David P. Fessell

Entrapment neuropathies I: upper limb (carpal tunnel excluded).

Several entrapment neuropathies of the upper extremity can cause hypoechoic swelling and nerve compression as seen at ultrasound. The ulnar nerve can be compressed at the cubital tunnel of the elbow and Guyons canal at the wrist. The deep branch of the radial nerve can be compressed at the supinator muscle at the elbow, and the superficial radial nerve may be compressed at the dorsal wrist (Wartenbergs syndrome). In addition to compression at the carpal tunnel, the median nerve may be compressed at the elbow, related to a supracondylar process or by the pronator teres. Knowledge of these key anatomical sites of potential nerve compression is essential for accurate diagnosis of entrapment neuropathies.

FOOT AND ANKLE SONOGRAPHY

Sonography of the foot and ankle offers many advantages. Currently, sonographic evaluation rivals or exceeds MR imaging for evaluation of tendons, joint and bursal pathology, and specific soft tissue pathology. The advantages of sonographic evaluation provide a strong impetus for applying this modality to imaging of foot and ankle pathology. Those who accept the challenge will have an expanded repertoire to offer in the pursuit of efficient and effective patient care.

Sonography of Partial-Thickness Quadriceps Tendon Tears With Surgical Correlation

Objective. With the use of surgical findings as the reference standard, the purpose of this study was to describe the sonographic findings of partial‐thickness and complete tears of the quadriceps tendon and to determine whether sonography can potentially aid diagnosis. Methods. Three hundred eighty‐nine consecutive sonographic reports (January 1996 to April 2001) of the knee/quadriceps tendon were reviewed retrospectively and assessed for subsequent surgery on the quadriceps tendon. Seven cases were thus identified. Findings at surgery (complete versus partial tears) were compared with the original sonography reports. Results. All 4 partial tears and 1 of 2 complete tears were diagnosed correctly on the basis of sonography. One complete tear was described as a partial tear on the basis of sonography. In a seventh case, complete disruption of the extensor mechanism with osseous avulsion of the superior pole of the patella was identified correctly. Dynamic scanning was essential in diagnosing a partial quadriceps tendon tear in 1 case. Conclusions. Sonography, including the use of dynamic evaluation, was helpful in the diagnosis of partial‐thickness tears of the quadriceps tendon and may aid in differentiation of such cases from complete quadriceps tendon tears, particularly in the acute setting. The presence of scar tissue in the setting of chronic injury may represent a potential pitfall in the assessment of partial versus complete quadriceps tears. Further study is needed to define the accuracy of sonography for detecting quadriceps tendon tears.

Achilles Tendon Ultrasound Technique

As the strongest tendon of the human body, the Achilles tendon originates from the soleus and gastrocnemius muscles, and inserts onto the posterior calcaneal tuberosity. The tendon is surrounded by a paratenon rather than a synovial sheath. Sonography is an efficient and accurate way to assess the Achilles tendon. Advantages of sonographic evaluation include cost, widely available equipment, ease of contralateral comparison, and the ability to image during joint motion. Ultrasound Technique The ultrasound technique for imaging the Achilles tendon is as follows: •� Position: The patient is prone with the foot hanging over the edge of the table. Mild dorsiflexion of the ankle and use of thick transmission gel help optimize imaging. •� Transducer: A high-frequency transducer of at least 10 MHz is typically used given the superficial location of the structures. •� Longitudinal and transverse evaluation: The Achilles tendon can be easily seen when the transducer is placed in the sagittal plane, longitudinal to the tendon fibers. The transducer is moved proximally from the insertion site at the calcaneal tuberosity to the myotendinous junction. The transducer is turned 90 degrees for evaluation in the transverse plane. •� Normal appearance: The Achilles tendon should be uniform in thickness and echogenicity in a longitudinal plane, and has a predominately flat or concave anterior margin in a transverse plane. •� Dynamic evaluation: Dynamic imaging is important in evaluation of Achilles tendon tears since hemorrhage, fluid, debris, or scar tissue may fill the gap between torn tendon ends. With passive movement of the foot or by gently squeezing the calf muscles (Thompson test), the gap between the torn tendon ends becomes more obvious as one tendon end moves without translation of movement to the other tendon end.

