Avulsion fractures and chronic avulsion injuries of the knee: role of MR imaging

Avulsion fractures and chronic avulsion injuries of the knee are common lesions in sports-related trauma, especially among adolescents. Magnetic resonance imaging may prove useful in detecting and characterizing such lesions, and has several advantages with regard to other imaging modalities. We review, illustrate, and discuss the MR imaging features of some of the more frequent avulsion fractures and chronic avulsion injuries of the knee, including avulsion fractures of the cruciate ligaments, avulsion fractures of lateral and medial stabilizers, avulsion fractures and chronic avulsion injuries of the extensor mechanism, and avulsive cortical irregularities of the distal femur. The role of MR imaging in evaluating such lesions is emphasized.     

Advanced imaging of glenohumeral instability: the role of MRI and MDCT in providing what clinicians need to know

The inherently unstable anatomy of glenohumeral (GH) joint predisposes it to shoulder dislocation. Shoulder dislocation can occur either due to acute trauma or due to chronic microtraumas in the setting of underlying morphological abnormality. A plain radiograph is the initial imaging modality for diagnosis and management of shoulder dislocation and its associated osseous abnormalities such as Hill-Sachs deformity or osseous Bankart lesion. However, advanced imaging techniques such as multidetector CT (MDCT) with three-dimensional (3D) volume rendering and MRI can be helpful in further characterization of osseous abnormalities and detection of associated soft tissue injuries, respectively. These additional findings may be useful for optimal surgical repair for GH joint stabilization. In this pictorial essay, we present the clinically relevant osseous and soft tissue pathologies in various types of shoulder dislocation, with emphasis on pathologies that can be demonstrated using advanced imaging examinations. Discussed pathologies include glenoid fractures, labral tears, Bankart lesion, Hill-Sachs defect, Perthes lesion, anterior labral posterior sleeve avulsion (ALPSA), glenolabral articular disruption (GLAD), humeral avulsion of the glenohumeral ligament (HAGL), Kim lesion, and other associated soft tissue and nerve injuries.     

Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging.

Bone scintigraphy is used to detect radiographically silent fractures. Magnetic resonance imaging (MRI) is currently used to screen knee injuries for cartilage and ligament damage. MRI also delineates bone marrow and fractures. We investigated the bone scintigraphic findings in patients who had subchondral bone injuries demonstrated on MRI. Thirteen patients underwent MRI, three-phase bone scintigraphy with SPECT, and arthroscopic surgery after sustaining acute traumatic hemarthrosis of a knee. They all had clinically unsuspected subchondral bone injuries demonstrated on MRI with normal radiographs and normal overlying articular cartilage at arthroscopy, consistent with occult fractures. All showed focal bone repair on scintigraphy. Two of the 13 patients showed additional bone injuries only on bone scan. Two other patients scintigraphically showed focal bone repair at the medial femoral condyle due to avulsion of the medial collateral ligament. SPECT was easier to interpret than multi-view planar imaging. Bone scintigraphy confirms subchondral fractures demonstrated on MRI but also demonstrates ligament avulsion injuries and additional more subtle bone injuries.     

Osseous and myotendinous injuries about the knee

Osseous injuries may be articular, extra-articular, or physeal, and may be related to direct trauma, avulsion forces, or chronic microtrauma. Muscle and tendon injuries about the knee may occur alone or in association with more significant osseous and ligament injuries. Radiographs or computed radiography images remain an important screening technique for patients who have suspected knee injuries. After initial radiographs, MR imaging has become the most common modality for detection and complete evaluation of osseous and soft-tissue injuries about the knee when those radiographs and other techniques do not demonstrate clearly the type and extent of injuries. This article focuses on the usefulness of MR imaging in the detection, classification, and management of bone, muscle, and tendon injuries of the knee.     

Avulsion injuries of the pelvis

Pelvic avulsion injuries occur in both the skeletally immature and adult patient populations. Avulsion injuries are most common in the adolescent age group and usually present as an avulsion of the unfused apophysis at the level of tendon attachment resulting from violent muscular contraction during an athletic endeavor. Acute apophyseal avulsion injuries are usually easily detected and adequately imaged with radiographs, but occasionally advanced imaging such as magnetic resonance imaging or computed tomography is required to detect and fully delineate the extent of injury. Chronic injuries can mimic a more aggressive lesion, but familiarity with the location of various tendon attachment sites on the osseous pelvis can help avoid this pitfall. Traumatic avulsion injuries can also occur in the skeletally mature pelvis; however, in the adult, the presence of a pelvic avulsion fracture in the absence of trauma should be considered a pathological lesion until proven otherwise. This article discusses the clinical and imaging findings of apophyseal avulsion injuries in the adolescent athlete, followed by a discussion of specific pelvis avulsion injuries that occur in the adult population.     

