More patients were seen in both TKA and THA groups with higher comorbidity burden as represented by a higher Deyo comorbidity index (Figure 1). TSA patients did not present an apparent pattern of changes in respect to the Deyo index. The LOS continuously decreased within each procedure category, with TKA at 4.04 ± 2.36 days in 2007 to 3.47 ± 1.93 days in 2013, THA at 4.26 ± 3.25 days in 2007 to 3.49 ± 2.69 days in 2013, and TSA at 2.65 ± 2.41 days in 2007 to 1.99 ± 1.78 days in 2013. Conversely, total hospital charges increased across all procedure types after adjusting for inflation based on 2007 dollar, with average charges for TKA at $35,721 in 2007 to $41,980 in 2013, THA at $39,575 in 2007 to $46,590 in 2013, and TSA at $31,551 in 2007 to $40,015 in 2013 (Figure 1).
We next analyzed the incidence of complications over time (Figure 2 and Table 1). All complications were adjusted for LOS and reported as complications per in-hospital day. The incidences of two complications continuously decreased for all procedure categories, such as wound infection (from 0.08% per hospital day in 2007 to 0.03% per hospital day in 2013 among TKA patients) and transfusion (from 7.54% per hospital day in 2007 to 4.04% per hospital day in 2013 in TKA) (Table 1). Other complications, including MI, and pneumonia remained largely unchanged from 2007 to 2013. The incidence of cardiac event excluding MI and ARF increased over time. ARF among TKA patients increased from 0.21% per hospital day in 2007 to 0.40% per hospital day in 2013.
The utilization of PT during the hospitalization remained consistently high, higher than 98% in TKA and THA patients and 63.7% to 73.1% among TSA patients (Figure 3). The utilization of occupation therapy increased, especially among THA and TSA patients, from 44.7% in 2007 to 59.7% in 2013 among THA patients (Figure 3 and Table 1). More utilization of echocardiography service was seen over time (Figure 3, from 0.92% to 1.29% in TKA, 1.20% to 1.69% in THA, and 0.10% to 1.02% in TSA). The utilizations of many other resources decreased, including for stress tests, chest radiographs, and CCU care among selective arthroplasty procedures (Figure 3).
Our analysis of all primary TKA, THA, and TSA cases collected from 2007 to 2013 in the HCUP/SID-NY database identified notable trends in patients undergoing these procedures. We determined a modest trend toward younger patients in TKA and THA and more prominent trend among patients undergoing TSA. Furthermore, we found an increased average comorbidity burden over time, as reflected by higher Deyo index scores. Complication rates remained relatively stable or decreased. Utilization of resources and tests was bidirectional with CT, chest radiograph, stress test, and CCU use decreasing and that of echocardiography and OT services increasing. No change in PT utilization was found.
Indications for TJA have expanded to include younger, more active patients,19 - 23 and our finding of a trend toward younger patients in primary TKA, THA, and TSA cases is consistent with trends in other patient databases over similar periods.24 , 25 The increasing proportion of younger patients seen here has potential implications for healthcare resource utilization because joint bearings intended for younger, more active patients tend to be costlier.24 Most patients for each of the three procedures were women; an analogous finding in the Veteran population has been attributed to a higher incidence of osteoarthritis in women.22 We observed a trend toward an increasing percentage of male patients for each of the three procedures, a finding that to our knowledge has not previously been reported. We observed no clear trend in the racial makeup of patients undergoing each of the three procedures.
Our finding of an increased average comorbidity burden in this patient group, as reflected by higher Deyo index scores, for TKA and THA, is consistent with national trends.2 , 26 Interestingly, as has been found on a national level for THA,2 comorbidity burden increased for TKA and THA while simultaneously age decreased. A higher comorbidity burden has been associated with higher costs in THA.27 Of note, we did observe an increase in inflation-adjusted total hospital submitted charges for each of the three procedures studied. However, we could not identify causes of this increase with the available information in the HCUP database studied (Figure 3). It is likely other factors beyond the scope of our study might be contributing to the increase of such submitted charges. For example, surgeons and hospitals are incentivized to discharge patients earlier and to screen patients to prevent the 30-day readmissions since the Affordable Care Act became effective. Over the past 10 years, more practices have implemented programs that include multimodal analgesia with peripheral nerve blocks, aggressive PT with multiple sessions (two to three times daily), and blood salvage therapy. All these potentially could increase the hospital cost with the aim of facilitating discharge readiness earlier. Because we also identified a downtrending pattern of complications over the years studied, the increase in initial hospital spending could potentially be cost-effective by decreasing high-cost complications. Future research is indicated to better understand what is driving the increase of hospital charges.
