Diagnostic value of US, MR and MR arthrography in shoulder instability
Introduction
Shoulder instability represents a common condition primarily affecting young active people and especially athletes. It occurs when the humeral head is forced out of the glenoid fossa. This can be the result of a sudden injury or from overuse activities of the shoulder joint. Once the soft tissues (ligaments, tendons, and muscles) supporting the shoulder become loose or torn, the shoulder joint becomes prone to dislocations. Chronic shoulder instability is defined as the persistent inability of the soft tissues to keep the humeral head congruent into the glenoid fossa.1, 2, 3, 4
The stability of the glenohumeral joint depends on the stabilizing musculotendinous structures of the rotator cuff and most of the muscles of the shoulder girdle. The glenoid labrum also plays an important role in shoulder stability by providing the fibrous attachment of the glenohumeral ligaments and capsule to the glenoid rim.5
According to the injured anatomical structures, several distinct pathological conditions have been described. Because of the complexity of the anatomy of the shoulder joint, the diagnosis and management of these conditions can be challenging.
SLAP lesion represents an injury of the superior labrum, at the point where the tendon of the biceps muscle inserts on the labrum and extends anteriorly and posteriorly. It is diagnosed when contrast media interposed between superior and anterior glenoid labrum oriented laterally towards the biceps brachii tendon insertion.4 Type I is characterized by marked fraying of the free edge of the superior labrum. Type II occurs when the labral-bicipital complex is avulsed from the glenoid. Type III is a displaced bucket handle tear of the superior labrum with an intact biceps anchor and Type IV is a bucket handle tear of the superior labrum, with extension into the fibers of the biceps tendon.
The classic Bankart lesion is defined as a defect of the capsulolabral complex at the site of the inferior glenohumeral ligament (Figure 1). Its variants include: Perthes lesion (Figure 2), anterior labral periosteal sleeve avulsion (ALPSA) (Figure 3), humeral avulsion of the glenohumeral ligament (GLAD) (Figure 4), bony humeral avulsion of the glenohumeral ligament and the floating anteroinferior glenohumeral ligament (HAGL). Any of these lesions can be associated with glenolabral articular disruption.6
In Perthes lesions, the scapular periosteum remains intact but is stripped medially resulting in incomplete avulsion of the labrum from the glenoid margin, whereas in Bankart lesions, the scapular periosteum is torn. In ALPSA lesions, the labrum, capsule and ligaments are medially displaced, inferiorly rotated and fibrosed. In GLAD lesions the anterior glenoid labrum is partially torn with an adjacent articular cartilage chondral defect in clinically stable patient. Hill-Sachs lesion is an impacted fracture of dorsolateral aspect of the humeral head with/without changes in intensity of adjacent bone (Figure 5). The criteria for defining a ligamentous lesion are: rupture, thickness and changing of intensity of the ligament.
Many methods have been described in the literature for diagnosing shoulder pathology. These include standard radiograms, conventional arthrotomography, ultrasound, CT arthrography and MR imaging.7
For the evaluation of rotator cuff injuries, ultrasound (US) and magnetic resonance imaging (MRI) are considered to be the most accurate. MRI however, is more universally accepted although it can be limited in evaluating partial tears of the rotator cuff.8, 9 On the other hand, labral capsular ligamentous complex lesions can be diagnosed by MRI but subtle lesions are better visualised after intra-articular injection of contrast media and subsequent distension of capsule.10, 11, 12, 13, 14, 15, 16
The aim of our study was to compare US, conventional MRI and MR arthrography findings in patients with anterior shoulder instability and with a clinical diagnosis of labral capsular ligamentous complex lesion. At the same time we evaluated the accuracy of MR arthrography in the diagnosis of this lesion.
Section snippets
Materials and methods
After approval of the local Ethics Committee, our department's Trauma Registry from July 2008 up to February 2012 was retrospectively reviewed to identify all eligible patients. Eligibility criteria included: 1) history of acute or chronic shoulder instability (more than three dislocations over a period of more than two months); 2) diagnosis of labroligamentous lesion.
Details including patient age, gender, mechanism of injury, clinical examination, finding of imaging modalities (standard
Results
A total of 200 consecutive patients who met the inclusion criteria were included in our study. The mean age was 39 years (range 15 to 83 years); 147 were male and 133 involved the right shoulder. Chronic instability was documented in 133 patients, whereas acute instability was documented in 67 patients.
All patients had plain radiographs, US scans and conventional MRIs.
Plain radiographs were reported as normal in all patients, whereas the US scans revealed rotator cuff ruptures in 80 patients
Discussion
For the evaluation of the rotator cuff tears, both MRI and ultrasound are regularly used in clinical practice. Kelly et al. reported that US and MRI are both useful in diagnosis of rotator cuff tears, although no method was considered superior.22 In our study we didn't find any statistically significant difference between these techniques in diagnosing incomplete rotator cuff rupture; however, there was a statistically significant difference with regards to partial rotator cuff rupture. When we
Conclusion
The US scan is a valuable diagnostic technique for rotator cuff complete or incomplete ruptures. For evaluating Hill-Sachs lesions or bony Bankart lesions, MRI is more accurate. In the case of labral capsular ligamentous complex lesions, MR arthrography is superior.
Conflict of interest
All authors declare they have no conflicts of interest.
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