Stress Fractures of the Foot and Ankle

Incidence

Stress fractures typically affect runners, military enlistees, tennis and basketball players, and anyone involved in repetitive lower-extremity activity or an exhaustive training regimen. The two most studied cohort types are military recruits and collegiate running athletes. It is important to understand the differences in these groups. While they are similar in age, the subjects in studies of military enlistees are almost all men who are enduring an acute increase in musculoskeletal strain during training. Studies of running athletes, on the other hand, are more gender balanced and have a high incidence of RED syndrome among enrolled subjects.

Military enlistees are uniquely at risk for stress injuries and fractures because of heterogeneous baseline fitness levels, variable, often intense training regimens, and a rapid acceleration of training. In a prospective study, Milgrom et al reported an alarmingly high rate (20%) of symptomatic stress fractures among elite Israeli army recruits during a year-long training program, 51% of which were located in the tibial diaphysis, a distribution that more closely mirrors running athletes. Ninety-three percent of tibial stress fractures in the cohort occurred during the first half (6 months) of training. Metatarsal fractures were the dominant fracture type (91%) during the second half of the year. Reported incidence rates of stress fractures in other series are exponentially lower, approximately 1% to 2%, with a lower incidence of tibial stress injuries. Pester and Smith reported on 1338 stress fractures among 1050 injured US military enlistees during basic training over a 4-year period at Fort Dix. Relative incidence by fracture location was: 53% metatarsal, 27% calcaneus, and 14% tibia. Third metatarsal (27%) stress injuries were more common than second (17%) and first (5%). Female recruits were 20% more likely to sustain a stress injury, were specifically more likely to injure the tibia or calcaneus, and were twice as likely to develop bilateral stress injuries.

The distribution and risk factors for stress fractures are different among runners. As introduced previously, approximately 50% of stress fractures among American collegiate and recreational adult runners are in the tibial disphysis. Stress fractures of the tibial diaphysis disproportionately occur in younger runners. Bony stress injuries more frequently occur in middle and long distance runners and are often associated with oligo- or amennorhea. Uniquely, 50% of collegiate runners who develop a bone stress injury have more than one, often (65% of the time) concurrently. Higher MRI grade injuries correlate with lower dual-energy x-ray absorptiometry (DEXA) hip and radius BMD scores and oligo/amenorrhea. Vitamin D levels are known to be relatively deficient among subjects who sustain fifth metatarsal stress fractures.

Clinical Presentation

Stress injuries, both stress reactions and fractures, often present with insidious onset of deep, aching pain during and/or after activity that improves with rest. Sixty-six percent of patients will have tenderness to palpation over the affected bone (80% for fibula and tarsal injuries), but only 25% will have obvious swelling, though swelling may be present in over 50% of metatarsal injuries. Endurance and high-level competitive athletes often endure and push through their symptoms. Adolescent and collegiate athletes often present in a delayed fashion due to pressure to perform from family, coaches, and internal pressure and anxiety within athletes, themselves. Continued loading beyond the reparative potential of the bone may lead to progression to a visible radiographic cortical lucency or even fracture displacement. The differential diagnosis at this stage includes tendinitis, periostitis, pes bursitis, exertional compartment syndrome, and gastrocnemius–soleus complex injury.

Imaging

Imaging studies are used to confirm stress-related injuries, assess their location, and evaluate their severity. Plain radiographs are specific if frank cortical disruption is present, but lack sensitivity in the acute setting, as bony mineralization is a subacute/chronic finding. Plain radiographs reveal evidence of stress fracture in only 10% of injuries. Plain radiographs are more likely to be helpful during treatment and follow-up once fractures are diagnosed and may reveal demineralization (rarefaction), sclerosis, periosteal reaction, and endosteal thickening. Technetium-122 ( ⁹⁹ Tc) bone scans are sensitive but have essentially been replaced by MRI, which does not require intravenous contrast dye, does not expose the patient to radiation, and generates an anatomically brilliant and specific image. Additionally, the false positive rate is lower with MRI than bone scan. Computed tomography (CT) is helpful only to characterize fracture morphology but is not sensitive enough to be utilized as a screening tool.

Imaging features vary based on the bone involved. Broadly, fractures can be categorized as cortical (e.g., tibial and metatarsal shaft) and cancellous. Cortical fractures will, typically, first become visible on MRI as periosteal reaction on T2 and STIR sequences. Increased T2 and STIR signal within the bone marrow will then develop as stress injuries progress. Increased T2 and STIR signal are the first to develop in cancellous bone (e.g., calcaneus) injuries.

