A compression fracture is a common fracture of the spine. It implies that the vertebral body has suffered a crush or wedging injury. The vertebral body is the block of bone that makes up the spinal column.
Each vertebral body is separated from the other with a disc. When an external force is applied to the spine, such as from a fall or carrying of a sudden heavy weight, the forces may exceed the ability of the bone within the vertebral body to support the load. This may cause the front part of the vertebral body to crush forming a wedge shape. This is known as a compression fracture. If the entire vertebral body breaks, this is considered a burst fracture and is discussed elsewhere. The compression fracture may range from mild to severe in terms of severity. A mild compression fracture causes minimal pain, minimal deformity and is often treated with time and activity modification.
A severe compression fracture may be such that the spinal cord or nerve roots are involved, as they are draped over the sudden angulations of the spine. This may cause severe pain, a hunched forward deformity (kyphosis) and rarely neurologic deficit from spinal cord compression.
Risks - Osteoporosis - Trauma
The risk for spinal compression fracture increases with age. Osteoporosis is the most common risk facture for compression fractures. Osteoporosis is a condition in which there is thinning of the bones, weakening them. This may be due to a lack of calcium in the diet, certain medications, old age, inactivity or genetic factors.
In general, some trauma occurs with each compression fracture. In cases of severe osteoporosis, the trauma may be minimal, such as, stepping out of a bathtub or lifting a heavy object. Moderate trauma is usually required to create a fracture in patients with mild to moderated osteoporosis. This may range from falling off a chair to an automobile accident. A normal spine may also suffer from a compression fracture when there is a severe forward bending injury. This most commonly occurs from a fall from a height or an automobile accident.
Neurologic injury is rare with compression fractures. The degree of neurologic injury is usually due to the amount of force present at the time of injury. If there is severe angulations of the spine secondary to a wedge fracture, this may stretch the spinal cord and create injury. This would then lead to loss of strength and sensation, as well as reflexes. In most patients with osteoporotic compression fractures, there is no neurologic injury but only pain from the fracture. However, if left untreated the fracture angulations may worsen and lead to late paralogic injury.
A compression fracture is usually diagnosed by the history, physical exam and x-rays. In any patient over the age of 60 with the acute onset of sudden low back pain, a compression fracture should be suspected. Physical exam will usually note tenderness directly over the area of pain as well as mild kyphotic deformity (e.g., a sudden angulations forward or hunched over appearance). Plain x-rays will demonstrate the wedge shape of the vertebral body on a lateral view. A CAT scan is occasionally needed to help differentiate a compression fracture from a burst fracture.
Occasionally an MRI scan is obtained to rule out disc herniation along with a compression fracture. MRI scan may also help differentiate pathologic compression fractures, that is, those that involve a tumour, from a typical osteoporotic compression fracture. In any patient with a known history of cancer, a compression fracture should tip off the physician to look for evidence of a metastatic lesion and pathologic fracture.
If osteoporosis is suspected, a Bone Mineral Density (BMD) test may be ordered. This test helps determine the severity of the bone thinning. In addition, laboratory tests to look at blood count and thyroid function may be indicated as well. A decision as to whether to treat osteoporosis should be made by the patients' primary physician.