Abstract
Background
Hyperlaxity is associated with a high incidence of shoulder dislocations. Collagen V regulates the diameter of fibrils of the abundant collagen type I. Decorin and biglycan are members of the small leucine rich proteoglycans(SLRP's)family and play important roles in the regulation of collagen fibrillogenesis. The aim of this study was to identify if there was a link in hyperlaxity, capsule strength, collagen V and SLRP's expression.
Methods
Data was collected for 10 patients undergoing open shoulder stabilization for recurrent instability. Beighton score was used to assess hyperlaxity. Localization of Collagen V and SLRP's was studied by immunohistochemical staining of paraffin embedded sections of shoulder capsule. Grading of the stain was done on a 0-4 scale(0=no staining and 4=strong staining>50% of the slide)by three observers. Shoulder capsules were mounted on a material testing system and vertical load was applied to reach yield.
Results
The mean force required for yield in 15 shoulder capsules was 45N(17-78). Data was analysed for Group A(weak group) with yield<45N(8 specimens) and Group B(strong group)with yield>45N(7 specimens). The mean age was 26 years and all were male. The mean force for group A was 31N(17-41) and group B was 59N(45-78). The mean Beighton score for group A was 1.9(0-4) and Group B was 2. 2 specimens in Group A had Beighton score>4 as compared to 0 in Group B, indicating hyperlaxity. The mean grading of collagen V expression in synovial surface was 2.6,Blood vessels(BV)1.6 and extracellular matrix(ECM)1.9 in Group A and 4,3.1 and 2.6 respectively in group B. The mean grading of decorin expression for shoulder capsule was 2.7 in Group A and 3.3 in group B. The mean grading of Biglycan expression in synovial surface was 2,BV 2 and ECM 2.9 in Group A and 2,2.5 and 4 respectively in group B.
Conclusions
We found that weaker capsule specimen(group A)had higher incidence of hyperlaxity. Decorin and biglycan expression in ECM and Collagen V expression in synovial surface, BV and ECM of shoulder capsule was higher in group B(strong group). This study shows a link between hyperlaxity, strength, Collagen V and SLRP's expression in shoulder capsule.
