Spontaneous Proximal Thoracic Curve Correction Following Selective Fusion of the Main Thoracic Curve in Adolescent Idiopathic Scoliosis

T.R. Kuklo*,
L.G. Lenke*,
D.S. Won*,
E.J. Graham*,
F.A. Sweet*,
R.R. Betz#,
K.M. Blanke*.
* St. Louis, MO,
#Philadelphia, PA, USA

INTRODUCTION:
There are no studies reporting the response of a structural proximal thoracic (PT) curve following instrumented fusion of the main thoracic (MT) curve in AIS.

PURPOSE:
The purpose of this study was to evaluate the spontaneous correction of the non–instrumented PT curve after correction of the MT curve by either a posterior (PSF) or anterior (ASF) instrumentation and fusion.

METHODS:
85 pts (single surgeon) with a PT curve ³ 20° (ave 29°. range 20–49°; ave residual side bending 18°, range 3–40°) were evaluated for PT curve flexibility – correction following PSF – PT curve not instrumented (n=44) and ASF – PT curve not instrumented (n=4 1). PT, MT, thoracolumbar–lumbar (TL–L) coronal and sagittal Cobb measurements, side bending Cobb, T1 tilt, clavicle angle, shoulder balance, and PT, MT and TL–L apical vertical translation (AVT) were also evaluated preop, one week postop, and at a minimum 2–yr postop (ave. 3.2 yrs). A patient outcome questionnaire was also completed to correlate patient satisfaction with respect to their shoulder balance and overall appearance. RESULTS: Radiographic: The two groups were found to be statistically equivalent (p=0.66) in terms of preop PT curve and PT side bending curve measurements. The improvement in the PT curve on both immediate postop and 2–yr minimum postop follow–up was significant (p<0.0001) for both groups. Additionally, the correction was maintained over time. However, the ASF correction of the PT curve was significantly greater than the PSF correction on both the immediate postop (p=0. 017) and minimum 2–yr postop (p=0.0024) evaluation, yet the MT curve correction was the same in both groups (p=0.45).

	Preop PT Curve	Preop side bending	Immediate postop	Immed Postop Change	Postop	Postop Change
PSF	29(20–49)*	20(8–40)	20	–9	21(5–39)	–8
ASF	28 (20–46)	17(3–35)	16	–12	16(2–31)	–12

*( ) denotes range

There was no difference in radiographically measured shoulder balance (p=0.27) or postop sagittal change in the PT curve (p=0. 12).

PATIENT OUTCOME:
Both groups reported improvement in shoulder balance and clinical appearance, but there was no statistical difference between the two groups (p=.24). Additionally, there was no reported deterioration in either parameter.

CONCLUSIONS:
Spontaneous proximal thoracic curve correction consistently occurs after instrumented correction of the main thoracic curve. Further, this spontaneous correction is significantly greater following an ASF vs. PSF of the MT curve.