Clinical value of grading the scintigraphic appearances of tibial stress fractures in military recruits.

PURPOSE: This study evaluated the relation between the scintigraphic appearances of tibial stress fracture in military recruits and the likelihood that they would complete basic military training. MATERIALS AND METHODS: The authors retrospectively reviewed 58 Tc-99m MDP scans of recruits referred for possible tibial stress fracture and graded them according to the criteria of Zwas et al. (1987). Stress fracture appearances were correlated with clinical information such as the duration of rehabilitation and final outcome with regard to completion of the initial basic military training program. RESULTS: Thirty-seven of the 58 patients (64%) had tibial stress fractures, all of which were located in the tibial diaphysis, with most occurring in the middle and lower thirds. Most (23 of 37) patients had stress fractures of grade I or II, and the others had grade III or IV stress fractures. There was no statistical difference in the proportion of patients with bilateral fractures between grades I-II and III-IV. There was no significant difference in the duration of rehabilitation for recruits successfully recovering from grade III-IV fractures compared with grade I-II fracture. There was a greater proportion of patients with lower grade fractures than higher grade fractures (P = 0.0006) who, despite rehabilitation, could not continue training because of unremitting or recurring pain at the fracture site and were medically discharged from military service. CONCLUSIONS: Contrary to expectation, recruits with higher-grade stress fractures were not less likely to complete basic military training compared with recruits with lower grade stress fractures.     

Magnetic resonance imaging of para-acetabular insufficiency fractures in patients with malignancy

AIM: To describe the characteristic magnetic resonance imaging (MRI) findings of para-acetabular insufficiency fractures in patients with malignancy, and compare the MRI appearance of these fractures with that of metastatic bone disease. MATERIALS AND METHODS: MRI examinations were reviewed in 16 patients with a known malignant tumour and severe hip pain that raised the possibility of local recurrence or metastatic disease. Six patients had received pelvic irradiation, and three patients were receiving steroid medication. RESULTS: The total number of fractures detected was 21: a solitary fracture was present in 11 patients and five patients had bilateral para-acetabular fractures. Two patients had associated sacral insufficiency fractures, and one of them had stress fractures involving both acetabular columns. Conventional radiography allowed the diagnosis of 14 (67%) fractures; six (28%) radiographic examinations were negative; and one (5%) examination was equivocal for fracture. Available scintigraphic and computed tomography (CT) studies revealed typical findings of fracture. Using MRI, insufficiency fractures appeared as linear regions of low signal intensity on T1- and T2-weighted images. Marked marrow oedema was evident in all cases. Fractures characteristically were parallel to the superior acetabulum in a curvilinear fashion in 18 (86%) instances, and were oblique in three (14%) instances. The fractures demonstrated considerable enhancement after intravenous gadolinium administration. No associated soft tissue masses were documented. CONCLUSION: Para-acetabular insufficiency fractures are a cause of hip pain, which may mimic skeletal metastasis in the patient with malignancy and pelvic irradiation. Recognition of the characteristic MRI findings of these fractures can preclude misdiagnosis and unnecessary bone biopsy.     

Stress fractures in the lower extremity. The importance of increasing awareness amongst radiologists

Stress fractures are fatigue injuries of bone usually caused by changes in training regimen in the population of military recruits and both professional and recreational athletes. Raised levels of sporting activity in today's population and refined imaging technologies have caused a rise in reported incidence of stress fractures in the past decades, now making up more than 10% of cases in a typical sports medicine practice. Background information (including etiology, epidemiology, clinical presentation and treatment and prevention) as well as state of the art imaging of stress fractures will be discussed to increase awareness amongst radiologists, providing the tools to play an important role in diagnosis and prognosis of stress fractures. Specific fracture sites in the lower extremity will be addressed, covering the far majority of stress fracture incidence. Proper communication between treating physician, physical therapist and radiologist is needed to obtain a high index of suspicion for this easily overlooked entity. Radiographs are not reliable for detection of stress fractures and radiologists should not falsely be comforted by them, which could result in delayed diagnosis and possibly permanent consequences for the patient. Although radiographs are mandatory to rule out differentials, they should be followed through when negative, preferably by magnetic resonance imaging (MRI), as this technique has proven to be superior to bone scintigraphy. CT can be beneficial in a limited number of patients, but should not be used routinely.     

