Retrospective Review of Shoulder Balance Comparing Adolescent Idiopathic Scoliosis (AIS) to Early Onset Scoliosis (EOS) Patrick J. Cahill William Lavelle Swamy Kurra Stephen A. Albanese Randal R. Betz

Hypothesis Study Design Compare AIS and EOS populations to see if surgical techniques used had an effect on the ultimate alignment of the shoulder girdle. Study Design Retrospective study (n = 145): 2 prospectively collected databases HARMS Study Group Children’s Spine Study Group Reviewed AIS and EOS patients involved in definitive fusions

Background Treatment of spinal deformity can be challenging. AIS surgical distraction techniques, EOS (growing rods or VEPTRs) and final definitive fusion all focus on improvement of spinal deformity. Few studies have investigated the effect of corrective measures on overall alignment of the shoulder girdle.

Methods Study categorized into: AIS Group (n = 111) EOS Group (n = 34) Compared prior and post definitive fusion radiographic shoulder balance parameters between groups (AIS vs. EOS) T1 tilt angle Kuklo clavical angle Coracoid height difference (CHD) Clavicular tilt angle difference (CRAD) Clavicle-rib intersection difference (CRID)

T1 Tilt angle Kuklo Clavicle angle Angle formed between superior end plate of T1 and horizontal line Angle between horizontal line and the line connecting highest point of clavicle

Clavicle Tilt Angle difference Differences of the left and right clavicle tilt angles. Clavicle Tilt angle is the angle between the horizontal angle and the line passing along the middle of clavicle.

Clavicle height difference Coracoid height difference Difference between the points where right and left clavicle intersect ribcage, respectively Right and left coracoid height difference

Methods Preop and Postop Compared groups by ANOVA test Measured major and minor coronal Cobb angles Measured sagittal imbalances Measured percentage of corrections from lateral and posterioranterior (PA) standing radiographic films Compared groups by ANOVA test P < 0.05 considered statistically significant

Results Mean age at definitive fusion: AIS = 11.3 years EOS – 12.6 years Post definitive fusion shoulder girdle measurements were statistically significant. (Table 1) Though measurements were significant, but no significant difference in post definitive means between groups. (Table 1) Mean post definitive fusion major Cobb corrections were greater in AIS vs. EOS: AIS Group: 59.36o preop to 20.18o postop EOS Group: 67.26o preop to 50.7o postop Post definitive fusion p< 0.0001 between groups

Post Definitive Fusion Table 1 T 1 Tilt CA CTAD CRID CHD Mean Mean (cm) Post Definitive Fusion AIS -5.38o -2.33o -4.23o -1.092 -1.255 EOS 1.63o 0.52o 0.8o 0.153 0.225 Normal Population (a) 1.3o (+1.4o) 2.2o (+1.7o) 4.0o (+3.2o) 0.48 (+0.36) 0.69 (+0.58) (a) Normal population of non-scoliosis patients in Akel I, et al. Evaluation of shoulder balance in the normal adolescent population and its correlation with radiographical parameters. Eur Spine J. 2008 Mar; 17(3): 348-54.

Conclusion Both AIS and EOS surgical techniques are effective in maintaining proper shoulder girdles alignment. AIS techniques show more success in terms of Cobb angle correction than EOS techniques.