14
Muscle, Bone, and Joint Health
PRior To My Injury, I exercised vigorously for one hour every day. My good health helped me after my injury; during my ten days in the ICU, unable to move, I lost five percent of my muscle mass. I’m positive that the health of my body at the time of my injury and my love of physically demanding workouts were (and continue to be) instrumental in my recovery.
Don’t get me wrong—after my accident, I was paralyzed. The effort it has taken to get to where I am today has been significant. From the moment it began, my physical therapy was excruciatingly difficult and left me completely exhausted. All these years later, PT is still a challenging part of my life, but I know the benefits are worth the effort and, yes, the pain. Making my muscles work hard helps my heart, my lungs, my bones and joints, and even my brain. It also means I can be as independent as possible, which improves my quality of life. And all of that means greater longevity.
Your ability to exercise will be a fundamental component of successful functional recovery, and also for maintaining muscle mass and bone density. If you’re paralyzed and unable to move, your muscles and bones waste away, making exercise difficult, which sets in motion a vicious cycle. But the good news is that you can break that cycle. Existing technologies that move paralyzed limbs, such as functional electrical stimulation (Figure 26; see page 184), body weight support and balance systems, robots, and exoskeletons (Figures 27–29; see pages 185–186), are useful. There are also less expensive ways to support your muscle and bone health, depending on the severity of your injury. Let’s take a look.
Muscle Function
Skeletal muscles are made up of bundles of muscle cells, or fibers; most skeletal muscles are attached to bones by tendons. For a muscle to move, a signal must be transmitted from the top of your brain (the motor cortex) down the spinal cord in a neuron. The neurons leave the spinal cord as a nerve fiber, and then spread out over the muscle to cause it to contract. This combination of motor neuron and the muscle fibers that it innervates is called the motor unit. After an ANI, the muscle motor unit undergoes profound changes due to death of the motor neurons in the brain or spinal cord that cause paralysis.
If your injury has left you paralyzed, you may feel a desire to move your limbs and use them to be independent. But, depending on your injury, it can take weeks to months before nerves can regrow from the site of injury to the muscle. As more nerves connect with muscle, the muscle gains strength. It can do this in two different ways. First, in a process called hypertrophy, each muscle fiber can grow larger to do the work of two or more fibers that are not innervated. Second, dormant cells in the muscle, called satellite cells, can be stimulated to make a new muscle cell, which is then incorporated into the existing muscle. The nerve itself can promote muscle growth by extending new branches to neighboring motor neurons. This recruits more muscles that lack their own innervation. When a muscle grows bigger, it grows stronger.
Muscle Atrophy
Immobility: Your muscles begin to shrink in size by 0.5 percent per day when you stop using them due to denervation or injury. I was immobile for one-and-a-half months before I could move my legs. By then, I had lost fifteen pounds—10 percent of my body weight. If the loss had been muscle only, that wouldn’t have been so bad, but when muscle atrophies, it’s usually replaced by fat. So I had actually lost 15 to 20 percent of my muscle mass. “Use it or lose it” is especially true when it comes to your muscles, which is why physical therapy carefully exercises your muscles, even when you’re unable to move them voluntarily.
Central nervous system damage: The death of neurons in the brain or spinal cord can cause significant muscle atrophy. Usually, the atrophy is limited to the paralyzed limb, but if you’ve suffered sufficient brain damage, there can be widespread muscle atrophy—in your arms, core, and legs—without paralysis.
Peripheral nervous system damage: There can also be damage to nerves in the peripheral nervous system, outside the spinal cord. When I fell from my bike and hit my head, I put out my right arm to lessen the impact. But I overextended it, and the nerves in that armpit (the brachial plexus) were stretched and damaged. This injury probably contributed to some of the muscle atrophy in my right arm, which is now only 25 percent as strong as my left arm. So it’s important that your doctors look for peripheral nerve damage, which can result from stretching, compression, or direct trauma. Sometimes, it’s possible to stretch, exercise, and massage (using myofascial techniques) the affected limb to release the nerve. In other instances, a surgical repair is necessary.
