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The ODFS® Pace XL is intended to provide ankle dorsiflexion in individuals who have a dropped foot as a consequence of upper motor neuron injury. By detecting the swing phase of gait through a foot switch signal, appropriate electrical stimulation of the leg and ankle muscles may improve gait by flexing the foot of persons who have lost or impaired function. There may be additional benefits from FES such as muscle re-education, prevention/retardation of disuse atrophy, increased or maintained range of joint motion and increase in local blood flow.

The ODFS® Pace XL is a medical device and should only be used under medical supervision for the treatment of dropped foot following an upper motor neuron injury.

The ODFS® Pace XL is an external functional neuromuscular stimulator. It consists of a small, body worn, battery powered, single channel stimulator which is triggered by a footswitch worn in the shoe. The footswitch options are:

1. Shoe insole incorporating wireless transceiver which provides wireless triggering
2. 'Out of shoe' wireless transceiver with 'in shoe' heel switch. Provides wireless triggering.
3. Wired 'in shoe' heel switch for where 1 & 2 are not appropriate or to cover an emergency, e.g. loss of battery power in wireless accessory.

The triggering element and detection is the same across all options and option 3 is common to the ODFS® Pace (predicate device).

Electrical pulses are generated by the device in order to stimulate muscle contractions in the lower limb. (Neuromuscular stimulation) Triggering with a footswitch permits the stimulation to be varied according to the gait of the user. Stimulation produces contraction of the appropriate muscles to cause dorsiflexion of the ankle in individuals who have impaired or absent ability to pick up their foot during walking as a result of a neurological injury. This paralysis affecting the foot is commonly known as 'drop foot' or 'dropped foot'.

The electrical stimulation is delivered via self adhesive skin surface electrodes. The electrodes may be flexibly placed according to the optimum response of the patient but typically are located over the common peroneal nerve as it passes near the head of the fibula. The user may be offered the below knee ODFS® Leg Cuff accessory as aid to locating electrodes repeatedly day to day. An additional option is to mount the ODFS® Pace XL upon the ODFS® Leg Cuff.

For individuals presenting with weakness and/or spasticity a muscle stimulation exercise program can be delivered by the ODFS® Pace XL. In this case the footswitch trigger is not used and the ODFS® Pace functions as a powered muscle stimulator. A clinician would determine the need for this application which can be enabled from a setup option in the ODFS® Pace XL. (Default is to have the exercise disabled)

The Odstock Medical Ltd ODFS® Pace XL device is a functional neuromuscular stimulator. The acceptance criteria and the study that proves the device meets the acceptance criteria are described below.

1. Table of acceptance criteria and the reported device performance:

The provided document K171396 is a 510(k) premarket notification of intent to market the ODFS® Pace XL. This submission does not define specific "acceptance criteria" in the sense of predefined numerical targets that the device must achieve in a clinical trial. Instead, the submission demonstrates "substantial equivalence" to legally marketed predicate devices by showing that the ODFS® Pace XL has the same intended use and similar technological characteristics, and that any differences do not raise new questions of safety and effectiveness.

The "performance data" provided focuses on the electrical output specifications of the device and its compliance with recognized standards. The comparison is primarily against the ODFS® Pace (K102115) and ODFS® III v6.2 (K050991) predicate devices.

2. Sample sized used for the test set and the data provenance:

The provided document describes performance testing of the device itself to verify functional and output specifications and compliance with electrical safety standards. It does not describe a clinical study with human subjects (a "test set" in a clinical performance context).

• Test set sample size: N/A (no clinical test set as part of this submission for substantial equivalence)
• Data provenance: The performance testing was conducted by the manufacturer (Odstock Medical Ltd) and a third party for electromagnetic compatibility. The country of origin for the data is the UK. The testing described is prospective (i.e., performed on the ODFS® Pace XL device).

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

N/A - This submission is not based on a clinical study where expert ground truth establishment would be required. The "ground truth" for the device's electrical performance and safety is derived from established engineering principles and international standards.

4. Adjudication method for the test set:

N/A - Not applicable as there was no clinical test set requiring adjudication.

5. If a multi reader multi case (MRMC) comparative effectiveness study was done, if so, what was the effect size of how much human readers improve with AI vs without AI assistance:

N/A - This is not an AI-assisted diagnostic device. No MRMC study was conducted or described.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

N/A - This is a medical device for functional neuromuscular stimulation, not an algorithm. The "standalone" performance relates to the device's adherence to its electrical and functional specifications, which was tested.

7. The type of ground truth used:

The "ground truth" for this submission are the engineering specifications and international standards for electrical medical devices. For example:

• The voltage, current, pulse width, and frequency outputs were measured against the device's designed specifications.
• The patient leakage current limits were measured against the requirements of ISO 60601-1.
• Electromagnetic compatibility was assessed against ISO 60601-1-2.
• Safety requirements for nerve and muscle stimulators were assessed against ISO 60601-2-10.

8. The sample size for the training set:

N/A - This is a hardware device; the concept of a "training set" in the context of machine learning does not apply here.

9. How the ground truth for the training set was established:

N/A - Not applicable.

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