After receiving approval from the institutional review board, we retrospectively identified two cohorts of patients who had undergone unilateral TKA from August 2018 to October 2020. The triamcinolone group included 50 patients from the previous randomized controlled study . After completion of the study, we added 52 patients to the dexamethasone group based on the same criteria. The inclusion criteria were (1) primary unilateral TKA for osteoarthritis of the knee and (2) age 55 to 90 years old. The exclusion criteria were patients with (1) a history of contralateral TKA within one year, (2) the administration of any glucocorticoids during the three months prior to the surgical procedure, (3) diabetes mellitus, (4) rheumatoid arthritis, (5) a history of knee surgery or knee injury for example high tibial osteotomy, meniscus repair, ligament reconstruction and so on (6) liver or renal failure (7) administration of any anticoagulant drug, and (8) preoperative deep venous thrombosis (DVT).
In the dexamethasone group, at the period from May 2020 to October 2020, a periarticular injection of 60 mL of physiological saline solution containing 10 mg dexamethasone, which has been confirmed to be an effective dose,  and 150 mg ropivacaine was administered during TKA.
In the triamcinolone group, at the period from August 2018 to May 2020, a periarticular injection of 60 mL of physiological saline solution containing 40 mg triamcinolone acetonide, which has been confirmed to be an effective dose,  and 150 mg ropivacaine was administered. The biological half-lives of dexamethasone and triamcinolone acetonide are 36 to 55 h and 18 to 36 h, respectively, and 40 mg of triamcinolone has an anti-inflammatory potency equivalent to 8 mg of dexamethasone [2, 14, 15].
All TKA procedures were performed under general anesthesia. A single-shot, echo-guided femoral nerve block consisting of 20 mL of physical saline solution containing 75 mg ropivacaine was performed for all patients before the surgical procedure. Two senior surgeons performed or assisted in all surgical procedures. A pneumatic tourniquet was inflated to 250 mmHg. Medial parapatellar arthrotomy was performed. An Attune prosthesis (Depuy, Warsaw, IN, USA) was implanted in all knees using cement. Just before the prosthesis was implanted, 20 mL of the mixture was injected into the posterior aspect of the capsule and the remaining 40 mL was injected into the synovium, periosteum, iliotibial band, and collateral ligaments. After capsule closure, all patients were administered an intra-articular injection of 2 g tranexamic acid in 20 mL of physiological saline solution to reduce blood loss. The tourniquet was released after the wound had been closed and the knee bandage had been wrapped. No drain was inserted in any cases.
Pain and nausea control were performed similarly in all patients. From the day after surgery, 1 g acetaminophen was taken orally 3 times a day. For the management of pain, an intramuscular injection of 15 mg pentazocine and transrectal administration of 25 mg diclofenac were given if the patient required rescue. For the management of nausea, an intramuscular injection of 10 mg metoclopramide was given if the patient requested it. All patients were allowed to walk with a walker on the day after surgery. The number of uses of rescue analgesia and metoclopramide was recorded for 24 h postoperatively. Pain scores at rest, pain scores during walking, and nausea scores were recorded using a 0-to-10 Numerical Rating Scale, with pain at rest recorded at 4, 8, 16, 24, 48, and 72 h and 7 days postoperatively; pain during walking at 24, 48, and 72 h and 7 days postoperatively; and nausea at 8, 24 and 48 h postoperatively. The number of patients who vomited within 24 h after surgery was recorded. Patient temperatures were measured every 6 h for 72 h after surgery, and patients who had a high fever over 38 °C at any point were recorded.
Demographic information, including the age, sex, body weight, height and operative time, were recorded. CRP and fasting blood glucose levels were determined within three weeks preoperatively. Fasting blood glucose levels were determined the morning after surgery. CRP levels were determined 24 and 48 h and 7 days postoperatively.
Based on the results of previous studies, [2, 16] an a priori power analysis was performed to detect a difference in pain score of 0.8 with the desired power of 0.90 and a significance level of 0.05. The required sample size was calculated as 40 for each arm of the study. Assuming a 10% exclusion rate, the minimum sample size was 44 in each group. We included over 50 patients in each group (Fig. 1).
All statistical analyses were performed using the SPSS software program (SPSS version 26.0; IBM, International Business Machines Corporation, Armonk, NY, USA). Student’s t-test was used to compare the age, body weight, height, operative time, CRP level, and fasting blood glucose level between the groups. The chi-square test was used to compare the sex, incidence of a postoperative fever, and incidence of vomiting between the groups. The Mann-Whitney U-test was used to compare the pain and nausea scores and number of times rescue analgesia and metoclopramide were used between the groups. For all parameters other than the pain score, a post hoc analysis was performed to confirm the power of the test with significant differences.