Joint Replacement Rehabilitation Outcomes on Discharge From Skilled Nursing Facilities and Inpatient Rehabilitation Facilities

Article Outline

• Abstract
• Methods
  • Overall Study Design
  • Study Facilities
  • Study Group
  • Measures and Instruments
    • Comprehensive Severity Index
    • FIM
    • Point-of-care documentation instruments
  • Data Collection and Reliability
    • Facility characteristics
    • FIM
    • Point-of-care documentation
    • Chart abstraction
  • Data Analysis
• Results
  • Study Facilities
  • Patient Characteristics
    • Demographic, medical, and functional profile
    • Payer mix
  • Process of Care
  • Outcomes
    • Functional status—descriptive analysis
    • Functional status—multivariate analysis
    • Discharge destination
• Discussion
  • Implications for Practice and Policy
  • Study Limitations and Generalizability of Study Findings
• Conclusions
• Acknowledgments
• References
• Copyright

Abstract 

DeJong G, Horn SD, Smout RJ, Tian W, Putman K, Gassaway J. Joint replacement rehabilitation outcomes on discharge from skilled nursing facilities and inpatient rehabilitation facilities.

Objective

To compare functional outcomes at discharge across postacute settings.

Design

Prospective observational cohort study.

Setting

Eleven inpatient rehabilitation facilities (IRFs), 8 freestanding skilled nursing facilities (SNFs), and 1 hospital-based SNF from across the United States.

Participants

Consecutively enrolled patients (N=2152): patients with knee replacement (n=1401) and patients with hip replacement (n=751).

Interventions

None; examination of existing practice patterns.

Main Outcome Measure

FIM discharge motor score.

Results

Freestanding SNF patients entered with higher motor FIM scores and left with higher scores than did IRF patients. IRF patients, however, achieved larger motor FIM gains and achieved them in a shorter time. In multivariate models controlling for patient differences and onset days, IRFs were associated with better discharge motor outcomes, but the overall setting effect was not large. The largest motor FIM differences were between medium-volume IRFs and low-volume freestanding SNFs: 4.6 motor FIM points for patients with knee replacement and 7.3 motor FIM points for patients with hip replacement. Other differences between settings were much smaller. Multivariate models explained between a third and a half of the variance in outcome.

Conclusions

As a group, IRFs had better motor FIM outcomes than did SNFs, but the size of the IRF advantage was not large. Other important facility and practice characteristics also were associated with discharge outcomes after joint replacement rehabilitation. Earlier and more intensive rehabilitation was associated with better outcomes. The volume of joint replacement patients seen by a facility also plays a part: medium-volume facilities among both SNFs and IRFs had better outcomes.

Key Words: Arthroplasty, replacement, hip, Arthroplasty, replacement, knee, Rehabilitation, Skilled nursing facilities

List of Abbreviations: BMI, body mass index, CMG, case-mix group, CMS, Centers for Medicare and Medicaid Services, CSI, Comprehensive Severity Index, IRF, inpatient rehabilitation facility, JOINTS I, Joint Replacement Outcomes in Inpatient Rehabilitation Facilities and Nursing Treatment Sites, JOINTS II, follow up study to Joint Replacement Outcomes in Inpatient Rehabilitation Facilities and Nursing Treatment Sites, LOS, length of stay, OLS, ordinary least squares, OT, occupational therapy, POC, point-of-care, PPS, prospective payment system, PT, physical therapy, SNF, skilled nursing facility

IN THE YEAR 2005, a total of 735,064 Americans obtained a total hip or total knee replacement. Of these, 562,300 (76.5%) received some type of postacute care. In fact, joint replacement is the most frequent condition leading to postacute admission in an SNF or an IRF.¹, ² These 2 rehabilitation settings are sometimes seen as potential substitutes for one another, with SNFs providing less intensive rehabilitation services over a longer LOS and IRFs providing more intensive services over a shorter LOS.³

Where patients with a hip or knee replacement should obtain their rehabilitation remains a vexing issue in American postacute care. Little is known about the relative outcomes of patients with joint replacement who go to SNFs or IRFs, in part because these 2 venues use different patient assessment tools to compare outcomes.⁴ The issue became more contentious after Medicare's 75% rule (now 60% rule) that significantly limited the types of patients with joint replacement who could be admitted to an IRF and still allow an IRF to qualify as an IRF for Medicare payment purposes.⁵, ⁶, ⁷ Implicit in the Medicare ruling was the assumption that patients with joint replacement could be served less expensively in SNFs and achieve roughly similar outcomes.

While the matter of SNF-level versus IRF-level rehabilitation care has been an enduring one in the United States, studies in other countries shed limited light on this choice mainly because many countries do not have a tradition of SNF-level care. Australian⁸ and Canadian⁹ studies in the 1990s compared follow-up outcomes at 12 and 8 months, respectively, among patients with joint replacement who received rehabilitation in a bed-service rehabilitation center and those who went home with or without rehabilitation. Both studies found no significant differences.

In the United States, most studies that have compared postacute outcomes across settings of care have focused on patients with stroke and hip fracture.¹⁰, ¹¹, ¹², ¹³, ¹⁴, ¹⁵, ¹⁶ These studies found that patients with stroke who went to IRFs fared better than those who went to SNFs, but found the results for patients with hip fracture mixed, with neither IRFs nor SNFs conferring a clear-cut advantage for patients with hip fracture.

Few studies have focused specifically on outcomes of patients with joint replacement across settings of care. In a 3-city study conducted in the mid-1990s, Kane et al¹³ examined follow-up outcomes of patients with hip replacement, but study limitations narrowed the inferences that could be made about home-level, SNF-level, and IRF-level care.

Buntin et al⁴ used Medicare claims data from January 2003 through June 2004 to examine outcomes of patients with joint replacement who went home (N=148,558), to IRFs (N=148,874), and to SNFs (N=127,719). They found that IRF patients were admitted with lower levels of function but were discharged at higher levels of function relative to SNF patients. Despite its large numbers, the Buntin⁴ study faced 2 major challenges. First, the study's claims data did not allow investigators to control for many of the patient covariates that might affect outcomes. Second, SNFs and IRFs used different patient assessment instruments that were administered at different points in time.

Using a matched-group design (87 IRF and 87 SNF patients) from 1 IRF and 5 SNFs in the same geographic area, Walsh and Herbold¹⁷ reported that IRF patients ambulated longer distances, were discharged home more frequently, were transferred to acute care less frequently, used less home care, and used a walker less frequently. Investigators matched patients on age, sex, type of surgery, and admission ambulation score on the FIM. (When replicating these 4 matching criteria using data from the study reported here, we found some important differences in admission FIM scores between IRF and SNF patients that may not have been addressed in the Walsh and Herbold study).

This article evaluates the outcomes at discharge associated with SNF-level and IRF-level care for patients who have a knee or hip replacement (exclusive of those with hip replacement after hip fracture). The article reports findings from the nationwide multicenter JOINTS I study conducted from 2005 to 2007. This study examined processes of care and discharge outcomes associated with joint replacement rehabilitation. An accompanying article, also based on JOINTS I, examines the types, duration, and intensity of therapy actually received in both SNFs and IRFs, while this article focuses on outcomes at discharge. A follow-up study, the JOINTS II study, examines patient outcomes at follow-up and evaluates use of rehabilitation and health care services in the first several months after discharge from an SNF or an IRF. We report the results of the JOINTS II study in 2 accompanying articles.¹⁸, ¹⁹

The central question addressed in this article is which setting of care produces better discharge outcomes for patients with joint replacement after adjusting for patient differences and select facility characteristics. Implicit here is the null hypothesis that there are no differences in outcomes related to setting of postacute care for joint replacement rehabilitation. This question was predicated on the assumption that SNFs and IRFs provide relatively homogeneous sets of services within their respective settings. This assumption, we learned, was not correct mainly because it did not take into account the significant practice differences within settings, particularly among SNFs, including the differences between freestanding and hospital-based SNFs.³ In this article, we describe how patient outcomes differ at discharge across 3 settings of care: freestanding SNFs, a hospital-based SNF, and IRFs.

Back to Article Outline

Methods 

Overall Study Design 

JOINTS I was a prospective observational cohort study. It did not entail a new intervention; instead, it observed the actual processes and practices of care and their associated outcomes. Patient differences were controlled through multivariate analyses that included a large array of patient characteristics, including the patient's level of medical acuity and functional status.

The study design and data collection protocols were approved by both a parent institutional review board and local review boards representing each of the participating facilities. All patients entered the study consecutively from February 2006 through February 2007. Because this was not an intervention study and involved no direct patient contact by study investigators, patient consent was not required, and thus no patient refusals had to be taken into account that might otherwise have altered the relative outcomes observed in the 3 settings of care.

