Stress fracture of the 2nd metatarsal bone.
First described by Aristotle in 200 BC, stress fractures were initially recorded in the medical literature in 1855 by the Prussian military physician Breithaupt, who described what is now known as a \"march fracture\" (stress fracture of the metatarsals). Metatarsal stress fracture is not limited to high-level athletes or military recruits. This type of injury is seen in runners of all levels, ballet dancers, gymnasts, patients with rheumatoid arthritis (RA), those with metabolic bone disease, and neuropathic conditions. Metatarsal stress fracture also is seen with increasing frequency in patients who engage in aerobics, particularly high-impact aerobics.
The incidence of stress fracture in the general population is unknown, as virtually all literature on the subject is derived from a military population or advanced-level athletes. Stress fractures are estimated to comprise up to 16% of all injuries that are related to athletic participation; running is the cause in most of these. Most stress fractures (95%) involve the lower extremities; the metatarsals are most commonly involved.
Functional Anatomy
The second and third metatarsals are relatively fixed in position within the foot; the first, fourth, and fifth are relatively mobile. More stress is placed on the second and third metatarsals when ambulating, so these are at increased risk for stress fracture.The fifth metatarsal, which is approximately 1.5 cm from the proximal pole of the bone, bears greater stress in those who oversupinate when they walk or run. The fifth metatarsal also has a diminished blood supply and thus, decreased ability to heal.
Stress fractures of the proximal fifth metatarsal need to be distinguished from proximal avulsion fractures (\"pseudo-Jones\" fractures) and Jones fractures. The proximal avulsion fracture is usually associated with a lateral ankle strain and occurs at the insertion of the peroneus brevis tendon. The true Jones fracture is an acute fracture of the proximal diametaphyseal junction.
History
- Patients usually report increased intensity or duration of exercise regimen.
- Dull pain occurs initially only with exercise, progressing to pain at rest.
- Pain starts as diffuse, then localizes to the site of the fracture.
- Stress fractures can be historically distinguished from a true Jones fracture, because patients with a stress mechanism report a long history of prodromal symptoms of pain over the proximal fifth metatarsal.
- Menstrual irregularities should be explored in female patients, due to a high association between female athletics, amenorrhea, and osteoporosis (the \"female athletic triad\").
Causes
- Increased intensity, duration, or frequency of exercise
- New footwear
- Insufficient rest periods
- Continuing to train despite pain
- Osteopenia/osteoporosis
- Rheumatoid arthritis
- Neuropathic foot
- Female athletic triad
Imaging Studies
- Plain-film radiography
- Radiographs may be negative early in the process.
- Changes of stress fracture may not be evident on plain films until 3 months after symptom onset.
- Fifty percent of stress fractures are never observed on plain films.
- Plain film radiography can help the physician distinguish fifth metatarsal stress fracture from a true Jones fracture. Fractures with a stress etiology show a widened fracture line, intramedullary sclerosis, and periosteal reaction.
- Bone scan
- Technetium Tc 99 diphosphonate 3-phase bone scan has traditionally been the imaging modality of choice.
- This study is nearly 100% sensitive for the diagnosis of stress fracture, although specificity is considerably lower.
- Bone scan can demonstrate stress fracture within 24-72 hours from symptom onset. Differentiation between stress fracture and stress reaction may be determined with a bone scan.
- MRI and single-photon emission computed tomography: These imaging tests also may be used to image stress fractures, and MRI is now becoming the study of choice because it has the same sensitivity as a bone scan, but the specificity is much higher. Additionally, it does not require ionizing radiation.