Ali Naraghi

Accessory muscles: Anatomy, symptoms, and radiologic evaluation

A wide array of supernumerary and accessory musculature has been described in the anatomic, surgical, and radiology literature. In the vast majority of cases, accessory muscles are asymptomatic and represent incidental findings at surgery or imaging. In some cases, however, accessory muscles may produce clinical symptoms. These symptoms may be related to a palpable swelling or may be the result of mass effect on neurovascular structures, typically in fibro-osseous tunnels. In cases in which an obvious cause for such symptoms is not evident, recognition and careful evaluation of accessory muscles may aid in diagnosis and treatment.

MRI of Labral and Chondral Lesions of the Hip

OBJECTIVE Unenhanced MRI, indirect MR arthrography, and direct MR arthrography have been used in the radiologic evaluation of patients with suspected labral tears and chondral lesions of the hip. The purpose of this article is to examine the existing evidence for the use of these techniques in patients with hip pain and suspected labral or chondral abnormalities. CONCLUSION Evidence from a review of the radiologic literature supports the use of direct MR arthrography over unenhanced MRI and indirect MR arthrography for the detection of labral and cartilage abnormalities in the hip. Although high-resolution unenhanced 3-T MRI appears promising, limited information in the literature supports its use in the detection and characterization of chondrolabral lesions.

Three-Dimensional MRI of the Musculoskeletal System

OBJECTIVE The purposes of this review are to describe commonly available 3D MRI techniques and to discuss the literature to date regarding the utility of such techniques in the assessment of internal derangement of joints. CONCLUSION Long acquisition and postprocessing times and limited contrast characteristics have generally prohibited routine use of 3D MRI in clinical practice. However, technical advances, including higher-field-strength MRI systems, high performance gradients, high-resolution multichannel coils, and pulse sequences with shorter acquisition times, have made feasible 3D isotropic MRI with reasonable acquisition times.

Diffusion tensor imaging of peripheral nerves

Diffusion tensor imaging (DTI) is a powerful MR imaging technique that can be used to probe the microstructural environment of highly anisotropic tissues such as peripheral nerves. DTI has been used predominantly in the central nervous system, and its application in the peripheral nervous system does pose some challenges related to imaging artifacts, the small caliber of peripheral nerves, and low water proton density. However advances in MRI hardware and software have made it possible to use the technique in the peripheral nervous system and to obtain functional data relating to the effect of pathologic processes on peripheral nerves. This article reviews the imaging principles behind DTI and examines the literature regarding its application in assessing peripheral nerves.

Intramuscular Fat Infiltration Contributes to Impaired Muscle Function in COPD.

UNLABELLED Muscle weakness is a prevalent complication in chronic obstructive pulmonary disease (COPD). Atrophy does not fully explain muscle weakness in this population. The recent focus on fat infiltration and its clinical implications in age and diseased muscles are important because it may further explain the extent of declining muscle strength and mobility seen in COPD. PURPOSE The objectives of this study are to quantify fat infiltration (muscle quality) of lower-limb muscles in people with COPD and healthy older adults using magnetic resonance imaging and proton magnetic resonance spectroscopy, and to explore its relationship with muscle strength and walking capacity in COPD. METHODS T1-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy were performed in people with COPD (n = 10) and control subjects (n = 10) matched for age, gender, and body mass index. Maximal cross-sectional area (muscle size), isokinetic and isometric muscle peak torques, and 6-min walk distance were also assessed. RESULTS In addition to muscle atrophy (mean between-group differences of 20% to 25%, P < 0.05), COPD group presented with fatty infiltration in thigh and calf muscles that were significantly greater than what was observed in their healthy counterparts (mean between-group differences of 74% to 89%, P = 0.001). There was a strong inverse correlation between intramuscular fat infiltration, muscle peak torque, and walking distance (r = -0.6 to -0.8, P < 0.001) in this group as opposed to fair-to-moderate correlations between muscle size and the same outcomes (r = 0.4-0.6, P < 0.01). CONCLUSION Poor muscle quality accompanies atrophy in people with COPD. Intramuscular fat infiltration not only appears to have a strong correlation with impaired function but also is more profound than muscle atrophy in this group. Monitoring both muscle size and quality may enable a more comprehensive assessment of exercise programs in COPD.