Treatment

Treatment begins with prevention. Changes in shoewear and modifications to training regimens have led to reductions in stress injuries among military recruits. Identifying and managing the sources of relative energy deficiency and menstrual dysfunction in RED syndrome, including psychological and nutritional, is paramount to risk reduction among runners, gymnasts, and other high-risk groups.

Once they occur, the treatment of stress reactions begins with immobilization, typically in a fracture boot or well-cushioned, hard-soled postoperative shoe, and a holiday from high-impact inciting exercise (e.g., running) for a period of 4 to 8 weeks. Most stress fractures heal in 1 to 3 months, allowing return to a prior level of activity/sport within 3 to 4 months. Once the fracture has healed, shoe modifications with biomechanical correction are necessary, as is the avoidance of a premature return to activity. Aerobic conditioning exercise may continue in lower impact forms (e.g., swimming or cycling). The athlete can return to sports when pain free. Depending on the patient and injury location, well-cushioned custom orthotics with stiff soles and shoewear modifications can be made to reduce load, particularly through the forefoot and midfoot. The proliferation of commercially available rocker bottom running shoes, which reduce pressure parameters in the central and lateral forefoot, has the potential to help reduce the incidence of midfoot and forefoot stress injuries in runners.

Most stress fractures (visible fracture line on plain radiographs, CT scan, or MRI) can also be successfully treated nonoperatively. Initially, a fracture boot or short leg cast can be applied for protected weight bearing. The patient should be treated holistically, considering age, exercise goals (younger athlete vs. older nonathlete), diet, training regimen, and coexisting conditions. If relative energy deficiency is suspected to play a role in a young female patient’s pathophysiology, communication with the patient’s primary care physician and appropriate referral to a dietician, psychiatrist, primary care sports medicine physician, and/or endocrinologist may be prudent. Laboratory evaluation to evaluate potential causes of amenorrhea and DEXA scans should be considered, especially in high-risk or repetitive cases.

Potential pharmacologic strategies include calcium and vitamin D supplementation and teriparatide. Daily calcium and vitamin D maintenance dosing recommendations are shown in Box 38-1 . Calcium and vitamin D supplementation during Army initial military training (US) has been demonstrated in a randomized, double-blinded, placebo-controlled trial to increase the circulating level of ionized calcium and osteoprotegrin:RANKL ratio and improve volumetric BMD, cortical bone mineral content, and thickness compared to placebo. While bisphosphonates have been demonstrated to reduce the risk of fragility fractures among postmenopausal women, they inhibit fracture healing once fractures occur. Acute teriparatide administration (daily for 2 weeks post-fracture) has been shown to accelerate stress fracture healing in bisphosphonate-associated fractures. However, clinically meaningful improvements in union rate and stress fracture recovery time have not been demonstrated in young, athletic populations.

While nonsteroidal antiinflammatory drugs (NSAIDs) lower perioperative pain scores and opioid prescription use following fracture surgery, selective cyclooxygenase-2 (COX-2) inhibitors, specifically, were implicated in the insurance claims database study published in 2020 by George et al to contribute to nonunion risk after fracture care. In both studies, when lower quality studies are excluded, there is no demonstrable association between NSAID use and nonunion. Nonselective NSAIDs, including ketorolac and ibuprofen, have been demonstrated to be safe for use in postfracture care. Further research needs to be done to further delineate the risks of NSAID use in acute fractures as well as during healing of stress fractures.

Bone stimulation with noninvasive low-intensity pulsed ultrasound (LIPUS; extracorporeal shockwave therapy) has shown some promise in accelerating fracture healing but has no proven benefit in stress fractures. LIPUS has both a short-term (2–4 days) and long-term (18 days) stimulatory effect on human periosteal cells, increasing short-term alkaline phosphatase activity, calcitonin secretion, vascular endothelial growth factor secretion, and calcium nodule formation in a dose-dependent manner and increasing viable cell number and calcium deposition 18 days following stimulation. Clinically, Heckman et al first published evidence clinical efficacy of the device in an industry-funded randomized, double-blinded clinic study of 67 tibial shaft fractures across 17 total sites (16 in the United States, 1 in Israel) in 1994. LIPUS was used as an adjunct to closed reduction and casting, accelerating clinical fracture healing by 1 month (86 +/- 8 days vs. 114 +/- 10 days) and complete cortical healing by over 2 months (114 +/- 8 vs. 182 +/- 16 days). By chance of randomization, however, a significantly higher proportion of placebo group patients sustained an ipsilateral fibular shaft fracture, theoretically increasing the risk of delayed and/or nonunion. In another more recent multicenter, randomized, sham-controlled trial of LIPUS use in tibial shaft delayed unions in Germany, BMD increase and bone gap area reduction were improved relative to controls. However, no meaningful clinical difference was demonstrated. Multiple authors in these two well-designed studies were paid consultants of the sponsoring company. Two series specifically studying lower extremity stress fractures failed to demonstrate a clinical benefit to LIPUS. The authors conclude that the use of LIPUS is reasonable to consider in cases of delayed fracture union.

