Posterosuperior glenoid internal impingement of the shoulder in the overhead athlete: pathogenesis, clinical features and MR imaging findings.

Posterosuperior glenoid internal impingement (PGII) is an impingement syndrome of the shoulder that is most commonly seen in the throwing or overhead athlete. The supraspinatus can be normally compressed or impinged between the greater tuberosity and the posterosuperior labrum in the abduction and external rotation position. However, repetitive throwing and biomechanical abnormalities may lead to the intensification of this contact and to the clinical and pathological picture of PGII. The injured athlete usually complains of poor throwing performance and pain located in the posterosuperior aspect of the shoulder. Two main theories regarding the aetiology of PGII have been postulated with differing initial mechanisms. The MRI features of PGII have been described and include supraspinatus and anterior infraspinatus partial undersurface tears, bony changes at the humeral head and labral pathology, including a variation of the type II superior labrum from anterior to posterior lesion. This pictorial essay aims to present cases illustrating the pathophysiology, clinical features and recently described MRI findings, and discuss some of the MR protocol considerations.

Are extra-labral MR findings useful in the diagnosis of a labral tear?

OBJECTIVE: To determine diagnostic performance statistics of extra-labral magnetic resonance (MR) findings for detection of labral tears in a population of patients with clinical suspicion of this diagnosis. MATERIALS AND METHODS: Seventy-nine patients clinically suspected of having a labral tear (who underwent arthroscopy) had their MR studies retrospectively reviewed to determine the presence of lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes. These findings were then correlated with the arthroscopic presence (or absence) of a labral tear. RESULTS: All findings (lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) had a specificity and positive predictive value (PPV) of 100%. Lateral acetabular oedema-like marrow signal had a sensitivity of 35% and 20% negative predictive value (NPV). This was the only statistically significant finding (P < 0.05). The sensitivity and NPV of ganglia were 12% and 16%, dysplastic femoral bumps (12%, 16%), synovial herniation pits (4%, 14%) and geodes (6%, 15%) respectively, (P > 0.05). CONCLUSION: Lateral acetabular oedema-like marrow signal is a useful sign (100% PPV) in the MR diagnosis of a labral tear, if one is clinically suspected. The other findings (ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) were not statistically significant. Further studies are required to evaluate these.

Muscle injury of the chest wall and upper extremity.

Most muscle trauma more commonly involves the lower extremity, but injury to the chest wall, particularly the pectoralis major, is well recognized. Trauma to the upper limb muscle-tendon unit is preserved. Development of complications from muscle injury is also discussed. This article systematically reviews the clinical features, pathogenesis, imaging findings, and management for upper limb and chest wall muscle injuries. Imaging modalities focus on magnetic resonance imaging and ultrasound, highlighting their advantages and disadvantages in specific situations.

Prevalence and location of acetabular sublabral sulci at hip arthroscopy with retrospective MRI review.

OBJECTIVE: The objective of this prospective study was to determine the prevalence and location of acetabular sublabral sulci diagnosed as variants at hip arthroscopy and to provide a retrospective MRI review. SUBJECTS AND METHODS: Two experienced hip arthroscopists noted the prevalence and location of acetabular labral sulci in 121 patients. The study population consisted of 57 males and 64 females with an average age of 43 years (range, 16-70 years). Of the 121 hip arthroscopies that showed sulci (22% of patients), correlation with the relevant MR studies (n = 27) was performed. Two radiologists who were aware of the arthroscopic findings reviewed the MR studies retrospectively, and agreement on imaging appearances was reached by consensus. RESULTS: Arthroscopy revealed 30 sulci (25%) in 27 of the 121 patients. In those who had a single sulcus (25 patients), 11 (44%) were located anterosuperiorly, 12 (48%) posteroinferiorly, one (4%) anteroinferiorly, and one (4%) posterosuperiorly. The other two patients had more than one sulcus: one patient had one posterosuperior sulcus and one posteroinferior sulcus; and the other patient had one anterosuperior sulcus, one anteroinferior sulcus, and one posteroinferior sulcus. In total, of the 121 patients, the number and position of the sulci were 12 anterosuperior (10%), 14 posteroinferior (12%), two anteroinferior (2%), and two posterosuperior (2%). Of the 27 MR examinations, 24 were unenhanced and three studies were performed after intraarticular injection of gadolinium. In these 27 patients, a total of 30 sulci were detected at arthroscopy. On retrospective MR review of both the conventional and gadolinium-enhanced studies, nine (75%) of the 12 anterosuperior sulci could be visualized. Ten (71%) of the 14 posteroinferior sulci were also identified. Neither of the two anteroinferior sulci could be seen. Both of the posterosuperior sulci were evident. Of the conventional MR studies, of a potential of 27, 18 (70%) were identified on conventional imaging. CONCLUSION: Sulci of the hip exist (22% of patients) and can be found at all anatomic positions (i.e., anterosuperior, anteroinferior, posterosuperior, and posteroinferior) of the hip. These sulci can be visualized on MRI with an accuracy of 70% using a nongadolinium technique.

MR imaging of post-traumatic articular cartilage injuries confined to the femoral trochlea. Arthroscopic correlation and clinical significance.

