The FREEHAND Implantable Functional Neurostimulator System (FNS)(NeuroControl, Cleveland, OH) is a radiofrequency (RF) powered motor control neuroprosthesis that consists of both implanted and external components. It utilizes low levels of electrical current to stimulate the peripheral nerves that innervate muscles in the forearm and hand providing functional hand grasp patterns. The NeuroControl FREEHAND System consists of the following subsystems:
The (Implanted Components include the Implantable Receiver-Stimulator, Epimysial and Intramuscular Electrodes, and Connectors (sleeves and springs);
The External Components include the External Controller, Transmit Coil, Shoulder Position Sensor, Battery Charger, and Remote On/Off Switch;
The Programming System consists of the Pre-configured Personal Computer loaded with the Programming Interface Software, the Interface Module, and a Serial Cable;
The Surgical Implementation Components include the Electrode Positioning Kit (the Surgical Stimulator, Epimysial Probe, Anode Plate, and Clip Lead); and
The Intramuscular Electrode Insertion Tool Kit (the Intramuscular Probe and the Cannula). The Intramuscular Electrode is preloaded in the Lead Carrier with Carrier Cover.
The NeuroControl FREEHAND System is intended to improve a patient's ability to grasp, hold, and release objects. It is indicated for use in patients who:
-are tetraplegic due to C5 or C6 level spinal cord injury (ASIA Classification)
-have adequate functional range of motion of the upper extremity
-have intact lower motor neuron innervation of the forearm and
-hand musculature and are skeletally mature
The NeuroControl FREEHAND System may only be prescribed, implanted, or adjusted by clinicians who have been trained and certified in its implementation and use.
-Monopolar Electrosurgical Instruments should not be used on the implanted upper extremity. These tools could damage the Implantable Receiver-Stimulator. Bipolar electrosurgical instruments can be used safely in coagulating mode.
-Electrostatic Discharge (ESD) may damage the FREEHAND Implantable Receiver-Stimulator during intraoperative handling. Handle only as instructed in the Clinician's Manual.
-Neuromuscular Blocking Agents (long-acting) should not be administered during implantation surgery. These agents render nerves unresponsive to electrical stimulation and may compromise the proper installation of the device.
Surface Stimulation: Electrical surface stimulation (muscle stimulator, EMG, or TENS) should be used with caution on or near the implanted upper extremity as it may damage the system. Contact NeuroControl prior to applying surface stimulation.
X-rays, mammography, ultrasound: X-ray imaging (e.g., CT or mammography), and ultrasound have not been reported to affect the function of the Implantable Receiver-Stimulator or Epimysial Electrodes. However, the implantable components may obscure the view of other anatomic structures.
MRI: Testing of the FREEHAND System in a 1.5-Tesla scanner with a maximum spatial gradient of 450 gauss/cm or less, exposed to a whole body averaged Specific Absorption Rate (SAR) of 1.1 W/kg, for a 30 minute duration resulted in localized temperature rises no more than 2.7oC in a gel phantom (without blood flow) and translational force less than that of a 3-gram mass and torque of 0.063 N-cm (significantly less than produced by the weight of the device).
A patient with a FREEHAND System may undergo an MR procedure using a shielded or unshielded MR system with a static magnetic field of 1.5-Tesla only and a maximum spatial gradient of 450 gauss/cm or less.
The implantable components may obscure the view of other nearby anatomic structures. Artifact size is dependent on variety of factors including the type of pulse sequence used for imaging (e.g. larger for gradient echo pulse sequences and smaller for spin echo and fast spin echo pulse sequences), the direction of the frequency encoding, and the size of the field of view used for imaging. The use of non-standard scanning modes to minimize image artifact or improve visibility should be applied with caution and with the Specific Absorption Rate (SAR) not to exceed an average of 1.1 W/kg and gradient magnetic fields no greater than 20 Tesla/sec.
The use of Transmit Coils other than the scanner's Body Coil or a Head Coil is prohibited. Testing of the function of each electrode should be conducted prior to MRI scanning to ensure no leads are broken. Do not expose patients to MRI if any lead is broken or if integrity cannot be established as excessive heating may result in a broken lead.