Clinical Features

The primary clinical symptom of tibial stress fracture is pain with activity, particularly near the end of activity. Symptoms typically begin as mild discomfort that abates with rest. This typically escalates with continued training, with pain beginning earlier during a training activity and persisting for a longer duration after activity. It is rare to have acute-onset pain that does not resolve with short periods of rest. The pain and discomfort can progress to the point that the patient cannot participate in the activity and training has to be discontinued.

Physical examination typically reveals tenderness over a localized third of the tibia, usually along the midshaft. In a recent study published by Milgrom et al, 106 Israeli infantry recruits with medial tibial pain were assessed on physical examination. While medial tibial pain and tenderness are both sensitive, neither are specific for a tibial stress fracture. The single-leg hop test was found to be the best singular physical examination test for stress fracture, with the following indices, using a positive bone scan as the diagnostic gold standard: 100% sensitivity, 45% specificity, 74% positive predictive value, 100% negative predictive value. No enlistee with tenderness to palpation of greater than one third the length of the tibia was diagnosed with a stress fracture.

Diagnosis

Radiographs are typically normal in the early stages of stress injury and fracture but may demonstrate some periosteal reaction or cortical thickening as early as 2 to 3 weeks from the time of the earliest symptoms. The early stages can show a mild cortical lucency, typically along the posteromedial tibial cortex, which later becomes an area of increased density accompanied by a more noticeable periosteal reaction with cortical thickening. An anterior cortical line, which is often a subtle finding in high-grade tibial stress fractures, can be a harbinger for a more difficult clinical course. Complete stress fractures through the anterior tibial cortex, a less common variant more frequently seen in basketball players, can be resistant to conservative treatment and prone to pseudoarthrosis ( Fig. 38-1 ).

MRI is the current gold standard for the diagnosis of tibial stress reactions and fractures, largely replacing ⁹⁹ Tc bone scans as previously discussed. Both are very useful in detecting stress fractures in the early or evolving stages ( Fig. 38-2 ). A grading system first described by Fredericson et al and later validated and modified by Kijowski et al categorizes severity of injury along a progression of imaging characteristics ( Table 38-1 ). Grade 1 injuries are characterized by medial (91%) tibial periosteal reaction only, clinically manifesting as medial tibial stress syndrome or “shin splints.” Grade 2 injuries are defined by the appearance of bone marrow edema on T2 and STIR, but not T1, images. T1 signal changes in the bone marrow, which are the hallmark of Grade 3 injuries, are thought to correlate with a more robust inflammatory response to repetitive stress. Grades 4a and 4b are distinguished from Grades 2 and 3 by the presence of intra-cortical signal changes. Grade 4b injuries, defined by the presence of linear areas of intracortical signal abnormality, have significantly more severe periosteal edema (greater MRI thickness) and bone marrow edema (wider and longer) than all other grades. This translates, clinically, to a longer median return to sport time than other groups (see Table 38-1 ). The vast majority of diaphyseal tibial stress fractures, even Grade 4b, are localized to the posteromedial tibia and resolve with conservative measures.

Treatment

Treatment is largely nonoperative for tibial stress fractures, unless injuries reach Grade 4 or are anterior, and return to sports is usually possible within 3 to 9 weeks, depending on the severity of injury. Training characteristics, shoewear, running form, and patient-specific components of RED syndrome should all be examined for potential intervention, contributing to a holistic return to sport plan. Initial treatment consists primarily of rest and avoidance of the instigating activity, whether that be running, marching, jumping, or sport (e.g., basketball). Strict non–weight bearing is usually unnecessary, but immobilization with a tall fracture boot can decrease load borne by the tibia and improve patient compliance in training abstinence. Exercise may continue with upper body and core strengthening, as well as low-impact cardiovascular exercise, including swimming, biking, and even on an elliptical trainer. Resumption of activity is based upon the presence or absence of symptoms. Training is gradually resumed and accelerated based on the absence of symptoms as well as the lack of clinical examination findings, such as swelling and tenderness.

