Data; Assessing Limits Of Stability With The Balance System; Interrupting Patient Performance - biodex BALANCE SYSTEM SD Operation & Service Manual

10. DATA

aSSESSING LIMITS OF STaBILITY WITH THE BIODEX BaLaNCE SYSTEM
The Limits of Stability (LOS) for standing balance has been defined as the maximum angle a
body can achieve from vertical without losing one's balance. Once the LOS is exceeded a fall,
stumble or step will ensue. LOS in normal adults is eight degrees anterior, four degrees posteri-
or, and 16 degrees in the lateral direction.
In the static mode the patient's movements are calculated as the average amount of angular dis-
placement of the Center of Gravity (COG). This is then further defined as a percentage of the
patients's Limits of Stability.
At 100% of the LOS, a patient will fall if they don't respond appropriately.
Center is established in the test protocol during the centering process where patients must posi-
tion themselves so the platform is flat and the cursor is centered. In actuality, this process is to
position the COG over the point of the vertical ground reaction force.
An Anterior/Posterior Stability Index of 6.8 means the average displacement from center is 6.8
degrees. LOS for A/P motion is 12 degrees. In this case, the patient was able to control their bal-
ance to remain within 57% of their A/P LOS.
Balance is a complex process involving visual, vestibular and neuromuscular control. The
Biodex Balance System will prove to be a more sensitive test of balance performance because
being a dynamic tilting platform it will invoke the neuromuscular control aspects more so than a
static force plate type system, as well as the visual and vestibular components.
The Biodex Balance System will provide an accurate, reliable assessment of a patient's balance
performance. This objective measure can be correlated to actual functional activity performance,
fall incidence and fall direction. In addition, balance mobility programs can be evaluated
through objective assessment of the effects of lower extremity exercise on balance performance.
INTERPRETING PaTIENT PERFORMaNCE
The patient's performance is noted in the following ways:
1. Stability Index:
The stability index represents the variance of platform displacement in degrees from level. A
high number is indicative of a lot of motion which is indicative of the patients having trouble
balancing. Differences between right and left limbs can be noted.
2. Percent Time in Zone Quadrant:
Example: If a patient with a right lateral ankle sprain spends the vast majority of time in Zone 1,
the trend will be to fall into inversion. This gives feedback as to the exact ankle position being
challenged.
3. Test Grid:
For testing, as the patient goes further and further from the center of axis, the patient is being
challenged to sustain proper position. For rehabilitation, we can note how far the patient can
deviate from the center and still maintain a proper position.
— 10-1 — DATA