2.15 Pathological pelvic fractures and acetabular reconstruction in metastatic disease
1 Introduction
Metastatic lesions in the bony pelvis profoundly reduce a patient’s quality of life and can intimidate oncologists and orthopedic surgeons, who may lack familiarity with advanced treatment options for this condition. This chapter reviews treatment strategies for patients with these metastases.
Metastases can develop anywhere within the pelvic ring, causing pain and fracture from structural insufficiency of the bone. Metastatic lesions may also be associated with a large soft-tissue component that can cause symptoms independent of the bone (eg, nerve impingement, venous outflow obstruction, traction, or impingement on normal soft-tissue structures) and require therapeutic intervention. Unlike pelvic pathology from trauma, pathological pelvic fractures do not exhibit the acute soft-tissue disruption associated with high-energy trauma. Most pathological fractures of the pelvis remain undisplaced, and most can be treated nonoperatively. Pain management, protected weight bearing, and appropriate adjuvant therapy (ie, radiation therapy and/or chemotherapy) usually suffice for pathological fractures of the superior or inferior pubic rami, the iliac wing, the sacral ala, as well as avulsion fractures involving the anterior superior or anterior inferior iliac spines or the ischial tuberosity. Nonsurgical measures usually succeed, with some notable exceptions. For example, symptoms associated with pathological fractures of the ischium can persist as a result of unresolved compressive forces (sitting) or tension forces (hamstring pull). In these instances, curettage, cementation, and fixation may be necessary to provide relief ( Fig 2.15-1 ). Local care must be applied in concert with systemic therapy. The surgeon should ensure that proper bone protective therapies are used in accordance with the recommendations of the National Comprehensive Cancer Network guidelines for bone health in patients with metastatic bone disease [1]. By integrating supportive care, biological suppression of the cancer, and mechanical protection of the deficient bony structure, patients usually remain comfortable and functional.
Several factors, including the responsiveness of the tumor to radiation and chemotherapy, the healing potential of the fracture, and the life expectancy of the patient, determine whether surgery will be performed. Each type of primary tumor has unique features that determine the frequency of pelvic metastases, the amount of matrix produced by the local tumor and host, and the vascularity of the metastasis. These features also influence decision making. For example, a sclerotic prostate cancer metastasis may be treated expectantly, a solitary lytic renal metastasis can be treated with embolization and resection, and a breast cancer lesion that has not responded to hormone and radiation therapy would be treated with hip arthroplasty and the so-called Harrington reconstruction. Although a comprehensive review of these oncological distinguishing features is beyond the scope of the chapter, these factors must be considered when surgery is contemplated for metastatic cancer of the pelvis.
The acetabulum presents a more complex management problem. The extent of bone destruction and associated bone insufficiency govern the treatment of the acetabular fracture. Traumatic or fragility fractures of the acetabulum differ from metastatic pathological fractures because of the magnitude of bone deficiency and the healing potential of the fractures. Pathological fractures either do not heal or heal in a slow, limited fashion because of tumor progression and/or diminished bone formation after radiation or chemotherapy [2].
2 Metastatic disease of the acetabulum
2.1 Background
Metastatic lesions involving the acetabulum frequently occur in patients with cancer. These lesions can progress, leading to pathological fracture involving the hip joint or mechanical insufficiency of the acetabulum, causing significant pain and functional compromise. Initial management should incorporate the following modalities, as appropriate: pain management with narcotic analgesics, protected weight bearing, radiation, antineoplastic agents, and bisphosphonates. However, if symptoms persist despite adequate non-operative management, surgical intervention may be required to address the problem. Surgery for a metastatic acetabular lesion is a significant operative procedure for patients who often have multiple-organ system compromise because of the underlying disease, as well as a reduced life expectancy. Thus, surgery involves significant risks to the patient; however; when performed in the appropriate situation, it can lead to substantial and sustained functional improvement and pain relief, with 75% of patients achieving satisfactory pain relief and 60–75% maintaining the ability to walk and to function in the community 6 months postoperatively [3–6].