Strengthening Muscle
To regain your strength and coordination, you may need to combine multiple therapies in a program designed expressly for you. The program may include range-of-motion work, strengthening, functional training, patient and family education, and equipment training. For muscle strengthening, your program may include some or all of the following: good nutrition (increased protein, especially leucine, and sufficient calories), independent physical activity (resistance and weight training and cardiovascular exercise), assisted physical activity using functional electrical stimulation (FES; Figure 26), body weight support systems (including robots and exoskeletons); and drugs such as testosterone and anabolic steroids (androgens such as methandrostenolone, also known as performance-enhancing drugs or PEDs).
Use it or lose it: Activity-based therapies (ABT) have great potential to improve motor function. These activities include locomotor training, FES, and task-specific training. All of these interventions are intended to stimulate the nervous system and optimize functional recovery. Recovery can be via neuroplasticity (reorganization of the nervous system and recruitment of nerve pathways not used routinely) or activity-based programs, which have benefits beyond improved motor function, including improvements in cardiac function, bone density, muscle mass, and glucose metabolism. After walking daily using my platform walker for up to fifteen minutes at a time, I’ve increased the pressure sensation in my feet, lumbar, and thoracic regions.
Much of the work in activity-based programs is performed by walking with assistance: treadmill walking with therapist assistance and body weight support (Figure 27), overground walking with only body weight support (e.g., Hocoma Andago, Figure 28A); robot treadmill walking with body weight support (e.g., Hocoma Lokomat, Figure 28B); and overground walking with exoskeletons, which are a type of robot with balance and body weight support in one unit (e.g., ReWalk exoskeletons Figures 29A & B). Results from a number of studies of ABT have shown improvements in trunk control, endurance, walking speed, balance, and ability to perform activities of daily living. For people with upper-extremity weakness, the use of robots to move and strengthen the upper extremities can be helpful. For a year, I used the BIONIK InMotion robot (see pages 47–48) for one-hour sessions three times a week and increased my upper-extremity strength and coordination significantly.
There are four main ways ABT helps in moving the lower extremities:
1. Functional electrical stimulation (FES; Figure 26) uses electrodes to deliver small voltage shocks to stimulate dormant nerves and artificially cause muscle contraction. It is most commonly configured to enable bicycle pedaling, because it can be done by you alone for periods of time up to one hour.
Figure 26. Functional electrical stimulation (FES)
2. The Lokomat treadmill (Figure 27) uses two therapists who each move one leg in a coordinated manner to stimulate a normal gait. In some people, who are able to perform intensive therapy for several months, paralyzed limbs can recover strength and coordinated movement, so the person may walk independently.1
Figure 27. Treadmill locomotor training
3. Suspension systems, like the Hocoma Andago, or a suspension system plus powered movement like the robotic Hocoma Lokomat (Figure 28), provide weight support and balance; thereby enabling you to practice walking overground and turning.
Figure 28. Locomotion devices: A. Hocoma Andago, and B. Hocoma Lokomat.
Figure 29. Robots: A. ReWalk Personal 6.0 Exoskeleton, and B. ReWalk ReStore Exosuit
4. Robots like the ReWalk Personal (Figure 29A) and the ReWalk ReStore Exosuit (Figure 29B) provide body weight support and balance, in addition to robot-assisted lower extremity movement, which permits independent walking on a treadmill or overground for people who have serious deficits in walking due to motor and/or sensory loss. In the future, I believe that locally implanted epidural electrical stimulators (or eventually transcutaneous electrical stimulators) will enable independent walking by combining the best features of current technology (see chapter 19). Powered exoskeletons use a combination of electric motors, hydraulics, and gyroscopes to enable the wearer to move with more strength and control.
There are several models available, but none of them have become simple enough to put on, take off, and use to become the preferred method for walking. That said, they are excellent devices (but expensive) for strengthening your limbs and core. Further advances in materials for construction and batteries will likely make them more useful in the future. But for now, even the psychological benefits of being able to stand up and walk are tremendous. More on exoskeletons on page 210.
