MRI in stress fracture

Biologic therapies in stress fractures: Current concepts

Stress fractures, a common overuse injury in physically active individuals, present a significant challenge for athletes and military personnel. Patients who sustain stress fractures have demanding training regimes where periods of rest and immobilisation have unacceptable negative consequences on sports goals and finances. Aside from being an overuse injury, there are various contributing risk factors that put certain individuals at risk of a stress fracture. The main two being nutritional deficiencies and hormonal variations, which have significant effects on bone metabolism and turnover. Historically, treatment of stress fractures focused on conservative strategies such as rest and immobilisation. Calcium and vitamin D deficiencies have been closely linked to stress fractures and so over time supplementation has also played a role in treatment. With the introduction of biologics into orthopaedics, newer treatment strategies have been applied to accelerate fracture healing and perhaps improve fracture callus quality. If such therapies can reduce time spent away from sport and activity, it would be ideal for treating stress fractures. This article aims to offer insights into the evolving landscape of stress fracture management. It investigates the pre-clinical evidence and available published clinical applications. Though fracture healing is well understood, the role of biologics for fracture healing is still indeterminate. Available literature for the use of biologic therapies in stress fractures are restricted and most reports have used biologics as a supplement to surgical fixation in subjects in studies that lack control groups. Randomised control trials have been proposed and registered by a few groups, with results awaited. Assessing individuals for risk factors, addressing hormonal imbalances and nutritional deficiencies seems like an effective approach to addressing the burden of stress fractures. We await better designed trials and studies to accurately determine the clinical benefit of adding biologics to the management of these injuries.

Lumbar Pedicular Stress Fracture Post-laminectomy: a Case Report

We present the case of a 74-year-old male suffering from degenerative lumbar spinal stenosis with neurogenic claudication resulting in reduced walking distance. MR imaging indicated spinal canal stenosis at the level of L3–L4 and L4–L5 due to degenerative discopathy, discal extrusion, and facet arthrosis. After conservative treatment had failed, a multilevel laminectomy was performed. Four months postoperatively, the patient developed a stress fracture of the L4 pedicle. Pedicular stress fractures are uncommon and few case reports are found in the literature. Usually, they occur due to contralateral spondylolysis or congenital anomalies. The findings in this case however suggest a change of biomechanical load over the pedicle due to spinal surgery. An overview of the literature concerning spinal instability after laminectomy is provided. Spinal decompressive surgery can significantly change the biomechanical forces on the spinal structures, resulting in important postoperative complications. Whether pedicle stress fracture in this case is a result of pre- or postoperative circumstances remains a subject for discussion.

Proximal fibular resection improves knee biomechanics and enhances tibial stress fracture healing in patients with osteoarthritis with varus deformity: a prospective, randomized control analysis

Background

The present study aimed to evaluate the functional outcome of single-stage total knee arthroplasty using long-stem tibial component with proximal fibular resection (PFR) for patients with knee osteoarthritis with varus deformity associated with tibial stress fracture.

Method

A cohort of 62 patients with a mean age 71.63 ± 7.40 years who met the criteria were randomized to a study group and a control group. Patients in the study group underwent single-stage total knee arthroplasty using long-stem tibial component with PFR. The control group received conventional treatment. All patients were followed at 1, 3, 6 and 12 month(s) after surgery. Standard anteroposterior and lateral weight bearing knee X-rays were analyzed. Western Ontario and Mc-master Universities Osteoarthritis Index score (WOMAC) and the visual analog scale (VAS) score were used to assess the functional outcome. The level of significance was set at p < 0.05 levels.

Results

One patient in the study group was lost to follow-up, leaving 61 patients for final assessment. The WOMAC total score and mean VAS score were significantly better in study group than in control group at final follow-up (p < 0.05). All fractures were successfully united in a mean time of 12.26 ± 1.20 weeks in study group. A total of 16 patients in control group had delayed union, five had established nonunion and required further interventions. No complications relating to surgery was detected.

Conclusion

Total knee arthroplasty with PFR for knee arthritis with varus deformity associated with tibial stress fractures restores limb alignment, improves biomechanics, enhances fracture healing and provides excellent functional outcome.

A Review and Proposed Rationale for the use of Ultrasonography as a Diagnostic Modality in the Identification of Bone Stress Injuries

Bone stress injuries are common in military personnel and athletes. The delayed diagnosis of a bone stress injury can lead to a more severe injury that requires a longer period of treatment. The early detection of bone stress injuries is a central part of management. Currently, the reference standard for detecting bone stress injuries is magnetic resonance imaging. However, the expanding use of point-of-care ultrasonography (US) may enable the early detection of bone stress injuries in the clinical setting. In this article, we review the US detection of bone stress injuries, as well as discuss the rationale for the use of US in the diagnosis of these injuries.

