Study Design
Using a quasi-experimental study design, we compared a 6-week post-operative augmented rehabilitation to usual care among people who were 60 years or younger and undergoing elective THA. Participants were recruited from a central intake centre, Edmonton Hip and Knee Clinic which serves Edmonton Alberta, Canada, and surrounding regions. With over 35 surgeons and multi-disciplinary teams, approximately 3000 joint replacements are performed annually. Most, if not all, surgeons were high volume (> 50 THA per year) who routinely used the Hardinge approach. All patients followed a provincial standardized clinical pathway for acute-care management with 3 to 4 days of hospital stay. The home exercise program which is provided as usual care included range of motion activities, isometric hip strengthening exercises, and walking with appropriate assistive walking devices.
Eligible participants were a) 60 years of age or younger, b) received a unilateral THA, c) 6-12 weeks follow-up after receiving an elective THA, and d) able to communicate in English. The exclusion criteria consisted of a) bilateral THA, b) hemiarthroplasties, c) emergency THA, d) primary diagnosis of developmental hip dysplasia, and e) patients who have a systemic illness that limited their ability to participate (e.g., rheumatoid arthritis, cardiac involvement that precluded exercise).
Upon providing written consent, patients were assessed at their 6-week post-operative visit with the surgeon (baseline assessment) and then 6 weeks later when the interventional group had completed the rehabilitation program (Follow-up assessment) (FIGURE 1). The assessment consisted of socio-demographic (age, sex, education, marital status), medical/surgical information, physical activity (SenseWear Pro Armband (SWA) (22-25), pain and function (Hip Osteoarthritis Outcome Score, HOOS (26)) and participants’ satisfaction with THA. Using a standardized form, clinical charts were reviewed for medical and surgical information (chronic conditions, height/weight, surgical approach, complications). This study was approved by the University of Alberta’s Health Ethics Board. (PRO00051978). All procedures were performed in accordance with University of Alberta’s Health Ethics Board guidelines.
Augmented Rehabilitation Program
The intervention group consisted of participants who were referred to a post-operative augmented 6-week rehabilitation program by their surgeons at the 6-week post-operative routine visit. The outpatient rehabilitation program involved 2 hours of structured group exercise classes led by a physiotherapist over 6 weeks. Participants were required to attend twice a week for 12 sessions. Each session included 1 hour of land-based exercises and 1 hour of water-based exercises.
Usual Post-operative Care for Control Group
At the 6-week routine post-operative surgical visit, age (within a 5-year age difference) and sex-matched participants were recruited for the control group. Participants in the control group continued with usual care after their six-week surgeon’s visit, which included a standardized home exercise.
Outcomes Measures
Physical Activity (PA): A direct measure of daily PA was estimated from the daily energy expenditure calculated from the SenseWear Pro ArmbandTM (SWA; Body Media, Inc, Pittsburgh, PA). The SWA is a tri-axial accelerometer that integrates motion sensor data with the data from three sensors (heat flux, galvanic skin response, and skin temperature) and combines these data with demographic characteristics (gender, height, weight, handiness, and smoking status) to estimate energy expenditure using algorithms provided by the manufacturer (22-25). The SWA has been shown to have good validity under both laboratory (22, 27, 28) and free-living conditions (29). There is an error rate of 8% with an ICC of 0.8 for energy expenditure determined from the SWA and doubly labeled water (30).
The SWA was worn on the arm over the triceps for four consecutive days (31). Participants were instructed to remove the device when bathing, showering, or swimming. Valid days were defined as those days when the participant wore the SWA > 10 hours during the waking time (32, 33). Once the SWA was returned to the lab, data were downloaded to generate the total time the device was worn, steps/minute, and minute by minute energy expenditure, and metabolic equivalent task (MET) intensity levels. One MET is the energy cost of resting quietly, often defined in terms of oxygen uptake as 3.5 mL/kg/min (34, 35). Minute by minute data was averaged over all valid days to provide information on the number of steps/day, energy expenditure, stationary time, and time spent in different activity intensities (i.e., light PA, moderate-vigorous PA [MVPA]).
Stationary time was defined as waking time with an energy expenditure ≤ 1.5 METs (36-38). Light Physical Activity was defined as activities that required an energy expenditure of 1.6-2.9 METs (e.g., activities of daily living [ADL]) (37). MVPA included activities with an energy expenditure ≥ 3.0 METs. For time spent in MVPA, recommendations suggested PA bouts of > 10 minutes (39, 40). Data were inspected to determine both the total minutes of MVPA (MVPAall) and continuous MVPA occurring in >10 minutes bouts (i.e., MVPA10+). To count as an MVPA10+ the bout had to start with a minute above the MVPA cut-point (> 3 METs) and last for > 10 consecutive minutes with allowance for a maximum of two observations falling below the cut-point during the period (i.e., 8/10 minutes) (41). Furthermore, we calculated the amount of time and energy spent in MVPA10+. The amount of energy spent on MVPAall was also presented as PA energy expenditure.
Hip Osteoarthritis Outcome Score (HOOS): The HOOS questionnaire is a self-report measure of joint-specific pain, stiffness, sports activity, and health-related quality of life. It consists of 5 subscales: Pain (10 items), Symptoms (2 items), Function in activities of daily living (ADL) (17 items), Function in sport and recreation (Sport/Rec) (4 items), and hip-related Quality of life (QoL) (4 items). Each subscale score is calculated independently by summing all items in each subscale and then normalizing the total into the range of 0 to 100 (26). The higher score reflects better condition for the hip. The validity, reliability, and responsiveness of HOOS had been evaluated in different studies (26, 42, 43). HOOS contains adequate measurement qualities to evaluate patients with hip osteoarthritis or THA (43) and patients ≤ 66 years of age reported higher responsiveness in all five subscales compared to patients > 66 years of age (26).
Participants’ satisfaction with THA: Participants’ satisfaction was assessed using a 5-item questionnaire asking if THA: could be recommended to their family, was worthwhile, was helpful, led to a negative outcome, or was dissatisfying (44). All items were rated on a 5-point likert scale ranging from strongly agree to strongly disagree
Data analysis
Summary descriptives were reported as mean and standard deviation (SD) for continuous variables, numbers, and percentages for categorical variables. The between-group differences at baseline, follow-u,p, and the absolute change (follow-up - baseline) were evaluated by using two independent samples t-tests. To evaluate the within-group differences, paired-samples t-tests were used. Mann-Whitney U nonparametric test was used to compare the groups if data is not normally distributed. To explore whether the physical activity as measured by the SWA (step counts and MVPA bouts) were correlated with the self-reported HOOS subscale scores, Pearson correlation coefficients were examined and categorized as weak (0.10 to 0.39), moderate (0.40 to 0.69), strong (0.70 to 0.89) and very strong (0.90 to 1.00). (45). Statistical analyses were conducted using SPSS version 24 (SPSS, Inc. Chicago, IL, USA).