Bilateral Tibial Stress Fractures and Osteoporosis in a Young Patient

Abstract

Stress fractures result from microscopic bone injury due to repetitive submaximal stress and include fatigue and insufficiency fracture components. Fatigue fractures generally occur in runners and athletes and are caused by abnormal physical load on the bone. On the other hand, insufficiency fractures are generally seen in the elderly secondary to osteoporosis, typically involving the pelvis and surrounding bones. Insufficiency fracture occurs as a result of normal loading in the abnormal bone. In this case report, we describe a young patient with bilateral tibial stress fractures with both fatigue and insufficiency components.

Bone is a dynamic structure involving a delicate balance between formation and breakdown under the endocrine system’s control. Key factors involved in the auto-repair mechanisms of the bone tissue include the tension and load. However, repetitive loads on the bone exceeding its auto-repair capabilities are likely to result in stress fractures, ¹¹ representing a type of overuse injury that occurs more commonly in athletes and military personnel. Stress fractures are more common in women than men because of anatomical, biomechanical, and hormonal factors. ¹ Of these fractures, 95% occur in the lower extremities, with proximal tibia being the most common site of involvement. ¹⁵ Approximately 16% of the cases have been reported to involve both sides. Stress fractures are divided into 2 categories: fatigue fractures and insufficiency fractures. ⁴ Fatigue fractures occur in healthy bone tissue because of abnormal mechanical loads, mostly in young adults, and particularly affecting the weight-bearing bones. Typical risk groups include athletes, dancers, and military personnel. ¹⁶ On the other hand, insufficiency fractures occur because of reduced bone strength and involve normal or mildly increased mechanical physical load on the bone. ³ In this case report, we will describe a young patient with bilateral tibial stress fractures that include both fatigue and insufficiency fracture components.

The Patient

This 27-year-old female patient presented to our outpatient unit with a 2-week history of bilateral knee pain. Although her medical history was unremarkable for trauma, she reported strenuous and regular exercise, mainly involving running, in the past month as a part of her preparation for police academy entrance examinations. Her pain was reported to get worse on running, with relief on rest. She had no previously diagnosed health conditions or regular use of medications. Her family history revealed cases of premature osteoporosis in some family members. Our patient had no history of amenorrhea or an eating disorder. Her weight was 67 kg and height was 173 cm. On physical examination, she had tenderness upon palpation on the proximal tibias. Also, there was flexion limitation due to pain in both knee joints. McMurray and Apley compression tests were negative on both sides, although she had pain in the knee’s medial part. The hop test performed on the patient was painful for both knees. The anterior and posterior drawer tests were negative. Neurological examination was normal, and distal peripheral pulses could be detected in both legs. Anatomically, she had no varus or valgus deformity, and the Q angles in the right and left legs were 20° and 23°, respectively. The right and left legs had the same length.

Plain radiographs obtained to rule out osseous pathological conditions showed no pathology (Figures 1 and 2). Bilateral knee magnetic resonance imaging (MRI) requested on a suspicion of stress fractures and meniscal pathology showed bilateral stress fractures and soft tissue edema in the medial knee (Figures 3 and 4).

Figure 1.

Radiograph of patient’s two knees (anterior-posterior).

Figure 2.

Radiograph of patient’s two knees (lateral).

Figure 3.

Sagittal proton density weighted spair magnetic resonance image of right knee.

Figure 4.

Sagittal proton density weighted spair magnetic resonance image of left knee.

Laboratory results showed a vitamin D level of 8 ng/mL (25-100 ng/mL), with no abnormalities in calcium, phosphorus, alkaline phosphatase, parathyroid hormone, thyroid-stimulating hormone, estrogen, progesterone, and prolactin levels. Vitamin D deficiency was thought to be caused by inadequate oral intake and insufficient exposure to sunlight. Bone densitometry result was consistent with osteoporosis. The Z score for lumbar spine and femoral neck was −2.5.

Rest and quadriceps exercises were recommended to the patient, with prescription of nonsteroidal anti-inflammatory drug, calcium, and vitamin D₃. At 1-month follow-up examinations, she reported no improvement in pain. Transcutaneous electrical stimulation, ultrasound, hot pack, and physical exercise therapy were initiated. Subsequently, her pain was reduced, and her vitamin D level at 3 months was 38 ng/mL.

