Stress fractures in and around the ankle are most often due to repetitive stress. These injuries are often underdiagnosed and may be misdiagnosed as “shin splints.” In fact, the symptoms may persist for an extended period before the diagnosis of a stress fracture is even made. One reason for this is these types of injuries are often sports-related. Athletes, in general, may have a higher pain threshold and continue to exercise, which can exacerbate symptoms.
At the Palo Alto Medical Foundation, we see a predominantly athletic population in our sports medicine department. Our goal is not only to get them back to a functional level but also to get them back to a competitive level as well.
The term “athlete” is often used loosely for anyone who is remotely active. However, the definition of an athlete needs to be better defined in the literature as to individual training regimens and/or activity levels. Stress fractures of the ankle area are caused by weightbearing repetitive stress and you’ll often see these injuries among athletes who participate in track, soccer and basketball. Football and baseball players may suffer these injuries as well.
Running is the predominant sport for eliciting stress fractures of the lower extremity. Track injuries often happen during times of increased mileage training and/or the initiation of speed work. In addition, they can also arise as a result of a change in running surface. Concrete is about five to 10 times as dense as asphalt and can generate a significant increase in cumulative stress on the bones of the lower extremity, thus resulting in fracture.
In the case of the trained athlete who is running on a regular basis, the osteoblastic activity cannot keep up with the catabolic nature of the osteoclastic cells. In the case of the weekend warrior, the individual’s bone density may not be adapted to a sudden increase of running stress. This is not necessarily an issue of a catabolic/anabolic imbalance, but rather an issue of too much too soon. Athletes who have coaches and are training on a regular basis are more aware of such injuries and are often treated sooner than the weekend warrior. In today’s society, a lot of people train on their own. They may come in to see you when they can’t achieve symptom relief with ice, rest and NSAIDs.
Are Age And Sex Contributing Factors In Risk For Stress Fractures?
Not only is the type of sport important as a possible piece of the diagnostic puzzle but the sex of the patient is also relevant. Women tend to be more prone to getting stress fractures. Although this is primarily anecdotal, we’ve found this to be the case in our practice.
There are some studies providing evidence to support this hypothesis. The increased incidence in females is secondary to a syndrome, often coined as the “female triad.” This triad consists of amenorrhea, osteopenia and eating disorders. While other contributing factors may include low body weight, high training intensity, suboptimal nutrition, physical and mental stress, the three etiological factors of the triad are often present in a high percentage of female runners, according to the research.
Barrow, et. al., found menstrual irregularity has a higher correlation with more stress fractures in female collegiate runners: 49 percent in those with zero to five menses per year versus 29 percent in runners reporting 10 to 13 menses per year.1 Amenorrhea has a strong association with decreased bone density averaging a 4 percent loss in bone density per year and up to a 20 percent decrease per year in some cases.2 Oral contraceptives help offset this hypoestrogenic state significantly and thereby reduce the risk of stress fractures in these female runners. The etiology of this exercise-induced amenorrhea is due to an energy drain on the body and a resulting hypothalamic amenorrhea in an attempt to conserve energy in the body.2
The age of the patient can also be a diagnostic marker for helping to identify those who are more predisposed to these kind of fractures. Younger athletic kids are often prone to stress fractures of the growth plate. These are kids who are usually involved in multiple sports year round.
Pubescent and post-menopausal women runners also have a higher incidence of stress fractures of the ankle. In addition, this incidence is particularly high among freshman collegiate runners. Given the increased level of training and competition combined with inexperience, this higher incidence is likely the result of more training errors.3,4
What Biomechanical Factors Are Involved?
There are biomechanical factors to consider as well. Significant tibial varum or valgum can predispose an individual to a certain kind of stress fracture. Most women tend to have a more genu valgum (secondary to the coxa varum in their hip). This can generate more medial tibial stress and thus may lead to more tibial stress fractures.
The alignment of the running surface can be an etiological factor as well. The cant of the road or track can be significant if the individual runs on this cant for an extended period. Doing so can alter the biomechanical forces which are placed on the lower extremity, even to the point where it could generate a stress fracture in a weakened area of bone. In addition, the shoes a runner uses can be a factor in altering biomechanics. The shoes may wear out and/or lack adequate cushioning.
Diagnostic Insights You Can’t Afford To Miss
An array of imaging techniques is available to practitioners. However, these must be correlated with the physical signs and symptoms. Stress fractures of the ankle region can be easily delineated from shin splint-type pain with some simple examination techniques. Shin splints (also known as medial tibial stress syndrome and periostitis) tend to have diffuse tenderness, no pain on loading (hop test on the affected leg), no swelling and no pain on percussion.