Pitfalls and Pearls in MRI of the Knee

OBJECTIVE The purpose of this article is to review the common pitfalls in MRI of the knee and pearls on how to avoid them. CONCLUSION MRI of the knee is highly accurate in evaluation of internal derangements of the knee. However, a variety of potential pitfalls in interpretation of abnormalities related to the knee have been identified, particularly in evaluation of the menisci, ligaments, and articular cartilage.

Anterior Cruciate Ligament Reconstruction: MR Imaging Signs of Anterior Knee Laxity in the Presence of an Intact Graft

PURPOSE To determine the accuracy of secondary magnetic resonance (MR) imaging signs of anterior cruciate ligament (ACL) insufficiency in predicting clinical anterior translational knee laxity, in the presence of an intact graft, after ACL reconstruction. MATERIALS AND METHODS Institutional review board approval was obtained, and the requirement to obtain informed consent was waived. Fifty-two patients with ACL reconstruction and no injury to the contralateral knee were included. Three patients with visible ACL graft tears at MR imaging were excluded. All patients underwent MR imaging of the affected knee, functional assessment with use of the International Knee Documentation Committee (IKDC) score, and arthrometric testing of both the affected and uninjured knee. A side-to-side difference of more than 3 mm at 133 N was considered to be indicative of knee laxity. Two radiologists independently evaluated all MR images for seven signs of anterior knee laxity. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for each MR imaging sign. RESULTS Ten patients demonstrated knee laxity at arthrometric testing. Patients with knee laxity at arthrometric testing had significantly lower IKDC scores (P < .03). Sensitivities for all signs were low (0%-50%). Anterior translation of the tibia of more than 7 mm, a posterior cruciate ligament (PCL) angle of less than 100°, and a PCL curvature ratio of more than 0.39 demonstrated high specificity (range, 82%-90%). Uncovering of the posterior horn of the lateral meniscus and the posterior femoral line had a specificity of 97%-100% and a sensitivity of 0%. All signs had a low PPV and high NPV for laxity. All MR imaging signs demonstrated near-perfect interobserver agreement. CONCLUSION Although MR imaging signs of knee laxity in the presence of an intact ACL graft have a high specificity, the low PPV means that MR imaging is of little value in predicting anterior knee laxity as demonstrated with mechanical testing.

Anterior cruciate ligament reconstruction by using bioabsorbable femoral cross pins : MR imaging findings at follow-up and comparison with clinical findings

PURPOSE To determine the frequency of imaging findings and complications related to bioabsorbable femoral cross pins at follow-up magnetic resonance (MR) imaging studies after anterior cruciate ligament (ACL) reconstruction and compare these MR imaging findings with clinical evaluation findings. MATERIALS AND METHODS The institutional review board approved this retrospective study, and informed consent was waived. Follow-up MR imaging studies (average, 26 months after surgery) in 218 patients with prior ACL reconstruction were retrospectively reviewed. Cross-pin fracture, posterior transcortical breach, migration, resorption, and lateral prominence of cross pins, as well as the cross-pin angle relative to the transepicondylar line, were investigated on MR images. The clinical evaluation included Lachman, anterior drawer, and pivot shift tests, as well as assessment for joint tenderness. RESULTS Fracture, posterior transcortical breach, migration, and lateral prominence of cross pins were excluded from analysis when at least one cross pin was completely resorbed (n = 16 patients). Forty-five fractured cross pins were seen in 35 (17%) of 202 patients. The posterior femoral cortex was breached in 57 (28%) of 202 patients. Migration of fractured pin fragments occurred in 12 (6%) of 202 patients. There was a significant relationship between fractures and posterior breach of cross pins (P = .001), as well as between cross-pin angles and fractures (P = .002). Both cross pins were completely resorbed in 12 (6%) of 218 patients (average time since surgery, 53 months; range, 8-92 months). No significant association was found between any MR imaging finding related to cross pins and clinical test findings. CONCLUSION Fracture and posterior transcortical breach of bioabsorbable femoral cross pins, commonly seen at follow-up MR imaging studies, do not correlate with clinical findings of joint instability or pain. Posteriorly angulated cross pins and posterior transcortical breach are significantly associated with cross-pin fractures.

