Sample chapter from The Hand, Wrist, and Arm Sourcebook

Christine M. Kleinert Institute for Hand and Micro Surgery

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SAMPLE CHAPTER: The Hand, Wrist, and Arm Sourcebook
By Steven McCabe, MD, and Stan Goldman, PhD

Introduction: The Wonders of the Hand and Upper Limb

The human hand and arm are as biologically astonishing as sight or hearing. The upper limb, which includes the hand, wrist, forearm, elbow, arm, and shoulder, is an essential tool that allows us to drink, eat, dress, keep clean, earn a living, and make love. In fact, the primary function of the upper limb is to position the hand in space as a tool and a sensory organ. Our hands and arms are the best tools we have, and our hands also "see" as they sense temperature and space. When we grope our way in the dark, our hands become our eyes. Besides movement and sensation, our hands also protect us. The graceful, elongated fingers can be made into a fist, our species’ most basic weapon. Since our upper limbs are so important to us, people are naturally fascinated with the function and design of the upper limb. The spiral cascade of the fingers; the biomechanical dexterity of the wrist, elbow and shoulder; and the strength of our hand and arm muscles provide us with a unique connection to the outer world.

Unfortunately, we often fail to appreciate the function, sensation, and beauty of the upper limb until it is injured. If you have injured your hand or arm or if you suffer from common conditions such as carpal tunnel syndrome or arthritis, you are not alone. Each year in the US, there are 18 million acute injuries to the hand, arm, or shoulder and almost 24 million visits to physicians for upper limb disorders. One quarter of all disabling work injuries in the US involve the upper limbs.

Upper-limb injuries, arthritis, and other disorders have devastating economic and psychological consequences. In fact, losing the use of your hand often means losing your job. Our hands are also part of our self-identity. We decorate hands with rings as celebratory symbols of status and power, friendship and love, education and athletics. Wedding bands, high school rings, super bowl rings, gold bracelets, even tattoos—all help project ourselves to others. At a job interview, the handshake becomes a crucial part of that important first impression we make on others. Hearing impaired people use their hands to talk in sign. For visually impaired people, the hand can feel the shape or temperature of an object. If you pay attention to how most people look at each other, they usually look at the face first, but inevitably gaze at the hands second. Our hands are a representation of who we are. That is why nails and hands are sites of personal adornment and expressions of fashion, from nail lacquer to thumb rings.
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In the most extreme injuries that result in amputation, hand loss can be more psychologically traumatic than leg loss. Patients with severe upper-extremity injuries often suffer psychologically from post-traumatic stress disorder, similar to the shell-shock that soldiers experience after war. This post-traumatic stress causes nightmares, flashbacks, irritability, and avoidance of the site of injury, often the workplace. Amputees who lose the hand or arm grieve for their lost limbs as they would mourn the death of a loved one. They may experience denial, pining, anger, guilt, shame, alienation, anxiety, tension, insecurity, and depression.

We chose the subject of the book because humans' upper limbs are so interesting and so important--psychologically, socially, and economically--and yet are often taken for granted. Our purposes are

to encourage people to appreciate this unique biomechanical wonder--the human upper limb.
to provide a clear, concise, and readable guide to understanding the hand, wrist, forearm, elbow, arm, and shoulder for people who are not health professionals.
to teach people strategies for preventing common injuries such as household accidents.
to explain to people the treatments for disorders such as tendonitis, carpal tunnel syndrome, arthritis, distal radius fractures (wrist fractures), golfer’s elbow, and tennis elbow.
to help an aging population care for their upper limbs affected by arthritis, pain, and decreased function.
to teach people how to be informed consumers in the health care process, for example, posing questions to a surgeon, having realistic expectations, and complying with rehabilitation programs.
to give conservative treatment options to patients before considering surgery.
to help injured workers understand workers’ compensation from the viewpoint of the doctor, the employer, and the patient.

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This book has an introductory chapter and then four sections. This first chapter gives an overview of the structure and function of an amazing piece of machinery, the human hand.

Section one will discuss many of the common injuries to the hand and arm such as fractures of the distal radius (so-called broken wrist), lacerations (cuts), fingertip injuries, and other injuries that surgeons see repeatedly. This section stresses injury prevention.

Section two will talk about non-injury conditions that affect the hand such as carpal tunnel syndrome, ganglions, trigger digits, and tendonitis. This second section focuses on causes, diagnoses, treatments, and outcomes for each common disorder.