MRI of anterior cruciate ligament injuries and associated findings in the pediatric knee: changes with skeletal maturation

OBJECTIVE: The objective of our study was to evaluate the MRI characteristics of anterior cruciate ligament (ACL) injuries and associated findings relative to skeletal maturity. We also contrast the frequency of findings in this younger population to adult data. MATERIALS AND METHODS: Eighty-two consecutive knees with an MRI report diagnosis of ACL injury (partial tear, sprain, or complete tear) or tibial spine avulsion fracture imaged over 4 years were retrospectively reviewed. Patients were grouped by degree of skeletal maturity as determined from the MR images. The examinations were reviewed for the type of ACL injury, secondary imaging findings, and associated knee injuries. Findings were correlated to skeletal maturity, and frequencies were compared with adult data. RESULTS: ACL injuries were more common in boys in the skeletally immature group, but more common in girls in the skeletally mature group (p = 0.03). Tibial spine avulsion fractures were most common in skeletally immature patients (p < 0.01), whereas complete tears of the ACL were most common in skeletally mature patients. Associated injuries were less common in the skeletally immature group, but this trend did not reach statistical significance. Most secondary signs of ACL injuries occurred at similar rates in all groups with frequencies similar to those reported in adults. CONCLUSION: ACL injuries in skeletally immature patients are seen more often in boys. Tibial avulsion fractures and partial tears are more common in younger, less rigid skeletons that may absorb the forces of trauma. As children mature, complete ACL tears and associated injuries occur in frequencies approaching those patterns seen in adults. Similarly, skeletally mature girls are affected more often than mature boys.     

Avulsion of the common hamstring tendon origin in an active duty airman

Hamstring injuries are common in active athletic populations, such as military service members. Ruptures of the hamstring origin from the ischial tuberosity are rare injuries and missed if not considered in the differential diagnosis of ischial pain. Unlike other hamstring injuries, complete hamstring avulsions must be treated surgically. Results of untreated hamstring avulsions are poor. The purpose of this article is to describe the case of an active duty airman who presented for an unrelated complaint and was discovered to have a 5-week-old hamstring avulsion. Surgical repair of the hamstring avulsion 6 weeks after injury yielded an excellent result and return to full duty. Hamstring avulsions recognized early by history and physical examination and diagnostic imaging permits early and effective treatment. Early surgical repair of the tendon to bone can result in return to full duty.     

Bone stress injuries

Bone stress injuries are due to cyclical overuse of the bone. They are relatively common in athletes and military recruits but also among otherwise healthy people who have recently started new or intensive physical activity. Diagnosis of bone stress injuries is based on the patient's history of increased physical activity and on imaging findings. The general symptom of a bone stress injury is stress-related pain. Bone stress injuries are difficult to diagnose based only on a clinical examination because the clinical symptoms may vary depending on the phase of the pathophysiological spectrum in the bone stress injury. Imaging studies are needed to ensure an early and exact diagnosis, because if the diagnosis is not delayed most bone stress injuries heal well without complications.     

When Groin Pain Is More Than ‘Just a Strain’

Most groin pain results from brief musculotendinous injuries, but not all groin pain signifies simply a pulled muscle. The pain can stem from one or more musculoskeletal or nonmusculoskeletal origins, such as avulsion fracture, osteitis pubis, or hernia. While acute causes are often readily identified, chronic groin pain can present a diagnostic challenge. Paying close attention to the history can help identify acute causes such as strains and avulsion fractures; determining the location and nature of the pain can also help with diagnosis. Conservative treatment is often effective for treatment of acute injuries such as strains and avulsion fractures.     

Wrist Trauma: More Than Bones

Acute and subacute wrist trauma predominantly consist of fractures of the distal radius in elderly patients and most frequently carpal fractures (scaphoid, followed by triquetrum and hamatum) and avulsion fractures of the ulnar styloid in younger patients, especially in sports-related injuries but also in work activities. The initial radiographs may miss the fractures and result when untreated in complications as nonunion, osteonecrosis, and degenerative osteoarthritis.Fractures of the distal radius and of the scaphoid may be associated with ligament injuries, most frequently the scapholunate complex, which are often overlooked at the emergency department. Patients without osseous injuries may present intrinsic and extrinsic ligament tears that may lead to carpal instability when they are clinically and/or radiologically missed.Therefore, in acute and subacute setting, computed tomography may be helpful for the detection of subtle fractures, and magnetic resonance imaging, for the early diagnosis of occult fractures and ligament injuries.     