One hallmark of the study was its clinical practice team comprised of local study site directors and front-line clinicians from both SNFs and IRFs who worked together to develop the study's data collection protocols and review study findings. Because SNFs and IRFs sometimes are viewed as competing service delivery systems with different advocacy interests, we created the clinical practice team as a vehicle both to improve study methods and to forge consensus and buy-in across participating facilities.

Study Facilities 

Several factors were considered when recruiting facilities for the study. Because the size, scope, and funding of the study did not allow for a national probability sample of facilities, our most important facility selection goal was to achieve geographic diversity. We sought to recruit at least 2 SNFs and 2 IRFs from each of the 4 major census regions. Moreover, we sought a mix of freestanding and acute hospital-based facilities, for-profit and nonprofit facilities, and facilities from both high and low managed-care markets.

Because of the extensive ramp-up activities associated with data collection design and training at each facility, we sought facilities that could bring 200 or more patients into the study and thus reduce facility transaction costs. We had to relax this threshold as recruitment continued among SNFs, which had much lower patient volumes than projected.

Facility participation was entirely voluntary. One participating SNF had significant data quality issues, and another SNF with a handful of patients was unable to compile its data in a timely manner. We excluded both facilities from the final study sample. As we report in DeJong et al,³ the study's sole hospital-based SNF had practice differences that were materially different from the study's freestanding SNFs. Thus, we present findings for 3 types of facilities: (1) 8 freestanding SNFs, (2) 1 hospital-based SNF, and (3) 11 IRFs. In our multivariate analyses, we considered the hospital-based SNF both as an independent setting and as 1 of several SNFs by combining it with the freestanding SNFs.

Study Group 

Patient selection criteria for this study were broad: (1) 21 years or older, (2) admitted after hip or knee replacement of any type (including bilateral replacements and revisions), (3) admitted from any source, and (4) did not have a hip fracture prior to hip replacement. We excluded patients with hip fracture for this analysis mainly because this subcohort presented a different demographic and treatment profile.

Measures and Instruments 

Three measures and instruments were used: (1) the CSI, which measures patient acuity at admission; (2) the FIM, which measures patient functional status at admission and discharge; and (3) the study's POC documentation system, which measures processes of care over the course of the patient's stay.

As the study's principal severity adjuster, the CSI provides a comprehensive, disease-specific measure of severity of illness and acuity. It considers over 2200 potential variables that include patient characteristics, medical history, physiologic parameters, laboratory findings, and a myriad of patient signs, symptoms, and physical findings. The CSI score combines a patient's physiologic, functional, and psychosocial complexity into a single overall score based on the extent and interaction of all the patient's various health conditions. CSI is a continuous score with no upper limit.²⁰, ²¹, ²², ²³, ²⁴, ²⁵

The FIM, along with CSI, served as an important risk adjuster at admission. FIM consists of 2 subscales: (1) a 13-item motor subscale and (2) a 5-item cognitive subscale.²⁶, ²⁷ Each item uses a 7-point scale. Motor FIM was the study's main outcome variable because it was the portion of FIM that was most aligned with the goals associated with joint replacement rehabilitation. The study used both motor FIM and cognitive FIM to characterize the patient at admission to rehabilitation. Cognitive FIM was not used as an outcome measure because patients with joint replacement rarely present serious cognitive limitations, and cognitive FIM demonstrated significant ceiling effects at discharge. In all instances, we used the unweighted motor and cognitive FIM scores because there is no known Rasch-adjusted FIM scoring system or weights for patients with joint replacement. Additional information about the study's use of FIM can be found in the accompanying article by DeJong et al.³

We also used FIM to categorize patients into 6 CMGs used by CMS for IRF payment purposes. We collapsed the 6 CMGs into 3 CMG groupings and labeled them as mild, moderate, or severe as outlined in table 3 of DeJong et al.³

An important feature of the JOINTS study was the collection of all processes of care in order to characterize similarities and differences of care rendered across all 3 settings and how these differences might be taken into account when evaluating outcomes. Because patient records across participating SNFs and IRFs provided an inadequate and nonuniform characterization of rehabilitation care a patient received, we created and tested, with the help of the study's clinical practice team, a standardized POC documentation instrument for each major rehabilitation discipline that could be used across all participating sites.

In this article, we use POC data derived only from physical and occupational therapy POC instruments because these 2 POC instruments were used consistently and uniformly. Moreover, in this article we address only the intensity of therapy as measured by the overall amount of therapy divided by the patient's LOS; we do not address the role of specific therapy activities in facilitating outcomes. Therapy intensity is a defining difference between SNFs and IRFs and thus also serves as a proxy for differences between SNFs and IRFs. We provide a more granular characterization of individual therapy activities across all 3 types of facilities in an accompanying article by DeJong.³

Data Collection and Reliability 

We obtained data on facility characteristics from 2 main sources. First was the provider of service files maintained and updated quarterly by CMS for each Medicare-certified provider. CMS creates the provider of service from the Online Survey and Certification Reporting System to which individual study facilities report key facility characteristics. Second was a 1-page facility characteristics questionnaire sent to each study facility site director to confirm and supplement data obtained from CMS provider of service files. From these 2 sources we obtained data on facility characteristics such as geographic location, profit status, bed size, annual patient volume, occupancy rates, physician and pharmacy services, payer mix, staffing ratios, and presence of beds dedicated to orthopedic or joint replacement rehabilitation patients.

The FIM was administered at admission and discharge in all 3 settings. Because SNFs do not use FIM routinely as do IRFs, it was essential to make sure that SNFs interpreted and administered the FIM in the same manner as IRFs. To ensure that all sites administered the FIM appropriately and consistently, we engaged IT HealthTrack, a FIM training and follow-up survey organization, to train clinical staff at each study site. SNF clinicians completed a 3-day training session, and all clinicians were required to score 100% on an examination that tested their knowledge of FIM and its uses. While we did not conduct formal reliability checks thereafter, we did evaluate FIM scoring to determine whether there were any anomalous FIM scores, at both the individual and facility level, relative to what else was known about individual patients—for example, age and admission CSI—to determine if corrective action was required.

Physical and occupational therapists collected POC therapy activity data in 5-minute increments either during the course of therapy or immediately at the conclusion of a therapy session. This documentation was included in the patient chart and was later abstracted during chart abstraction. Altogether, the study collected data on 61,146 PT and OT sessions.

Reliability of POC data was checked internally but not across settings. However, because therapists from all settings participated in POC development and definitions and they participated in therapy-specific conference calls throughout data collection to address questions across all sites, we expect that POC data are as reliable as other variables defined and obtained from existing medical charts.

Each study facility designated a chart abstractor who underwent a 3-day off-site training program using charts from the abstractor's own facility. An experienced chart abstractor worked with the facility-designated abstractor in reviewing sample charts until the 2 achieved 95% agreement on all data elements abstracted. Once abstracted, these data were reviewed, edited, and entered into the database by project staff. Reliability was checked periodically throughout data collection and at the end of data collection by randomly selecting charts from each site for reabstracting by project staff. Data abstractors continued to maintain 95% agreement on all data elements abstracted.

Through the chart abstraction process, we obtained data on patient characteristics, patient medical history, comorbidities, living situation, employment status, payers, use of durable medical equipment, use of orthotics and prosthetics, medications, and a variety of other variables related to patient status and outcome. Through chart abstraction we also obtained all the data needed to determine the patient's severity of illness and acuity as measured by CSI described above in Measures and Instruments.

Data Analysis 

We used both descriptive and multivariate analyses to examine facility and patient characteristics and how they relate to outcomes. We took into account important differences within as well as between facility types (freestanding SNF, hospital-based SNF, IRF). One of these differences was annual volume of patients with joint replacement; we subclassified study facilities further by annual volume of patients with joint replacement served—low, medium, high, and very high volume. To determine facility volumes, we chose calendar year 2006 as the reference year because it coincided with the study's data collection period (table 1). (A facility's joint replacement volume should not be confused with its bed size; a small facility, for example, may serve a very high volume of patients with joint replacement because it chooses to specialize in rehabilitation of patients who had a joint replacement.)

Table 1. Facility Volume—Annual Number of Patients With Joint Replacement^⁎

Source: JOINTS study.

Abbreviations: Fs-SNF, freestanding SNF; Hb-SNF, hospital-based SNF.

We used OLS regression in SAS statistical software^a to identify variables that were significantly associated with motor FIM outcomes at discharge. We checked for multicollinearity and considered possible interaction terms. We used a stepwise selection process that allowed variables to enter and leave the model and evaluated the relative strength of each variable by examining its F value. We chose the most parsimonious models by allowing only significant variables (P<.05) to remain in the model.

Separate OLS regression models were created for patients with knee replacement and patients with hip replacement with discharge motor FIM as the dependent variable. We considered 3 sets of independent variables: (1) patient characteristics (eg, age, sex, level of education, living status, revision [yes/no], bilateral replacement [yes/no], patient acuity as measured by CSI, motor and cognitive FIM scores on admission); (2) facility characteristics (eg, type and volume); and (3) 2 POC variables (eg, onset days or days from surgery to onset of rehabilitation, and intensity of OT and PT measured by total hours of OT and PT divided by LOS).

