Knee Imaging Following Anterior Cruciate Ligament Reconstruction: The Surgeon's and Radiologist's Perspectives.

Anterior cruciate ligament (ACL) tears are common injuries that if left untreated can result in chronic instability, cartilage damage, meniscal tears, and ligamentous injuries, eventually leading to early osteoarthritis. ACL reconstruction surgeries are therefore increasingly being performed. Despite the fact that most patients achieve excellent postoperative results, patients can present with recurrent instability and pain. These patients often undergo imaging with radiographs, magnetic resonance imaging, and/or computed tomography. An understanding of the imaging appearance of the normal ACL reconstruction and common causes of failure is therefore essential for the interpreting radiologist. This article reviews surgical techniques for ACL reconstruction, highlighting recent technical advances, the normal imaging appearance after ACL reconstruction, etiologies for reconstruction failure, and the diagnosis of these with the aid of imaging.

Lipidus migrans-a radiology imaging feature after ankle injury.

We present an uncommon imaging feature with fluid fat tracking within the tendon sheath of the flexor hallucis longus (FHL) after traumatic injury to the ankle joint. We propose a coined medical term "lipidus migrans" to define the presence of floating fat in a tendon sheath. This is due to lipohemarthrosis from intra-articular fracture of the ankle with leakage of fluid fat into the tendon sheath. Communication between the FHL tendon sheath and ankle joint can occur in up to 25% of patients. Radiologists should be aware of the presence of lipidus migrans as a potential posttraumatic complication after intra-articular ankle fracture and that fat in the tendon sheath may mimic fracture fragments or even a tendon sheath tumor.

Evaluation of Chondrocalcinosis and Associated Knee Joint Degeneration Using MR Imaging: Data from the Osteoarthritis Initiative.

OBJECTIVES: To evaluate the ability of different MRI sequences to detect chondrocalcinosis within knee cartilage and menisci, and to analyze the association with joint degeneration. METHODS: Subjects with radiographic knee chondrocalcinosis (n = 90, age 67.7 ± 7.3 years, 50 women) were selected from the Osteoarthritis Initiative and matched to controls without radiographic chondrocalcinosis (n = 90). Visualization of calcium-containing crystals (CaC) was compared between 3D T1-weighted gradient-echo (T1GE), 3D dual echo steady-state (DESS), 2D intermediate-weighted (IW), and proton density (PD)-weighted fast spin-echo (FSE) sequences obtained with 3T MRI and correlated with a semiquantitative CaC score obtained from radiographs. Structural abnormalities were assessed using Whole-Organ MRI Score (WORMS) and logistic regression models were used to compare cartilage compartments with and without CaC. RESULTS: Correlations between CaC counts of MRI sequences and degree of radiographic calcifications were highest for GE (rT1GE = 0.73, P < 0.001; rDESS = 0.68, P < 0.001) compared to other sequences (P > 0.05). Meniscus WORMS was significantly higher in subjects with chondrocalcinosis compared to controls (P = 0.005). Cartilage defects were significantly more frequent in compartments with CaC than without (patella: P = 0.006; lateral tibia: P < 0.001; lateral femur condyle: P = 0.017). CONCLUSIONS: Gradient-echo sequences were most useful for the detection of chondrocalcinosis and presence of CaC was associated with higher prevalence of cartilage and meniscal damage. KEY POINTS: • Magnetic resonance imaging is useful for assessing burden of calcium-containing crystals (CaC). • Gradient-echo sequences are superior to fast spin echo sequences for CaC imaging. • Presence of CaC is associated with meniscus and cartilage degradation.

Growth plate injury at the base of the coracoid: MRI features.