Negative bone scans in impending tibial stress fractures. A report of three cases

Three highly motivated military recruits who presented with tibial pain on exertion are reported. Their initial bone scan assessments to rule out stress fracture were normal, and the recruits were returned to demanding training. One month later, because of persistent and increasing tibial pain, they were rescanned and focal activity representative of tibial stress fractures was found in each case. Until now it has been assumed that a negative bone scan ruled out a stress fracture unequivocally. Our reported cases show that bone pain may in fact precede scintigraphic evidence of a stress fracture. Persistent and increasing bone pain during demanding physical activity, even in the presence of a prior normal bone scan, may represent stress fracture and repeat bone scan may be indicated.     

Stress fractures of the ribs in elite competitive rowers: a report of nine cases

Objective The objective was to report the clinical and imaging patterns of nine cases of stress fractures of the rib diagnosed in Italian Olympic rowers. Patients and methods Nine patients with stress fractures of the rib detected from 103 (8.7%) Italian team rowers competing between May 2000 and May 2006 were identified based on the database of a sports medicine institute. All athletes were male. They were aged between 17 and 31 years (mean: 24.4). Patient weight, fracture location, rowing side and imaging methods employed were noted. Results The diagnosis was made based on history, clinical examination and Tc-99m MDP bone scintigraphy. Eight of the 9 fractures were located anterolaterally between the fourth and ninth rib. In 1 of the 5 athletes with standard radiographs, a fracture line was visible and in 4 there was callus formation. In 2 athletes sonography was performed, which detected discontinuity of the rib surface and callus formation (1 case each). Conclusion Stress fractures of the ribs are relatively common in competitive rowers. They are characterized by increasing lateral chest pain and typical scintigraphic, radiographic and sonographic findings.     

Stress fractures in the young athlete: a pictorial review

Stress fractures are an uncommon but important source of pain and disability in young athletes. The presentation and differential diagnosis of stress fractures in young athletes differs from that of older athletes. This pictorial review outlines the pathogenesis and imaging features of stress fractures. Other pathologies that can mimic stress fractures and the advantages of the use of magnetic resonance imaging will be discussed. An imaging algorithm for a suspected stress fracture is suggested.     

Classification and return-to-play considerations for stress fractures

Stress fractures are common injuries, particularly in endurance athletes. Stress fracture management should take into consideration the injury site (low risk versus high risk), the grade (extent of microdamage accumulation), and the individual's competitive situation. The authors briefly discuss the pathophysiology and diagnostic process of stress fractures and expand on the classification of stress fractures and its impact on return-to-play decision making based on the relative risk of the fracture.     

Stress fracture of the pubic ramus in a swimmer

Stress fracture is common in military recruits, joggers, and runners. Stress fracture in the pubic ramus is not common, and it constitutes only 1.25% of all stress fractures. A stress fracture, avulsion type of the pubis at the insertion of adductor magnus on an active swimmer is reported here.     

Role of MRI in the diagnosis of insufficiency fractures of the sacrum and acetabular roof

 Objective. To review the risk factors and the radiological appearance of insufficiency fractures of the sacrum and acetabular roof. Design and patients. Twenty patients with sacral and acetabular roof insufficiency fractures were reviewed retrospectively. There were 16 women (80%) and 4 males (age range 48–86 years, excluding an 8-year-old boy). Thirteen patients had a known tumour, and nine had received pelvic irradiation. All patients, except one who was asymptomatic, presented with low back or hip pain. In patients with a known tumor, metastases were suspected. Plain radiography (20), bone scintigrams (16), MR examinations (20), and bone densitometry (14) were performed. Nine patients also each had a CT scan. Results and conclusions. In three cases the CT scan performed 10–25 days after onset of symptoms was interpreted as normal. MR examination performed a few days after the CT scan showed in each of these three patients a fracture line with a band of edema. Scintigraphy was very sensitive, but the H-shaped pattern of sacral uptake, specific for an insufficiency fracture, was detected in only three of 16 cases. The earliest MR sign was medullary edema, seen as early as 18 days after the onset of symptoms. On spin echo (SE) T1-weighted images (T1WI), the hypointense signal of edema could mask a fracture line. On SE T2WI the fracture line could be detected within the hyperintense edema (10 of 17 patients with examinations including SE T2WI). However, in four patients a fracture of the sacrum was not seen on T2WI, these having been obtained in the axial plane. For this reason, intravenous gadolinium was injected, revealing a fracture line in 12 of 14 examinations, or fat suppression sequences were performed, revealing a fracture line in five of five cases. The total number of fractures detected was 17 [15 fractures of the sacrum (bilateral in 10 cases) and two of the acetabular roof]. At a later stage, the edema resolved and the fracture was clearly seen. The two cases of fracture of the acetabular roof were easily recognized at MRI, particularly in the sagittal plane.     

