Most of the patients undergoing TKR are elderly.9
They are likely to have co-morbidities that give them more Siriraj Med J, Volume 66, Number 3, May-June 2014 67
risks to postoperative complications than patients in other
age groups.
10 In contrast, some studies have found that
age has no effect on functional status in patients after
TKR;11 therefore, more studies are needed.
There has been much interest concerning how
patients undergoing TKR have higher BMI than normal.12
BMI is another factor which affects functional status, as
higher BMI has more likelihood for postoperative complications and poorer outcomes of TKR.13 However, in
other studies comparing BMI, it was found that BMI has
no effect on functional status after TKR.14
In Thailand, there are no studies investigating the
relationships among age, BMI, recovery symptoms, and
functional status in TKR patients. The present study aimed
to explore age, BMI, recovery symptoms, and functional
status, and examine their relationships in patients after
TKR at the first follow-up (2 weeks) to better understand
the early recovery phase in TKR patients.
MATERIALS AND METHODS
Participants and sample size
Participants were patients after TKR, recruited
by convenience sampling from a university hospital in
the central region of Thailand between September and
December 2012. Patients who met the following inclusion
criteria were approached: (a) suffering from knee osteoarthritis, (b) undergoing TKR for the first time, (c) having
first follow-up following discharge, (d) being mentally
competent, and (e) being literate in Thai. The exclusion
criteria were (a) having a co-morbidity affecting functioning and mobility and (b) having history of psychoneurological abnormality.
The sample size was calculated using the Table
of Power Analysis of Polit and Beck15, with the level of
confidence (α) of 0.05. The power of test was 0.80, with
the effect size of 0.30. A sample size of 88 was necessary.
Instrument for assessments
Recovery symptoms were measured using the
Recovery Symptoms modified by the researcher from the
Activities of Daily Living Scale of the Knee Outcome
Survey16 and the Symptom Inventory.17 It was a 27-item
checklist with one open-ended questions. Using a scale
from 1 to 7, the subjects were asked to describe the
frequency with which given symptoms occurred during
the previous week. A total score was calculated by summing
the item scores. Higher scores indicated more severe symptoms. To determine the content validity of the instrument
in this study, the instrument was submitted to three
specialists at a university hospital who were experts in
caring for patients after TKR. The reliability in this study
was assessed by using Cronbach’s alpha and was found
to be 0.70.
Functional status was measured by using the
functional dimension of The Modified Thai WOMAC
(Western Ontario and McMaster University Osteoarthritis
Index).18 It is composed of 15 items arranged in a numeric
rating scale with the scores ranging from 0 to 10, to elicit
data regarding functional status of knee joints in different