cuboid stress fractures
Though rare, an isolated cuboid stress fracture should be considered in a patient presenting with lateral foot pain. Overuse injuries are a common entity in medical practice. Stress reactions and fractures make up a significant portion of patients in a typical sports medicine clinic. Due to the repetitive mechanical forces dissipated in the area, the foot is prone to overuse injuries.
Isolated stress fractures of the cuboid are rare, with a review of literature showing less than a 1% incidence. This condition should be a consideration in a patient with continual lateral foot or ankle pain, especially if the patient has persistent lateral foot pain, is athletically inclined, and has a history of repetitive use such as running, triathlon, and jumping activities such as ballet.
General risk factors for stress fractures include running, jumping, marching, decreased bone density, female gender, and poor pre-activity conditioning . Furthermore, a specific triad has been associated with the female athlete involving amenorrhea, low bone mineral density, and dietary restraint. This triad has been shown to increase the risk of stress fractures by 30 to 50% .
The initial stage of bone failure is generally called a stress reaction. This diagnosis is made in a symptomatic patient who has a bone scan or MRI evidence of bone periosteal reactive changes without a true fracture line. Many factors influence the risk of stress fractures, these being divided into intrinsic (gender, age, race), extrinsic (training regimen, footwear, surface, sport), biomechanics (bone geometry), hormonal (menses abnormalities, contraception, thyroid) and nutritional (eating disorders) .
When found and diagnosed, these isolated cuboid stress fractures are most commonly present in endurance sport athletes (marathon, half-marathon, triathlon), but there are also reports in other sports involving large loading forces on the cuboid, including ballet, gymnastics, basketball, and rugby. In a review of 196 cases of stress fractures (125 fractures in males and 71 in females), the most common site was the tibial shaft (44.4%), followed by the foot (15%), metatarsals (9.7%), and the tarsals (1%) . Cuboid stress fractures are less common than fractures in other tarsal bones such as the calcaneus and navicular because the cuboid is not a weight-bearing bone .
The most common presentation for cuboid stress injuries or fractures is insidious onset of pain over weeks to months. Initially, the pain is only with weight-bearing and activity. However, this can progress to pain at rest or with minimal activity.
Activity history is usually affirmative for rapid increases in distance, duration, or training intensity. Other pertinent questions would be changes in running/playing surfaces and the amount of time rested between training events. The sports medicine provider should also investigate menstrual history in females, nutrition (to include calcium and vitamin D intake), medications, footwear, and special equipment used (especially in a sport such as a triathlon).
On physical examination, there is a hallmark localized point tenderness on the lateral foot, especially in the area of the cuboid bone. There may also be mild erythema and subtle soft tissue swelling over the lateral foot area. The “Nutcracker” provocation test in which the examiner stabilizes the calcaneus while the forefoot is abducted, compressing the cuboid between the calcaneus and the base of the fourth and fifth metatarsals with pain being a positive test. If there is significant periosteal reaction or sclerosis in the fracture area, then a palpable mass may be present in the area of maximum tenderness. The placement of a vibrating tuning fork just above the area of maximum tenderness can cause an increase in pain intensity and has been proposed as a diagnostic method for stress fractures .
Imaging with plain radiographs is usually negative at the early stages of a stress fracture, but these studies are needed initially to differentiate other pathologies such as tumors, osteomyelitis, or occult fractures. Conventional radiographs have a sensitivity of 15% to 35% on initial examination, which increases to 30% to 70% over a 2 to 3-week period due to a more pronounced bone periosteal reaction which may be appreciated by the presence of hardly noticeable flake like patches of new bone 2 to 3 weeks after the onset of pain .
Advanced imaging modalities such as computed tomography (CT), MRI, or radionuclide bone scan can be helpful when the diagnosis is questionable or stress fracture is suspected. In the 1970s, a bone scan was primarily used as the imaging modality of choice to diagnose a stress fracture, tracing the uptake of technetium-99m diphosphate characteristic of a stress reaction or fracture .
MRI has now largely replaced bone scans as the imaging modality of choice and is the current “gold standard.” It offers greater specificity and visual resolution over the previously used nuclear bone scan study, which still has indications in some cases such as a patient with surgical hardware or a pacemaker.
