The use of endoprosthetic or megaprosthetic implants has gained universal acceptance not only in the oncology community but also in trauma and joint surgeries for complex bone loss cases. The extensile approaches for the DAA not only include access to the proximal femur but also may be readily extended to the knee as may be needed for oncologic cases.

Metastatic disease, myeloma, and lymphoma are the most common causes of massive bone loss in adult patients with bone tumor. Bone sarcomas, including osteosarcoma and Ewing sarcoma, are more common in young adults and adolescents. Biopsy confirmation of tumors is very important to be able to plan the approach, the type of resection, and whether preoperative (neoadjuvant) treatment is necessary. Some of the bone tumors and diseases that are known to have high propensity for bleeding due to vascularity are myeloma, renal cell metastasis, thyroid cancer, and Paget disease. These patients would likely benefit from preoperative arterial embolization to reduce the risk of hemorrhage.

Nononcologic indications from femoral endoprosthetic reconstruction include periprosthetic fractures, revision hip arthroplasty, and comminuted osteoporotic fractures. The only absolute contraindication is an active infection at the surgical site. Relative contraindications for primary bone sarcomas include soft tissue extension around the greater trochanter or sciatic notch and a tumor that extends into the tensor fascia lata (TFL), which would leave poor anterior hip soft tissue coverage for closure. The advantages of the supine-positioned patient include easy intraoperative imaging, anterior column acetabular exposure, direct leg length comparison, and femoral neurovascular bundle exposure.

In oncologic cases, it is important to incorporate the biopsy tracts, particularly in those patients with bone sarcomas to reduce the risk of contamination and recurrence. The location of the tumor often dictates the surgical approach, and, when possible, it is essential to retain the blood supply to the anterior soft tissue structures of the hip (Figure 38.1A and B). The blood supply comes from the sciatic notch, and dissection in this area should be approached cautiously. If the TFL loses its blood supply, it will atrophy and necrose. This will increase the risk of seroma and infection. Midsubstance tears of the TFL muscle should be avoided. When necessary, the TFL may be detached from its origin and safely repaired at the conclusion of the surgery to avoid denervation.

Traditional approaches to the proximal femur have required that the patient be in the lateral decubitus position. Access to the contralateral extremity is very limited compared with the supine position where the other leg is available for comparison or for harvesting a vein for vascular bypass if needed. The planning for a sarcoma resection is different from that for other malignancies in that the goal is to obtain a clear surgical margin. There is no consensus regarding an acceptable margin; however, a 2-cm bone margin may often be obtained without compromising function. With pathologic fractures associated with lymphoma, myeloma, or metastatic disease, surgery is often combined with adjuvant treatment, such as radiation or chemotherapy. The margin is not considered to be as crucial in these patients with systemic forms of bone cancer.

The goals of hip reconstruction for oncology surgery include safe surgical exposure, soft tissue preservation without compromising the tumor margin, joint stability, and a durable reconstruction. Advances in megaprosthetic implants have resulted in better, more user-friendly instrumentation and more femoral stem options (Figure 38.2A and B). Femoral stem options include cemented, press fit, and a combination of a collared stem with ingrowth potential and a cemented stem (hybrid technique). A muscle-sparing approach may be used for tumor surgery, and it is important to avoid injuring the lateral femoral cutaneous nerve (LFCN), which is one of the many advantages of the DAA. By opening the TFL fascial envelope and keeping the deep dissection within this envelope, skillful use of the DAA helps to avoid LFCN irritation and injury.

If the greater trochanter is uninvolved with a tumor, it may be preserved and left in continuity with the vastus origin using a trochanteric slide osteotomy (Figure 38.3). This is easily accomplished with the DAA, and once the trochanter is osteotomized, the proximal femur can be elevated anteriorly and exposed. By keeping the abductors and the vastus lateralis muscle origin attached to the trochanter, minimal repair is necessary at the conclusion of the case. If further femoral exposure is needed, the gluteus maximus tendon insertion may be released, and the sciatic nerve will passively translocate posteriorly with the release of this gluteal sling.

Whichever approach is selected for oncologic resection, it should be performed by a fellowship-trained orthopaedic oncologist and the resection margin should not be compromised by the approach. Surgical planning is highly dependent on preoperative cross-sectional imaging, including magnetic resonance imaging and computed tomographic scans. As yet, there are no studies in the literature looking at the functional outcome as it relates to the surgical approach to the proximal or total femur replacement, although the use of a synthetic monofilament polypropylene mesh such as Marlex, (Once manufactured by C.R. Bard, since 2017 is now marketed as Bard Mesh, BD, Franklin Lakes, NJ, USA) or soft tissue allograft has been reported to improve stability and reduce the incidence of dislocation. Mesh is sutured or anchored around the periphery of the acetabulum and then cerclaged around the proximal femur and sutured to itself while tensioned in a purse-string closure. Additionally, a transfer of the gluteus maximus from its femoral insertion to the anterior capsule and trochanter has also been described. For nononcologic reconstructions, the stability of the hip is highly dependent on the position of the acetabular cup, the femoral head size, and the option for a prosthetic constraint (Figure 38.4). Hemiarthroplasty, also known as bipolar reconstruction, is more common in oncologic cases because the retained labrum and capsule along with the large bipolar head help to reduce the risk of dislocation (Figure 38.5).