• Ahmed Jawhar, Desiree Brenner, Carolina De La Torre, Carsten Sticht, Udo Obertacke, and Norbert Ponelies.
• Department of Orthopaedics and Trauma Surgery, University Medical Center Mannheim of University Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany. ahmed.jawhar@umm.de.
• Eur J Trauma Emerg Surg. 2021 Feb 1; 47 (1): 233-240.

PurposePostoperative quadriceps muscle strength was lowered after tourniquet application during total knee arthroplasty (TKA). Furthermore, tourniquet application results in higher proteolytic activity within vastus medialis cells, without influence on the amount and function of mitochondria. The effects of the commonly utilized intraoperative tourniquet on gene expression within the human skeletal muscle cells are barely examined. The purpose of the present study was to analyze the gene expression within the skeletal muscle cells after tourniquet-induced ischemia to identify differential expressed genes (DEGs) and pathways.MethodsAs part of a randomized, controlled, monocentric trial (Clinical-Trials.gov NCT02475603) 20 patients, scheduled to undergo primary total knee arthroplasty (TKA), were included. Written informed consent was received and the patients were randomly assigned to Group A (TKA with tourniquet) (n = 10) and Group B (TKA without tourniquet) (n = 10). A muscle biopsie of (5 × 5 × 5 mm) 125 mm3 were obtained from the vastus medialis exactly 60 min after performing the surgical approach. After preparation of a muscle homogenate, RNA extraction was performed (RNeasy Plus Universal Mini Kit Qiagen) and RNA integrity (RIN) was determined (Agilent 2100 Bioanalyzer, RNA 6000 Pico Kit). Gene expression profiling was performed using a validated method (GeneChip™ Human Transcriptome Array 2.0; Affymetrix). Statistical analysis (SPSS-Version 24; SAS JMP10 Genomics, Version 6) included the number of significant DEGs (p < 0.05), the number of DEGs with relative difference > 25% and the number of significant pathway (p < 0.05). The serum C-reactive protein (CRP) and the white blood cell (WBC) count were also perioperatively measured. The protocol was approved by our Institutional Ethics Committee (File reference 2012-334N-MA).ResultsTourniquet application resulted in a total of 3555 (13.8%) statistically significant DEGs within vastus medialis cells. 76 DEGs (29 upregulated, 47 downregulated) revealed a relative difference of more than 25%. Statistically significant changes occurred in 59 (25.8%) of 229 analyzed pathways. Furthermore, there was no clinically meaningful difference between the groups with regard to CRP and WBC count.ConclusionsTourniquet induced ischemia results in significant changes of the gene expression within cells of vastus medialis including metabolism, genetic information processing and cellular processes. The identified altered expression of genes and pathways might serve as pharmacotherapeutical targets; although further research is needed to clarify the underlying biological processes.Clinical RelevanceThese findings add further knowledge and should raise the awareness of surgeons about the effects of tourniquet induced ischemia at the gene expression level. Additional high-quality research may be warranted to examine the short and long term clinical significance of the present data.Level Of EvidenceLevel I.

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