Total hip arthroplasty in Italy: an observational, population-based study on surgical volume growth from 2001 to 2023 and forecasts until 2050 with six different statistical models

Background: The number of total hip arthroplasty (THA) procedures has been steadily increasing worldwide, driven by aging population, improvements in surgical techniques and implant design. This study aimed to analyze the temporal trends of elective THA in Italy since 2001-2023 and forecast THA volumes up to 2050 to provide insights for healthcare planning. Materials and methods: International Classification of Diseases, 9th Revision, Clinical Modification (ICD9-CM) coding system was used to extract records of interest (elective THA) from the Italian National Hospital Discharge Record database. Six statistical models were applied to forecast future THA volumes: logistic regression; Poisson regression; logarithmic regression; inverse/power regression; Poisson log-normal regression; and hierarchical Poisson regression with temporal effects (HPTE). Model performances were assessed by using error metrics and internal validation on the basis of a rolling-origin approach. An out-of-sample validation was conducted to ensure a robust assessment of forecasting reliability. THA volume forecasts were provided with 95% prediction intervals. Results: A total of 1,318,400 records for primary elective THAs performed in Italy since 2001-2023 were analyzed. The number of THAs increased by approximately 80%, rising from 68.270 in 2001 to 122.777 in 2023. Among the tested models, HPTE generally showed the best fitting and forecasting performances. By using the HPTE model, the forecasts showed an increase in THA volumes up to a maximum rate ratio (RR) of 1.3 (PI95%: 1.1-1.4) in terms of RR in 2036, then decreasing to a RR equal to 1.2 (PI95%: 1.1-1.4) by 2050 with respect to 2019. Conclusions: Our findings forecast a steady increase between 10% and 40% in THA, driven by demographic and epidemiological trends. These projections are essential for anticipating future surgical demand and guiding healthcare system planning. Without adequate investment and strategic planning, rising volumes may strain service capacity and sustainability. Level of evidence: population based study, level 1 evidence.