Nerve Imaging in the Wrist.

Neuropathic symptoms involving the wrist are a common clinical presentation that can be due to a variety of causes. Imaging plays a key role in differentiating distal nerve lesions in the wrist from more proximal nerve abnormalities such as a cervical radiculopathy or brachial plexopathy. Imaging complements electrodiagnostic testing by helping define the specific lesion site and by providing anatomical information to guide surgical planning. This article reviews nerve anatomy, normal and abnormal findings on ultrasonography and magnetic resonance imaging, and common and uncommon causes of neuropathy.

The smoke sign: a secondary sign of unsuspected acute pectoralis major tendon injury on routine shoulder MRI.

OBJECTIVE: To study the diagnostic utility of the "smoke sign" to detect unsuspected acute pectoralis major tendon injury on routine shoulder MRI. MATERIALS AND METHODS: Retrospective study of 52 shoulder MRI in patients with (38) and without (14) acute pectoralis major injury confirmed on imaging. Two readers independently reviewed shoulder MRI for the presence of the "smoke sign"-feathery soft tissue edema lateral or anterior to short head biceps/coracobrachialis on fluid-sensitive coronal-oblique and sagittal-oblique images, respectively. RESULTS: The smoke sign was present on shoulder MRI in 24/24 (100%) humeral avulsions, 4/4 (100%) tendon tears, 4/8 (50%) of myotendinous junction injuries, and 0/2 (0%) intramuscular injuries. The smoke sign was present in 0/14 examinations without acute pectoralis major injury. CONCLUSION: While dedicated pectoralis MRI remains the preferred method for imaging pectoralis injury, the "smoke sign" can serve as an easy to recognize finding on routine shoulder MRI that can raise the suspicion of an acute pectoralis major tendon injury. Its detection should prompt evaluation of the pectoralis major tendon and recommendation for dedicated imaging to confirm and evaluate the full extent of injury.

MRI of the Fingers: An Update.

OBJECTIVE. The purpose of this article is to review the general guidelines for MRI of the finger and emphasize normal finger anatomy as it relates to abnormalities and injuries. CONCLUSION. Advanced imaging, particularly MRI, is increasingly relied on to make the diagnosis and guide management of finger injuries. It is incumbent on radiologists to understand the complex anatomy of the fingers as well as to be familiar with common injuries and aspects of injuries that affect management in order to meaningfully contribute to patient care.

Does the Addition of DWI to Fluid-Sensitive Conventional MRI of the Sacroiliac Joints Improve the Diagnosis of Sacroiliitis?

OBJECTIVE: The purpose of this study was to determine whether adding DWI to conventional MRI of the sacroiliac joints improves the diagnostic performance of MRI readers in the detection of sacroiliitis. MATERIALS AND METHODS: MR images of the sacroiliac joints of 63 patients with lower back pain obtained between January 2016 and December 2016 were analyzed retrospectively. Three readers reviewed the MRI studies for bone marrow edema lesions around the sacroiliac joints as a marker of active sacroiliitis and gave a diagnostic confidence score of 0-4 using MRI without DWI and MRI with DWI in separate sessions. The normalized apparent diffusion coefficient mean (nADCmean) was measured. Clinical and radiologic data using the Assessment of Spondyloarthritis International Society criteria were the reference for the diagnosis of sacroiliitis. Diagnostic performance, confidence scores, and interreader agreement for the MRI methods were compared. The nADCmean values of patients with and those without sacroiliitis were compared. RESULTS: The accuracy, sensitivity, and specificity of MRI without DWI were 68.3%, 69.0%, and 67.6% and for MRI with DWI were 74.6%, 69.0%, and 79.4% (accuracy and sensitivity, p > 0.100; specificity, p = 0.039). The mean confidence score for MRI without DWI was 3.60 and for MRI with DWI was 3.67 (p = 0.270). The kappa coefficient for MRI without DWI was 0.28 and for MRI with DWI was 0.46 (p = 0.041). The nADCmean in patients with sacroiliitis was 3.86 and in patients without sacroiliitis was 1.6 (p ≤ 0.001). The nADCmean AUC was 0.758 (95% CI, 0.67-0.83). CONCLUSION: The addition of DWI to conventional MRI does not significantly improve overall diagnostic performance in terms of accuracy, sensitivity, or confidence in the detection of inflammatory sacroiliitis, but it does have increased specificity and interobserver agreement. ADC threshold values can be used as predictors of sacroiliitis but give no added advantage over MRI with DWI.

