Risk factors analysis and the establishment of nomogram prediction model of hidden blood loss exceeding 800 mL after total hip arthroplasty

To identify risk factors for hidden blood loss (HBL) exceeding 800 mL after total hip arthroplasty (THA) and establish a nomogram prediction model to guide clinical interventions. A retrospective study included 235 patients from the West Coast Campus of The Affiliated Hospital of Qingdao University, as well as 157 patients from the other two campus of the same hospital, all of whom underwent initial total hip arthroplasty (THA) at The Affiliated Hospital of Qingdao University between May 2023 and February 2025. Perioperative parameters including patient demographics, pre-surgical indices, and postoperative metrics were rigorously documented. Hidden blood loss was determined by applying Gross’s formula. Lasso regression and other statistical methods identified independent risk factors. A nomogram was developed using R software and validated via Bootstrap validation and external validation. HBL > 800 mL (113 cases) occurred in 48.09% of the training set patients.Data analysis demonstrated Patients’ advancing age correlated with reduced HBL. Male patients were more likely to have elevated HBL than female ones. All patients had an increased risk of HBL if they had lower limb atherosclerosis, hypocalcemia, or greater trochanter osteoporosis.The nomogram underwent Bootstrap validation with 200 iterations, yielding an average AUC of 0.849 (95% confidence interval: 0.845, 0.852). The AUC under external validation was 0.795 (after smoothing) and the calibration curve showed acceptable agreement, demonstrating that the model has good discriminative ability. Younger age, male, hypocalcemia, lower limb atherosclerosis and greater trochanter osteoporosis may increase HBL risk. The nomogram provides a reliable tool for relatively preoperative risk stratification and personalized management.