General indications for surgical management of patients with metastatic lesions involving the acetabulum must consider factors such as patient disability, response to nonsurgical therapy, coincident disease, and projected patient longevity [7]. Specifically, surgery is warranted when patients experience continued acute symptoms despite appropriate nonoperative therapy, persistent debilitating pain and poor function 1–3 months after radiation therapy, and pathological fracture of the ipsilateral femur, impending pathological fracture of the ipsilateral femur requiring surgery, or coincidental acetabular fracture. To justify surgical intervention, the patient’s life expectancy should exceed 1 month and preferably 3 months [3, 8].
The factors found to reflect prognosis in these patients include preoperative performance status, the presence of visceral metastasis, and tumor type. The Eastern Cooperative Oncology Group (ECOG) Performance Status scale is an effective tool for functional evaluation of patients and has been found to reflect prognosis ( Table 2.15-1 ) [9–13]. Marco et al [3] reported that the median survival of patients with an ECOG score of 0 or 1 was 15 months compared with 7 months in those with an ECOG score higher than 1. Patients without visceral metastasis had a median survival of 12 months compared with 3 months in those with visceral metastasis (P < .004). The type of primary tumor was also found to reflect prognosis and survival. Patients with breast cancer bony metastasis survived longer (median, 19 months) than patients with all other tumor types (median, 6 months) [3].
2.2 Evaluation and workup
Preoperative evaluation involves a thorough history and physical examination. An overall medical evaluation is required with assessment of the patient’s ability to tolerate surgery. Laboratory evaluation should always include a serum calcium level because 5–10% of patients with metastatic bone disease can have hypercalcemia of malignancy. This condition most commonly occurs in patients with the primary diagnoses of myeloma, squamous cell carcinoma of the lung, and breast cancer. Hypercalcemia develops in more than 30% of patients with breast cancer metastasis to bone at some point in their course [14]. Patients who have been bedridden or immobile are at a heightened risk for hypercalcemia. Widespread use of bisphosphonates has diminished the frequency of this complication. Debilitated patients with cancer are in a hypercoagulable state and are at high risk for deep vein thrombosis. Preoperative screening with a duplex Doppler ultrasound and prophylactic or therapeutic use of a vena cava filter should be considered in the appropriate patient. Radiographic evaluation is necessary to define the anatomy of the lesion and allow for proper surgical planning, as well as to screen the patient for other sites of skeletal involvement that may impact the clinical situation. For example, a patient with an ipsilateral femoral shaft lesion may require concomitant stabilization with a long-stem femoral component to avoid a pathological periprosthetic fracture below a standard-length femoral stem.
Radiographic evaluation of the acetabular lesion should include plain x-rays and a 3-D imaging study. An AP pelvis and AP and lateral views of the full ipsilateral femur are needed to evaluate for additional lesions. Image intensification, specifically Judet views, is helpful in further defining the acetabular lesion and the extent of anterior or posterior column involvement. A full-body bone scan screens the rest of the skeleton for metastatic lesions and can direct further imaging. However, certain cancers can be cold on bone scan. For example, multiple myeloma or aggressive lytic lesions, such as those seen with lung cancer, do not allow for surrounding bone reaction and, therefore, do not result in uptake on bone scan. Thus, a negative bone scan does not negate the possibility of other sites of bony disease. Systemic screening should be guided by the patient’s medical history and physical examination.
The 3-D imaging studies are helpful for planning. Magnetic resonance imaging (MRI) and computed tomographic (CT) scans have different capabilities and should be used selectively. Contrast is unnecessary when imaging metastatic disease. Magnetic resonance imaging of the hip and/or pelvis has the advantage of showing marrow and, therefore, better defines the intramedullary extent of tumor within the pelvis. However, marrow signal abnormalities seen on MRI scans are not necessarily indicative of tumor tissue, and can be caused by radiation- or chemotherapy-induced marrow edema or to a postradiation change. This fact must be considered when using MRI for surgical planning. These images also reveal the soft-tissue extent of the tumor, which can be helpful in planning to debulk disease [15, 16]. In the rare case of a solitary metastasis when curative resection is contemplated, an MRI scan can define the extent of the tumor, allowing for wide resection of all involved tissue. However, MRI is less effective than CT in defining cortical bone involvement and in assessing the extent of mechanical compromise of the bone. A CT scan defines both cortical and cancellous bone involvement and gives a better indication of mechanical insufficiency. It can also provide information regarding the soft-tissue extent of the lesion, albeit with less detail than from MRI scans. Thus, CT is the study of choice for imaging metastatic acetabular lesions.