Tarsal tunnel disease and talocalcaneal coalition: MRI features.

OBJECTIVE: To assess, utilizing MRI, tarsal tunnel disease in patients with talocalcaneal coalitions. To the best of our knowledge, this has only anecdotally been described before. MATERIALS AND METHODS: Sixty-seven ankle MRIs with talocalcaneal coalition were retrospectively reviewed for disease of tendons and nerves of the tarsal tunnel. Interobserver variability in diagnosing tendon disease was performed in 30 of the 67 cases. Tarsal tunnel nerves were also evaluated in a control group of 20 consecutive ankle MRIs. RESULTS: Entrapment of the flexor hallucis longus tendon (FHL) by osseous excrescences was seen in 14 of 67 cases (21 %). Attenuation, split tearing, tenosynovitis, or tendinosis of the FHL was present in 26 cases (39 %). Attenuation or tenosynovitis was seen in the flexor digitorum longus tendon (FDL) in 18 cases (27 %). Tenosynovitis or split tearing of the posterior tibial tendon (PT) was present in nine cases (13 %). Interobserver variability ranged from 100 % to slight depending on the tendon and type of disease. Intense increased signal and caliber of the medial plantar nerve (MPN), indicative of neuritis, was seen in 6 of the 67 cases (9 %). Mildly increased T2 signal of the MPN was seen in 15 (22 %) and in 14 (70 %) of the control group. CONCLUSIONS: Talocalcaneal coalitions may be associated with tarsal tunnel soft tissue abnormalities affecting, in decreasing order, the FHL, FDL, and PT tendons, as well as the MPN. This information should be provided to the referring physician in order to guide treatment and improve post-surgical outcome.

ECU tendon "dislocation" in asymptomatic volunteers.

OBJECTIVE: Assess extensor carpi ulnaris (ECU) tendon position in the ulnar groove, determine the frequency of tendon "dislocation" with the forearm prone, neutral, and supine, and determine if an association exists between ulnar groove morphology and tendon position in asymptomatic volunteers. MATERIALS AND METHODS: Axial proton density-weighted MR was performed through the distal radioulnar joint with the forearm prone, neutral, and supine in 38 asymptomatic wrists. The percentage of the tendon located beyond the ulnar-most border of the ulnar groove was recorded. Ulnar groove depth and length was measured and ECU tendon signal was assessed. RESULTS: 15.8 % of tendons remained within the groove in all forearm positions. In 76.3 %, the tendon translated medially from prone to supine. The tendon "dislocated" in 0, 10.5, and 39.5 % with the forearm prone, neutral and supine, respectively. In 7.9 % prone, 5.3 % neutral, and 10.5 % supine exams, the tendon was 51-99 % beyond the ulnar border of the ulnar groove. Mean ulnar groove depth and length were 1.6 and 7.7 mm, respectively, with an overall trend towards greater degrees of tendon translation in shorter, shallower ulnar grooves. CONCLUSIONS: The ECU tendon shifts in a medial direction when the forearm is supine; however, tendon "dislocation" has not been previously documented in asymptomatic volunteers. The ECU tendon medially translated or frankly dislocated from the ulnar groove in the majority of our asymptomatic volunteers, particularly when the forearm is supine. Overall greater degrees of tendon translation were observed in shorter and shallower ulnar grooves.

Labral and cartilage abnormalities in young patients with hip pain: accuracy of 3-Tesla indirect MR arthrography.

