Opening Wedge Thoracoplasty and Vertical Expandable Prosthetic Titanium Rib Insertion for Congenital Scoliosis and Fused Ribs

 

 

 

 

DEFINITION

This procedure lengthens the concave constricted hemithorax through a vertical expandable prosthetic titanium rib (VEPTR) expansion thoracoplasty with indirect correction of congenital scoliosis to maximize the potential for thoracic growth in order to benefit the growth of the underlying lungs.

 

 

ANATOMY2

 

Congenital scoliosis and fused ribs is a severe variant of congenital scoliosis.

 

Long unilateral unsegmented bars are common on the concave side of the curve with multiple contralateral hemivertebrae (FIG 1).

 

The extent of rib fusion is commonly extensive, usually concentrated on the concave side of the curve, and, when adjacent to the spine, can contribute to curve progression through tethering.

 

Mixed deformities are also seen, with areas of absent ribs adjacent to areas of fused ribs.

 

 

 

 

FIG 1 • A 2 1/2-year-old girl with rapidly progressing congenital scoliosis and fused ribs. A long, unilateral, unsegmented bar is seen on the concave side and multiple hemivertebrae are seen on the convex side. The height of the concave hemithorax is considerably decreased compared to the convex side.

 

Both the height and width of the concave fused hemithorax is often diminished, with reduction in height of the entire thorax common from multiple congenital anomalies of the thoracic spine.

 

All these anomalies combine to reduce overall thoracic volume.

 

 

This variant is classified as a type II volume depletion deformity of the thorax.1

 

PATHOGENESIS

 

Congenital scoliosis is associated with haploinsufficiency of the Notch signaling pathway genes8 and the more severe variant spondylocostal dysostosis is associated with DLL3 mutations.4

 

Fused ribs and congenital scoliosis is a widespread “failure of segmentation” involving both spine and rib cage and is most commonly seen in conditions such as VACTERL (vertebral anomalies, anal atresia, cardiovascular anomalies, tracheoesophageal fistula, esophageal atresia, renal or radial anomalies, limb anomalies) syndrome or spondylocostal dysostosis but can also occur as an isolated anomaly.

 

NATURAL HISTORY

 

Severe congenital scoliosis with fused ribs often progresses rapidly without treatment, with growth inhibition of the lung on the concave side of the curve.

 

Early extrinsic restrictive lung disease from the constrictive effects of the severe spine and rib cage anomalies may be clinically masked in the young child by elevation in resting respiratory rate and reduction in play activities to aid overall body oxygenation, but as the youngster becomes older, a high respiratory rate becomes difficult to sustain and early respiratory insufficiency develops.

 

Clinically, sleep disturbances are usually first seen, then frank clinical daytime dyspnea may develop with the need for respiratory assistance such as nasal oxygen, continuous positive airway pressure (CPAP)/bilevel positive airway pressure (BIPAP), or even ventilator support. Untreated infantile scoliosis patients begin to experience increased mortality from respiratory failure after age 20 years, with a death rate three times normal

by age 60 years,6 but the long-term mortality in untreated congenital scoliosis and fused ribs is unknown.

 

 

P.835

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The clinical assessment should include both general and pulmonary health.

 

 

Onset of radiologic and clinical scoliosis should be determined; clinical course and response to treatment recorded.

 

Details about any prior spine surgery are important to note because that may affect growth potential of the spine.

 

A respiratory history should include determination of the frequency of colds, bronchitis, and pneumonias due to bacterial origins or viral etiology such as respiratory syncytial virus (RSV). Increasing frequency of respiratory illnesses, need for hospitalization for them, or the need for ventilatory assist to recover from them is worrisome and suggests developing respiratory insufficiency.

 

Voluntary reduction in play activities by the child, gradually lowering them to the point where aerobic demands are minimal, also is an early sign of respiratory insufficiency. An extensive review of related body systems is important.

 

Congenital heart disease can contribute to clinical respiratory insufficiency and cor pulmonale can be life-

threatening.

 

Gastrointestinal (GI) abnormalities such as gastroesophageal reflux disease (GERD) may cause aspiration pneumonia.

 

Congenital renal abnormalities are seen in a third of congenital scoliosis patients.

 

Abnormal bowel and urinary incontinence should be documented and neural cause investigated.

 

Physical examination should include measurement of percentile weight/height and resting respiratory rate.

 

 

Low weight is common in children with thoracic insufficiency syndrome and may be related to the increased work of rapid breathing.7

 

Normal respiratory rate is 60 to 80 breaths per minute in the first year of life, declining to 20 to 24 breaths per minute by age 4 to 6 years.5

 

Nasal flaring suggests labored breathing.

 

Perioral cyanosis or clubbing of the fingertips implies hypoxia.

 

Unequal shoulder heights, head and truncal decompensation as well as any leg limb inequality are measured.

 

Adams forward bend test is used to observe rotation of the back on the convex side of the curve. Isolated rib prominences and any generalized abnormal shape of the chest is noted, including pectus carinatum or excavatum.

 

Rib defects are measured, and clinical instability is estimated by degree of collapsing inward paradoxical motion with respiration. Areas of stiff chest wall over fused ribs are measured and location recorded. Chest circumference at the nipple line is measured and normal percentile determined.

 

A thumb excursion test (FIG 2) is done. From the back, the hands are placed lightly on each side of the chest with the thumbs extended medially, equidistant from the spine. The patient takes a deep breath, with chest expansion moving each hand outward with the tips of the thumbs moving away from the spine.

 

 

In normal individuals, the thumbs move out symmetrically with deep respiration, but with chest wall stiffness, the thumbs barely move with breathing.