Magnetic resonance imaging findings of chronic lateral ankle instability

The ankle inversion injury is one of the most common types of injury that is encountered in athletes and active individuals. There are a wide variety of acute injuries associated with ankle inversion, including peroneal tendon tears, osteochondritis dessicans of the talus, anterior talofibular ligament avulsion, peroneal retinaculum avulsion, and calcaneofibular ligament tears. Chronic sequelae include impingement, posttraumatic degenerative arthritis, and an attenuated peroneal retinaculum. Most inversion injuries to the ankle have multiple associated injuries and isolated ligament injuries are uncommon. Chronically, the injured ankle usually demonstrates the injuries found at the time of the initial injury. Subsequently, there is a high frequency of these injuries in patients evaluated for symptoms of chronic lateral ankle instability. A high index of suspicion for the specific types of injuries associated with ankle inversions may result in a higher rate of injury detection and more expeditious and accurate diagnoses. Given the persistence of these injuries seen in patients with chronic posterolateral instability, injury patterns of ankle inversion are important to recognize even in the absence of acute trauma. We review the various types of injuries with their associated magnetic resonance (MR) imaging characteristics seen in patients with chronic lateral ankle instability.     

Bone abnormalities of the knee: prevalence and significance at MR imaging

Focal abnormal signal intensity within the distal femoral condyles or proximal tibial plateaus is frequently seen on T1- or intermediate-weighted magnetic resonance (MR) images of the knee. To characterize the prevalence and significance of these findings better, a retrospective study of MR imaging of the knee, performed on the first 434 consecutive patients at a primarily outpatient community MR imaging center, was undertaken. A signal intensity loss demonstrated on images with a short echo time (20 or 25 msec) was divided into three types based on morphologic criteria. A type 1 finding was a diffuse, often reticulated signal intensity loss in the metaphyseal and epiphyseal regions of bone. A type 2 loss was associated with an interruption in the smooth, black cortical line. A type 3 finding was a profound signal intensity loss primarily restricted to the immediate subcortical region. Seventeen percent of all cases revealed a type 1 or 2 loss that may have been compatible with acute bone injuries. These bone lesions were frequently associated with tears of the anterior cruciate ligament and contralateral collateral ligament, but infrequently these lesions were detected with plain radiography and arthroscopy. When associated with a weight-bearing cortex, bone injuries detected with MR imaging may explain clinical symptoms of pain on weight bearing, and type 1 injuries may represent regions of bone at increased risk for the subsequent development of insufficiency fractures if the bone is not adequately protected during trabecular healing.     

Magnetic resonance imaging of ligamentous injury of the cervical spine

This study is a retrospective review of 43 patients with acute cervical spine trauma, including 97 ligamentous injuries of various types diagnosed by magnetic resonance imaging (MRI). Three general patterns of ligamentous injury were observed, including: complete rupture; partial avulsion or attenuation of the ligament, without frank rupture; and combined osseous and ligamentous fragment. Overall, proton density and T2^*-weighted gradient-echo or T2-weighted spinecho images in the sagittal plane provided the best evaluation of the spinal ligaments. Axial proton density and T2^*-weighted gradient images were useful only in assessment of the trasverse portion of the cruciate ligament. By providing direct visualization of the spinal ligaments, MRI demonstrated multiple case of ligamentous injury that were greater than expected or unexpected from plain radiographic and computed tomographic findings. Surgical proof was obtained for 11 patients with 14 ligamentous injuries that were diagnosed by MRI independently. There were two false-positive MRI diagnoses for posterior longitudinal ligament rupture, but no false-negatives among these 11 patients. This study indicates that MRI allows accurate diagnosis of cervical spine ligamentous injuries that are otherwise only inferred by the mechanism of injury and resulting spinal alignment.     

隐性骨与软骨损伤的MRI诊断

目的探讨隐性骨与软骨损伤的MRI特点,分析骨挫伤、隐性骨折和关节软骨损伤间的关系。方法回顾性分析了101例隐性骨与软骨损伤,其中骨挫伤70例,隐性骨折13例,关节软骨损伤18例。观察病变的MRI特点、分布,检出骨挫伤的序列敏感性。结果T1WI,STIR或PDWI(f/s)检出骨挫伤的敏感性为95.7%及100%。骨挫伤病变在关节主要分布于骨骼的边缘,脊椎主要分布于椎体上缘终板下。隐性骨折骨折线走行方向不定,平均宽度为1.8 mm,邻近区域的骨挫伤是其重要的间接征象。关节软骨损伤MRI表现为关节软骨变薄、断裂或缺损,软骨下骨挫伤出现率为100%。结论隐性骨折和关节软骨损伤均合并有骨挫伤,MRI是诊断隐性骨与软骨损伤的敏感方法。     

Adolescent hamstring avulsions that simulate tumors

Hamstring injuries are common in athletes. Most of these injuries are diagnosed clinically and managed conservatively. Some patients, such as those with atypical clinical presentations or persistent pain, may be referred for imaging evaluation. In this subacute setting, studies obtained may have confusing features, and fractures may be mistaken for neoplasms. Hamstring avulsions, as seen on plain radiographs and conventional tomography, can have an aggressive appearance owing to callus and postfracture osteolysis. Although computed tomography is not usually necessary, it is very helpful in the subacute setting, identifying the healing avulsed apophysis. Familiarity with the appearance of ischial avulsions over time and with different modalities facilitates accurate characterization of hamstring injuries. We present our experience with six ischial avulsion fractures referred to us as tumors.     