Stress fractures of the foot and ankle, part 1: biomechanics of bone and principles of imaging and treatment

A stress fracture is a focal failure of bone induced by the summation of repetitive forces, which overwhelms the normal bone remodeling cycle. This review, the first of two parts, discusses the general principles of stress fractures of the foot and ankle. This includes bone structure, biomechanics of stress applied to bone, bone remodeling, risk factors for stress fracture, and general principles of imaging and treatment of stress fractures. Cortical bone and trabecular bone have a contrasting macrostructure, which leads to differing resistances to externally applied forces. The variable and often confusing imaging appearance of stress fractures of the foot and ankle can largely be attributed to the different imaging appearance of bony remodeling of trabecular and cortical bone. Risk factors for stress fracture can be divided into intrinsic and extrinsic factors. Stress fractures subject to compressive forces are considered low-risk and are treated with activity modification and correction of any modifiable risk factors. Stress fractures subject to tensile forces and/or located in regions of decreased vascularity are considered high risk, with additional treatment options including restricted weight-bearing or surgery.

Postoperative Foot and Ankle MR Imaging

MR imaging has an important role in the evaluation of the postoperative foot and ankle. In this article, a variety of operative techniques and postoperative findings in the foot and ankle are described, including tendon and ligament reconstruction, as well as the treatment of tarsal coalition and Morton neuroma. The role of MR imaging in the assessment of complications of foot and ankle surgery is also detailed.

Fatigue Fracture of the Calcaneus: From Early Diagnosis to Treatment: A Case Report of a Triathlon Athlete

Stress fractures are frequently underdiagnosed and undertreated despite being common in sports. Early diagnosis is crucial; therefore, a high index of clinical suspicion is required. Complementary examinations are essential for diagnosis and follow-up. The authors report a clinical case of a young adult triathlon athlete referring mechanical pain in the rear left foot, with 2 weeks' progression. An earlier increase in daily training intensity was recorded. Complementary examinations confirmed a calcaneal fatigue fracture. Immobilization and no weight bearing were introduced for an initial period of 4 weeks, and the rehabilitation process was started. Progressive weight bearing was introduced between fourth and eighth weeks. Sports activity started at the 12th week. Boundaries to sports activity were eliminated by the 24th week, without pain or functional limitation. Repetitive overload to the heel and intense axial weight bearing in association to repetitive concentric/eccentric gastrocnemius contraction are related to calcaneal stress fracture, the second most common stress fracture in the foot. Calcaneal stress fractures can be adequately treated with activity modification, without casting or surgical intervention. When in the presence of bilateral stress fractures, metabolic and nutritional issues must be considered. The case report highlights the importance of sports medicine examination for detecting intrinsic and extrinsic fatigue fracture risk factors.

Ultrasound-Diagnosed Tibia Stress Fracture: A Case Report

Stress fractures are a frequent cause of lower extremity pain in athletes, and especially in runners. Plain imaging has a low sensitivity. Magnetic resonance imaging (MRI) or bone scan scintigraphy is the criterion standard, but expensive. We present the case of a young female distance runner with left shin pain. Plain radiography was unremarkable. Ultrasound showed focal hyperechoic elevation of the periosteum with irregularity over the distal tibia and increased flow on Doppler. These findings were consistent with a distal tibia stress fracture and confirmed by MRI. Examination of our case will highlight the utility of considering an ultrasound for diagnosis of tibial stress fracture.

The Pathophysiology of Primary Hip Osteoarthritis may Originate from Bone Alterations

Objectives:

The aim of this study was to investigate whether bone alterations detected by hip magnetic resonance imaging (MRI) were associated with subsequent primary hip OA.

Methods:

We enrolled 7 patients with hip joint pain from their first visit, at which hip joints were classified as grade 0 or I on the Kellgren-Lawrence grading scale. Plain radiographs and magnetic resonance imaging (MRI) were performed on all cases, and pain was assessed with the Denis pain scale. Average age, height, weight, body mass index, bone mineral density (L1-4), central edge angle, Sharp’s angle, and acetabular hip index were calculated.

Results:

Within two months of the onset of pain, 4 of the 7 cases showed broad bone signal changes, while 3 cases showed local signal changes in the proximal femur on hip MRI. Three to 6 months after the onset of pain, in all patients whose pain was much improved, plain radiographs showed progression to further-stage OA.

