Abstract
Background: In preoperative thoracic (TC) and thoracolumbar (TLC) AIS curves to evaluate periapical rib-vertebra angle asymmetry [1] and rib-spinal angle asymmetry in relation to the spinal deformity and the 4th column support of the spine [2].
Methods: Consecutive preoperative AIS patients having spinal instrumentation and fusion were assessed using radiographs and ultrasonographs. Twenty-eight preoperative patients with AIS were studied (TC 19, apex T8-9 in 15, TLC 9, apex T12 in 2, L1 in 7, mean Cobb angle 51 degrees). In AP radiographs the following were measured by one observer (RGB): Cobb angle (CA), apical vertebral rotation (AVR) and apical vertebral translation (AVT) from the T1-S1 line; in TC at 6 levels about the apical vertebra (3 above, at and 2 below) for each of 1) rib-vertebral angles (RVAs) and difference (RVAD=concave minus convex RVA), 2) rib-spinal angles (RSAs) to the T1-S1 line and difference (RSAD), and 3) vertebral tilt; and in TLC the RVAs, RVADs, RSAs and RSADs of ribs 11 & 12. The ultrasound apical spine-rib rotation difference (SRRD) was obtained as a measure of transverse plane rib deformity. With the subject in a prone position and head supported, readings of laminal rotation (LR) and rib rotation (RR) were made on the back at 12 levels by one of two observers (RKA, ASK) using an Aloka SSD 500 portable ultrasound machine with a veterinary long (172mm) 3.5 MHz linear array transducer. The maximal difference between LR and RR about the curve apex was calculated as the apical spine-minus-rib rotation difference (SRRD).
Results: Thoracic curves. The RVADs (but not the RVAs, RSAs or RSADs) only at 2 & 3 levels above the apex correlate significantly with each of CA (p=0.054), AVR (p=0.047), AVT (p=0.014, after controlling for CA p=0.131) and vertebral tilt (p=0.032) but not SRRD (all two levels above apex). Thoracolumbar curves. The 11th RSAD (but not RVAD or RSAs) correlates significantly with each of AVR (r= −0.776, p=0.014, after controlling for CA p=0.022) and SRRD (r= −0.890, p=0.001, after controlling for CA p=0.003) that together correlate significantly (r=0.672, p=0.048).
Conclusion: In TC supra-apical rib asymmetry (RVAD) in sternally-stabilized [2] and longest levers of the sternal-rib complex is associated with spinal deformity; in TLC supra-apical rib asymmetry (11th RSAD) is associated with transverse plane deformity of each of the apical vertebra (mainly L1) and 12th ribs. These rib associations, probably secondary to the spinal deformity, may involve a primary rib component in the 4th spinal column. The prognostic value of supra-apical RVAD and RSAD for progressive AIS needs to be evaluated.
The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.
References:
1 B Xiong, JA Sevastik, R Hedlund et al. Radiographic changes at the coronal plane in early scoliosis. Spine1994;19(2):159–64. Google Scholar
2 EE Berg. The sternal-rib complex. A possible fourth column of the spine. Spine1993,18 (13):1916–19. Google Scholar
