A hip fracture caused by metastatic cancer is termed a pathological fracture, distinguishing it from a break caused by significant trauma. This complication arises when cancer cells spread from a primary tumor elsewhere in the body to the bones of the hip, typically the upper femur or pelvis. A pathological hip fracture is a serious event that severely limits a patient’s mobility and quality of life.
The Mechanism of Pathological Fracture
Metastatic cancer cells disrupt the natural process of bone remodeling, which normally maintains bone strength through a balance of breakdown and formation. Bone strength is compromised when cancer cells interfere with osteoclasts, which break down old bone, and osteoblasts, which build new bone. This imbalance results in localized areas of structural weakness within the bone tissue.
Two primary types of bone lesions result from this disruption: osteolytic and osteoblastic metastases. Osteolytic lesions, which are more common, occur when tumor cells over-activate osteoclasts, leading to excessive bone resorption and the creation of weak spots. Conversely, osteoblastic lesions stimulate osteoblasts to produce disorganized, structurally unsound tissue, resulting in dense, sclerotic areas prone to breaking. Cancers that commonly metastasize to the bone include those originating in the breast, lung, prostate, kidney, and thyroid.
Identifying Warning Signs and Assessing Risk
The most common clinical indicator of an impending pathological fracture is pain that progressively worsens, especially with weight-bearing activities. This discomfort may initially be mild but becomes constant and is not relieved by rest. This signals that the bone is under abnormal stress from the growing tumor.
Clinicians use various imaging techniques to detect these lesions and evaluate the risk of fracture. Plain X-rays often reveal the characteristic lytic or blastic patterns of metastatic bone destruction. MRI or CT scans provide more detailed information on the extent of bone and surrounding soft tissue involvement. An important concept is the “impending fracture,” which describes a lesion weakened enough to be at high risk of breaking spontaneously or with minimal force.
To objectively quantify this risk, physicians often use scoring systems such as the Mirels score. This score combines factors like the lesion’s location, size, X-ray appearance, and the severity of the patient’s pain. A high score indicates a significant risk of fracture, often prompting the need for prophylactic surgical intervention. For instance, a score of nine or higher suggests the risk is high enough to warrant preventative stabilization.
Stabilization and Treatment Strategies
Treatment for metastatic hip involvement is divided into two main categories: prophylactic surgery (stabilization before a break) and intervention to repair an acute fracture. Prophylactic stabilization is performed when a lesion significantly compromises the bone’s structural integrity, such as with a high Mirels score. This surgery often involves inserting an intramedullary rod or nail down the center of the femur to provide immediate support across the weakened area.
When an acute, complete fracture has occurred, the surgical approach is tailored to the location and extent of the damage. Fractures in the femoral head and neck often require joint replacement, such as hemiarthroplasty or total hip arthroplasty, because the compromised blood supply makes healing unlikely. For breaks lower down the femur, internal fixation using plates, screws, or rods, often augmented with bone cement for immediate stability, is the preferred method. The goal of any surgical intervention is to allow the patient to bear weight as soon as possible.
Beyond surgery, palliative radiation therapy is a cornerstone of treatment. Radiation is highly effective for reducing pain and can slow tumor growth at the bone site, helping to maintain stability or prevent further destruction. Systemic therapies, including chemotherapy, hormone therapy, and bone-modifying agents, are also integrated to manage the underlying cancer and reduce the risk of future skeletal events.
Recovery and Mobility After Intervention
The recovery phase focuses on maximizing the patient’s functional independence and improving comfort. Given the context of advanced disease, the primary goal of rehabilitation is palliative, centered on maintaining mobility rather than striving for a complete cure. Physical therapy is initiated quickly after surgery, often within the first few days, to encourage early weight-bearing and prevent complications from prolonged immobility.
The ability to walk again after surgery is associated with a better quality of life and, in some cases, improved survival outcomes. Rehabilitation programs are managed to ensure the stabilized hip can withstand necessary forces while the patient regains strength and balance. Continued pain management, utilizing medications and non-surgical therapies, remains a high priority. Supportive care services, including psychosocial support, are integrated to help patients manage the physical and emotional challenges of advanced cancer.