Orthopedics

Assessment of Postoperative Vigor in Patients Undergoing Elective Total Joint Arthroplasty: A Concise Patient- and Caregiver-Based Instrument

E Michael Keating, MD; Chitranjan S Ranawat, MD; William Cats-Baril, PhD

Abstract

ABSTRACT

Assessment of early postoperative recuperative power (i.e., vigor and functional ability) in surgery patients is considered to be important for optimizing patient rehabilitation, discharge planning, and health system resource utilization. However, no broadly accepted method of patient assessment has been available to measure these parameters. Therefore, a panel of experts was assembled to design an instrument to assess recuperative power in the total joint arthroplasty setting. The instrument consists of both subjective, patient-based, preoperative and postoperative, fixedended questions and objective, caregiver-based measures of patient function (i.e., muscle strength and hematocrit [HCT]). The prototype instrument employed the vitality subscale of the Short Form-36 (SF-36), the activities of daily living items from the Western Ontario and McMaster University Osteoarthritis Index (WOMAC-ADL), as well as three novel scales: Well-being, Ready to resume activities, and Ready to leave the hospital. The instrument was tested in 65 patients at two medical centers. The reliability and validity of the three novel psychometric scales were tested by measuring internal consistency and validity by comparison with the standard scales. Postoperative patient Well-being and Ready scales correlated strongly with muscle strength (P < .01), while postoperative HCT correlated with muscle strength (r = 0.4) and Ready scale (P < .01 ). This analysis suggested that patient well-being and readiness to resume normal activities may be the best surrogates of patient vigor and that these parametric assessments correlate well with functional and laboratory measures of vigor (i.e., muscle strength and HCT). Based on these findings, the final instrument (Version 4.2) consists of a patient questionnaire that can be completed within approximately 5 minutes (12 preoperative and 14 postoperative questions), and a caregiver questionnaire that includes two objective functional tests: muscle strength and HCT. In conclusion, postoperative vigor may be able to be assessed with a concise, patient-based instrument and may provide valuable information for rehabilitation and discharge planning. The utility of this instrument is currently being assessed in a prospective clinical study.

Abstract

ABSTRACT

Assessment of early postoperative recuperative power (i.e., vigor and functional ability) in surgery patients is considered to be important for optimizing patient rehabilitation, discharge planning, and health system resource utilization. However, no broadly accepted method of patient assessment has been available to measure these parameters. Therefore, a panel of experts was assembled to design an instrument to assess recuperative power in the total joint arthroplasty setting. The instrument consists of both subjective, patient-based, preoperative and postoperative, fixedended questions and objective, caregiver-based measures of patient function (i.e., muscle strength and hematocrit [HCT]). The prototype instrument employed the vitality subscale of the Short Form-36 (SF-36), the activities of daily living items from the Western Ontario and McMaster University Osteoarthritis Index (WOMAC-ADL), as well as three novel scales: Well-being, Ready to resume activities, and Ready to leave the hospital. The instrument was tested in 65 patients at two medical centers. The reliability and validity of the three novel psychometric scales were tested by measuring internal consistency and validity by comparison with the standard scales. Postoperative patient Well-being and Ready scales correlated strongly with muscle strength (P < .01), while postoperative HCT correlated with muscle strength (r = 0.4) and Ready scale (P < .01 ). This analysis suggested that patient well-being and readiness to resume normal activities may be the best surrogates of patient vigor and that these parametric assessments correlate well with functional and laboratory measures of vigor (i.e., muscle strength and HCT). Based on these findings, the final instrument (Version 4.2) consists of a patient questionnaire that can be completed within approximately 5 minutes (12 preoperative and 14 postoperative questions), and a caregiver questionnaire that includes two objective functional tests: muscle strength and HCT. In conclusion, postoperative vigor may be able to be assessed with a concise, patient-based instrument and may provide valuable information for rehabilitation and discharge planning. The utility of this instrument is currently being assessed in a prospective clinical study.

INTRODUCTION

The American Academy of Orthopaedic Surgeons (AAOS) has developed patient-based instruments to measure the surgical outcome of orthopedic care; however, no broadly accepted, patient-based instrument or method has been available to assess early postoperative recuperative power (i.e., vigor, functional ability) following major orthopedic surgery. This information could be useful for rehabilitation and discharge planning. A recent report by Munin et al1 has demonstrated that early intensive rehabilitation resulted in shorter mean hospital stay and more rapid attainment of short-term functional milestones. An instrument that could assess a patient's readiness and ability to rehabilitate could potentially impact functional outcome and health system resource utilization. We, therefore, sought to develop a concise patient-based instrument in order to validate an instrument designed to assess early postoperative vigor that would complement the AAOS "core" items.

