Stiffness post-total knee replacement: a proof of principle study investigating the effect of gene expression analysis of markers of fibrosis: Gene expression of stiffness post-TKR

BACKGROUND: To establish proof of principle of a link between phenotypic expression and stiffness after TKR. METHODS: From 100 patients, genetic expression of markers of fibrosis were performed for 15 synovial samples from patients categorised as ‘best post-operative range of movement (ROM)’ and 15 samples from patients with ‘worst ROM’. These markers included Matrix Metalloproteinases (MMPs), A Disintegrin and Metalloproteinases with Thrombospondin (ADAMTs) and Tissue Inhibitors of Matrix Metalloproteinases (TIMPs). Genetic marker data were compared to Oxford Knee Scores (OKS) and Pain Catastrophizing Scores (PCS). RESULTS: Quantitative markers for gene expression demonstrated more outliers in stiff compared to non-stiff knees, suggesting a greater imbalance in pro- and anti-fibrotic markers in stiff knees. Whilst there was a significant difference in the range of post-operative knee flexion (p=0.001) and extension (p=0.001), there was no statistically significant difference between stiff and non-stiff knees in pre-operative or post-operative OKS (p≥0.06). There was no difference in the individual components of the individual PCS score items nor the PCS total scores when stiff and non-stiff knees were compared (p>0.05). CONCLUSION: Biological factors, namely gene expression of MMPs, TIMPs and ADAMTs, may contribute towards post-TKR stiffness. This now warrants further investigation to better understand this relationship based on larger, multi-centre, cohorts.