Upper Limb Orthoses for Persons With Spinal Cord Injuries and Brachial Plexus Injuries

Epidemiology

An estimated 276,000 people in the United States live with a spinal cord injury (SCI), which translates into approximately 12,500 new cases per year. Most new injuries involve males (80%); vehicular crashes and falls are the most common causes of SCI, representing 38% and 30% of injuries, respectively. The most common subgroup is tetraplegia; 59% of individuals with an SCI have tetraplegia, and 41% have paraplegia. The neurologic injury level and the completeness of injury are important prognostic markers for recovery and for determining future equipment and orthotic needs.

Pathophysiology

The spinal cord is the major conduit through which motor, sensory, and autonomic information travels between the brain and the body. Pairs of spinal nerves enter and exit throughout the length of the spinal cord and are named based on the vertebral level they originate from. Eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal nerves make up the 31 spinal nerves on each side. Nerve roots that exit and enter the spinal cord excite groups of muscle cells, or myotomes, and receive sensory information from skin areas, or dermatomes. Nerve roots are numbered according to the vertebral level they exit and enter. For example, nerve roots that exit the spinal cord at the fifth cervical vertebra excite C5-innervated muscles. An SCI interrupts the conduction of both efferent and afferent signals, resulting in varying degrees of sensorimotor loss and functional deficit. It is important to understand that the level of vertebral injury does not always correlate with the neurologic level of injury. For example, the spinal cord in adults usually terminates at either the L1 or L2 vertebra. Vertebral fracture or disk herniation involving the lower lumbar or sacral levels would likely involve injury to the lumbosacral spinal nerves and not the spinal cord proper, as in cauda equina syndrome.

The cervical spinal cord is encased within seven cervical vertebrae. At the first and second levels, the diameter of the spinal cord is small in relation to the size of the spinal canal. The cord occupies only one third of the canal at C1–2, but it occupies half of the canal at C7. Because range of motion (ROM) is greatest at the C5, C6, and C7 vertebrae, and because of the relationship between canal size and cord size in the lower cervical region, most injuries occur at those levels.

Traumatic SCI generally results in disruption of the spinal cord architecture, followed by a complex pattern of pathophysiologic processes that exacerbate the injury. Although they may be classified as functionally complete, most traumatic injuries do not result in complete disruption of the cord. Residual effects are often characterized by a peripheral rim of intact tissue with a central cystic cavity. At the level of injury, injuries to white matter and gray matter result in a combination of central and peripheral injuries. Damage to the white matter affects motor control and sensory input from the periphery to the brain below the level of injury. In addition, at and surrounding the injury level, evidence can be seen of lower motor neuron (LMN) injury resulting in flaccid paralysis at the level of injury. Muscles with LMN injury are also at risk for contractures as a result of shortening and scarring and are not amenable to functional electrical stimulation (FES). Coulet et al. have detailed the implications of SCI pathophysiology on upper extremity rehabilitation.

Classification of Spinal Cord Injuries

As described by Bryden et al. and Landi et al., thorough evaluation of the upper limb is the foundation to successful treatment of SCIs. The International Standards for Neurological Classification in Spinal Cord Injury (The Standards) remain the most widely used assessment of motor and sensory impairment after SCI. The muscle strength of 20 muscles (five in the upper limb and five in the lower limb on each side) is graded on an ordinal scale ranging from 0 (absent strength) to 5 (normal strength). Sensory testing to pinprick and light touch also is conducted, yielding a possible score of 56 for each sensation for each side of the body (112 total points for pinprick and 112 total points for light touch). From the motor and sensory examination, the neurologic level and level of impairment are determined. The American Spinal Injury Association (ASIA) Impairment Scale (AIS) grades the level of impairment from A (complete) to E (normal). The Standards define neurologic level as the most caudal segment where normal sensory function and antigravity strength exist on both sides of the body; normal motor and sensory function exist rostral to that level.

In addition, there are clinical presentations of SCI that are described in terms of incomplete syndromes. Central cord syndrome classically presents with upper extremity weakness that is greater than lower extremity weakness. Brown-Séquard syndrome classically presents as a hemicord lesion that leads to loss of pain and temperature sensation contralateral to the lesion and proprioception, vibration, and motor loss ipsilateral to the lesion. Cauda equina syndrome is commonly grouped into discussions of SCI; however, it does not involve the spinal cord. It is caused by injury to the lumbosacral nerve roots that leads to flaccid weakness, saddle anesthesia, and bowel and bladder incontinence. Conus medullaris syndrome is similar to cauda equina syndrome in that it may involve the lumbosacral nerve roots, but it also involves injury to the caudal portion of the spinal cord itself and can present a clinical picture of mixed upper and lower motor neuron injury. Teaching and reference tools are available from ASIA in Atlanta, GA.