A variety of instruments have been developed to assess patients' perceptions about their physical and emotional or psychosocial well-being over the long term. Instruments, such as the Short Form-36 (SF-36), are general and can be used in a variety of settings,2 whereas other instruments, such as the Western Ontario and McMaster University Osteoarthritis Index (WOMAC),3 the Sickness Impact Profile (SIP),4 the Musculoskeletal Function Assessment (MFA),5 and the Iowa Level of Assistance Scale (ILAS),6 are designed specifically for patients with musculoskeletal diseases such as osteoarthritis. The primary outcome measures are pain and stiffness, physical function, and emotional or psychosocial well-being. Patient self-assessment has been validated as a reliable measure of these factors.5,7,8 These instruments provide a reliable and valid assessment of long-term clinical outcome following surgical intervention.5,9

The postoperative hematocrit (HCT) level is one of the key clinical variables postulated to impact early patient vigor. Low HCT levels are a common postoperative problem in patients undergoing major orthopedic surgery (both elective and emergent), particularly with the institution of lower transfusion triggers. A primary consequence of low HCT is fatigue,10 which has been shown to be negatively associated with measures of vigor in other patient populations.11 Consequently, HCT levels, easily measurable in clinical practice, may serve as a useful surrogate laboratory measure of vigor.

Therefore, the objectives of this study were to develop and begin to validate an instrument that would provide both subjective and objective information concerning early postoperative vigor in the total joint arthroplasty setting.

MATERIALS AND METHODS

Instrument Development. A multidisciplinary panel of experts was convened in December 1996 to identify psychometric and objective functional surrogates of patient vigor in the total joint arthroplasty setting. The panel included representation from orthopedic surgery (five members), rheumatology/internal medicine (one member), physical therapy (one member), orthopedic nursing (one member), the insurance industry (one member), and health economics (two members). Candidate items were identified and selected for inclusion in the prototype vigor assessment instrument. Domains of vigor were defined as energy level; readiness to leave the hospital; and ability to perform activities of daily living. Based on these definitions, items were selected from two existing scales (the vitality subscale of the SF36 and the activities of daily living items from the WOMAC scale [WOMAC-ADL]), and new items were created. Objective tests of physical strength and energy were also identified. The selected items formed the basis of pre- and postoperative patient and caregiver questionnaires. Although patient self-assessment provides the most accurate measure of patient well-being, the panel suggested development of a caregiver measure to compliment the patient self-assessment scale.

Study Design. An initial pilot test of the selected items was conducted in 15 patients at two large surgical centers that specialize in total joint arthroplasty. Items were evaluated for level of endorsement, understandability, and readability. Items that showed little variability were eliminated. Factor analysis of the remaining items was used to develop a prototype instrument consisting of five scales.

The prototype instrument was developed and tested on 65 patients to determine the performance, reliability, and validity of each scale. Preoperative questionnaires were mailed to patients 10 days before surgery. Patients were asked to complete the questionnaires prior to admission and again on the day of admission. Postoperative questionnaires were completed by patients and caregivers either 4 days after surgery or at discharge. Objective tests, including pulmonary function, distance walked, muscle strength, HCT, temperature and heart rate, were performed as part of the day of admission assessment and at the postoperative assessment. Pulmonary function, distance walked, and muscle strength are well-established measures of functional ability and physical strength. HCT was included as an objective laboratory measure of vigor because of the well-established correlation between anemia and energy level.12,13

Based on the results of the pilot study, items were refined and simplified for inclusion in the prototype instrument. Factor analysis of the patient preoperative data set resulted in the formation of three scales (Table 1). The first two scales contained 4 selected items from the vitality subscale of the SF-36 and 10 items from the WOMAC-ADL scale. The third scale (Well-being) contained the remaining four selected items. Two additional scales (Ready, Leave) were also created, to assess the patient's readiness to resume activities and leave the hospital (Table 1). Because of a lack of variability (i.e., ceiling effect) in responses to subjective questions posed by caregivers, the prototype caregiver questionnaire was based primarily on objective performance tests of physical strength and energy level. The functional tests consisted of a pulmonary function test, a timed distance-walked test, a handgrip muscle strength test, and a corresponding HCT level assessment. Together these scales constituted the prototype instrument (Version 3.0).

Table

TABLE 1Items included in the vigor assessment Instrument (Version 3.0)

TABLE 1

Items included in the vigor assessment Instrument (Version 3.0)

Statistical Methods. The reliability and validity of the instruments were assessed using standard psychometric methods,14,15 including exploratory factor analysis, internal consistency analysis, test-retest reliability analysis, and validity coefficients. Face validity was assumed following item selection by the panel and discussion by a patient focus group. Content validity was assessed by examining Pearson's correlations between new and established scales and between the subjective scales and objective measures of vigor. Sample size was established using techniques described by Cohen.16

RESULTS

Patients. The validation population consisted of 65 patients undergoing primary unilateral total joint replacement at one of two participating surgical centers specializing in total joint arthroplasty. Table 2 describes the demographic and baseline clinical characteristics of the patient population for this study. The age distribution was typical for this elective orthopedic surgery population. Records from five patients had missing demographic information; four records did not list a date of birth, thus precluding a calculation of age for those patients. The majority of patients had at least a high school education and was married. Surgery types were evenly distributed.