Conclusion:

Our findings suggest that bone abnormalities in the proximal femur might be involved in the pathogenesis of primary hip OA.

Joint pain undergoes a transition in accordance with signal changes of bones detected by MRI in hip osteoarthritis

Objectives:

In this study, we aimed to investigate whether joint pain is derived from cartilage or bone alterations.

Methods:

We reviewed 23 hip joints of 21 patients with primary hip osteoarthritis (OA), which were classified into Kellgren–Laurence (KL) grading I to IV. Plain radiographs and magnetic resonance imaging (MRI) were obtained from all of the 23 joints. Two of the 21 patients had bilateral hip OA. Pain was assessed based on the pain scale of Denis. A Welch t test was performed for age, height, weight, body mass index, bone mineral density, and a Mann–Whitney U test was performed for KL grading.

Results:

Four of 8 hip joints with pain and OA showed broad signal changes detected by MRI. Fourteen hip joints without pain, but with OA did not show broad signal changes by MRI. Collectively, MRI analyses showed that broad signal changes in OA cases without joint pain or with a slight degree of joint pain were not observed, while broad signal changes were observed in OA cases with deteriorated joint pain.

Conclusion:

Our findings suggest that hip joint pain might be associated with bone signal alterations in the hips of OA patients.

Stress fractures of the tibia and medial malleolus

Tibial diaphyseal stress fractures are rare in the general population, but are more frequently seen in the athletic and military communities. The diagnosis of this problem may be problematic and needs to be considered in all athletes and military recruits who present with shin or ankle pain. The female triad in athletes (low-energy availability/disordered eating, amenorrhea, and osteoporosis/osteopenia) should be considered in those women who sustain this injury. Management is usually conservative with a variety of rehabilitation programs suggested, but a pragmatic approach is to manage the patient symptomatically.

Fractures of the distal phalanx and associated soft tissue and osseous abnormalities in 22 horses with ossified sclerotic ungual cartilages diagnosed with magnetic resonance imaging

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.

Occult fractures of the greater tuberosity of the humerus

We studied the highest reported number of patients with occult fracture of the greater tuberosity of the humerus and we analysed why fracture was not diagnosed, shoulder function and prevalence of eventually associated rotator cuff tear (RCT). Twenty-four patients with a missed fracture of the greater tuberosity underwent MR study for a suspect RCT. We evaluated shoulder function and self-assessed comfort with the Constant score (CS) and Simple Shoulder Test (SST). Nine patients showed evidence of cuff tendinosis, 11 of partial (p) RCT (2: subscapularis; 6: supraspinatus and 3: supraspinatus and infraspinatus). All patients with pRCT were older than 40. Initially, the mean CS and SST were 54% and 5/12; at follow-up, values increased to 36% and 5 points. MR should be performed in patients apparently negative for fracture but with painful shoulders and decreased ROM. Of our patients, 45.8% had pRCT; nevertheless function recovery was verified in 16 weeks.

Significance of radiographic abnormalities in patients with tibial stress injuries: correlation with magnetic resonance imaging

OBJECTIVE

The objective was to correlate radiographic findings with magnetic resonance imaging (MRI) findings in patients with suspected tibial stress injuries in order to determine the significance of radiographic signs of stress injury in these individuals.

PATIENTS AND METHODS

The study group consisted of 80 patients with suspected tibial stress injuries who underwent a radiographic and MR examination of the tibia. Nineteen patients had bilateral involvement. Thus, a total of 99 tibias were evaluated. All radiographs and MR examinations were retrospectively reviewed, 1 month apart, in consensus by two musculoskeletal radiologists. The radiographs were reviewed without knowledge of the site of the clinical symptoms. Fisher's exact tests were used to determine the association between a positive radiograph and the presence of various MRI signs of a high-grade stress injury.

RESULTS

There was a strong association between the presence of periosteal reaction on radiographs at the site of the clinical symptoms and a Fredericson grade 4 stress injury on MRI.

CONCLUSIONS

The presence of periosteal reaction on radiographs at the site of clinical symptoms is predictive of a high-grade stress injury by MRI criteria.