Section three focuses on the aging hand, especially arthritis. Section four discusses how to make better decisions about healthcare for your hand and upper limb. The more you know about your injury or disorder, the more likely you are to seek help at the appropriate time, participate in making treatment decisions, recognize when treatment is working or not, and achieve satisfaction with the results. Here we give practical advice if you are about to undergo hand or wrist surgery: choosing the properly trained surgeon, asking the most effective clinical questions, actively participating in a quick recovery from surgery. Throughout section four, we take the conservative position that you should know and try all the alternative treatment options before agreeing to non-emergency (elective) surgery. Surgery is controlled injury and should not be considered until all other options are explored. Furthermore, you must have realistic expectations about the outcome of surgical procedures. Although surgery is often necessary, the limb may not return to a fully functional condition after surgery.
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Each chapter includes a description of the common conditions that affect the upper limb from the perspective of the doctor and the patient, the natural history of the condition, and treatment. We offer advice about when to see a physician, and when to see a specialist in treatment of the hand and arm. Diagnosis, treatment, medication, and surgery are discussed for each condition. As an example of the condition, each chapter has a case history of a patient, a line drawing, or a photograph. Each chapter ends with bullet points or questions called "The Facts in Hand" or "The Questions in Hand" that are the most important medical points to remember from the chapter or important clinical questions that you should ask the doctor.

This chapter is written to share our amazement of the wonderful structure and workings of an incredible piece of biological machinery, the human hand. There is an intricate and inseparable link between the structure (anatomy) of the hand and the way it works (function). The more carefully we study the anatomy, the more refined is our understanding of how the hand works. The more we learn how the hand is used, the more informed is our study of its anatomy. After an injury, knowledge of hand anatomy gives you and your doctor a blueprint for repair and reconstruction that will give you the best possible function.
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Function

Although the hand is relatively unconstrained and used in many ways, if you observe people using their hands in daily activities, you can see that the hand functions in a few specific repeating patterns. The most basic patterns of hand use are pinch and grip. Key pinch is a strong method of pinching which is self-descriptive. An object is pinched between the pulp of the thumb and the side of the index finger. Tip pinch is not as strong as key pinch. In tip pinch, the object is pinched between the tips of the index finger and the pulp of the thumb. Power grip is the position of the hand as it holds a hammer, a baseball bat, or a tennis racquet. The wrist is in extension, and the fingers are fully flexed into the palm around the object. Hook grip is applied with the fingers hooked around an object such as when carrying a suitcase. In the hook grip, the wrist is in neutral position, in a straight line with the forearm. The final commonly used functional position is the so-called flat hand. The flat hand is used to push and hold objects. The entire upper limb--the wrist, forearm, elbow, arm, and shoulder--has the primary function of positioning the hand to achieve these five basic functions.
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Terminology

Fig. 1. Line drawing of finger flexion and extension.

To communicate effectively about the hand, there are some basic anatomic points that are important. In referring to a feature of the anatomy closer to the center of the body, we use the term proximal. Distal refers to a point farther away from the center of the body. Superficial refers to something closer to the surface. Palmar is the palm side of the hand, and dorsal is the back of the hand. Flexion is the act of bending the fingers and thumb into the palm of the hand; extension is the act of straightening the fingers.
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Anatomy

Bones

Bones are hard structures composed of living bone cells, surrounded by a hard, strong, supportive calcium frame. Ligaments connect bone to bone at joints. Ligaments are primarily made of collagen, a strong rope-like material that imparts stability to joints, preventing them from moving past their appropriate anatomic limits. The bony or skeletal anatomy of the upper limb allows the hand to be positioned in space to perform activities and to evaluate the surrounding environment.

Fig. 2. Line drawing of the bones of the upper limb. The single bone of the upper arm is called the humerus, located between the elbow and the shoulder. The humerus articulates (moves) with the scapula (the bone that contains the shoulder blade) to form the shoulder joint, a shallow ball and socket joint that is inherently unstable but allows tremendous freedom of motion. Shoulder surgeons affectionately and accurately call the shoulder joint a "ball in a wall." The joint is supported by a ring of muscles called the rotator cuff that provides stability to the shoulder joint and helps it move. These muscles are prone to injury in the middle years of life and to atrophy (muscle wasting) in later years.

