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This chapter provides two case reports that illustrate the concepts introduced in this text. They are presented in a format that mirrors decisions encouraged in clinical practice. The first case involves a 63-year-old woman post total knee arthroplasty, and the second case considers a 20-month-old infant with cerebral palsy. We encourage you to read both cases, as they demonstrate somewhat different concepts.
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Mrs. Janice Smith, a 63-Year-Old Post Total Knee Replacement
In this case we apply concepts introduced in Chapters 4 through 8 and 10.
Vignette You are a physical therapist who has recently started work in a clinic that specializes in the rehabilitation of patients pre and post total joint arthroplasty. Mrs. Smith is the first patient you have seen in the clinic. She is an active woman with severe osteoarthritis of the right knee. Preoperatively, you assessed her 6-minute walk distance (6MWT) and obtained a value of 412 m. Mrs. Smith is now 2 weeks post total knee arthroplasty and her 6MWT distance is 232 m.
Questions 1. How confident can you be about Mrs. Smith's 6MWT distance of 232 m?
2. What is the interpretation of a 6MWT distance of 232 m?
3. How much change in Mrs. Smith's 6MWT distance is necessary to be reasonably certain that she has improved?
4a. When would the typical person with Mrs. Smith's 6MWT distance of approximately 232 m at 2 weeks post-arthroplasty be expected to improve by a detectable amount? Write a measurable goal.
4b. Suppose at 8 weeks post-arthroplasty Mrs. Smith had a 6MWT distance of 391 m. When would the typical person's 6MWT distance at 8 weeks post-arthroplasty be expected to improve by a detectable amount? Write a measurable goal.
5. What is Mrs. Smith's expected target 6-minute walk distance? How does distance compare to what the expected value would be for 63-year-old women in the population?
Approach to Questions and Responses 1. How confident can you be about Mrs. Smith's 6MWT distance of 232 m?
To answer this question, we applied information reported in Chapters 4 and 10. The first step was to find studies reporting the reliability of the 6MWT for a similar patient group. Accordingly, we conducted a PubMed literature search using the following search themes: “measure AND measurement properties AND condition” format. We applied the following search term: (“6-min* walk” OR six-minute OR 6MW*) AND (reliab* OR SEM OR MDC OR test-retest) AND knee AND (osteoarthritis OR arthroplasty OR replacement).
Three articles were identified and we found the following one to be most relevant: Kennedy DM, Stratford PW, Wessel J, Gollish JD, Penney D. Assessing stability and change of four performance measures: A longitudinal study evaluating outcome following total hip and knee arthroplasty. BMC Musculoskelet Disord 2005;6:3. In this study Kennedy et al reported the relative reliability of the 6MWT to be 0.94 in a sample of patients with osteoarthritis ...