What Is Pathologic Fracture?
A pathologic fracture arises from bone weakening due to disease, often linked to primary bone cancers, tumors, non-cancerous growths, metastatic spread from other cancers, or metabolic disorders. The core problem underlying pathologic fractures lies in the disruption of typical bone biomechanics triggered by these underlying pathologies.
What Is the Cause of Pathologic Fracture?
Pathologic fractures predominantly result from metastatic cancer, where cancerous cells have migrated to bones from other parts of the body, as opposed to primary bone tumors that originate within the bone itself. The primary cancers that commonly metastasize to bone comprise breast, lung, prostate, thyroid, and renal cancers, with the proximal femur, spine, and pelvis being frequent sites of skeletal metastasis.
While metastatic disease is a frequent cause of pathologic fractures, it is vital not to dismiss the potential of a primary bone sarcoma (cancer that originates in the bone tissue). Although rare, primary bone sarcomas can be highly aggressive, and overlooking them could lead to serious complications.
What Is the Pathophysiology of Pathologic Fracture?
Two distinct types of bone lesions can occur:
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Osteolytic Lesions: The bone lesions are defined by significant bone destruction induced by tumors. This destructive process involves the activation of osteoclasts, specialized cells responsible for breaking down bone tissue. The upregulation of the RANK ligand (receptor activator of nuclear factor kappa beta ligand), produced by the tumor, is critical in stimulating osteoclast activity and subsequent bone resorption.
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Osteoblastic Lesions: These bone lesions are marked by atypical bone formation triggered by tumors. The tumor releases endothelin 1, a peptide hormone that stimulates bone formation. This secretion prompts heightened osteoblastic activity, creating new bone in unconventional patterns and locations.
Osteolytic osteoblastic lesions can compromise bone structural integrity, while abnormal bone formation can disrupt normal biomechanics. These changes render the bone more vulnerable to fractures, increasing susceptibility even under minimal stress.
What Are the Symptoms of Pathologic Fractures?
The symptoms encompass:
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Persistent or sporadic pain can be experienced in the affected bone.
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In certain instances, pathologic fractures might remain asymptomatic or exhibit minimal symptoms until the fracture occurs.
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Patients with underlying malignancies may present with fever or unintended weight loss.
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Depending on the primary carcinoma site, patients might exhibit specific symptoms. For instance, renal cell carcinoma could manifest as urinary abnormalities, whereas lung carcinoma may cause shortness of breath.
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Patients may also experience hypercalcemia, characterized by excessive calcium in the blood. Symptoms can range from subtle cognitive changes like mild confusion to severe manifestations such as cardiac arrhythmias (improper beating of the heart), gastrointestinal disturbances, or renal dysfunction.
How Is Pathologic Fracture Evaluated?
Upon uncovering a pathologic fracture, especially when juxtaposed with an enigmatic lesion, it becomes imperative to embark upon a comprehensive diagnostic journey to ascertain its stage and etiology.
A. Laboratory Analyses:
These should encompass a spectrum of evaluations:
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A comprehensive metabolic panel (CMP), including alkaline phosphatase and serum calcium levels, provides a holistic view of metabolic function.
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A complete blood count (CBC) to assess various blood parameters.
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Coagulation studies are imperative for evaluating blood clotting mechanisms, including prothrombin time (PT) and activated partial thromboplastin time (aPTT).
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Erythrocyte sedimentation rate (ESR) assessment aids in gauging inflammation or underlying malignancies.
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Urinalysis serves to detect any anomalies in urine composition.
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Urinary protein electrophoresis and serum protein electrophoresis enable precise protein analysis.
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Disease-specific markers like prostate-specific antigen (PSA) for prostate cancer and carcinoembryonic antigen (CEA) for gastrointestinal cancer offer targeted insights into potential diagnoses.
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The presence of Bence Jones protein suggests the consideration of multiple myeloma (a cancer that forms in a type of white blood cell called a plasma cell) as a diagnosis.
