Clin Orthop Surg.  2011 Jun;3(2):89-100. 10.4055/cios.2011.3.2.89.

Pedicle Screw Instrumentation for Adolescent Idiopathic Scoliosis: The Insertion Technique, the Fusion Levels and Direct Vertebral Rotation

• Suk SI

• KMID: 1719304
• DOI: http://doi.org/10.4055/cios.2011.3.2.89

Abstract

The pedicle is a power nucleus of the vertebra and offers a secure grip of all 3 columns. Pedicle screw instrumentation has advantages of rigid fixation with improved three-dimensional (3D) correction and it is accepted as a reliable method with a high margin of safety. Accurate placement of the pedicle screws is important to reduce possible irreversible complications. Many methods of screw insertion have been reported. The author has been using the K-wire method coupled with the intraoperative single posteroanterior and lateral radiographs, which is the most safe, accurate and fast method. Identification of the curve patterns and determining the fusion levels are very important. The ideal classification of adolescent idiopathic scoliosis should address the all patterns, predict the extent of accurate fusion and have good inter/intraobserver reliability. My classification system matches with the ideal classification system, and it is simple and easy to learn; and my classification system has only 4 structural curve patterns and each curve has 2 types. Scoliosis is a 3D deformity; the coronal and sagittal curves can be corrected with rod rotation, and rotational deformity has to be corrected with direct vertebral rotation (DVR). Rod derotation and DVR are true methods of 3D deformity correction with shorter fusion and improved correction of both the fused and unfused curves, and this is accomplished using pedicle screw fixation. The direction of DVR is very important and it should be opposite to the direction of the rotational deformity of the vertebra. A rigid rod has to be used to prevent rod bend-out during the derotation and DVR.

Keyword

Adolescent idiopathic scoliosis; Pedicle screw instrumentation; Pedicle screw insertion technique; Fusion level; Direct vertebral rotation

MeSH Terms

Adolescent
*Bone Screws
Humans
Orthopedic Procedures/instrumentation/*methods
Rotation
Scoliosis/*surgery
Spinal Fusion

Figure

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  Fig. 1 (A) Intraoperative posteroanterior and lateral radiographs after K-wires are inserted. (B) Magnified T8-10. Exact pedicle entry points are marked.

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  Fig. 2 Single thoracic adolescent idiopathic scoliosis is defined as a thoracic curve that is more than 40° and is larger than the lumbar curve. A selective thoracic fusion from the proximal neutral vertebra (NV) to the distal NV is recommended. There are two types, A and B, depending on the relation between the distal end vertebra (EV) and the NV. (A) In type A, the NV is located at the EV + 1 or the same level, and can be fused to the NV. (B) In type B, the NV is located at the EV + 3 and must be fused to the NV - 1 or the EV + 2.

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  Fig. 3 The double major curve is defined as a lumbar curve greater than 40° and larger the thoracic curve. The thoracic cuve is more than 30° and both curves have to be fused. There are two types, A and B. In type A, L3 crosses the mid sacral line and the rotation is less than grade 2 in the bending film. In type B, L3 does not cross the mid sacral line and the rotation is more than grade 2 in the bending film.

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  Fig. 4 The thoracolumbar and lumbar (TL/L) curve is defined as a TL/L curve more than 40° with a thoracic curve less than 30°. The TL/L curve only should be fused. The two types, A and B, depend on whether the L3 crosses mid sacral line and the rotation is more or less than grade II, in bending radiographs. This is the same as in the double major curve.

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  Fig. 5 (A) A 15-year-old girl with a single thoracic adolescent idiopathic scoliosis, type A, in which the neutral vertebra (NV) is the same as the end vertebra (EV). The distal fusion level is T12 (NV) and the direction of the direct vertebral rotation (DVR) of the distal NV is the opposite direction compared with the thoracic DVR. (B) The patient is treated with the rod derotation and DVR, and the postoperative radiographs show a well-balanced spine.

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  Fig. 6 (A) A 14-year-old girl with a single thoracic adolescent idiopathic scoliosis, type B, in which the neutral vertebra (NV) is located at the end vertebra (EV) + 3. The distal fusion level is the NV - 1 (L3) and the direction of the direct vertebral rotation (DVR) of the distal NV is the same direction compared with the thoracic DVR. (B) The patient is treated with the rod derotation and the DVR method.

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  Fig. 7 (A) A 13-year-old girl with a double thoracic adolescent idiopathic scoliosis. The distal fusion level is the neutral vertebra (NV), which is L1, and the direction of the direct vertebral rotation (DVR) is the opposite direction compared to the thoracic DVR. (B) Both thoracic curves are fused with four rods, rod derotation and DVR. (C) The preoperative unequal shoulder height is well corrected postoperatively. EV: end vertebra.

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  Fig. 8 (A) A 13-year-old girl with a double major curve of adolescent idiopathic scoliosis. The direct vertebral rotation (DVR) direction of the lumbar curve is the opposite to the direction of the thoracic DVR. (B) Bending radiographs show that L3 crosses the mid sacral line and L3 rotation is less than grade II (type A). This is fused to the neutral vertebra (NV) - 1 (L3). (C) Both thoracic and lumbar curves are treated with two rods, translation and DVR. EV: end vertebra.

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  Fig. 9 (A) A 17-year-old girl with a double major curve, type B. The direct vertebral rotation (DVR) direction of the lumbar curve is opposite to the direction of the thoracic DVR. (B) Bending radiographs show that L3 does not cross the mid sacral line and L3 rotation is more than grade II (type B), which is fused to the neutral vertebra (NV; L4). (C) The patient is treated with two rods, rod derotation and DVR. EV: end vertebra.

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  Fig. 10 (A) A 13-year-old girl with a thoracolumbar curve with fusion of the thoracolumbar curve only. The direction of direct vertebral rotation (DVR) is the same in both the thoracic and the lumbar curve. (B) Bending radiographs show L3 crosses the mid sacral line and L3 rotation is less than grade II (type A) on bending film. (C) The patient is fused to the neutral vertebra (NV)-1 (L3) with rod derotation (S bended rod) and DVR. EV: end vertebra.

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  Fig. 11 (A) A 15-year-old girl with a thoracolumbar curve. (B) Bending radiographs show that L3 does not cross the mid sacral line and L3 rotation is more than grade II (type B). (C) The patient is fused to the neutral vertebra (NV; L4) with rod derotation (S bended rod) and direct vertebral rotation. EV: end vertebra.

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