Primary total joint arthroplasty (TJA) of the hip and knee are common and effective procedures for improving pain and function in patients with arthritis. National registries estimate more than 1 million total knee arthroplasty (TKA) and total hip arthroplasty (THA) procedures are performed annually in the United States,1 and as the baby boomer population continues to age, the demand for TJA will continue to increase. By 2030, the annual number of THA and TKA procedures is expected to rise to 572,000 and 3.48 million, respectively, in the United States.2 More emphasis is being placed on decreasing costs during the postoperative course. More than one-third of payments made for TJA were postdischarge, and 70% of those payments were made to postacute care facilities.3 Similarly, some studies estimate that by discharging patients directly home, savings of $8759 to $29,118 per patient can be achieved, which has drawn attention to discharge disposition following TJA in recent years.4 Because TJA is typically elective, the orthopedic surgeon usually carries the responsibility of managing these costs, and with proper clinical pathways, these costs can be reduced significantly.5
In patients with arthritis involving more than 1 joint, it may be taken into consideration which joint should be replaced first to optimize recovery and potential costs. However, no studies have been conducted that objectively examine the question of whether TKA or THA should be performed first based on the potential for increased costs from length of stay (LOS) and discharge disposition. This study examined whether order of surgery (ie, TKA or THA first) affects LOS and discharge disposition in patients with coexisting knee and hip arthritis. The current authors hypothesized that performing a TKA first in the setting of coexisting hip arthritis would be associated with a higher incidence of discharge to a skilled nursing facility (SNF). Secondarily, LOS, demographic factors, and 90-day complication rates also were evaluated.
Materials and Methods
All data for this study were obtained using the Michigan Arthroplasty Registry Collaborative Quality Initiative (MARC-QI), a statewide registry of THA and TKA procedures. After receiving Institutional Review Board approval, a MARCQI database query was performed to collect all available data for arthroplasties performed at 2 campuses of a single institution between July 2013 and April 2017. Inclusion criteria were patients 18 years and older who underwent both a primary THA and TKA within 18 months. Patients were divided into 2 groups based on whether THA or TKA was performed first. For all patients, the following data were collected from the MARCQI query: age, body mass index (BMI), time between procedures, LOS, discharge disposition, and the number of 90-day adverse postoperative events. Adverse 90-day postoperative events included deep infection, fracture, hardware failure, urinary tract infection, other return to the operating room, emergency department visit, readmission, or death.
All statistical analyses were performed using SPSS version 22 software (IBM, Armonk, New York). First, the equal variance and normality assumptions of continuous data were assessed using Levene's test and the Shapiro–Wilk test, respectively. Student t tests and Mann–Whitney U tests were used to assess differences in normally distributed and non-normally distributed independent outcome variables, respectively. A chi-square test was used to compare categorical variables. P<.05 was considered significant. A power analysis was conducted, with alpha=0.05 and a power of 0.80 to determine magnitude of differences able to be detected for the sample size.
A total of 211 patients underwent both TKA and THA performed within 18 months. Of these, 124 patients underwent THA first and 87 underwent TKA first. In 89 cases (42.2%), the second procedure was on the ipsilateral side. There was no difference in age or BMI between the 2 groups or the number of cases performed on the ipsilateral side (Table 1). There was a significantly longer length of time between the first and second arthroplasty in patients who underwent TKA first by a mean of 2 months (P=.001).
There was no difference between groups in discharge disposition for the first case (P=.833) or second case (P=.395) (Table 2). For all cases, 97.3% of the patients discharged home after their first case also were discharged home after the second case, and the remaining 2.7% were discharged to an SNF. For patients discharged to an SNF after the first case, 72.7% were discharged to an SNF after the second case, and the remaining 27.3% were discharged home.
The LOS did not vary between groups for the first procedure (P=.695) or second procedure (P=.473) (Table 3). There also was no difference between groups in the incidence of 90-day events after the first procedure (P=.272) or after the second procedure (P=.169). Furthermore, there were no differences in 90-day events following hip procedures whether done first or second (P=.371), and no differences in 90-day events following knee procedures whether done first or second (P=.524).