Discussion

Stress fractures represent a common form of overuse injury and result from repetitive submaximal physical loads on the bone that occur over a period of time. ¹⁷ All age groups may be affected, and military personnel constitute a particular risk group. From an etiologic viewpoint, stress fractures may be grouped into 2 categories: fatigue fractures and insufficiency fractures. While the latter group is because of normal stress on the abnormal bone, the former results from abnormal stress exposure on the normal bone. ⁶ Bone tissue is in the cycle of formation and breakdown, and it can repair itself. Literature reports mainly emphasize the role of balanced or unbalanced submaximal forces that cause microfractures, ultimately leading to stress fractures. Stress fractures occur when the bone repair mechanisms fail and physical loads persist, indicating that stress fractures represent a continuum of events rather than being an acute condition.^7,20,22 In a study by Matheson et al ¹³ involving 320 cases with stress fractures, the site of the fracture was 49.1% tibia, 25.3% tarsal bones, 7.2% metatarsal bones, 6.6% femur, 1.6% fibula, 0.9% pelvis, and 0.6% sesamoid. In the same study, 16.6% of the cases had bilateral stress fractures. ¹³ Fatigue fracture is mostly seen in the tibia, fibula, metatarsals, femoral neck, pubic rami, calcaneus, and navicular bones, while insufficiency fractures are also seen in the sacrum, pubic rami, superior acetabulum, femoral head, and medial femoral condyle. Our patient also had bilateral fractures at the most common site of involvement, that is, the tibia.

Several external and internal factors are involved in the predisposition to stress fractures. Examples of internal factors include the anatomy, age, gender, structural foot disorders, loss of bone quality, vascular disorders, and hormonal disturbances (particularly in women). The type and intensity of the physical activity, exercise surface, training methodology and equipment, and nutrition are among the external factors. Muscular fatigue, and reduced muscle mass, particularly in women, may lead to reduced muscular protection against the physical stress on bones, ⁹ resulting in an increased risk of fatigue fractures. On the other hand, several predisposing factors for bone breakdown play a role in the development of insufficiency fractures, and these include menstrual disorders, osteoporosis, diabetic or idiopathic neuropathy, smoking, alcohol consumption, anorexia nervosa, Paget’s disease, and rheumatoid arthritis. ¹⁴

We summarize the features of the insufficiency and fatigue fracture in Table 1.^10,12

Table 1.

Summary of the differences between fatigue and insufficiency fractures

	Fatigue Fractures	Insufficiency Fractures
Definition	Abnormal physical load on the bone	As a result of normal or abnormal loading in the abnormal bone
Epidemiology	Young athletes: women > men	Elderly low body mass index: women > men
Pathophysiology	Abnormal load leads to remodeling; when resorption is greater than replacement, a fracture occurs	Normal load on weakened bone (osteopenia or metabolic bone disease)
Common locations	Tibia, fibula, metatarsals, femoral neck, pubic rami, calcaneus, and navicular	Sacrum, pubic rami, superior acetabulum, femoral head, medial femoral condyle
Imaging	The earliest radiographic sign is the “gray cortex” sign. A periosteal reaction and endosteal callous formation with cortical thickening follow as the injury. Magnetic resonance imaging features, including periosteal edema and marrow edema, are best demonstrated on images from fluid-sensitive sequences. As the severity of the injury progresses, a hypointense linear fracture line may be seen. In imaging, stress fractures cannot be distinguished as insufficiency or fatigue fractures. Anamnesis and physical examination are our most important assistants.

It can be difficult to diagnose stress fractures. The main symptom of stress fractures is localized pain, which increases with activity and decreases with rest. Physical examination shows localized sensitivity and tenderness with or without swelling. Range of motion examination and provocative tests are required to reveal pain in deep located stress fractures. The hop test is a provocative test for lower extremity stress fractures. In this test, the patient is asked to jump on a single leg and the test is positive when intense localized pain is triggered in the patient. Static alignment and biomechanics can identify structural abnormalities and muscle imbalances that can predispose to specific injuries. Differential diagnoses include tendinopathies, nerve compression, compartment syndrome, and tumors.

