9 The Patient with Spinal Cord Injury: Surgical Considerations
Abstract
The incidence of the development of scoliosis in young patients with spinal cord injury (SCI) is essentially 100% if they are injured before the age of 10 years and 67% if they are injured prior to skeletal maturity. Patients with scoliosis secondary to SCI can benefit from different strategies such as prophylactic bracing, especially if started immediately following the injury, as this has been shown to delay or even eliminate the need for spinal fusion. Aligning the spine during a fusion in a sitting posture with a level pelvis and proper sagittal alignment to maximize the patient’s independence and function as well as reduce the potential for decubitus ulcerations is critical. Relatively early fusion to minimize the surgical complication risks should also be considered. Failure to recognize the compensatory movement patterns that the patient with SCI may be utilizing prior to a spinal fusion may result in unanticipated postoperative challenges in management. A comprehensive team approach with physical/occupational therapy, wheelchair specialists, orthotists, rehabilitation medicine physicians, and orthopaedic surgeons is therefore highly recommended to provide optimal global care for this patient population. When a surgical treatment is recommended by the team, patients with scoliosis secondary to SCI can continue to lead full and active lives after spinal fusion.
9.1 Etiology
Spinal deformity as a result of spinal cord injury (SCI) most commonly affects children and adolescents, but may also impact adults. The coronal and/or sagittal plane deformity typically develops secondary to muscle weakness and/or imbalance. The development of progressive kyphosis alone can also present as a residual deformity following a fracture or iatrogenic injury secondary to a laminectomy possibly performed at the time of initial surgical decompression/stabilization. 1
9.2 Prevalence
The prevalence of scoliosis in SCI is quite high, especially when an injury occurs in a younger patient. Lancourt et al 2 reported that the prevalence of scoliosis was 100% in patients with SCI under the age of 10 years, 19% in patients from 11 to 16 years, and 12% in patients over 16 years of age. Dearolf et al 3 found that the risk of surgery for spinal deformity resulting from SCI was 67% if the injury occurred prior to maturity. Mulcahey et al 4 reported that children injured before the age of 12 years were 3.7 times more likely to require a spinal fusion as compared to those injured after the age of 12 years in a study of 217 children with SCI.
A multitude of problems can be incurred as a result of spinal deformity in a patient with SCI. Most notably, the spinal deformity may lead to significant pelvic obliquity that results in poor sitting balance; this puts the patient at risk for pressure ulcerations from asymmetrical sitting and increased unilateral ischial weight bearing. Further, poor sitting ability can inhibit upper extremity function and lead to difficulties with fitting and using lower extremity orthotics. It has been shown that gastrointestinal dysfunction can result from severe pelvic obliquity, while a patient’s cardiopulmonary status can be negatively impacted when the spinal deformity progresses above 80 to 90 degrees (Fig. 9‑1 a, b).
9.3 Management
9.3.1 Nonoperative
Bracing
Historically, the timing and efficacy of bracing for paralytic scoliosis has been debated. The standard bracing protocols for idiopathic scoliosis were often followed for patients with SCI, and bracing was initiated only after the curves progressed to greater than 25 degrees in growing children. However, more recently, Mehta et al 5 evaluated a more aggressive bracing regimen at Shriners Hospitals for Children—Philadelphia. The study demonstrated a significant reduction in the need for surgery when brace treatment was initiated on curves less than 20 degrees. There was a trend toward a reduction in the need for surgery if bracing was started when the curves measured 21 to 40 degrees, although this was not statistically significant (p = 0.08). There was minimal to no effect on risk of surgery when bracing was initiated on curves greater than 40 degrees. The timing of surgery was also evaluated in the study and demonstrated similar trends with regard to earlier bracing. There was a significantly prolonged delay in the need for surgery of over 4 years when patients were braced with a curve measuring less than 10 degrees. A 3-year delay was noted when bracing was initiated for curves between 11 and 20 degrees. Finally, only a 1-year delay in surgery was identified when bracing was started for curves between 21 and 40 degrees.