Time to Discharge
There was no difference in discharge disposition for THA or TKA, whether performed as the first procedure or second procedure (P=.426 and P=.699, respectively). There also was no difference between LOS for THA or TKA, whether done first or second (P=.404 and P=.739, respectively). Furthermore, there was no difference between groups in the difference in LOS between the first and second procedure (P=.599). Whether the procedure was on the ipsilateral side also did not impact the discharge disposition (P=.582) or LOS (P=.275) after the second procedure.
Given the sample size, with alpha=0.05 and a power of 0.80, it would be possible to detect an 18% difference between groups in the number of patients discharged home after the second case vs to an SNF or inpatient rehabilitation. It also would be possible to detect a difference between groups in mean LOS after the second procedure of .59 days, and a 16% difference between groups in the incidence of a 90-day event after the second case.
With the increasing rates of already prevalent TJA surgeries, the decision of whether a THA or TKA should be done first in a patient with symptomatic coexisting hip and knee arthritis is becoming more relevant. No previous study has evaluated this question from a cost perspective standpoint. The current authors hypothesized that TKA performed prior to THA would be associated with higher rates of discharge to an SNF. However, there were no significant differences in discharge disposition to an SNF between the 2 groups. The rates of discharge to home, SNF, and inpatient rehabilitation following primary arthroplasty (73%, 24%, and 3%, respectively) were comparable with reported national averages (70%, 19%, and 11%, respectively).6
There was a high correlation in patients' disposition following their first and second procedure, with 90% being discharged to the same destination after both operations. Of 144 patients who had been successfully discharged home following their first procedure, only 4 (2%) were discharged to an SNF following the second procedure. However, in patients who underwent THA first, discharge to an SNF decreased from 27.4% to 19.4% after the first and second procedures, respectively. No difference in LOS was observed between the 2 groups, and there also was no difference in LOS between patients' first and second TJA procedure. Interestingly, patients who underwent TKA first had their second TJA 2 months later from their index surgery than patients in the THA first group.
Based on these findings, the current authors believe other patient factors are the main determinant of discharge disposition rather than the order of TJA operations. However, the reduction in discharge disposition to an SNF between the first and second surgeries in the THA group merits further evaluation. Several studies have reported higher rates of discharge to postacute care facilities in Black, Asian, and Medicare patients for both primary THA and TKA.7–9 Advanced age and low socioeconomic status also have been directly implicated.10,11 Another study reported patient expectations were the most important predictor of patient disposition following elective TJA, which would place more importance on preoperative counseling.12 Factors such as these are likely to be much more important in respect to postoperative costs and complications, and it is estimated that patients with significant comorbidities can double the cost of TJA.3 Several risk assessment calculators have been proposed to incorporate these factors, but at this time, the current authors do not believe the order in which lower extremity TJA procedures are performed should be part of this calculation.
This study had several limitations. The study was retrospective, with inherent limitations. Results were from 2 campuses of a single institution, with associated potential regional or institutional bias. In addition, the sample size was relatively small, and although differences in discharge disposition may not be statistically significant, these differences can be clinically significant from a cost perspective in a larger population analysis, potentially resulting in a type II error. This is the first study to evaluate the order of performing THA or TKA first in patients with coexisting hip and knee arthritis from a cost perspective. The results of this study do not support recommending one procedure over the other based on cost. Further large-scale, multi-institutional studies are needed.
- Maradit Kremers H, Larson DR, Crowson CS, et al. Prevalence of total hip and knee replacement in the United States. J Bone Joint Surg Am. 2015;97(17):1386–1397. doi:10.2106/JBJS.N.01141 [CrossRef]
- Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780–785.
- Bozic KJ, Ward L, Vail TP, Maze M. Bundled payments in total joint arthroplasty: targeting opportunities for quality improvement and cost reduction. Clin Orthop Relat Res. 2014;472(1):188–193. doi:10.1007/s11999-013-3034-3 [CrossRef]
- Gage B, Morley M, Spain P, Ingber M. Examining Post Acute Care Relationships in an Integrated Hospital System. Waltham, MA: RTI International; 2009.
