Development of a prognostic risk score for pin tract infection in definitive external fixation: a prospective cohort study

Pin tract infection (PTI) is one of the most frequent complications of external fixation and can lead to pain, osteolysis, loss of fixation, and prolonged treatment. Although several studies have described prognostic variables for PTI, no validated prognostic models or risk scores are currently available to estimate individual patient risk. Socioeconomic and behavioral factors may influence hygiene routines, access to antiseptics, and adherence to care instructions, yet these variables are rarely incorporated into models that may help identify patients at higher risk. This study aimed to develop a preliminary prognostic risk score for PTI in patients treated with external fixation using socioeconomic, behavioral, and clinical prognostic variables. Among 1,220 patients admitted with traumatic limb fractures, 417 required surgical stabilization. External fixation was commonly used for tibial fractures. A total of 119 patients with external fixators attended follow-up visits and agreed to participate in interviews. Four were excluded (one aged < 18 years, one with an upper extremity fixator, and two with congenital deformities), resulting in a final sample of 115 adults treated with standard external fixation for ≥ 2 weeks. Interviews were conducted during routine follow-up visits over a two-year period. The primary outcome was PTI, defined as erythema, secretion, and pain requiring topical or oral antibiotics (Checketts–Otterburn Grade 2). Secondary variables included socioeconomic and behavioral factors such as smoking, alcohol consumption, diet, education level, and hygiene practices. Candidate prognostic variables were evaluated using Cox proportional hazards regression and combined into a preliminary prognostic risk score. Discrimination of the prognostic model was assessed using time-dependent area under the receiver operating characteristic curve (AUC). Among 115 patients (mean age 39 ± 14.5 years; 83% male), 33 (29%) experienced complications, including 21 (18%) PTIs. The final prognostic model retained five predictive variables for subsequent PTI: low education level, chronic disease, use of saline for pin site disinfection, male sex, and smoking. A prognostic risk score incorporating these variables demonstrated promising discrimination for stratifying PTI risk during the first year of follow-up (1-year AUC = 77.1% [SE 6.99]). A preliminary prognostic score based on patient-reported and clinical variables demonstrated promising discrimination for stratifying PTI risk in individuals treated with external fixation. Following external validation, this tool may support postoperative decision-making, guide targeted preventive strategies and help prioritize patient education and antiseptic access in resource-limited settings. Further validation in larger, multicenter cohorts is warranted.