Stress fractures in athletes

A stress fracture is a partial or complete bone fracture that results from repeated application of stress lower than the stress required to fracture the bone in a single loading. Otherwise healthy athletes, especially runners, sustain stress injuries or fractures. Prevention or early intervention is the preferable treatment. However, it is difficult to predict injury because runners vary with regard to biomechanical predisposition, training methods, and other factors such as diet, muscle strength, and flexibility. Stress fractures account for 0.7% to 20% of all sports medicine clinic injuries. Track-and-field athletes have the highest incidence of stress fractures compared with other athletes. Stress fractures of the tibia, metatarsals, and fibula are the most frequently reported sites. The sites of stress fractures vary from sport to sport (eg, among track athletes, stress fractures of the navicular, tibia, and metatarsal are common; in distance runners, it is the tibia and fibula; in dancers, the metatarsals). In the military, the calcaneus and metatarsals were the most commonly cited injuries, especially in new recruits, owing to the sudden increase in running and marching without adequate preparation. However, newer studies from the military show the incidence and distribution of stress fractures to be similar to those found in sports clinics. Fractures of the upper extremities are relatively rare, although most studies have focused only on lower-extremity injuries. The ulna is the upper-extremity bone injured most frequently. Imaging plays a key role in the diagnosis and management of stress injuries. Plain radiography is useful when positive, but generally has low sensitivity. Radionuclide bone scanning is highly sensitive, but lacks specificity and the ability to directly visualize fracture lines. In this article, we focus on magnetic resonance imaging, which provides highly sensitive and specific evaluation for bone marrow edema, periosteal reaction as well as detection of subtle fracture lines.

Change of cross-linked telopeptide of type I collagen (ICTP) and other bone resorption markers in patients with bone fragility fractures

BACKGROUND

The serum concentration of cross-linked telopeptide of type I collagen (ICTP) has been reported to be a useful marker and for both diagnosis and monitoring of bone metastasis. This study was performed to clarify the changes in various bone turnover markers, including ICTP, after bone fragility fracture.

METHODS

Seventy-six bone fragility fracture patients (14 men and 62 postmenopausal women; mean age, 77.0 years) were evaluated for bone resorption markers, including serum ICTP. We measured urinary N-terminal telopeptides of type I collagen (NTX) several times after fracture. Furthermore, serum ICTP, serum NTX, urinary deoxypyridinoline (DPD), and urinary C-telopeptide-cross-linked type I collagen (CTX) were measured at the times of both minimum and maximum urinary NTX.

RESULTS

Urinary NTX was increased significantly from 86.4 +/- 57.9 to 214.3 +/- 137.2 nmol BCE/mmol Cr following fracture. Serum ICTP showed a similar significant increase from 7.6 +/- 4.7 to 10.4 +/- 5.5 ng/ml in bone fragility fracture patients. Furthermore, other markers also showed similar increases. The level of increase in urinary NTX (148.0%) was especially high compared with other bone resorption markers. On the other hand, the level of increase in serum ICTP (36.8%) was similar to that in serum NTX (39.8%). Serum ICTP levels were significantly correlated with other bone resorption markers, with an especially strong correlation between serum ICTP and serum NTX (r = 0.647, P < 0.001). The percentage of cases in which ICTP exceeded the cutoff value for suspected bone metastasis in postmenopausal women was 73.6%.

CONCLUSIONS

The value of ICTP increases with bone fragility fracture and is correlated with other bone resorption markers, and ICTP obviously exceeded the reference value as compared with other bone resorption markers.

Radiographic evaluation of vertebral fractures in osteoporotic patients

Vertebral fractures, are a serious clinical problem for elderly osteoporotic patients, have been increasingly recognized and are now common. On the assumption that it is difficult to diagnose osteoporotic vertebral fractures on plain radiographs, we studied 78 consecutive patients aged over 50 years with severe back pain with or without minor trauma. All patients had been admitted to our department and had undergone radiographic examinations including plain radiography, magnetic resonance imaging (MRI) and bone scintigraphy. Surprisingly, 74 of the patients (94.9%) with severe back pain had vertebral fractures. Low intensity on T1-weighted MRI indicated that the severe back pain was a symptom of vertebral fracture. The patients were divided into two groups: those with total, and those with partial T1-weighted hypointensity of the vertebral body on MRI. Thirty-five of the vertebral fractures (47.3%) were not detectable on plain radiographs, and patients without trauma showed vertebral deformity more frequently than those with trauma. The patients were treated conservatively with bed rest until the severe back pain had subsided, after which they were evaluated clinically. The average period of bed rest was 22.3 days, which did not differ significantly in relation to the occurrence of trauma, the extent of the signal change in the vertebral body on MRI or the presence of vertebral deformity. Even without vertebral deformity or trauma, vertebral fractures required long periods of bed rest for pain relief and entailed serious clinical problems.

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.

High-Resolution CT Grading of Tibial Stress Reactions in Distance Runners

OBJECTIVE

The purpose of this study was twofold: to determine whether asymptomatic distance runners exhibit cortical tibial abnormalities on CT and to determine the diagnostic accuracy of CT in athletes with medial tibial stress syndrome.