Conversely, tibial and fibular stress fractures (and navicular as well) will often have pinpoint tenderness, swelling, pain on loading and pain with percussion over the fracture site.3,4
Some of these fractures take longer to diagnose, depending upon environmental and epidemiological factors. For example, navicular stress fractures are often misdiagnosed due to the initial diffuse nature of the symptoms. Patients often present with ankle pain. In addition, there is often little swelling in the area due to the avascular nature of the navicular. Patients often describe it as a diffuse ankle and midfoot pain that occurs with weightbearing. Also be aware that navicular stress fractures can be localized to the highpoint of the talonavicular joint, known as the “N-spot.” As a result of these factors, proper diagnosis of navicular stress fractures may be delayed between six to 12 months.
To help ensure diagnostic accuracy, you should always consider other etiological factors for lower extremity (exercise induced) pain that may mimic stress fractures in some aspects. Some of these conditions are compartment syndrome, osteochondral lesions of the ankle joint, isolated tibio-fibular diastasis status post-inversion injury, neoplastic lesions, accessory ossicles and possibly vascular anomalies secondary to arterial outlet syndromes.1,5
While some of these are not common pathological entities, you should nevertheless include them in your differential diagnosis and rule them out with the physical exam and imaging techniques.
As we noted above in regard to the physical exam, there are several signs (including pinpoint tenderness) that are indicative of a stress fracture. Most importantly, all of these symptoms worsen with activity. Yet there other pertinent tips that can help you diagnose stress fractures.
One of the best is having the patient hop on the affected limb (the “hop test”) to see if he or she can reproduce the pain. Watch as kids get out of the chair or off the exam table. If they jump down with no pain, then they may not have a fracture. The tuning fork test is an old standby, but is supportive at best with larger bone stress fractures. Always be sure to test the contralateral side. When the patient has pain with ROM of the ankle joint, this may be a tipoff (or indicator) of an ankle osteochondral lesion.
Once you suspect the stress fracture, your diagnostic treatment protocol will vary, depending on the injured area. If the exam warrants further investigation, then an X-ray should be the first step.
Essential Pointers On Imaging Modalities
X-rays for tibial pain should consist of an AP, external oblique and lateral views. The external oblique view is particularly good for detecting any tibial shaft or medial stress fracture. With a tibial shaft fracture, you may see a horizontal (aka “dreaded”) black line on the lateral view. On the AP image, you may see some cortical irregularities with a diaphyseal fracture.
With epiphyseal plate stress fractures, you’ll see increased sclerosis on either side of the plate. For navicular stress fractures, it is best to add a lateral oblique (or navicular view) to your usual foot protocol. In addition, you may pick up on other pathological entities, such as osteochondral lesions of the talar dome and neoplastic lesions of any of the involved bones, both of which can give direct and referred pain. You can view fibular stress fractures with standard ankle images. Anecdotally, we have found more distal fibular stress fractures in female patients.
Bone scans are a very sensitive technique that can aid you in diagnosing a stress fracture. The three phase tech-99 scan will show increased areas of blood flow and inflammation. Due to the sensitivity and cost-effectiveness of this test, it is usually a first line approach.
MRIs are good for detecting very early stress fractures and for ruling out any soft tissue pathology when the bone scan is negative.3,4 With the MRI, you will see the stress fracture as an area of increased marrow edema on the T-2 image. In active kids, you will often find incidental areas of marrow edema (indicating bone stress) that are not symptomatic. Sometimes, “marrow hyperplasia” is present in multiple sites in growing children. The MRI is also the best way of imaging an osteochondral lesion of the talar dome and tibial plateau. Actual stress fractures of the talus itself are rare. These so-called stress fractures are either osteochondral injuries, non-displaced talar neck fractures or posterior talar process injuries.
When ordering an MRI, it is best to give the radiologist as much information as necessary in order to image the involved area properly. You should state what you are looking for and possibly what size sections you want taken (i.e., 3-mm sections as opposed to the usual 5-mm sections).
CT scans are best for navicular stress fractures. Once again, it is best to inform the radiologist what specifically you are looking for so he or she may tailor the test to make sure the slices are not so large they would miss the fracture. We recommend 1.5-mm “cuts.”
A Treatment Guide For Lower Extremity Stress Fractures
While treatment for lower extremity stress fractures, in and around the ankle, varies, here is our treatment protocol for specific lower extremity stress fractures.6
• Medial malleolar. Use a nonweightbearing (NWB), below-knee (BK) cast or boot for three to four weeks, and then proceed to weightbearing (WB) with a BK boot for four weeks. Patient should be able to return to activity (RTA) within 26 to 36 weeks. Orava, et. al., have found healing can take five months with these injuries.7 Shelbourne et. al., recommend open reduction, internal fixation (ORIF) and a NWB BK cast for four weeks, proceeding to a BK boot for two to four weeks, and an estimated RTA in six to 12 weeks.8
• Lateral malleolar. Have the patient maintain WB in an air cast for four to six weeks. The estimated RTA may range from eight to 12 weeks. Be aware that there may be a prolonged healing period, particularly among post-menopausal women.