Historical Perspective

Orthotic Intervention

Despite the dramatic progress in medicine, rehabilitation, and societal modifications, the upper limb remains obliged to assume new and demanding roles after SCI. After the introduction of antibiotics, high mortality rates among persons with tetraplegia declined, and early rehabilitation techniques focused on purposeful tightening of the finger flexor muscles to develop force between the thumb and the index and middle fingers ( Fig. 14.1 ). Typically referred to as natural tenodesis, tenodesis action, passive tenodesis, and tenodesis hand, this pinch, which provides sufficient force to acquire light objects, formed the basis for the wrist-driven flexor hinge splint and the early techniques for surgical augmentation of the C6 hand. For individuals with active wrist extension, enough force for a functional pinch can emerge even when no active finger–thumb strength exists, but more complex upper extremity tasks may require additional orthoses or adaptive equipment to accomplish. Advanced surgical reconstruction techniques, tendon transfers, and nerve grafts along with technologic advancements continue to provide additional opportunities for improved independence, efficiency, and cosmesis.

Early work with patients with poliomyelitis paved the way for orthotic treatment guidelines in tetraplegia. Whether powered by external sources or voluntary wrist extension, the wrist-flexor hinged orthosis ( Fig. 14.2 ) has been a mainstay of orthotic prescription in tetraplegia rehabilitation. Nickle's wrist-driven flexor hinged orthosis was commonly referred to as the “Rancho Splint” or “wrist-driven flexor hinge splint.” For persons without wrist extension, cable-driven and gas-powered sources were used to activate the pinch. However, despite rejection of the externally powered flexor hinge splint by persons with higher cervical injuries, a variety of wrist-driven orthoses remain on the market for those with midcervical injuries. These wrist-driven orthoses are considered the standard of care for persons with midcervical tetraplegia for restoring function for simple activities of daily living (ADLs) ( Fig. 14.3 ).

Evaluation of the Upper Limb

The Consortium for Spinal Cord Medicine has published clinical practice guidelines for upper limb function after SCI and on outcomes after traumatic SCI ; both provide important upper extremity treatment guidelines for tetraplegic rehabilitation. Based on injury level and completeness of injury, anticipated functional abilities as well as adaptive equipment and orthotic needs can be anticipated, and this information can make the rehabilitation process and discharge planning more efficient. Readers are encouraged to review the practice guidelines for a complete list of recommendations for equipment.

Although The Standards' motor and sensory examinations are internationally applied, they provide insufficient information for the design of upper extremity treatment paradigms. As an adjunct, the International Classification for Surgery of the Hand in Tetraplegia (ICSHT) is recommended when planning for upper limb surgery. As shown in Table 14.1 , the ICSHT is a simple assessment of every muscle in the upper limb below the shoulder. Despite several shortcomings, the ICSHT provides a foundation for decision-making about upper limb interventions and augments the motor and sensory information gained from The Standards.

In addition to the motor and sensory systems, examination of joint range-of-motion (ROM) is essential, because limitations in these areas will greatly impede the application of orthoses, neuroprostheses, and tendon transfers. Spasticity, muscle atrophy, and scarring contribute to poor posturing and potentially fixed deformities. Electrodiagnostic testing in SCI has been popularized by the clinical deployment of neuroprostheses because of the need for intact LMNs for viable electrostimulation. For patients with motor levels appropriate for a neuroprosthesis, formal testing of the muscles' responses is recommended.

The Capabilities of the Upper Extremity (CUE) and the Grasp and Release Test (GRT) are two tools for evaluating hand function. The CUE is a 17-item questionnaire that asks patients to rate their ability to perform functional tasks with their arms on a seven-point ordinal scale. The questionnaire separates proximal arm function from hand function and has been shown to be effective in measuring outcomes after surgery to improve upper extremity function. The GRT, designed specifically for tetraplegia assessment, measures three variables: pinch strength, grasp strength, and hand function. Stroh-Wuolle et al. first reported on the psychometrics of the GRT, which were further established by Mulcahey et al. Clinically, the GRT has been an effective outcome measure for intervention studies of FES and tendon transfers. Despite limitations, The Functional Independence Measure continues to be widely used in rehabilitation centers. Activity and participation have become important components in the overall assessment of upper extremity interventions in SCI and can be evaluated with the Craig Handicap and Reporting Technique (CHART), Canadian Occupational Performance Measure (COPM), and Craig Hospital Inventory of Environmental Factors (CHIEF). Various publications have discussed issues related to upper extremity outcome instruments for persons with tetraplegia.

Upper Limb Orthotic Management