- Background and Rationale Musculoskeletal disorders (MSDs) are the leading cause of occupational illness in France, accounting for 88% of recognized occupational diseases in 2019 (French Social Security data). In the healthcare sector, MSDs affect the trunk (particularly the lumbar and dorsal spine) and upper limbs of nursing staff disproportionately. Within nursing homes (EHPADs), 94% of recognized occupational diseases are MSD-related. Among LNA Santé's internal data (2023), 27.8% of all workplace accidents (WPAs) are linked to resident handling; 54% of WPAs affect care staff, primarily nursing assistants (aides-soignants, 31%), registered nurses (18%), and personal care assistants (auxiliaires de vie, 12%). The most physically demanding tasks identified include bed baths and diaper changes performed with residents in decubitus (lying) position.
- Rationale for the Intervention The HAPO exoskeleton is a passive back-assist wearable device developed by Ergo Santé (France) designed to support the upper body during forward-bending tasks. Prior phases of the LNA Santé exoskeleton research program (EXO 1, Versions 1-4) demonstrated increasing levels of satisfaction and acceptance, culminating in a 100% satisfaction rate at Version 4 among LNA Santé care staff. These early-phase studies identified initial discomfort related to device sizing and fit for female morphology, which was progressively addressed. Following these positive findings, EXO 2 was designed to assess, over a longer period and in a larger and more diverse cohort, the real-world impact of HAPO V4 on occupational fatigue, pain, and working conditions, including exploration of primary prevention (asymptomatic staff) and secondary prevention (staff with prior upper body pain history).
- Study Design EXO 2 is a prospective, multicenter, single-group, longitudinal observational study with a within-participant before-after design. No control group was included. All eligible volunteer care staff from five LNA Santé nursing home sites were enrolled. Each participant underwent a 2-week baseline observation period (without exoskeleton) followed by an 11-week exoskeleton use period. Data were collected at weekly intervals using standardized tools.
Regulatory classification: This study is classified as Research Not Involving the Human Person (RNIPH) under Article L1121-1 of the French Public Health Code, in the field of human and social sciences applied to occupational health. Data collection and processing comply with CNIL Reference Methodology MR-004, ensuring pseudonymization and confidentiality without requiring review by a Committee for the Protection of Persons (CPP).
- Intervention Description HAPO Exoskeleton Version 4 (Passive Back-Assist Wearable Device) The HAPO V4 exoskeleton is a passive (non-motorized), CE-marked wearable device worn around the torso. It is designed to provide mechanical support to the dorsal and lumbar spine and upper body during forward-bending tasks, reducing muscular effort during resident handling in decubitus position (bed baths, diaper changes). The device is adjusted individually to each participant's morphology before the intervention phase. Care staff wear the exoskeleton daily during all bed baths and resident changes in lying position throughout their working shifts (day and night), for 11 consecutive weeks (Day 15 to Day 91). The exoskeleton does not replace existing patient-handling equipment (hoists, slide sheets, etc.) but supplements them. Usage is voluntary on a daily basis; reasons for non-use are recorded.
- Standard of Care / Work Context All participants continued their usual care routines. Standard patient-handling equipment available in each unit (rails, hoists, patient lifters - lève-malade and verticalisateur) was documented. Ongoing risk prevention training (PRAP - Prevention of Risks Related to Physical Activity) was provided to all site coordinators. No other ergonomic intervention was introduced during the study period.
- Visit Schedule and Procedures Visit Timing Assessments Pre-inclusion (VS) Day -7 Study presentation meeting at each site; information letter; 7-day reflection period Inclusion (V0) Day 0 Written consent; demographics, clinical data, occupational data; prior upper body pain history (past 12 months); individual exoskeleton fitting preparation Baseline V1, V2 Day 7 and Day 14 Borg scale (upper body effort); number of handling tasks; daily pain logbook (VAS) - no exoskeleton Intervention V3-V12 Day 15 to Day 84 (every 7 days) Borg scale (weekly); VAS pain (daily logbook); exoskeleton use rate and reasons for non-use (daily logbook); satisfaction (weekly); number of handling tasks (weekly) End-of-study (Vf) Day 91 Borg scale; VAS pain; exoskeleton use; satisfaction; number of handling tasks; participant verbatim Absenteeism & WPA follow-up 3 periods vs Months 1-3 M-12 to M-10; M-3 to M-1; M4 to M6 (unit-level data)
- Assessment Tools Borg Scale (CR10 version - Perceived Exertion) The Borg CR10 is a validated ratio scale measuring subjective perceived exertion intensity. In this study, it is applied specifically to upper body effort (neck, shoulders, upper arms, back, hips/waist) experienced during resident handling tasks. Completed weekly by participants. Score ranges from 0 (nothing at all) to 10 (maximal exertion); higher score = greater perceived effort. Assessed at baseline (Day 7 and Day 14) and weekly from Day 15 to Day 91.
