Pathologic fracture

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Introduction

A pathologic fracture through a bone tumor is the most dramatic clinical presentation in musculoskeletal oncology. Pathologic fractures are not associated only with malignant or aggressive bone tumors. In the pediatric population, fractures most commonly occur through benign active lesions such as non-ossifying fibroma, unicameral bone cyst, and fibrous dysplasia. These tumors, which are generally latent lesions in adults, may be active lesions in children, causing the fracture by weakening the bone through erosion of the cortex (for example, unicameral bone cyst), or by acting as a point of stress concentration within the bone.

Malignant tumors presenting with pathologic fracture usually prove to be challenging management problems. Malignant pathologic fractures may present in the following three ways:

Fractures through a primary malignant bone tumor

Fractures through solitary metastatic lesions without a known primary site of disease

Fractures through metastatic disease in patients with a known primary cancer diagnosis.

The implications of each of these three clinical situations will be discussed later in this section.

History

When obtaining the patient history, consider:

Prior symptoms. Pain present for a prolonged period prior to fracture may actually be a positive: It suggests a slow-growing lesion. In pediatric patients in particular, there may have been no symptoms from an active bone tumor prior to the fracture. In older patients, the fracture may be the latest manifestation of a long history of metastatic bone disease.

Known primary cancer or symptoms that may suggest a primary malignancy. If an adult patient has a known primary malignancy, determine whether he or she has received or is receiving systemic therapy, and whether he or she is known to suffer from extensive bone or visceral metastases.

Prior radiation to the site of fracture

Extent of metastatic disease, if surgery is being considered to manage a metastatic pathologic fracture

Symptoms related to cervical spine involvement; lung, liver, and CNS metastatic disease; and possible symptoms of hypercalcemia

Physical Examination

In assessing the local site of a pathologic fracture:

Ensure that the skin is intact and that there is no evidence of distal neurovascular impairment. Open pathologic fractures and pathologic fractures with neurovascular impairment are rare because these are generally not high-energy injuries.

Evaluate the stability of the fracture.

Determine the extent of physiological impairment caused by the injury. Evidence of articular involvement should be evaluated, especially in pathologic fractures occurring through aggressive or malignant primary tumor, which commonly effect the epiphyseal-metaphyseal portion of the bone. As a result, they more commonly affect the joint than metastatic pathologic fractures.

Complete a general examination in older patients. If there is no known primary malignancy elsewhere, the common sites of tumors that metastasize to bone should be evaluated (thyroid, breast, lungs, kidney and prostate). Evidence of widespread metastases should be assessed by examining for hepatic or splenic enlargement, CNS signs, and changes of pulmonary osteoarthropathy.

Investigations

In discussing investigations of pathological fractures, it is also necessary to describe management goals since in many cases, biopsy of the pathological fracture is combined with stabilization of the fracture. However, appropriate investigation should precede surgery.

Order routine blood work, including complete blood count, erythro sedimentation rate, (CBC, ESR, Ca2+, PO4, alkaline phosphatase, serum immune electrophoresis, and PSA) if there is no known primary cancer in an adult patient.

Obtain liver function and coagulation tests in a patient expected to have surgery.

Obtain a total body bone scan to identify wide spread bony metastases if there is no known primary cancer and the patient is not confined to traction as a result of an unstable lower extremity fracture

Order chest CT, mammogram, and abdominal ultrasound or CT as appropriate to evaluate the patient for an occult primary cancer. If the patient is known to have metastatic bony disease, routine and flexion/extension views of the cervical spine are necessary prior to intubation.

Obtain plain radiographs. The interpretation of the radiographic features of the underlying lesion that caused the fracture is critical to the diagnosis of the condition and planning of further management.

Order MRI or CT imaging of the local site of fracture for patients without a known cancer diagnosis, especially if the fracture has occurred through a solitary bony lesion. Imaging may demonstrate a soft tissue mass or matrix formation that suggests that the lesion is likely a primary aggressive or malignant tumor.