PURPOSE: To assess the MRI features of growth plate injury at the base of the coracoid process. MATERIALS AND METHODS: Subjects were identified through retrospective search of our department imaging database and teaching files and the teaching files of two outside academic institutions. The coracoid base growth plate was examined with attention to widening, irregularity, abnormal signal intensity of the growth plate, and the presence of adjacent soft tissue edema. The apposing coracoid and scapular bony surfaces were examined for signal intensity and morphology. RESULTS: Shoulder MRIs in eight patients with coracoid base growth plate disturbances were retrospectively reviewed (7 males, 1 female, mean age 15 years). Growth plate injury manifested as widening, irregularity and increased signal, apposing bony marrow edema and hypertrophy, and surrounding soft tissue edema. Five subjects were athletes (football, archery, basketball, swimming, rugby), two had a history of neuromuscular disorders, and one subject presented after a fall. Clinical indications included: rule out labral tear (n = 3), rule out rotator cuff tear or fracture after fall (n = 1), nonspecific pain (n = 1), shoulder subluxation, rule out glenoid pathology (n = 1, patient with underlying neuromuscular disorder), muscular dystrophy with shoulder pain (n = 1), and impingement (n = 1). Coracoid growth plate injury was not suspected clinically in any of the patients. CONCLUSION: Awareness of the imaging appearance of coracoid base growth plate injury can aid in a more accurate diagnosis of shoulder MRI studies in young pediatric athletes. While uncommon, coracoid growth plate injury should be considered when assessing children with shoulder symptomatology.

Elbow Imaging in Sport: Sports Imaging Series.

Elbow pain is a frequent presenting symptom in athletes, particularly athletes who throw. The elbow can be injured as a result of acute trauma, such as a direct blow or a fall onto an outstretched hand or from chronic microtrauma. In particular, valgus extension overload during the throwing motion can precipitate a cascade of chronic injuries that can be debilitating for both casual and high-performance athletes. Prompt imaging evaluation facilitates accurate diagnosis and appropriate targeted interventions.

Soft-tissue aneurysmal bone cyst with translocation t(17;17)(p13;q21) corresponding to COL1A1 and USP6 loci.

We present the case of a 46-year-old woman with no significant past medical history who developed left mid-thigh pain and fullness. Imaging demonstrated a mineralized soft-tissue mass, which increased in size during a year of monitoring, but retained a circumscribed appearance. The mass was located in the medial soft tissues of the thigh, separate from the bone on imaging studies, and this finding was confirmed during excision. The mass showed gross and microscopic features of an aneurysmal bone cyst. This diagnosis was supported by cytogenetic analysis revealing a t(17;17)(p13;q21) translocation corresponding to the USP6 and COL1A1 loci. Soft-tissue aneurysmal bone cyst is a rare entity, with fewer than 25 reports in the literature. Limited cytogenetic information about these tumors is available. To our knowledge, the USP6 and COL1A1 rearrangement has only previously been described in a pediatric soft-tissue aneurysmal bone cyst. We also discuss the differential diagnosis of ossifying soft-tissue lesions.

Postoperative MRI of the shoulder.

Magnetic resonance imaging (MRI) evaluation of the postoperative shoulder presents technical and diagnostic challenges related to imaging artifacts from hardware and micrometallic shavings, postsurgical scarring, and morphological alterations. Improved visualization of postoperative shoulder anatomy and pathology can be obtained with the use of metal artifact reduction techniques as well as MR arthrography. In this article we review the MR techniques that are designed to address these technical and diagnostic challenges, and we discuss the definitions and indications, normal MRI appearance, and complications of routine surgical procedures for treatment of injuries to the rotator cuff, labral ligamentous complex, and biceps tendon.

Pitfalls in shoulder MRI: part 1--normal anatomy and anatomic variants.

OBJECTIVE: The purpose of this article is to review frequently encountered pitfalls as they pertain to normal and variant anatomy of the shoulder, including the rotator cuff and rotator cable, blood vessels, glenoid labrum, and the glenohumeral ligaments. CONCLUSION: MRI is the preferred method for evaluating internal derangement of the shoulder. Radiologists interpreting MR images should have a detailed understanding of pertinent anatomy and knowledge of common and uncommon pitfalls to avoid during image interpretation.

Pitfalls in shoulder MRI: part 2--biceps tendon, bursae and cysts, incidental and postsurgical findings, and artifacts.

OBJECTIVE: The purpose of this article is to review frequently encountered pitfalls as they pertain to the biceps tendon, bursae and cysts around the shoulder, incidental findings, postsurgical findings, and frequently encountered imaging artifacts. CONCLUSION: Imaging pitfalls in and around the shoulder are not limited to normal anatomy and anatomic variants. Radiologists must be cognizant of the vast variability of structures in the shoulder and of the incidental and postsurgical findings and artifacts affecting them.

Imaging algorithms for evaluating suspected rotator cuff disease: Society of Radiologists in Ultrasound consensus conference statement.