OBJECTIVE: Assess the diagnostic accuracy of 3-T indirect magnetic resonance arthrography (iMRA) for hip cartilage and labral pathology detection using arthroscopy as the reference standard and compare it to the published performance of direct magnetic resonance arthrography (dMRA). MATERIALS AND METHODS: Between 2009 and 2011, 290 patients suspected of having femoroacetabular impingement underwent iMRA. Our study group consisted of 41 of these patients (17 males, mean age 35 years; 24 females, mean age 33 years) who did not have a prior history of hip surgery and who subsequently underwent arthroscopy. Two experienced musculoskeletal radiologists separately evaluated the randomized and anonymized studies for the presence and quadrant location of labral and cartilage pathology. These recorded data were compared to arthroscopic reports. RESULTS: Forty-one patients had labral pathology, 34 patients had acetabular and 5 patients had femoral cartilage pathology at arthroscopy. Sensitivity, specificity, accuracy, negative- and positive-predictive values for labral lesion detection were respectively 98, 99, 99, 99 and 98 %; for acetabular cartilage lesion detection they were 69, 98, 89, 87 and 95 %; for femoral cartilage lesion detection they were 69, 95, 93 and 39 %. Sensitivities of iMRA by quadrant (anteroinferior, anterosuperior, posteroinferior, posterosuperior) for the labrum were 100.0, 95.0, NA and 85.7 %, for acetabular cartilage were NA, 58.8, NA and 39.5 % and for femoral cartilage were 50.0, 33.3, 75.0 and 75.0 %). NA indicates results not available because of the absence of findings in those quadrants. Specificities of iMRA by quadrant (anteroinferior, anterosuperior, posteroinferior, posterosuperior) for the labrum (95.0, 100.0, 95.1, 67.5 %), acetabular (100.0, 85.7, 92.6, 79.5 %) and femoral cartilage (100.0, 94.7, 96.2, 85.9 %). CONCLUSION: iMRA at 3 T is accurate in detecting labral pathology suggesting that it is a viable alternative to dMRA.

Imaging of chondral lesions including femoroacetabular impingement.

Healthy cartilage is essential for normal joint function, and osteoarthritis is the end result of cartilage injury. Hip osteoarthritis was once believed to be a disease of old age; however, younger individuals with femoroacetabular impingement have been found to have premature cartilage injury due to potentially treatable geometric hip joint abnormalities. Thus advanced knowledge of early cartilage damage in these individuals has the potential to affect their clinical course. Imaging provides methods for the noninvasive assessment of cartilage disease. Although much of imaging has been limited to the detection of physically evident abnormalities in cartilage, newer MR techniques are proving that it may be possible to assess the health of cartilage before physically evident damage is present. We review both the currently used morphologic techniques and emerging biochemical strategies used in the assessment of hip cartilage health.

Demystifying radial imaging of the hip.

The hip joint poses unique challenges at magnetic resonance (MR) imaging because of its shape and anatomic position. When conventional imaging planes are used, partial-volume averaging effects may substantially hamper the depiction of cartilage and labral damage at MR imaging. Such effects are most prevalent when the imaging plane is not perpendicular to the curvature of the joint and result in images that poorly depict or fail to depict cartilage and labral conditions. Partial-volume averaging, along with the inherently thin and closely apposed articular cartilage, may be partly to blame for the seemingly disparate reported sensitivities of MR imaging for depicting cartilage damage in the literature, which vary widely depending on whether arthrography was used. Fortunately, the multiplanar capability of MR imaging is not limited to standard anatomic planes. Radial sections, which are obtained perpendicular to the surfaces of the hip joint, provide a true cross section of the cartilage and labrum that conventional planes do not. Radial imaging is a reproducible technique that enhances the morphologic assessment of the articular cartilage and labrum. The additional information it provides is important because early damage occurs in the anterosuperior region of the hip in patients with femoroacetabular impingement.

Tendon injuries of the hip.

Hip pain is a common but potentially vexing clinical problem; symptoms may be protean, referred, and poorly localized. History and physical examination can be unreliable in discriminating between intra-articular and extra-articular origins of pain. MR imaging augments clinical evaluation by providing information about the hip joint as well as the periarticular structures, which can be a source of symptoms. This article presents an anatomy-based review of common and less common tendon pathologies on MR imaging, which are considered in the differential diagnosis of hip pain.

Ulnar variance: correlation of plain radiographs, computed tomography, and magnetic resonance imaging with anatomic dissection.

