Incidence and risk factors for surgical site infection after medial opening-wedge high tibial osteotomy using a locking T-shape plate.

Medial opening-wedge high tibial osteotomy (MOWHTO) is a well-established surgical method for treatment of isolated medial compartment osteoarthritis with varus deformity, but the surgical outcomes may be compromised by surgical site infection (SSI). This study aimed to investigate the incidence and the risk factors for SSI after MOWHTO. This retrospective study included consecutive patients who underwent MOWHTO for isolated medial compartment osteoarthritis with varus deformity in two tertiary referral hospitals from January 2019 and June 2021. Patients who developed SSI within 12 months of surgery were identified by inquiring the medical records for index hospitalisation, notes of after-discharge outpatient visits, or records of readmission for treatment of SSI. Univariate comparisons were performed to detect the differences between SSI and non-SSI groups, and multivariate logistic regression analysis was used to identify the independent risk factors. Six hundred sixteen patients with 708 procedures were included and 30 (4.2%) cases of SSI occurred, with 0.6% rate for deep SSI and 3.6% for superficial. Univariate analyses showed significant difference between groups in terms of morbidity obesity (≥32 kg/m ) (20.0% vs 8.9%), comorbid diabetes (26.7% vs 11.1%), active smoking (20.0% vs 6.3%), time from admission to operation (5.2 ± 4.0 vs 4.1 ± 3.0), size of osteotomy ≥12 mm (40.0% vs 20.0%), type of bone grafting and lymphocyte count (2.1 ± 0.5 vs 1.9 ± 0.6). However, in the multivariate analysis, only active smoking (OR, 3.4; 95% CI, 1.4-10.2), size of osteotomy ≥12 mm (OR, 2.8; 95% CI, 1.3-5.9) and allogeneic/artificial vs no bone grafting (OR, 2.4; 95% CI, 1.0-10.8) remained significant. SSI was not uncommon after MOWHTO, but the majority was superficial. The identified three independent factors, including smoking, size of osteotomy ≥12 mm and allogeneic/artificial bone grafting would help risk assessment and stratification, target risk factor modification and clinical surveillance, and inform patient counselling.