The Society of Radiologists in Ultrasound convened a panel of specialists from a variety of medical disciplines to reach a consensus about the recommended imaging evaluation of painful shoulders with clinically suspected rotator cuff disease. The panel met in Chicago, Ill, on October 18 and 19, 2011, and created this consensus statement regarding the roles of radiography, ultrasonography (US), computed tomography (CT), CT arthrography, magnetic resonance (MR) imaging, and MR arthrography. The consensus panel consisted of two co-moderators, a facilitator, a statistician and health care economist, and 10 physicians who have specialty expertise in shoulder pain evaluation and/or treatment. Of the 13 physicians on the panel, nine were radiologists who were chosen to represent a broad range of skill sets in diagnostic imaging, different practice types (private and academic), and different geographical regions of the United States. Five of the radiologists routinely performed musculoskeletal US as part of their practice and four did not. There was also one representative from each of the following clinical specialties: rheumatology, physical medicine and rehabilitation, orthopedic surgery, and nonoperative sports medicine. The goal of this conference was to construct several algorithms with which to guide the imaging evaluation of suspected rotator cuff disease in patients with a native rotator cuff, patients with a repaired rotator cuff, and patients who have undergone shoulder replacement. The panel hopes that these recommendations will lead to greater uniformity in rotator cuff imaging and more cost-effective care for patients suspected of having rotator cuff abnormality.

Magnetic resonance imaging of ankle tendon pathology: benefits of additional axial short-tau inversion recovery imaging to reduce magic angle effects.

OBJECTIVES: Our goals were to quantify the reduction of the magic angle effect using short-tau inversion recovery (STIR) imaging and to determine the value of adding an axial STIR sequence to the magnetic resonance imaging ankle protocol. MATERIALS AND METHODS: Axial STIR sequences were used to measure normal tendon T1 and to estimate signal loss due to the inversion recovery preparation of our clinical protocol. In addition, 102 ankles were imaged with axial fat-suppressed intermediate-weighted fast spin echo and STIR sequences. Two radiologists analyzed the tendons for signal intensity, size, abnormalities, and magic angle effect. The diagnostic value and image quality of the two sequences were compared. RESULTS: We calculated a 50% reduction of signal intensity in healthy tendons on the STIR sequence at TI = 170 ms compared with TI = 0 ms, explaining the decrease in the magic angle effect. Using the STIR sequence, our study demonstrated significantly lower signal intensity within the tendons, more precise tendon size, and a lower magic angle effect compared with the standard intermediate-weighted FSE sequence (p < 0.001). Diagnostic classification of tendon abnormalities using the STIR sequences showed higher sensitivity (82.35% vs. 75.27%) and better agreement with a reference standard than the intermediate-weighted sequences, and superior image quality (p < 0.01). CONCLUSIONS: Axial STIR sequences reduce magic angle effects and improve visualization of ankle tendon pathology.

MR and CT arthrography of the shoulder.

The combined use of shoulder arthrography with MR and CT imaging offers distinct advantages over conventional nonarthrographic imaging techniques. The improved contrast and joint distension afforded by direct arthrography optimize evaluation of various intra-articular structures and help to define subtle abnormalities and distinguish normal variants from true shoulder pathology. In this article, we review the rationale and basic approaches to shoulder arthrography as well as the imaging appearance of the normal shoulder, anatomical variants, and pathology highlighted by this technique.

Diagnosing ulnar neuropathy at the elbow using magnetic resonance neurography.

INTRODUCTION: Early diagnosis of ulnar neuropathy at the elbow is important. Magnetic resonance neurography (MRN) images peripheral nerves. We evaluated the usefulness of elbow MRN in diagnosing ulnar neuropathy at the elbow. METHODS: The MR neurograms of 21 patients with ulnar neuropathy were reviewed retrospectively. MRN was performed prospectively on 10 normal volunteers. The MR neurograms included axial T1 and axial T2 fat-saturated and/or axial STIR sequences. The sensitivity and specificity of MRN in detecting ulnar neuropathy were determined. RESULTS: The mean ulnar nerve size in the symptomatic and normal groups was 0.12 and 0.06 cm(2) (P < 0.001). The mean relative signal intensity in the symptomatic and normal groups was 2.7 and 1.4 (P < 0.01). When using a size of 0.08 cm(2), sensitivity was 95% and specificity was 80%. DISCUSSION: Ulnar nerve size and signal intensity were greater in patients with ulnar neuropathy. MRN is a useful test in evaluating ulnar neuropathy at the elbow.