Common Musculoskeletal Overuse Injuries
Upper Limb and Shoulder
Rotator cuff injury: The rotator cuff, tendons that keep the upper arm bone (humerus) in place, is designed to give you the greatest freedom of motion—it’s how you scratch your back, brush your hair, or reach for something above your head. The rotator cuff is not, however, designed for moving heavy objects or repetitive motions. Consequently, any person with ANI is at risk in the long term for damaging their rotator cuff. This occurs most frequently in manual wheelchair users but can occur in anyone who has weakness of the muscles that make up the rotator cuff. For example, my rotator cuff screams “ouch” after I spend an hour using my right arm to control the computer mouse, and when I use it to steer the bike while cycling. It could happen easily when you are carrying a water pitcher, stirring batter while cooking, or reaching up into a cabinet to get a dish or glass.
Pushing a manual wheelchair using your triceps and your rotator cuff places an unnatural burden on them. Over time, the muscles atrophy and the tendons fray, making them susceptible to breakage. The constant wear and tear also lead to inflammation and pain. Fortunately, there are several exercises that will strengthen these muscles. It is helpful to adjust your wheelchair to make pushing as efficient as possible, as is purchasing the lightest chair possible (see page 202). The chair’s setup should position the rear axle as far forward as it can go, and seating should be adjusted to maintain optimal posture.
Learn the early signs of rotator cuff injury so that you can switch (temporarily) from a manual wheelchair to an electric modified third wheel (see page 203) or power wheelchair, and allow your shoulders to rest and heal. Some new wheelchairs have electric motors in the hubs of the wheels that allow you to use them as manual power-driven. If you have shoulder problems and use a manual wheelchair, investigate these chairs so that you have the option to switch to power or electric-assist as needed.
Frozen shoulder: Frozen shoulder happens when the muscles of the shoulder are kept immobile due to paralysis or pain. The muscles shorten, inflammation occurs, and the tissues around the head of your shoulder bone (humerus) become attached by weblike strands of fibrotic tissue that cause extreme stiffness and loss of range of motion (adhesive capsulitis). This process dramatically decreases the shoulder’s range of motion, especially when you try to rotate your arm in and out. The best treatment for frozen shoulder is to prevent it by maintaining movement. Once frozen shoulder occurs, anti-inflammatory drugs in combination with stretching and physical therapy can help improve and restore range of motion.
Hand, Wrist, and Elbow
Carpal tunnel syndrome (CTS): CTS is the most common overuse injury, affecting 40 to 65 percent of wheelchair users. The causes of the repetitive stress are transfers, weight shifts, and pushing the wheelchair. The symptoms are weakness and numbness of the hand, a worsening of symptoms while sleeping, and slight improvement by shaking the wrist.
CTS is diagnosed by electromyography (EMG). Treatment is usually conservative and includes using padded gloves to push your wheelchair, wearing a splint while you sleep at night to stretch the wrist, over-the-counter anti-inflammatory drugs, and, occasionally, steroid injections. If, after three months of these treatments, the pain is still debilitating, you may consider surgery. Surgery is performed under local anesthetic and has high success rates, but the inability to use your hand during the recovery period may be difficult, as you will need more help with your everyday tasks. And you’ll need to use an electric wheelchair while you recover.
Ulnar nerve compression (elbow): Compression of the ulnar nerve (commonly called “hitting your funny bone”) due to entrapment at the elbow is the second most common peripheral nerve problem, affecting 25 to 45 percent of wheelchair users. The symptoms are shooting pain down your forearm and numbness of the little and ring fingers. Treatment is basic: Avoid situations that put pressure on the inner part of your elbow (such as resting your arm on your armrest or table) or keeping your elbow flexed for long periods of time.
Lateral (tennis elbow) and medial (flexor tendonitis) epicondylitis: The bumps on the underside of your elbow are called the epicondyles. Wheelchair users who grip their rims too hard or are not sitting properly may develop lateral epicondylitis (pain and tenderness on the outer side of the elbow). You can also overuse the flexor pronator muscle by extending the wrist too high when pushing your wheelchair, which causes pain on the inner side of the elbow (this is not uncommon when your wrist and finger strength are weak, which is typical of tetraplegics). Treatment for either condition is improving your wheelchair technique, applying an ice pack to the painful area, stretching and strengthening the muscles with physical therapy, steroid injections, and using an electric wheelchair when necessary.