MATERIALS AND METHODS

A cross-sectional study with high-resolution CT of both tibiae was performed on 41 subjects: 20 asymptomatic distance runners, 11 distance runners with unilateral or bilateral pain due to medial tibial stress syndrome (14 painful tibiae), and 10 volunteers not involved in a sport. The group was composed of 13 women and 28 men, ranging in age from 18 to 26 years. A total of 82 tibiae, 14 painful and 68 painless, were evaluated. On the basis of CT findings, tibiae were classified in three groups, and correlation between CT classification and symptoms was made.

RESULTS

Among distance runners, the presence of CT abnormalities was found in 14 (100%) of 14 painful tibiae in patients with medial tibial stress syndrome and in 8 (16.6%) of 48 painless tibiae. The difference was statistically significant (p < 0.001, Fisher's exact test). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CT in diagnosing medial tibial stress syndrome were 100%, 88.2%, 63.6%, 100%, and 90.2%, respectively.

CONCLUSION

High-resolution CT has high diagnostic accuracy in depicting medial tibial stress syndrome. Cortical abnormalities can also be seen in some asymptomatic distance runners.

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.

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.

Differential diagnosis of a femoral neck/head stress fracture

STUDY DESIGN

Resident's case problem.

BACKGROUND

Identifying stress fractures of the hip can be a challenging differential diagnosis. Pain presentation is not always predictable and radiographs may not show the fracture, especially during its early stages. Hip stress fractures left untreated can displace and necessitate open reduction internal fixation or total hip arthroplasty.

DIAGNOSIS

A 70-year-old woman presented to the physical therapy clinic with complaints of right hip pain. She had been evaluated by a physician and radiographs of the hip, which revealed some arthritic changes, were otherwise normal. Upon examination, the physical therapist observed an antalgic gait, a noncapsular pattern of limitation of hip motion, an empty painful end feel at the end range of motion (ROM) for hip abduction, external rotation, and flexion, and extreme tenderness to palpation over the anterior hip region. The therapist suspected a more pernicious problem than osteoarthritis and discussed his suspicion with the physician. The physician subsequently requested an MRI that revealed a femoral neck and head stress fracture that was later confirmed with a bone scan. The patient was provided with a walker for ambulation with a non-weight-bearing status for 6 weeks, after which she returned to physical therapy for progressive weight bearing and strengthening. She was discharged with a relatively pain-free hip and was ambulating with a cane. A 2-month follow-up examination revealed a pain-free hip and a return to all premorbid activities, including ambulation without an assistive device.

DISCUSSION

The presence of a normal radiograph of the hip should not be considered conclusive in ruling out a stress fracture in the hip region. The current case demonstrates how careful evaluation can reveal occult pathologies and prevent potentially catastrophic morbidity.

Bone stress injuries causing exercise-induced knee pain

BACKGROUND

No comprehensive studies of bone stress injuries in the knee based on magnetic resonance imaging findings have been published.

PURPOSE

Assess the incidence, location, nature, and patterns of bone stress injuries in the knee in military conscripts with exercise-induced knee pain.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

During a period of 70 months, 1330 patients with exercise-induced knee pain underwent magnetic resonance imaging of the knee. A total of 1577 knees were imaged; the images with bone stress injury findings were retrospectively reevaluated with respect to location and type of injury. The person-based incidence of bone stress injuries in the knee was calculated, based on the number of conscripts within the hospital's catchment area.

RESULTS

Of the 1330 patients, 88 (7%) met the inclusion criteria, and 141 bone stress injuries were found in the 110 knees imaged. The incidence of bone stress injuries was 103 per 100 000 person-years. Of the patients, 25% had bilateral bone stress injuries; 28% had 2 solitary bone stress injuries in the same knee simultaneously, all situated in the femoral condyle and tibial plateau. The most common anatomical location for a bone stress injury was the medial tibial plateau (31%), which was also the most typical location for a more advanced injury. After the commencement of military service, a bone stress injury in the medial tibial plateau caused knee pain earlier than did a bone stress injury elsewhere in the knee (P = .014).

CONCLUSION

The incidence of bone stress injuries in the knee with exercise-induced knee pain is relatively high in conscripts. Multiple and bilateral injuries can occur. For accurate diagnosis and to ensure appropriate treatment, magnetic resonance imaging is recommended as a routine imaging method when a physical activity can be regularly associated with the onset of symptoms.

Distinction of Long Bone Stress Fractures from Pathologic Fractures on Cross-Sectional Imaging: How Successful Are We?

