Dear Editors,
With great interest we read the recent article by Inacio et al.
1
comparing performance of three comorbidity measures to predict 90-day and 1-year mortality after total hip and knee arthroplasty in a cohort of elderly patients. They showed that the Elixhauser and Charlson comorbidity scores had similar performance for postoperative mortality prediction, but performed better than the RxRisk-V comorbidity score. Furthermore, a combined model with comorbidities identified by three comorbidity scores was the best postoperative mortality prediction model. This study includes a large sample of patients and the authors have used the right statistical methods to compare the performance of different models for postoperative mortality prediction. In our view, however, there are several issues in this study that need to be clarified before adoption into routine practice.First, three comorbidity scores used in this study only include baseline characteristics of study patients, but not preoperative mobility ability and functional status of patients. Actually, mobility disability is common among patients undergoing total hip and knee arthroplasty. Such condition can not only impair patient survival, but also may adversely affect postoperative recovery and outcomes. The available evidence shows that mobility disability is a strong independent predictor of mortality after total hip and knee arthroplasty
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, 3
.Second, other than the preoperative comorbidities and illness severity, surgical burden and risk also are the important determinants for postoperative mortality. It has been shown that compared with the total knee replacement, the unicompartmental knee replacement significantly decreases 45-day mortality
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. As compared with other surgical approaches, posterior surgical approach is associated with decreased 90-day postoperative mortality after total hip replacement5
. Furthermore, the early postoperative mortality is significantly lower in the bilateral hip or knee arthroplasty than in the unilateral procedure. As the weighted mean volume of blood loss is more than 1000 ml, total hip and knee arthroplasty is one of leading indications for surgical transfusions, and intraoperative blood transfusion has been identified as an independent predictor for increased postoperative mortality- Hunt L.P.
- Ben-Shlomo Y.
- Clark E.M.
- Dieppe P.
- Judge A.
- MacGregor A.J.
- et al.
National Joint Registry for England, Wales and Northern Ireland
90-Day mortality after 409 096 total hip replacements for osteoarthritis, from the National Joint Registry for England and Wales: a retrospective analysis.
90-Day mortality after 409 096 total hip replacements for osteoarthritis, from the National Joint Registry for England and Wales: a retrospective analysis.
Lancet. 2013; 382: 1097-1104
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, 6
. In addition, perioperative hypotension is most prevalent during the intraoperative period and has been associated independently with short-term morbidity and mortality after noncardiac surgery. In fact, as comparison with the surgical risk stratification that only includes preoperative variables, the inclusion of intraoperative elements in the multivariable model can improve the performance to predict perioperative mortality and adverse cardiac events7
.Third, for noncardiac surgical patients, the preoperative comorbidities including cardiac, renal and pulmonary diseases, can be deteriorated by perioperative stress and complications, especially for elderly patients. Furthermore, new onset postoperative organ injury and dysfunction, such as myocardial or kidney injury, heart failure, arrhythmias, acute ischemic stroke, delirium and deep vein thrombosis, have been shown as independent predictors of increased mortality after noncardiac surgery. In available literature, the performance of preoperative comorbidity scores in predicting the postoperative mortality of patients has been questioned
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, 9
.Thus, we argue that alone use of preoperative comorbidity scores may not provide an exact prediction for postoperative mortality in the elderly patients undergoing total hip and knee arthroplasty. The best postoperative mortality prediction model should include the known preoperative, intraoperative and postoperative risk factors affecting postoperative mortality.
Authors' contributions
Fu-Shan Xue: This author had carefully read the manuscript of Inacio et al., analyzed their methods and data, suggested the comment points, and drafted this manuscript, and is the author responsible for this manuscript. Fu-Shan Xue had seen and approved the final manuscript.
Gui-Zhen Yang: This author had read the manuscript of Inacio et al., and helped to analyze their methods and data, and reviewed this manuscript. Gui-Zhen Yang had seen and approved the final manuscript.
Chao Sun: This author had read the manuscript of Inacio et al., and helped to analyze their methods and data, and revise the comment points. Chao Sun had seen and approved the final manuscript.
Conflict of interest
None declared.
Acknowledgement
None of the authors received financial support and had potential conflicts of interest for this work.
References
- Evaluation of three co-morbidity measures to predict mortality in patients undergoing total joint arthroplasty.Osteoarthritis Cartilage. 2016; 24: 1718-1726
- Predictors of mortality following primary hip and knee replacement in the aged. A single-center analysis of 1,998 primary hip and knee replacements for primary osteoarthritis.Acta Orthop. 2013; 84: 44-53
- All cause and disease specific mortality in patients with knee or hip osteoarthritis: population based cohort study.BMJ. 2011; 342: d1165
- 45-Day mortality after 467 779 knee replacements for osteoarthritis from the National Joint Registry for England and Wales: an observational study.Lancet. 2014; 384: 1429-1436
- 90-Day mortality after 409 096 total hip replacements for osteoarthritis, from the National Joint Registry for England and Wales: a retrospective analysis.Lancet. 2013; 382: 1097-1104
- Anemia and patient blood management in hip and knee surgery: a systematic review of the literature.Anesthesiology. 2010; 113: 482-495
- Intraoperative tachycardia and hypertension are independently associated with adverse outcome in noncardiac surgery of long duration.Anesth Analg. 2002; 95: 273-277
- Performance of posttransplant model for End-Stage Liver Disease (MELD) and delta-MELD scores on short-term outcome after living donor liver transplantation.Transplant Proc. 2009; 41: 3766-3768
- Established preoperative risk factors do not predict long-term survival in isolated coronary artery bypass grafting patients.Ann Thorac Surg. 2012; 93: 1943-1948
Article info
Publication history
Published online: September 08, 2016
Accepted:
July 25,
2016
Received:
July 21,
2016
Footnotes
☆Re: Inacio MC, et al. Evaluation of three co-morbidity measures to predict mortality in patients undergoing total joint arthroplasty. Osteoarthritis Cartilage. 2016;24(10):1718-26. http://dx.doi.org/10.1016/j.joca.2016.05.006.
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- Response to Letter to the Editor: ‘Use of preoperative comorbidity scores to predict mortality after total arthroplasty’Osteoarthritis and CartilageVol. 25Issue 1
- PreviewThank you for the opportunity to reply to Xue et al.'s letter regarding our recent manuscript. We appreciate Xue et al.'s interest in our study and agree that a series of pre, intra, and post-operative factors are associated with a higher risk of mortality after joint replacement surgery. We do not dispute the importance of these factors and their impact on death. Our study did not intend to identify factors associated with mortality after surgery but instead evaluated and compared the ability of three widely used co-morbidity measures' to predict mortality.
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