Musculoskeletal Complications
Osteoporosis: Osteoporosis means your bones have lost density, making them weaker and more breakable. There are generally no symptoms; all too often osteoporosis is diagnosed after even a minor fall results in a broken bone. Bone weakening occurs primarily in paralyzed limbs because of lack of use and decreased weight-bearing. Osteoporosis is diagnosed with a bone density scan.
People with ANI have rapid loss of bone density.2 Within two years, 60 percent will have developed osteoporosis; 20 percent will have mild bone density loss (osteopenia), and 20 percent will remain in the normal range. Over a fifteen-year period, 40 percent of people with ANI will have a fracture. Bones in regions of complex regional pain syndrome (CRPS) show increased osteoporosis. For example, the bones in my right forearm, which is where I have CRPS, have lost twice as much bone density as any other bones in my body.
Lifestyle changes are the first step in addressing osteoporosis. Good nutrition with adequate intake of calcium and vitamin D; weight-bearing exercise; smoking cessation; counseling on fall prevention; and avoidance of heavy alcohol use all help you limit bone thinning and fractures. Avoid, if possible, drugs that increase bone loss, such as certain steroids. Weight-bearing therapies, including the use of a standing frame, FES (which only works if maintained for a prolonged period of time), exercise, and whole-body vibration platforms can all help strengthen bone and limit loss of density.
Bisphosphonates are medications that inhibit bone resorption (loss of bone mass) and weakening. They are the most frequently prescribed drugs because of their efficacy, low cost, and safety. In a review of many trials of people with osteoporosis, bisphosphonates reduced the risk of fracture by 40 to 60 percent. Your doctor can discuss the best options for you.
Osteoarthritis (OA): OA is a common condition as we age. It causes joint pain and a subsequent reduction in activities, which leads to a loss of range of motion, causing functional impairment—a domino effect. OA affects both large joints (knee, hip, shoulder) and small joints (fingers and wrist). Consequently, it causes difficulty walking, bending over, reaching overhead, performing tasks with your hands such as opening a jar, knitting, cooking, even opening a letter. The upper extremity, particularly the shoulder joint, is frequently affected by osteoarthritis. OA of the knee, hip, and shoulder is common in all three ANIs because there is frequently an imbalance, created by different sensory and motor abilities on one side of your body. This is particularly common if you use a cane or have use of only one arm and hand, making the limb susceptible to OA from overuse. Treatment of OA should be conservative, starting with therapy to improve range of motion; nonsteroidal anti-inflammatory drugs such as ibuprofen; and exercise of muscles to prevent disuse atrophy.
Osteomyelitis: Most commonly the result of a pressure ulcer that has extended into the underlying bone, osteomyelitis should be considered a non-healing stage IV pressure ulcer. It’s best diagnosed with a bone scan or MRI. Frequently, bone biopsy is needed to identify the bacteria causing it. Treatment is administration of intravenous antibiotics for six to twelve weeks. If healing is still delayed after antibiotics, the bone may need to be removed, especially if there’s evidence of systemic spread of the infection.
Radiculopathy and Myelopathy: Osteoarthritis-associated inflammation can lead to radiculopathy. In a radiculopathy, a nerve is pinched as it exits the spinal cord through a narrowed hole (foramen) in the vertebrae. The most common location is in the neck, especially at the sixth and seventh vertebrae, which is also one of the most common sites for SCI. Over time, bone spurs can further obstruct the foramen. When a radiculopathy occurs months to years after your injury, it can be frightening because your first thought may be that something has “gone wrong” in your brain or spinal cord. The major symptoms are pain and muscle weakness (myelopathy).
