Seguro mixto simple

The interosseous (in- tur- AW- see- us) muscles fill the space between the four metacarpal bones in the hand (figure 6.44). Note that these small muscles occupy only the half of the hand nearest the fingers. The heel of the hand is filled with carpal bones. There are two sets of interosseous muscles. The four dorsal interosseous are acces- sible from the back of the hand. They move the index and fourth fingers away from the middle finger and move the middle finger from side to side. The three palmar interosseous muscles are accessible through the palm. They bring the fingers together by moving the index, fourth, and fifth fingers toward the middle finger. All seven interos- seous muscles have a role in the grasping function and in the many subtle manipulations of the fingers and hand. Trigger points in the interosseous muscles refer pain to the sides and undersides of the fingers and the last finger joints. They contribute to finger stiffness, weakness, and awkwardness. Interosseous muscles can cause numbness in the fingers when they compress the digital nerves, which also lie between the metacarpal bones. The digital nerves are sensory nerves for the fingers (Simons, Travell, and Simons 1999).

The bulky, highly developed first dorsal interosseous muscle makes up most of the web between the index finger and thumb (figure 6.45). Its trigger points have a much wider referral pattern, sending pain to the palm, the

Figure 6.44 Dorsal interosseous trigger points and referred pain pattern. The abductor digiti minimi manus muscle, trigger point, and referred pain are also included in this drawing.

Figure 6.45 First dorsal interosseous trigger points and referred pain pattern

Chapter 6—Elbow, Forearm, and Hand Pain 153

little finger, the back of the hand, and all surfaces of the index finger. They frequently refer a deep ache to the entire ulnar (pinky side) side of the hand. To locate the first dorsal interosseous muscle, see and feel it bulge up as you press the index finger against the thumb (figure 6.46).

If writing with a pen or pencil gives you pain in the underside of your middle finger and its last knuckle, look for a trigger point in the second dorsal interosseous muscle, between the metacarpals of the index and middle fingers. This muscle helps the middle finger push against the thumb to grip the pen between them. Fixing writer’s cramp is often only a matter of finding the hand muscles that have the trigger points. The short thumb muscles and the first dorsal interosseous are the usual source of writer’s cramp, but don’t overlook the others.

Heberden’s nodes, bumps on the sides of the last knuckles, are thought to originate with trigger points in overused interosseous muscles. Bumps on the middle knuckles are called Bouchard’s nodes. It may be possible to eliminate both kinds of nodes by trigger point therapy to the interosseous muscles if intervention comes early enough. Even if fully developed, nodes can often be reduced. The same stresses in the interosseous muscles that create nodes on

the knuckles may contribute to the development of arthritis (Simons, Travell, and Simons 1999).

Players of musical instruments like the piano, violin, or guitar, who must often spread their fingers to extreme positions to reach notes, are especially prone to overuse of the interosseous muscles. Repetitive, powerful gripping with the fingers on the job or in a sports activity also risks overloading these small muscles.

Your computer mouse puts both the first dorsal and first palmar interosseous muscles at risk of overuse if you use your index finger to click the buttons. The mouse also predictably overworks the extensor indicis and part of the extensor digitorum, which work together to lift the finger between down strokes. If you position your mouse far to the side of your keyboard, you’re likely to create trigger points in your infra- spinatus, teres minor, trapezius, rhomboid, and anterior deltoid muscles because of the continuous outward rotation and forward flexion of the arm. A good solution to the mouse problem may be an ergonomic keyboard with a built- in touchpad mouse.

The tip of a supported thumb can be used to massage the interosseous muscles (figure 6.47). Deeper massage can be done with a wedge- shaped rubber eraser, held in a small spring clamp to save your fingers. Figures 6.48 and 6.49 show two different kinds of erasers that can be found everywhere. One is a big pink eraser; the other fits over the end of a shortened pencil, which is then gripped in the clamp. The inexpensive plastic spring clamp shown in the illus- trations can be found at many variety, department, and hardware stores.

Figure 6.46 Locating first dorsal interosseous by isolated contraction

Figure 6.47 Dorsal interosseous massage with supported thumb

Massage the thick first dorsal interosseous by pressing it against the metacarpal bone with supported thumb (figure 6.50). The hand will be held in a neutral position, as if holding a cup. It works well to have your hand resting in your lap while massaging with an eraser or supported thumb. Be slow and detailed in your search for trigger points; there can be several in this muscle. Trouble with the interosseous muscles can be difficult to resolve. They’re not easy to massage and your activities may be keeping them under continuous stress. Give serious thought to changes you can make in the way you use your hands that will give these special muscles a break.

Figure 6.48 Eraser massage

of interosseous Figure 6.49 Spring clamps and erasers for massage of interosseous muscles

Figure 6.50 First dorsal interosseous massage with supported thumb. Press the muscle against the bone.

Chapter 7