RAPT and AM-PAC “6-Clicks”: Do They Correlate on Predicting Discharge Destination After Total Joint Arthroplasty?

Abstract

Background: The Risk Assessment and Prediction Tool (RAPT) and the Activity Measure for Post-Acute Care “6-Clicks” Mobility Score (AM-PAC) are validated discharge planning tools for patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA). Planning for discharge with these tools considers very different factors and it is important to determine if they relate. Purpose: We sought to determine whether the preoperative RAPT score would correlate with postoperative AM-PAC score for predicting discharge destination for THA and TKA populations. Secondarily, we sought to examine whether the AM-PAC and RAPT scores would remain statistically significant predictors of discharge destination despite covariates. Methods: A retrospective cohort study was performed for patients who underwent THA or TKA from January 2020 to December 2022 at a specialty orthopedic hospital. Primary variables included the RAPT score, the AM-PAC score, and discharge disposition. Correlation between AM-PAC and RAPT scores was tested using Pearson’s correlation coefficient, and association between both scores and discharge destination was tested using chi-square tests and multivariable logistic regression. Results: Our comparison of AM-PAC scores and RAPT scores found a statistically significant, positive correlation in both THA and TKA patients. Regression analysis found that increased RAPT and AM-PAC scores resulted in higher odds of being discharged home for both populations, after adjusting for all other variables. In both cohorts, patients discharged to a facility were more likely to be female, be over the age of 70 years, have Medicare/Medicaid insurance, and have a higher number of preoperative social work visits or any incidence of an intraoperative or hospital complication. Conclusions: This retrospective study found that RAPT score correlated with AM-PAC score for predicting discharge destination for elective THA and TKA populations, suggesting that these scores may be predictors of home discharge destination even when accounting for covariates. Further study is recommended.

Introduction

Identifying an appropriate discharge destination plays a significant role in cost containment in the post-acute phase of total joint arthroplasty (TJA) [16,25]. Research attributes approximately one-third of bundled payments to post-acute inpatient care [9,12,17,22]. In the United States, projected rates of primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) are expected to rise through 2040 by 248% and 401%, respectively [21]. Advancements in intraoperative and postoperative care have contributed to a decreased length of stay (LOS) for TJA surgeries, shifting many to an ambulatory surgery status [9,12,19,23]. The evolving reimbursement models of bundled care have also driven providers to shorten LOS for TJA [21]. Studies have illustrated that home discharge for patients after elective TJA is a safe, preferred, and cost-saving option [9,14,21,25].

Through patient education, shared decision-making, and managing patient expectations, care teams can identify safe and appropriate discharge destinations [6]. Many aspects of care require presurgical planning. At our institution, physical therapists play a critical role in discharge planning; patients undergoing TJA attend preoperative physical therapy (PT) sessions. Based on a patient’s preoperative clinical intake forms, discharge planning will be completed either by a physical therapist for straightforward discharge planning or a member of the case management team for more complex cases. The Patient Health Questionnaire-2 (PHQ-2) score of 3 or higher indicates a patient requires a social worker to complete discharge planning [13]. Physical therapists and case managers participate in discharge planning preoperatively, aiming to project actual discharge needs by garnering pertinent information preoperatively, upon hospital admission, and during the first visit with a patient. As movement analysis experts, physical therapists synthesize subjective and objective clinical information on a patient’s functional status and inform discharge recommendations shared with the patient and interdisciplinary team. Another important predictor of discharge destination to consider is patient expectations [7]. Incorporating the patient into decision-making on discharge destination before admission results shortens LOS and increases the number of home discharges [1,4,6,9].

Selecting patients’ discharge disposition can be simplified with objective measures available to assist discharge planners in identifying which patients are appropriate to be discharged home versus to an inpatient rehabilitation facility (IRF) or to subacute rehabilitation (SAR) [9]. The RAPT and the Activity Measure for Post-Acute Care “6-Clicks” Mobility Score (AM-PAC) are validated tools for predicting discharge destination in patients undergoing THA or TKA [8,19,24]. The RAPT is a 6-item preoperative survey that scores age, sex, preoperative walking distance, use of gait aid, community supports, and presence of a caregiver at home, with patients classified as low, intermediate, or high risk based on a 12-point scale [2,3,14,19]. A lower score indicates a patient may require an IRF/SAR while a higher score indicates a home discharge. Patients at our institution undergoing elective THA or TKA complete the RAPT during preoperative clinical intake. The AM-PAC is a functional measurement tool that evaluates 6 basic inpatient mobility tasks on a 4-point scale [10,11,15,24]. Each item is scored from 1 to 4 based on the amount of difficulty a patient has or how much help is needed from another person in completing the specific task. Lower scores equate to lower levels of function [10,11]. The AM-PAC is collected postoperatively by a physical therapist at the initial encounter, either on the day of surgery or the following morning, and is based on the patient’s performance during initial assessment.

