By Erin Boutwell
A growing body of research on metatarsal stress fractures is helping lower extremity practitioners manage both the biomechanical and physiological effects of these frustrating injuries, as well as the expectations of patients who are eager to return to activity.
Emilie Reas, 30, an avid runner from San Diego, was finishing an 11-mile run when she felt an “achy tension” in the dorsal surface of her right foot, followed by numbness radiating down her second toe.
“The next day … I could not walk without an intense, deep, throbbing pain,” she said.
A series of x-rays indicated a stress fracture of her second metatarsal.
Metatarsal stress fractures often plague athletes like Reas, removing them from competition and relegating them to the bench for weeks and even months at a time. And even researchers who have studied metatarsal stress fractures extensively don’t completely understand them.
“Stress fractures, they’re an interesting animal–especially in the foot–because there’s not a great understanding yet of who gets them or why,” said Robin Queen, PhD, FACSM, director of the Michael W. Krzyzewski Human Performance Lab and assistant professor of orthopaedic surgery at Duke University Medical Center in Durham, NC.
The foot-ankle complex is a highly complicated system, and so many variables are involved in the mechanism of stress fractures that it may be impossible to separate the individual contributions. Nor are all metatarsal bones alike–the first metatarsal is large, strong, mobile, and less frequently injured than the lesser metatarsals. By comparison, the fifth metatarsal is susceptible to bending moments applied from plantar loads, and may be characterized by poor healing and an inadequate blood supply.1
The patient populations affected by metatarsal stress fractures also are somewhat varied. Athletes and military personnel may be at increased risk for stress fractures due to their high levels of physical activity. However, metatarsal stress fractures can occur in anybody, especially when caused by a traumatic event.1
While the type and etiology of metatarsal stress fractures vary, some common risk factors and elements exist. In a 2009 LER article that focused chiefly on fifth metatarsal fractures, Queen and coauthor James Nunley, MD, described these risk factors, including type of activity, gender, foot posture, and shoe/surface characteristics.2
Since then, research by Queen and other researchers has continued to explore the mechanisms underlying metatarsal stress fractures and how to prevent their development. The results of these studies, along with current clinical opinion, highlight some important areas for future consideration.
Any time athletes start demonstrating symptoms of an overuse injury, inappropriate footwear is a potential culprit. Indeed, footwear design has been shown to affect plantar loading patterns, influencing the forces within the metatarsals.2 This is a particularly relevant issue as the popularity of barefoot or minimalist running grows in the US.
A 2015 study concluded that peak pressures under the forefoot were increased when wearing a minimalist shoe compared with a typical running shoe, and hypothesized that this increased forefoot loading may be associated with stress fracture risk.3 These results substantiate an earlier case study in which two minimalist runners developed metatarsal fractures.4 In both publications, the authors suggested that foot strike patterns may need to be altered to address the potential biomechanical risks of barefoot running.
Comparisons have also been made between running shoes and bladed cleats during a jump landing, demonstrating higher forefoot loads in the cleated condition.5 Specifically, cleat placement for athletes who participate in field sports may play an important role in plantar pressure patterns.6 Differences in loading patterns between male and female athletes have also advanced the idea of gender-specific footwear.6
Queen indicated that more cushioning in the shoe itself may be beneficial, but expressed doubt that athletes would use such shoes.
“In soccer… they like to feel that ground; they want that proprioceptive feedback,” she said. “You’re walking a fine line between what the athlete wants from a performance perspective and … what may prevent the injury.”
Orthotic devices are also a commonly used method of managing loads within the foot, but they may need to serve multiple functions, including support and shock absorption. Because a metatarsal stress fracture is damage caused by repetitive impact loading, providing shock absorption with a shoe insert or orthotic device seems an intuitive solution. However, the results of scientific investigations have not demonstrated consistent improvement with orthotic devices.7 Studies of military populations have found no reduction in the incidence of metatarsal stress fractures in participants assigned to a shock-absorbing insole compared with the standard-issue insole in either the Israel military8 or Royal Marine trainees in the UK,9 although a reduced incidence of femoral8 and tibial9 stress fractures associated with the shock-absorbing insoles was reported.
An orthosis also can be used to support the foot structure and limit movement. This type of support may be necessary because of the dynamic nature of the mechanical structure of the foot. Research has demonstrated that peak pressure increased under the metatarsal heads after runners completed a marathon, and this pressure increase was attributed to local muscle fatigue associated with a modified rollover process and increased pronation.10,11 Dieter Rosenbaum, PhD, director of the gait lab at the University of Münster in Germany and coauthor of both fatigue studies, added that an orthotic intervention may be warranted “as a preventive measure to just support the foot … when it gets tired after prolonged loading.”