The 2 POC variables deserve greater elaboration. First, onset days may represent a practice difference between SNFs and IRFs or may be an independent predictor of outcomes and thus needs to be taken into account. Varying number of onset days may be a function of (1) discharge planning and referral practices in acute care, (2) health plan or fiscal intermediary decision-making, (3) efficiency of SNF or IRF admission processes, (4) availability of SNF and IRF beds in a given geographic area, or (5) medical complications that may have prolonged the patient's stay in acute care. Thus, we chose to consider onset days as an independent predictor without attributing its value to any one of these possible explanations. Onset days is part of the baggage that the patient brings to the rehabilitation process and thus could be considered a patient characteristic as well as a process variable.

Second, intensity of therapy is as much a facility characteristic as it is a POC variable mainly because SNFs and IRFs are defined in part by the intensity of care they provide—with SNFs offering a less intense level of therapy and IRFs offering a more intense level of therapy because of the 3-hour rule. In short, therapy intensity, though a continuous variable, also serves as a proxy for setting of care––SNF or IRF.

We report 3 sets of regression models for patients with knee and hip replacement. In model 1, we allowed only patient characteristics and setting to enter, not volume or intensity. In model 2, we also allowed facility characteristics such as intensity and volume to enter. In model 3, we omitted intensity because of its strong association with setting and instead allowed volume-facility combinations—for example, high-volume SNFs or medium-volume IRFs. In running our 3 regressions models, we considered models in which the hospital-based SNF was considered a distinct setting apart from freestanding SNFs and IRFs, another in which the hospital-based SNF was excluded altogether, and another in which the hospital-based SNF was combined with the freestanding SNFs, an all-SNF model.

We also conducted a logistic regression analysis to determine the robustness of our OLS regression findings. To do so, we redefined the patient's FIM gain as a dichotomous outcome variable: whether the patient achieved a FIM gain of 25 or more points (fiftieth percentile gain).

For multivariate analysis we did not consider postdischarge destination (eg, home, institutional setting) because there was very little variation in discharge outcomes except in a few instances as noted in table 4. Lack of variation was expected because a hip or knee replacement is most often an elective procedure, and patients expect to go back to their homes or the living environment from which they came.

Back to Article Outline

Results 

Study Facilities 

The final study sample included patients from 20 facilities—8 freestanding SNFs, 1 hospital-based SNF, and 11 IRFs. All 11 IRFs were freestanding (table 2). While the study sought a representative balance of freestanding facilities and hospital-based units among study SNFs and IRFs, the vast majority of study facilities were freestanding, in part because hospital-based units did not have the target volumes we sought. About one third of the freestanding SNFs and nearly three fourths of the IRFs were nonprofit facilities, as was the hospital-based SNF, although the hospital-based SNF was staffed by contract therapists from a for-profit company. Thus, the distinction between for-profit and nonprofit was not always a clear one. About one third of study facilities had a dedicated orthopedic or joint replacement rehabilitation unit with designated beds.

Table 2. JOINTS Study Facility Characteristics by Type of Facility Compared With All SNFs and IRFs Nationally

Facility Characteristics	JOINTS Study			National⁎
	Fs-SNF n=8	Hb-SNF n=1	IRF n=11	SNF n=15,027	IRF n=1219
Size (no. of beds), mean ± SD	180.3±111.5	50.0	99.1±45.1	107.3±64.9	31.5±28.1
Has dedicated orthopedic or joint replacement unit (%)	25.0	Yes	36.4	NA	NA
Nonprofit (%)	37.5	Yes	72.7	28.8	61.8
Freestanding (%)	100.0	No	81.1	92.0	17.9
Hospital-based unit (%)	0.0	Yes	18.9	8.0	82.1
2006 Occupancy rate (%), mean ± SD	90.4±11.1	85.0	90.0±16.8	NA	NA
No. of patients with joint replacement in 2006, mean ± SD	98.8±86.3	315.0	295.2±170.8	NA	163.4
24-Hour onsite physician coverage (%)	37.5	Yes	100.0	NA	100.0
Onsite pharmacist coverage (%)	0.0	Yes	100.0	NA	NA
Geographic region
Northeast	2	√	2	2722	215
Midwest	4	0	2	4813	334
South	1	0	4	5133	466
West	1	0	3	2349	202
Payer mix†
Non-HMO Medicare patients (%)	83.9	81.2	70.8	NA	63.4
HMO patients (%)	19.3	14.0	16.0	NA	NA

Source: JOINTS study facility questionnaire and Centers for Medicare and Medicaid Services provider of service file.

Abbreviations: Fs-SNF, freestanding SNF; Hb-SNF, hospital-based SNF; HMO, Health Maintenance Organization; NA, not applicable.

While study freestanding SNFs had many more beds than study IRFs on average (180.3 vs 99.1), study IRFs served an average of nearly 300 patients with joint replacement a year, while study freestanding SNFs served an average of about 100 patients a year. Study facilities fell neatly into 1 of 4 facility volume categories as outlined in table 1—low, medium, high, and very high volume. Cut points between these categories were clear and unambiguous.

Though nominally an SNF, the hospital-based SNF was a hospital-based facility that shared therapy staff with a sister IRF in the same hospital and had many features of an IRF such as an average LOS of 8.8 days, ready access to physician and pharmacy coverage, a volume of patients with joint replacement comparable to study IRFs, and similar levels of patient severity. It was similar to a freestanding SNF mainly in therapy intensity (1.8 therapy hours a day). In short, the hospital-based SNF was a hybrid of a freestanding SNF and an IRF (see fig 1 in DeJong et al³).

• 
  • View Large Image
  • Download to PowerPoint

• Fig 1. 

  Discharge motor FIM scores and 95% confidence intervals for patients with knee and hip replacement discharged from SNFs and IRFs, adjusted for patient differences. *Model 1b is the flip side of model 1a shown in table 6. Model 1b forces in the all-SNF variable and uses IRF as the reference group. Model 2 based on table 7 is not shown because it includes no setting effects (setting effect obscured by therapy intensity). Abbreviations: med., medium; vol., volume.

Patient Characteristics 

As outlined in table 3, the final study group consisted of 2152 patients, 65.1% of whom had a total knee replacement and the remaining 34.9% of whom had a total hip replacement. Some 62.4% of the entire study group came from IRFs, 25.2% from freestanding SNFs, and the remaining 12.4% from the study's hospital-based SNF.

Table 3. Numbers of Patients in JOINTS Study Group by Type of Replacement^⁎

Type of Joint Replacement	Fs-SNF		Hb-SNF		IRF		Total
	n	%	n	%	n	%	n	%
Kneereplacement	353	65.0	189	71.1	859	64.0	1401	65.1
Hipreplacement	190	35.0	77	28.9	484	36.0	751	34.9
Total	543	100.0	266	100.0	1343	100.0	2152	100.0
Kneereplacement
Unilateral	339	96.0	187	98.9	704	82.0	1230	87.8
Bilateral	14	4.0	2	1.1	155	18.0	171	12.2
Total	353	100.0	189	100.0	859	100.0	1401	100.0
Revision	19	5.4	9	4.8	52	6.1	80	5.7
Hipreplacement
Unilateral	189	99.5	77	100.0	467	96.5	733	97.6
Bilateral	1	0.5	0	0.0	17	3.5	18	2.4
Total	190	100.0	77	100.0	484	100.0	751	100.0
Revision	29	15.3	6	7.8	78	16.1	113	15.1

Source: JOINTS study.

Abbreviations: Fs-SNF, freestanding SNF; Hb-SNF, hospital-based SNF.

Freestanding SNFs and IRFs served similar percentages of patients with knee revisions (5.4% and 6.1%, respectively) and hip revisions (15.3% and 16.1%, respectively). However, IRFs served larger percentages of patients with bilateral knee replacements and hip replacements: 18% of IRF patients with knee replacement had a bilateral replacement versus 4% of freestanding SNF patients with knee replacement. Likewise, 3.5% of IRF patients with hip replacement had a bilateral replacement versus 0.5% of freestanding SNF patients with hip replacement. The hospital-based SNF had much lower rates of revisions and bilateral replacements than did the study's freestanding SNFs or IRFs.

In Table 4, Table 5 we partition the study group by type of replacement (knee or hip), by facility type (freestanding SNF, hospital-based SNF, or IRF), and by annual facility volume of joint replacement patients served—low, medium, high, and very high volume.