As LOS decreases, clinicians benefit from more efficient workflows and access to predictive tools earlier in the process, which is why the RAPT is highly valuable. The AM-PAC measure allows for continued objective assessment of discharge destination postoperatively. The previously validated RAPT and AM-PAC tools are promising to help guide rehabilitation professionals in determining discharge recommendations. However, little has been published on whether these validated tools correlate on predictive discharge properties [14].

This retrospective review aimed to determine whether the preoperative RAPT score correlates with the postoperative AM-PAC score in predicting discharge destination for elective THA and TKA populations. Our secondary aim was to evaluate whether the RAPT and AM-PAC would remain statistically significant predictors of discharge destination while accounting for other covariates. We hypothesized that the RAPT and AM-PAC scores would predict the same discharge destination for THA and TKA patients, with and without accounting for covariates know to be related to discharge destination.

Methods

An Institutional Review Board–approved retrospective cohort study was conducted with information obtained from our institution’s electronic medical record (EMR). This study consisted of patients who underwent primary, unilateral THA or TKA from a single, orthopedic institution from January 2020 to December 2022. Demographic data including sex, body mass index (BMI), and age were collected at baseline.

Exclusion criteria included patients admitted for more than 7 days, revision surgeries, simultaneous bilateral procedures, and patients for whom the medical record did not specify discharge destination (Supplemental Fig. 1). After the exclusion criteria were applied, a total of 20,822 patients were included in the analysis, including 11,206 patients who underwent THA and 9616 patients who underwent TKA, an overwhelming majority of whom were discharged home. Of the THA patients, 228 patients (2.03%) were discharged to an IRF or SAR while 10,978 (97.97%) patients were discharged home. Of the TKA patients, 340 (3.53%) were discharged to an IRF or SAR while 9276 (96.46%) patients were discharged home (Supplemental Table 1).

Also collected were primary variables of interest, the preoperative RAPT score, the postoperative AM-PAC score collected by the PT, and discharge disposition, as well as covariates of interest: preoperative PT and social work visits, number of inpatient PT visits, payor information, hospital complications (defined by a diagnosis present on billing that was not present on admission), and intraoperative complications (defined by documentation in the operative note).

Statistical Analysis

Descriptive statistics of the study population were performed and summarized using means and standard deviations for continuous variables and frequencies and percentages for discrete variables. Discharge destination was dichotomized to a binary variable of home versus facility setting (IRF/SAR). Independent samples t tests were performed to compare the means of continuous data, while chi-square tests were performed to analyze percentage differences of categorical variables. Simple linear regression was used to assess the correlation between continuous variables, with Pearson correlation coefficients used to operationalize the magnitude of the correlation. Multivariable logistic regression was performed to assess independent associations between preoperative (ie, RAPT score) and immediate postoperative (ie, AM-PAC score) patient factors and discharge disposition. Statistical significance was defined as P values of .05 or lower. All analyses were performed using SPSS version 23.0 (IBM Corporation).

Results

For THA and TKA patients, 98.0% and 96.5% of patients were discharged home, respectively. The THA patients discharged home were younger on average than those discharged to an IRF/SAR (64.0 vs 75.3 years, P < .001); 75% of patients discharged to an IRF/SAR were female compared with 57% of patients discharged to home (P < .001). Private or commercial insurance was significantly higher in patients who were discharged to home (57%) compared with patients who were discharged to an IRF/SAR (14%; P < .001). For TKA patients, similar patterns of patient characteristics were seen in patients discharged to a home setting. Patients discharged to home were younger compared with patients not discharged to home (66.7 vs 74.6 years, P < .001) and had a lower percentage of female patients (60.0% vs 81.0%, P < .001). Patients with commercial insurance were also discharged to home at a higher percentage (50%) compared with patients discharged to an IRF/SAR (13%; P < .001).

