Our laboratory found the need for an inexpensive quantitative measure of upper limb kinesthetic sense. So we refined and standardized a protocol for the threshold to detection of passive movement of the elbow. To keep the method feasible, we used a continuous passive motion machine and commonly available laboratory instruments.
Here we present a detailed protocol that yielded valid and reliable results using this method. We suggest the method may also be adopted for other joints in the future. Enjoy the paper.
This protocol requires fabrication of a visual screen. See written protocol for instructions. Begin equipment preparations by calibrating the electric goniometer and EMG sensors according to the manufacturer's instructions.
Turn on the continuous passive motion machine and activate Extension Flexion mode. Program the CPM machine to move through 90 to 130 degrees of elbow extension at a speed of 0.23 degrees per second. Seat the participant in a standard-height chair, ensuring that they are sitting with a straight back and feet flat on the floor.
Verbally prepare the participant for EMG sensor and electro goniometer placement using the standardized script. Next, attach the biceps brachii and triceps brachii EMG sensors. Manually resist elbow flection to locate the biceps brachii muscle belly and mark the central point of the muscle belly with a small dot of washable marker to denote location for EMG sensor placement.
Manually resist elbow extension to locate the central point of the bulk of the muscle belly of the lateral head of the triceps, and denote this location for EMG sensor placement. Prepare the skin by removing dead skin cells, followed by scrubbing with an alcohol swab. Then attach the EMG sensors.
Repeat the process for placement of the triceps brachii EMG sensor. Standardized placement of the electro goniometer begins by identifying landmarks. Determine the midpoint of the dorsal aspect of the wrist, and mark with washable marker.
Palpate the most prominent aspect of the lateral epicondyle and mark with washable marker. Palpate the greater tubercle of the humerus and mark with washable marker. The location of the greater tubercle can be verified by passively moving the testing arm through internal and external rotation.
Attach one end of the string to the lateral epicondyle mark using paper tape. Pull the string taut, connecting it to the dorsal wrist midpoint mark. Trace a line along the proximal forearm, in line with the string, using washable marker.
Move the free end of the string to the greater tubercle mark and pull string taut. Trace a line along the distal humerus and line with the string using washable marker. Then remove the string.
Measure one and a half inches from the lateral epicondyle mark along the proximal forearm line and mark this location with a small dot of washable marker. This is the location for placement of the distal paddle of the electric goniometer. Measure one and a half inches from the lateral epicondyle mark along the distal humerus line and mark the location with a small dot of washable marker.
This is the location for the placement of the proximal paddle of the electric goniometer. Secure the remaining components of the electric goniometer to the skin using paper tape. Position the participant's upper extremity in the CPM machine.
Adjust the height and orientation of the CPM machine to achieve a position of 90 degrees sagittal plane shoulder flection, 90 degrees elbow flection, and a neutral forearm. The participant's lateral epicondyle should be aligned with the rotational axis of the CPM machine. Adjust the CPM hand support to fit comfortably with the palm of the participant's hand, and secure the participant's forearm to the CPM via the wrist strap.
Inform the participant of the testing procedure using the standardized verbal information. Hand participant the switch and test switch. Inform participant of additional aspects of the testing procedure.
Diminish auditory input by placing noise-canceling headphones on the participant. Occlude visual input of the CPM machine and test arm, using the visual screen. Loudly state.Begin.
And wait the corresponding amount of time per trial before initiating movement of the CPM. Monitor EMG sensor feedback readings to ensure the participant does not attempt to use active movement to assist in movement detection. Between each trial, remove the participant's test arm from the CPM machine and passively move the elbow through full extension, then back to 90 degrees for placement in the CPM machine.
Complete eight trials, including two catch trials where the participant's arm is not moved. If during a catch trial, the participant reports they can't feel the CPM move or depresses the trigger switch, use the standardized script. To determine a participant's TDPM value for each trial, use the electric goniometer tracing to identify the angle measurement for the point at which the CPM machine movement started, and for the point at which the participant indicated movement was felt.
The difference in degrees between these two points determines the TDPM value for that trial. To determine a participant's overall TDPM score, remove the smallest and largest TDPM values from the six non-catch trials, then average the remaining four trial scores. Using the standardized method for measurement of the threshold to detection of passive movement at the elbow, 20 healthy adults with no known upper limb pathology were tested.
Additionally, the non-affected upper extremity in eight adults with chronic stroke was tested. Exploratory results demonstrating the TDPM in the healthy adult versus chronic stroke population are shown here. The average TDPM for healthy participants was 1.19 degrees.
The average TDPM for individuals post-stroke was 8.24 degrees. Using a two-tailed T test, this difference between groups was found to be significant, suggesting the discriminative capabilities of this TDPM protocol. In the healthy control participants, a retest was completed one week after the initial measurement.
Spearman correlation and inter-class correlation coefficients were calculated to evaluate test/retest reliability, with the value suggesting moderate to good reliability of the measure among the healthy control participants. Construct validity of this elbow TDPM method was examined by evaluating the Spearman correlation between elbow TDPM and error and targeted reaching, as measured by the tablet version of the brief kinesthesia test. A moderate relationship was found between these two measures of kinesthesia.
This protocol outlines a method for measurement of threshold to detection of passive movement at the elbow that can produce precise, reliable results. It is unique in that it uses equipment that is commonly found in rehabilitation and sensory motor laboratories. The field of sensory motor research is in need of tools that can quantify sensory motor impairment as well as the impact of interventions.
It is our hope that this practical method is found useful by those seeking to advance sensory motor research.