Table 4. Characteristics and Outcomes of Patients With Knee Replacements

Characteristic or Outcome	Fs-SNF				Hb-SNF‡	IRF				F or χ2∥	P
	Low Volume (n=45)	Medium Volume (n=187)	High Volume (n=121)	Total (n=353)	High Volume (n=189)	Medium Volume (n=297)	High Volume (n=363)	Very High Volume (n=199)	Total (n=859)
Demographics
Age (y)	72.5±8.3	74.8±7.5	69.8±10.2	72.8±8.8	73.1±7.1	70.1±9.9	70.3±10.1	69.5±10.3	70.0±10.1	8.69	<.001
Sex (% female)	80.0	70.6	76.9	74.9	72.0	70.7	76.6	65.8	72.1	10.76∥	.096
Race (% white)	100.0	95.7	39.7	77.3	97.9	90.2	69.4	81.4	79.4	257.34∥	<.001
Lived alone (%)	22.2	39.6	43.0	38.4	36.0	31.7	38.8	25.6	33.3	19.92∥	.003
Payer mix (% non-HMO Medicare)	82.2	81.3	81.8	81.6	79.9	73.4	70.5	79.4	73.6	16.01∥	.014
Health and functional status
Admission CSI⁎	16.8±11.7	21.7±11.2	29.6±8.5	23.8±11.3	28.6±7.9	28.5±12.7	31.9±14.9	25.2±11.4	29.2±13.6	23.57	<.001
BMI	31.5±5.8	31.4±6.3	35.5±8.1	32.9±7.2	34.4±7.9	32.6±6.8	33.0±7.7	31.9±6.5	32.6±7.1	6.26	<.001
Admission motor FIM	52.8±12.8	51.1±8.0	48.1±7.6	50.3±8.8	46.4±8.5	42.2±7.5	42.6±8.0	42.1±9.0	42.3±8.0	42.61	<.001
Discharge motor FIM	69.3±12.6	73.4±6.4	69.1±6.5	71.4±7.8	69.8±6.4	69.2±7.0	67.7±7.2	68.3±8.4	68.3±7.5	13.26	<.001
Change in motor FIM	16.5±9.5	22.2±8.1	21.1±6.3	21.1±7.9	23.5±7.6	27.0±7.5	25.1±7.6	26.1±8.3	26.0±7.8	22.36	<.001
Admission cognitive FIM	32.0±5.4	33.6±3.0	34.7±1.6	33.8±3.2	30.3±4.5	29.4±6.0	29.8±4.9	31.9±3.4	30.2±5.1	42.61	<.001
Onset days†	4.8±2.8	4.4±2.0	3.2±2.2	4.0±2.3	3.5±1.6	4.1±3.1	4.0±3.3	3.8±1.8	4.0±3.0	4.35	<.001
CMG (%)
801–802	80.0	73.3	62.0	70.3	67.2	48.8	47.1	52.8	49.0	77.35∥	<.001
803–804	8.9	20.9	28.9	22.1	23.3	30.6	36.9	36.7	34.7
805–806	11.1	5.9	9.1	7.7	9.5	20.5	16.0	10.6	16.3
Comorbidities (%)
Morbid obesity (BMI ≥40)	8.9	10.2	26.5	15.6	19.6	15.2	14.9	10.1	13.9	24.04∥	<.001
Hypertension	71.1	71.1	81.0	74.5	79.9	76.1	68.9	66.8	70.9	17.32∥	.008
Diabetes	31.1	14.4	28.1	21.3	28.0	24.2	20.4	22.1	22.1	15.72∥	.015
Ischemic heart disease	11.1	15.5	10.7	13.3	21.2	17.9	17.6	9.6	15.8	14.76∥	.022
Tier 1 (most severe)§	0.0	0.0	0.0	0.0	0.0	0.7	0.3	1.0	0.6	56.36∥	<.001
Tier 2 (moderately severe)	0.0	0.5	0.0	0.3	3.7	3.7	1.1	1.5	2.1
Tier 3 (mild)	4.4	16.6	8.3	12.3	15.3	21.2	27.6	19.6	23.5
Tier 0 (none on list of comorbidities)	95.6	82.9	91.7	87.4	81.0	74.4	71.1	77.9	73.8
Discharge destination (%)
To community¶	93.3	94.7	96.7	95.2	98.4	96.0	95.6	95.5	95.7	4.94∥	.552
To other settings	6.7	5.3	3.3	4.8	1.6	4.0	4.4	4.5	4.3
Process of care
LOS	16.1±8.2	13.7±7.6	13.3±6.0	13.9±7.2	8.8±3.3	8.0±3.5	9.9±4.1	8.3±2.8	8.9±3.7	55.71	<.001
Intensity#	1.2±0.5	1.1±0.2	1.4±0.3	1.2±0.3	1.5±0.2	2.2±0.5	2.0±0.4	2.0±0.3	2.1±0.4	307.90	<.001

Source: JOINTS study.

NOTE. Values are mean ± SD or as otherwise indicated.

Abbreviations: Fs-SNF, freestanding SNF; Hb-SNF, hospital-based SNF; HMO, Health Maintenance Organization.

Table 5. Characteristics and Outcomes of Patients With Hip Replacements

Characteristic or Outcome	Fs-SNF				Hb-SNF‡	IRF				F or χ2∥	P
	Low Volume (n=10)	Medium Volume (n=108)	High Volume (n=72)	Total (n=190)	High Volume (n=77)	Medium Volume (n=159)	High Volume (n=211)	Very High Volume (n=114)	Total (n=484)
Demographics
Age (y)	74.0±11.9	76.3±9.1	71.1±11.8	74.3±10.6	73.5±7.6	68.9±12.7	71.0±12.6	69.4±11.3	69.9±12.3	5.78	<.001
Sex (% female)	70.0	73.2	75.0	73.7	67.5	59.8	66.8	64.0	63.8	8.15∥	.227
Race (% white)	100.0	97.2	29.2	70.9	100.0	84.9	75.4	92.1	82.4	183.19∥	<.001
Lived alone (%)	10.0	46.3	36.1	41.2	31.2	30.8	39.3	29.0	34.1	14.01∥	.030
Payer mix (% non-HMO Medicare)	70.0	82.4	93.1	85.4	84.4	61.6	68.3	80.7	69.0	44.51∥	<.001
Health and functional status
Admission CSI⁎	13.9±9.2	11.5±8.1	22.3±7.9	15.7±9.6	15.1±8.7	19.3±13.1	23.0±13.1	19.9±11.8	21.0±12.9	15.15	<.001
BMI	27.4±5.1	28.9±6.1	31.8±6.4	29.9±6.3	30.6±6.8	30.1±7.2	29.0±6.6	29.3±6.0	29.5±6.7	2.39	.027
Admission motor FIM	43.8±14.0	47.5±8.2	47.8±7.3	47.4±8.2	46.0±8.2	39.2±8.2	38.9±8.6	39.3±8.7	39.1±8.4	26.08	<.001
Discharge motor FIM	61.9±22.5	70.9±7.4	68.0±8.4	69.4±9.3	69.3±6.3	66.9±7.3	64.0±10.3	65.9±8.6	65.4±9.1	9.48	<.001
Change in motor FIM	18.1±10.5	23.4±7.2	20.2±6.8	22.0±7.4	23.3±7.9	27.7±8.2	25.1±8.3	26.6±7.5	26.3±8.2	10.81	<.001
Admission cognitive FIM	29.8±5.9	32.6±4.7	34.5±3.1	33.2±4.4	30.0±3.1	28.7±5.6	28.0±6.4	31.0±3.6	29.0±5.7	26.08	<.001
Onset days†	6.4±4.9	4.9±3.3	3.0±2.4	4.3±3.2	3.5±1.5	4.3±2.0	4.7±4.4	3.6±1.8	4.3±3.3	6.14	<.001
CMG (%)
801–802	50.0	57.4	61.1	58.4	64.9	31.5	32.2	42.1	34.3	78.44∥	<.001
803–804	30.0	27.8	31.9	29.5	22.1	33.3	33.7	44.7	36.2
805–806	20.0	14.8	6.9	12.1	13.0	35.2	34.1	13.2	29.6
Comorbidities (%)
Morbid obesity (BMI ≥40)	0.0	4.6	13.9	7.9	10.4	6.9	4.7	5.3	5.6	10.84∥	.094
Hypertension	80.0	67.6	79.2	72.6	70.1	67.3	56.9	63.2	61.8	15.25∥	.018
Diabetes	30.0	13.0	19.4	16.3	22.1	25.2	16.1	12.3	18.2	12.29∥	.056
Ischemic heart disease	10.0	26.9	8.3	18.9	24.7	20.8	19.4	16.7	19.2	11.95∥	.063
Tier 1 (most severe)§	0.0	0.0	0.0	0.0	0.0	1.9	0.5	0.9	1.0	22.33∥	.218
Tier 2 (moderately severe)	0.0	0.9	0.0	0.5	1.3	1.3	2.8	1.8	2.1
Tier 3 (mild)	10.0	10.2	9.7	10.0	10.4	14.5	20.9	11.4	16.5
Tier 0 (none on list of comorbidities)	90.0	88.9	90.3	89.5	88.3	82.4	75.8	86.0	80.4
Discharge destination (%)
To community¶	70.0	94.4	100.0	95.3	97.4	96.2	82.9	95.6	90.3	47.62∥	<.001
To other settings	30.0	5.6	0.0	4.7	2.6	3.8	17.1	4.4	9.7
Process of care
LOS	17.5±8.3	16.1±8.8	11.7±8.0	14.5±8.7	8.9±3.5	9.6±5.2	11.2±5.1	8.6±3.4	10.1±4.6	24.14	<.001
Intensity#	1.1±0.5	1.1±0.2	1.3±0.3	1.2±0.3	1.5±0.2	2.1±0.5	2.0±0.4	1.9±0.3	2.0±0.4	139.30	<.001

Source: JOINTS study.