RAPT scores were significantly higher (representing lower risk) for patients discharged home compared with patients discharged to a facility in both THA and TKA patients (THA: 9.6 ± 1.9 vs 5.8 ± 2.6; TKA: 9.6 ± 1.8 vs 6.2 ± 2.2, P < .001 for both procedures). Similar to RAPT scores, patients who were discharged to home had higher (representing higher functional ability) mean AM-PAC scores compared with patients not discharged to home in both THA and TKA cohorts. In THA, mean AM-PAC score was 23.7 ± 1.2 in patients discharged to home versus 16.9 ± 2.5 in patients discharged to an IRF/SAR (P < .001). In TKA patients, of patients discharged to home, the average score was 23.7 ± 1.2 compared with 17.3 ± 2.2 among patients discharged to an IRF/SAR (P < .001). Simple Pearson’s correlation test to evaluate postoperative AM-PAC scores from preoperative RAPT scores found a statistically significant, positive correlation in both THA (ρ: 0.235, P < .001) and TKA (ρ: 0.280, P < .001) patients (Supplemental Fig. 2).

Multivariable binary logistic regression models evaluated the outcome of home discharge for both THA and TKA cohorts (Table 1), while accounting for covariates. All variables from the univariate analysis were considered eligible covariates in the models. Race and ethnicity were dichotomized into a binary response of White versus non-White and Hispanic versus non-Hispanic, respectively (Table 1). Results from the regression analysis found that increased RAPT and AM-PAC scores resulted in higher odds of being discharged to home for both THA and TKA patients, after adjusting for all other variables in the model. In THA patients, a 1-point increase in RAPT score was associated with an adjusted odds of discharge home of 1.49 (95% confidence interval (CI): 1.31–1.70), while 1-point increase in AM-PAC score had an adjusted odds of discharge home of 2.94 (95% CI: 2.54–3.42). For TKA patients, similar effects of RAPT and AM-PAC scores were found, with increased scores associated with higher adjusted odds of discharge home (RAPT adjusted odds ratio [aOR]: 1.70, 95% CI: 1.50–1.93; AM-PAC aOR: 2.96, 95% CI: 2.61–3.36).

Table 1.

Multivariable logistic regression on discharge destination.

Factor (covariate)	Units or category	aOR	95% CI for aOR		P
			Lower	Upper
Total hip arthroplasty
RAPT score	N/A	1.49	1.31	1.70	.000
AM-PAC score	N/A	2.94	2.54	3.42	.000
Sex	ref = male	0.91	0.51	1.63	.756
Age	Years	0.98	0.95	1.02	.272
BMI	kg/cm2	0.99	0.95	1.03	.472
Race	ref = White	0.95	0.45	2.02	.902
Ethnicity	ref = Non-Hispanic	1.30	0.42	4.01	.645
Payor group	ref = Commercial	0.77	0.37	1.59	.484
Surgery year 2021	ref = 2020	0.43	0.21	0.91	.026
Surgery year 2022	ref = 2020	0.33	0.16	0.68	.003
Pre-op PT	Yes/No	2.16	1.13	4.14	.020
Pre-op social work visits	# of visits	0.42	0.33	0.55	.000
Inpatient PT visits	# of visits	1.10	1.01	1.20	.027
Any complications	Yes/No	0.51	0.30	0.87	.014
Total knee arthroplasty
RAPT score	N/A	1.70	1.50	1.93	.000
AM-PAC score	N/A	2.96	2.61	3.36	.000
Sex	ref = male	0.92	0.54	1.57	.766
Age	Years	0.98	0.94	1.01	.198
BMI	kg/cm2	1.00	0.96	1.03	.879
Race	ref = White	0.75	0.43	1.30	.302
Ethnicity	ref = Non-Hispanic	1.85	0.68	5.09	.231
Payor group	ref = Commercial	0.74	0.38	1.43	.370
Surgery year 2021	ref = 2020	1.12	0.64	1.97	.685
Surgery year 2022	ref = 2020	0.79	0.45	1.38	.407
Pre-op PT	Yes/No	1.49	0.86	2.58	.151
Pre-op social work visits	# of visits	0.57	0.45	0.73	.000
Inpatient PT visits	# of visits	1.10	1.01	1.19	.024
Any complications	Yes/No	0.54	0.34	0.86	.009

AM-PAC Activity Measure for Post-Acute Care, aOR adjusted odds ratio, BMI body mass index, CI confidence interval, PT physical therapy, RAPT Risk Assessment and Prediction Tool.