Visual Analog Scale for Pain (VAS / EVA - Upper Body) A 10 cm visual analog scale measuring daily upper body pain intensity (neck, shoulders, upper arms, back, hips/waist). Completed daily in the participant logbook. Score ranges from 0 (no pain) to 10 (worst imaginable pain); higher score = greater pain intensity. Assessed daily from Day 0 to Day 91.
Exoskeleton Satisfaction Scale A single-item numeric rating scale measuring participant satisfaction with the HAPO V4 device. Completed weekly. Score ranges from 0 (completely dissatisfied) to 10 (completely satisfied); higher score = greater satisfaction. Assessed weekly from Day 15 to Day 91.
Exoskeleton Use Rate (Logbook) Daily recording in the participant logbook of whether the exoskeleton was worn (full use / partial use / not worn) during all resident handling tasks in decubitus. Reasons for non-use are also recorded. Analyzed as proportion of days with full, partial, or no use over the intervention period.
Number of Resident Handling Tasks (Logbook) Weekly count of the number of bed baths and diaper changes performed by the participant during the follow-up period, used as a proxy for workload. Assessed weekly from Day 7 to Day 91.
Absenteeism Rate and Workplace Accidents Unit-level data on restricted sick leave rates and number of work accidents related to resident handling, collected for three comparable periods: pre-study (M-12 to M-10), immediately before (M-3 to M-1), during (M1 to M3), and after the study. Collected from HR records.
Financial and Operational Investment Data At end of study: cost per unit (rental or purchase), human resources required for implementation, training time dedicated to exoskeleton introduction. Collected from each site coordinator.
- Statistical Analysis Plan Statistical analyses were performed by a contracted biostatistician using R (v4.3.2 or later). No formal sample size calculation was performed given the exploratory nature and the constraint of volunteer availability (estimated 5-8 participants per site, 5 sites = 30-40 participants).
Descriptive statistics: Continuous variables described as mean ± SD or median [IQR] (normality tested by Shapiro-Wilk); qualitative variables as frequencies and percentages. Rates are accompanied by 95% CIs (Clopper-Pearson method).
Primary and secondary inferential analyses (Borg scale and VAS): At key visits, compared to baseline (V1/V2) using paired parametric (paired t-test) or non-parametric (Wilcoxon signed-rank) tests depending on normality of differences. Longitudinal mixed linear models (with participant as random effect) used to evaluate the temporal effect. Satisfaction data and handling counts analyzed by the same approach, with McNemar tests and Poisson regressions if distributions are discrete. Exoskeleton use (refused/partial/total) analyzed by McNemar test and binomial regression (refusal as event). Multivariate risk factor analyses and correlations across continuous outcomes at different visits are also planned.
All tests bilateral, alpha = 5%; all confidence intervals 95%.
- Benefit-Risk Assessment Expected benefits: Reduction in perceived upper body exertion during resident handling tasks; reduction in upper body pain intensity; improvement in working conditions and quality of work life; reduction in workplace accidents and sick leave rates related to resident handling over time.
Identified risks: Physical discomfort during the device adaptation period (estimated first 1-2 months of use); potential redistribution of physical load to previously unloaded muscle groups, which may cause new strain patterns; possible onset of new pain in alternative body regions during the adaptation phase. Participants are informed that withdrawal is voluntary and can occur at any time, without consequence, if discomfort or adverse effects are considered excessive.
- Regulatory and Ethical Framework This study is classified as RNIPH under French law (Article L1121-1 of the French Public Health Code) as a study in human and social sciences applied to occupational health, conducted on a voluntary basis without CPP review. Data collection and processing comply with CNIL Reference Methodology MR-004. Written informed consent was obtained from all participants. Data are pseudonymized; the correspondence list is held exclusively by the site coordinator at each participating establishment. The sponsor (LNA Santé) is the data controller. Results are compiled into an internal report and intended for publication in a peer-reviewed scientific journal. Study documents are archived for 2 years after study closure.