One type of supportive orthotic device is a rigid carbon fiber shoe insert, designed to restrict movement of the foot structures. This insert has been tested as a possible way to mitigate forces on the metatarsals during cutting movements, but no reduction in loading beneath the metatarsals was found with the rigid insert.12
Harvey Johnson, CO, of Hillsborough, NC, uses custom foot orthoses—and, in some cases, custom fracture braces13,14—to treat metatarsal stress fractures in elite athletes. Over the past 27 years, he has successfully treated stress fractures in more than 300 elite athletes with fracture bracing, and an additional 1000 cases of stress fractures in professional and collegiate athletes with custom foot orthoses, he said.
Johnson builds full-length foot orthoses to treat metatarsal stress fractures using multiple density EVAs (ethylene vinyl acetates) and other materials, fabricating the devices individually in his lab.
“Pain is my ally when fitting and evaluating orthoses. I have to see an immediate and significant improvement in pain during the fitting to know I have built an effective device,” he said.
Clinical consensus on orthotic use
The research results on orthotic devices do not present a compelling case for their use. Nevertheless, orthotic intervention may be warranted in specific cases. Joshua J. Mann, DPM, practitioner at the Ankle & Foot Centers of Georgia in Jonesboro, said he would consider an orthotic intervention when he detects biomechanical problems during a clinical exam or observational gait analysis.
“There can be added stress distally on the metatarsal neck/shaft regions with increased ground reaction force,” Mann said. “These increased forces can be caused by an abnormal metatarsal parabola, cavus foot type, or ankle equinus.”
“Custom orthotics can be expensive for a patient, but I do think they are beneficial for the right patient,” Mann said. “With that being said, you would be amazed at how many patients train in worn-out shoes, and would benefit from just wearing proper footwear.”
An orthotic device can help or hurt, said Selene Parekh, MD, MBA, a partner at the North Carolina Orthopaedic Clinic in Durham, NC and associate professor of orthopaedic surgery at Duke University.
“I have patients who have flat feet but are asymptomatic … they see somebody, they get put into an orthotic that overloads their lateral column, and now they start having stress fractures,” Parekh said.
Queen urged caution in the incorporation of orthotic devices in the treatment of patients with stress fractures.
“It’s very, very difficult to understand exactly what we’ve done when we start to put … the orthotics in,” she said. “We are obviously unloading a given area, but then what’s the long-term implication of using an orthotic and then allowing them to return to sports? Are they really ready or not?”
Johnson maintains that orthotic intervention in patients with metatarsal stress fractures can be effective if done correctly.
“Foot orthotic management requires methodical attention to detail, including biomechanical evaluation of the foot/ankle complex in the unweighted prone position as well as functional weight bearing, and selective use of materials, design, and fabrication techniques,” he said. “Additionally, there are numerous techniques and modifications I incorporate into the foot orthotic that reduces weight bearing on the offending metatarsal head and reduction of torsion to the metatarsal shaft.”
Whether an athlete is starting a new barefoot running program or gearing up for a season of collegiate sports competition, experts agreed that preconditioning is critical to the prevention of metatarsal stress fractures.
“Typically, patients have increased their activity level too quickly, or have added a higher impact exercise [eg, sprint intervals] that their body is not used to,” Mann said of his metatarsal stress fracture patients.
Michael Orendurff, PhD, director of the biomechanics laboratory at Orthocare Innovations in Seattle, WA, explained that the rationale behind a preconditioning program involves the time lag between an increase in bone loading and an increase in new bone formation.
“Wolff’s Law [if there’s more stress, there’s more bone] has a really big time lag, and so six to eight weeks into the [new loading] paradigm, you’re finally starting to lay down new bone. Metatarsal fractures happen a lot about six to eight weeks into the beginning of some new training cycle,” Orendurff said.
Citing a study that found kids who played ball sports had a reduced incidence of stress fractures in their adult lives compared those who did not report playing soccer or basketball in their youth,15 Orendurff also emphasized that childhood ball sports may be an important aspect of conditioning.
“Play-based loading and activity is really incredibly important for kids to have. [They] end up dosing [themselves] with just the right amount of stress,” he said.
In addition to a gradual build-up in physical activity, Parekh suggested that blood testing for vitamin D deficiency may be an appropriate preventive measure. Vitamin D has been associated with promoting bone mineral density, although vitamin D intake has not been conclusively tied to a reduction in stress fracture risk.16
“I think that, in general, all athletes as part of their preseason medical evaluation should probably start getting vitamin D [testing] done. Vitamin D levels are so critical for bone health,” he said.
Better measurement of loads
In discussions with experts on metatarsal stress fractures, a recurring theme was the need for more accessible and more precise data. Queen indicated that imaging techniques, in addition to the current standard of plantar pressure measurements, may be useful to get a better understanding of the loads placed on the metatarsal bones.
Load sensors that athletes or patients can wear to determine the mechanical demands of an activity may also be useful, Orendurff said. Such sensors are commercially available and have been used to evaluate loading in Australian Rules football players17 and other professional athletes.
But Orendurff also noted that low-technology methods—or simple math—can be effective as well.