NOTE. Values are mean ± SD or as otherwise indicated.

Abbreviations: Fs-SNF, freestanding SNF; Hb-SNF, hospital-based SNF; HMO, Health Maintenance Organization.

The study's typical joint replacement patient was a woman in her early 70s with an average BMI in the low 30s (BMI ≥30 is obese). About 15% of patients were morbidly obese (BMI ≥40). About one third of all patients lived alone. SNF patients were on average almost 3 years older than their IRF counterparts.

IRF patients presented more severe medical and functional profiles on admission than SNF patients. IRF patients had higher CSI scores and lower FIM scores at admission. However, freestanding SNF and IRF patients presented similar rates of common comorbidities such as diabetes, hypertension, and ischemic heart disease; hospital-based SNF patients presented higher rates of these common comorbidities.

Because of their FIM scores, proportionately more SNF patients fell into one of the lower, less severe CMGs (801–802), while IRF patients, compared with SNF patients, were more likely to fall into 1 of the 4 more severe CMGs (803–806). For a definition of CMGs, see table 3 in the accompanying article by DeJong et al.³

Medicare was the dominant payer for patients in all 3 types of facilities and for both types of joint replacement. Non-Health Maintenance Organization Medicare was more common among freestanding SNF and hospital-based SNF patients (≈ 81%–84%) than among IRF patients (≈71%). IRFs had a more diverse payer mix with more patients who were enrolled in Medicaid or a commercial health plan, possibly because study IRFs served a slightly younger cohort, some of whom were not eligible for Medicare.

Process of Care 

The typical patient with joint replacement came to an SNF or an IRF after a 4-day LOS in acute care. The average LOS for freestanding SNF patients, hip and knee combined, was 14.1 days, for hospital-based SNF patients 8.8 days, and for IRF patients about 9 to 10 days depending on whether the patient had a knee replacement (8.9d) or a hip replacement (10.1d). On a case-mix–adjusted basis, the average LOS for freestanding SNF patients was much longer than for IRF patients (see table 4 in the accompanying article by DeJong³).

An important difference between freestanding SNFs and IRFs is that freestanding SNFs provided less intensive services (h/d) over a longer period; IRFs provided more intensive services in a shorter period. Freestanding SNFs demonstrated a wider variation in LOS and intensity of therapy relative to IRFs. (For more on processes of care, see DeJong,³ especially fig 1).

Outcomes 

Table 4, Table 5 indicate that, as measured by motor FIM, SNF patients entered rehabilitation at higher functional levels and left at higher functional levels; IRF patients entered at lower levels and left at lower levels. Overall, without case-mix adjustment, IRFs demonstrated larger gains in motor FIM scores than did freestanding SNFs for both patients with knee replacement (26.0 vs 21.1; P<.001) and patients with hip replacement (26.3 vs 22.0; P<.001).

There also were striking differences by facility volume. While there was little variation among IRFs in FIM gain, the 5 medium-volume IRFs (100–183 patients a year) had the largest gains from admission to discharge (27.0 for patients with knee replacement, 27.7 for patients with hip replacement). At the other extreme, 4 low-volume freestanding SNFs (20–45 patients a year) had the smallest FIM gains from admission to discharge (16.5 for patients with knee replacement, 18.1 for patients with hip replacement). There was nearly a 10-point spread in motor FIM gain between medium-volume IRFs and low-volume freestanding SNFs. The 3 medium-volume freestanding SNFs performed best among SNFs (22.2 for patients with knee replacement, 23.4 for patients with hip replacement).

Study IRFs achieved larger gains in shorter lengths of time and therefore demonstrated higher LOS efficiencies—that is, achieved more FIM gains a day—than did their SNF counterparts. The 5 medium-volume IRFs not only had the largest gains but also had shorter average LOS and therefore, as a class of facilities, had the highest LOS efficiencies.

The study's hospital-based SNF performed in the middle of the pack. In terms of FIM gain, the hospital-based SNF had higher motor FIM gains than study freestanding SNFs but lower gains than study IRFs. It achieved its FIM gains in an average of 8.8 days, making it more LOS-efficient than study freestanding SNFs.

We present 3 sets of regressions in Table 6, Table 7, Table 8. All tables convey essentially the same findings, but their juxtaposition provides useful insights. The 2 most important patient predictors were the patient's admission motor and cognitive FIM scores. The next most important patient predictor was the patient's onset days (days from actual joint replacement to admission to postacute rehabilitation). Postacute setting explained less of the variation in outcomes.

Table 6. Results of OLS Regression Analysis in Predicting Discharge Motor FIM Score Using Setting (Regression Model 1)

Source: JOINTS study.

Abbreviation: NA, not applicable.

*In this regression model, the hospital-based SNF is combined with freestanding SNFs. This regression model compares all SNFs with all IRFs.

Table 7. Results of OLS Regression Analysis in Predicting Discharge Motor FIM Score Using Therapy Intensity (Regression Model 2)

Source: JOINTS study.

NOTE. Therapy intensity is total hours of PT and OT combined, divided by LOS.

Abbreviation: NA, not applicable.

Table 8. Results of OLS Regression Analysis in Predicting Discharge Motor FIM Score Using Facility Type by Facility Volume but Not Therapy Intensity (Regression Model 3)

Source: JOINTS study.

Abbreviations: Fs, freestanding; NA, not applicable; vol., volume.

In regression model 1 (see table 6), in which we only considered patient characteristics and setting, IRF entered positively (P=.014 for patients with knee replacement and P=.005 for patients with hip replacement). R² values were 0.325 for patients with knee replacement and 0.458 for patients with hip replacement. Table 6 combines the hospital-based SNF with the freestanding SNFs and thus compares all SNFs with IRFs. When we treat the hospital-based SNF as a setting distinct from freestanding SNFs, IRFs enter more positively, but all other relationships remain the same.

Regression model 2 (see table 7) refines model 1 by also considering other facility characteristics and process variables. We found that volume and therapy intensity—a defining difference between SNFs and IRFs––made a difference in outcome: those who received more intense therapy, akin to what is found in an IRF, had, on average, larger FIM gains (see table 7). When setting and therapy intensity are included in the same model as in table 7, therapy intensity masks the setting effect seen in table 6. More important, however, was the role of facility volume: medium-volume facilities demonstrated better risk-adjusted outcomes and low-volume facilities demonstrated worse risk-adjusted outcomes (for knee patients). Table 7 considers the hospital-based SNF as a distinct setting.

In regression model 3 (see table 8), we exclude therapy intensity because of its strong association with setting (eg, r=.711 among IRF patients with knee replacement), and instead considered volume-by-setting combinations as distinct facility types. We found that medium-volume IRFs had better outcomes and low-volume freestanding SNFs had worse outcomes as observed in descriptive analyses in Table 4, Table 5. The spread between medium volume IRFs and low-volume freestanding SNFs was 4.6 motor FIM points for patients with knee replacement and 7.3 motor FIM points for patients with hip replacement. The results in table 8 suggest that facility volume differences observed in table 7 are driven mainly by medium-volume IRFs and low-volume freestanding SNFs. Among patients with knee replacement, medium-volume freestanding SNFs outperformed other freestanding SNFs as well as higher-volume IRFs. Findings in table 8 offer further explanation for the results found in Table 6, Table 7. Table 8 considers the hospital-based SNF as a distinct setting.

Multivariate analyses confirm the descriptive analyses, that facility type and volume are associated with discharge motor FIM scores after accounting for patient differences and differences in onset days. Regressions in Table 6, Table 7, Table 8 explained about one third of the variation in outcomes among patients with knee replacement and nearly one half of the variation in outcome among patients with hip replacement. We ran models both with and without the hospital-based SNF, and the findings were the same. The hospital-based SNF itself was never a predictor (negative or positive) of outcome.

In the logistic regression analyses, where FIM gain is treated as a dichotomous variable, we found the same predictor variables entered in both OLS and logistic regression models. With the exception of model 3, in which medium-volume SNFs are positively associated with knee replacement outcomes, all models suggest either IRF setting or characteristics correlated with IRFs (eg, intensity of therapy) are associated with better functional outcomes.