Interpretation and classification of bone scintigraphic findings in stress fractures

A new system for classification of stress fractures identified by bone scintigraphy was developed and divided into four grades according to lesion dimension, bone extension, and tracer accumulation. The scintigraphic findings were evaluated for severity of lesions by extent of the visualized bone response, ranging from ill-defined cortical lesions with slightly increased activity (I) to well-defined intramedullary transcortical lesions with intensely increased activity (IV). Bone scintigraphies using [99mTc]MDP were obtained in 310 military recruits suspected of having stress fractures. In 235 patients, 391 stress fractures were diagnosed. Forty percent of the lesions were asymptomatic. Most of the lesions were in the tibiae (72%), and 87% of the patients had one or two lesions, while 13% had three to five lesions. Eighty-five percent of the lesions were classified as mild and showed early and more complete resolution on follow-up studies after treatment as compared to the severe grades. Furthermore, specific scintigraphic patterns have been introduced for distinguishing inflammatory shin-splints from stress fractures, allowing for their appropriate early treatment. Thus, early recognition of mild stress fracture scintigraphic patterns representing the beginning of pathologic bone response to stress enabled a prompt and effective treatment to prevent progression of lesions, protracted disability, and complications.     

The effect of leg strength on the incidence of lower extremity overuse injuries during military training

This study examined the effects of strength, aerobic fitness, and activity profile on the incidence of overuse injuries, particularly stress fractures, during military training. A total of 136 military recruits were followed during 9 weeks of basic training. Maximal strength and aerobic fitness were determined by a one-repetition maximum leg press and a 2,000-m run, respectively. An activity profile was determined by the recruit's activity history. Twelve recruits (8.8%) were diagnosed with stress fractures. Recruits who were 1 SD below the population mean in both absolute (98.4 +/- 36.6 kg) and relative strength (1.72 +/- 0.61 kg/kg of body weight) had a five times greater risk for stress fracture (p < 0.05) than stronger recruits. Poor aerobic fitness did not appear to be related to any increased incidence of stress fracture. It appears that recruits with lower body strength levels, within 1 SD of the population mean, have a reduced incidence of stress fractures during military training.     

Delay in diagnosis of neck of femur stress fracture in a female military recruit

We report the delay in diagnosis of a Neck of Femur (NOF) stress fracture in mixed sex basic military training. Stress fractures are common in military training with the incidence reported as ranging between 3.2-31%. NOF stress fractures, whilst only representing around 8% of stress fractures are associated with a high morbidity. It is imperative that medical officers looking after military recruits have a sound knowledge of the potential signs, symptoms and presentation of these injuries. Medical officers should always remains vigilant for stress fractures especially in mixed military training.     

Imaging findings in symptomatic patients with femoral diaphyseal stress injuries

Purpose: To assess the imaging findings seen in symptomatic patients with stress injuries of the femoral diaphysis.

Material and Methods: Seven patients (5 F, 2 M, age range 16 to 56 years, mean 38 years) underwent imaging evaluation of the symptomatic lower extremity due to an insidious onset of thigh or groin pain unrelated to trauma. Imaging studies included radiography and magnetic resonance imaging (MRI) in seven patients, bone scintigraphy in five, and computed tomography (CT) in three.

