| Requirement | Constraint | Verification | Validation |
| 1. The device must allow adjustment of plantarflexion and dorsiflexion to match the patient’s current phase of rehabilitation. | – The device must be easy/intuitive to adjust ROM settings. – The device must minimize the risk of tissue damage, falls, or excessive fatigue. – The device must minimize the risk of reinjury. | – Bench test ROM adjustment mechanism for repeatability and shifting under load. | – Clinicians and test users evaluate ease of adjustment during simulated rehabilitation sessions. |
| 2. The device must allow adjustment of abduction and adduction to match the patient’s current phase of rehabilitation. | – The device must be easy/intuitive to adjust ROM settings. – The device must minimize the risk of tissue damage, falls, or excessive fatigue. – The device must minimize the risk of reinjury. | – Mechanical inspection of ab/adduction mechanism. – Bench test ROM adjustment mechanism for repeatability and shifting under load. | – Clinicians and test users evaluate ease of adjustment during simulated rehabilitation sessions. |
| 3. The device must allow adjustment of inversion and eversion to match the patient’s current phase of rehabilitation. | – The device must be easy/intuitive to adjust ROM settings. – The device must minimize the risk of tissue damage, falls, or excessive fatigue. – The device must minimize the risk of reinjury. | – Mechanical inspection of in/eversion mechanism. – Bench test ROM adjustment mechanism for repeatability and shifting under load. | – Clinicians and test users evaluate ease of adjustment during simulated rehabilitation sessions. |
| 4. The device must actively assist the ankle range of motion during the active recovery phase. | – Active actuator must provide smooth motion. – Assistive torque must be adjustable. – Operation must comply with medical device electrical safety standards. | – Actuator torque and speed curve testing. – Electrical safety testing (current leakage, shutoff performance). | – Clinicians evaluate smoothness and therapeutic appropriateness during mock therapy. – Patient feedback on comfort and natural motion. |
| 5. The device must tolerate loads without loss of structural integrity. | – The brace must be durable enough to withstand daily long-term use. | – Static and fatigue load testing. – Material inspection and FEA correlation. | – Trial walking/ROM exercises by users to confirm real-world durability. |
| 6. The device must be lightweight. | – The brace must be designed with inclusivity of a wide range of age groups and mobility levels. – The device must minimize the risk of tissue damage, falls, or excessive fatigue. – The device must minimize the risk of reinjury. | – Mass measurement and pressure mapping. | – User wear test for 30 minutes to assess fatigue. – Clinician evaluation for suitability across mobility levels. |
| 7. The device must be comfortable. | – The brace must be designed with inclusivity of a wide range of age groups and mobility levels. | – Material certification review. – Pressure and contact-point inspection. – Repeated-donning comfort analysis. | – Patient comfort surveys after extended wear. – Clinician review for irritation/redness. |
| 8. The device must allow fast switching between the three rehabilitation phase modes. | N/A | – The device’s mode control will be confirmed by testing the success rate of the mode switching. | – Human testing will be used to confirm that someone outside of device development can successfully switch the mode of the device. |
| 9. The device must constrain the range of motion of the ankle to match the patient’s current phase of rehabilitation. | N/A | – The device’s accuracy will be confirmed by comparing range of motion readings to a fixture with set angles. | – Human testing will be used in conjunction with a set test fixture to measure the ankle range of motion in all three planes during each phase |
| 10. The device must provide a controllable active element capable of assisting the patient through a prescribed range of motion during the sub-acute phase. | N/A | – The device’s active component control will be confirmed by comparing range of motion readings to a fixture with set angles. | – Human testing will be used to ensure that the device provides ample actuation torque to provide effective assistance through either exercise or weight |
| 11. The device must allow clinicians to set a custom range of motion boundary for each plane of motion within the sub-acute phase. | N/A | – The device’s active component control will be confirmed by comparing range of motion readings to a fixture with set angles. | – Human testing will be used to test the device range of motion based on the prescribed set point at various points in the range (min, max, nominal) |
| 12. The device must include a fail-safe that prevents motion beyond clinician-set limits. | N/A | – The device’s fail-safe mechanism will be confirmed by attempting to rotate the device beyond the constrained range of motion and measuring further motion beyond that range. | – Human testing will be used in conjunction of a set fixture to measure the range of motion in the ankle relative to the prescribed range set by the hard stop. |
| 13. The device must include an emergency shut-off mechanism that rapidly stops all powered motion. | N/A | – The function of the shutoff control will be confirmed deactivation of all active components of the device upon emergency shutoff activation | – Human testing will be used to ensure that the device shutoff is easily reachable by the wearer and intuitively designed for use by measuring time between patient stimulus and device shutoff. |