Figure 1 summarizes the findings from models 1 and 3, in which setting effects were observed. For each model, figure 1 depicts the mean values associated with the setting effects and their 95% confidence intervals. Figure 1 also underscores the wider range of outcome values seen in SNFs than in IRFs.

Among patients with knee replacement, there was virtually no difference between SNFs and IRFs in whether a patient was discharged to a community or institutional setting. This was not always the case with patients with hip replacement: patients discharged from low-volume freestanding SNFs were less likely to go home (70%), while more than 95% of patients from other facilities returned to the community. The only exception was among high-volume IRFs, where 82.9% went home.

Back to Article Outline

Discussion 

The study's principal question is how type of setting is associated with functional outcomes at discharge. In the descriptive analyses, IRF patients present more medical acuity and more functional limitation on admission, and make larger gains. In multivariate analyses, the relationship continues to hold when IRF is allowed to enter the model, although the IRF advantage overall is modest. The relationship between setting and outcome is less direct when we consider therapy intensity. More intense therapy—for example, more hours of PT and OT a day, seen in IRFs—is associated with better outcomes.

Annual facility volume of patients with joint replacement also plays a role, which becomes more pronounced when we consider its interaction with facility type. Low-volume and high-volume SNFs did not do as well as medium-volume SNFs and medium-volume IRFs. We were not able to test this finding with low-volume IRFs because the study's initial facility recruitment and selection strategies favored higher-volume facilities; low-volume SNFs came into the study because of difficulties in recruiting SNFs of any volume. We cannot say from this study what the minimum patient volume should be for a facility to be active in this patient segment and type of care.

This article examines outcomes across 3 settings of care. While there are noticeable differences among the 3 settings (eg, intensity of therapy), there are also noticeable differences within settings, especially among freestanding SNFs. We found significant variation in days from surgery to freestanding SNF admission (onset days), freestanding SNF LOS, intensity of therapy, and outcomes. As in the Buntin et al⁴ study, we found larger SDs in SNF LOS than in IRF LOS. Study IRFs demonstrated a more consistent set of practice patterns and outcomes.

This study corroborates findings from other studies. For example, we found that obesity, while a potential risk factor for joint replacement itself, was not strongly associated with outcomes.²⁸, ²⁹, ³⁰, ³¹ Likewise, higher patient volume is associated with better outcomes for many conditions and procedures including total knee replacement,³² total hip replacement,³³ pelvic reconstructive surgery,³⁴ total shoulder replacement,³⁵ intensive care,³⁶ diabetic care,³⁷ scoliosis with spinal fusion,³⁸ and coronary artery bypass surgery.³⁹ While most of these studies show a linear relationship between volume and outcome, our study found a curvilinear relationship where medium volumes are associated with better outcomes.

Implications for Practice and Policy 

One needs to consider whether study findings, though statistically significant, also are significant from a clinical and policy perspective. Some differences may be a result of measurement error as well as true differences, and this is especially important when smaller differences are observed. Previous studies have suggested that increases of 2 FIM points are clinically important because they are associated with a reduction of 6 to 10 minutes of personal assistance a day.⁴⁰, ⁴¹, ⁴², ⁴³, ⁴⁴, ⁴⁵ Clinical significance does not automatically translate into policy significance, however, because policy makers may be willing to tolerate a 2-point difference in the face of other considerations such as costs, a consideration that lies beyond the scope of this article. We can safely say, for example, that a 10-point difference in FIM gain is compelling; a 3 to 5 point difference is less so, but still material when one considers what this means for daily caregiver burden; a 2-point or smaller difference is less decisive.

While we started this study asking which setting of care provides superior functional outcomes for patients with joint replacement and though we find that the findings tilt in favor of IRFs, study results require a more nuanced interpretation. First, intensity of therapy is associated with outcomes—and facility type, SNF or IRF with their respective therapy intensities, needs to be considered when making a postacute placement. The fact that freestanding SNFs and IRFs provide, on average, similar amounts of total therapy,³ suggests even more strongly that intensity, as found in IRFs, is associated with better outcomes—at least at discharge. This finding is in keeping with previous research on patients with stroke served by IRFs⁴⁶ and research among patients with stroke, orthopedic, cardiovascular, and pulmonary conditions in SNFs.⁴⁷

Second, onset days—number of days from surgery to rehabilitation admission—is associated with motor FIM gain at discharge. Despite ever decreasing LOS in acute care, starting rehabilitation earlier is associated with better outcomes: every day counts. This finding corroborates the study by Munin et al⁴⁸ in which, in a limited randomized trial (N=71), they observed that patients with joint replacement who started rehabilitation on day 3 after a joint replacement had better functional outcomes than those who did not start until day 7. This finding suggests that more may need to be done to facilitate the hand-off from acute care to rehabilitation as early as possible.

Third, a facility's volume of patients with joint replacement is associated with outcome, and low volumes are associated with worse outcomes. Centers for Medicare and Medicaid Services and other health plans should consider excluding facilities that do not serve a certain minimum number of patients with joint replacement. Low-volume facilities not only had more onset days but also had worse outcomes after onset days were taken into account in regression analysis. It is possible that low-volume facilities cannot achieve the scale and proficiency needed to facilitate good outcomes. We observed that medium-volume facilities do best among both IRFs and SNFs, but we do not know where the sweet spots are between low and medium volumes or between medium and high volumes.

The volume effect also has implications for the 75%/60% rule cited in the introduction. Under the 75%/60% rule, smaller IRFs were unable to admit higher volumes of patients with joint replacement and achieve the specialization and proficiency needed for good outcomes. We need to underscore that we were unable to test this directly because small IRFs serving low volumes of patients with joint replacement were not represented in the study. Nonetheless, the 75% rule may have had unintended consequences when it restricted volumes of certain types of patients. This needs to be studied further, although the new 60% rule gives facilities greater latitude in who can be admitted and thus in achieving the volumes needed for more proficient care.

Fourth, we observed considerable within-setting variability, especially with respect to LOS, therapy intensity, and outcomes among SNFs. SNFs with the longest LOS and least intense services performed least well. These were predominantly low-volume SNFs. Medium-volume SNFs did much better. Thus, there may be important choices to be made within types of facilities as well as between types of facilities.

Finally, there is the question of how to view hospital-based SNFs—as a class by themselves or in a class with other SNFs. In our analysis of joint replacement rehabilitation processes,³ we observed noticeable differences between the hospital-based SNF and study freestanding SNFs. The presence of hospital-based SNFs obscures the comparison between the 2 payment systems, SNF-PPS and IRF-PPS. According to the Medicare Payment Advisory Commission, hospital-based SNFs have large negative margins (–83.8%).⁴⁹ Hospitals must make up their SNF costs from other payers—for example, the Medicare diagnosis-related group payment for acute care. In short, we may be comparing 3 payment systems—IRF-PPS, SNF-PPS, and SNF-PPS cross-subsidized by other payers. This indirect cross-subsidy blurs 1 of the key distinctions that motivated this study. Large negative hospital margins may also account for why there were 521 or 30% fewer hospital-based SNFs in 2006 than in 2001 and why they now comprise only 8.1% of all SNFs.

Study Limitations and Generalizability of Study Findings 

The study achieved geographic diversity by successfully enrolling SNFs and IRFs from all 4 of the nation's major census areas. However, all facilities participated voluntarily and thus self-selected into the study. In short, we have a convenience sample but a geographically diverse one. Low-volume IRFs, especially smaller IRF units in acute care hospitals, were not represented in the study, and their participation would have strengthened study findings with respect to low volumes and increased generalizability to all IRFs. Given variability and diversity of SNF practice patterns and lower numbers of SNF study patients, the study would have benefited from participation of more SNFs relative to IRFs. Overall, it is likely that the study attracted above-average facilities of both kinds. Thus, we recommend caution in generalizing to all SNFs and all IRFs nationally.

This study used a common outcome metric—motor FIM—to compare joint replacement rehabilitation outcomes across settings of care. FIM is not without its challenges, however. Scoring on some FIM items can vary with local practice patterns in how patient care is managed and thus observed. For example, if a patient is admitted with a temporary Foley catheter, the patient will have a lower FIM score than if he or she were admitted a day later without a catheter. The effects of such differences are probably marginal. Also, IRFs use FIM for payment purposes and are very familiar with its definitions and rules. SNFs do not use FIM regularly, so even with training and checking for reliability, they may not have been as accurate in FIM scoring throughout the project.

