In the probabilistic sensitivity analysis, reducing periprosthetic joint infections was the preferred strategy in more than 99% of simulations, with a 95% CI for the net monetary benefit ranging from USD 239 to USD 295. In contrast, the 95% CI for the net monetary benefit for reducing early postoperative readmission was USD 94 to USD 129, and for aseptic loosening USD 150 to USD 185. The willingness-to-pay threshold did not significantly affect the results.
Historically, a primary focus of THA outcomes research has been focused on improving implant survivorship. However, with the advent of highly crosslinked polyethylene and lower rates of wear, osteolysis, and aseptic loosening, the relative importance of more short-term outcomes, such as periprosthetic joint infections and hospital readmissions, may have increased. We used predictive modeling to evaluate the effect of reducing short- and long-term complications of THA on lifetime cost and quality of life. The model suggests that reductions in the rate of periprosthetic joint infections may result in greater improvements in cost and quality of life compared with equivalent reductions in the rate of aseptic loosening, while reducing early postoperative readmissions had greater effect on cost. However, the savings associated with reductions in the rate of readmissions were more than offset by the greater improvements in quality of life associated with reductions in aseptic loosening as reflected in the net monetary benefit. There are several logical explanations for these results. First, although periprosthetic joint infections are not the most common complication after THA, they are associated with high monetary cost and a greater reduction in quality of life when compared with revisions for aseptic loosening. In addition, there is a natural time preference for early benefits over delayed benefits, known as discounting. The same phenomenon leads to a preference for late rather than early complications. The negative effect of early complications therefore is weighted more heavily in the model.
Our study has several notable limitations. As a model-based cost-effectiveness study, the accuracy of the results is limited by the accuracy of the model inputs. Because of the specific data points that were sought, we did not perform a systematic review for every variable. Nonetheless, we have attempted to assemble the best available literature to inform the model and used sensitivity analysis to account for uncertainty. Furthermore, despite a lack of research, decisions must be made regarding investment of research and development resources to reduce costs and improve patient quality of life after THA. As such, we would advocate for a quantitative, transparent approach to such decisions over a less systematic approach. Certain assumptions required extrapolation from the existing literature, such as the utility associated with successful two-stage revision THA for periprosthetic joint infections. However, there was no change in the preferred strategy (reduction in the rate of periprosthetic joint infections), even if the utility associated with successful aseptic and septic revisions was assumed to be equal during the sensitivity analysis. Similarly, we conservatively estimated the utility of readmission to be ½ of a primary operation, which may underestimate the health effect of a readmission. Our costs were obtained from our hospital cost-accounting system, which estimates direct costs of care using time-driven activity-based costing. As with any hospital cost accounting system, there are limits to how direct and indirect medical costs are measured, which affects the cost estimates used in our analysis. Furthermore, there may be a lack of generalizability in our cost estimates owing to regional variation. In addition, indirect nonmedical costs, such as missed work, travel time, and other societal costs are not captured.
We are not aware of other studies that have addressed research prioritization based on various strategies to improve the cost-effectiveness of THA for direct comparison with our study. However, several studies have highlighted the substantial costs associated with early complications and readmissions after surgery [16, 21]. Using the American College of Surgeons National Surgical Quality Improvement Program linked to Medicare claims, Lawson et al.  reported that reducing postoperative complications for the 20 most common surgical procedures by 5% would result in savings to Medicare of USD 31 million per year. In orthopaedic surgery. Whitehouse et al.  estimated that surgical site infections increased the overall costs of orthopaedic procedures threefold and doubled the rate of readmissions. Although these studies are difficult to directly compare with our investigation, they support the notion that early postoperative complications have a large effect on total healthcare costs.
By design, our investigation compared the effect of equivalent reductions of three common complications of THA rather than comparing specific strategies for reducing complication rates. Our results are meant to inform decision-making regarding resource allocation for quality improvement efforts. We believe our results support more emphasis on reducing short-term complications, such as periprosthetic joint infections and to a lesser degree, addressing the potential cost-savings associated with reductions in early postoperative readmission. Nonetheless, our model assumed all strategies result in a proportional reduction in the rate of failure, which may not be achievable. Furthermore, the investment necessary and effort needed to achieve equivalent reductions in each complication may be vastly different. As such, the results should be interpreted cautiously and only as a rough guideline of the potential return on investment when considering research prioritization in THA. Perhaps the most important implication of our study is the implied benefit of a joint replacement registry. Registries would allow for real-time monitoring of the complications that we have shown are likely to have the greatest overall effect on patient health and healthcare costs associated with THA. Although long-term studies evaluating differences in implant longevity always will have value, the importance of small differences in early postoperative complications cannot be underestimated.
We have developed a cost-effectiveness model that suggests that there may be greater improvements in quality of life and cost savings associated with THA with reductions in the rate of periprosthetic joint infections compared with equivalent reductions in the rate of aseptic loosening associated with improvements in implant longevity. In addition, although the net monetary benefit resulting from reductions in the rate of aseptic loosening is larger than an equivalent reduction in the rate of hospital readmission, the pure cost savings may be greater for reductions in readmission. These findings support the notion that greater investment in strategies to improve short-term outcomes, such as reducing periprosthetic joint infection rates, rather than efforts to enhance longterm implant survivorship may be warranted.
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