Compliance with brace wear can be a challenge with any pediatric patient. 6 However, this hurdle is increased for children with preexisting functional limitations secondary to SCI. A study of pediatric patients with SCI demonstrated a 28% reduction in the reachable workspace when the children were wearing a thoracolumbosacral orthosis (TLSO). 7 These potential limitations in upper extremity range of motion can compromise a patient’s independence and may hinder their compliance. Preliminary studies performed at the author’s institution have unfortunately been underpowered to provide sufficient evidence on brace wear compliance in this patient population. However, given that approximately two-thirds of all patients who sustain an SCI prior to maturity will require a spinal fusion, the practitioner must aggressively pursue and encourage nonoperative management to potentially diminish and/or delay this unacceptably high risk of surgery.
Wheelchair Modification
Additional and/or alternative options do exist that attempt to prevent or delay the progression of spinal deformity. Lateral supports on a wheelchair may or may not affect curve progression but can be useful to improve sitting balance and allow use of the arms. The patient’s wheelchair should be intermittently pressure mapped to identify areas of increased dependence due to pelvic obliquity. Variations can be made in seating materials and custom molding to attempt to reduce the development of pressure ulcerations.
Lower Extremity Orthotics
Ambulation for patients with incomplete SCI should be encouraged if motor strength allows. While not specifically evaluated in the pediatric SCI population, it has been shown that maintaining some upright mobility can diminish the risk for significant curve development and progression in patients with Duchenne’s muscular dystrophy. 8 , 9 The spinal orthosis can be utilized as the pelvic portion of a hip–knee–ankle–foot orthosis (HKAFO). Alternatively, the pelvic portion of the HKAFO can be modified to fit over the spinal orthosis to allow concomitant wear of both braces.
9.3.2 Surgical
Indications for Surgery
Surgical intervention is recommended for progressive spinal deformity secondary to SCI when the curvatures progress to greater than 40 degrees in a growing child and/or significant functional limitations are encountered related to the deformity. The nature of the procedure is contingent on the patient’s age and skeletal maturity. Typically, standard spinal fusions can be performed on children older than 10 years of age, whereas specialized instrumentation allowing for continued spine and chest wall growth is considered for patients younger than 10 years who have significant deformities.
The threshold curve magnitude of greater than 40 degrees for surgical intervention in skeletally immature patients was derived in part from the study of patients with spina bifida. Müller et al 10 reported an average progression of 13 degrees per year once the curve exceeded 40 degrees in patients with spina bifida. Complication rates have also been reported to be significantly higher for surgical intervention with larger spinal deformities (>70 degrees). 11 Despite this, for some younger patients with flexible curves, surgical intervention may be delayed beyond 40 degrees in hopes of reaching enough growth to warrant a definitive fusion, avoiding the challenges of “growth friendly” systems.
Spinal fusion may also be considered for scoliosis in a skeletally mature patient with SCI if the deformity leads to significant functional limitations. Poor sitting balance can result in pressure ulcerations on the dependent buttocks and hip. Further, sitting imbalance can restrict the maximal capacity of the patient’s upper extremities if the leaning requires an arm for stabilization. Lastly, cardiopulmonary function has also been shown to be negatively impacted by severe spinal deformity. There are no objective studies of the indications for recommending spinal fusion to mature patients with SCI.
Growing Instrumentation
Standard spinal fusion is typically avoided in patients under the age of 10 years, as significant spinal height and chest wall growth remain in this age group. Two posterior distraction–based options for progressive curves in this age group are growing rods and the vertical expandable prosthetic titanium rib (VEPTR), each of which can be lengthened at regular intervals during a child’s growth. The growing rods are connected to the spine at the proximal and distal aspects of the construct with hooks and/or pedicle screws. The VEPTR differs in part from growing rods in that its proximal fixation point is laterally on the rib rather than on the spine. These systems have rods/connectors, which allow progressive lengthening at regular intervals, typically every 6 months, to keep up with the patient’s spinal growth. Externally driven, magnetically controlled growing rods and growth guidance rod systems are also an option for those with early onset scoliosis. Anterior vertebral growth modulation with a tethering implant may also be considered for some in the juvenile age group.
However, there are no studies to date that specifically evaluate the use of growing systems in patients with SCI. Unfortunately, these constructs carry a significantly high complication rate of 25 to 72% in the able-bodied population. 12 , 13 , 14 In the authors’ experience, this risk is much higher in the SCI population. Children with SCI are already prone to urinary tract and respiratory infections. This risk is increased with the need for surgical lengthening procedures of the growing instrumentation every 6 months. Typically, most patients with growing systems will eventually undergo a spinal fusion.