It is also important to underscore what this article does not address. First, this article does not address the effects of specific types of therapy activities (eg, exercise, gait, dressing upper body) that patients may have received. What is more important, perhaps, is not where patients obtain therapy, but what therapy patients actually receive regardless of the setting.⁵⁰ Then the setting or settings can be selected that are best able to deliver such care. While the JOINTS study is powered to answer this best practices question, we do not address it here. Second, this article does not address the role of nursing, a major component of the inpatient experience. While we attempted to collect nursing POC data, compliance was uneven. Third, while this article addresses outcomes and LOS efficiency (FIM gain/LOS), it does not address payment efficiency—for example, outcome per dollar payment or cost-effectiveness. Fourth, this article addresses only outcomes on discharge; it does not address longer-term outcomes at follow-up such as postdischarge complications, functional status, general health, hospital readmissions, and resumption of premorbid social roles.

To some extent, the SNF–IRF dichotomy presents an incomplete choice. It suggests that there has to be a winner and loser in the policy debate about the merits of SNF and IRF care for patients who have had a joint replacement. We already have suggested that patient volume may play a role among both SNFs and IRFs. Hence, the choice may not be just between SNF and IRF. There also may be important choices to be made within types of facilities.

The SNF–IRF dichotomy may also be a false choice. Another way to frame the issue is to ask which patients do better in an SNF, which do better in an IRF, and for which patients it makes little or no difference. This article does not address this question head on and is the subject of future analysis. We have framed this article largely in the context of the current policy debate.

SNF–IRF comparisons are not straightforward. Given the variation within these settings as well as between them, generalizations can only be made cautiously. Ideally, one might want to conduct a randomized trial, but these 2 settings lack the uniformity and consistency in practice—especially among SNFs—that a randomized trial presumes. Public policy would be well served if the focus could shift to what is best practice in both settings of care in order to identify a next generation of practice that transcends the SNF–IRF dichotomy.

Back to Article Outline

Conclusions 

Patients with joint replacement in study SNFs come in with higher functional scores and leave with higher functional scores than IRF patients. Study IRF patients, however, experience a larger net motor functional gain and achieve these gains in a shorter period. Multivariate analyses, controlling for patient differences and onset days, indicate that IRFs are associated with better outcomes, but the size of the setting effect is not large.

We found that therapy intensity, a practice feature strongly associated with IRFs, was positively associated with functional outcome. Apart from intensity effect, the study found that interaction between setting and annual volume of patients with joint replacement was a stronger predictor of outcome than setting alone. Medium volume SNFs and IRFs had better outcomes; high-volume and low-volume freestanding SNFs had worse outcomes. The study uncovered as much practice variation (in terms of therapy intensity and LOS) within settings, especially among SNFs, as between settings. Large practice variations within settings can obscure distinctions between settings.

In short, overall study findings favor IRF-level care, but the IRF advantage is not clear-cut. The choice of postacute setting also needs to take into account other important facility and practice characteristics such as therapy intensity and a facility's volume of joint replacement rehabilitation patients.

Supplier

Back to Article Outline

Acknowledgments 

We gratefully acknowledge the role and contributions of the clinical staffs at each of the 22 clinical sites represented in the JOINTS study. The site study's site directors included John Bishop, PT, and Erin Propst; Charles Schauer, PhD, and Flo Singletary, MA, CCC-SLP; Hilary Siebens, MD, and Harriet Aronow, PhD; Jacalyn Lichtenstein, RN, and Lynne Wright, RN; Julie Barth; Andrea Curry; Jon Nordrum, PT, Melissa P. Hake, PT, Donna Coughlin, PT, and Karen Kotval, RN; Santiago Toledo, MD; Robert Krug, MD, and Steve Kunsman; Robert Bowsher, MD, and Cynthia A. Kreutz; Barbara Higgins; John Jimenez; Gina Harris, PT, Natalie Russo, OT, and Marcy Howard; Steve Christensen and Lyle Black; Jean Russell, Elisa Freeman, and Andrea Maddux; Ann Cottrell, Dawn Haskell, PT, and MaryAnn Morrison, RN; Ellen Logsdon; Bernard Shore, MD, Cindy Lovetro, RN, Karen Rowlands, and Deborah Greco, LPN; Kathy Stover; Karen L. George, OT, Suzanne Besecker, Audrey Hartz, RN, Geraldine Essick, and Pragna Doshi, PT; Mary VandeKamp, SLP, MA-CCC, Vienna Lafrenz, OT, Glenda Mack, MSPT, Luanne L. Cunningham, and Jane Klugman, PT.

We acknowledge members of our staffs who also contributed significantly to the success of this study: Michael R. Brown, BA, Roberta James, MStat, Elizabeth Newman, OTD, OTR/L, Mary Foley, RN, Cathy Ellis, PT, Naomi Greenberg, PT, Deborah Hutton, OTR/L, and Josephine Kuofie, RN.

We also acknowledge the input and contributions of all members of the study's Policy Advisory Panel and the organizations they represent: Rosaly Correa-de-Arauio, MD, PhD; Barbara Manard; Robyn Stone, PhD; Rochelle Archuleta; Carolyn Zollar, JD; Mary Fran Delaune; Trudy Mallinson, PhD, and Anne Deutsch, PhD; Christine MacDonell; Barbara Braun, PhD; Elizabeth Sandel, MD; Susan Klanecky; Michael Weinrich, MD; Melinda Buntin, PhD; Reginald Warren, PhD; Leigh Callahan, PhD; Carl Granger, MD; and Michael Munin, MD. We also acknowledge those nonmembers of the Policy Advisory Panel who participated as observers because of their employment with policy-making agencies and funding sources: James Bowman, MD; Ruth Brannon and Philip Beatty; Dexanne Clohan, MD, Justin Hunter, JD, and John Markus, JD.