- Tessier JE, Rupp G, Gera JT, DeHart ML, Kowalik TD, Duwelius PJ. Physicians with defined clear care pathways have better discharge disposition and lower cost. J Arthroplasty. 2016;31(9)(suppl):54–58. doi:10.1016/j.arth.2016.05.001 [CrossRef]
- Keswani A, Tasi MC, Fields A, Lovy AJ, Moucha CS, Bozic KJ. Discharge destination after total joint arthroplasty: an analysis of postdischarge outcomes, placement risk factors, and recent trends. J Arthroplasty. 2016;31(6):1155–1162. doi:10.1016/j.arth.2015.11.044 [CrossRef]
- Schwarzkopf R, Ho J, Quinn JR, Snir N, Mukamel D. Factors influencing discharge destination after total knee arthroplasty: a database analysis. Geriatr Orthop Surg Rehabil. 2016;7(2):95–99. doi:10.1177/2151458516645635 [CrossRef]
- Schwarzkopf R, Ho J, Snir N, Mukamel DD. Factors influencing discharge destination after total hip arthroplasty: a California state database analysis. Geriatr Orthop Surg Rehabil. 2015;6(3):215–219. doi:10.1177/2151458515593778 [CrossRef]
- London DA, Vilensky S, O'Rourke C, Schill M, Woicehovich L, Froimson MI. Discharge disposition after joint replacement and the potential for cost savings: effect of hospital policies and surgeons. J Arthroplasty. 2017;31(4):743–748. doi:10.1016/j.arth.2015.10.014 [CrossRef]
- Inneh IA, Clair AJ, Slover JD, Iorio R. Disparities in discharge destination after lower extremity joint arthroplasty: analysis of 7924 patients in an urban setting. J Arthroplasty. 2017;31(12):2700–2704. doi:10.1016/j.arth.2016.05.027 [CrossRef]
- Gholson JJ, Pugely AJ, Bedard NA, Duchman KR, Anthony CA, Callaghan JJ. Can we predict discharge status after total joint arthroplasty? A calculator to predict home discharge. J Arthroplasty. 2017;31(12):2705–2709. doi:10.1016/j.arth.2016.08.010 [CrossRef]
- Halawi MJ, Vovos TJ, Green CL, Wellman SS, Attarian DE, Bolognesi MP. Patient expectation is the most important predictor of discharge destination after primary total joint arthroplasty. J Arthroplasty. 2015;30(4):539–542. doi:10.1016/j.arth.2014.10.031 [CrossRef]
|Characteristic||THA First (N=124)||TKA First (N=87)||P|
|Age, mean±SD, y||67±10||69±8||.067|
|BMI, mean±SD, kg/m2||31.6±6.8||31.7±6.7||.922|
|Ipsilateral second case||45.2%||37.9%||.295|
|Time between cases, mean±SD, mo||7.3±4.5||9.3±4.4||.001|
|Discharge Disposition and Procedure||No. of Patients|
|THA First (N=124)||TKA First (N=87)|
| First procedure||85 (68.5%)||63 (72.4%)|
| Second procedure||96 (77.4%)||64 (73.6%)|
| First procedure||34 (27.4%)||21 (24.1%)|
| Second procedure||24 (19.4%)||22 (25.3%)|
| First procedure||5 (4.0%)||3 (3.4%)|
| Second procedure||4 (3.2%)||1 (1.1%)|
Time to Discharge
|Day of Discharge and Procedure||No. of Patients|
|THA First (N=124)||TKA First (N=87)|
|Postoperative day 1|
| First procedure||15 (12.1%)||8 (9.2%)|
| Second procedure||14 (11.3%)||20 (23.0%)|
|Postoperative day 2|
| First procedure||50 (40.3%)||37 (42.5%)|
| Second procedure||54 (43.5%)||27 (31.0%)|
|Postoperative day 3|
| First procedure||47 (37.9%)||32 (36.8%)|
| Second procedure||42 (33.9%)||30 (34.5%)|
|Postoperative day 4+|
| First procedure||12 (9.7%)||10 (11.5%)|
| Second procedure||14 (11.3%)||10 (11.5%)|