Excessive tibial loading, as measured by vertical peak impact, vertical loading rate, and tibial shock, has been uniquely linked to correctable errors in running form that predispose runners to injury. Gait retraining, if executed with a proven protocol, has been shown to reduce tibial loads during running in a durable manner. When retraining is coupled with appropriate running shoes to reduce impact loading and orthotics to correct dynamic pronation and/or supination at heel strike, tibial strain can be greatly reduced, lowering the risk of reinjury.

In the case of anterior tibial shaft stress fracture, delayed union is common and conservative treatment often fails to produce complete symptom relief, let alone return to a prior level of sport. It is reasonable to consider surgical intervention, especially if fracture healing fails to progress with 4 to 6 months of conservative treatment. Surgical drilling of the anterior tibial cortex has not been as successful as the results of osteosynthesis with either compression plating or intramedullary nailing. If union is achieved, return to an equivalent preinjury level of sport has been reported in 95% of patients. The authors prefer reamed suprapatellar tibial nailing, as reamed nailing both preserves and stimulates periosteal blood supply and suprapatellar nailing is associated with a lower incidence of clinically impactful anterior knee pain than nailing via an infrapatellar approach. LIPUS bone stimulation can be considered in refractory cases of delayed union after surgical intervention.

Clinical Features

Athletes, typically runners, jumpers, or soccer players, with a medial malleolar stress injury typically present with insidious onset of activity-related pain over the medial malleolus and mild associated swelling, with or without an ankle effusion. The differential diagnosis includes anteromedial ankle impingement, deltoid ligament injury, osteochondral lesion, and posterior tibialis tendonitis. The presence of anteromedial talar neck osteophytes should raise suspicion for an impingement-associated stress injury. It is theorized that the combination of dorsiflexion and rotation can cause excessive or repetitive force transmission to the medial malleolus at the level of the medial tibiotalar shoulder, leading to micro-trabecular injury. Ankle range of motion is not limited, and a history of instability or inversion/eversion injury is not typical, although lateral ankle ligament instability may accompany medial malleolus stress fractures associated with varus hindfoot alignment.

Radiographs

Other than anteromedial tibiotalar osteophyte formation, plain radiographs are usually normal as late as 2 months after the initial appearance of symptoms. If a medial malleolar stress reaction or fracture is suspected, MRI is the axial imaging modality of choice, as it allows for screening for other pathologies in the differential diagnosis (e.g., osteochondral lesion, posterior tibialis tendonitis, deltoid ligament injury, etc.) and can be utilized to assess severity of injury. Further evaluation of stress injuries with a weight-bearing CT scan is helpful to evaluate anteromedial tibiotalar bony impingement and the location, orientation, and characteristics of the injury further for preoperative planning purposes. Axial T2-weighted MR images will demonstrate edema (increased signal) within the medial distal tibia and periosteal reaction as well as a linear area of decreased signal oriented parallel to the medial shoulder of the distal tibia in cases of true fracture ( Fig. 38-3A ). Corresponding sclerosis and reactionary bone formation adjacent to the fracture will be evident on CT scan ( Fig. 38-3B ).

Treatment

The treatment of the medial malleolar stress fracture is patient and fracture dependent. The patient’s activity level, alignment, chronicity of symptoms, fracture severity, associated other problems, and timing of the athletic season all factor into the choice of treatment. For stress injuries without frank fracture on axial imaging, a trial of conservative treatment is reasonable.

In the early stages of symptoms, immobilization in a tall fracture boot, which limits ankle dorsiflexion beyond neutral, for 4 to 6 weeks and high-impact activity restriction are recommended. Restriction of weight bearing is typically not necessary. If the patient has varus alignment at the ankle level, whether intrinsic to the ankle or from knee, tibia, or hindfoot/midfoot varus, the use of a lateral heel wedge and/or custom orthotic may unload the medial ankle compartment and prevent further or reinjury. Symptom resolution can take 5 to 9 months with conservative treatment, and symptoms often recur with resumption of preinjury activity level.

