BACKGROUND: Although increased capsular volume has been implicated in shoulder instability, there is a paucity of clinical evidence to quantify the size of the capsule with specific instability conditions of the shoulder. HYPOTHESIS: Shoulder capsular area, as measured by magnetic resonance arthrography, is increased with specific patterns of shoulder instability. STUDY DESIGN: Cross-sectional study; Level of evidence, 4. METHODS: During an 8-month period, all patients with a diagnosis of anterior (n = 19), posterior (n = 14), or multidirectional (n = 13) instability of the shoulder and who were assessed with a magnetic resonance arthrogram were reviewed. A group of 10 control patients without clinical instability were also identified. The magnetic resonance arthrograms of all groups were randomly mixed, and 5 reviewers recorded measures of capsular length and area and determined labral abnormalities. The magnetic resonance arthrogram measurements were compared between groups, and interobserver agreement was determined. RESULTS: The cross-sectional area of the capsule was increased in patients with posterior (P = .017) or multidirectional instability (P = .021) versus controls, but not in patients with anterior instability. Additionally, the posteroinferior cross-sectional area was increased in patients with posterior (P = .001), multidirectional (P = .003), and anterior (P = .008) instability. In patients with a posterior labral tear, the mean axial (P = .043) and mean posteroinferior sagittal cross-sectional area (P = .011) was increased, but there were no differences in cross-sectional area for those with an anterior labral tear. The overall interobserver reliability was very good (correlation coefficient range, 0.68-0.94). CONCLUSION: Our results reinforce the concept that capsular elongation and laxity, either preexisting or acquired, play a role in certain instability conditions of the shoulder. Additional work is needed to determine how to correlate surgical decision making with the cross-sectional area measurements demonstrated in this study.
BACKGROUND: Although increased capsular volume has been implicated in shoulder instability, there is a paucity of clinical evidence to quantify the size of the capsule with specific instability conditions of the shoulder. HYPOTHESIS: Shoulder capsular area, as measured by magnetic resonance arthrography, is increased with specific patterns of shoulder instability. STUDY DESIGN: Cross-sectional study; Level of evidence, 4. METHODS: During an 8-month period, all patients with a diagnosis of anterior (n = 19), posterior (n = 14), or multidirectional (n = 13) instability of the shoulder and who were assessed with a magnetic resonance arthrogram were reviewed. A group of 10 control patients without clinical instability were also identified. The magnetic resonance arthrograms of all groups were randomly mixed, and 5 reviewers recorded measures of capsular length and area and determined labral abnormalities. The magnetic resonance arthrogram measurements were compared between groups, and interobserver agreement was determined. RESULTS: The cross-sectional area of the capsule was increased in patients with posterior (P = .017) or multidirectional instability (P = .021) versus controls, but not in patients with anterior instability. Additionally, the posteroinferior cross-sectional area was increased in patients with posterior (P = .001), multidirectional (P = .003), and anterior (P = .008) instability. In patients with a posterior labral tear, the mean axial (P = .043) and mean posteroinferior sagittal cross-sectional area (P = .011) was increased, but there were no differences in cross-sectional area for those with an anterior labral tear. The overall interobserver reliability was very good (correlation coefficient range, 0.68-0.94). CONCLUSION: Our results reinforce the concept that capsular elongation and laxity, either preexisting or acquired, play a role in certain instability conditions of the shoulder. Additional work is needed to determine how to correlate surgical decision making with the cross-sectional area measurements demonstrated in this study.
Authors: Jonathan M Frank; Simon Lee; Frank M McCormick; Mark Jordan; Bryce Austell; William Slikker; Michael J Salata; Shane J Nho Journal: Knee Surg Sports Traumatol Arthrosc Date: 2014-09-14 Impact factor: 4.342
Authors: Christoph Schaeffeler; Simone Waldt; Jan S Bauer; Chlodwig Kirchhoff; Bernhard Haller; Michael Schröder; Ernst J Rummeny; Andreas B Imhoff; Klaus Woertler Journal: Eur Radiol Date: 2014-03-13 Impact factor: 5.315