Trauma to the foot

Minor trauma to the foot may cause stress fracture, avulsion fracture or ligamentous and tendon injury. Plain radiographs are frequently normal. Radionuclide bone scan is a sensitive detector of early bone injury. A stress fracture may develop focal uptake or diffuse uptake throughout the bone involved. MR imaging is the most sensitive means of evaluating injury to the soft tissues. Acute edema, partial tear, complete tear, and chronic tendinitis have distinct features on T1- and T2-weighted images. Major trauma occurs most commonly as a result of falls from heights and from motor-vehicle accidents. Plain films are useful in the initial evaluation of the extent of trauma. CT is particularly useful in evaluating calcaneal fractures that involve the subtalar joint. Both MR imaging and CT scans are useful in detecting injured or entrapped tendons associated with fracture-dislocations.     

Basic principles of nuclear medicine techniques for detection and evaluation of trauma and sports medicine injuries

Nuclear medicine skeletal imaging is a very sensitive technique for evaluating bone and muscle abnormalities because it can detect minor changes in metabolism and blood flow. The specificity of bone imaging, however, depends on the ability of the nuclear medicine physician to make a differential diagnosis. To aid in making a specific diagnosis, this article describes the various patterns of abnormality in stress fractures, tibial stress syndrome (shin splints), compartment syndrome, enthesopathy, and traumatic fractures. The characteristic scintigraphic appearance of joint injuries, muscle injuries (rhabdomyolysis), and radionuclide arthrography is discussed and the way the scan patterns change with time in these various disorders is described. A brief summary of the basic anatomy and physiology of bone and muscle in normal and injured tissue is presented and the basic mechanisms which cause the various abnormal scan patterns is postulated. In addition, a staging system for stress fractures is presented to help direct the referring physician toward the proper management of the injured patient. In most cases, nuclear medicine skeletal imaging can be used to differentiate between acute muscle injury, tibial stress syndrome, skeletal injury (periosteal reaction, stress fracture, and traumatic fracture) or an abnormality that is entirely associated with the joint or connective tissue. This differential diagnosis is easier if the nuclear medicine procedure is performed within a few days after the onset of injury.     

Bone marrow edema in sports: general concepts

This paper will discuss the value of medical imaging in the detection and follow-up of bone marrow edema (BME), resulting from acute and chronic trauma in sports. MR imaging is the only imaging technique that allows direct evaluation of bone marrow edema in sports medicine. The use of fat suppressed T2-weighted or STIR images is particularly appropriate to detect bone marrow edema. The extent of bone marrow edema reflects the biomechanics of trauma. Compressive forces between two bony structures will result in extensive areas of bone marrow edema, whereas distraction forces provoke more subtle areas of bone marrow edema at the insertion of supporting structures of joints. In most clinical situations, a combination of compression and distraction forces is present, causing a complex pattern of bone marrow edema. A meticulous pattern approach of the distribution of these bone marrow changes around a joint can reveal in most instances the underlying mechanism of trauma. This may be helpful to analyze which joint supporting structures may be at risk. In the acute setting, plain radiography and CT scan may have an additional role in the detection of small avulsion fractures occurring at the site of minor areas of bone marrow edema. The clinical significance and natural history of bone marrow edema is still a matter of debate.     

颌面部骨折并颅颈交界区损伤的CT诊断

目的 探讨颌面部骨折合并颅颈交界区损伤的影像学特点及多层螺旋CT诊断。方法 收集10例颌面部外伤合并颅颈交界区损伤的螺旋CT重建扫描资料，比较常用影像学检查手段的诊断价值。结果 上、下颌骨双骨折并颧弓骨折者5例，下颌骨骨折5例。其中3例合并颞颌关节脱位，3例合并有轻、中度颅脑损伤。合并颅颈交界区损伤有：枕颈脱位2例，枕骨髁撕脱骨折2例，寰枢椎旋转性半脱位6例，结论 颌面部外伤骨折合并上颈椎损伤多为韧带型损伤，影像学特点为小片的撕脱性骨折及枕颈半脱位、寰枢椎旋转性半脱位；多层螺旋CT重建技术是诊断本病的最佳方式；提高对本病的警惕，重视颅颈交界区解剖标志间关系的画线测量是防止漏诊的关键。