• Tibial epiphyseal plate. Emphasize NWB in a boot for two to four weeks and then proceed to WB in a boot for two to four weeks. The RTA ranges from four to eight weeks.
• Navicular. For type I fractures (dorsal cortical break only), emphasize NWB in a BK cast or boot for six to eight weeks and then proceed to a WB boot for four weeks. The patient’s RTA may range between four to six months.
Types II and III are fractures that propagate into or completely through the navicular cortex. For optimal treatment, use ORIF with a bone graft across the fracture site. Follow up with six weeks of NWB in a BK cast and then proceed to the WB boot for two to four weeks. The RTA for these patients ranges between three and four months.9
In our experience, most patients who have had conservative treatment of types II and III navicular injuries either never completely heal, give up on their sport, and/or develop significant talonavicular and sometimes cuneo-navicular arthrosis.
• Medial tibial. Have these patients wear an Aircast (pneumatic) brace for four weeks. The patient’s RTA may occur between four and 12 weeks. This is supported by the work of Swenson, et. al.10 You may use a “standard” version of the brace for lower lesions or a “long leg” version for more proximal lesions.
• Anterior tibial. Use the Aircast long leg brace with anterior panel for four to six weeks of NWB. Then proceed to six weeks of WB. The patient’s RTA may range between 12 and 26 weeks. Clanton, et. al., also recommend electric bone stimulation and even IM Nailing for recalcitrant injuries.11
All stress fracture time protocols here are general references. The succession of each stage of treatment is based on pain. Remember, X-rays and other imaging techniques may lag behind the actual healing so assessing clinical signs and symptoms is paramount. We also address the patient’s lower extremity biomechanics with orthoses and shoe accommodations when necessary.
Key Considerations In Facilitating A Return To Activity
Once the patient is able to resume weightbearing without pain, then the patient can proceed to physical therapy. The most important role of physical therapy is to re-educate the muscles neurally in the ankle with stabilization exercises (such as standing on one leg flat on the ground and on a BAPS stabilization board) being particularly helpful. In addition, physical therapy can also strengthen the muscles and tendons in the lower extremity, as well as reduce any residual edema with modalities such as electrical stimulation.
Ice and massage are always good therapy adjuncts. However, you should avoid using antiinflammatories in the acute phase as they have been shown to delay early bone mineralization.
During the nonweightbearing phase in the boot, we often allow our patients to use a stationary bike or swim with a pull buoy to support their legs (although talar osteochondral lesions are a notable exception). Basketball players may begin shooting baskets once they begin the weightbearing phase.
There is a gradual protocol for returning runners to their activities. Have them begin by walking every other day (EOD) up to 30 to 40 minutes. If they can do this without pain for a week, have them proceed to running/walking EOD for 15 to 20 minutes. The next stage would be running 30 to 40 minutes EOD and then every day without pain. Each stage is at least a week apart. In addition, you should tailor the return to activity protocol to the patient’s specific sport.
How To Handle Recalcitrant Fractures
If the fracture is not healing, then a bone stimulator is often warranted. When the patient who has the fracture is medically compromised with conditions like osteoporosis, eating disorders or previous smoking, etc., we initiate a bone stimulator. Other factors for bone stimulation include the location of the fracture. Navicular and anterior tibial fractures are notoriously slow to heal.
Also be aware that medical consultation may be in order to determine the reason for the delayed healing. An endocrinologist consult may be helpful in treating female patients who fit the “triad” we discussed earlier. In addition, if the bone pain is from a tumor-like lesion that was excised, then an oncology consult may be warranted.
Stress fractures about the ankle can be difficult to diagnose. The difficulty in diagnosis lies with the ability to know when stress fractures should be higher on your list of differential diagnoses. However, by using the proper physical exam and imaging techniques, you should be able to easily identify and treat these injuries.
Dr. Saxena is a Fellow of the American College of Foot and Ankle Surgeons, American Academy of Podiatric Sports Medicine and the American Academy of Foot and Ankle Orthopedics and Medicine. He practices within the Department of Sports Medicine at the Palo Alto Medical Foundation in Palo Alto, Calif.
Dr. Cassidy is a Fellow within the Department of Sports Medicine at the Palo Alto Medical Foundation in Palo Alto, Calif.
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