OBJECTIVE

The objectives of our study were to define CT and MRI features that distinguish pathologic fractures from stress fractures and to compare the performance of CT and MRI with radiography.

MATERIALS AND METHODS

Two reviewers retrospectively reviewed 45 MR images, 37 CT scans, and 43 radiographs in 59 patients (30 biopsy-proven pathologic fractures and 29 stress fractures followed to resolution). The features observed on MRI were abnormal bone marrow (well-defined, ill-defined); intracortical, periosteal, or muscle T1 or T2 signal; endosteal scalloping; and a soft-tissue mass. The features seen on CT were marrow abnormality and character (well-defined, ill-defined, permeative, moth-eaten), endosteal scalloping, periosteal reaction (benign, aggressive), and a soft-tissue mass. Reviewers rated their confidence for diagnosing a pathologic fracture on a 1-3 scale (< 50%, 50-95%, > 95% sure, respectively) with each technique. Performance of each technique was defined by reviewer accuracy and area under the receiver operating characteristic curve (Az); the frequency with which the MRI and CT features were associated with pathologic and stress fractures was calculated.

RESULTS

For both reviewers, accuracy for differentiating pathologic from stress fractures was highest on MRI (accuracy/Az: reviewer 1, 98%/0.97; reviewer 2, 93%/0.99); CT (reviewer 1, 88%/0.83; reviewer 2, 82%/0.90) was less accurate than radiography (reviewer 1, 94%/0.98; reviewer 2, 88%/0.96). On MRI, pathologic fractures compared with stress fractures exhibited well-defined T1 marrow signal (83% vs 7%, respectively; p < 0.001), endosteal scalloping (58% vs 0%, p < 0.001), muscle signal (83% vs 48%, p = 0.026), and a soft-tissue mass (67% vs 0%, p < 0.001). On CT, pathologic fractures compared with stress fractures exhibited marrow abnormality (84% vs 17%, respectively; p = 0.001), endosteal scalloping (44% vs 0%, p = 0.006), and aggressive periosteal reaction (36% vs 0%, p = 0.04).

CONCLUSION

MRI is useful for distinguishing pathologic from stress fractures, especially after inconclusive radiographic findings. Specifically, pathologic fractures exhibit well-defined T1 marrow alterations, endosteal scalloping, and adjacent soft-tissue abnormalities.

Stress fracture at the junction of the middle and distal third of the ulnar diaphysis in a spinner bowler: a case report and a review of the literature

Stress fractures of the ulnar shaft are uncommon injuries, which have been documented in a variety of sports. The location of the fracture is influenced by the activity and mechanism of injury with which it is associated. The combined traditional approach of clinical history, physical examination, plain radiographs and nuclear scintigraphy for unusual stress fracture may be troublesome. This report is the first to describe a stress fracture at the junction of the middle and distal third of the ulnar diaphysis in a bowler due to chronic torsional stress. We discuss the possible mechanism of injury and describe the diagnostic imaging. A review of the literature is also given and compared with the findings and data of this case.

CT and MR imaging findings in athletes with early tibial stress injuries: comparison with bone scintigraphy findings and emphasis on cortical abnormalities

PURPOSE

To prospectively compare computed tomography (CT), magnetic resonance (MR) imaging, and bone scintigraphy in athletes with clinically suspected early stress injury of tibia.

MATERIALS AND METHODS

Medical ethics committee approval and informed consent were obtained. A total of 42 patients experiencing tibial pain due to early stress injuries were evaluated. Eight patients had bilateral involvement; thus, 50 tibiae were evaluated. All patients underwent initial radiography that was negative for injury. MR imaging, CT, and bone scintigraphy were performed in all patients within 1 month of onset of symptoms. Ten asymptomatic volunteers served as the control group. Location of stress injuries, types of bone alterations, and presence of periosteal and bone marrow edema were evaluated. Sensitivity, specificity, accuracy, and positive and negative predictive values of MR imaging and CT were assessed, as was sensitivity of bone scintigraphy. McNemar test was used to detect statistically significant differences.

RESULTS

Sensitivity of MR imaging, CT, and bone scintigraphy was 88%, 42%, and 74%, respectively. Specificity, accuracy, and positive and negative predictive values were 100%, 90%, 100%, and 62%, respectively, for MR imaging and 100%, 52%, 100%, and 26%, respectively, for CT. Significant difference in detection of early tibial stress injuries was found between MR imaging and both CT and bone scintigraphy (McNemar test; P < .001 and P = .008, respectively).

CONCLUSION

MR imaging is the single best technique in assessment of patients with suspected tibial stress injuries; in some patients with negative MR imaging findings, CT can depict osteopenia, which is the earliest finding of fatigue cortical bone injury.

