The morbidity associated with osseous metastatic lesions of the pelvis and lower extremity can be devastating. Pain and decreased mobility can severely affect the quality of life of patients who are already undergoing other cancer treatments, including radiation and chemotherapy. Because 40% of metastatic disease occurs in the pelvis and 25% in the femur, there is more opportunity for the occurrence of problems that require surgical management. Many patients present with lower extremity pain and difficulty ambulating. Nonsurgical management can include bisphosphonates (also known as diphosphonates) or denosumab, radiation, weight-bearing restrictions, pain medications, and minimally invasive interventional radiology techniques such as acetabuloplasty; however, surgery may be recommended in selected patients. The goals of surgical treatment in lower extremity metastatic disease include stabilization of the bone, palliation of pain, and restoration of mobility. Global considerations in this population, such as the timing of surgery in patients receiving chemotherapy or radiation, often need to be addressed with a multidisciplinary team. By setting appropriate expectations in the patient with metastatic disease, appropriate stabilization and reconstruction can be achieved to restore a patient’s mobility and function while affording appropriate pain relief.

The pelvis is second only to the spine in the occurrence of bony metastasis. The complex anatomy of the pelvis and acetabulum precludes simple identification of which pathologic fractures or metastatic lesions are indicated for surgical intervention. The specific characteristics of the lesion needs to be evaluated critically in regard to biomechanical stability to make appropriate treatment
decisions.¹ Pelvic lesions can be divided into non-weight-bearing portions, such as the iliac wing and the pubis, from the weight-bearing columns and the periarticular area. Non-weight-bearing portions rarely require surgery, whereas selected patients may benefit from surgical intervention for lesions around the acetabulum.

Nonsurgical approaches in the pelvis, including external beam radiation therapy, minimally invasive ablative therapies such as radiofrequency ablation, and cryotherapy, may provide relief in selected patients, although they do not confer structural restoration.² Cementoplasty or acetabuloplasty is a technique where CT-guided probes can be placed within periacetabular pelvic lesions and cement injected into the pathologic defect.³ Published studies have shown the efficacy of these minimally invasive procedures.^3,4 Acetabuloplasty may over time have equivalent pain and functional improvements compared with reconstructive techniques, with fewer complications associated with the initial procedure and subsequent revision interventions.⁴

After initial evaluation of location, the complex anatomy of the pelvis requires cross-sectional imaging. Judet views, often used in trauma evaluations around the acetabulum, generally underestimate the amount of bone loss around the hip joint. CT with three-dimensional reconstructions can help simplify the complexities of the lesion and the structural areas that might be affected. Recently developed three-dimensional modeling can also help plan for surgery and can be used to make physical models from which patient-matched custom implants can be manufactured. Typically, standard off-the-shelf implants and knowledge of various reconstructive options can minimize the need for more expensive custom implants, but in some patients with significant bone destruction and extended life expectancy, the expense can be justified. Surgery in this area can be a difficult undertaking, requiring understanding of multiple approaches as well as implant possibilities.

Fractures of the iliac wing or isolated ischial or pubic ramus fractures can often be treated nonsurgically. These lesions may not be structural because they are not in the weight-bearing axis from the femur through the acetabulum to pelvic columns up to the sacrum. Because they are often nonstructural, the pain associated with them could be related to the tumor itself rather than weight-bearing functional pain. For this reason, these lesions can also be managed with radiofrequency ablation,⁵ embolization, and/or radiation. As the pain improves, treatment with chemotherapy and bisphosphonates can help reverse bone loss while allowing formation of new bone.

Refractory lesions can be managed with surgery with less morbidity than periacetabular lesions. Iliac wing lesions can be approached through the proximal portion of the iliofemoral or ilioinguinal approaches. Anterior ring surgery can be performed via a Pfannenstiel incision. Soft-tissue reconstruction, by bringing muscular planes together and preventing abdominal or pelvic hernias, will minimize early wound healing problems as well as late morbidity from these hernias. Percutaneous screw fixation techniques have been developed to treat patients with nonperiacetabular metastatic bone lesions of the pelvis not amenable to less invasive measures, while avoiding the complications associated with open treatment. A 2022 study demonstrated improvements in patient pain levels, as well as functional improvements, with low levels of complications.⁶