In chronic or recurrent cases, or if the fracture line is discretely visible on CT scan, surgical treatment is typically necessary. Since these fractures are intraarticular, the long-term health of the joint must be considered. If there is any displacement of a complete fracture on presentation, the authors recommend surgical fixation with concomitant debridement (arthroscopic or open) of anteromedial tibiotalar osteophytes for joint preservation and to expedite recovery. Historically, drilling of the stress fracture with/without bone grafting was the mainstay of treatment. More recently, satisfactory clinical results with durable return to sport by 3 to 4 months and no nonunions (21 total cases) after arthroscopic debridement with rigid fixation have been reported. Buttress (antiglide) plating should be considered for fracture fixation in cases with a vertical fracture morphology ( Fig. 38-4 ). Percutaneous screws fixation is an option in cases of no fracture displacement or an incomplete fracture. It is critical to assess the anteromedial joint line for areas of bony impingement. If present, debridement of both talar and tibial osteophytes is necessary ( Fig. 38-5 ). In cases with an established nonunion, the authors recommend take-down of the pseudarthrosis and bone grafting as an adjunct to open reduction and buttress plate fixation.

Clinical Presentation

Fibular stress fractures typically occur in in the distal third of the fibula, usually (73%) 4 to 7 cm proximal to the tip of the fibula at the level of the syndesmosis. An association between hindfoot valgus and distal third fracture location has been described. The second most common location is 7 to 15 cm proximal to the fibular tip (15% of fractures). The vast majority of injuries occur in running athletes while in training, with a preponderance for the winter months. Most patients report insidious symptom onset without obvious trauma, yet a minority (39%) can recall the training episode during which they first become symptomatic.

As with other stress fractures, the clinical presentation is typically characterized by insidious onset of pain, usually within 10 days of the increased activity or alteration of training, with associated ankle swelling and associated fibular tenderness to palpation. The patient’s pain is often generalized and difficult to locate. Tenderness, when present, is usually located at the posterolateral border of the fibula approximately 4 to 7 cm from the tip of the malleolus, corresponding to the most common fracture location. If the presentation is subacute, a common clinical finding is palpable prominence at the fracture site from the abundant callus. Ankle range of motion is usually well preserved.

Radiographic Findings

Radiographs demonstrate the fracture within 3 or 4 weeks of the initiation of symptoms. The characteristic radiographic findings include a relatively transverse fracture, low incidence of fracture displacement, and abundant callus ( Fig. 38-6 ). Significant cortical thickening is seen both distal and proximal to the fracture site, and a less dense line is seen at the location of the initial fracture. These findings are often apparent at 12 to 16 weeks. Additional diagnostic studies, such as MRI, are rarely needed ( Fig. 38-7 ).

Etiology

There are many theories concerning the cause of these fractures. In patients, especially young runners, with physiologic hindfoot valgus, load transfer through the more compressive lateral half of the ankle joint during high-impact loading likely generates a relative force of valgus on the fibula. If patients have planovalgus alignment of their foot or run with dynamic pronation, this likely exacerbates this load transfer through the fibula, as planovalgus causes significant lateral translation of global contact area and peak pressure location in the tibiotalar joint. In severe cases of valgus hindfoot alignment, with subfibular impingement, stress injuries to the distal fibula may occur without high-impact loading.

Treatment

Stress fractures of the distal fibula are uniformly treated conservatively until there is fracture displacement or incongruency of the ankle mortise often associated with chronic deltoid ligament insufficiency. Rest and physical activity restriction is the hallmark of treatment. A tall fracture boot or pneumatic ankle brace may be used for 3 to 4 weeks to improve patient comfort and reduce coronal plane stresses on the fibula. Immobilization does not likely alter the natural history of the fracture, as Devas and Sweetnam reported uniform symptom resolution in their 50-patient case series with elastic strapping of the ankle and avoidance of high impact training. The authors recommend avoidance of inciting activities until the distal fibula is no longer tender to palpation. Activity resumption is usually possible within 6 to 8 weeks.

