Stress Fracture of the Spine

A stress fracture is an incomplete fracture of a bone. It generally caused by a chronic repeated loading. This type of fracture is typically seen in lower extremity, spine, or pelvis. Briethaupt, a Prussian military physician, first reported this kind of fracture (Breithaupt, 1855). He presented the first description of a metatarsal stress fracture when he noted swelling and pain in the feet of military recruits. Thus, these injuries were called "march fractures" because of they commonly were seen in military recruits suddenly subject to long forced marches (Stechow, 1897). In 1897, just a few years after William Roentgen created the first x-ray machine, radiographic examination of these injuries became possible. 

A stress fracture of the spine generally occur in two locations: posterior elements of lumbar vertebrae (pars interarticularis), and vertebral body. Stress fracture of the pars interarticularis is called spondylolysis. Stress fracture of the vertebral body typically occurs in osteoporosis, and is called as fragility fracture or osteoporotic compression fracture.

Pathogenesis
Microfractures have been thought to be the physical precursor to stress related injury of bone but the reality is quite subtle. Mechanical forces activate the cell signaling mechanisms. Integrins, membrane proteins, thought to be a part of the cell sensing system, appear to play a role in the activation. Aberrant forces alter the subtle balance between osteoclastic and osteoblastic activity through altered gene activity. This mechanotransduction of force into biological mechanism is the true precursor to the stress related injury of bone. Cell signaling alters the gene activation pattern which then changes the metabolic activity of the cells. The altered metabolic activity causes aberrant remodeling which is a component of the initial stress “reaction” and not a true fracture.

Presentation
A stress fractures may present subtle symptoms. It causes pain and tenderness associated with weight bearing. Stress fracture of the spine gets worse with sitting and standing, gets better with lying.

Diagnosis
Injury may first be seen on a bone scan (scintigraphy) reflecting metabolic activity of bone. Slightly later the injury will be visible on an MRI. Finally the injury may become visible on an x-ray.

Treatment
Rest induces healing of a stress fracture. The amount of recovery time varies greatly depending upon the location, severity, the strength of the body's healing response and an individual's nutritional intake. While the bone may feel healed and not hurt during daily activity, the process of bone remodeling may take place for many months after the injury feels healed. Thus, incidences of re-fracturing the bone is still at significant risk. Rehabilitation usually includes muscle strength training to help dissipate the forces transmitted to the bones. With severe stress fractures, surgery may be needed for proper healing. Spine fractures may be treated with vertebroplasty or kyphoplasty procedures.