There is a role for diagnostic ultrasound as an adjunct to the physical examination. A recent study found the application of point-of-care ultrasound to have a positive predictive value of 99% . However, the amount of training necessary in the deployment and interpretation of diagnostic bedside musculoskeletal ultrasound may limit its universal application across various practices.
An isolated cuboid stress reaction or fracture is typically manageable by primary care providers, sports medicine, or orthopedics. Appropriately managed, these stress fractures are among the quickest to heal, as the cuboid has a generous vascular supply. Treatment generally begins with a general evaluation, ice, and painkillers such as NSAIDs or acetaminophen .
Treatment protocols may vary among providers, but many principles remain similar. The patient may need to start with minimal or non weight bearing with the aid of crutches. Others may use a CAM walking boot initially. Time frame for these is dependent on the patient and provider but weight bearing can be progressed once there is no tenderness to palpation and pain free.
The next few weeks are spent in a gradual return to activity of daily living (ADL), walking plus swimming, walking plus stationary cycling, walking plus the elliptical trainer. A zero-gravity treadmill is also an option for high-level athletes. Once there is progression into this, a graded return to walking and running follows.
Formal physical therapy may include intrinsic foot strengthening, range of motion, and proprioception exercises to offset any deconditioning from the period of non-weight bearing. Some patients quickly make it through the staged rehabilitation, while others may spend 1 to 2 weeks in each stage. At any point in the rehabilitation, if the pain returns, they should step back to a previous pain-free stage for 1 to 2 weeks, then gradually advance to the next stage.
Some adjunctive oral medications are found in the literature, including bisphosphonates, oral contraceptive pills, and vitamin D supplementation. A major prospective, randomized study conducted on 324 young military recruits did not show a decreased incidence of stress fractures with the bisphosphonates group versus placebo . Hormone replacement therapy via oral contraceptive pills to increase bone mineral density is also controversial. A randomized study of 150 young female runners treated with low-dose OCP versus placebo revealed that while stress fracture incidence subjectively trended lower in the OCP group, it was not statistically significant .
Evaluating possible vitamin D deficiency in athletes diagnosed with a stress fracture is common in practice, especially recurrent stress fractures. A recent study of 5201 U.S. Navy female recruits, which evaluated a daily vitamin D (800 international units) combined with calcium (2000 mg) vs. placebo, confirmed decreased stress fracture rates in the vitamin D/calcium group . Though somewhat controversial, routine evaluation of vitamin D levels with treatment of vitamin D deficiency remains a consideration with a stress injury diagnosis.
Bone stimulators have achieved attention in the last few years for treatment of stress fractures. One stimulator uses electromagnetic energy that generates magnetic fields over the fracture site. However, no conclusive data demonstrate that electromagnetic bone stimulators enhance healing. A second type of stimulator uses a pulsed ultrasound device that is theorized to increase vascular endothelial growth factor and fibroblast growth factor, which can promote angiogenesis. However, there is also limited data with this type also. One study with forty three tibial shaft stress fractures showed no significant difference in time to healing by adding a pulsed ultrasound bone stimulator to the usual treatment regimen of rest and activity modification .
Extracorporeal shockwave therapy (ESWT) stimulates osteogenesis and angiogenesis and has been shown to be an effective treatment option for stress fractures in small studies. These were not specific for cuboid fractures and involved five and ten patients.
Athletes should be encouraged to undertake a slow, gradual increase in time, pace, and distance. Cross-training with cycling, swimming, and elliptical is also highly encouraged during the process if they are getting back to running and sprinting. Patients should be counseled on the importance of a proper diet, including caloric intake and appropriate intake of vitamins and minerals, especially calcium and vitamin D. It may also be beneficial to evaluate the athlete’s foot structures, shoes and gait.
With a rich blood supply, cuboid stress fractures are among the quickest stress fractures to heal and generally carry a good prognosis. In a case series involving six tarsal bone stress fractures, a mean expected time to return to athletic participation was found to be 12.1 weeks in division 1 collegiate athletes .
In summary, isolated cuboid stress fractures are uncommon but should be on the differential diagnosis in a patient presenting with lateral foot pain. They most commonly present in endurance athletes and are viewed as more of a “low risk” stress fracture due to its fairly abundant blood supply. They are treated with limited weight bearing for a period until the pain and tenderness improve, then a gradual return to activity and sport.
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