Quantification of intervertebral disc volume properties below spine fusion, using magnetic resonance imaging, in adolescent idiopathic scoliosis surgery.
METHODS
Prospective clinical study. A quantification of volume and hydration variation of the intervertebral discs, using magnetic resonance imaging (MRI), in the lumbar spine before and after surgery performed in adolescent idiopathic scoliosis (AIS).


OBJECTIVE
To evaluate an objective quantification of volume and hydration of intervertebral discs below spine fusion in scoliosis surgery.


BACKGROUND
Repercussion of long spine fusion on the free lower lumbar spine is one of the major concerns of scoliosis surgery. However, the evolution of lumbar intervertebral disc below thoracolumbar fusions remains unknown.


METHODS
MRI performed in the clinical protocol, concerned 28 patients having an idiopathic scoliosis. They underwent posterior instrumentations. MRI was obtained before surgery, after surgery at 3 months and for 15 patients at 1 year. MRI data were posttreated using a custom-made image processing software to semiautomatically derive volume properties of disc, anulus fibrosus, and nucleus pulposus. The nucleus-disc volume ratio was also an indicator of the hydration level.


RESULTS
The reliability of the three-dimensional reconstruction process was initially verified using an intraoperator reproducibility test. Original preoperative data on disc volume properties were then derived. Postoperative volume variations were quantified in discs below spine fusion taking into account the level of the arthrodesis and the disc location. It showed that the postoperative volume criteria increased significantly for nucleus, disc, and nucleus-disc volume ratio and some magnitude modulation could be conditioned by the location of surgical instrumentation. Some stabilization or reduction depending on disc level and arthrodesis size between 3 months and 1 year is observed in the follow-up. It tended to prove that the recovery of balance physiologic positioning and inherent biomechanical loads could induce a restored hydration of disc, which should favor the remodeling of free segments.


CONCLUSIONS
This work was the first report dealing with consequences of scoliosis surgery on subjacent disc in term of volume and hydration properties.
Violas
Philippe
P
Department of Pediatric Surgery, Pontchaillou University Hospital, Rennes, France. pviolas@hotmail.com
Estivalezes
Erik
E
Briot
Jérome
J
Sales de Gauzy
Jérome
J
Swider
Pascal
P
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001696:Biomechanical Phenomena; D001834:Body Water / Q000502:physiology; D002356:Cartilage / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D002648:Child; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D015588:Observer Variation; D009984:Orthopedic Fixation Devices; D011446:Prospective Studies; D011859:Radiography; D020127:Recovery of Function; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery; D013123:Spinal Fusion; D013131:Spine / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology