Eliminating pain and restoring physical activity are the main goals of total hip arthroplasty (THA). Despite the high relevance of activity as a rehabilitation goal of and criterion for discharge, in-hospital activity between operation and discharge has hardly been investigated in orthopaedic patients.

Therefore, the aim of this study was to a) measure for reference the level of in-hospital physical activity in patient undergoing a current rapid discharge protocol, b) compare these values to a conventional discharge protocol and c) test correlations with pre-operative activities and self-reported outcomes for possible predictors for rapid recovery and discharge.

Patients (n=19, M:F: 5:14, age 65 ±5.7 years) with osteoarthritis treated with an elective primary THA underwent a rapid recovery protocol with discharge on day 3 after surgery (day 0). Physical activity was measured using a 3D accelerometer (64×25×13mm, 18g) worn on laterally on the unaffected upper leg. The signal was analysed using self-developed, validated algorithms (Matlab) calculating: Time on Feet (ToF), steps, sit-stand-transfers (SST), mean cadence (steps/min), walking bouts, longest walk (steps).

For the in-hospital period (am: ca. 8–13h; pm: ca. 13–20h) activity was calculated for day 1 (D1) and 2 (D2). Pre-operative activity at home was reported as the daily averages of a 4-day period. Patient self-report included the HOOS, SQUASH (activity) and Forgotten Joint Score (FJS) questionnaires.

In-hospital activity of this protocol was compared to previously collected data of an older (2011), standard conventional discharge protocol (day 4/5, n=40, age 71 ±7 years, M:F 16:24).

All activity parameters increased continuously between in-hospital days and subsequent am and pm periods. E.g. Time-on-feet increased most steeply and tripled from 21.6 ±14.4min at D1am to 62.6 ±33.4min at D2pm. Mean Steps increased almost as steep from 252 to 655 respectively. SST doubled from 4.9 to 10.5. All these values were sign. higher (+63 to 649%) than the conventional protocol data.

Cadence as a qualitative measure only increased slowly (+22%) (34.8 to 42.3steps/min) equalling conventional protocol values. The longest walking bout did not increase during the in-hospital period. Gender, age and BMI had no influence on in-hospital activity.

High pre-op activity (ToF, steps) was a predictor for high in-hospital activity for steps and SST's at D2pm (R=0.508 to R=0.723). Pre-op self-report was no predictor for any activity parameter.

In-hospital recovery of activity is steep following a cascade of easy (ToF) to demanding (SST) tasks to quality (cadence). High standard deviations show that recovering activity is highly individual possibly demanding personalised support or goals (feedback).

Quantitative parameters were all higher in the rapid versus the conventional discharge protocol indicating that fast activation is possible and safe. Equal cadence for both protocols shows that functional capacity cannot be easily accelerated.

Pre-op activity is only a weak predictor of in-hospital recovery, indicating that surgical trauma affects patients similarly, but subjects may be identified for personalized physiotherapy or faster discharge.

Reference values and correlations from this study can be used to optimize or shorten in-hospital rehabilitation via personalization, pre-hab, fast-track surgery or biofeedback.

Introduction: Physical activity is a major outcome in total hip arthroplasty (THA) and discharge criterion. Increasing immediate post-op activity may accelerate discharge, enable fast track surgery and improve general rehabilitation. Preliminary evidence (O'Halloran P.D. et al. 2015) shows that feedback via motivational interviewing can result in clinically meaningful improvements of physical activity. It was the aim of this study to use wearable sensor activity monitors to provide and study the effect of biofeedback on THA patients' activity levels. It was hypothesized that biofeedback would increase in-hospital and post-discharge activity versus controls.

Methods: In this pilot study, 18 patients with osteoarthritis receiving elective primary THA followed by a rapid recovery protocol with discharge on day 3 after surgery (day 0) were randomized to the feedback group (n=9, M/F: 4:5, age 63.3 ± 5.9 years, BMI 26.9 ± 5.1) or a non-feedback control group (n=9, M/F: 0:9, age 66.9 ± 5.1 years, BMI 27.1 ± 4.0). Physical activity was measured using a wearable sensor and parameters (Time-on-Feet (ToF), steps, sit-stand-transfers (SST), mean cadence (steps/min)) were calculated using a previously validated algorithms (Matlab). For the in-hospital period data was calculated twice daily (am, ca. 8–13:00h and pm, ca. 13–20:00h) of day 1 (D1) and 2 (D2). The feedback group had parameters reported back twice (morning, lunch) using bar charts comparing visually and numerically their values (without motivational instructions) to a previously measured reference group (n=40, age 71 ±7 years, M:F 16:24) of a conventional discharge protocol (day 4/5). Activity measures continued from discharge (D3) until day 5 (D5) at home.

Results: Randomization resulted in matched groups regarding age and BMI, but not gender. The first post-op activity assessment (D1am) was identical between groups. Also thereafter similar values with no significant differences in any parameter were seen, e.g. the time-on-feet at D2PM was 59.2 ±31.7min (feedback) versus 62.9 ±39.2min (controls). Also on the day of discharge and beyond, no effect from the in-hospital feedback was measured. For both groups the course of activity recovery showed a distinct drop on day 4 following a highly active day of discharge (D3). On day 5, activity levels only recovered partially. For both groups, all quantitative activity parameters were significantly higher than the reference values used for feedback. Only cadence as a qualitative measure was the same like reference values.

Discussion: Biofeedback using activity values from a body-worn monitor did not increase in-hospital or immediate post-op home activity levels compared to a control group when using the investigated feedback protocol. In general, while the day of discharge steeply boosts patient activity, the day after at home results in an activity drop to near in-patient levels before discharge. In a fast track surgery protocol, it may be of value to avoid this drop via patient education or home physiotherapy. Biofeedback using activity monitors to increase immediate post-op activity for fast track surgery or improved recovery may only be effective when feedback goals are set higher, are personalised or have additional motivational context.