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The TriaCII orthosis for treatment of adolescent idiopathic scoliosis (AIS) from Boston Brace International, Avon, Massachusetts, is a dynamic tension-based orthosis in which the forces acting on the spine are able to move with the patient, rather than being static, as with conventional bracing, explains James "Jim" Wynne, CPO, Boston Brace director of Education and Training. "The whole premise of tension-based dynamic bracing is that you have a lower force that moves with the patient," Wynne continues. "Thus those forces are in constant contact with the patient, so we maximize the time over which the force acts. It is a custom-fitted orthosis that consists of two parts: lumbar and thoracic. The lumbar part does not restrict lumbar motion; it maintains the motion segment. The thoracic part consists of tension springs that are adjusted to patient tolerance. A unique coupling mechanism allows the two parts to move with each other."
The TriaC was developed jointly by the University Hospital of Groningen and the University of Twente in the Netherlands. An article in Medical Engineering & Physics, April 2002, with an abstract at PubMed ( www.pubmed.gov ), by A.G. Veldhuizen, J. Cheung, G.J. Bulthuis, and G. Nijenbanning of the University Hospital of Groningen describe the TriaC as follows: "A transverse force system, consisting of an anterior progression force counteracted by a posterior force and torque, acts on the vertebrae of a scoliotic spine. The aim of the newly introduced TriaC brace is to reverse this transverse force pattern by externally applied and constantly present orthotic forces. In the frontal plane the force system in the TriaC brace is in accordance with the force system of the conventional braces. However, in the sagittal plane the force system acts only in the thoracic region. As a result, there is no pelvic tilt, and it provides flexibility without affecting the correction forces during body motion. In the current preliminary study it is demonstrated that the brace prevents further progression of the Cobb angle and axial rotation in idiopathic scoliosis. The new brace has the added advantage of comfort for the wearer, and it offers a better cosmetic appearance, as well as, potentially, a better compliance."
Stopping Progression, Achieving Stability
"The aim is not so much to maximally reduce the Cobb angle, but rather to achieve a stable, well balanced spine into adulthood," Wynne says. "How we get to that point, and how much correction is needed is somewhat variable."
Wynne continues, "What the TriaCII studies are showing is that a minimum of 20-percent in brace reduction of the Cobb angle is necessary for success." Although often patients, once they are no longer being braced, often return to the curve degree they had before orthotic treatment, without that treatment, the progression of the curve might have gone much further. For instance, if a 35-degree curve is corrected to 20 degrees with bracing, and later returns to around 35 degrees, without the orthotic treatment, the curve might have progressed into the 45-50-degree range in which surgery may be considered necessary. Thus the goal of avoiding surgery has been achieved.
Studies are finding that in many cases, the correction obtained with the TriaC is being maintained for four to six years after patients are weaned from the brace, Wynne says. "With conventional bracing, the general tendency has been for patients to go back to where they were before bracing."
John Michael, MEd, CPO, FAAOP, in a "John Michael's Corner" article, comments on the TriaC: "The TriaC is custom-fitted from a kit of prefabricated bars and straps... [T]he TriaC is based on a series of three-point pressure systems that correspond to those exerted by the Boston/Milwaukee orthoses. This orthosis also seems easy to don and doff and less constricting than most body jacket styles."
Indications for Use
Indications for using a TriaCII orthosis are, according to Boston Brace:
- The patient has an idiopathic scoliosis with a Cobb angle of between 15 and 35 degrees.
- The thoracic apex of the primary or secondary curve is between TH7 and TH11.
- The patient is skeletally immature. According to international guidelines this means Risser 0-2, pre-menarche or post-menarche less than one year.
- The patient has a flexible spine.
- The patient's posture is "normal."
- The patient is motivated to wear the orthosis.
- As the patient is not an adult, the parent's consent to him/her wearing the orthosis is needed.
Hypothesis on AIS Etiology
The dynamic tension bracing action of the TriaC aims to help direct the growth of the spine, rather than reacting to the growth of the spine, as is the case of conventional bracing, Wynne explains. The concept behind the TriaC is based on the hypothesis that in progressive scoliosis, vertebral body wedging during adolescent growth results from asymmetric muscular loading in a "vicious cycle" (vicious cycle hypothesis of pathogenesis) by affecting vertebral body growth plates (endplate physes).
An illuminating and interesting discussion on this theory can be found online in an electronic focus group (EFG) conducted by the International Federated Body on Scoliosis Etiology (IBSE) at www.scoliosisjournal.com/content/1/1/16
The text for the debate was written by Ian A.F. Stokes, PhD, who has done research on the subject, and includes comments by various experts as they weigh in on the debate.
The site notes, "A frontal plane mathematical simulation tested whether the calculated loading asymmetry created by muscles in a scoliotic spine could explain the observed rate of scoliosis increase by measuring the vertebral growth modulation by altered compression. The model deals only with vertebral (not disc) wedging. It assumes that a pre-existing scoliosis curve initiates the mechanically modulated alteration of vertebral body growth that in turn causes worsening of the scoliosis, while everything else is anatomically and physiologically normal.' The results provide quantitative data consistent with the vicious cycle' hypothesis. Dr. Stokes' biomechanical research engenders controversy. A new speculative concept is proposed of vertebral symphyseal dysplasia with implications for Dr. Stokes' research and the etiology of AIS.
"What is not controversial is the need to test this hypothesis using additional factors in his current model and in three-dimensional quantitative models that incorporate intervertebral discs and simulate thoracic as well as lumbar scoliosis. The growth modulation process in the vertebral body can be viewed as one type of the biologic phenomenon of mechanotransduction. In certain connective tissues this involves the effects of mechanical strain on chondrocytic metabolism a possible target for novel therapeutic intervention."
The TriaC has produced positive results for many patients, and, according to Boston Brace, "With the open design, lightweight construction, and the freedom of movement, patients will enjoy a more comfortable quality of life throughout their treatment process."