Diagnosis is usually made with an X-ray of the neck or a CT scan and electromyography (EMG). EMG measures the speed of the nerve impulse from the brain to the affected muscle. It can determine whether the problem is in the brain or in nerves outside the spinal cord; the latter is much more common. Treatment is conservative, including stretching for range of motion, bed rest, and physical therapy. For pain, nonsteroidal anti-inflammatory drugs are usually prescribed. There is also evidence that chiropractic treatment is helpful, but only for neck pain that is not due to a radiculopathy but is caused by chronic musculoskeletal problems.3 Usually, the pain and weakness resolve after four to eight weeks. If symptoms continue, you may require additional testing with MRI to rule out other causes.
SCI-Specific Musculoskeletal Problems
Post-operative spine degeneration: Many people will require an operation to stabilize their spine. In my case, I had surgery to fuse my vertebrae from C3 to C5. As a result, I have a decreased range of motion for movements such as spinal flexion, extension, and rotation. More important, the fused vertebrae act like a lever and push against the adjacent vertebrae, especially the lower ones (C6 to T1 in my case). This accelerates the normal process of wear and tear that causes degeneration of the disc and erosion of the vertebrae.
Over many years, this can lead to new neurologic deficits and a disease called neuropathic spinal arthropathy. Because this process can worsen pain as well as motor and sensory function, you should have yearly exams to document your muscle strength and sensation. The diagnosis is best made by CT scan, which can show narrowing of vertebral discs and erosion of parts of the vertebrae. Unfortunately, there aren’t any particularly good treatments for neuropathic spinal arthropathy. But physical therapy to strengthen the muscles can be helpful, and so can exercises to increase range of motion. These activities can sometimes worsen pain, in which case immobilizing the neck is recommended using a custom fitted brace. Surgery to fuse damaged vertebrae will likely decrease pain, but this can lead to further damage of your spine by the same arthropathy process.
Heterotopic ossification: Heterotopic ossification is the development of bone deposits in soft (nonskeletal) tissue, primarily around the hip and knee joints. It occurs in many people with SCI and some with TBI. It can develop within days following the injury. In most cases, heterotopic ossification causes no significant physical limitations, but it can limit joint motion, cause swelling, or increase spasticity in the leg. In rare situations, drugs will need to be prescribed and surgery is sometimes necessary.
Loss of muscle mass (sarcopenia): From ages forty to eighty, the average American experiences a 35 percent decrease in total muscle and bone mass. This loss is called sarcopenia and is accompanied by decreased muscle strength. There are many causes, including decreased physical activity due to weakness, chronic pain, and fatigue; loss of muscle innervation, which is necessary to stimulate muscle contraction and promote muscle cell survival, repair, and regeneration; decreased caloric intake (especially protein); vitamin D deficiency; and decreased production of growth hormone and testosterone. Two ways to address the problem, supported by current studies, are: 1) exercise, which has been shown to increase muscle mass when weights are used in the upper extremity and sit-to-stand and gait training are used for the lower extremity4; and 2) adding protein to your diet in the form of fish, certain amino acids (e.g., leucine), and vitamin D for people with confirmed deficiency.5 Speak with a nutritionist for expert advice on the best dietary and supplement options for you.
Everything You Need to Know
Your bone and muscle health are integral to your level of functioning and independent living. Strong muscles and bones are also key to longevity.
After your injury, you may experience significant bone and muscle loss. Work with your doctor and physical therapy team to ensure that you’re doing all you can to maintain and even increase muscle mass and bone density. To the extent that you are able:
• Include weight-bearing exercise at least three times a week as part of your PT.
• Be sure your diet includes enough protein.
• Learn adaptive techniques that will protect you from rotator cuff injury, carpal tunnel syndrome, and other common conditions to which your injury has made you more vulnerable.
• Take advantage of the latest technologies when they can help you, such as robotic-assisted exercise therapy.
• When an injury occurs, start with the most conservative therapeutic approach and leave surgery as a last resort.
In addition to working with your physical therapy team to improve your muscle strength and bone density, investigate local groups of other people with ANI who participate in team sports or workouts such as swimming, bicycling, rowing, and basketball. You’ll benefit from the camaraderie as well as the exercise.