Methods and Procedures: This was a retrospective, comparative study ... Received 26 February 2007; accepted 10 May 2007. doi:10.1038/oby.2007.10 ... piled from medical records using the International Code of Diseases. (ICD-9) for each patient. ... total, pharmacy, occupational and physical therapy rehabilitation hos-.
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EPIDEMIology
Obesity and Inpatient Rehabilitation Outcomes Following Knee Arthroplasty: A Multicenter Study Heather K. Vincent1 and Kevin R. Vincent1 Objective: This multicenter study examined whether inpatient rehabilitation outcomes following total knee arthroplasty (TKA) were influenced by BMI. Methods and Procedures: This was a retrospective, comparative study conducted using a computerized medical database and medical records derived from TKA patients, at 15 independent rehabilitation hospitals (N = 5,428). Patients were separated into four groups based on BMI: non-obese (BMI < 25 kg/m2), overweight (25–29.9 kg/m2), moderately obese (30–40 kg/m2), severely obese (BMI ≥ 40 kg/m2). All patients completed an interdisciplinary inpatient rehabilitation program post-TKA. Total and individual functional independence measure (FIM) scores, length of stay (LOS), FIM efficiency scores, itemized hospital charges, and discharge disposition location, were collected. Results: The percentage of total FIM change was 7.5% greater by the time of discharge in the non-obese than in the very severely obese (P < 0.05). FIM efficiency was lowest in the severely obese as compared to the remaining groups (3.7 points (pts)/day vs. 4.0–4.3 pts/day; P = 0.044). The change in the motor FIM score from admission to discharge was 6.7–15.6% greater in the non-obese than in the remaining groups (P < 0.05). The changes in cognition FIM, toilet transfer and walking without assistance scores were higher in the non-obese as compared to the severely obese group (P < 0.05). The severely obese group had higher total, physical and occupational therapy and pharmacy charges than the remaining groups (P < 0.05). Discussion: An excessive BMI does not prevent gains during inpatient rehabilitation; however, these gains are made less efficiently and at a higher cost than those made when the BMI is low. Obesity (2008) 16, 130–136. doi:10.1038/oby.2007.10
Introduction
The prevalence of obesity is increasing globally (1). Secondary to the problem of excessive weight is the development of osteoarthritis and joint pain to knee and subsequent physical disability (1–3). An effective solution for painful osteoarthritis about this joint is to perform a total knee arthroplasty (TKA) (4), and obesity often leads to TKA (5). Following TKA, many patients benefit from inpatient rehabilitation services that can assist in improving functional independence and performing the activities of daily living and eventually allow for discharge to the least restrictive environment, preferably to the patient’s home. Recently, the Centers for Medicare Services has developed a reimbursement plan that will ultimately exclude rehabilitation reimbursement for TKA patients who have specific criteria, including a BMI value of 40 kg/m2) (18). obesity | VOLUME 16 NUMBER 1 | JANUARY 2008
Study variables Patient descriptive variables included age, gender and ethnicity. Physio logical measures performed at the time of admission to rehabilitation included a metabolic chemistry panel, complete blood count, vital signs, height and weight. The number and type of comorbidities were compiled from medical records using the International Code of Diseases (ICD-9) for each patient. The type of TKA procedure (primary or revision), TKA revision etiology (pain, mechanical and infection related reasons) and weight bearing status were obtained from medical records and confirmed from each medical chart by the surgeons’ discharge summary. Study outcome variables The criterion measures were the LOS, functional independence measure (FIM) scores and 18 subscores at admission and discharge, and total, pharmacy, occupational and physical therapy rehabilitation hospital charges. Functional improvement during inpatient rehabilitation is generally measured using the 18-item FIM (19). The FIM estimates performance of tasks that can be broadly categorized as activities of daily living, mobility, and cognitive domains. The FIM tool is an important representative measure of the overall success of the interdisciplinary rehabilitation program. The FIM tool is a validated measure to capture overall functional improvements (19). Cognition was