Patients with a history of cancer and a solitary bone lesion without a prior diagnosis of bony metastatic disease require a biopsy to confirm the origin of the bone lesion. Primary bone sarcomas can occur in the same patient population who presents with metastatic disease. For example, Paget sarcoma, postradiation sarcoma, and chondrosarcoma can all present with a lytic or mixed lytic-blastic lesion, or with a pathological fracture. Paget disease can also harbor myeloma or a metastasis that can only be confirmed by biopsy. The blastic lesions associated with prostate cancer metastasis also can mimic pelvic Paget disease. Metabolic bone disease also occurs within older patient populations (ie, brown tumor of hyperparathyroidism or osteomalacia), each of which can present with multiple skeletal lesions mimicking metastasis. Therefore, establishing the diagnosis before surgical intervention can avoid potential surgical mismanagement of resectable and curable primary tumors or overtreatment of metabolic lesions.
3 Classification
An effective classification system for acetabular lesions should combine the anatomical pathology of the lesion with the surgical intervention required to address it in a complete, linearly progressive, and logical fashion. Several systems are available, each with various advantages for addressing oncological problems. Systems that deal with other traumatic and disease conditions, such as failed arthroplasty [17], are not as relevant to oncology. Harrington [4] originally reported on a four-class system to define the acetabular lesion and direct the reconstruction. Class I patients had structurally intact lateral cortices and superior and medial walls and were reconstructed with a conventional cemented total hip arthroplasty, with or without use of medial metallic mesh. Class II patients had a deficient medial wall but with the superior wall (roof or dome) and lateral cortices intact, and were reconstructed with a flanged acetabular component. Class III patients with deficiencies in the superior wall, medial wall, and either one or both lateral cortices were reconstructed with a flanged acetabular component supported by threaded Steinmann pins and cement foundation. Class IV patients required tumor resection for cure and were reconstructed as outlined for Class III patients, or by autoclaving and reimplanting the segment of resected hemipelvis into which an acetabular component is fixed [4]. However, this system does not include all potential lesions and anatomical combinations, nor does it flow linearly with regard to extent of disease. Thus, it is less intuitive and difficult to use.
The American Academy of Orthopaedic Surgeons (AAOS) has defined a classification system for acetabular defects [18], specifically for lesions associated with osteolysis in total hip arthroplasty. Lesions are divided into five categories based on type and location. The classification incorporates whether the defect is segmental or cavitary, central or peripheral. Type IV lesions indicate a pelvic discontinuity. These lesions were subsequently reclassified/subclassified by Berry et al [19] into groups depending on the cavitary or segmental nature of the lesion, as well as lesions associated with radiation. This classification system focuses on the anatomy of the lesion but does not progress linearly, with segmental defects presented earlier in the classification than cavitary defects. Another weakness of the AAOS classification system is the incorporation of factors unrelated to the anatomy of the lesion (eg, prior radiation). Finally, this system does not subclassify or further define combined defects, which have a significant impact on the extent and type of reconstruction. Therefore, the AAOS classification system is cumbersome and difficult to use in metastatic disease cases, and it does not define the type of reconstruction required to address a lesion.