Synthetic-echo time postprocessing technique for generating images with variable T2-weighted contrast: diagnosis of meniscal and cartilage abnormalities of the knee

PURPOSE To assess the feasibility and accuracy of a synthetic-echo time (TE) magnetic resonance (MR) postprocessing technique for the diagnostic evaluation of abnormalities of menisci and articular cartilage in the knee. MATERIALS AND METHODS This study was approved by the institutional review board. Twenty-four patients (three women, 21 men; mean age, 44.8 years) gave informed written consent to prospectively undergo evaluation of their knees (10 left and 14 right knees) with standard sagittal intermediate-weighted (repetition time msec/TE msec, 2200/17) and fat-saturated T2-weighted (3600/88) fast spin-echo sequences. In addition, sagittal multiecho fast gradient-echo sequences were performed for the generation of synthetic-TE images with variable T2- or T2(*)-weighted contrast by using a newly developed synthetic-TE analysis tool that was incorporated directly into the picture archiving and communication system. Sensitivity, specificity, and accuracy values for detection of lesions in menisci and articular cartilage were calculated by using findings at surgery as reference standard. RESULTS The standard intermediate-weighted and fat-suppressed T2-weighted MR sequences had overall sensitivity, specificity, and accuracy values of 100% and 100%, 88% and 93%, and 95% and 95% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 82%, 97%, and 95%, respectively, for articular cartilage defects. Corresponding sensitivity, specificity, and accuracy values for multiecho MR imaging with synthetic-TE MR image generation were 92% and 100%, 88% and 87%, and 90% and 90% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 70%, 99%, and 95%, respectively, for articular cartilage defects. CONCLUSION For the evaluation of menisci and articular cartilage, images generated with the synthetic-TE technique are a potentially viable alternative to standard T2-weighted images obtained at different TEs. Furthermore, the synthetic-TE approach allowed assessment of abnormalities of menisci and articular cartilage with high sensitivity and specificity.

Dissecting the accessory soleus muscle: A literature review, cadaveric study, and imaging study

The accessory soleus muscle (ASM) has been an unusual anatomical variant since its first recordings in Guys Hospital Reports of the early nineteenth century. Individuals with an ASM may present with symptoms of pain and/or swelling and were often misdiagnosed as soft‐tissue tumors such as hemangioma, sarcoma, or lipoma. The aim of our study was threefold: (1) to review the cadaveric and clinical literature to determine the reported prevalence of ASM; (2) to conduct a cadaveric study investigating the prevalence and attachment sites of the ASM; (3) to conduct a retrospective analysis of magnetic resonance imaging (MRI) of patients presenting with ankle symptoms to determine prevalence and attachment sites of the ASM. Our findings demonstrated that the prevalence of the muscle (3%) was as stated in the literature (0.7–5.5%), but with males more likely to possess unilateral ASM and females more likely to possess bilateral ASM. Three common attachment types were reported in the literature: (i) a distal attachment to the medial aspect of the calcaneus by a separate tendon (26.1% of ASM subjects), (ii) a distal tendinous attachment to the calcaneal tendon (3.5%), and (iii) a distal fleshy attachment to the medial surface of the calcaneus (4.3%), with the remaining 66.1% of ASM subjects from previous studies with unidentified attachment types. Our cadaveric specimens were found to possess each attachment type, whereas imaging patients all possessed distal attachments to the medial calcaneus via a separate tendon. Furthermore, a rare cadaveric specimen with two distal attachments was also found. We believe it is important to recognize the prevalence of this condition and be aware of its morphology in order to understand its clinical presentation, accurately diagnose the condition, and pursue effective forms of management. Clin. Anat. 24:903–910, 2011.