Metastatic Bone Disease: Pelvis

Metastatic disease to the pelvis can lead to structural instability and debilitating pain. Lesions are classified by biologic subtype and location based on the Enneking and Dunham system: iliac (Type I), periacetabular (Type II), and rami (Type III), with the sacral region added as type IV. The metastatic acetabular classification is described for periacetabular lesions (Enneking. The anatomic considerations in tumor surgery: pelvis. In: Enneking WF, editor. Musculoskeletal tumor surgery, vol. 2. New York: Churchill Livingstone; 1983. p. 483–529; Healey and Brown Lenard. Pathologic pelvic fractures and acetabular reconstruction in metastatic disease. In: Tile M, Helfet DL, Kellam JF, Vrahas M, editors. Fractures of the Pelvis and Acetabulum. New York, NY, Thieme Publishers, 2015, pp. 835–848). Three-dimensional imaging of the lesion is essential to adequately assess the anatomy and structural stability of the pelvis. Type I and Type II lesions involving the posterior column typically lead to issues with structural stability. Most cases of pelvic metastatic disease can be managed nonoperatively with pain management and radiation therapy. Occasionally, however, due to intractable pain, compromised pelvic stability, or (rarely) for the reduction of oncologic disease burden, surgical intervention is indicated. Surgical 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. When appropriately indicated, percutaneous augmented cementoplasty can provide a viable alternative to open surgery with less surgical morbidity. For open procedures, 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 is variability in reconstruction methods after resection of Type II lesions with many viable options, including percutaneous augmented cementoplasty, augmented arthroplasty reconstruction including cement-rebar constructs, and resection arthroplasty. Type IV lesions that require resection of greater than 50% of the sacroiliac joint compromise pelvic stability and often require stabilization 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 utilized. While surgical morbidity can be significant, appropriate treatment of pelvic metastatic lesions has been shown to improve patient quality of life. As such, 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.