Understanding knee arthroscopy : biomarkers, pain and socioeconomic determinants

Abstract

The overall aim of this thesis was to investigate arthroscopic knee surgery in Sweden at both an individual and a societal level. The vision is to enhance patient care, improve working conditions for healthcare personnel, and reduce societal costs by simplifying the selection of patients who benefit from arthroscopic knee-surgery, and optimizing their pain management. To achieve this, it is necessary to understand the characteristics of patients who undergo surgery, as well as those who do not. Key questions include: Who receives arthroscopic knee surgery in Sweden? Are there socioeconomic or regional differences in patient characteristics and access? Among those who undergo surgery, who benefits from the procedure? What factors associated with postoperative pain may predict an extensive use of analgesics? Who will require more postoperative healthcare, and what preventive strategies can be implemented? In an attempt to address these questions, the thesis combines clinical studies involving measurements of synovial metabolites with epidemiological studies based on nationwide Swedish registers.Study I investigated whether local external cooling and compression of the surgical field following arthroscopic knee surgery influence inflammatory and metabolic markers in the synovial membrane. A randomized controlled trial was conducted among otherwise healthy patients undergoing arthroscopic knee surgery, with half allocated to cooling and compression. Concentrations of prostaglandin E2 (PGE2), glucose, lactate, glycerol and glutamate as well as ethanol exchange ratios indicating blood flow, were measured. In parallel, intra-articular temperature and patient-reported pain (VAS) were reported. Cooling and compression significantly lowered the temperature in the operated knee, which positively correlated with PGE2 levels. This suggest that cooling reduces inflammation by lowering PGE2 concentration. A lower metabolic rate of the synovial tissue could also be seen in the form of lactate level stability.Study II aimed to identify determinants of postoperative pain after arthroscopic knee surgery through a cross-sectional cohort study. Synovial tissue metabolites (PGE2, glucose, glycerol) were analyzed using microdialysis together with variables including age, sex, weight, length, BMI and smoking status. Postoperative pain was assessed using a visual analogue scale (VAS), with ≥ 4 defined as higher pain. No synovial metabolites were significantly associated with pain levels. However, patients reporting higher levels of pain were younger (p = 0.04), had lower body weight (p = 0.02), and a lower BMI (p = 0.04) and were more often smokers (p = 0.02). Multinomial logistic regression confirmed higher pain in smokers (p = 0.01) and younger patients (p = 0.02). Longer surgical duration was also significantly associated with increased pain (p = 0.007). These findings highlight individual factors supporting more personalized and patient centered pain management strategies for patients treated in an outpatient setting.Study III investigated national trends in knee arthroscopies in Sweden between 2002 and 2016. Using the Swedish Hospital Discharge Register (SHDR) a nationwide cohort consisting of all patients above 18 years of age undergoing arthroscopic surgery was created. Patient demographics and regional differences were mapped as well as patients with osteoarthritis (OA) going through knee arthroscopy. A total of 241,055 knee arthroscopes were identified. There was a marked decline in arthroscopy rates over time, with incidence falling from 247 to 155 per 100,000 inhabitants. This downward trend was consistent in all age groups, irrespective of sex, and among patients with osteoarthritis. More men (60%) than women (40%) underwent surgery. Half of all knee arthroscopies in the study were performed in metropolitan regions.Study IV assessed socioeconomic status (SES) and access to arthroscopic knee surgery using a retrospective registry-based nationwide population cohort in Sweden. Linking registry data from Statistics Sweden (SCB), the Swedish National Board of Health and Welfare's Patient Register (NPR), and the Longitudinal Integrated Database or Health Insurance and Labor Market Studies (LISA), the study evaluated whether socioeconomic gradients influenced the likelihood of receiving surgery. A total of 799,018 patients with knee ailments between 2001 and 2019 (before the COVID-19 pandemic) were included in the analyses. Linear regression models showed that women had a lower probability of receiving surgery compared with men with an absolute lower probability of 1.71 (16.7% relative difference). A clear socioeconomic gradient was observed: individuals in the highest income group had a 2.77 higher probability of surgery (33% relative difference).Both income and education, individually and combined, were significantly associated with a higher likelihood of undergoing arthroscopy.These results demonstrate sex disparities and that socioeconomic status influences access to arthroscopic knee surgery in Sweden.List of scientific papersI. Stålman A, Berglund L, Dungner E, Arner P, Felländer-Tsai L. Temperature Sensitive Release of PGE2 and Diminished Energy Requirement in Synovial Tissue with Postoperative Cryotherapy: A Prospective Randomized Study After Knee Arthroscopy J Bone Joint Surg Am. 2011; 93:1961-8. https://doi.org/10.2106/jbjs.j.01790II. Berglund L, Stålman A, Dungner E, Qureshi A, Kumlin M, Felländer-Tsai L. Younger Patients and Smokers Report a Higher Level of Pain After Knee Arthroscopy: A Clinical and Experimental Study Including Synovial Metabolism Knee Surgery, Sports Traumatology, Arthroscopy (2019)27:471-477. https://doi.org/10.1007/s00167-018-5125-xIII. Berglund L, Liu C, Adami J, Palme M, Qureshi A, Felländer-Tsai L. Decreasing Incidence of Knee Arthroscopy in Sweden Between 2002 and 2016: A Nationwide Register-Based Study. Acta Orthopaedica 2023;94:26-31. https://doi.org/10.2340/17453674.2023.7131IV. Berglund L, Felländer-Tsai S, Marcano A, Anderson E, Gerdin Wärnberg M, Qureshi A, Garland A, Palme M, Adami J, Felländer-Tsai L. To Operate or Not to Operate - The Socioeconomic Gradient in Knee Arthroscopies in Sweden. A Nationwide Cohort Study of Horizontal Inequity. [Submitted]