LA, Einertson MJ, Winemiller MH, et al: Functional outcomes and quality of life after tumor‐related hemipelvectomy. Phys Ther 2008;88:916–927 4. Kramer A, Walsh PJ, Seguin B: Hemipelvectomy in dogs and cats: technique overview, variations, and description. Vet Surg 2008;37:413–419
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5. Krijnen MR, Wuisman PI: Emergency hemipelvectomy as a result of uncontrolled infection after total hip arthroplasty: two case reports. J Arthroplasty 2004;19:803–808 6. Wedemeyer C, Kauther MD: Hemipelvectomy—only a salvage therapy? Orthop Rev (Pavia) 2011;3:e4 7. Alexander J, Carb A: Subtotal hemipelvectomy in the dog. J Vet Orthop 1979;1:9–14 8. Bray JP, Worley DR, Henderson RA, et al: Hemipelvectomy: outcome in 84 dogs and 16 cats. A Veterinary Society of Surgical Oncology Retrospective study. Vet Surg. DOI:10.1111/j.1532‐ 950X.2013.12080.x 9. Enneking WF, Spanier SS, Goodman MA: A system for the surgical staging of musculoskeletal sarcoma. Clin Orthop Relat Res 1980;204:106–120 10. Ehrhart N: Soft‐tissue sarcomas in dogs: a review. J Am Anim Hosp Assoc 2005;41:241–246 11. Liu QY, Li HG, Chen JY, et al: [Correlation of MRI features to histopathologic grade of soft tissue sarcoma]. Ai Zheng 2008;27:856–860 12. Ham SJ, Schraffordt Koops H, Veth RP, et al: External and internal hemipelvectomy for sarcomas of the pelvic girdle: consequences of limb‐salvage treatment. Eur J Surg Oncol 1997;23:540–546
incision. PhD Thesis, Iowa, University of Iowa, 2009. http://ir. uiowa.edu/etd/90 18. Sadighi PJ, Woodworth CS: Muscle‐splitting thoracotomy. Am Surg 1998;64:370–371 19. Jawad M, Scully S: In brief: classifications in brief: Enneking classification: benign and malignant tumors of the musculoskeletal system. Clin Orthop Relat Res 2010;468:2000–2002 20. Stotter A, Fallowfield M, Mott A, et al: Role of compartmental resection for soft tissue sarcoma of the limb and limb girdle. Br J Surg 1990;77:88–92 21. Enneking WF, Spanier SS, Malawer MM: The effect of the anatomic setting on the results of surgical procedures for soft parts sarcoma of the thigh. Cancer 1981;47:1005–1022 22. Enneking WF, Spanier SS, Goodman MA: A system for the surgical staging of musculoskeletal sarcoma. Clin Orthop Relat Res 2003; 4–18 23. Azzarelli A: Surgery in soft tissue sarcomas. Eur J Cancer 1993;29A:618–623 24. Karakousis CP, Kontzoglou K, Driscoll DL: Anterior compartment resection of the thigh in soft‐tissue sarcomas. Eur J Surg Oncol 1998;24:308–312
13. Pascoe PJ: Perioperative pain management. Vet Clin North Am Small Anim Pract 2000;30:917–932
25. White LM, Wunder JS, Bell RS, et al: Histologic assessment of peritumoral edema in soft tissue sarcoma. Int J Radiat Oncol Biol Phys 2005;61:1439–1445
14. Abelson AL, McCobb EC, Shaw S, et al: Use of wound soaker catheters for the administration of local anesthetic for post‐ operative analgesia: 56 cases. Vet Anaesth Analg 2009;36:597–602
26. Voros D, Theodorou D, Ventouri K, et al: Retroperitoneal tumors: do the satellite tumors mean something? J Surg Oncol 1998;68:30–33
15. McEntee MC, Steffey M, Dykes NL: Use of surgical hemoclips in radiation treatment planning. Vet Radiol Ultrasound 2008;49:395–399
27. Calabrese L, Giugliano G, Bruschini R, et al: Compartmental surgery in tongue tumours: description of a new surgical technique. Acta Otorhinolaryngol Ital 2009;29:259–264
16. Senchenkov A, Moran SL, Petty PM, et al: Soft‐tissue reconstruction of external hemipelvectomy defects. Plast Reconstr Surg 2009;124:144–155
28. Kawaguchi N, Ahmed AR, Matsumoto S, et al: The concept of curative margin in surgery for bone and soft tissue sarcoma. Clin Orthop Relat Res 2004; 165–172
17. Xu J: Contribution of deep muscle tissue to ongoing pain and spontaneous activity of nociceptive pathways after plantar
29. Hugate R Jr., Sim FH: Pelvic reconstruction techniques. Orthop Clin North Am 2006;37:85–97
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