Many of the advances in spinal bracing have developed as a result of our better understanding of spinal biomechanics. Conceptually, the spine can be thought of as a series of semirigid segments interconnected by viscoelastic linkages. Spinal kinematics involves motion in six degrees of freedom, with rotation about three axes and translation along the three coordinates. For clinical considerations, testing (particularly involving normal subjects) has generally been confined to three planes of motion: flexion-extension, axial rotation, and lateral bending.

Evaluation of the efficacy of an orthosis to limit spinal motion can be performed by a variety of methods. Standard radiography, typically utilizing flexion-extension views, has been employed. Cineradiography evaluates motion using fluoroscopy with movie film. Goniometry utilizes external devices attached to the subject to measure spinal motion. Goniometry has been demonstrated to correlate fairly well with radiographic techniques, and avoids exposing subjects to radiation. This advantage, however, is offset by some decreased accuracy and lack of information on motion at any particular segment.

Since bracing attempts to control the position of the spine through the application of external forces, orthotic design must account for regional variations of the surrounding anatomy. These include the vital soft tissue structures of the anterior neck, the rigid thoracic ribcage, and the bony pelvis at the base of the lumbar spine. The surrounding soft tissue envelope has a substantial effect on the ability of an externally applied force to control spinal movement. Pressure measurements on the soft tissues may be an objective way to assess the fit of a spinal orthosis. The role of soft tissue pressure measurement as an index of applied corrective force for the bracing of deformity remains unclear. The intervening soft tissue envelope is also an area of potential complication with problems ranging from skin breakdown, local pain, decreased vital capacity, and increased lower extremity venous pressure.

Along with our improved understanding of the biomechanics of spinal bracing, improvements in the materials available for brace manufacture have led to dramatic advancements in their design. Newer composite materials, polymer resins, and thermoplastics have led to a proliferation of commercially available orthoses that are lightweight and comfortable without sacrificing the stability afforded by the heavier, more cumbersome designs of the past. Advances in computer engineering have also led to innovative methods for customized production of orthotics in a more time-efficient manner. At the authors’ institution, efforts to limit the length of in-patient stays have necessitated a close working relationship between treating clinicians and the orthotists. A computerized database of key measurements that have been recorded over years has allowed our orthotists to develop digitized models of various sizes and body types utilizing computer aided design/computer aided manufacturing (CAD/CAM) technology. Using this approach, simple measurements at the sternal notch, xyphoid, and waist along with linear measurements can be performed and integrated with CAD/CAM technology to rapidly design a precision fit orthosis in a fraction of the time needed for standard
mold-based orthoses. This approach has been studied in the setting of bracing for adolescent idiopathic scoliosis. Braces comparable (in comfort and curve correction) to those made using traditional mold techniques could be produced in approximately one-third of the time previously required. Continuing advancements in this area include the development of handheld three-dimensional laser imagers that utilize reflectors placed on the patient to capture body shape information. This technology has been established in limb applications and spinal applications and is currently evolving.

COs can be divided into two broad categories, soft and hard; hard orthoses are further divided into cervical and cervicothoracic braces. Soft collars provide little immobilization, but are often used in the treatment of whiplash-type injuries, where they may provide comfort and proprioceptive feedback to help “remind” a patient to voluntarily restrict motion. Some practitioners utilize soft cervical collars in the management of cervical myelopathy while others discourage use in this setting.

Rigid cervical and CTOs come in several forms. All forms must be able to accommodate the vital soft tissue structures in the neck while simultaneously providing rigid immobilization of the mobile cervical spine. This is generally accomplished by firm seatings about the base of the skull and upper thorax connected by a rigid column. Most include an anterior opening to accommodate a tracheostomy tube. Examples of COs include the Philadelphia collar (Fig. 40.1), the Miami J collar (Fig. 40.2), and the Aspen CO (Fig. 40.3).

The classic study evaluating the effectiveness of various orthoses in immobilizing the cervical spine was performed by Johnson and colleagues in 1977. The authors evaluated the soft collar, Philadelphia collar, four-poster orthosis, sterno-occipital mandibular immobilizer (SOMI), and a cervicothoracic orthosis. They utilized radiographs and overhead photographs taken at the extremes of motion in flexion-extension, rotation, and
lateral bending. They quantified sagittal plane motion for each brace at every level of the cervical spine. As others had demonstrated, they found that a soft collar offered no restriction of motion in any plane. They found that increasing the length of the orthosis (extending it onto the thorax) and increasing the rigidity of the connection improved the flexion control, but lateral bending and total flexion and extension were less controlled. They also demonstrated increased motion between the occiput and C1 in all the braces compared with the unbraced state. This “snaking” or paradoxical motion has subsequently been described throughout the cervical and thoracolumbar spine.

