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Multi Center Comparison of the Factors Important In Restoring Thoracic Kyphosis During Posterior Instrumentation for Adolescent Idiopathic Scoliosis

Saturday, October 20, 2012: 3:13 PM
Melrose (Hilton Riverside)
Shafagh Monazzam, MD1, Peter O. Newton2, Tracey Bastrom2 and Burt Yaszay2, (1)Orthopedics, Radys Children Hospital, San Diego, CA, (2)Orthopedics, Rady's Childrens Hospital, San Diego, CA

Purpose

The purpose of this study was to determine what factors were most predictive of

postoperative correction of hypokyphosis when segmental posterior implants were used in

treating thoracic adolescent idiopathic scoliosis (AIS).

Methods

Prospectively collected cases from a multi-center study were analyzed.

Lenke type 1-4 AIS patients with preoperative kyphosis of 5-20°, treated with posterior pedicle

screws, a 5.5mm rod, and by a surgeon who had at least 20 patients in the database were

included. Patients were divided into two groups postoperatively based on first erect x-rays: those

remaining hypokyphotic (HK, T5-T12 <20° or an increase <5° in T5-T12 sagittal kyphosis) and

those restored to normal kyphosis (NK, T5-T12 >20° with ≥5° increase). Patients whose

correction was <5° were considered unchanged (hypokyphotic). Regression analysis was done

on four preoperative factors thought to influence the postoperative kyphosis: preoperative

kyphosis, the surgeon, rod material utilized (Steel vs. Ti) and use or not of a posterior release

(Ponte osteotomies).

Results

Of the 280 patients included in the study, 222 remained hypokyphotic and 53 achieved

normal kyphosis. There were no differences in preoperative kyphosis (13.4 ± 5 HK group vs 14.5

± 4 NK group) and age (14.7 HK group vs 14.6 NK group) between the patients who were

brought to >20° (NK) and those who remained <20° (NK). Of the factors evaluated, the surgeon

who performed the operation was the most significant predictor of restoration of normal

kyphosis. Comparison of surgeons showed the rate of normalizing kyphosis ranged from 6% to

42% (p=0.001) and that there was no difference in the degree of preoperative kyphosis between

surgeons.

Conclusion

Restoration of thoracic kyphosis remains a challenge in posteriorly treated thoracic

AIS cases. The “surgeon” was the only significant predictor of restoring normal kyphosis,

emphasizing the importance of intraoperative techniques not presently documented in our study

database (e.g., extent of release, compression/distraction forces, rod contour, other corrective

techniques).