At the distal end of the arm, the humerus ends at the elbow joint. This joint is a hinge-like joint that is quite constrained, but allows over 100 degrees of motion in a single plane and rotation of the forearm. The prominent firm bumps at each side of the elbow are the distal ends of the humerus, the lateral (on the outside), and the medial (on the inside) epicondyles. These are the sites of inflammation in tennis and golfer’s elbow that we discuss in chapter 12.
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The forearm has two long bones, the radius and ulna, that form joints with each other and the humerus at the elbow and with each other and the bones of the wrist at the wrist. Flexion of the elbow allows the hand to reach the face and mouth so that we can eat. Rotation of the forearm is accomplished by the radius rotating along its long axis at the elbow and around the ulna at the wrist. The most common fracture, or broken bone, is at the distal end of the radius, commonly occurring with a fall. This so-called broken wrist is really a broken bone in the forearm--the radius. Structures that lie on the same side of the forearm as the radius are called radial in their position. Those structures on the same side as the ulna are called ulnar in their position.

Like a bag of bones, the hand and wrist are made up of 27 bones, the highest number of integrated, coordinated bones per tissue area in the human body. The wrist is comprised of 8 bones, the carpal bones, aligned in 2 rows. Motion of the wrist is accomplished by a complicated symphony of interdependent motions between the carpal bones and the radius and ulna. The wrist also transfers the load (weight) from the hand to the bones of the forearm. The position and motion of the 8 small bones are controlled by a complicated set of ligaments between the various bones.
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Fig. 3. Line drawing of the bones and joints of the hand and the bones of the wrist.

The hand has 5 tubular bones called metacarpals that bridge the distance between the wrist and the digits. Each of the digits, the four fingers and the thumb, has a corresponding metacarpal bone in the hand. There is very little motion between the metacarpals and the wrist for the index finger and the long finger. The metacarpal for the thumb is very mobile at its base as are the joints between the wrist and the metacarpals for the ring and small fingers. To prove this to yourself, grasp the large knuckle at the base of the index finger and try to move it up and down vertically. There is very little motion. Now do the same with the large knuckle of the small finger. It will move about 1-2 inches. At the base of the fingers and thumb, the large knuckles are called the metacarpophalangeal joints or MCP joints. These joints allow the finger to flex and extend into and out of the palm of the hand. Flexing the fingers into the palm makes a fist. Extending the fingers away from the palm makes a flat hand. When in extension, the MCP joint has some motion side to side horizontally. But in full flexion, the ligaments become tight, and the MCP joint cannot be moved side to side horizontally. (Try moving your large knuckle joint of your index finger side to side when the hand is in a tight fist--you cannot--and then when the hand is straight.) The two smaller knuckles of the fingers, the interphalangeal joints, are fairly flat single joints that move in one plane. The interphalangeal joints are constrained from moving sideways by their bony architecture and strong ligaments along the sides of the joints.

The bones of the fingers are called phalanges, each one is a phalanx. The fingers each have three phalanges, but the thumb has two. The bones of the fingers, the phalanges, have an interesting length relationship. The distal phalanx, the last bone in the finger (under the nail) is the shortest. The middle phalanx is somewhat longer, and the proximal phalanx is the sum of the length of the distal and middle phalanges. The sum of the lengths of the middle and proximal phalanges is equal to the length of the metacarpal bone. This relationship forms a sequence of numbers known as the Fibonacci sequence, which is often expressed in nature and forms the basis of an equiangular spiral. This same equiangular spiral is repeated throughout nature, apparent in the shape of the nautilus shell, a hurricane, and even galaxies. When moving your fingers in a cascade, from small finger to index finger, as magicians do during a magic trick, you can see the spiral curve at work.
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Muscles

Muscles are contractile tissues that shorten when they receive an electrical signal from a nerve. The muscles usually originate (start) on a bone and form a long tendon that joins (inserts) into a different bone, passing across one or more joints. A tendon is a rope-like structure that connects a muscle to a bone. When the muscle shortens, it exerts a force that causes the joint to move to shorten the distance between the muscle’s origin and insertion.

Muscle groups are described by their location and the action that they have on joints. The large muscles of the upper chest and back are responsible for moving and controlling the position of the shoulder. The muscles of the rotator cuff are a group of muscles passing close to the shoulder joint that helps to stabilize the joint and assist with its motion.

The biceps, a muscle well known to us, is assisted by other muscles in its action of flexing the elbow joint. On the back (posterior) surface of the arm, the triceps extends (straightens) the elbow. On the forearm, the muscles on the flexor surface (where your skin is lighter in color) flex the wrist and digits; the muscles on the extensor surface (where the skin is usually hairy) extend the wrist and digits.

The small muscles within the hand are called the intrinsic muscles. These small muscles act to coordinate the fine movements of the fingers and thumb.
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Nerves

Nerves are biological electrical cables. They consist of long extensions of nerve cells that are located within or adjacent to the spinal cord. These long extensions, called axons, are insulated by myelin. Hundreds of thousands of axons are gathered together in a nerve.