B. Radiological Assessments:
These encompass a range of crucial analyses:
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X-rays are a cornerstone for appraising pathologic fractures, offering detailed insights into their nature and extent. Lesions exhibiting characteristics such as a diameter exceeding 1.96 inches, periosteal reaction, cortical interruption, and associated pathologic fractures may signify aggressiveness.
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A chest radiograph is imperative for evaluating lung cancer.
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Consideration of CT (computed tomography) scans of the abdomen, chest, and pelvis aids in staging, while local CT scans of bone lesions offer localized insights. MRI (magnetic resonance imaging) scans are invaluable for assessing neurovascular and soft tissue involvement.
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Whole-body bone scintigraphy serves to identify areas of osteoblastic activity indicative of ongoing bone repair.
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In cases of multiple myeloma, a skeletal survey involving X-rays of multiple bones is warranted.
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Mammography plays a crucial role in the evaluation of breast cancer.
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Positron emission tomography (PET) scans excel at detecting metabolic activity throughout the body and offer comprehensive diagnostic capabilities.
C. Biopsy:
Biopsy procedures involve the extraction of a minute tissue sample for microscopic examination. Among the three primary types are open biopsy, fine-needle aspiration (FNA, a diagnostic procedure that involves the removal of fluid, cells, or tissue with a thin needle for examination under a microscope), and core-needle biopsy, each tailored to specific diagnostic needs.
What Is the Management of Pathologic Fracture?
1. Impending Pathologic Fractures:
In cases of impending pathologic fractures, where bone integrity is compromised, there is a heightened risk of fracture even with minimal force. Management strategies encompass prophylactic fixation, wherein the weakened bone is reinforced preemptively with internal fixation before fracture onset. This approach offers the advantage of mitigating the risk of a complete fracture, which can entail heightened pain and pose surgical challenges during management.
2. Pathologic Fractures:
The treatment modality for pathological fractures hinges on the specific characteristics of the underlying lesion. A fracture's capacity to mend is intricately tied to the nature of the underlying disease, with healing rates varying across different conditions. Notably, fractures stemming from myeloma exhibit superior healing potential compared to those attributed to metastasis from lung cancer. Hence, accurate diagnosis assumes paramount importance in formulating effective treatment strategies. In instances of multiple myeloma, the fixation of fractures often necessitates screws and plates, which suffice to stabilize the affected bone. Conversely, fractures induced by lung cancer demand more extensive interventions, often requiring the implementation of bone-replacing prostheses. The chosen implant should not merely bear the load but distribute it effectively, ensuring durability, immediate stability, and sufficient extension beyond the affected region by at least two cortical bone diameters.
Following surgical intervention, the adjunctive use of radiotherapy is contemplated to impede disease progression within localized regions. However, this approach carries potential complications, albeit rare, such as radiation-induced fractures, necessitating lifelong monitoring to address any emerging issues preemptively. Additional complications, including local tissue necrosis and wound healing disturbances, warranting vigilant management and follow-up care, may manifest. Following surgical fixation, patients are encouraged to commence physical therapy promptly, aiming to restore mobility swiftly and often advancing to weight-bearing activities as tolerated. Postoperative anticoagulation is typically prescribed for individuals who have undergone lower-extremity surgery to mitigate thrombotic risks. Over the long term, the proactive administration of bisphosphonates is highly advised to attenuate the incidence of skeletal-related events (SREs) and deter malignancy-induced hypercalcemia, thus optimizing patient outcomes.
Conclusion:
Pathologic fractures present a formidable clinical obstacle, underscoring the importance of comprehending their etiology and implementing suitable management approaches. Thus, the pivotal steps of diagnosis, assessment of severity and extent, and implementation of appropriate interventions are imperative for effective fracture management. Treatment options span surgical interventions, including stabilization procedures, to systemic therapies tailored to counteract the underlying disease pathology. Rehabilitation and supportive measures are indispensable in facilitating functional restoration and enhancing the quality of life following fracture occurrence.