PURPOSE: Several techniques used to measure ulnar variance on a posteroanterior wrist radiograph have been described. It remains unclear whether they accurately represent the true ulnar variance of the patient. The purpose of this study was to correlate ulnar variance measurements on plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and anatomic dissection. METHODS: Posteroanterior (PA) radiographs, coronal and sagittal CT scans, and coronal MRI scans were obtained on 8 fresh-frozen cadaver wrists. The ulnar variance was measured by 5 reviewers. The specimens were then dissected, exposing the wrist joint. The ulnar variance was measured directly on each specimen using digital calipers. The inter-rater reliability was calculated for each imaging modality. The bias for each imaging modality was calculated using the digital caliper measurements as the true ulnar variance. RESULTS: Intraclass correlation coefficients demonstrated excellent inter-rater reliability for each imaging modality. The average bias from the true variance was the following: PA radiograph, 0.77 mm; coronal CT, 0.96 mm; sagittal CT, 0.96 mm; MRI with articular cartilage, 0.73 mm; MRI excluding cartilage, 0.49 mm. The variance measured on all imaging modalities tended to underestimate the magnitude of the true variance. CONCLUSIONS: Ulnar variance measured on coronal MRI best reflected the true ulnar variance as measured directly using calipers. The CT scans demonstrated the greatest deviation from the true variance. However, differences were small and might not be clinically meaningful. All imaging modalities demonstrated excellent inter-rater reliability, with MRI being highest. All imaging modalities tended to underestimate the magnitude of the true variance. CLINICAL RELEVANCE: The imaged underestimation of true ulnar variance should be taken into account when performing surgical procedures that alter the relative lengths of the radius and ulna.

The rotator interval: a review of anatomy, function, and normal and abnormal MRI appearance.

OBJECTIVE: The purpose of this article is to review imaging of the rotator interval, an anatomically complex region in the shoulder that plays an important role in the normal function of the shoulder joint. The rotator interval can be difficult to evaluate by imaging, and it is not routinely evaluated arthroscopically unless the clinical examination or imaging findings suggest an abnormality of the rotator interval. Rotator interval pathology is implicated in glenohumeral instability, biceps instability and adhesive capsulitis-entities which remain a challenge to diagnose and treat. CONCLUSION: Imaging can play an important role in increasing suspicion for injury to the rotator interval so that this region can be evaluated and appropriate treatment can be initiated.

MR imaging of entrapment neuropathies of the lower extremity. Part 1. The pelvis and hip.

Entrapment neuropathies can manifest with confusing clinical features and therefore are often underrecognized and underdiagnosed at clinical examination. Historically, electrophysiologic evaluation has been considered the mainstay of diagnosis. Today, cross-sectional imaging, particularly magnetic resonance (MR) imaging and specifically MR neurography, plays an increasingly important role in the work-up of entrapment neuropathies. MR imaging is a noninvasive operator-independent technique that allows identification of the underlying cause of injury, differentiation between surgically treatable and untreatable causes, and guidance of selective diagnostic anesthetic nerve blocks. Pathologic conditions affecting the lumbosacral plexus and major motor and mixed nerves of the pelvis and hip include neuropathies of the lumbosacral plexus, femoral nerve, lateral femoral cutaneous nerve, obturator nerve, and sciatic nerve; piriformis muscle syndrome; and injury of the gluteal nerves. Diagnosis of entrapment neuropathies of the pelvis and hip with MR imaging requires familiarity with the normal MR imaging anatomy and awareness of the anatomic and pathologic factors that put peripheral nerves at risk for injury.

Cortical lesions of the tibia: characteristic appearances at conventional radiography.

Lesions that involve the cortex of the tibia are fairly common in radiology practice. However, the number of diseases that involve the tibial cortex is great, and it can be difficult to arrive at a limited differential diagnosis from radiographic findings. Categorization of lesions of the tibia into those that cause cortical destruction and those that cause cortical proliferation can help narrow the broad differential diagnosis. Lesions that cause cortical destruction include nonossifying fibroma, fibrous dysplasia, osteofibrous dysplasia, aneurysmal bone cyst, giant cell tumor, eosinophilic granuloma, Ewing sarcoma, neurofibromatosis, adamantinoma, osteoblastoma, chondromyxoid fibroma, hemangioendothelioma, renal cell metastatic disease, hemangioma, and hemangiopericytoma. Lesions that cause cortical proliferation include osteochondroma, stress fracture, osteoid osteoma, periosteal osteogenic sarcoma, diaphyseal dysplasia, venous stasis, cellulitis, chronic osteomyelitis, osteopathia striatum, and melorheostosis. Conventional radiography along with clinical and pathologic data can aid in diagnosis of the wide variety of disease processes that involve the tibial cortex.