The external components of the FREEHAND System must be removed prior to MRI scanning. Patients must be continuously observed during the MR procedure and instructed to report any unusual sensations (e.g., warming, burning, or neuromuscular stimulation). Scanning must be discontinued immediately if any unusual sensation occurs. Contact NeuroControl Corporation for additional information.
Antibiotic Prophylaxis: Standard antibiotic prophylaxis for patients with an implant should be utilized to protect the patient when invasive procedures (e.g., oral surgery) are performed.
Ultrasound: Therapeutic ultrasound should not be performed over the area of the Implantable Receiver-Stimulator or Epimysial Electrodes as it may damage the system.
Diathermy: Therapeutic diathermy should not be used in patients with the NeuroControl FREEHAND System as it may damage the system.
Therapeutic Radiation: The electronic components in the FREEHAND System may be damaged by therapeutic ionizing radiation. The damage that occurs may not be immediately detectable. Any changes in sensation or muscle contraction should be reported to the physician. If the changes are painful or uncomfortable the patient should stop using the FREEHAND System pending review by the clinician.
Invasive Procedures: To avoid unintentional damage to implanted components, invasive procedures such as drawing blood or administering an intravenous infusion should be avoided on the implanted arm or in the area of the Implantable Receiver-Stimulator or near sites of the Epimysial Electrodes.
Serum CPK levels: Exercise and muscle activity are known to cause changes in certain blood enzymes measured by standard laboratory and clinical tests, such as serum CPK. Exercise, whether volitional or induced by electrical stimulation, may produce elevated serum CPK levels. If a FREEHAND System patient has elevated CPK, fractionation is indicated to differentiate between CK-MM from skeletal muscle and CK-MB from cardiac muscle that could be the result of cardiac injury.
Drug Interactions: Muscle inhibitors and muscle relaxants may affect the strength of muscle contraction achieved using the FREEHAND System. It is recommended that these medications be stabilized prior to implementing the FREEHAND System so that muscle response to electrical stimulation can be accurately evaluated.
Electrostatic Discharge (ESD) exposure can cause loss of current amplitude programmability which also produces stimulus current amplitude higher than default. This does not result in any increased safety concerns from stimulation, has not caused compromise in hand function, and device operation will remain stable in this mode of operation. If a patient indicates that an increase in grasp strength is suddenly observed, this malfunction mode should be considered and evaluated. Changes in hand grasp can be managed by reprogramming grasp patterns, usually lowering stimulus pulse widths.
Pacemaker Warning Areas: Patients should avoid areas posted with a warning to persons who have an implanted pacemaker. Contact NeuroControl Corporation for additional information.
Studies have not been conducted on the use of the NeuroControl FREEHAND System in patients with the following conditions:
-children who are skeletally immature (usually males < 16 years, females < 15 years)
-prior history of a major chronic systemic infection or other illness that would increase the risk of surgery
-poorly controlled autonomic dysreflexia
-seizures and balance disorders
Risks and benefits in patients with any of these conditions should be carefully evaluated before using the FREEHAND System.
Safety critical tasks: Patients should be advised to avoid performing tasks which may be critical to their safety, e.g., controlling an automobile (throttle or brake), handling an object that could injure the patient (scald or burn), etc.
The patient should be advised to avoid the use of a compression cuff for measuring blood pressures on the arm in which the FREEHAND System is implanted.
Post-operatively, the patient should be advised to regularly check the condition of his or her skin across the hand, across the volar and dorsal aspects of the forearm, and across the chest where the FREEHAND System Receiver-Stimulator, leads and Electrodes are located for signs of redness, swelling, or breakdown. If skin breakdown becomes apparent, patients should contact their clinician immediately. The clinician should treat the infection, taking into consideration the extra risk presented by the presence of the implanted materials.
Keep it dry: The user should avoid getting the external components, cables, and attachments of the FREEHAND System wet.
The patient and caregiver should be advised to inspect the cables and connectors regularly for fraying or damage and replace components when necessary.
Excerpted with permission from the Package Insert, FREEHAND System, NeuroControl Corporation, Cleveland, OH
For a neurostimulation system, MR healthcare professionals are advised to contact the manufacturer of the specific device to ensure that the latest safety information is obtained and carefully followed in order to ensure patient safety relative to the use of an MR procedure.