OBJECTIVE: To assess and describe post-traumatic articular cartilage injuries isolated to the trochlear groove and provide insight into potential mechanism of injury. MATERIALS AND METHODS: We retrospectively evaluated MR imaging findings of all knee MRIs performed at our institution over the last 2 years (2450). Thirty patients met the criteria of a cartilage injury confined to the trochlear groove. In 15 cases, which were included in our study, arthroscopic correlation was available. Each plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. Any additional pathological derangement was documented and information about the mechanism of injury was retrieved by chart review. RESULTS: In all cases the cartilaginous injury was well demonstrated on MRI. In 13 patients additional pathological findings could be observed. The most frequently associated injury was a meniscal tear in nine patients. In eight cases, the arthroscopic grading of the trochlear injury matched exactly with the MRI findings. In the remaining seven cases, the discrepancy between MRI and arthroscopy was never higher than one grade. In 13 out of 15 of patients trauma mechanism could be evaluated. Twelve patients suffered an indirect twisting injury and one suffered a direct trauma to their knee. CONCLUSION: The findings of this study demonstrate that MR imaging allows reliable grading of isolated injury to the trochlear groove cartilage and assists in directing surgical diagnosis and treatment. These injuries may be the only hyaline cartilage injury in the knee and meniscal tears are a frequently associated finding. Therefore, it is important to search specifically for cartilage injuries of the trochlear groove in patients with anterior knee pain, even if other coexistent pathology could potentially explain the patient's symptoms.

Shoulder imaging in athletes.

Shoulder pain and injuries are common in athletes. Overhead athletes, in particular, place great demands on the shoulder and supporting structures. Magnetic resonance (MR) imaging is well suited to evaluation of the osseous structures and soft tissues of the shoulder and plays an important role in evaluation of shoulder pain in athletes. Primary extrinsic impingement is well evaluated on MR imaging as are the less common posterior superior glenoid impingement and subcoracoid impingement. Rotator cuff tendinosis as well as partial- and full-thickness tears are frequently encountered in the athletic shoulder. The biceps tendon and rotator interval capsular structures are important sources of shoulder pain. Glenohumeral instability that results from a traumatic event or atraumatic multidirectional recurrent instability is assessed. The biceps labral complex is a source of considerable anatomic variability and pathology.

Use of the modified three-point Dixon technique in obtaining T1-weighted contrast-enhanced fat-saturated images on an open magnet.

The purpose of this study was to investigate the modified three-point Dixon technique as a method for obtaining fat-saturated T1-weighted sequences before and after intravenous gadolinium administration using an open MR imaging scanner. A preliminary experiment using an oil/gadolinium phantom was performed on a 0.35-T open magnet and an advanced 1.5-T unit. Fat saturation was achieved at 1.5 T using a frequency selective presaturation technique and a modified three-point Dixon technique on the low-field scanner. The modified three-point Dixon sequence was then evaluated in ten patients undergoing MRI examinations of the spine with gadolinium enhancement to determine image characteristics and diagnostic potential. The phantom study demonstrated a homogenous suppression of signal from oil and a good distinction between fat and a gadolinium chelate on the 0.35-T unit comparable to that on the 1.5-T scanner. By applying the modified three-point Dixon technique on the open-magnet, the distinction between fat and gadolinium dimeglumine was rated as very good in 139 and good in 17 axial slices in a total of 156 images. No image was rated as difficult or not possible. Motion artifacts that hampered the reading were detected in the lower cervical spine due to respiratory movement in four (3% of all) images. The modified three-point Dixon technique provides the combination of gadolinium enhancement with fat saturation on an open magnet. Early clinical applications appear promising.

Impingement syndrome of the ankle following supination external rotation trauma: MR imaging findings with arthroscopic correlation.

Our objective was to identify MR imaging findings in patients with syndesmotic soft tissue impingement of the ankle and to investigate the reliability of these imaging characteristics to predict syndesmotic soft tissue impingement syndromes of the ankle. Twenty-one ankles with chronic pain ultimately proven to have anterior soft tissue impingement syndrome were examined by MR imaging during January 1996 to June 2001. The MR imaging protocol included sagittal and coronal short tau inversion recovery (STIR), sagittal T1-weighted spin echo, axial and coronal proton-density, and T2-weighted spin-echo sequences. Nineteen ankles that underwent MR imaging during the same period of time and that had arthroscopically proven diagnosis different than impingement syndrome served as a control group. Fibrovascular scar formations distinct from the syndesmotic ligaments possibly related to syndesmotic soft tissue impingement were recorded. Arthroscopy was performed subsequently in all patients and was considered the gold standard. The statistical analysis revealed an overall frequency of scarred syndesmotic ligaments of 70% in the group with ankle impingement. Fibrovascular scar formations distinct from the syndesmotic ligaments presented with low signal intensity on T1-weighted images and remained low to intermediate in signal intensity on T2-weighted MR imaging. Compared with arthroscopy, MR imaging revealed a sensitivity of 89%, a specificity of 100%, and a diagnostic accuracy of 93% for scarred syndesmotic ligaments. The frequency of scar formation distinct from the syndesmotic ligaments in patients with impingement syndrome of the ankle was not statistically significantly higher than in the control group. In contrast to that, anterior tibial osteophytes and talar osteophytes were statistically significantly higher in the group with anterior impingement than in the control group. Conventional MR imaging was found to be insensitive for the diagnosis of syndesmotic soft tissue impingement of the ankle. Fibrovascular scar tissue distinct from syndesmotic ligaments is suggestive for the diagnosis of soft tissue impingement, but the reliability of these findings is still questionable.

Perthes lesion (a variant of the Bankart lesion): MR imaging and MR arthrographic findings with surgical correlation.

OBJECTIVE: The aim of this study was to evaluate the use of MR imaging in the characterization of the Perthes lesion by correlating MR findings with findings at arthroscopy. CONCLUSION: The use of a combination of axial and abduction-external rotation position sequences on MR images can be helpful in the diagnosis of a Perthes lesion. A fluid-filled joint with capsular distension, caused by either a large amount of effusion or MR arthrography, was found to be helpful in outlining Perthes lesions. Adding the abduction-external rotation position to the protocol in patients in whom Perthes lesion is suspected will increase diagnostic accuracy and may reveal a Perthes lesion not visible on axial images, as was the case in 50% of the patients in our series.