Anatomy and Physiology

Other than for congenital variations, there are two hallux sesamoids. The tibial (medial) hallux sesamoid is larger, longer, and often more distally positioned. The fibular (lateral) sesamoid is typically smaller, rounder, and more proximal in its relation to the tibial sesamoid. As a result of these differences, the tibial sesamoid endures greater weight-bearing forces and is therefore the one more often injured. The sesamoids are embedded within the extensor hallucis brevis tendon complex and are connected to each other by the intermetatarsal ligament. The abductor hallucis brevis inserts into the tibial sesamoid and the adductor hallucis brevis inserts into the fibular sesamoid. The blood supply to the tibial hallux sesamoid is via terminal branches of the medial plantar artery. Ossification occurs at between 9 and 11 years of age, often in multiple areas of the sesamoid. Congenital partition of the tibial sesamoid is fairly common, reportedly ranging from 10% to 33%, ten times greater than that in the fibular sesamoid. Partition, when present, is often bilateral.

The sesamoids function to dissipate forces within the hallux metatarsophalangeal (MTP) joint, elevate the metatarsal head (thereby increasing the mechanical advantage of the flexor hallucis brevis [FHB] tendon), and protect the flexor hallucis longus (FHL) tendon while maintaining its direction of pull. Excision of the tibial sesamoid leads to a 10% loss of hallux push-off power. Excision of both sesamoids leads to further loss of the effective tendon moment arm of the FHB. In addition, removal of the sesamoid can disrupt the delicate tendon balance of the hallux MTP joint, possibly resulting in malalignment. Specifically, a tibial hallux sesamoidectomy can lead to progressive hallux valgus deformity if appropriate technique is not utilized. For these reasons, the sesamoids should not be considered dispensable.

Diagnosis

The diagnostic evaluation of sesamoid disorders begins with a thorough history. Sesamoid stress fractures present with insidious pain onset during and/or after athletic activity. Typically, there is no precipitating trauma or event. In general, pain is localized to the plantar hallux MTP joint and worsens with weight bearing. Toe off is typically quite painful for the patient, making running, jumping, and ascending stairs quite problematic for most patients. The examiner should pay close attention to the location of most severe tenderness to palpation—plantar medial tenderness typically indicates tibial sesamoid pathology, while plantar central to plantar lateral tenderness correlates with fibular sesamoid disease. Swelling may occur in the surrounding soft tissues, and joint motion may be restricted secondary to pain. Holding direct pressure over the diseased sesamoid while passively dorsiflexing the hallux MTP joint will cause severe pain. Tenderness over the dorsal hallux MTP and pain with axial loading and rotation of the hallux MTP joint at the midaxis of joint motion should raise suspicion for symptomatic co-incident hallux rigidus. The differential diagnosis for sesamoid stress fracture also includes stress injury or acute disruption of a bipartite sesamoid synchondrosis, acute sesamoid fracture, sesamoid osteonecrosis (avascular necrosis, AVN), sesamoid chondromalacia, and first metatarsal-sesamoid arthritis. Uniquely, avascular changes may predispose the sesamoids to subsequent fracture and nonunion, a process that is difficult to distinguish from chronic stress injury.

Radiographic analysis includes standing anteroposterior (AP), oblique, and lateral foot views. Axial and tangential sesamoid views assist in assessing for focal arthrosis, plantar osteophytes, or bony prominences ( Fig. 38-8 ). An oblique sesamoid view is helpful in identifying a fracture of the tibial sesamoid. It is recommended that a marker (a radiopaque BB) be placed on the skin overlying the site of tenderness to differentiate which sesamoid is indeed involved as well as confirming that it is not the flexor tendon that is the site of pain.

It is often difficult to differentiate between a fractured and bipartite sesamoid in plain radiographs. In general, a fracture exhibits sharp irregular borders on both sides of separation. In contrast, a bipartite sesamoid has smooth cortical edges and a total size larger than that of a single sesamoid. An injury to the synchondrosis of a bipartite sesamoid will, clinically, behave like a fracture, but present radiographically as a diastasis of a bipartite sesamoid. Bipartite sesamoids are often bilateral, so a radiograph of the contralateral foot can assist in the diagnosis, especially in the case of injury to a bipartite sesamoid.

Other imaging studies are useful in evaluating sesamoid stress fractures. An MRI is an excellent tool to localize disease and differentiate between bone and soft tissue abnormalities. It can assess sesamoid inflammation, viability, joint degeneration, and tendon continuity ( Fig. 38-9 ). MRIs have largely replaced bone scans, which have a high rate of false positives. In the case of fracture and/or suspected first metatarsal-sesamoid arthrosis, a CT scan can help delineate fractures, differentiate them from bipartite sesamoids, and define the degree of fracture healing or metatarsal–sesamoid arthrosis.