Back to Article Outline

References 

1. Merrill C, Elixhauser A. Hospital stays involving musculoskeletal procedures, 1997-2005. Rockville: Agency for Healthcare Research and Quality; 2007;
   • View In Article
2. Tian W, DeJong G, Brown M, Hsieh J, Zamfirov Z, Horn SD. Looking upstream: factors shaping the demand for postacute joint replacement rehabilitation. Arch Phys Med Rehabil. 2009;90:1260–1268
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (305 KB)
   • CrossRef
3. DeJong G, Hsieh CH, Gassaway J, et al. Characterizing rehabilitation services for patients with knee and hip replacement in skilled nursing facilities and inpatient rehabilitation facilities. Arch Phys Med Rehabil. 2009;90:1269–1283
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (3689 KB)
   • CrossRef
4. Buntin MB, Deb P, Escarce J, Hoverman C, Paddock S, Sood N. Comparison of Medicare spending and outcomes for beneficiaries with lower extremity joint replacements. In: Santa Monica: RAND Health; 2005;p. 1–44
   • View In Article
5. United States General Accountability Office. More specific criteria needed to classify inpatient rehabilitation facilities. Washington (DC): Government Accountability Office; 2005;
   • View In Article
6. Medicare Payment Advisory Committee. Report to the Congress: Issues in a modernized Medicare program. Chapter 5: Payment for Post-acute care. In: Washington (DC): MedPAC; 2005;p. 105–133
   • View In Article
7. Centers for Medicare and Medicaid Services. Changes to the criteria for being classified as an inpatient rehabilitation facility. Code of Federal Regulations. 42 Pt 412, Vol 69, No. 89 In: Washington (DC): Centers for Medicare and Medicaid Services; 2004;p. 25756–25776
   • View In Article
8. Tribe K, Lapsley H, Cross M, Courtenay B, Brooks P, March L. Selection of patients for inpatient rehabilitation or direct home discharge following total joint replacement surgery: a comparison of health status and out-of-pocket expenditure of patient undergoing hip and knee arthroplasty for osteoarthritis. Chronic Illn. 2005;1:289–302
   • View In Article
   • MEDLINE
   • CrossRef
9. Mahomed N, Koo Seen Lin M, Levesque J, Lan S, Bogoch E. Determinants and outcomes of inpatient versus home based rehabilitation following elective hip and knee replacement. J Rheumatol. 2000;27:1753–1758
   • View In Article
   • MEDLINE
10. Deutsch A, Granger C, Fiedler R. Outcomes and reimbursement of inpatient rehabilitation facilities and subacute rehabilitation programs for Medicare beneficiaries with hip fracture. Med Care. 2005;43:892–901
    • View In Article
    • MEDLINE
    • CrossRef
11. Deutsch A, Granger CV, Heinemann AW, et al. Outcomes and reimbursement of inpatient rehabilitation facilities and subacute rehabilitation programs. Stroke. 2006;37:1477–1482
    • View In Article
    • CrossRef
12. Kane RL, Chen Q, Blewett LA, Sangl J. Do rehabilitative nursing homes improve the outcomes of care?. J Am Geriatr Soc. 1996;44:545–554
    • View In Article
    • MEDLINE
13. Kane RL, Chen Q, Finch M. The optimal outcomes of post-hospital care under Medicare. Health Serv Res. 2000;35:615–661
    • View In Article
    • MEDLINE
14. Kane RL, Chen Q, Finch M, Blewett LA. Functional outcomes of posthospital care for stroke and hip fracture patients under Medicare. J Am Geriatr Soc. 1998;46:1525–1533
    • View In Article
    • MEDLINE
15. Kramer AM, Steiner JF, Schlenker RE. Outcomes and costs after hip fracture and stroke: a comparison of rehabilitation settings. JAMA. 1997;227:396–404
    • View In Article
16. Munin M, Seligman K, Dew M, et al. Effect of rehabilitation site on functional recovery after hip fracture. Arch Phys Med Rehabil. 2005;86:367–372
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (111 KB)
    • CrossRef
17. Walsh M, Herbold J. Outcome following rehabilitation for total joint replacement at IRF and SNF. Am J Phys Med Rehabil. 2006;85:1–5
    • View In Article
    • MEDLINE
    • CrossRef
18. DeJong G, Tian W, Smout RJ, et al. Use of rehabilitation and other health care services by patients with joint replacement after discharge from skilled nursing and inpatient rehabilitation facilities. Arch Phys Med Rehabil. 2009;90:1297–1305
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (247 KB)
    • CrossRef
19. DeJong G, Tian W, Smout RJ, et al. Long-term outcomes of joint replacement rehabilitation patients discharged from skilled nursing and inpatient rehabilitation facilities. Arch Phys Med Rehabil. 2009;90:1306–1316
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (286 KB)
    • CrossRef
20. Averill R, McGuire T, Manning B, et al. A study of the relationship between severity of illness and hospital cost in New Jersey hospitals. Health Serv Res. 1992;27:587–617
    • View In Article
    • MEDLINE
21. Clemmer T, Spuhler V, Oniki T, Horn SD. Results of a collaborative quality improvement program on outcomes and costs in a tertiary critical care unit. Crit Care Med. 1999;27:1768–1774
    • View In Article
    • MEDLINE
    • CrossRef
22. Horn SD, Sharkey P, Buckle J, Backofen J, Averill R, Horn R. The relationship between severity of illness and hospital length of stay and mortality. Med Care. 1991;29:305–317
    • View In Article
    • MEDLINE
    • CrossRef
23. Horn SD, Torres A, Willson D, Dean J, Gassaway J, Smout RJ. Development of a pediatric age and disease-specific severity measure. J Pediatr. 2002;141:496–503
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (133 KB)
    • CrossRef
24. Ryser D, Egger M, Horn SD, Handrahan D, Gandhi P, Bigler E. Measuring medical complexity during inpatient rehabilitation following traumatic brain injury. Arch Phys Med Rehabil. 2005;86:1108–1117
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (212 KB)
    • CrossRef
25. Willson D, Horn SD, Smout RJ, Gassaway J, Torres A. Severity assessment in children hospitalized with bronchiolitis using the pediatric component of the Comprehensive Severity Index. Pediatr Crit Care Med. 2000;1:127–132
    • View In Article
    • MEDLINE
    • CrossRef
26. Hamilton B, Granger C, Sherwin F. A uniform data system for medical rehabilitation. Baltimore: Brookes; 1987;
    • View In Article
27. Hamilton B, Laughlin J, Fiedler R. Interrater reliability of the 7-level functional independence measurement (FIM). Scand J Rehabil Med. 1994;26:115–119
    • View In Article
    • MEDLINE
28. Amin A, Patton J, Cook R, Brenkel I. Does obesity influence the clinical outcome at five years following total knee replacement for osteoarthritis. J Bone Joint Surg Br. 2006;88:335–340
    • View In Article
    • MEDLINE
    • CrossRef
29. Hamoui N, Kantor S, Vince K, Crookes P. Long-term outcome of total knee replacement: does obesity matter?. Obes Surg. 2006;16:35–38
    • View In Article
    • MEDLINE
    • CrossRef
30. Stickles B, Phillips L, Brox W, Owens B, Lanzer W. Defining the relationship between the obesity and total joint arthroplasty. Obes Res. 2001;9:219–223
    • View In Article
    • MEDLINE
31. Vincent HK, Weng JP, Vincent KR. Effect of obesity on inpatient rehabilitation outcomes after total hip arthroplasty. Obesity. 2007;15:522–530
    • View In Article
32. Hervey SL, Purves HR, Guller U, Toth AP, Vail TP, Pietrobon R. Provider volume of total knee arthroplasties and patient outcomes in the HCUP-nationwide inpatient sample. J Bone Joint Surg Am. 2006;85-A:1775–1783
    • View In Article
    • MEDLINE
33. Battaglia TC, Mulhall KJ, Brown TE, Saleh KJ. Increased surgical volume is associated with lower THA dislocation rates. Clin Orthop Relat Res. 2006;(Jun):29–33
    • View In Article
34. Sung VW, Rogers ML, Myers DL, Clark MA. Impact of hospital and surgeon volumes on outcomes following pelvic reconstructive surgery in the United States. Am J Obstet Gynecol. 2006;195:1778–1783
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (148 KB)
    • CrossRef
35. Lyman S, Jones EC, Bach PB, Peterson MG, Marx RG. The association between hospital volume and total shoulder arthroplasty outcomes. Clin Orthop Relat Res. 2005;(Mar):132–137
    • View In Article
36. Durairaj L, Torner JC, Chrischilles EA, Sarrazin MS, Yankey J, Rosenthal GE. Hospital volume-outcome relationships among medical admissions to ICUs. Clin Invest Crit Care. 2005;128:1682–1689
    • View In Article
37. Holmboe ES, Wang Y, Tate JP, Meehan TP. The effects of patient volume on the quality of diabetic care for Medicare beneficiaries. Med Care. 2006;44:1073–1077
    • View In Article
    • MEDLINE
    • CrossRef
38. Vitale MA, Arons RR, Hyman JE, Skaggs DL, Roye DP, Vitale MG. The contribution of hospital volume, payer status and other factors on surgical outcomes of scoliosis patients. J Pediatr Orthop. 2005;25:393–399
    • View In Article
    • MEDLINE
    • CrossRef
39. Nallamothu BK, Saint S, Hofer TP, Vijan S, Eagle KA, Bernstein SJ. Impact of patient risk on the hospital volume-outcome relationship in coronary artery bypass grafting. Arch Intern Med. 2005;165:333–337
    • View In Article
    • MEDLINE
    • CrossRef
40. Corrigan JD, Smith-Knapp K, Granger CV. Validity of the functional independence measure for persons with traumatic brain injury. Arch Phys Med Rehabil. 1997;78:828–834
    • View In Article
    • Abstract
    • Full-Text PDF (950 KB)
    • CrossRef
41. Disler PB, Roy CW, Smith BP. Predicting hours of care needed. Arch Phys Med Rehabil. 1993;74:139–143
    • View In Article
    • MEDLINE
42. Granger CV, Cotter AC, Hamilton BB, Fiedler RC. Functional assessment scales: a study of persons after stroke. Arch Phys Med Rehabil. 1993;74:133–138
    • View In Article
    • MEDLINE
43. Granger CV, Cotter AC, Hamilton BB, Fiedler RC, Hens MM. Functional assessment scales: a study of persons with multiple sclerosis. Arch Phys Med Rehabil. 1990;71:870–875
    • View In Article
    • MEDLINE
44. Granger CV, Divan N, Fiedler RC. Functional assessment scales. Am J Phys Med Rehabil. 1995;74:107–113
    • View In Article
    • MEDLINE
45. Hamilton BB, Deutsch A, Russell C, Fiedler RC, Granger CV. Relation of disability costs to function: spinal cord injury. Arch Phys Med Rehabil. 1999;80:385–391
    • View In Article
    • Abstract
    • Full-Text PDF (968 KB)
    • CrossRef
46. Horn SD, DeJong G, Smout RJ, Gassaway J, James R, Conroy B. Stroke rehabilitation patients, practice, and outcomes: is earlier and more aggressive therapy better?. Arch Phys Med Rehabil. 2005;86:S101–S114
    • View In Article
    • MEDLINE
47. Jette D, Warren R, Wirtalla C. The relation between therapy intensity and outcomes of rehabilitation in skilled nursing facilities. Arch Phys Med Rehabil. 2005;86:373–379
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (118 KB)
    • CrossRef
48. Munin M, Rudy T, Glynn N, Crossett L, Rubash H. Early inpatient rehabilitation after elective hip and knee arthroplasty. JAMA. 1998;279:847–852
    • View In Article
    • MEDLINE
    • CrossRef
49. Medicare Payment Advisory Committee. Section D: Skilled Nursing Services. Report to Congress: Medicare Payment Policy. In: Washington (DC): MedPAC; 2008;p. 153–154
    • View In Article
50. Kane R. Assessing the effectiveness of postacute care rehabilitation. Arch Phys Med Rehabil. 2007;88:1500–1504
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (84 KB)
    • CrossRef

• a SAS Institute, SAS 100 Campus Dr, Cary, NC 27513.