Multiple covariates were also found to be significant predictors of discharge home in our multivariable regression models. In THA patients, a preoperative PT visit doubled the adjusted odds of a home discharge (aOR: 2.16, 95% CI: 1.13–4.14). An increased number of inpatient PT visits was also associated with a home discharge (aOR: 1.10, 95% CI: 1.01–1.20). Conversely, a higher number of preoperative social work visits and any incidence of an intraoperative or hospital complication were associated with a decreased odds of home discharge. The years of 2021 and 2022 also saw a decreased likelihood of home discharge compared with the initial study year of 2020. For TKA patients, other than RAPT and AM-PAC scores, only the increased number of inpatient PT visits was associated with an increased odds of home discharge (aOR: 1.10, 95% CI: 1.01–1.19). An increased count of preoperative social work visits and complications were associated with a decreased odds of home discharge.

Discussion

As demand for TJA procedure rises and LOS decreases, efficient planning is essential to patient satisfaction, timely discharge, and cost containment. Reductions in LOS are facilitated by postsurgical pathways consisting of a multidisciplinary perioperative approach [6,12] and by determining a patient’s appropriate discharge location as early as possible [20]. Objective measures such as the RAPT and AM-PAC scores can help guide the discharge planning process [14,19,24,26]. However, few studies examine the correlation of preoperative RAPT scores with postoperative AM-PAC scores [14]. Our retrospective study of 20,822 THA and TKA patients at a specialty orthopedic hospital found that both the preoperative RAPT score and the postoperative AM-PAC score were strong predictors of discharge destination, with and without accounting for known covariates, and were significantly correlated with each other.

RAPT and AM-PAC scores collected for both THA and TKA cohorts were much higher in patients discharged home than in patients discharged to an IRF/SNF. Our finding that both the RAPT and AM-PAC remained significant predictors of discharge disposition while accounting for known demographics such as age, sex, and insurance payor, within a large TJA population, strengthens the evidence on the construct validity of both objective measures. Patients discharged to an IRF/SAR, regardless of procedure type, were more likely to be female, over the age of 70 years, and have Medicare/Medicaid insurance while admitted, which parallels previous research [16,18].

This study is limited by the fact that a much larger percentage of our sample was discharged home than to an IRF/SNF, skewing the inferences we can make from statistical comparison of the 2 cohorts. In addition, patients who were more likely to be discharged home were mainly White and non-Hispanic, which is supported by a recent publication whose authors could not comment on why this was the case, writing that “Health disparities are inherently complex and likely due to a multitude of societal and systemic factors, making it difficult to identify a root cause” [23]. In addition, COVID-19 likely produced a historical bias on the discharge destination of all patients in the years 2020 and 2021, when patients were encouraged to return home postoperatively due to concerns surrounding the virus [5]. This study is also from a single orthopedic institution in the Northeastern United States with patients receiving either THA or TKA surgery; thus, results may not apply to patients receiving other orthopedic procedures or at facilities of varying size and specialty.

We examined additional covariates including preoperative PT or social work visits, increased number of inpatient PT visits, and intraoperative and hospital complications. In the THA cohort, patients attending a preoperative PT visit were twice as likely to be discharged home, suggesting that preoperative PT may be a crucial factor in discharge planning. If patients who had preoperative PT received education well in advance on postoperative expectations, proper home environment set-up, required durable medical equipment, and applicable precautions, they were less likely to be discharged to an IRF/SAR. Receiving an increased number of inpatient PT visits was found to be a statistically significant predictor of a home discharge, regardless of procedure type. Additional PT visits may result in a longer LOS, but their benefit in helping patients achieve functional goals may lead to a safe home discharge. In both cohorts, a higher number of preoperative social work visits and any incidence of an intraoperative or hospital complication were a significant factor in predicting discharge to IRF/SNF. These findings suggest that clinicians should consider these covariates, in addition to the RAPT and AM-PAC, when predicting discharge destinations.

Further research should examine whether a postoperative AM-PAC score adds useful data following uncomplicated THA or TKA when the RAPT has been completed. This review points to interesting findings regarding the impact of modifiable and non-modifiable factors on patient discharge destinations. The AM-PAC questions strictly assess the patient’s functional abilities postoperatively, while the RAPT factors in age and gender and social variables such as reliance on community support.

In conclusion, the findings of this retrospective review suggest that preoperatively collected RAPT scores correlate with postoperatively collected AM-PAC measures for predicting discharge destination in elective THA and TKA patients. Higher scores on both measures increased the likelihood of a home discharge. Individually, both tools are strong predictors of discharge destination and remain strong predictors even when accounting for covariates known to impact discharge destination. These findings underscore the value of objective measures to predict discharge destination early in the perioperative process. Future studies should evaluate patients in rural areas, patients from more diverse backgrounds, and the value of physical therapists as discharge planners.