We identified stable or reduced rates of complications over the span of our study period. To account for changes in decreasing LOS, we adjusted rates to events per each in-hospital day.25 , 28 The incidence of postoperative complications remained overall stable or decreased, with the exception of ARF. Improved perioperative care is likely contributing to these, such as better wound closure techniques, improved wound dressing, the utilization of tranexamic acid, and other blood preservation techniques.29 - 31 As the LOS for all procedures also decreased, this raises the question whether the complication burden, particularly for those complications that present several days after joint arthroplasty, was merely shifted to intermediate care facilities such as skilled nursing facilities or acute rehab facilities to which joint arthroplasty patients were discharged.20 , 25 , 28 In an era of intensified focus to shift joint arthroplasty to an outpatient setting, this issue deserves further study because it potentially represents an important patient safety issue.
The reason for an increase in the diagnosis of ARF remains speculative. Since the publication of the RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria for acute kidney injury in 2004,24 , 32 and the AKIN (Acute Kidney Injury Network) modification in 2007,32 adoption of these definitions of AKI (acute kidney injury) has been inconsistent across medical societies and, presumably, in clinical care. It is possible that the promulgation of the RIFLE and AKIN criteria during our study period complicated the picture, leading to higher documentation rates. As an essential component of multimodal analgesia, NSAID has been administered more frequently in recent years. Such practice could also lead to an increase in creatinine levels meeting the diagnostic criteria for ARF, although with debatable clinical implications. It is also known that patients with increased comorbid burden are at greater risk of perioperative AKI,22 and patients in our study period did indeed trend toward a higher Deyo index. However, this does not explain why the incidence of other complications decreased or remained stable during the period.
Despite the suggestion that a higher comorbidity burden may be associated with increased resource utilization,27 we found a decrease in several metrics (ie, chest radiograph, stress test, and CCU) and stable utilization of PT. We observed an increase in the utilization of echocardiography and OT. We were not able to determine the timing of the utilization of these tests and services during hospitalization. Thus, it remains unclear, for example, whether echocardiography was being performed as part of preoperative testing and then billed as part of the hospitalization. The decrease in the utilization of stress tests and the increase in the use of echocardiography suggest further study into how evolving risk stratification practices for cardiac patients undergoing noncardiac surgery, or general trends in the utilization of echocardiography,33 might be affecting resource utilization in joint arthroplasty. One possibility is that the recent promulgation of strict criteria for the appropriate use of cardiac stress testing and the changes in reimbursement policy for cardiac stress tests34 could have theoretically placed economic pressure on cardiologists to opt for the less restrictive and less expensive tests such as the echocardiogram.
It has been suggested that the use of regional anesthesia in TSA, THA, and TKA is associated with decreased perioperative complications and resource utilization.12 , 35 In our analysis, we observed an overall decrease in complications and resource utilization in TSA even without a clear decrease in the use of general anesthesia alone as the anesthetic method, suggesting additional drivers at work other than type of anesthesia.
Interestingly, despite a shorter average LOS across the three procedures studied here, as well as a decrease in the utilization of several common resources as described earlier, total inflation-adjusted hospital submitted charges increased across all three procedures. This trend may just mirror the general trend in increasing healthcare costs brought on by factors such as increased administrative expenditures. Specifically related to orthopaedic surgery, it has been suggested that joint arthroplasty in younger patients is costlier because of the requirement for more “premium” implants that will withstand greater physical activity and have more longevity.24 In addition it is possible that more resources need to be spent on a given day to facilitate expediting earlier discharge, such as multiple costly PT sessions. However, submitted hospital charges should be seen as an imperfect proxy for actual costs and resource utilization, largely because charges vary from one hospital to another.25 , 27 The increase in hospital charges we observed here deserves further elucidation.
Our study is limited by its nature of using secondary data. Administrative codes should not be expected to perfectly capture clinical reality. However, any coding bias is unlikely to markedly change across institutions over the period studied, thus having only a modest effect on our trend analysis. Second, our study focused only on the same hospitalization. Readmissions and postdischarge events were not counted in our study.
We identified several interesting patterns of change over the period studied: a trend toward younger patients with more comorbidities, stable or decreasing incidence of most postoperative complications, shorter LOS, less resource utilization for many processes except echocardiography and OT, and increased inflation-adjusted total hospital submitted charges. Additional studies are indicated to elucidate potential causative factors for these trends. Nonetheless, our study provides vital information for healthcare providers and healthcare policy makers in designing clinical practices, reimbursement policies, and cost-effective healthcare initiatives.
The authors thank Lauren Wilson for her statistical support with the data analysis.
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons
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