included with the motor scores as the two major total scores included in the overall FIM score. As part of the FIM score were other specific scores for activities of daily living. While all 18 FIM subscores were collected for each patient, categories that related to lower body functioning included weight bearing transfers (bed to chair, tub/shower, toilet), level of independence for walking and stairs (20). As an estimate of the rate of functional gain made during the rehabilitation intervention, a FIM efficiency score was calculated. FIM efficiency was defined as the change in FIM from admission to discharge divided by the LOS (FIM efficiency = FIM points gained/total days). LOS, total hospital, pharmacy and individual therapy charges were obtained from medical records. Discharge disposition locations were determined from the case management section within the patient charts. Patients were discharged to one of four locations: home, a skilled nursing facility, acute transfer back to the hospital, or assisted living. Rehabilitation intervention During the rehabilitation program, each patient completed a comprehensive interdisciplinary inpatient rehabilitation under the supervision of a physiatrist and therapy team. Each patient received ~3 h of supervised therapy daily from both physical and occupational therapists. This rehabilitation plan is summarized in Table 1. Standardized protocol driven therapy sessions were conducted twice daily, once in the morning and afternoon. During therapy sessions, patients engaged in activities to increase flexibility and range of motion, improve independence in performing activities of daily living, and to improve proprioception, gait and balance. Statistical analyses Statistical analyses were performed using the Statistical Package for the Social Sciences software (version 14.0). All data are expressed as mean ± s.d. of measurement. Frequency distribution of diagnosis etiologies, ethnicities, smoking and alcohol use, comorbidity types and disposition locations were analyzed using Chi-Square tests (χ2). Since there were four groups of different sample sizes, non-parametric Kruskal–Wallis tests were used to determine whether differences existed among the groups for outcome variables. Given that our previous work has shown that TKA type (primary vs. revision) influences TKA outcomes, we examined the potential interactions between the BMI group and TKA status on the main outcome variables of admission and discharge FIM scores, FIM efficiency, LOS and total charges by applying a univariate ANOVA with the group factors of BMI group and TKA status in this study. Significant interactions 131
articles EPIDEMIology are presented. Hierarchal linear regression models were generated to examine whether BMI was a significant contributor to the models predicting LOS, FIM efficiency and total hospital charges. Models were adjusted for several factors that influence these outcomes (age, gender, race, revision status, race, comorbidity number, admission
hematocrit) (13,14,21). The α level was established at 0.05 a priori for all statistical tests.
Table 1 Inpatient rehabilitation intervention performed by all study participants. Each therapy program required ~3 h of therapy daily
Characteristics and comorbidities of the study sample are shown in Table 2. The severely obese group contained a greater proportion of younger, shorter, female patients and African Americans than the non-obese and moderately obese groups (P < 0.05). Similarly, resting glucose levels were also higher in the severely obese than in the non-obese or moderately obese groups (P 0.05); patients in the severely obese group had a higher prevalence of revisions, particularly related to mechanical reasons. Frequencies of patients instructed for specific weight bearing status were also not different among BMI groups. Fasting glucose levels were 5.1–15.5% higher in the severely obese group than the non-obese and moderately obese groups (P < 0.05); admission hematocrit values ranged from 30.2 to 30.5% with no difference among groups (P > 0.05). Comorbidities of the patient sample were collected. Major comorbidities included diabetes mellitus, rheumatoid arthritis, peripheral arterial disease, hypertension, congestive heart failure, anemia, hypothyroidism, cellulitis, urinary tract infection, neuropathy, depression and anxiety. The prevalence of these comorbidities were not different among the four groups (the lowest P value for the χ2 tests of these distributions was 0.189), indicating homogeneity among the study groups.