Plan for Management

Following evaluation of these investigations, further clinical management will follow one of the following pathways:

Pediatric fractures. If the fracture has occurred through a unicameral bone cyst or other benign active lesion with potential for healing, it may be best to allow the fracture to heal and then attempt to eradicate the lesion (for example, injection of steroids or marrow into the unicameral bone cyst following completion of fracture healing). Some pediatric pathologic fractures through non-ossifying fibromas, eosinophilic granuloma, and small bone cysts may actually provide a stimulus for healing of the lesion without further intervention. In more destructive lesions, such as fibrous dysplasia of the proximal femur, surgical intervention may be necessary to prevent or correct deformity.

Adolescents and young adults with fractures through benign aggressive tumors. An aggressive tumor presenting with a fracture, such as a giant cell tumor or aneurysmal bone cyst, causes three particular management problems. First, the tissue disruption, necrosis, and early callus formation that result from the fracture may make histologic diagnosis difficult. Second, it is difficult to completely remove all traces of the aggressive lesion after pathologic fracture has spread tumor cells through the soft tissues. Finally, it is difficult to adequately restore the skeletal anatomy after fracture of the severely eroded bone. This is especially problematic because most aggressive tumors occur in the epiphyseal-metaphyseal bone and the pathological fracture often involves the articular surface. Therefore, these lesions should be referred to sub-specialized musculoskeletal oncology centers for diagnosis and management. The difficulty in diagnosis requires sub-specialty pathology expertise, and the problem of tumor eradication and joint reconstruction is beyond the capacity of most general orthopaedic surgeons. Pathologic fractures occurring in young adults with probable aggressive tumors should be biopsied and treated by a sub-specialist.

Pathological fracture through probable primary malignancy of bone. Pathologic fractures through primary malignant bone tumors are usually recognized by one or more of the following features:1) the patient is younger than expected for metastatic disease to the bone, 2) the lesion is solitary, 3) a soft tissue mass is evident on cross-sectional imaging, and 4) radiological detection of matrix formation by the tumor suggests a malignant bone- or cartilage-forming tumor. The diagnosis of fracture in a primary sarcoma of bone is simple to make in an 18 year old who has suffered a pathologic fracture through a solitary lesion that is producing abundant osteoid in a large soft tissue mass. In this situation, it is obvious that pathologic fracture has occurred through an osteosarcoma. The diagnosis is not as obvious if the patient is middle aged with a pathologic fracture through a malignant fibrous histiocytoma of bone that produces no matrix. The reason for emphasizing an awareness of pathologic fractures through a primary bone sarcoma is that the management of pathologic fractures is dramatically different in sarcoma and metastatic cancer. Patients presenting with pathologic fractures through sarcomas of bone may be cured by complete excision of the primary bone malignancy, which might require amputation in some cases of advanced local disease. Patients with metastatic disease to the bone, on the other hand, will not be cured if the pathologic fracture is excised (by definition, they have cancer present elsewhere in the body) and emphasis is placed on rapid palliative management and repair (not generally excision) of the fracture. The incidence of pathologic fractures through sarcoma of bone is much lower than the incidence of fractures through metastatic cancer; therefore, it is critical for the clinician to have an awareness of fractures through sarcoma when the patient presents with a fracture through a solitary bone malignancy.

Pathological fracture through solitary probable metastatic lesion; no primary cancer known. If the clinical situation and radiographic appearance are highly suggestive of a lesion that is a solitary metastatic lesion rather than a primary bone tumor, the clinician has two treatment priorities: diagnosis of the lesion and management of the fracture. If a primary malignancy has not been discovered by the investigations described above, a diagnostic biopsy at the fracture site is indicated. If the fracture requires fixation, it may be possible to perform this procedure at the time of biopsy, as long as the frozen section confirms the diagnosis of metastatic disease. In the patient with a pathologic fracture without a known cancer diagnosis, the surgeon should inform the pathologist, who will ensure that the tissue is processed appropriately to permit a full diagnostic workup that could identify the primary tumor site if possible.

Pathological fracture through metastatic lesion, with known cancer diagnosis. This final situation for patients presenting with pathologic fractures through a metastatic bone tumor is the most common in older adults. These patients have a known cancer diagnosis and have a fracture through a site of obvious metastatic disease. Often there is generalized skeletal disease evident on radiographs at the time of fracture. These patients require palliative orthopaedic care rather than establishment of a diagnosis, and in many cases -- especially with lower extremity lesions -- this palliative care will require surgery.

The Other Presenting Complaints