Abstract
Introduction
The goal of total hip arthroplasty (THA) is to reduce pain, restore function but also activity levels for general health benefits or social participation. Thus evaluating THA patient activity can be important for diagnosis, indication, outcome assessment or biofeedback.
Methods
Physical activity (PA) of n=100 primary THA patients (age at surgery 63 ±8yrs; 49M/51F; 170 ±8cm, 79.8 ±14.0kg) was measured at 8 ±3yrs follow-up. A small 3D accelerometer was worn for 4 successive days during waking hours at the non-affected lateral upper leg. Data was analyzed using validated algorithms (Matlab) producing quantitative (e.g. #steps, #transfers, #walking bouts) and qualitative (e.g. cadence, temporal distribution of events) activity parameters. An age matched healthy control group (n=40, 69 ±8yrs, 22M/18F) served as reference.
Results
Daily steps were only 13% lower (n.s) for patients (avg. ±SD: 5989 ±3127) than controls (6890 ±2803). However, the Nr. of walking bouts (187 ±85 vs 223 ±78, −16%) and sit-stand transfers (35 ±14 vs 48 ±15, −27%) were sign. less in patients (p<0.05, Mann-Whitney).
Patients showed equal amounts of walking bouts in medium duration (30–60s, 1–5min) but sign. less (−25%) short (<10s, 10–30s) and less (−43%) long events (>5min). This corresponds with sign. less (−32%) short sitting periods (>10min) in patients. Also cadence was sign. lower in patients (93.8 ±11.7 vs 98.9 ±7.3 steps/min).
Conclusions
PA varies widely in patients with a substantial proportion (35%) being more active than average controls. Thus, THA must not per se reduce or limit PA.
Only 17% of controls and 11% of patients reached the WHO target (10,000 steps/day) suggesting that the THA related drop in activity may inflate the risks for cardiovascular, metabolic or mental disease associated with low activity.
Patients avoided short and long activities, both associated with effort (transfers, fatigue) and walked more slowly. Targeted interventions may address this behaviour. Objective clinical outcome assessment must focus on these parameters and not, as commercial fitness trackers may imply, total step counts alone.