Occupational therapy Activities of daily living for 30–45 min in the morning session Dressing Bathing Adaptive strategies and usage of assistive equipment Group activities Upper extremity activities (e.g., ball bouncing, stretching) Advanced activities (3× week, 30–60 min/session) Physical therapy (morning and afternoon sessions) Group sessions (60 min) therapist: patient ratio averaged 1:3 Therapy protocols Seated leg raises Isometric contractions for the ankle (gastrocnemius, quadriceps, gluteus maximus) Heel slides (hip flexors, biceps femoris) Terminal knee extensions Hip abduction (as long as it is not contraindicated) Gait walking or walking with cane Stair climbing Speech therapy (if required) Dysphagia therapy, cognitive therapies Psychotherapy was provided on a case by case basis if needed, if depressive, anxiety or adverse symptoms were present
Results Patient characteristics
Table 2 Patient characteristics for all BMI groups Non-obese (n = 2,267)
Overweight (n = 2,240)
Moderately obese (n = 740)
Severely obese (n = 173)
P value
Women (%)
73.9
63.7
69.2
80.1
0.0001
Age (year)
a
74.3 (9.6)
73.1 (9.3)
68.9 (9.7)
63.1 (8.5)
Height (cm)
164.0 (9.7)
164.5 (10.0)
163.0 (10.0)
160.0 (10.3)a
0.0001
Weight (kg)
64.6 (9.4)
77.8 (10.2)
94.2 (13.3)
121.5 (18.3)
0.0001
BMI (kg/m2)
22.6 (2.1)
27.5 (1.4)
34.2 (2.8)
45.9 (5.3)a
0.0001
Ethnicity (%) Caucasian African American Hispanic
59.7 8.9 29.2
53.4 13.6 31.4
49.9 15.7 31.2
49.2 18.4c 29.6
0.0024
Unilateral/bilateral TKA (%)
0.0001
a
a
89.4/10.6
83.3/16.7
79.5/20.5
80.6/19.4
0.109
TKA etiology (%) Primary Revision mechanical Revision infection Revision pain
87.0 9.8 2.9 0.4
83.3 13.5 1.5 1.7
79.5b 16.2 1.8 2.4
80.7b 16.4 0.8 2.0
0.019
Weight bearing status As tolerated Partial Non-weight bearing
90.9 8.8 0.4
91.8 8.1 0.1
92.3 7.2 0.5
93.0 6.7 0.3
0.750
Values are mean (s.d.) or percentage of the study group. TKA, total knee arthroplasty. a Different from all remaining groups. bDifferent from non-obese, moderately obese groups. cDifferent from non-obese at P < 0.05. 132
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articles EPIDEMIology Table 3 Inpatient rehabilitation outcomes for all BMI groups following TKA
Admission FIM (pt) Discharge FIM (pt) FIM change (%) LOS (days) FIM efficiency (pts/day) Total charges (USD) Physical therapy charges (USD) Occupational therapy charges (USD) Pharmacy charges (USD) Daily charges (USD) Discharge disposition (% to home, SNF, AC)
Non-obese (n = 2,267)
Overweight (n = 2,240)
Moderately obese (n = 740)
Severely obese (n = 173)
70.5 (69.0–72.1) 105.0 (103.3–106.6) 51.6 (47.9–55.3)a 10.3 (9.7–10.8)b 4.1 (3.8–4.5) 13,673 (12,864–14,483)b 2,658 (2,500–2,816)b 1,838 (1,719–1,958) 1,183 (1,010–1,356) 1,346 (1,321–1,370) 88.6/5.9/5.0
71.1 (70.2–72.1) 105.4 (104.4–106.4) 52.4 (50.1–54.6)b 9.7 (9.3–10.0) 4.3 (4.1–4.5) 13,179 (12,690–13,668) 2,507 (2,411–2,602) 1,786 (1,714–1,858) 1,237 (1,132–1,342) 1,354 (1,339–1,369) 94.9/2.2/2.7
71.6 (70.9–72.3) 103.9 (103.2–104.7) 48.6 (46.9–50.3) 9.5 (9.2–9.7) 4.0 (4.1–4.4) 13,014 (12,643–13,385) 2,452 (2,380–2,525) 1,791 (1,736–1,846) 1,321 (1,762) 1,372 (1,361–1,383) 93.1/2.2/4.5
71.2 (70.2–72.3) 103.0 (101.9–104.1) 47.6 (45.1–50.1) 9.7 (9.3–10.1) 3.7 (3.8–4.3)a 13,516 (12,965–14,066) 2,542 (2,435–2,650) 1,875 (1,794–1,957)b 1,459 (1,247)b 1,382 (1,366–1,400)b 92.7/3.9/2.8
Values are mean (95% confidence intervals). AC, acute care transfer; FIM, functional independence measure; LOS, length of stay; SNF, skilled nursing facility; TKA, total knee arthroplasty; USD, US dollars. a Different from severely obese. bDifferent from all remaining groups at P < 0.05.