Instrument Reliability. The novel Well-being scale performed as well as the established modified SF-36 and WOMAC scales in a preoperative comparison of performance and reliability. All these scales measured highly for internal consistency and testretest reliability (Table 3). Missing data were only approximately 10% for each scale, and no pattern to the missing data was observed. These scales also performed well and were internally consistent when administered postoperatively. The Ready and Leave scales, which were only administered postoperatively, were both observed to be internally consistent.

Validity. The results obtained with the Well-being, vitality subscale of SF-36, and WOMAC-ADL scales correlated well with one another and are shown in Table 4. Likewise, a strong correlation between the subjective measures and some of the objective functional tests was also observed. The correlation was strongest between the postoperative questionnaires and the objective functional tests (Table 5). The Well-being and Ready scores correlated well with pulmonary function (P < .05), distance walked (P < .05), and muscle strength (P < .01). The strongest correlation was between three subscales (Well-being scale, vitality subscale of SF-36, Ready scale) and the muscle strength test administered postoperatively (r = 0.4 to 0.54). The novel Ready scale, which assesses the patient's readiness to resume activities of daily living, demonstrated the highest correlation with the objective functional tests, including HCT (P < .01). Furthermore, postoperative HCT correlated with muscle strength (r = 0.4; data not shown). In contrast, the WOMAC scale correlated poorly with preoperative and postoperative objective functional tests. Overall, these data demonstrated a high level of correlation between the subjective Ready scale and the objective functional and laboratory measures of vigor.

Table

TABLE 2Validation population demographic and baseline clinical characteristics (N = 65)*

TABLE 2

Validation population demographic and baseline clinical characteristics (N = 65)*

Table

TABLE 3Subjective scale performance, consistency, and reliability

TABLE 3

Subjective scale performance, consistency, and reliability

Development of the Final Instrument. Based on this initial analysis, a subgroup of the panel developed Version 4.2 (Fig I). The panel subgroup simplified the instrument to a minimal core set of questions and functional tests based on the analysis of the items in the prototype instrument. Given that the vitality subscale of the SF-36 performed similar to the Well-being items, it was eliminated from the final version in favor of the Well-being scale. In addition, in an attempt to develop a more concise instrument, the WOMAC-ADL was reduced to 5 items, which performed as well as the full 10 items included in the prototype instrument. Moreover, the Ready scale, which correlated most strongly with the objective measures, was incorporated into the final version. Finally, many subjective questions were removed from the final version because of a basal or ceiling effect. The resultant patient questionnaires consist of 12 preoperative and 14 postoperative questions. The patient can complete each questionnaire within approximately 5 minutes. The caregiver questionnaire was streamlined to include the results of two objective functional tests: muscle strength, and HCT. While the postoperative assessment was performed 4 days after surgery or at discharge, postoperative HCT was also measured before this date. The optimal timing and frequency of usage for Version 4.2 is being addressed in a prospective clinical trial. Proposed dates for data collection include postoperative day 2, postoperative days 4 to 5, and postoperative weeks 2 to 3.

DISCUSSION

Although several reliable instruments are used to measure long-term surgical outcomes, an extensive search of the English language literature has failed to reveal the existence of an instrument to assess early postoperative vigor. The utility of a reliable short-term outcome instrument would focus on the optimization of patient rehabilitation and discharge planning. Therefore, a multidisciplinary panel developed a novel instrument for subjective and objective measurement of short-term patient recuperative power (i.e., vigor). The instrument also was developed to be convenient and easy to use by both patients and caregivers.

Improving early postoperative vigor may have important implications in facilitating recovery, shortening the length of hospitalization, and improving short-term and, potentially, longterm physical function, all of which can have a substantial impact on patients' emotional and psychosocial well-being. Munin et al have prospectively demonstrated the effect of early rehabilitation on length and cost of hospitalization, as well as the attainment of short-term functional recovery as assessed by improved functional independence measures.' The utility of a reliable instrument to assess early postoperative vigor could help optimize surgical outcomes and allocation of healthcare resources through better patient rehabilitation and discharge planning. Further, interventions aimed at improving early postoperative rehabilitation can be more readily evaluated. Perioperative blood management interventions, such as blood transfusion, may be able to be prioritized based on the assessment of early postoperative vigor.