Imaging the ankle and foot and using magnetic resonance imaging

Magnetic resonance (MR) imaging has improved the possibility of evaluating musculoskeletal structures thus gaining an important role in the diagnosis and treatment of foot and ankle pathologies. In this review, the normal and pathological images of the ankle and foot obtained using MR techniques are presented and discussed. The high soft-tissue contrast resolution and the multiplanar sections of MRI allow the imaging of contiguous tissues where small contrast differences exist, such as ligamentous and tendinous injuries or impingement syndromes. The spatial resolution with high sensitivity for bone signal changes offers an early detection of osseous abnormalities such as stress fractures or osteonecrosis. Here it is specified possibilities and limitations of MRI in the diabetic foot: this technique is superior to nuclear medicine and computed tomography (CT), however it is unable to distinguish between neuro arthropathy and infection.

Distinguishing stress fractures from pathologic fractures: a multimodality approach

Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount.

Regional migratory osteoporosis: a review illustrated by five cases

Regional migratory osteoporosis is an uncommon self-limiting disease characterized by an arthralgia which migrates between the weight-bearing joints of the lower limb. The radiological features of the disease obtained by conventional radiography, CT, MRI and radionuclide scintigraphy are illustrated by means of five case reports. These range from the most common presentation of sequential, proximal to distal spread in the lower limb to the rare intra-articular form, and disease involving the axial skeleton is also recognized. Clinical and radiographical features often overlap with those of diseases such as transient osteoporosis of the hip and transient bone marrow oedema syndrome, which is reflected in confusing terminology. Histological sampling is usually unnecessary; the radiological features are characteristic and the histological findings are not specific. Regional migratory osteoporosis is associated with systemic osteoporosis. This association is probably under-recognized, and has implications for the pathophysiology of the disease and for treatment.

Sonographic findings in stress fractures of the lower limb: preliminary findings

Stress fractures are common injuries frequently overlooked on first radiographs, especially in the early course. The gold standard for accurate diagnosis is MRI and scintigraphy. We report six cases of stress fractures of the lower limb diagnosed with sonography and describe typical sonographic features.

Imaging of the navicular

This article presented a rational approach to imaging of navicular pathology. The indications, techniques, and limitations of conventional radiographic imaging were discussed. In addition, the role of advanced imaging techniques, including MRI, CT, and NMI, in the diagnosis of navicular pathology was presented. By appropriately combining plain radiographic imaging with advanced imaging modalities, an accurate diagnosis is typically obtained.

Bone marrow edema syndrome of the foot: one year follow-up with MR imaging

OBJECTIVE

To describe the MR findings of bone marrow edema syndrome (BMES) of the foot and its evolution at 1 year follow-up.

DESIGN AND PATIENTS

Twenty-five of 32 patients with disabling foot and ankle pain unrelated to trauma diagnosed as BMES when MR imaging demonstrated a bone marrow edema pattern in one or more bones without any radiological or underlying clinical cause, were re-evaluated by MR imaging 1 year later.

RESULTS

On the initial MR examinations an average of 4.7 individual bones were involved by bone marrow edema. Soft tissue edema was present in every patient and joint effusion in 10 patients. MR imaging at 1 year showed resolution of bone edema in 18 patients (72%), partial improvement in five (20%) and no improvement in two (8%). Six patients (24%) developed similar symptoms in the other foot during follow-up. Ten of 17 available plain radiographs showed some loss of radiodensity. Further bone marrow edema developed in bones of the same foot that were initially normal, or in uninvolved distant bone marrow areas in the same affected bone, in six of seven patients on follow-up MR imaging.

CONCLUSIONS

The evolution of the MR findings of BMES of the foot is to complete resolution or partial improvement at 1 year in the majority of cases. Migration to the other foot occurs in up to a quarter of patients.

Bone stress injuries of the lower extremity: a review

Bone stress injuries can cause long-lasting damage, especially in young athletes and military conscripts, if not diagnosed and treated properly. Diagnosis has been traditionally based on clinical, radiographic and scintigraphic examinations, but MRI has become increasingly important. High resolution MRI is particularly valuable for the grading of bone stress injuries. The clinician should be aware of the wide range of bone stress injuries and available diagnostic methods. Early diagnosis is the prerequisite for avoiding long-lasting complications. Most bone stress injuries heal with closed treatment, but surgery is necessary in some cases. They heal well if the diagnosis is not delayed and the treatment adequate.

