Hemiarthroplasty also had the highest reoperation rate in most age groups. Younger patients who underwent THA had a higher average reoperation rate over their lifetime than did those treated with ORIF, although once patients were 59 years old at the time of injury THA was followed by fewer total lifetime revisions than ORIF (Fig. 3-A). The patients who underwent ORIF were subdivided into those who had successful healing after the index surgery and those in whom the fracture failed to unite and required revision surgery. This analysis showed that patients between 40 and 65 years old in whom the fracture failed to heal after ORIF required an average of 1.9 additional operations throughout their lifetime, whereas those who underwent primary THA eventually required 0.4 operation on average (Fig. 3-B).
Hemiarthroplasty had uniformly inferior health outcomes. Results were similar between ORIF and THA in patients 40 to 65 years old, whereas THA began to have superior outcomes after the age of 65 (Fig. 4-A). Again, the results were subdivided according to the success of the primary ORIF, which showed that patients between 40 and 65 with successful fracture union after ORIF had utility outcomes that were, on average, 2.6% better than those after primary THA, whereas those in whom the ORIF failed had, on average, outcomes that were 11.6% worse than those following THA (Fig. 4-B).
When comparing both cost and quality of life, we found that THA became cost-effective after the age of 54 years for patients with no medical comorbidities, after 47 years old for patients with mild comorbidity, and after 44 years old for patients with multiple comorbidities. Using an alternative ICER threshold of $50,000/QALY changed those threshold ages by <1 year.
The model was highly sensitive to the failure rate of fracture-healing after ORIF and to the health utility after successful ORIF or after THA. Figure 5 shows the relationship among patient age, ORIF failure rate, and medical comorbidity level. The results were moderately sensitive to the revision rate of primary THA and were relatively insensitive to the remaining variables.
Probabilistic statistical analysis conducted to evaluate the stability of the conclusions showed that hemiarthroplasty was never the preferred option under any modeled circumstances. The conclusions derived from comparing ORIF with THA were stable for patients <45 years old (ORIF was generally the preferred strategy) or >65 years old (THA was the preferred strategy). For patients 45 to 65 years old, THA and ORIF had nearly equivalent cost-effectiveness (Fig. 6, with full acceptability curves shown in the Appendix).
Displaced femoral neck fractures in patients younger than 65 years of age can be challenging to manage. Case series have shown the failure rates of ORIF to be as low as 8%9 or as high as 35%48 in this patient population, and revision surgery can be challenging12,13,15. Similarly, the 10-year survival rate of THA in a younger population has been shown to be as high as 100%49 and as low as 75%50. When uncertainty about outcomes makes decision-making difficult, quantitative analyses can help objectify risks, define areas where there is more or less ambiguity, and be used to support clinical decision-making44. By defining the critical variables that determine outcomes, we can add structure and evidence-based recommendations to the decision process.
The results of this study showed that both ORIF and THA can be cost-effective options for patients who sustain a displaced femoral neck fracture between 40 and 65 years of age, whereas hemiarthroplasty has inferior results. Although ORIF and THA have similar health outcomes on average, patients who undergo ORIF and have fracture healing have slightly better outcomes than those who undergo THA, with considerably lower costs, while those in whom the fracture fails to heal after ORIF have notably worse outcomes and a higher reoperation rate than patients treated with THA. The success rate of ORIF is a function of (1) patient factors such as injury mechanism, medical comorbidity, and fracture pattern; (2) surgeon factors, including comfort with performing complex ORIF and primary THA; and (3) system factors, including operating room resources/accessibility and availability of specialist surgeons trained in either arthroplasty or advanced fracture fixation.
Our study suggests that the transitional age at which THA should be considered is 54 years old for healthy patients, 47 years for those with mild comorbidity, and 44 years for those with multiple comorbidities. However, rather than specifying treatment decisions, it is our hope that this study can add clarity to the conversation between patient and surgeon. The surgeon can evaluate the patient’s injury characteristics and comorbidities to estimate the likelihood of ORIF resulting in successful healing and use that estimate to counsel the patient about treatment options through a process of shared decision-making.
This study is strengthened by the body of high-quality literature describing outcomes after both arthroplasty and ORIF, which improves the strength and reliability of the conclusions. Furthermore, this is a clinical scenario that is amenable to well-established modeling techniques, which facilitate testing of areas where clinical probabilities are less defined and allow quantification of uncertainty. The use of the NIS database analysis adds context to these conclusions, showing that more than 1 of 10 femoral neck fractures occur in patients in the age group evaluated in this study and that this truly is a transitional age group for which decision-making is challenging.
There are several limitations and caveats to this analysis. When interpreting these results, it is important to recognize that the conclusions are sensitive to several variables. Whenever possible, we attempted to improve confidence in the results by obtaining critical values from only the highest-quality evidence (usually from national clinical registries with data from thousands of patients), and we used literature review when registry data were not available. For example, we relied on systematic review to estimate failure of ORIF and modeled failure to occur immediately postoperatively, although in reality these failures are likely spread out throughout a 1 to 3-year postoperative period. We included data from studies with follow-up as long as 10 years. However, there are limited data on ORIF failure rates beyond that point, so it is possible that our model is overestimating the long-term success rate of ORIF. For this variable, and other areas where there was uncertainty and registry data were not available, we used multiway sensitivity analysis to quantify that relationship to allow recommendations to be adjusted for alternate clinical scenarios. Additionally, our cost estimates required the use of cost-to-charge ratios and were obtained from the HCUP database, which relies on ICD-9-CM diagnosis coding; such coding does not distinguish between displaced and nondisplaced femoral neck fractures. Although this decreases the precision of the cost estimates, the net cost estimates for the 3 primary procedures were relatively similar, and the overall conclusions were relatively insensitive to the initial procedure costs. As a result, we believe that, despite these areas of uncertainty, this model represents valid evidence-based recommendations based on the highest-quality data available.
It is also important to clarify the clinical scenario that was being evaluated. This analysis focused on patients 40 to 65 years old, for whom the operative decision is between ORIF and THA and a failure of ORIF would most likely be treated with conversion to THA. The decision between THA and hemiarthroplasty in a more elderly population was outside the scope of this analysis and has already been extensively analyzed23,25. Additionally, there is also a younger patient population for whom a salvage procedure such as valgus osteotomy would be considered following failed ORIF; that is a much more complex and patient-specific decision process.
In conclusion, the results of this analysis support the decision to perform either ORIF or primary THA in patients between the ages of 40 and 65 years who have a displaced femoral neck fracture, with the age at which to transition to primary THA found to be between 44 and 54 years old depending on medical comorbidities and the risk of fixation failure. The results of this study can be used to provide quantitative support for the shared decision-making that should occur between the patient and physician.
Tables showing the quality of the studies included in the analysis, THA implant survival rates, annual all-cause mortality rates by age, perioperative mortality rates during revision THA by age, utility ratios and failure/revision rates of ORIF by age, and distribution of values used in the probabilistic sensitivity analysis, as well as figures showing acceptability curves at different ages and medical comorbidities derived from the probabilistic statistical analysis, are available with the online version of this article as a data supplement at jbjs.org.
Investigation performed at the Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, North Carolina
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