Spinal Balance and In-Orthosis Correction

I n-orthosis correction is typically looked upon as how much correction to the Cobb angle is achieved, but the practitioner must also look at overall spinal balance in relation to the central sacral line to determine the direction and application of forces. For instance, a decreased Cobb angle with a marked asymmetrical balance in relation to trunk shift and decompensation is unacceptable. As evidenced in Figure 1, both spinal balance and Cobb angle have been greatly improved. If there was good Cobb angle correction but poor spinal balance in the coronal plane, then the correction would be unacceptable. It is important to also pay particular attention to the sagittal plane when decreasing Cobb angle in-orthosis to prevent increasing hypokyphosis. A marked decrease in sagittal kyphosis should not be sacrificed for in-orthosis Cobb measurements. Research is limited on spinal balance and decompensation. In 1998, Raso et al. reported that little research has been done on trunk distortion. They proposed that the best treatment would improve both spine alignment and body deformity, not simply relying on the single-plane measurements of the Cobb angle. Watts also noted the small amount of research and uncertainty concerning the topic of spinal balance, while emphasizing the desired position of the wellcompensated spine and reduction of trunk shift. Rudicel and Renshaw studied decompensation because of the concern that spinal decompensation can lead to back pain in adult life. They defined decompensation as the horizontal distance between two vertical lines, one bisecting the sacrum and the other bisecting the highest vertebra seen on a standing anterior-posterior roentgenogram. Figure 2 shows this relationship radiographically. Among 22 female compliant patients treated with the cervicothoracic-lumbosacral orthosis in Rudicel and Renshaw’s study, there was no predictable improvement in decompensation in thoracolumbar and lumbar curves. However, it should be noted that half of their patients showed some mild improvement in decompensation. Mellencamp et al. reported that improvement of scoliosis with compensation could be a response expected from cervicothoracic-lumbosacral orthosis treatment. Winter and Carlson emphasized the importance of using the neck ring on the cervicothoracic-lumbosacral orthosis to align the patient’s head over the pelvis and recognized that some patients with the thoracolumbar spinal orthosis (TLSO) had sufficient righting reflexes to bring their upper spine into a compensated position, thereby negating the need for any counterforce above the curve. Bassett and Bunnell used a TLSO to show that lateral trunk shift could be reduced in 58 percent of patients treated for thoracic curves, 65 percent of those treated with thoracolumbar and lumbar curve patterns, and 88 percent of those with double curve patterns. It is important to distinguish at this point that a well-compensated spine with C7 over S1 can still have substantially undesirable trunk shift. It is this trunk shift that Bassett and Bunnell are referring to, and they measure this trunk shift using Floman’s description, in which a horizontal line is drawn halfway between the seventh cervical and the first sacral vertebrae. A perpendicular line is then drawn at the horizontal line’s midpoint. The distance between this perpendicular line and the center of the first sacral vertebra represents the lateral trunk shift. The position of side bending and drastic in-orthosis decompensation of the original nocturnal orthosis also raises the question of long-term effects. Federico and Renshaw studied the decompensation issue with the bending orthosis and found that 6 of 11 patients experienced no change, 2 had improvement, and only 3 experienced decompensation, and it was on average only 0.9 cm. d’Amato et al. reported on a new TLSO that works by pushing the curves toward the midline, as opposed to being bent away from it. As with the other TLSOs, the research on this topic is limited. A long-term study will determine the efficacy of the two night TLSOs in spinal balance. Although the literature is limited, the research cited points out an important concept. The practitioner should accept in-orthosis Cobb correction when the head is over the pelvis in the coronal plane while maintaining good overall spinal balance. The Cobb angle has been for years the gold standard of spinal orthosis efficacy, so it warrants a literature review to determine how much correction should be sought. Moe and Kettleson published the first classic study on in-orthosis correction in 1970, showing median corrections, at the end of treatment, of 23 percent in thoracic curves, 18 percent in lumbar curves, and 10 percent in higher thoracic curves in their study of 169 patients. Best correction inorthosis in Moe and Kettleson’s group was 38 percent in thoracic curves, 55 percent in lumbar curves, and 17 percent for high thoracic. In 1980, Carr et al. reported that of the patients in this same group (133 patients with 192 separate curves), those who had at least 50 percent correction in their orthosis had the best chance for maintaining a reasonable amount of correction after the orthosis use was discontinued. Two other reports cited exactly 50 percent as a standard for in-orthosis correction for successful outcomes to be KEITH M. SMITH, CO, is affiliated with the Orthotic & Prosthetic Lab, Inc., St. Louis, Missouri.