MR imaging of fatigue stress injuries to bones: intra- and interobserver agreement

The aim of this study was to determine the validity of MR imaging (MRI) in the assessment of stress-related injuries to bone.MR images of 50 military recruits (8 females and 42 males; 18-27 (mean 20) years of age) were retrospectively evaluated twice for stress injuries to bone by 4 radiologists (2 musculoskeletal radiologists, 2 radiology residents). Coronal T1-weighed (T1W) and STIR images, as well as axial and coronal T2-weighted (T2W) fat-suppressed images were taken using a 1.0T scanner. Rates for sensitivity, specificity, and accuracy of MRI of the stress-related injuries were calculated. Intraobserver and interobserver agreement was determined with kappa statistics. Rates for MRI sensitivity were 27-96%, for specificity 65-100%, and for diagnostic accuracy 58-97%. Lowest rates were seen when reading T1W images and highest when reading STIR images. Readers showed moderate to excellent intraobserver agreement (kappa 0.75-0.95). Interobserver agreement was fair to excellent (kappa 0.41-0.91), and the lowest values were seen in the interpretation of T1W images. Normal findings could be differentiated from various grades of stress injury to bone.MRI is a valid means of revealing the presence of stress injuries to bone and their staging. Observer agreement is good to excellent when using T2W images and STIR images, while T1W images are of lesser value.

Comparison of scintigraphy and magnetic resonance imaging for stress injuries of bone

OBJECTIVE

To compare findings of radiography, scintigraphy, and magnetic resonance imaging (MRI) in stress injuries of bone and evaluate changes of these findings with time correlated with clinical symptoms.

DESIGN

Prospective study.

SETTING

A primary care hospital outpatient orthopedic clinic.

PATIENTS

All 31 patients with stress injuries of bone who visited our clinic from July 1996 to June 2000.

INTERVENTION

Radiography, scintigraphy, MRI, and clinical examinations were performed on the same day or at least within 1 week of each other, and the findings were compared. If symptoms of stress injury of bone continued, these examinations were repeated at intervals of 2 months until symptoms disappeared. These radiologic findings were assessed by an independent radiologist who was blinded to the clinical symptoms of the patients.

MAIN OUTCOME MEASURES

Correlation accuracy of MRI and scintigraphy findings with clinical symptoms.

RESULTS

Even with negative initial radiographic findings, all initial scintigraphy and MRI indicated stress injury of bone. There were no patients with positive/negative examinations. Grade of scintigraphy and MRI were closely correlated, and these findings also correlated with the degree of clinical symptoms. Compared with scintigraphy, MRI showed more diagnostic information, such as fracture line and periosteal edema. Areas of increased activity in scintigraphy were consistent with the grades of MRI, especially high signal intensity areas of STIR (short tau inversion recovery) image.

CONCLUSIONS

From these observations, MRI is less invasive, provides more information than scintigraphy, and is recommended for initial diagnosis and assessment stages of stress injury of bone.

Bilateral proximal third fibular stress fractures in an adolescent female track athlete

Proximal fibular stress fracture is an uncommon injury in athletes but has been frequently reported in the military population. Although the true incidence is unknown and its pathophysiology is not completely understood, proximal fibular stress fracture is believed to be a rare injury and awareness of it will help clinicians make the proper diagnosis and provide appropriate treatment.

Pathological fracture of the femoral neck as the first manifestation of osteonecrosis of the femoral head

We describe two cases of pathological fracture of the femoral neck occurring as the first manifestation of osteonecrosis of the femoral head (ONFH). No abnormal findings suggestive of ONFH were identified on the radiographs for either of the patients, and the fractures occurred like spontaneous fractures without any trauma or unusually increased activity. The patients' medical history, age, and good bone quality suggested ONFH as a possible underlying cause of the fractures. If we had not suspected ONFH as a predisposing condition, these minimally displaced fractures might have been fixed internally with multiple pins, and this would have led to nonunion or collapse of the femoral head. To avoid inappropriate treatment, ONFH should be considered as a predisposing factor in pathological fractures of the femoral neck.

Low-risk stress fractures

Stress fractures can occur in almost any bone in the body, with the lower extremity weightbearing bones, especially the tibia, tarsals, and metatarsals, being affected most frequently. Although the cause of these fractures is multifactoral, repetitive physical forces without adequate rest are the primary culprits. Stress fractures may be broadly classified as low-risk or high-risk injuries. Low-risk stress fractures, the topic of this review article, can be diagnosed through a thorough history, physical examination, and radiographs. Nuclear scintigraphy is occasionally necessary for confirmation, especially for fractures of the spine and pelvis. When diagnosed early and treated with restriction of activity, low-risk stress fractures have a favorable prognosis.