Morbidity of direct MR arthrography.

OBJECTIVE: The purpose of this study was to determine the incidence and severity of arthrographic pain after intraarticular injection of a gadolinium mixture diluted in normal saline for direct MR arthrography. SUBJECTS AND METHODS: From March 2009 until January 2010, 155 consecutive patients underwent direct MR arthrography; 20 patients were lost to follow-up. Patients were contacted by telephone between 3 and 7 days after joint injection. Using an 11-point numeric pain rating scale, patients were asked to report if they had experienced joint pain that was different or more intense than their preinjection baseline, the severity of pain, the duration of pain, time to onset of pain, and eventual resolution of pain. RESULTS: The incidence of postarthrographic pain was 66% (89/135), with an average intensity of pain of 4.8 ± 2.4 (range, 1-10). Postarthrographic pain lasted an average of 44.4 ± 30.5 hours (range, 6-168 hours). The time to onset of pain after joint injection was on average 16.6 ± 13.1 hours (range, 4-72 hours). There was no significant difference regarding the severity or incidence of postarthrographic pain between groups on the basis of patient age (p = 0.20 and 0.26), patient sex (p = 0.20 and 0.86), contrast mixture contents (p = 0.83 and 0.49), or joint injected (p = 0.51 and 0.47). No patients experienced any other serious side effects. CONCLUSION: Sixty-six percent of patients who undergo direct MR arthrography will experience a fairly severe delayed onset of pain that completely resolves over the course of several days.

Bone marrow edema pattern around the knee on magnetic resonance imaging excluding acute traumatic lesions.

Magnetic resonance imaging (MRI) is very sensitive for the detection of marrow abnormalities. Bone marrow edema on MRI has been defined as an area of low signal intensity on T1-weighted images, associated with intermediate or high signal intensity findings on T2-weighted images. The bone marrow edema pattern is a nonspecific finding with multiple etiologies. The knee is a common place for bone marrow signal abnormalities to appear on MRI. Besides contusions and fractures from acute trauma, there are a variety of other causes of the bone marrow edema pattern. It is important for the interpreter of the study to be aware of the different etiologies responsible for producing these changes and to be able to narrow the differential diagnosis without mistaking such a pattern for acute trauma or infiltrative tumor. This article concentrates on those entities that produce a bone marrow edema pattern not related to acute trauma including red marrow proliferation, stress, osteochondral lesions, osteonecrosis, bone marrow edema syndrome, arthropathy, infection, Paget's disease, and marrow replacement disorders.

Stun gun induced myotendinous injury of the iliopsoas and gluteus minimus.

We report a 57-year-old man with a complete tear of his iliopsoas tendon at the distal myotendinous junction, a near complete tear of the iliopsoas tendon at the lesser trochanter of the femur, and a high-grade tear of his gluteus minimus tendon at the greater trochanter of the femur after being struck by a stun gun in the proximal left thigh. The stun gun discharge resulted in a forced contraction of the left hip flexor muscles, which resulted in pain, weakness and difficulty with active hip flexion. Three months after the being struck with the stun gun, the patient underwent magnetic resonance imaging (MRI) of the left hip. MRI of the left hip revealed a complete tear of the left iliopsoas tendon from the lesser trochanter with 4 cm of proximal retraction and a high-grade strain of the gluteus minimus tendon at the greater trochanter. The distal iliopsoas myotendinous junction and lesser trochanter tendon insertion were surgically repaired. This case illustrates that a stun gun can cause acute rupture of the iliopsoas tendon and tear of the gluteus minimus tendon, which is well visualized on MRI.

MRI of shoulder instability.

The most unstable joint in the body, the glenohumeral joint is subject to many insults including microinstability, subluxation and dislocation. During the last two decades, MRI has allowed for direct visualization of many of the lesions related to instability, aiding in diagnosis as well as therapeutic planning and follow-up. This article reviews the use of MRI for shoulder instability and describes the different types of lesions associated with this disorder. Topics include technical considerations, the use of MR arthrography, normal anatomy and variants, labral and glenohumeral ligament pathology, and osseous lesions related to instability.

Pseudotumors of the shoulder invited review.

This paper discusses the main types of MRI pseudotumors in and around the shoulder region. Some unusual types of pseudotumor will also be mentioned. Suggestions on how to improve awareness and diagnosis are also given.