Pathological fracture

Pathological fractures are fractures that occur in abnormal bone and occur spontaneously or following minor trauma that would not otherwise fracture biomechanically normal bone.

Terminology

The term pathological fracture is usually reserved for tumors, either benign or malignant, although it has been used in the setting of osteomyelitis. It can be used in the setting of generalized metabolic bone disease (e.g. Paget disease, osteopetrosis), although the term insufficiency fracture is probably more correct ⁴.  Insufficiency fractures are fractures due to multiple minor events causing a cumulative load on weakened osteoporotic bone. Fragility fractures on the other hand, are acute fractures in osteoporotic patients due to a single event of minimal trauma.

Pathology

Location

The most common location for pathological fractures are ⁴:

• subtrochanteric femur

• humeral head and metaphyseal junction

• vertebral body

In addition, in adult patients, the avulsion of the femoral lesser trochanter should be considered a pathological fracture until proven otherwise ⁴.

Radiographic features

Radiography and CT

• destruction or focal defect within the inner layer of bony cortex

• aggressive periosteal reaction

• lytic lesion

• soft-tissue mass

• mineralized matrix ⁴

MRI

• absent or ill-defined fracture line

• well-defined, homogenous T1-hypointense abnormal signal without normal intervening marrow signal

• adjancent muscle edema ⁴

Scintigraphy

• diffuse uptake of radiopharmaceutical by the lesion ⁴

Treatment and prognosis

Pathological fractures are feared by oncologists because they may cause immobilization of their patients, especially when the spine or lower extremities are affected.

Practical points

A radiologist should mention the possibility of a pathological fracture if an osteolytic metastasis is seen. In principle, every osteolytic focus in the femoral neck or the spine is at risk of a pathological fracture.

Scoring systems have been developed to assess the fracture risk of bone metastases, the Mirels classification is the one that has gained the most traction, although its poor sensitivity (35%) means that it is not without its controversy ⁵.