Anterior Spinal Overgrowth Is the Result of the Scoliotic Mechanism and Is Located in the Disc.
METHODS
Cross-sectional study.


OBJECTIVE
To investigate the presence and magnitude of anterior spinal overgrowth in neuromuscular scoliosis and compare this with the same measurements in idiopathic scoliosis and healthy spines.


BACKGROUND
Anterior spinal overgrowth has been described as a potential driver for the onset and progression of adolescent idiopathic scoliosis (AIS). Whether this anterior overgrowth is specific for AIS or also present in nonidiopathic scoliosis has not been reported.


METHODS
Supine computed tomography (CT) scans of thirty AIS patients (thoracic Cobb 21-81°), thirty neuromuscular (NM) scoliotic patients (thoracic Cobb 19-101°) and 30 nonscoliotic controls were used. The difference in length in per cents between the anterior and posterior side {[(ΔA-P)/P]*100%, abbreviated to A-P%} of each vertebral body and intervertebral disc, and between the anterior side of the spine and the spinal canal (A-C%) were determined.


RESULTS
The A-P% of the thoracic curves did not differ between the AIS (+1.2 ± 2.2%) and NM patients (+0.9 ± 4.1%, P = 0.663), both did differ, however, from the same measurements in controls (-3.0 ± 1.6%; P < 0.001) and correlated linearly with the Cobb angle (AIS r = 0.678, NM r = 0.687). Additional anterior length was caused by anterior elongation of the discs (AIS: A-P% disc +17.5 ± 12.7% vs. A-P% body -2.5 ± 2.6%; P < 0.001, NM: A-P% disc +19.1 ± 18.0% vs. A-P% body -3.5 ± 5.1%; P < 0.001). The A-C% T1-S1 in AIS and NM patients were similar (+7.9 ± 1.8% and +8.7 ± 4.0%, P = 0.273), but differed from the controls (+4.2 ± 3.3%; P < 0.001).


CONCLUSIONS
So called anterior overgrowth has been postulated as a possible cause for idiopathic scoliosis, but apparently it occurs in scoliosis with a known origin as well. This suggests that it is part of a more generalized scoliotic mechanism, rather than its cause. The fact that the intervertebral discs contribute more to this increased anterior length than the vertebral bodies suggests an adaptation to altered loading, rather than a primary growth disturbance.


METHODS
4.
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
Rob C
RC
Brink
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
Tom P C
TPC
Schlösser
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
Dino
D
Colo
Department of Clinical and Experimental Medicine, Linköping University, Sweden.
Ludvig
L
Vavruch
Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands.
Marijn
M
van Stralen
Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
Koen L
KL
Vincken
Department of Clinical and Experimental Medicine, Linköping University, Sweden.
Marcus
M
Malmqvist
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
Moyo C
MC
Kruyt
Department of Clinical and Experimental Medicine, Linköping University, Sweden.
Hans
H
Tropp
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
René M
RM
Castelein
D000293:Adolescent; D002648:Child; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging*; D008297:Male; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000209:etiology; D016683:Supine Position; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
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