Managing proximal femoral metastases

Metastases to the proximal femur are becoming more common as the population ages and oncological treatment for malignancies improves. More patients are living longer with malignancies, allowing more opportunities for the development of metastatic bony disease. Patients can develop bony metastases many years after treatment of the primary malignancy. Patients with carcinoma of the breast, for example, have a life expectancy approaching normal at about 25 years from presumed successful treatment of the primary disease. Although a patient who presents with a bony malignancy and a history of malignant disease must not automatically be assumed to have metastatic disease, as a second malignancy may occur. It must be remembered that a patient who has a history of malignancy has an increased risk of another malignancy compared to the general population. Metastases of the proximal femur represent significant nursing problems in terms of pain and loss of mobility. It is tempting to proceed rapidly to surgical stabilization.

The presence of a presumed metastasis to the proximal femur requires careful assessment. If the patient has other confirmed metastases, the diagnosis is easily achieved, but a solitary lesion requires careful investigation, including local and systemic imaging, and biopsy according to orthopedic oncological principles. The presence of a proximal femoral metastasis may be an incidental finding, e.g., on follow-up investigations, or may present clinically as pain or fracture. On identification of a proximal femoral fracture, management depends on many factors: what is the life expectancy of the patient, can the bony metastasis be treated medically, has the fracture occurred or is it likely to occur, is the lesion solitary, might there be a survival advantage on resecting the metastasis, and is the lesion lytic or sclerotic. When a metastatic lesion to the proximal femur has been confirmed, it must be remembered that the biology of that metastatic disease has overwhelmed the patient’s normal healing mechanism. It may be possible to alter the biology of the metastasis by adjuvant treatment with chemotherapy, radiotherapy, or immunotherapy and allow for some healing of the lesion to occur, though it must be remembered that the adjuvant treatment itself will alter the normal bone healing, and careful monitoring will be needed. If the lesion is not amenable to medical treatment or a fracture has occurred (medical treatment will not allow fracture healing to take place), surgical treatment may be considered. Several principles need to be considered. There is no point in considering surgery if the recovery time from that surgery is greater than the life expectancy of the patient, the reconstruction used itself must have a ‘life expectancy’ greater than the patient (normal methods of bone fixation are designed for traumatic fracture where bone healing occurs and are not intended for long term fixation), if the lesion is solitary would complete excision of the metastasis (as would be the case for example with primary bone tumor) improve patient survival. In those patients in whom a metastasis of the proximal femur has been identified, an assessment needs to be made of the risk of fracture occurring either at presentation or during medical treatment. There are many scoring mechanisms to assess the risk of fracture occurring. The most commonly used system is that described by Mirel in 1989,^[1] in which site, pain, size, and radiographic appearance are scored. A score of 7 or less indicates a low risk of fracture, whereas a score of 9 or more indicates a high risk of fracture. If a patient has a low risk of fracture, then careful monitoring is appropriate; if a patient has a high score or an increasing score, then surgical intervention would be appropriate. Patients with solitary metastases from breast or renal malignancies, particularly in those with long disease-free intervals, may benefit from complete excision of the metastasis in terms of increased survival, and even in some cases, such surgery may be curative. Those patients with multiple metastases or short disease-free intervals are probably in a palliative situation. In such cases, an assessment of life expectancy is required in order to determine which type of surgery is required. There are many systems available for assessing life expectancy. If life expectancy is <6 weeks, then it would probably be appropriate to avoid surgery. If a patient has a life expectancy of <6 months, then trauma implants may be appropriate, plus adjuvant therapy, for example, post-operative radiotherapy. Published studies have shown that if a patient survives longer than 6 months, there is a high risk of failure of the implant, either by breakage or cutting out of the host bone, e.g., the femoral head. It should be remembered that these lesions/fractures will not heal.^[2] Should this occur, then revision surgery would be required, possibly in the form of arthroplasty surgery or proximal femoral replacement. Such revision surgery is more prone to failure itself and subjects the patient to a second procedure. It has been shown that use of arthroplasty surgery as the initial surgery in appropriate patients, whilst more expensive initially, is cost-effective in terms of avoiding repeat surgery and hospital costs. The appropriate use of arthroplasty surgery is both advantageous to the patient and the treating institution. There are, however, some considerations. Uncemented implants should not be used, as the malignant process and adjuvant treatment may compromise the host bone biology.^[3] It also allows for rapid mobilization. If a stemmed arthroplasty is to be used, then imaging of the entire femur is mandated to ensure that there is no further distal metastasis. If a hip replacement does not allow for resection of the diseased bone, then a proximal femoral replacement may be required. An assessment of the pelvis is also required if there is a metastatic lesion of the acetabulum or if there is evidence of joint involvement with tumor. Consideration needs to be made as to the use of a cemented acetabular replacement.^[2] Treatment of proximal femoral metastases is complex and depends on multiple factors, including patient and tumor biology. Patients’ outcomes benefit from a multidisciplinary team approach involving medical, surgical, and radiology clinical teams. It must be remembered that it is inappropriate to proceed rapidly to surgical intervention and that the circumstances of each patient need to be considered, and that, as surgeons, we cannot rely on biology to heal these lesions. Furthermore, the definition of prosthetic success is that the implant lasts longer than the patient.