The role of sonography in differentiating full versus partial distal biceps tendon tears: correlation with surgical findings.

OBJECTIVE The purpose of this study was to determine the accuracy of ultrasound for distinguishing complete rupture of the distal biceps tendon versus partial tear and versus a normal biceps tendon. Surgical findings were used as the reference standard in cases of tear. Clinical follow-up was used to assess the normal tendons. MATERIALS AND METHODS The study population consisted of 45 consecutive elbow ultrasound cases with surgical confirmation and six cases of a clinically normal distal biceps tendon that underwent elbow ultrasound for suspicion of injury to a structure other than the biceps tendon. Cases underwent consensus review by two fellowship-trained musculoskeletal radiologists. Tendons were classified as normal biceps tendon, partial tear, or complete tear. The presence or absence of posterior acoustic shadowing at the distal biceps tendon was also assessed. The ultrasound findings were then compared with the surgical findings and clinical follow-up. RESULTS Ultrasound showed 95% sensitivity, 71% specificity, and 91% accuracy for the diagnosis of complete versus partial distal biceps tendon tears. Posterior acoustic shadowing at the distal biceps had sensitivity of 97% and accuracy of 91% for indicating complete tear versus partial tear and sensitivity of 97%, specificity of 100%, and accuracy of 98% for indicating complete tear versus normal tendon. CONCLUSION Ultrasound can play a role in the diagnosis of elbow injuries when a distal biceps brachii tendon tear is suspected.

Entrapment Neuropathies in the Upper and Lower Limbs: Anatomy and MRI Features

Peripheral nerve entrapment occurs at specific anatomic locations. Familiarity with the anatomy and the magnetic resonance imaging (MRI) features of nerve entrapment syndromes is important for accurate diagnosis and early treatment of entrapment neuropathies. The purpose of this paper is to illustrate the normal anatomy of peripheral nerves in the upper and lower limbs and to review the MRI features of common disorders affecting the peripheral nerves, both compressive/entrapment and noncompressive, involving the suprascapular nerve, the axillary nerve, the radial nerve, the ulnar nerve, and the median verve in the upper limb and the sciatic nerve, the common peroneal nerve, the tibial nerve, and the interdigital nerves in the lower limb.

Sonography of fat necrosis involving the extremity and torso with magnetic resonance imaging and histologic correlation.

Objective. The purpose of this study was to describe the sonographic appearance of pathologically proven isolated fat necrosis involving the extremities or torso with magnetic resonance imaging (MRI) correlation. Methods. A query of the Department of Pathology database at our institution for the diagnosis of fat necrosis resulted in 1539 cases. Review of the cases and medical records excluded cases without sonographic imaging, those involving the breast, and those within or adjacent to a primary process, including masses or prior surgery, which resulted in a total of 5 cases of primary fat necrosis, 2 of which were evaluated with MRI. Sonograms were reviewed by 2 musculoskeletal radiologists and characterized with regard to location, echogenicity, shadowing, posterior through‐transmission, a hypoechoic rim or halo, definition of borders, homogeneity, a mass effect, and vascularity. The patient medical records, histologic results, and MRI findings were also reviewed. Results. Of the 5 cases of isolated fat necrosis, 2 involved the torso and 3 the lower extremities. On sonography, all were located in the subcutaneous fat; 2 were isoechoic; 3 were hyperechoic; 2 had a hypoechoic halo; none showed shadowing or posterior through‐transmission; 2 were well defined; 3 were masslike; 4 were heterogeneous; and 2 showed increased flow on color or power Doppler imaging. Magnetic resonance imaging showed an intermediate signal and either diffuse or ring enhancement. Conclusions. Isolated fat necrosis of the extremities and torso had 2 sonographic appearances, which included a well‐defined isoechoic mass with a hypoechoic halo and a poorly defined hyperechoic region in the subcutaneous fat.

