Vertical Expandable Prosthetic Titanium Rib for the Treatment of Early-Onset Scoliosis

John T. Smith

Robert M. Campbell Jr

INDICATION/CONTRAINDICATIONS

The vertical expandable prosthetic titanium rib (VEPTR) was conceived and designed for the management of thoracic insufficiency syndrome (TIS) in children with severe spine and chest wall deformity in the growing child (1). TIS is defined as the inability of the thorax to support normal respiration or lung growth. TIS can be present in a variety of conditions affecting the growing spine including congenital scoliosis with fused ribs, progressive scoliosis of neurogenic causes, and other rare conditions that compromise volume of the thorax. The principal indication for the use of VEPTR is to manage TIS by creating volume in the thorax to promote lung growth while controlling spine deformity and promoting spine growth in the young child.

Contraindications to the use of the VEPTR device include severe malnutrition and small size where the device cannot be adequately covered with skin/soft tissue.

PREOPERATIVE PLANNING

There are a number of important considerations prior to initiating and treatment of early-onset scoliosis (EOS) whether with VEPTR or by other means. The general health of the child should be thoroughly assessed. When possible, an initial pulmonary assessment should be completed. Nutritional evaluation is important in children demonstrating failure to thrive. Imaging including an MRI of the spine should be obtained, particularly with curves of congenital origin to assess for intraspinal anomalies. CT scans are often valuable to understand the three-dimensional anatomy of the deformity
and for preoperative planning. Traction films are often of value, especially in neuromuscular curves to determine flexibility. Emerging in limited centers is the use of dynamic MRI to evaluate the function of the lungs and the diaphragm before and after surgery.

SURGICAL PROCEDURE FOR SCOLIOSIS WITHOUT RIB ANOMALIES

Rib to Pelvis VEPTR Technique (2)

This technique requires general anesthesia. Incisions to complete the procedure are limited, and therefore, very little blood loss is expected. The child is positioned prone on either soft rolls or a spine frame depending on size. The entire spine is prepped and draped from the base of the neck to the pelvis.

The typical construct is planned to go from the 2nd to 4th ribs to the pelvis. A midline incision is made in the upper thoracic spine. Dissection is carried down to the level of the spinous process. The rhomboid muscle is dissected off the spinous bilaterally, and the interval between the erector spinae and the rhomboid is developed laterally. Then, the lateral margin of the erector spinae is elevated medially to the tip of the transverse process. This location is confirmed using the image intensifier.

VEPTR rib hooks in a variety of configurations are then placed, preferably on more than one rib. The VEPTR II device offers the opportunity to stack rib hooks on 2 to 3 adjacent ribs and use an outrigger to place a transverse rib hook in a more lateral position. To place the hooks, the dissection goes gently through the intercostal muscles and is extraperiosteal on the rib, developing an interval between the pleura and the ventral side of the rib. Final position is confirmed after rib hook placement.

Standard fixation for the pelvis is to place S-hooks onto the ileum. An oblique incision is made about 1 cm lateral to the posterior superior iliac spine (PSIS). The best landmark is to develop the interval immediately lateral to the erector spine muscle mass. This interval is followed to the top of the ileum. A limited dissection of the gluteus maximus off the outer table of the ileum and an interval anterior to the ileum at the same level is made. Preservation of iliolumbar ligaments helps to preserve the stability of the hook. The hook generally slides in easily. A 5.0 to 6.0-mm connector is used to connect the VEPTR device to the pelvic hook.

A properly sized VEPTR device is then selected. The surgeon must estimate both the proper size of the expandable portion of the VEPTR and the length that will be gained with the initial distraction and correction of the curve. Experience makes this estimation easier. The device should be locked with a distraction lock and contoured with particular attention to create lumbar lordosis. A long pituitary rongeur or uterine packing forceps are passed from the proximal to the distal incision as deep as possible, and then a no. 20 chest tube is pulled from distal to proximal. Then, the VEPTR device is pushed into the chest tube and used to guide the device safely from proximal to distal. It is engaged into the connector distally, and the proximal end is cantilevered into the rib hooks proximally. Once stabilized proximally, then a C-ring is placed distally and a distractor is used to distract against the pelvis and correct the curve. Once adequate tension and correction are obtained, the set screws on the domino connector are tightened and the C-ring is removed. Typically, this construct is placed bilaterally with the convex side instrumented in a similar fashion after the concave side is done first. Wounds are irrigated in and closed in a standard fashion. A Valsalva maneuver is done to confirm the integrity of the pleura prior to closure. Our current practice is to sprinkle 1 g of vancomycin powder over the implants prior to closure. Every effort should be made to obtain a multiple-layer closure.

POSTOPERATIVE MANAGEMENT

Postoperative management is standard. Depending on the health of the patient, postoperative care may require initial ventilator support, especially after expansion thoracoplasty. Drains are needed if the chest has been opened. Fluid management is critical as all kids with this procedure tend to have reduced urine output in the initial 24 hours after surgery and, if given additional fluids, tend to third space the fluid making extubation more difficult. We strive to keep fluid balance tightly managed. Pain management will be required during the initial postoperative period.

COMPLICATIONS TO AVOID

Complications are an expected event in the management of severe spinal deformity in the growing child. Providing families a reasonable expectation of these events tends to minimize the impact of these problems as they occur.

The most important complications to avoid include neurologic injury during the distraction process. With VEPTR surgery, this is more likely to occur in the upper extremity than the lower extremity. Rib hooks should generally not be placed on the first rib since this may impinge on the brachial plexus. The exception to this rule is in the setting of cervicothoracic congenital scoliosis when the top rib is a much larger than normal conjoined rib that may be needed as an anchor. All extremities should be monitored during initial distraction procedures using modern techniques. Pulse oximetry on the extremity may be of value as well. Other common complications include infection, wound dehiscence, pneumonia, and implant migration. The use of intrawound vancomycin powder may reduce the incidence of infection.

SURGICAL PROCEDURE FOR CONGENITAL SCOLIOSIS WITH FUSED/ABSENT RIBS

General Approach

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