Metastatic bone disease: Pelvis

Metastatic disease to the pelvis can lead to structural instability and debilitating pain. Lesions are often quite large at the time of diagnosis, as the size of the pelvis and elastic nature of the peri-pelvic organs often result in few symptoms of mass effect for smaller lesions. Lesions are classified by biologic subtype and location based on the system of Enneking—iliac (Type I), periacetabular (Type II), rami (Type III), and sacrum (Type IV) [1]. Advanced 3-dimensional imaging of the lesion is essential to adequately assess the anatomy and structural stability of the pelvis. Only posterior column Type I and Type II lesions typically lead to issues with structural stability. The majority of cases of pelvic metastatic disease can be managed nonoperatively with pain management and radiation therapy, as most are at least moderately sensitive to radiation. Occasionally, however, due to intractable pain, compromised pelvic stability, or (rarely) for the reduction of oncologic disease burden, surgical intervention is indicated. These interventions are divided into intralesional procedures such as curettage with or without adjuvant therapies and possible cemented reconstruction; and wide, extralesional procedures including internal and external hemipelvectomies. The extended ilioinguinal approach can be used for most lesions, in addition to the anterolateral or posterior approaches to the hip for periacetabular lesions. As most Type I, III, and IV lesions do not compromise the structural integrity or weight-bearing capacity of the patient, intralesional and extralesional resections are typically followed with no attempt at reconstruction. Conversely, there has been much debate over reconstruction methods after resection of Type II lesions and many options exist, ranging from custom arthroplasty implants to allograft reconstructions to cement-rebar constructs to simply leaving a flail hip. Type IV lesions that require resection of greater than 50% of the sacroiliac joint compromise pelvic stability and therefore often require hardware to prevent dissociation and limb length discrepancy. In all cases, wound closure with adequate soft tissue coverage is critical, as complications such as dehiscence, infection and herniation can be devastating. If the wound cannot be closed without significant tension, a flap should be used. While morbidity for these surgeries is significant, treatment of these lesions has been shown to improve patient quality of life. The benefits of surgery should always be weighed against the risks and life expectancy of the patient prior to proceeding with surgery. As medical advances have increased patient survival for many types of metastatic cancer, orthopedic oncologists must now evaluate and hone our resection and reconstruction techniques to achieve longer lasting, commensurate results.