In the present study, the subjective scales of patient outcome, including the Well-being scale, the vitality subscale of SF-36, and the Ready scale, appear to accurately measure patients' postoperative energy levels and physical strength. When these scales are combined with simple functional tests (i.e., muscle strength, HCT level), they can serve as a meaningful proxy for patients' recuperative power within days after the completion of surgery. Among the objective measures, a statistically significant correlation between muscle strength and HCT was observed, suggesting that these measures may be valuable surrogates of vigor. Fortunately, these parameters are easily measured and are already incorporated into clinical practice. In addition, the most powerful correlation observed was between the Ready to resume scale and objective measurements of HCT and muscle strength.

Fig 1(A): Vigor assessment instrument (Version 4.2). Preoperative patient questionnaire and evaluation.

Fig 1(A): Vigor assessment instrument (Version 4.2). Preoperative patient questionnaire and evaluation.

Fig 1 (B): Vigor assessment instrument (Version 4.2). Preoperative caregiver questionnaire and evaluation.

Fig 1 (B): Vigor assessment instrument (Version 4.2). Preoperative caregiver questionnaire and evaluation.

Fig 1 (C): Vigor assessment instrument (Version 4.2). Postoperative patient questionnaire and evaluation.

Fig 1 (C): Vigor assessment instrument (Version 4.2). Postoperative patient questionnaire and evaluation.

Fig 1 (D): Vigor assessment instrument (Version 4.2). Postoperative caregiver questionnaire and evaluation.

Fig 1 (D): Vigor assessment instrument (Version 4.2). Postoperative caregiver questionnaire and evaluation.

In contrast, the distance walked and pulmonary objective measures of patient function were removed from the final version of the instrument because they did not correlate as well with the subjective measures of patient function. In addition, muscle strength (dynamometer) and HCT are more easily assessed compared with timed di s tance- walked and pulmonary function tests. Further, both preoperative and postoperative objective functional tests correlated poorly with the WOMAC subjective scale, suggesting that this subjective instrument is an insufficient measure of early postoperative vigor. This finding was expected given that the WOMAC is specific for long-term outcome in orthopedic surgery patients.

In summary, a concise instrument has been developed to assess postoperative vigor in the total joint arthroplasty setting. Although preliminary, the initial psychometric validation analysis of this instrument has suggested that subjective patient selfassessment of readiness to resume activities of daily living correlates highly with muscle strength and laboratory measures of vigor in the postoperative setting. Although these observations are interesting, they have yet to be tested in a randomized controlled trial. Extensive clinical testing of the current version may permit further refinement and/or improvement of the instrument and enhance the utility of the measurement. The clinical utility of this instrument and the optimal timing for data collection are currently under investigation in a prospective clinical study.

Table

TABLE 4Correlations among subjective scale performance (n = 58)

TABLE 4

Correlations among subjective scale performance (n = 58)

Table

TABLE 5Correlations among subjective scales and caregiver objective measures: Preoperative and postoperative assessment (n = 32)

TABLE 5

Correlations among subjective scales and caregiver objective measures: Preoperative and postoperative assessment (n = 32)

A variety of important questions remain to be addressed. For example, does postoperative vigor affect the patient's ability to participate in rehabilitation or length of hospital stay? What impact does the management of pre- and postoperative HCT have on postoperative vigor and outcome? Further, will the vigor instrument permit clinicians and administrators to make better decisions regarding when a patient should begin rehabilitation or when a patient should be discharged, rather than base these important decisions on reimbursement or payer issues?

REFERENCES

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3. Bellamy N, Buchanan WW, Goldsmith CH. Campbell J. Stitt LW, Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol. 1988; 15:1833-1840.

4. Gilson BS. Gilson JS, Bergner M, et al. The sickness impact profile. Development of an outcome measure of health care. Am J Public Health. 1975; 65: 1304-1810.

5. Martin DP, Engelberg R, Agel J, Swiontkowski MF. Comparison of the Musculoskeletal Function Assessment questionnaire with the Short Form-36. the Western Ontario and McMaster Universities Osteoarthritis Index, and the Sickness Impact Profile health-status measures. J Bone Joint Surg Am. 1997;79:1323-1335.

6. Shields RK, Enloe LJ. Evans RE. Smith KB, SteckeJ SD. Reliability, validity, and responsiveness of functional tests in patients with total joint replacement. Phvs Then 199S; 75:169-176.

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TABLE 1

Items included in the vigor assessment Instrument (Version 3.0)

TABLE 2

Validation population demographic and baseline clinical characteristics (N = 65)*

TABLE 3

Subjective scale performance, consistency, and reliability

TABLE 4

Correlations among subjective scale performance (n = 58)

TABLE 5

Correlations among subjective scales and caregiver objective measures: Preoperative and postoperative assessment (n = 32)

10.3928/0147-7447-19990102-04

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