Range of motion of the joints is vitally important to function.
In the context of peripheral nerve injury, both active and passive ranges of motion are important:
- If innervation is intact, active range of motion though activity of the functioning musculature occurs.
- If innervation is abnormal, the corresponding function and active motion will be decreased.
- As innervation returns, muscles are reinnervated and active range of motion can improve.
If passive range of motion is poor no degree of reinnervation will improve function because the joint will be limited by the passive range in which it can move.
Joint motion can be described as active or passive.
- It is important to explain the difference. Most patients think both active and passive motion will be corrected with reinnervation or a tendon transfer. However, you must emphasize that these will only produce active movement to the degree that there is passive range of movement.
- Passive range of motion:
- Occurs when the examiner moves the joint.
- It does not depend on the innervation of the muscles that normally move the joint.
- It does depend on the structural condition of the joint and will be abnormal of there is edema, fibrosis, ankylosis, scarring of the surrounding soft tissues or other structural changes of the joint/region in question.
- Active range of motion:
- Depends first on passive range of motion–the muscles that move the joint will not be able to move that joint more than it can be moved by the examiner.
- It also does depend on the innervation of the muscles that normally move the joint.
- Loss of active motion is deleterious to overall functional status and restoration of this is one of the prime goals of reinnervation.
Therefore it is critical that passive range is maintained in nerve injury (and, ideally, all) patients by therapy, home exercises, or even surgical means.
Splinting in general is critical both for maintaining joint range of motion and for maintaining the muscles in optimal position for reinnnervation:
- Remember, the muscles are strongest when the fibers are at their resting length (due to the sarcomere force /length curve).
- When a muscle is denervated and becomes stretched out that is a problem.
- This is because when it is eventually reinnervated it will be weaker than if splinting is used to keep the denervated muscles from getting over stretched
- Examples: for radial nerve palsy, think an extension splint for the fingers and a cockup splint for the wrist ; for flexor pollicis longus paralysis, think a flexion block splint to the IP joint of the thumb: and for peroneal nerve palsy think AFO/foot drop splint
It is important to know the terms used to describe motion for specific joints. Some joints have movements that are more complex then others. For example:
- The shoulder girdle has a number of normal planes of motion. It abducts/adducts, flexes/extends, and rotates internally/externally at the glenohumeral joint. It also moves via motion through the connections to the scapula and clavicle.
- The elbow is simpler and flexes/extends.
- The forearm pronates/supinates.
- The wrist flexes/extends and deviates radially/ulnarly.
- The thumb is also complex. It flexes/extends, abducts/adducts and opposes at the carpal-metacarpal joint. It flexes/extends and abducts/adducts at the metacarpal-phalangeal joint. It flexes and extends at the interphalangeal joints.
- The remaining fingers also flex/extend and abduct/adduct at the metacarpal-phalangeal joint. They flex/extend at the interphalangeal joints. The small finger can also oppose.
Quantitative measurement of joint range of motion is done using goniometry and other techniques.
- Simple device that allows measurement of the angle and range of joint motion.
- Useful for quantitating the passive and active range of motion at a joint. Comparing the two will then allow strength measurement as a muscle”™s ability to move a joint through all the available passive range is measured.
- To measure:
- You have to understand the alignment of the bones comprising the joint and align the arms of the goniometer parallel to the bones.
- Read the angle accordingly.
- Keep convention in mind that–for example for measurement of the metacarpal-phalangeal joint, 0° degrees is completely straight, hyperextension beyond zero is noted as positive (+) number, and an extension lag is noted as a negative (““) number.
- One way to follow clinical outcomes over time as motor function is restored is to actually measure the range of motion gained. At first measure with gravity eliminated, then against gravity, and finally, as recovery occurs, with full power through the full range of motion.
- Distance of movement:
- Distance is another quick way to quantify motion–for example, the pulp to palm distance (from the finger tip to the distal palmar crease on attempted flexion) is a quick way to track progressive improvement after surgery for nerve transfer, tenolysis and other procedures. It is useful for following function in a single patient from visit to visit, however, it is not as reliable as the goniometric measurements and should not be used to compare cross-patient and other data.