Therapeutic exoskeletons differ from rehab robots in that the patient wears the device. The mass distribution, the hip-knee-ankle joint coupling, and the donning/doffing workflow all become first-class safety concerns. This chapter walks the regulatory pathway under FDA 21 CFR 890.3480 (powered exoskeleton), the EU MDR class-IIa+ pathway, and the operating envelope a clinical site needs to commission a unit.
FDA classifies powered exoskeletons under product code PHL with prescription-use restriction. The 510(k) pathway accepts substantial-equivalence claims against predicate devices (ReWalk Personal, Ekso GT, Indego, Phoenix, Atalante). Special-controls guidance covers labelling for environment-of-use, patient-weight + height envelope, training requirements for the supervising clinician, and battery + actuator failure-mode disclosures. Devices outside the predicate envelope follow De Novo or PMA per Class III.
Joint torque per IEC 80601-2-78 + ISO 13482 (personal-care robot) sets the actuator sizing. Series-elastic actuators (SEA) decouple torque control from gear-train inertia and improve back-drivability for patient-driven motion. Battery envelope follows IEC 62133-2 + UL 1973 for the secondary lithium chemistry; thermal runaway containment per UN 38.3 is mandatory for transport. Body-weight support is graded per protocol — full unloading early, proportional later.
The donning workflow is part of the device's risk file. Time-to-don envelope, single-clinician vs two-clinician operation, and patient-position requirements (seated vs supine vs standing-frame) all flow into the IFU. Doffing in an emergency is qualified separately — every device must support clinician-initiated rapid release without battery support. ISO 13850 emergency-stop requirements apply to the actuator chain; the harness release follows the manufacturer's qualified mechanical procedure.
Step-symmetry, step-length, swing-time, and double-support time form the canonical gait dataset. The exoskeleton's onboard kinematics feed both the real-time controller and the post-session analytics surface (per Phase 2 of WIA-MED-026). Outcome measures: 6-Minute Walk Test (6MWT per Enright + Sherrill 1998), 10-Meter Walk Test, Berg Balance Scale (Berg 1989), and the Spinal Cord Independence Measure (SCIM-III) for SCI populations.
Indications follow the per-device IFU: typically chronic SCI with intact upper-extremity strength, post-stroke gait deficits, MS, traumatic brain injury. Contraindications include severe spasticity uncontrolled by medication, lower-extremity contractures beyond device range, unhealed pelvic or lower-extremity fractures, severe cardiopulmonary disease, and weight outside the device envelope. Pre-screening occurs against the device's qualification criteria per the operator's clinical-site policy.