Nerves transmit electrical signals in two directions. Sensory information such as touch and temperature from the skin and the position of the joints and muscles are collected and transmitted to the spinal cord and brain. In the opposite direction, our will to move our hands is created in the brain and transmitted through our spinal cord and nerves to the muscles where the electrical impulses cause the muscles to contract, changing the position of the joints.

Fig. 4. Line drawing of the major nerves of the upper limb. The nerves to the arm exit the spinal cord in the neck and have a complicated intermingling as they pass across the side of the neck and under the collarbone. This area is called the brachial plexus. In the mid-arm the nerves have sorted themselves out to three large nerves of the forearm and hand: the median, ulnar, and radial nerves.

The median nerve travels to the hand between the muscles of the forearm. At the wrist, it passes through a tunnel, the carpal tunnel, a common site of compression of the nerve. The median nerve provides the motor nerves for the muscles that flex the wrist and fingers. The median nerve also serves the small muscles in the ball of the thumb, particularly the muscle that lifts the thumb away from the plane of the hand. The sensation from the thumb, index, and long fingers and half of the ring finger is carried by the median nerve.

The ulnar nerve carries the sensation from the small finger and half of the ring finger, as well as the back of the hand on the ulnar side (by the small finger). The ulnar nerve lies on the ulnar side of the forearm. It passes behind the elbow joint and is susceptible to injuries and compression at this spot. When this nerve receives minor bumps, an electrical shock shoots down the hand, the so-called crazy bone or funny bone. The muscles supplied by the ulnar nerve aid in flexion of the fingers and power most of the small muscles of the hand, including those that extend the interphalangeal joints of the fingers.

The radial nerve powers the muscles that extend the elbow, wrist, and digits. The sensation from the skin on the back of the radial side of the hand is transmitted by this nerve.
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Blood Vessels

Fig. 5. Line drawing of the major arteries of the upper limb.

Blood vessels are the pipes that deliver the circulation to the tissues, providing nutrition and removing waste material. Arteries are blood vessels that deliver blood from the heart to the body. In the arm, a single large artery, the brachial artery, carries the blood to the level of the elbow. In the region of the elbow, this artery divides to form the radial and ulnar arteries that are the main two arteries supplying blood to the hand. The radial artery is superficial at the wrist and is the location where the pulse is typically felt. The arteries form two arches in the hand from which branches of the arteries provide circulation to the digits. Each digit has two arteries.

One important characteristic of the circulation to the hand is the redundancy of the system. A single artery can be cut anywhere in the hand and, assuming there is no disease of the remaining blood vessels, the circulation to the hand would be adequate.

The circulation to the hand also has the role of regulating temperature. Heat is created in the trunk of the body. The blood vessels carry this heat to the periphery where it is dispersed. The blood is returned to the heart through a large number of veins that contain valves. These veins can be seen on the back of the hand.

One can easily reproduce a famous Renaissance experiment proving that there are valves in the veins and that blood in the veins travels toward the heart. Put your finger on one of the veins on the back of your hand, close to the large knuckles. The veins are the blue longitudinal lines on the back of the hand. Now, holding the first finger down on the vein, with another finger, milk the blood in a direction away from the first finger to the wrist. Continue to hold down the first finger. When you let the second finger off the vein, the blood will not travel all the way back to the first finger. The vein will remain collapsed. When you remove the first finger, the vein once again will fill with blood. This experiment proves that there are valves in the veins and that blood in the veins is travelling toward the heart.
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Skin

The skin is an amazing organ, our first line of defense against bacteria and other pathogens. In the upper limb, the skin also participates in heat exchange. The skin on the back of the hand is very mobile and extensile. When we flex the fingers into the hand, as in a fist, the loose skin becomes tight. Take your index finger and place it on the back of the other hand. Now push with your finger and role it on the back of the hand. The skin is mobile and will move an inch or so. Now make a fist and try to move the skin on the back of the hand with your index finger. The skin is much less mobile. In young people, there is little redundancy of the skin. When a young person makes a fist, the skin on the back of the hand stretches as a result of its inherent elasticity. One characteristic of the aging process is the loss of skin elasticity. Luckily, as we get older, increasing redundancy makes up for this loss in elasticity. Since we have lost the elasticity, the extra skin allows us to make a fist. Now place the index finger on the skin of the palm. We are unable to move the skin on the palm of the hand with the finger. This property allows us to hold an object firmly and is the result of fibrous tissue holding the skin of the palm. This fibrous tissue is called fascia (sounds like "splash a") and is also the structure that creates the creases in our palm.