A classification system developed by Memorial Sloan-Kettering Cancer Center for metastatic acetabular disease seeks to combine the strengths of the aforementioned classifications (ie, the reconstructive focus of the Harrington system and the completeness and anatomical definition of the AAOS system). The Metastatic Acetabular Classification (MAC) system identifies each structural deficiency based on the anatomical location of the lesion ( Fig 2.15-2 ) and couples each classification with the appropriate reconstructive technique ( Table 2.15-2 ). Four anatomical sections are evaluated: the dome, the medial wall, the anterior column, and the posterior column, with interventional considerations for involvement of either one or both columns. Based on preoperative radiographic studies, the bone in each region is defined as either sufficient or insufficient based on its ability to support an acetabular component. A region is considered insufficient if it contains a fracture, segmental bony defect, or major cavitary defect. Intraoperative confirmation of bone integrity is necessary before proceeding with the reconstructive plan. If an additional area is found to be incompetent, or an area previously deemed incompetent is found to be structurally sufficient, then the reconstruction is altered accordingly to reflect the change in status [20].
A cavitary defect involving the acetabulum without disruption of the mechanical stability of the subchondral bone can be addressed with a bipolar hemiarthroplasty in instances a lesion of the proximal femur requires surgical intervention. If a periacetabular lesion is present where the articular congruity of the acetabulum is maintained, but which is symptomatic despite an adequate course of radiation therapy, direct cementation of the lesion can be performed. Pain relief is achieved by supporting the bone in this region, and possibly through the thermal effect of the cement on tumor and cytokine pain pathways. Cementation can be done using either an open technique, in which the lesion is curetted and packed with cement or with radiographically guided percutaneous injection of cement into the lesion. Dangers of the percutaneous technique include cement extravasation, either into the hip joint, with resulting disruption of the articulation and cartilage damage, or outside of the bony confines of the pelvis, with potential sciatic nerve or other soft-tissue impingement [21, 22].
Lesions resulting in a structurally incompetent acetabulum with adequate bone maintained in the ipsilateral hemipelvis to support internal fixation can be stably reconstructed using a combination of pins or screws and cement with a cemented acetabular component. Lesions involving the medial wall require additional support with a flanged acetabular component or antiprotrusio ring. Of note, lesions involving the obturator foramen (region for type III pelvic resection, as described by Enneking and Dunham [23]), with or without extension to the inferior aspect of the acetabulum, can result in significant pain and symptoms that are not relieved by total hip arthroplasty ( Fig 2.15-3 ). This is due to soft-tissue and nerve (femoral or obturator) impingement by the tumor in the confines of this region as these structures exit the pelvis.
Extensive tumor involvement in the acetabulum and inferior aspect of the pelvis (types II ± III pelvic resections) may require excision of this aspect of the pelvis and reconstruction of the hip with a saddle prosthesis ( Fig 2.15-4 ). This type of prosthesis is implanted into the femur using a femoral stem interface. The saddle’s proximal component allows rotation and articulates with a notch made in the residual ilium [24]. This type of reconstruction depends on adequate proximal iliac bone to support the articulation of the prosthesis and a stable sacroiliac joint. Aboulafia et al [24] reported on the results of this procedure in 17 patients, including nine with metastatic/systemic disease. A total of 12 (71%) of 17 patients had an excellent or good result. At the latest follow-up (range, 15–62 months), nine patients were still living (three of whom had metastatic disease), all with an excellent or good result. An additional indication for segmental pelvic resection and saddle reconstruction is a contained solitary lesion (ie, plasmacytoma or delayed-onset renal cell carcinoma metastasis) that is being widely excised for cure [25–28]. Large lesions with extensive involvement of the hemipelvis and disruption of the sacroiliac joint may be resected and reconstructed with a pelvic endoprosthesis and total hip arthroplasty. In certain instances, depending on the clinical circumstance, extensive pelvic lesions may best be addressed with a Girdlestone procedure, particularly in bedridden patients with pain at rest and a life expectancy of less than 3 months.
Related posts:
2.17 Posttraumatic acetabular dysplasia
2.12 The elderly patient with an acetabular fracture
2.14 Total hip arthroplasty after acetabular fracture
2.15 Pathological pelvic fractures and acetabular reconstruction in metastatic disease
2.13 Primary total hip arthroplasty for acetabular fracture
2.16 Acetabular fracture in the pediatric patient: the immature skeleton
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
