March fractures (metatarsal stress fractures) were first described in 1855, termed after the foot pain and swelling experienced by Prussian soldiers on long marches. March fractures are metatarsal fractures, caused by repetitive stress. Intrinsic patient and extrinsic environmental risk factors can both contribute to the development of these fractures. A combination of historical features and physical evaluation with imaging can help make the diagnosis. These stress fractures are typically managed conservatively but can be complicated by nonunion. In such instances, surgical fixation may be warranted.
March fractures are metatarsal fractures, most commonly second and third metatarsal fractures caused by an overuse injury. The repetitive impact to the metatarsals with weight-bearing exercises cause microfractures, which consolidate to stress fractures.
The most common location of metatarsal stress fractures is the second metatarsal neck as it is less flexible and prone to torsional forces given its strong ligamentous attachment to the 1 and 2 cuneiforms. In addition, the second metatarsal is the longest of the metatarsals, subjected to the most force.
March fractures occur commonly with sports and sudden increases in physical activity over 6 to 8 weeks. Metatarsal stress fractures are common in college athletes and the military, accounting for 25% of all stress fractures. Overall data suggest that females have a higher incidence of march fractures than men. In addition, those with prior stress fractures are more likely to develop another. Sixty percent of patients with a stress fracture will have had a previous one.
Common in new military recruits, a pervading theory is that osteoblastic activity lags behind osteoclastic activity during initial increases of exercise stress, leading to an increased incidence of stress fractures. March fractures occur secondary to bone fatigue or bone insufficiency. Bone fatigue occurs when normal bone is unable to resist excessive mechanical demands. Bone insufficiency occurs when normal strain occurs on abnormal bone. Intrinsic risk factors as nutritional deficiencies as vitamin D or calcium increase the risk of these fractures. In addition, extrinsic risk factors as the training type or shoe type can also contribute to an increased risk of metatarsal stress fractures.
Kaeding and Miller’s 5-Tier Grading System
Grade of Stress Fracture/Radiographic Finding
During an interview, patients indicate that there is an inciting activity or exercise subjecting the patient to repetitive stress. Activity-related, insidious onset of pain at the site of fracture is often elicited from the history. Pain may improve transiently with rest but increases again with activity. Pain often is described as dull and aching. It is important to obtain a thorough medical history with particular attention to potential intrinsic risk factors. This may include an interview on a patient’s diet, endocrine disorders, and menstrual history in female patients.
Physical examination consists of palpation of the pain site, eliciting boney tenderness. If the fracture is in the proximity of a joint, the joint motion will aggravate the pain. Patients may have a limping gait with weight bearing.
March fractures are diagnosed based on historical clues, physical examination, and confirmed with diagnostic imaging. Plain radiographs are the initial imaging modality of choice. However, plain radiographs have a high rate of false negative for metatarsal stress fractures early on and may not demonstrate fractures until 2 to 4 weeks after the onset of pain. While a clear fracture through the metatarsal may be seen on a radiograph, subtle periosteal reactions and blurring of the cortex may be the only clues of a stress fracture. More mature fractures may demonstrate callus formation or cortical lucency.
Occult, suspected fractures not visible on plain radiographs can be imaged using 3three-phase bone scans with technetium-99 or magnetic resonance imaging (MRI). Both advanced imaging modalities have been proven to be sensitive to these fractures up to 24 hours after onset of pain. While bone scans are considered sensitive, but not specific, MRI is both sensitive and specific for metatarsal stress fractures.
Lastly, thorough testing of the patient’s intrinsic risk factors may be needed. For example, measuring serum 25(OH), vitamin D concentration can be considered in those suspected of nutritional deficiencies.
In most cases, analgesia and rest are all that is needed for metatarsal stress fracture healing. Acetaminophen and ice are implemented for pain and swelling. The effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on fracture healing remains contested.
Immobilization is often unnecessary, and a stiff-soled orthopedic boot or walking boot may be used for 4 to 8 weeks. Weight-bearing is allowed as long as the patient is pain-free. Thus, exercise may resume with lower impact exercises as swimming, cycling, or deep water running. The exception to this treatment is areas higher risk for nonunion, consisting of the base of the fifth metatarsal and neck of the second metatarsal. Special consideration should be given to pain elicited at these areas for advanced imaging if radiographs are negative. In addition, if a fracture at these sites is present, non-weight bearing status can be achieved with crutches and casting. Additionally, a referral to an orthopedic surgeon should be placed in cases of nonunion that may need surgical fixation.
Modifiable risk factors should be treated. Nutritional deficiencies as low levels of vitamin D, calcium, or calories should be addressed by ensuring adequate intake and supplementation as needed. Environmental changes should be considered. Shock-absorbing insoles for shoes or boots can distribute force during weight-bearing exercises. The type of training activity, surface, and intensity can be adjusted.
As a march fracture heals, a graded return to activity should be employed. When the patient is fully weight-bearing and pain-free with low-intensity exercise, the patient gradually increases their exercise intensity by 10% every week to avoid further stress fractures.
Prevention of march fractures includes stretching with gradual increments in exercise intensity and duration to avoid abrupt changes in stress. In addition, correcting predisposing biomechanical conditions as gait training and arch supports can be beneficial.
Nonunion is a complication of march fractures with symptoms of chronic pain, swelling, or instability. In such cases, surgery with intramedullary nailing may be warranted. Post-operatively, healing can be arduous, sometimes taking months to years.