Results: Radiographs depicted three frank fractures in two patients, and revealed findings of stress injury in six patients. Available scintigraphic and CT findings were abnormal. On MR images, a solitary fracture was seen in two patients; two patients presented with bilateral stress fractures of the femoral diaphysis; and all seven patients had the imaging features of stress injury. Femoral diaphyseal stress fractures (n = 6) appeared as linear regions of T1- and T2-weighted low signal intensity, surrounded by diffuse bone marrow edema. Three of the six frank fractures, with an evident fracture line, were longitudinal and parallel to the cortical surface.

Conclusion: Femoral diaphyseal stress fractures are often inconspicuous with conventional radiography. MRI depicts the changes of stress injury in the femoral diaphysis, and is particularly useful in documenting the presence, morphology, and extent of fracture(s), information valuable for definitive diagnosis and appropriate management.     

Subchondral insufficiency fracture of the femoral head in young adults

A subchondral insufficiency fracture of the femoral head (SIF) is generally observed in elderly women. In addition, SIF has been reported to occur in young military trainees, which are considered to be due to a fatigue stress fracture. This report reviewed five cases of SIF in young adults without any history of overexertion or antecedent trauma. The clinical findings, time to the initial radiograph, time to the initial magnetic resonance imaging (MRI), and follow-up period were investigated. Radiographs and MRI were obtained in both hips. Bone mineral density and bone scintigram were performed. Measurements of a bone mineral density indicated presence of osteopenia in three patients. MRI disclosed a discontinuous irregular-shaped low-intensity band surrounded by bone marrow edema in all cases. After conservative treatments, one patient's condition resolved, while four patients underwent femoral head collapse resulting in surgical treatment. In these four patients, the diagnosis of SIF was histologically confirmed. In addition, the histological findings showed thin disconnected bone trabeculae, thus indicating the presence of some degree of osteopenia. These patients were considered to demonstrate an insufficiency fracture rather than a fatigue stress fracture based on both clinical findings and histological findings. SIF needs to be considered in patients presenting with hip pain even in young cases.     

Stress fracture of the tarsal navicular

Stress fractures of the lower extremity are common among military members and athletes at all levels of participation. They typically occur when an individual begins a new or different type of physical training or during periods of abrupt increase in the level of training. Stress fractures represent an incomplete remodeling of bone that occurs secondary to repetitive mechanical loading. In response to this increased loading, the osteoclastic resorption of lamellar bone outpaces the ability of the osteoblasts to create new lamellar bone, eventually leading to structural failure. The following case report reviews the typical clinical presentation, imaging findings, and treatment of the tarsal navicular stress fracture.     

Spontaneous stress fractures of the femoral neck

The diagnosis of spontaneous stress fractures of the femoral neck, a form of insufficiency stress fracture, can be missed easily. Patients present with unremitting hip pain without a history of significant trauma or unusual increase in daily activity. The initial radiographic features include osteoporosis, minor alterations of trabecular alignment, minimal extracortical or endosteal reaction, and lucent fracture lines. Initial scintigraphic examinations performed in three of four patients showed focal increased radionuclide uptake in two and no focal abnormality in one. Emphasis is placed on the paucity of early findings. Evaluation of patients with persistent hip pain requires a high degree of clinical suspicion and close follow-up; the sequelae of undetected spontaneous fractures are subcapital fracture with displacement, angular deformity, and avascular necrosis of the femoral head.     

Lower limb pain and disability following strenuous activity

One hundred five military recruits were evaluated in our outpatient clinic for pain in the lower limb following prolonged sustained physical effort and strain. Plain x-ray investigations augmented by technetium-99m polyphosphate demonstrated the presence of 80 stress fractures in 52.4% of the patients. None of the patients had any anatomical abnormalities of the lower limbs. Of the stress fractures seen, 82.5% were located in the tibial and femoral diaphyses and 16.2% were in the small bones of the foot. Plain radiography gave false negative results in 87.3% of documented fractures. The remaining 47.6% of these recruits had no evidence of stress fractures. However, 74% of them had various anatomical deformities of the lower limb, mainly of the feet. Correction of these deformities enabled these patients to return to previous strenuous activities of their basic military training. The pathogenesis of stress fractures is still not understood. However, the development of persistent pain in the lower limb following prolonged sustained intensive physical activity needs further investigation. Anatomical deformities may be associated with development of stress fractures.