11.1 Summary of the Procedure

The child is under general anesthesia. A body stockinette is placed over the trunk. Halter traction is applied through a windlass at the head and foot ends of the casting frame. The patient’s head is put into a halter strap and attached to the windlass at the head of the frame (Fig. 11.2). Two pelvic straps are wrapped around the waist overlying the body stockinette; they pass above the iliac crests and are tied at the level of the greater trochanter. Each strap runs under the ipsilateral leg to attach to the windlass at the foot end of the casting frame; the legs are supported by slings attached to the overhead crossbar of the casting frame.

A second body stockinette is applied so that the pelvic straps are situated between two layers of stockinette. They can be easily pulled out at the end of casting. A layer of 4-inch Bandage Ortho Wool is then applied over the stockinettes and snugly wrapped around the trunk (Fig. 11.3). The layers should not be bulky so that the clinician’s ability to achieve a good mold to the plaster is not compromised. A Velband roll is placed over the symphysis pubis to help mold the plaster cast over the iliac crests and abdomen and to prevent too tight a fit around the child’s abdomen. The Velband padding should be applied in such a way that there is adequate moulding with a good grip. Felt pads should be placed over all bony prominences to protect them and prevent pressure sores.

Hip flexion allows the derotation and correction of lumbar curves. Awareness of any shoulder asymmetry (arm positioning) and pelvic asymmetry / limb length discrepancy should be maintained, and with the ratchets, the traction of the straps should be adjusted as necessary.

The spine should be palpated during traction to determine the amount of curve correction needed. Once the surgeon is satisfied with the patient’s positioning, plaster of paris is applied. A few minutes should be allowed to pass before the clinician begins to mold the plaster as follows:

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  The rib / lumbar prominence is derotated by displacing the apex of the prominence anteriorly with posterolateral pressure for a thoracic curve and lateral pressure for a lumbar curve.

  
  
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  The frontal portion of the cast extends distally to the symphysis pubis to allow hip flexion to 100 degrees.

  
  
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  The cast extends distally at the back to the mid buttocks to allow gluteal hygiene.

A fiberglass layer is applied, and an epigastric window is cut with an oscillating saw to allow abdominal expansion and ease of breathing (Fig. 11.4). A window is also cut over the concavity of the curve on the side opposite the apex to allow passive correction. Another contralateral window may be applied for lumbar curves. The cast should be changed, on average, every 2 to 4 months and in response to curve changes. More frequent changes may be necessary in younger children.

It is worth noting that historically, derotation was applied through a strap that was attached to the side bar on the concavity of the curve, then passed under the patient and attached to a pulley on an overhead bar on the convexity of the curve. Presently, the surgeon applies derotation manually with anteriorly directed, posterolateral pressure over the apex of the curve while moulding the plaster.