Study Design
This descriptive cross-sectional study was conducted from July to December 2020 at the orthopaedics ward of two tertiary hospitals in Lanzhou, China. The study was approved by the Medical Ethical Committee of Lanhzou University second hospital (Approval Number: 2020A-126).
Inclusion criteria: 1) have a diagnosis of primary knee osteoarthritis, 2) scheduled for primary unilateral TKA secondary knee osteoarthritis, 3) have the ability to speak, write, and understand Chinese language, 4)at least 18 years old, 5) informed written consent. Exclude criteria: 1) prior knee surgery or a scheduled for revision or unicondylar knee arthroplasty, 2) cognitive and/or neurological disorders that prevented patients from understanding the questionnaires and surveys, 3) complicated with other serious chronic diseases (e.g., cancer, heart failure, kidney failure).
Following study enrollment, every patients completed six questionnaires under the guidance of the well-trained investigators, at the first day of their arrival at the hospital, within prior to patient’s surgery. All the data were filled out by the patients themselves independently within 30 minutes, and the investigators were present throughout the visit if participants required explanation or clarification. Participants were verbally given unified guide about the questionnaires. A total of 370 structured questionnaires were distributed and ten of which were ultimately excluded due to incomplete or missing information. In total, 360 valid questionnaires were collected.
Dependent Measure
Pain catastrophizing
Pain catastrophizing was measured by the Chinese version of the Pain Catastrophizing Scale (PCS)[18]. The scale includs 13 items, which describe the thoughts and feelings that patients may experience when they are in pain. The scale was composed of three dimensions: rumination (4 items), magnification (3 items), helplessness (6 items). Patients rate their recent pain-related thoughts using a 5-point Likert scale range from 0 (“not at all”) and 4 (“all the time”). The PCS total score is calculated by summing the 13 items that varies from between 0 (no catastrophizing) and 52 (severe catastrophizing), a higher score indicating a higher perceived level of catastrophizing. A PCS score of 30 or more as a cut-off point for pain catastrophizing was proposed by Sullivan[13]. This cutoff was used in previous study with ≥16 representing a high degree of pain catastrophizing[19, 20]. Our study utilized a cutoff of ≥38 to represent a high degree of pain catastrophizing and which was based on a Chinese study[18], in that the PCS was linguistically translated and culturally adapted, and the meaning of the original version was sufficiently maintained by idiomatic translation.The the Chinese version of PCS has shown high internal consistency with Chronbach’s alpha reported to be 0.93 among patients with chronic pain.
Independent Measures
Sociodemographic information
The sociodemographic information including age, gender, weight, height, marital status, educational levels, type of residence, work status and pain durations.
Physical function
The SF-36 is a widely used generic scale consisting of 36 items in 8 sections to evaluate 8 different domains. The participants’ physical function was assessed by the physical function(PF) domain in the Chinese version of the SF-36[19]. The PF domain is composed of 10 items and is scored on a scale from 0 to 100, with higher scores representing better physical function.
Pain Intensity
Pre-operative keen pain intensity was measured by a Numerical Rating Scale (NRS), with with 0 representing no pain and 10 being worst imaginable pain. These pain scores reflected the participant’s either pain at rest or pain during activity.
Oxford Knee Score
The Chinese version of the Oxford Knee Score (OKS) is a selfreported joint-specific questionnaire of pain and function associated with the knee[21]. The scale is composed of 12 items on a 5-point Likert’s scale, of which the total score ranges from 0 to 48, with lower scores indicating better functional status.
Symptoms of anxiety and depression
The individual anxiety and depressive symptoms of the participants was evaluated by the Hospital Anxiety and Depression Scale (HADS), which is composed of two 7-item subscales, including anxiety and depression[22]. The responses for 14 items range from 0 to 3. The scores of the two subscales is calculated by the mean scores of the corresponding items for the scores ranging from 0 to 21. A score on subscale is classified into three categories: within the normal range (0-7), suspected anxiety/depression (8-10), and presence of anxiety/depression (≥11). The HADS is reliable and valid in Chinese populations, with Cronbach alpha coefficients for the two subscales of 0.76 and 0.79[23].
Optimism and pessimism
Otimism and pessimism were assessesed by the Chinese version of the Life Orientation Test-Revised (LOT-R)[24]. This scale consists of 10 items, which are divided into optimism (3 items), pessimism (3 items) and filler items (4 items). Subjects respond to each item using an 5-grade Likert Scale, ranging from 0 (not at all agreement) to 4 (very agreement). The two subscale scores can be calculated, and the total score is is the result of adding the optimism to the inverted pessimism score. The LOT-R has satisfactory psychometric properties (Cronbach’s alpha=0.78) for the measurement of otimism and pessimism.
Statistical Methods
Statistical analyses were performed using the SPSS 25.0 (IBM Corp., Armonk, NY, USA). Count data was presented as frequency and percentage (%), measurement data was described by means ± standard deviation (SD). Independent 2 samples t-test and ANOVA was used to compare the pain catastrophizing score in different demographic characteristics of the patients. Pearson correlation analysis was applied to analyze the correlation between variables. Multivariate linear stepwise regression analysis was utilised to assess the factors associated with pain catastrophizing. For all analyses, P<0.05 was regarded as statistically significant.