Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space.

Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included "piriformis syndrome," a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes. The concept of fibrous bands playing a role in causing symptoms related to sciatic nerve mobility and entrapment represents a radical change in the current diagnosis of and therapeutic approach to DGS. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. A broad spectrum of known pathologies may be located nonspecifically in the subgluteal space and can therefore also trigger DGS. These can be classified as traumatic, iatrogenic, inflammatory/infectious, vascular, gynecologic and tumors/pseudo-tumors. Because of the ever-increasing use of advanced magnetic resonance neurography (MRN) techniques and the excellent outcomes of the new endoscopic treatment, radiologists must be aware of the anatomy and pathologic conditions of this space. MR imaging is the diagnostic procedure of choice for assessing DGS and may substantially influence the management of these patients. The infiltration test not only has a high diagnostic but also a therapeutic value. This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments, with emphasis on MR imaging and endoscopic correlation.

Myotendinous junction tear of the anterior bundle of the supraspinatus muscle-a rare pattern of injury involving rotator cuff muscles.

Myotendinous junction injuries are rare and often present with distinctive imaging findings that should be differentiated from purely tendinous degenerative ruptures. Myotendinous junction tears are common in the lower limb but rarely involve rotator cuff muscles. Considering rotator cuff muscles, the infraspinatus and supraspinatus muscles are the most frequently implicated. The intrinsic anatomy of the supraspinatus muscle gives it a greater contractile force and consequently a propensity for rupture. It is composed of two bundles: anterior and posterior (with the latest further divided in a deep anterior, a medial and a superficial posterior portion). These two components have distinctive anatomy with the anterior bundle having a long intramuscular tendon and bipennate configuration and the posterior bundle having a smaller intramuscular tendon and parallel muscle fibres. This distinctive anatomy grants a greater contractile force to the anterior bundle of the supraspinatus muscle and for this reason it is more prone to myotendinous rupture. This type of injury has been associated with a rapid progression to severe fatty infiltration and should be differentiated from purely tendinous tears that are more frequent and associated with degenerative changes. Myotendinous tears occur centrally located in the muscle belly and are not associated with full thickness tears of the distal tendon attachment.

Wrist MR arthrography: how, why, when.

MR imaging of the wrist frequently represents a diagnostic challenge for radiologists because of the complex anatomy of this joint, small size of its components, and little known pathologic conditions. MR arthrography combines the advantages of conventional MR imaging and arthrography by improving the visualization of small intra-articular abnormalities. This article reviews the current role of MR arthrography in the evaluation of wrist joint disorders considering the relevant aspects of anatomy, techniques, and applications.

Ankle MR arthrography: how, why, when.

MR arthrography has become an important tool for the assessment of a variety of ankle disorders. MR arthrography may facilitate the evaluation of patients with suspected intra-articular pathology in whom conventional MR imaging is not sufficient for an adequate diagnosis and be useful for therapy planning. MR arthrography is valuable in the evaluation of ligamentous injuries, impingement syndromes, cartilage lesions, osteochondral lesions of the talus, loose bodies, and several synovial joint disorders. Indirect MR arthrography is a useful adjunct to conventional MR imaging and may be preferable to direct MR arthrography in cases in which an invasive procedure is contraindicated or when fluoroscopy is not available.

MR imaging findings in ulnar-sided wrist impaction syndromes.

Ulnar-sided wrist impaction syndromes are a common source of ulnar pain and limitation of motion. These conditions refer to a group of pathologic entities that result from repetitive or acute forced impaction between the distal ulna and ulnar carpus or distal radius and surrounding soft tissues. MR imaging allows earlier detection of the bone and soft-tissue lesions that are present in the different ulnar-sided wrist impaction syndromes and is helpful in formulating the extensive differential diagnosis in patients with ulnar wrist pain and limitation of motion.

Imaging findings in ulnar-sided wrist impaction syndromes.

Impaction syndromes related to ulnar-sided pain include ulnar impaction syndrome, ulnar impingement syndrome, ulnocarpal impaction syndrome secondary to nonunion of the ulnar styloid process, ulnar styloid impaction syndrome, and hamatolunate impingement syndrome. The most common of these, ulnar impaction syndrome, is a degenerative condition of the ulnar side of the wrist related to excessive load bearing across the ulnar carpus, triangular fibrocartilage (TFC) complex, and ulnar head. In an adequate clinical setting, characteristic osseous findings at radiography include positive ulnar variance in ulnar impaction syndrome, a short ulna in ulnar impingement syndrome, nonunion of the ulnar styloid process in ulnar impaction syndrome secondary to ulnar styloid nonunion, an excessively long ulnar styloid process in ulnar styloid impaction syndrome, and type II lunate bone in hamatolunate impingement syndrome. Nevertheless, confirmation of clinical and conventional radiographic findings with magnetic resonance (MR) imaging is often necessary to exclude other entities with similar clinical manifestations. MR imaging allows earlier detection of an abnormality in the TFC complex, cartilage, or bone marrow of carpal bones and is helpful in formulating the extensive differential diagnosis in patients with ulnar wrist pain and limitation of motion.

Anatomy and MR imaging appearances of synovial plicae of the knee.

Synovial plicae are normal anatomic structures of the knee that sometimes become symptomatic. Magnetic resonance (MR) imaging and MR arthrography are useful tools in the evaluation of synovial plicae and allow differentiation of these entities from other causes of knee pain. At MR imaging, synovial plicae appear as bands of low signal intensity within the high-signal-intensity joint fluid. Gradient-echo T2-weighted and fat-suppressed T2-weighted or proton density-weighted MR images are optimal for the evaluation of plicae. Plica syndrome, the painful impairment of knee function in which the only finding that helps explain the symptoms is the presence of a thickened and fibrotic plica, should be included in the differential diagnosis of internal derangement of the knee. A diffusely thickened synovial plica, perhaps associated with synovitis or erosion of the articular cartilage of the patella or femoral condyle, in a patient with no other significant MR imaging findings suggests the diagnosis of plica syndrome. Once the diagnosis has been made, nonsurgical treatment is preferable initially. Failure of the patient to improve with conservative treatment leaves arthroscopic excision of the pathologic plica as the treatment of choice.