“You can think about it a little bit: ‘Am I doing twenty percent more acceleration this week than I did last week? I’m at risk.’ If you do that for eight weeks in a row, you’re overloaded,” he said.
Orendurff emphasized the importance of adequately conditioning the bone structure prior to intensive activity.
“Do it better in the preseason,” he said. “We cannot rescue you by giving you an orthotic halfway through.”
Potential physiological factors affecting stress fracture risk span a wide range, including bone density, nutrition, and hormone levels,1 and even within these systems, substantial overlap exists. For example, the aforementioned low vitamin D levels can result from a nutritional deficit but be detrimental to bone quality.
Interestingly, Parekh noted, many patients who present with stress fractures are not necessarily vitamin D deficient, which has been defined as a blood concentration of greater than 20 ng/mL, or even vitamin D insufficient, defined as a blood concentration of 20 to 29 ng/mL.18
“What we’re finding is it really has to be above fifty nanograms per milliliter before you see the pain get better,” Parekh added. “So even though their bloodwork may be ‘normal’ because it’s in the thirties or forties, that’s not good enough. It needs to be fifty and above, anecdotally.”
A global perspective
Clearly, the management of metatarsal stress fractures is multifaceted, with many avenues yet to be explored. Clinicians are responsible for simultaneously managing both biomechanical and physiological effects, as well as handling the expectations of their patients.
Mann stressed the importance of educating patients regarding their injuries.
“Once patients understand the reasons they are developing a stress fracture, we can then work together to overcome the issue,” he said. “Proper training, quality footwear, and orthotics to address their biomechanical issues, and nutrition are all important factors that must be considered.”
Outside the clinic, researchers are also acknowledging the importance of expanding studies beyond a single area of focus.
“There needs to be a merging of worlds … crossing that bridge between what we understand from a biomechanics and a load perspective to what’s actually happening within the body with regards to the physiology of bone remodeling,” Queen said.
Erin Boutwell is a freelance writer based in Chicago.
1. Fetzer GB, Wright RW. Metatarsal shaft fractures and fractures of the proximal fifth metatarsal. Clin Sports Med 2006;25(1):139-150.
2. Queen RM, Nunley JA. Fifth met stress fracture: load-based risk factors. LER 2009;1(3):41-49.
3. Bergstra SA, Kluitenberg B, Dekker R, et al. Running with a minimalist shoe increases plantar pressure in the forefoot region of healthy female runners. J Sci Med Sports 2015;18(4):463-468.
4. Giuliani J, Masini B, Alitz C, Owens BD. Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners. Orthopedics 2011;34(7):e320-e323.
5. DeBiasio JC, Russell ME, Butler RJ, et al. Changes in plantar loading based on shoe type and sex during a jump-landing task. J Athl Train 2013;48(5):601-609.
6. Queen RM, Vap A, Moorman CT, et al. Gender differences in plantar loading during an unanticipated side cut on FieldTurf. Clin J Sport Med 2015 May 8. [Epub ahead of print]
7. Snyder RA, DeAngelis JP, Koester MC, et al. Does shoe insole modification prevent stress fractures? A systematic review. HSS J 2009;5(2):92-98.
8. Milgrom C, Giladi M, Kashtan H, et al. A prospective study of the effect of a shock-absorbing orthotic device on the incidence of stress fractures in military recruits. Foot Ankle 1985;6(2):101-104.
9. House C, Reece A, Roiz de Sa D. Shock-absorbing insoles reduce the incidence of lower limb overuse injuries sustained during Royal Marine training. Mil Med 2013;178(6):683-689.
10. Nagel A, Fernholz F, Kibele C, Rosenbaum D. Long distance running increases plantar pressures beneath the metatarsal heads: a barefoot walking investigation of 200 marathon runners. Gait Posture 2008;27(1):152-155.
11. Weist R, Eils E, Rosenbaum D. The influence of muscle fatigue on electromyogram and plantar pressure patterns as an explanation for the incidence of metatarsal stress fractures. Am J Sports Med 2004;32(8):1893-1898.
12. Queen RM, Abbey AN, Verma R, et al. Plantar loading during cutting while wearing a rigid carbon fiber insert. J Athl Train 2014;49(3):297-303.
13. Groner C. Bracing vs athletic performance: why not both? LER 2009;1(4):18-22.
14. Queen RM, Crowder TT, Johnson H, et al. Treatment of metatarsal stress fractures: case reports. Foot Ankle Int 2007;28(4):506-510.
15. Fredericson M, Ngo J, Cobb K. Effects of ball sports on future risk of stress fracture in runners. Clin J Sport Med 2005;15(3):136-141.
16. Mayer SW, Joyner PW, Almekinders LC, Parekh SG. Stress fractures of the foot and ankle in athletes. Sports Health 2014;6(6):481-491.
17. Loader J, Montgomery P, Williams MD, et al. Classifying training drills based on movement demands in Australian football. Int J Sports Sci Coach 2012;7(1):57-67.
18. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2011;96(7):1911-1930.