Background
Review of literature reveals that in Idiopathic Scoliosis (IS) children, the post-operative
rib hump (RH) correction using full transpedicular screw construct has never been
compared to hybrid constructs, applying the Rib-Index (RI) method. Therefore the aim
of this report is to study which of the above two constructs offers better postoperative
Rib Hump Deformity (RHD) correction.
Methods
Twenty five patients with Adolescent Idiopathic Scoliosis (AIS) were operated using
full pedicle screw construct or hybrid construct. Sixteen underwent full screw instrumentation
(group A) and nine an hybrid one (group B). The median age for group A was 15 years
and for group B 17.2 years. The RHD was assessed on the lateral spinal radiographs
using the RI. The RI was calculated by the ratio of spine distances d1/d2, where d1
is the distance between the most extended point of the most extending rib contour
and the posterior margin of the corresponding vertebra on the lateral scoliosis films
and d2 is the distance from the least projected rib contour and the posterior margin
of the same vertebra. Moreover the amount of RI correction was calculated by subtracting
the post-operative RI from the pre-operative RI.
Results
Although within group A the RI correction was statistical significant (the pre-op
RI was 1.93 and the post-op 1.37; p0.001) and similarly in group B (the mean pre-op
RI was 2.06 while the mean post-op 1.51; p=0.008), between group A and B the post-operative
RI correction mean values were found to be no statistically significant, (p=0.803).
Conclusion
Although the pre- and post-operative RI correction was statistically significant within
each group, this did not happen post-operatively between the two groups. It appears
that the RHD correction is not different, no matter what the spinal construct type
was used. Provided that the full screw construct is powerful, the post-operative derotation
and RHD correction was expected to be better than when an hybrid construct is applied,
which is not the case in this study. It is therefore implied that the RHD results
more likely from the asymmetric rib growth rather than from vertebral rotation, as
it has been widely believed up to now. In 2013 Lykissas et al, reported that costoplasty
combined with pedicle screws and vertebral derotation significantly improved RH deformity
as opposed to pedicle screws and vertebral derotation alone. Another interesting implication
is that the spinal deformity is the result of the thoracic asymmetry, implication
in line with the late Prof. John Sevastikoglou’s (Sevastik’s) thoracospinal concept.