Another remarkable characteristic of the skin of the hand is its specialized sensory capability. Specialized microscopic sensory receptors occupy the skin and receive messages from pressure, vibration, and temperature, passing these to the brain through the nerves. The skin on the palm side of the hand is glabrous, in other words, hairless. This glabrous skin along with a small amount of moisture from sweating and the developed ridges that we see as our fingerprints give a slight friction to the skin that improves contact with objects.
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Nails

The nails are specialized structures related to the skin. They are made of keratin. There is no living tissue in the actual nail. This is why it does not hurt when we cut our nails. The nails form under a fold of skin at the tip of the digit. The nail’s function is to improve the ability of the tip of the finger to pinch and touch and to protect the tip of the finger.

Look at your fingernails. Are they chewed down, red, and bleeding? Nail biting is a habit that develops in childhood and continues throughout life for many people. It does put you at some increased risk of nail bed infection from bacteria in your mouth, but generally speaking, other than its aesthetic aspect, it is harmless. Many people are the complete opposite. They put the importance of the appearance of their nails above the actual use of their hands. Artificial nails are in fashion now, the longer the better. These nails can get to be so long, they actually interfere with and change the way we use our hands. Instead of using the tips of the fingers for touching the keyboard or picking up objects, the long nails get in the way and force the wearer to use the pad of the finger. Many illnesses show themselves in the fingernails. Psoriasis for example has distinctive nail changes as does chronic lung disease and certain types of heart problems. In Caucasians, malignant melanoma, a dangerous kind of skin cancer, can appear with a brown streak under the nail.
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Calluses

If you use your hands for activities, they will show the effects of those activities. Calluses are a good example of the hands’ response to use. If you cut the grass and do a little gardening, you will probably have a small callus at the base of the small, ring, and long fingers on both hands. If you play a stringed instrument, you will have calluses on the tips of the fingers of your left hand. If you do vigorous work, your palms may be very thick and rough. If you still write with a pen instead of a keyboard, you may have a callus at the smallest knuckle of your middle finger. The formation of a callus is a normal reaction to use. Sometimes we have patients come to the office who report that they have been unable to do anything for a long time with their hands as a result of an injury, but on inspection, they have thick calluses. The two cannot both be true, and the calluses cannot lie. Your hands are a window into who you are.
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Cracking the Knuckles

Have you ever been sitting in a library quietly reading and the person at the other end of the table continuously cracks the knuckles? You probably have wondered what is actually happening when a knuckle cracks? Is it the bone? Is it the tendon? Does anything break? Interestingly, there are a several possible causes for our knuckles to make noises. If there is roughness of the joint surfaces, you may have the sensation of grinding or rubbing called crepitation. This will give a fine crackling sensation like sandpaper, but not a loud crack. If you have had a fracture in the joint, there may be a step in the surface that causes a clunk as the joint moves. This is a rare problem. In the wrist, the ligaments keep the small bones in their correct orientation. If there is a disruption of these ligaments, the bones can move about in relation to each other and can clunk together with certain motions. The typical cracking of the knuckles occurs at the metacarpophalangeal joints and is likely because of one of two situations. Most likely, when you manipulate the joints to make them crack, you are setting up a vacuum in a recess of the joint inside the joint capsule. Then with further manipulation, the vacuum sucks the joint fluid and suddenly fills, making a crack. Think of it as opening Tupperware. The other possibility to explain cracking of the knuckles is that the extensor tendon for the finger is snapping over the bony prominence of the metacarpal head. There are probably no ill effects from cracking your knuckles if it is not painful and you do not have a nerve injury. If you have had a nerve injury, you should not crack your knuckles.
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Justice in Anatomy

There is a trend in society to reduce our body fat. It seems that having washboard abdominal muscles is one of the great desires of the new millennium. Please be aware that reduction of body fat will thin the subcutaneous fat (the fat under the skin), and this will occur over the entire body. This reduction of fat will cause the skin on the back of the hand to have more of a wrinkled appearance and to make the veins more prominent. The hands are the second most adorned part of the body. Those people with washboard abdominal muscles have older looking hands. There is justice in anatomy.
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Summary

Formed by bones and joints, activated by nerves and muscles, wrapped in skin, fed nutrients by the blood vessels, and mobilized by the human brain, the upper limb is a remarkable structure that has been vital for the development of the species and is essential to an individual’s physical, psychological, and economic health.
Symptoms and functional limitations caused by illness or injury of the hand and arm are profound in their impact, threatening our identity as well as limiting our daily activities.
Knowledge of hand and arm anatomy gives you and your surgeon a blueprint for repairing injured structures.