Table 4 FIM categories and lower body activity FIM subscores for all BMI groups following TKA FIM component Non-obese Overweight
Moderately Severely obese obese
Motor score Admission (pts) Discharge (pts) Change (pts)
40.66 (8.5) 41.06 (9.4) 68.78 (9.2) 69.10 (8.2) 30.52 (13.7)a 28.58 (12.5)
Cognition score Admission (pts) Discharge (pts) Change (pts)
28.27 (5.6) 31.43 (4.3) 3.28 (4.8)a
28.49 (5.5) 31.46 (3.9) 3.07 (4.4)
28.48 (5.9) 31.39 (4.5) 2.76 (4.6)
28.44 (5.8) 31.20 (5.0) 2.54 (4.0)
Stairs Admission (pts) Discharge (pts) Change (pts)
1.17 (0.8) 4.22 (1.9) 3.04 (1.9)
1.20 (0.8) 4.11 (1.9) 2.91 (1.9)
1.19 (0.8) 4.05 (1.9) 2.86 (1.9)
1.18 (0.7) 4.06 (1.9) 2.99 (1.8)
41.50 (9.3) 41.27 (9.1) 67.82 (10.2) 67.32 (10.2) 27.74 (12.2) 26.39 (11.1)
Tub-shower transfer Admission (pts) Discharge (pts) Change (pts)
1.52 (1.1) 4.72 (1.7)a 3.19 (1.9)
1.50 (1.2) 4.62 (1.7) 3.11 (1.9)
1.52 (1.2) 4.52 (1.8) 3.01 (2.0)
1.48 (1.2) 4.51 (1.7) 2.95 (1.9)
Toilet transfer Admission (pts) Discharge (pts) Change (pts)
3.12 (1.2) 5.77 (0.7)a 2.33 (1.2)a
3.30 (1.3) 5.72 (0.8) 2.28 (1.2)
3.32 (1.4) 5.66 (0.9) 2.22 (1.1)
3.21 (1.3) 5.58 (1.1) 2.09 (1.1)
Bed/chair transfer Admission (pts) Discharge (pts) Change (pts)
3.11 (1.1) 5.76 (0.7) 2.57 (1.2)
3.13 (1.1) 5.80 (0.7) 2.51 (1.2)
3.17 (1.1) 5.68 (0.9) 2.45 (1.2)
3.18 (1.0) 5.66 (1.0) 2.47 (1.1)
Lower body dressing Admission (pts) 2.49 (1.1) Discharge (pts) 5.51 (1.0)a 3.05 (1.3) Change (pts)
2.44 (1.1) 5.42 (1.1) 3.02 (1.3)
2.53 (1.1) 5.40 (1.2) 2.83 (1.4)
2.48 (1.1) 5.36 (1.2) 2.89 (1.4)
Walking without assistance Admission (pts) 1.76 (1.2) Discharge (pts) 5.50 (1.3)a 3.65 (1.6)a Change (pts)
1.86 (1.3) 5.40 (1.4) 3.57 (1.6)
1.86 (1.2) 5.31 (1.5) 3.45 (1.7)
1.90 (1.3) 5.34 (1.6) 3.42 (1.7)
Values are mean (s.d.). Change scores represent the mean difference between the discharge and admission scores for each FIM subscore. FIM, functional independence measure; pts, points; TKA, total knee arthroplasty. a Different from severely obese at P < 0.05.
BMI and functional outcomes
The raw FIM scores from admission to discharge and score changes (Discharge FIM–Admission FIM), LOS, FIM efficiency obesity | VOLUME 16 NUMBER 1 | JANUARY 2008
Table 5 Select inpatient rehabilitation outcomes when analyzed by BMI and primary/revision total knee arthroplasty status Moderately obese (n = 740)
Severely obese (n = 173)
51.5 (27.1) 56.8 (36.8)
48.7 (28.9) 48.2 (32.9)
46.5 (24.7) 52.7 (38.0)
9.7 (4.5) 9.5 (4.1)
9.5 (4.3) 9.3 (4.2)
9.5 (4.5) 10.7 (4.5)
FIM efficiency (pts/day) Primary 4.09 (2.5) Revision 4.45 (3.1)
4.29 (2.6) 4.44 (2.9)
4.28 (2.9) 4.03 (3.1)
4.19 (3.0) 3.52 (2.6)
Total charges (USD)a 13,812 Primary (6,799) 12,753 Revision (5,339)
13,246 (6,602) 12,844 (5,914)
13,108 (6,611) 12,652 (6,083)
13,192 (6,601) 14,873 (6,608)
1,793 (971) 1,785 (835)
1,802 (996) 2,185 (1,089)
Non-obese Overweight (n = 2,267) (n = 2,240) FIM change (%) Primary 51.3 (24.6) Revision 53.9 (29.9) LOS (days)a Primary Revision
10.5 (5.2) 9.2 (3.8)
Occupational therapy changes (USD)a Primary 1,853 (997) 1,788 (960) Revision 1,741 (890) 1,777 (862)
Values are means (s.d.). FIM, functional independence measure; LOS, length of stay; USD, US dollars. a Significant interaction for total knee arthroplasty status and BMI group at P
