10/22/2022
Pathophysiology of Frozen Shoulder: “Most authors now accept that frozen shoulder is a disease characterised by fibroblast proliferation, activation and matrix remodelling
- (Figure).” https://journals.sagepub.com/doi/abs/10.1177/1758573220965870?journalCode=sela
👉 “The resulting lesion being the production of a stiff, contracted, diffuse extracellular matrix (ECM) production with the overproduction of densely packed collagen fibrils.”
https://onlinelibrary.wiley.com/.../j.1758-5740.2009.00007.x, https://pubmed.ncbi.nlm.nih.gov/17673588/, https://pubmed.ncbi.nlm.nih.gov/20110457/, https://pubmed.ncbi.nlm.nih.gov/19214689/
👉 “More recently it has been suggested that this fibroblast activity represents a pro-resolving phenotype.” https://pubmed.ncbi.nlm.nih.gov/30668880/
“While previously debated, there is now a relative consensus that this involved immune cell regu-lation, including mast cells, macrophages, T-cells and B-cells.” https://onlinelibrary.wiley.com/.../j.1758-5740.2009.00007.x, https://pubmed.ncbi.nlm.nih.gov/17673588/
👉 “Many studies have identified evidence of elevated cytokine expression, in particular interleukin (IL)-1b, tumour necrosis factor-a (TNF-a) and IL-6 and to a lesser extent IL-8.”
https://pubmed.ncbi.nlm.nih.gov/21472067/, https://pubmed.ncbi.nlm.nih.gov/22999851/, https://pubmed.ncbi.nlm.nih.gov/28676856/
👉 “Other authors have identified abnormalities of transforming growth factor b (TGF-b), platelet-derived growth factor-b, cyclooxygenase-2 and vascular endothelial growth factor signalling.”
https://pubmed.ncbi.nlm.nih.gov/22999851/, https://pubmed.ncbi.nlm.nih.gov/9246090/, https://pubmed.ncbi.nlm.nih.gov/16990020/
👉 “Matrix metalloproteinases (MMP) dysregulation has been evidenced by many groups and of note a reduction of MMP-1, increased Tissue inhibitors of metalloproteinases (TIMP-1) and altered MMP1:TIMP-1 ratios.” https://pubmed.ncbi.nlm.nih.gov/23604641/
👉 “Other research has implicated a role for alarmins, neoinnervation and advanced glycation end-product activation.” https://pubmed.ncbi.nlm.nih.gov/29190116/, https://pubmed.ncbi.nlm.nih.gov/26776943/
🩻 “Structural changes during frozen shoulder” (Millar et al. 2022, https://pubmed.ncbi.nlm.nih.gov/36075904/)
👉 a | “The healthy capsule is collagenous in structure, composed primarily of dense type I collagen and elastic fibre bundles with limited blood vessels and nerve fibres. The main cell type within this membrane is the fibroblast, which maintains capsule health by producing extracellular matrix (ECM) proteins that provide a supportive yet flexible structure.”
👉 b | “In frozen shoulder, there is fibrosis and thickening of the connective tissue membrane as well as the adjacent synovial membrane.”
👉 c | “Fibroproliferation results in an increased number of fibroblasts producing more ECM proteins, resulting in a dense and poorly organized fibrillar structure. These fibrotic changes are accompanied by inflammation, neoangiogenesis and neoinnervation. The consequence is a reduced joint volume and increased stiffness of the capsule, causing restricted movement and pain.“
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