Askins and Eismont performed a widely referenced study comparing five commonly used COs in terms of their efficacy in restricting cervical motion. Radiographic and goniometer measurements found the NecLoc orthosis to be superior to the Miami J, Philadelphia, Aspen, and Stifneck orthoses in terms of flexion-extension, rotation, and lateral bending. The Miami J collar was also found to be significantly superior to the Philadelphia and Aspen orthoses in extension and combined flexion-extension.

Known complications of COs include skin breakdown over bony prominences such as the occiput, mandible, and sternum. Skin breakdown is especially prevalent in ploytrauma patients with prolonged recumbency and in patients with altered sensorium. One study reported that the Miami J and the Aspen collar produced the lowest chin and occiput pressures. Recently, increased intracranial pressure (ICP) as a consequence of rigid cervical orthotic immobilization has also been described.

In practice, obtaining a proper fit is sometimes difficult given the spectrum of body shapes encountered. However, it is vitally important to obtain a proper fit in order for the brace to be effective and to reduce the potential for paradoxical increased motion at sites adjacent to the spinal injury.

CTOs generally consist of occiput and chin supports attached to anterior and/or posterior thoracic plates. Examples include the SOMI (Fig. 40.4), the Minerva brace (Fig. 40.5), and the Yale brace (Fig. 40.6). Compared with COs, these devices improve control in all planes of motion. This improved rigidity, however, comes at the expense of patient comfort. Some early research distinguished between the two/four poster designs and those with more extensive connections between the head and thoracic components. The more recent, standardized classification system, however, categorizes the poster braces as CTOs along with the other designs. The traditional four poster brace was shown to limit 79% of overall
cervical flexion-extension, and limit midcervical flexion to a comparable degree as the more rigid CTOs. Due to their heavy design and high resting pressures on the chin and occiput, this brace is less commonly used today.

The SOMI (Fig. 40.4) utilizes metal uprights to connect occipital and mandibular rests to a sternal plate that is secured to the thorax by padded metal “over-the-shoulder” straps and additional circumferential straps that cross in the back. Since there is no posterior thoracic plate, the occipital rests are support by uprights from the sternal piece. This results in adequate control of flexion but deficient control of extension throughout the cervical spine. These braces are generally associated with fair patient comfort but also do demonstrate high resting pressures at the chin and occiput.

The thermoplastic Minerva body jacket (TMBJ) has a lightweight, bivalved, Polyform shell that allows improved patient comfort and hygiene and interferes less with follow-up radiographs. Donning this brace is somewhat complex, often requiring an orthotist for proper application. More recently a prefabricated version of the Minerva body jacket has been developed, the Minerva CTO (Fig 40.5). Its design features a forehead band attached to a large occipital flare. Sharpe and
colleagues demonstrated that this orthosis limits overall sagittal plane motion by 79%, axial rotation by 88%, and lateral bending by 51%.

The Yale brace (Fig. 40.6) was originally designed as a modified Philadelphia collar with custom molded anterior and posterior polypropylene thoracic extensions. The modern version is prefabricated. While lighter and less cumbersome than most of the other CTO’s, the Yale brace has similar efficacy in controlling motion. The Yale brace is reported to restrict 87% of overall flexion-extension, 75% of axial rotation, and 61% of lateral bending. While the CTOs have been shown to be fairly effective at limiting motion of the cervical spine, they should not be expected to rigidly immobilize below the C7–T1 level despite their thoracic components. In the author’s experience, use of CTOs in the bedbound patient is extremely problematic as the tendency for cephalad migration of the brace in the semirecumbent position increases the likelihood of pressure sore on the chin or occiput.

It is widely felt that the halo vest provides the most rigid immobilization of the cervical spine of all the currently used orthoses. Originally inspired by a device used by Frank Bloom to treat facial fractures in pilots with overlying burns during World War II, modified versions were used by Nickel and Perry to immobilize patients with polio who had undergone posterior cervical fusion. The early halo devices consisted of a circumferential stainless steel ring with four pins for skull fixation. The ring was attached to a plaster jacket by upright posts. Numerous improvements have been made to the various components of the halo vest, but the overall design principles remain the same. A ring is fixed to the skull with multiple pins. The ring is then attached to a vest by four connecting rods (Fig. 40.7). Newer rings are made of composite materials, which have the beneficial properties of light weight, radiolucency, and compatibility with magnetic resonance imaging. There does not appear to be a difference in fixation strength between newer radiolucent graphite rings and the early titanium ones. Recently, rings that are open posteriorly or have crown-type designs have been developed. These designs allow for ease in placement since the head of the patient does not need to be passed through the ring. Additionally, since the patient is not lying on the back of the ring, there is less risk of cervical spine fracture displacement through ring manipulation.