Periacetabular lesions are perhaps the most troublesome lesions to treat in patients with multifactorial pain. After restricted weight bearing, modification of activity levels, administration of oral or transdermal medication, and radiation, selected patients with painful lesions, a good performance status, and a reasonable expected longevity can be offered more aggressive treatment. The goals of acetabular metastatic tumor treatment remain maintenance of ambulatory status and pain control. Advances have been made in less invasive techniques that may improve pain and function. These include percutaneous screw fixation, minimally invasive stabilization, different types of ablations, osteoplasty, or a combination of these options. A 2021 study of patients with metastatic periacetabular disease undergoing minimally invasive stabilization and osteoplasty with or without ablations demonstrated improvements in function and pain control.⁷ Many of these types of procedures can be performed as outpatient procedures, with minimal complications, without delays in radiation or chemotherapy treatment.

Pathologic fractures remain a relative indication for surgical treatment in a patient whose performance status and prognosis do not contraindicate a major surgery. Osteosynthesis alone in patients with metastatic disease is often not sufficient, as metastatic lesions in bone are less likely to heal and are best managed in conjunction with arthroplasty and acetabular reconstruction.

Once surgery is indicated, an anatomic approach to characterizing the defects allows the surgeon to use a systematic way of choosing appropriate reconstruction. Assessing lesion location and size, and area of bone loss, will allow for a more appropriate restoration of mechanical stability. Reconstruction can be accomplished with standard arthroplasty components with
cement augmentation, cement and Steinmann pin fixation, antiprotrusio cages and triflange reconstruction cages, or with a combination of techniques (Figure 1). Polymethyl methacrylate (PMMA) is most often used instead of bone graft because of its immediate stability. The classification system used is the modified Harrington classification, based on the location of the lesion and the type of reconstruction needed. Type 0 nonarticular lesions are nonacetabular and do not penetrate the subchondral plate. They can be iliac, superior, ischial, or pubic and are best treated by curettage, high-speed burr removal, and reconstruction with a combination of PMMA, Steinmann pin, metallic mesh, and plates.

Type I lesions include contained lesions about the acetabulum that retain an intact lateral cortex with superior and medial portions of the acetabulum untouched. Any standard approach that allows access to insert routine arthroplasty components can be used, with the caveat that complete exposure of the lesions should be possible. Cement augmentation in the lesions and rim-fitting acetabular cages are very useful and the most straightforward solution. Furthermore, trabecular metal can be used for a more immediate friction fit if all-cemented components are not used. Screws can also be used to help initial fixation. Cemented components are most often used because of decreased ingrowth potential after irradiation.

Type II lesions have a defect in the medial wall of the acetabulum. Routine acetabular components will not have enough support until the wall has been reconstructed. After appropriate curettage and resection of tumor and nonviable bone, if the defect remains a type II and is not converted to a type III, reconstruction can be accomplished with mesh to support the medial wall and cementation. Steinmann pins can be used in the pubis and ischium to further support an acetabular implant. Antiprotrusio cups can also be used to distribute stresses away from the medial wall for a rim-loaded fit or screw fixation at the periphery, without the use of PMMA.

Type III lesions have loss of both the superior bone and the lateral cortex. These defects also require that the original acetabulum be reconstructed, using cement to make up the area of the diseased bone. After resection, screws or Steinmann pins can be placed through the defect into less involved areas of the pelvis to prepare for cementation, and an acetabular protrusio cup is then cemented over it. Cup-cage constructs can also be used with flanged cages supported by cement and an acetabular cup cemented into the cage. Screws can also be placed through the entire system for support. Depending on the amount of soft tissue released for exposure, a constrained liner can help reduce the risk of dislocation. The durability of these challenging reconstructions is sufficient in these metastatic reconstructions, with a revision surgery rate of 8% at 2 years and 16% at 4 years.⁸

Type IV lesions add inferior loss of bone, leading to pelvic discontinuity. Reconstruction of these defects is similar to that for type III; however, ischial fixation can be used to improve stability of fixation. Some antiprotrusio cages have three flanges, with two flanges to the iliac wing and one to the ischium, fixed with either screws or slotted placement in a trough in the bone. Newer cone acetabular components that obtain fixation purely through the posterior iliac wing may also be used in pelvic discontinuity, obviating the need for ischial support or fixation.^9,10