Clin Orthop Surg.  2011 Mar;3(1):24-33. 10.4055/cios.2011.3.1.24.

Changes in Level of the Conus after Corrective Surgery for Scoliosis: MRI-Based Preliminary Study in 31 Patients

• Hong JY
• Suh SW
• Park JH
• Hur CY
• Hong SJ
• Modi HN

• KMID: 999457
• DOI: http://doi.org/10.4055/cios.2011.3.1.24

Abstract

BACKGROUND
Detection of postoperative spinal cord level change can provide basic information about the spinal cord status, and electrophysiological studies regarding this point should be conducted in the future.
METHODS
To determine the changes in the spinal cord level postoperatively and the possible associated factors, we prospectively studied 31 patients with scoliosis. All the patients underwent correction and posterior fusion using pedicle screws and rods between January 2008 and March 2009. The pre- and postoperative conus medullaris levels were determined by matching the axial magnetic resonance image to the sagittal scout image. The patients were divided according to the change in the postoperative conus medullaris level. The change group was defined as the patients who showed a change of more than one divided section in the vertebral column postoperatively, and the parameters of the change and non-change groups were compared.
RESULTS
The mean pre- and postoperative Cobb's angle of the coronal curve was 76.80degrees +/- 17.19degrees and 33.23degrees +/- 14.39degrees, respectively. Eleven of 31 patients showed a lower conus medullaris level postoperatively. There were no differences in the pre- and postoperative magnitude of the coronal curve, lordosis and kyphosis between the groups. However, the postoperative degrees of correction of the coronal curve and lumbar lordosis were higher in the change group. There were also differences in the disease entities between the groups. A higher percentage of patients with Duchene muscular dystrophy had a change in level compared to that of the patients with cerebral palsy (83.3% vs. 45.5%, respectively).
CONCLUSIONS
The conus medullaris level changed postoperatively in the patients with severe scoliosis. Overall, the postoperative degree of correction of the coronal curve was higher in the change group than that in the non-change group. The degrees of correction of the coronal curve and lumbar lordosis were related to the spinal cord level change after scoliosis correction.

Keyword

Scoliosis; Corrective surgery; Spinal cord level; Conus medullaris

MeSH Terms

Adolescent
Adult
Cerebral Palsy/complications
Child
Female
Humans
Kyphosis/radiography
Lordosis/radiography
Lumbar Vertebrae/radiography/surgery
*Magnetic Resonance Imaging
Male
Muscular Dystrophy, Duchenne/complications
Prospective Studies
Scoliosis/complications/radiography/*surgery
Severity of Illness Index
Spinal Cord/*pathology
Thoracic Vertebrae/radiography/surgery
Young Adult

Figure

• 

  Fig. 1 The serial axial magnetic resonance images show the loss of the conus configuration. The tip of the conus was defined as the most distal point of the cord that could be visualized. The images show (A) the conus body, (B) the conus tip and (C) the cauda equina.

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  Fig. 2 The sagittal magnetic resonance image shows each vertebra/disc unit, which was divided into three equal portions (upper, middle, lower), and the intervertebral disc.

• 

  Fig. 3 The preoperative (A) anteroposterior (AP) and (B) lateral radiographs of a 15-year-old male patient show a Cobb angle, lordosis and kyphosis of 68°, 37°, and 41°, respectively. The postoperative (C) AP and (D) lateral radiographs show a Cobb angle, lordosis and kyphosis of 20°, 32°, and 29°, respectively. The conus tip was identified on the axial magnetic resonance (MR) image and the location was determined by comparing this image with the sagittal scout image. The preoperative (E) sagittal and (F) axial MR images and the postoperative (G) sagittal and (H) axial MR images show the conus tip is located at the L1-L2 disc space.

• 

  Fig. 4 The preoperative (A) anteroposterior (AP) and (B) lateral radiographs of a 23-year-old female patient show a Cobb angle, lordosis and kyphosis of 93°, -15°, and 38°, respectively. The postoperative (C) AP and (D) lateral radiographs show a Cobb angle, lordosis and kyphosis of 36°, 26°, and 37°, respectively. The conus tip was identified on the axial MR image, and the location was determined by comparing this image with the sagittal scout image. The preoperative (E) sagittal and (F) axial MR images and the postoperative (G) sagittal and (H) axial MR images show the conus tip is located at the upper L1 body preoperatively and at the lower L1 body postoperatively.

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