Pathologic Fractures

DEFINITION

A pathologic fracture is one that occurs when the normal integrity and strength of bone have been compromised by invasive disease or destructive processes.
Causes include neoplasm (primary tumor or metastatic disease), necrosis, metabolic disease, disuse, infection, osteoporosis, alteration of normal bone repair mechanisms or iatrogenic causes (e.g., surgical defect).
Fractures more common in benign tumors (vs. malignant tumors).
- Most are asymptomatic before fracture.
- Antecedent nocturnal symptoms are rare.
- Most common in children:
  - Humerus
  - Femur
  - Unicameral bone cyst, nonossifying fibroma, fibrous dysplasia, and eosinophilic granuloma are common predisposing conditions.
Primary malignant tumors
- These are relatively rare.
- Osteosarcoma, Ewing sarcoma, chondrosarcoma, malignant fibrous histiocytoma, and fibrosarcoma are examples.
- They may occur later in patients with radiation-induced osteonecrosis (Ewing sarcoma, lymphoma).
- Suspect a primary tumor in younger patients with aggressiveappearing lesions:
  - Poorly defined margins (wide zone of transition)
  - Matrix production
  - Periosteal reaction (Codman triangle)
  - Large soft tissue component
- Patients usually have antecedent pain before fracture, especially night pain.
- Pathologic fracture complicates but does not mitigate against limb salvage.
- Local recurrence is higher.
Patients with fractures and underlying suspicious lesions or history should be referred for evaluation and possibly biopsy.
Always obtain a biopsy of a solitary destructive bone lesion, even in patients with a history of primary carcinoma, before proceeding with definitive fixation.

MECHANISM OF INJURY

Pathologic fractures typically occur as a result of minimal trauma or even during normal activities.
Alternatively, pathologic fractures may occur during high-energy trauma involving a region that is predisposed to fracture.

CLINICAL EVALUATION

History: Suspicion of pathologic fracture should be raised in patients presenting with fracture involving:
- Normal activity or minimal trauma
- Excessive pain at the site of fracture prior to injury
- Patients with a known primary malignant disease or metabolic disease
- A history of multiple fractures
- Risk factors such as smoking or environmental exposure to carcinogens
Physical examination: In addition to the standard physical examination performed for the specific fracture encountered, attention should be directed to evaluation of a possible soft tissue mass at fracture site or evidence of primary disease such as lymphadenopathy, thyroid nodules, breast masses, prostate nodules, and rectal lesions, as well as examination of other painful regions to rule out impending fractures.

LABORATORY EVALUATION (TABLE 5.1)

Complete blood cell count (CBC) with differential, red blood cell indices, and peripheral smear
Erythrocyte sedimentation rate (ESR)
Chemistry panel: electrolytes, with calcium, phosphate, albumin, globulin, alkaline phosphatase
Urinalysis
Stool guaiac
Serum and urine protein electrophoresis (SPEP, UPEP) to rule out possible myeloma
Twenty-four-hour urine hydroxyproline to rule out Paget disease
Specific tests: thyroid function tests (TFTs), carcinoembryonic antigen (CEA), parathyroid hormone (PTH), prostate-specific antigen (PSA)

TABLE 5.1 Disorders Producing Osteopenia

	Laboratory Value
Disorder	Serum Calcium	Serum Phosphorus	Serum Alkaline Phosphatase	Urine
Osteoporosis	Normal	Normal	Normal	Normal Ca
Osteomalacia	Normal	Normal	Normal	Low Ca
Hyperparathyroidism	Normal to high	Normal to low	Normal	High Ca
Renal osteodystrophy	Low	High	High
Paget disease	Normal	Normal	Very high	Hydroxyproline
Myeloma^a	Normal	Normal	Normal	Protein
^aAbnormal serum or urine immunoelectrophoresis.
From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2006.