Points of Consensus: Idiopathic Scoliosis

Thomas M. Gavin, CO

ETIOLOGY

The etiology of IS remains unknown today, but current research suggests its cause is multifactorial. We recognize IS to be an extremely complex disorder, in which multiple factors may come into play, making curve progression in any given individual difficult to predict. In fact, the variability observed in factors such as curve patterns, curve flexibility, and age of onset suggests the "multifactorial" nature of IS is so pronounced that it may be more useful to think of IS as encompassing two or more distinct etiologies. Our inability to identify the distinct etiology a patient may be presenting with makes curve progression in any given individual, and thus the likelihood of successful orthotic treatment, difficult to predict. It is important for the treating orthotist to have a general understanding of the various factors thought to be associated with the condition. There currently is no evidence in the literature that suggests the development of IS can be prevented in one who is otherwise predisposed to have a progressive curve before treatment. Thus, the orthotist should be knowledgeable enough to quell caregiver or patient concerns about the possibility of the scoliosis being preventable, such as by the avoidance of heavy school backpacks or poor posture.

For the purpose of communicating with peers and other health care professionals, the treating orthotist should understand the differences among infantile, juvenile, and adolescent onset IS, and that these should not be confused with congenital scoliosis.

GOALS FOR ORTHOTIC TREATMENT

The goal of using an orthosis in the treatment of IS is to stop curve progression and minimize negative cosmetic consequences, thus preventing the need for surgical stabilization of a curve. In some instances in which surgery is anticipated, an orthosis may be beneficial to the patient by postponing the surgical stabilization.

The orthotist should appreciate the three-dimensional aspects of scoliotic spine deformity. For instance, one should recognize the propensity for thoracic scoliosis to be hypokyphotic, unless proven otherwise. The ability to envision and understand the three-plane deformities that may exist with scoliosis should influence the appropriate application of corrective forces for satisfactory in-orthosis correction.

KEY POINTS FOR UNDERSTANDING RISK OF PROGRESSION

THE RELATIONSHIP OF GENDER AND CURVE PROGRESSION

The incidence of scoliosis with smaller curves that do not require treatment beyond observation is similar between boys and girls. Progression of small curves to a size requiring treatment is more prevalent in girls than boys by a factor of approximately 7 to 1.

THE RELATIONSHIP OF CURVE SIZE AND MATURITY WITH CURVE PROGRESSION

In general, the younger the child and the larger the curve, the greater the risk for curve progression. However, other factors such as curve pattern can contribute to the risk for curve progression. In any individual patient, a worsening of the condition can be thought of as a race between curve progression and maturation of the growth process. In general, the cessation of spinal growth should naturally halt the progression of a scoliotic curve that is less than approximately 50° in size. There are two primary reasons the orthotist and other key health care providers should understand the risks for curve progression: 1) To communicate accurate information with the patient and caregivers regarding the strategy and timing of orthotic treatment; and 2) To enable a critical review of the literature because not all publications include patients of equal risk for curve progression.

STATEMENT OF EFFICACY OF ORTHOTIC TREATMENT

Orthoses can be efficacious in the treatment of IS, and their use is the only nonsurgical treatment method shown to positively alter the natural history of the disease. Although there are limitations in the current literature investigating the true etiology and natural history of the condition, there is strong evidence that orthotic treatment can prevent curve progression in most of those who would otherwise experience curve progression if left untreated.

RESEARCH PRIORITIES

More research is needed to identify which patients, at a younger age, with diagnoses of IS are more likely to demonstrate significant curve progression. Having this ability can potentially justify earlier intervention of orthotic treatment, which should increase the likelihood of a successful outcome while not simultaneously "overtreating" the patient population.
More research is needed to identify which patients have a more "malignant" etiology (or combination of factors) that may respond poorly to orthotic treatment.

CRITERIA FOR ORTHOSIS PRESCRIPTION

RESEARCH PRIORITY

More investigation is needed to understand orthotic design alternatives and the effectiveness of orthotically treating curves with apices cephalad to T7.

CRITERIA FOR ORTHOSIS USE

DISCONTINUATION DISCONTINUING TREATMENT BECAUSE OF MATURITY

Because girls typically reach skeletal maturity at a younger chronological age than do boys, a criteria for orthosis discontinuation will differ depending on patient gender. That said, multiple factors can be considered in assessing maturity, so only general guidelines are possible.

Girls should ideally be at least of Risser 4 maturity, 18 months to 2 years beyond menarchal, and/or with clear cessation of significant growth (as measured by consecutive height measurements using consistent techniques throughout the duration). Curve size and location should help influence the timing of this decision (ie, larger, more unbalanced curves may benefit from a more delayed discontinuation because of maturity).For boys, the primary adolescent growth spurt is later in life, so their risk for curve progression extends to an older chronological age. Extenuating factors like those referenced for girls (curve size and location) also exist for boys, but boys are believed to be served by an orthosis to Risser 4, preferably Risser 5, with greater emphasis being given to a documented significant decrease in growth velocity.

DISCONTINUING TREATMENT BECAUSE OF CURVE PROGRESSION OR OTHER FACTORS

Once an orthosis has been prescribed to prevent curve progression in adolescent IS, it is important to continue orthotic treatment until either skeletal maturity is achieved or the clinic team agrees the treatment is ineffective or no longer necessary because of maturity. The amount of in-orthosis correction, the patient's perceived ability to wear the orthosis, and evidence of curve progression are important factors during the consideration of discontinuation of orthosis use in an otherwise immature patient.

With respect to discontinuing orthotic treatment because of curve progression, we concur with the SRS's position, which states: "Surgery for IS is suggested when curve magnitude is 50° or more in either the previously untreated patient or in one who fails orthotic treatment. Surgery is undertaken with two goals in mind. The primary one is to prevent spine deformity progression and the secondary one is to diminish spinal deformity. The natural history of IS during adulthood is one of continued progression if the curves tend to be more than 50° at the end of growth." Thus, although 45° is considered the upper limit of orthotic efficacy, there can be exceptions to treating some with curves of 50° or higher; namely for those with infantile or juvenile scoliosis, for which there can be an advantage of slowing curve progression during periods of significant growth in an effort to delay the need for surgical stabilization. This is in recognition of the "crankshaft phenomenon," for which it is sometimes necessary for an orthopedist to surgically fuse the anterior spine in addition to the posterior when a significant amount of remaining growth is expected. Using an orthosis to delay or slow curve progression in a young child may postpone the need for surgical stabilization to the extent that only a posterior fusion is required. This can yield significant benefits to the patient.

"Weaning" from an orthosis, defined as recommending a period during which the patient can decrease the amount of time spent in the orthosis, may be beneficial to the patient in two distinct ways: 1) Long-term weaning (last 6 months of wear) can be considered as a treatment modality in response to risk for curve progression. For example, an adolescent who is thought to be approaching skeletal maturity and whose curve appears stable, but whose level of maturity is not to the degree that would justify complete orthosis discontinuation would be a candidate for long-term weaning; 2) Short-term weaning may serve as a way to minimize the risk for back pain when an orthosis is no longer necessary to prevent curve progression because of skeletal maturity. For example, once orthotic treatment is deemed unnecessary because of maturity, a patient may serially decrease the amount of time an orthosis is worn on a daily basis during a period of 1 to 4 weeks.

RESEARCH PRIORITY

There needs to be a better understanding of the optimal time to discontinue the use of an orthosis in the treatment of adolescent IS so as to assure a positive outcome with long-term follow-up.