The first imaging method to be performed in suspected stress fracture is plain radiography. Plain radiographs are mostly normal in the early stage and radiographic abnormalities usually begin to appear after 3 weeks of evolution. The sensitivity of plain radiography in the early period is about 10%. ¹⁸ The findings suggesting stress fracture on radiography are periosteal thickening and subtle linear sclerosis. Ultrasonography is increasingly available and can provide important clues in the diagnosis of the superficial stress fracture. Periosteal elevation, cortical break, and soft tissue edema can be seen with ultrasonography. Its advantages are that it is cost-effective and can be applied immediately at the bedside. Computed tomography is advantageous in showing the longitudinal fracture line and in evaluating spinal stress fracture. Pars interarticularis stress fracture (spondylolysis), which cannot be seen on plain radiography and MRI, can be seen in computed tomography. ¹⁹ Its disadvantages are that it cannot show bone edema and contains ionizing radiation. Bone scintigraphy was previously accepted as the gold standard in the diagnosis of stress fracture because of its high sensitivity. However, because of its low specificity, it has left its place mostly to MRI. Single-photon emission computed tomography is mostly used to evaluate dorsal spine stress fracture. ²³

MRI has very high sensitivity and specificity (100% and 85%, respectively) in the diagnosis of stress fractures. It is the second imaging method to be performed after plain radiography in suspicion of the stress fracture. ¹² Typical findings are hypointense fracture line on T1- and T2-weighted images, and bone marrow and soft tissue edema on T2 fat-suppressed and short tau inversion recovery sequences. MRI findings of medial tibial stress fractures can be classified by Fredericson et al ⁵ according to fluid-sensitive and T1-weighted features of stress injury (Table 2). Kijowski et al ⁸ elaborated on this issue to determine the clinical significance of imaging findings. According to this study, the estimated time to return to sports activities in patients with stage 1 stress fracture is 2 to 3 weeks, while this period is 6 to 7 weeks in patients with stage 2 through 4a stress fractures. In patients with a frank stress fracture (stage 4b), this period lasts an average of 9 to 10 weeks. ⁸ Therefore, the MRI staging system is useful in determining the severity of the disease and the healing process.

Table 2.

Fredericson MRI classification for medial tibial stress fractures

Grade	Periosteal Edema	Marrow STIR SI	Marrow T1 SI	Intracortical Signal
0	No	Normal	Normal	Normal
1	Yes	Normal	Normal	Normal
2	Yes	High	Normal	Normal
3	Yes	High	Low	Normal
4a	Yes	High	Low	Focal abnormality
4b	Yes	High	Low	Linear fracture

MRI, magnetic resonance imaging; SI, signal intensity; STIR, short tau inversion recovery.

In a report by Yavuz and Özkan, ²² it was stated that while plain radiographs may suffice for a diagnosis of older stress fractures, more advanced imaging modalities such as bone scintigraphy, MRI, or computed tomography may be required for earlier stages because of the absence of callus formation. Also, MRI was reported to represent the current gold standard diagnostic technique, replacing scintigraphy, as this latter modality offers lower specificity and higher false positivity (infection or malignancy) rates despite being highly sensitive. ²² In another study by Turk et al, ²¹ computed tomography was considered the gold standard diagnostic technique in a patient with longitudinal tibial fracture. In our patient, although plain radiographs showed no pathology, MRI showed the presence of fracture lines and bone marrow edema bilaterally.

Treatment of stress fractures include rest, nonsteroidal anti-inflammatory drugs, and plaster casts ⁶ ; several other treatments have also been proposed, including calcium and vitamin D, bisphosphonates, extracorporeal shock wave therapy, calcitonin, and oral contraceptives in appropriate patients, although more studies are warranted. ²²

Stress fractures, including both fatigue and insufficiency types, are frequently encountered in clinical practice as a source of pain in both athletes and patients with predisposing conditions. Radiography is the imaging modality of choice for baseline diagnosis. MRI has greatly improved our ability to diagnose radiographically occult stress fractures. Tc-99m bone scan and computed tomography may also be useful as diagnostic tools. Although fatigue and insufficiency fractures can be self-limited and go onto healing even without diagnosis, there is usually value in initiating prompt therapeutic measures, as incomplete stress fractures have the potential of progressing to completion and requiring more invasive treatment or delay in return to activity. ² Stress fracture has been known for many years. In this article, we have discussed about the importance of diagnosis and treatment.

This case is a young and fit woman presenting with simultaneous bilateral proximal tibia fractures. In her first history, she did not have any significant risk factors for stress fractures. This could be a fatigue fracture given the increased physical activity and sports recently for the examination. However, the low bone mineral density and vitamin D level in the examinations and research show the effect of insufficiency fracture together with the fatigue component. In conclusion, stress fractures represent a medical condition. While they may present as fatigue fractures in athletes, insufficiency fractures are the predominant form in the elderly and in subjects with osteoporosis or other medical conditions. Although in many case reports stress fractures are described either as fatigue or insufficiency fractures, our patient had both components. Patients with stress fractures should always be investigated for the presence of osteoporosis or other underlying conditions.