Ultrasound and MRI of the peroneal tendons and associated pathology

Lateral ankle pain is common with overuse and sports-related injuries and may cause considerable morbidity. The differential diagnosis of lateral ankle pain is extensive. Disorders of the peroneal tendons should be an important consideration during interpretation of a routine ankle magnetic resonance imaging (MRI) or ultrasound (US). This article presents a review of the common causes of peroneal tendon pathology with particular reference to anatomy, US, and MRI features. The importance of dynamic evaluation with ultrasound is also emphasized.

Ultrasound Compared With Magnetic Resonance Imaging for the Diagnosis of Rotator Cuff Tears: A Critically Appraised Topic

Failure of rotator cuff tendons because of wear and tear is the most common clinical problem of the shoulder, with more than 4.5 million physician visits per year in the United States. 1 Although failure can result from acute trauma, it more commonly arises from age-related attrition of the tendons. Rotator cuff injury increases with age, with two-thirds of asymptomatic persons over 70 years showing tendon tears by ultrasound imaging. Rotator cuff injury is more common inobesepersons,andlocalsteroidinjectionsandnicotineuse have been implicated in impairing tendon healing. 1 Both magnetic resonance imaging (MRI) and ultrasound (US) have evolved to become the mainstay in evaluation of the rotator cuff for tears or injury. 2 These techniques have essentially obviated the need for conventional shoulder arthrography. Technical improvements, coupled with a better understanding of rotator cuff anatomy and pathology, have resulted in maturation of these 2 modalities. However, diagnostic difficulty can arise because of technical limitations, artifacts, operator experience, and interpretative pitfalls. MRI, which is more universally accepted, may be limited in evaluating partial tears, whereas US is more challenging to perform, especially for beginners. 2 This article describes the use of evidence-based practice (EBP) techniques as a means of deciding the appropriateness of MRI or US in diagnosing rotator cuff tears.

Capsular Laxity of the Hip: Findings at Magnetic Resonance Arthrography

PURPOSE The purpose of this study was to retrospectively investigate magnetic resonance (MR) arthrography imaging findings associated with capsular laxity of the hip joint found at surgery. METHODS After institutional review board approval, 27 patients who had arthroscopy reports that described the presence or absence of capsular laxity of the hip joint were identified over a 2-year period. Preoperative MR images were retrospectively reviewed by 2 blinded radiologists. The following observations were recorded: (1) thickness, signal intensity, and defects of the anterior joint capsule; (2) thickness and signal intensity of the zona orbicularis; (3) width of the anterior and posterior joint recesses at the level of the femoral head; (4) presence of synovitis in the anterior joint recess; and (5) volume of intra-articular contrast and degree of hip rotation. Intrarater and inter-rater agreement was assessed. RESULTS Of the 27 patients, 17 were positive and 10 were negative for hip joint laxity at arthroscopy. The mean thickness of the anterior hip capsule was significantly different (P = .0043), measuring 2.5 mm (95% confidence interval [CI], 2.3 to 2.8 mm) in those with hip laxity and 3.3 mm (95% CI, 2.8 to 3.8 mm) in those without laxity. The mean width of the anterior joint recess was 5.8 mm (95% CI, 5.4 to 6.3 mm) in those with laxity and 3.6 mm (95% CI, 3.3 to 3.9 mm) in those without laxity and was significantly different (P < .0001). No other variables were considered useful because of a lack of significant differences between the 2 patient groups or low inter-rater agreement. CONCLUSIONS On the basis of 95% CIs, hip joint laxity at MR arthrography is associated with widening of the anterior hip joint recess (>5 mm) and thinning of the adjacent joint capsule (<3 mm) lateral to the zona orbicularis.