 

The motion is graded: +3 is greater than 1 cm motion outward, +2 is 1 to 0.5 cm motion, +1 is less than

0.5 cm, and +0 is no movement. The patient is also assessed for a marionette sign.1

 

 

 

FIG 2 • A. The thumb excursion test in a normal 9-year-old boy. The hands are placed loosely around the trunk, with the thumbs equidistant from the spine. B. The patient is asked to take a deep breath and the outward motion of the medial tip of the thumb is graded for each side: +3 is more than 1 cm of motion outward, +2 is 1 to 0.5 cm of motion, +1 is less than 0.5 cm, and +0 is no movement. The lower the score, the more stiff the chest is clinically, reflecting diminished ability to contribute to respiration. Note the large movement of the thumbs away from the spine in this normal child.

 

 

With respiration, the patient's head bobs up and down, much like that of a marionette puppet.

 

 

This is a positive sign, suggesting that the diaphragm is encountering resistance to downward excursion with inspiration, common in spine deformity, and in essence, the diaphragm is doing a “push-up” against body weight to fully expand the lung.

 

This is a high-energy expenditure and is not sustainable over time, leading to respiratory failure.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Weight-bearing anteroposterior (AP) and lateral radiographs of the spine, including the entire chest as part of the radiographs should be obtained, along with supine lateral bending films of the spine.

 

AP and lateral radiographs of the C-spine with flexion/extension laterals should be obtained. Computed tomography (CT) scan of the chest and lumbar spine, 5-mm intervals, and an unenhanced magnetic resonance imaging (MRI) of the entire spinal cord is obtained.

 

Dynamic lung MRI (FIG 3) is helpful in visualizing functional impairment of the thorax.

 

Pulmonary function tests by spirometry for patients older than age 6 years and infant pulmonary function tests for younger patients, if available. Complete blood count (CBC), sedimentation rate, C-reactive protein (CRP), electrolytes, prothrombin time (PT), and partial thromboplastin time (PTT) are also obtained.

 

DIFFERENTIAL DIAGNOSIS

Infantile scoliosis

Congenital scoliosis without rib fusion

 

Scoliosis associated with arthrogryposis

 

 

NONOPERATIVE MANAGEMENT

 

 

Observation with serial radiographs is indicated for mild or even moderate curves. Bracing is ineffective for congenital scoliosis.

 

Progression requires operative intervention.

 

 

P.836

 

 

 

 

FIG 3 • A dynamic lung MRI was performed and showed complete absence of rib cage expansion in inspiration and marked decrease in downward excursion of each respective hemidiaphragm during respiration.

 

SURGICAL MANAGEMENT

 

VEPTR expansion thoracoplasty is indicated for patients skeletally immature, as young as age 6 months, with progressive congenital scoliosis associated with fused ribs when the space available for lung (SAL) is less than 90%.

 

Patients unable to tolerate repetitive surgeries for later expansion of devices may not be suitable candidates for this procedure.

 

Absence of proximal ribs for device attachment also may be a contraindication for this procedure.

 

Preoperative Planning

 

For operative candidates, a trispecialty approach is highly recommended, with evaluation by not only by an orthopaedist but also a pediatric general surgeon and a pediatric pulmonologist, to best evaluate the multisystem abnormalities common for these complex congenital scoliosis cases.

 

 

The central question to address is whether expansion of the thorax with the likelihood of lung growth will provide a clinical benefit for the patient.

 

Anesthesia consultation preoperatively is also recommended. Any concerns raised by any of the

consultants should be addressed preoperatively.

 

Spinal cord abnormalities, such as tethers and diastematomyelia, should be addressed neurosurgically at least 6 weeks prior to VEPTR surgery to minimize the risk of traction to the spinal cord during the VEPTR procedure.

 

Significant gastric reflux may require fundoplication before VEPTR surgery.

 

Any coagulation disorders diagnosed that need treatment for surgery should be monitored by hematology services. Upper airway abnormalities may need scope-assisted operative intubation.

 

Positioning

 

The patient is placed in a prone position with longitudinal chest rolls. The knees and ankles are padded by foam pads.

 

A 2-inch strip of cloth adhesive tape is placed transversely across the pelvis (FIG 4), with a folded hand towel underneath it to protect the skin, and the ends of the tape are secured beneath the operating room (OR) table to provide gentile stabilization of the torso.

 

Arms are extended 90 degrees anteriorly and padded with foam pads.

 

Approach

 

Approach is through a modified thoracotomy incision.

 

 

 

 

FIG 4 • The patient is placed in a prone position, with longitudinal chest rolls to support the torso. Knees and ankle are supported by rolls and foam pads. Stabilization is through cloth tape over the buttocks across a hand towel secured under the OR table.

 

TECHNIQUES

• Opening Wedge Thoracoplasty

Exposure

A modified thoracotomy incision is made with the distal portion carried anteriorly in line with the 10th rib. Dissection with cautery continues through the muscle in line with the skin incision.

 

 

The interval between the ribs and the scapula is opened by blunt dissection.

 

The insertion of the middle and the posterior scalene muscles on the second rib is identified. The neurovascular bundle is just anterior to this landmark and should be avoided.

 

The paraspinal muscles are reflected medially to the tips of the transverse processes, with care taken not to damage the rib periosteum.

 

The proximal ribs for VEPTR attachment are assessed by palpation for strength, usually the second and third ribs are adequate.

Implantation of the Proximal Rib Cradle

 

The superior rib cradle of the VEPTR II (Depuy-Synthes Spine Co., Raynham, MA) is now ready for insertion.

 

Cautery is used to place shallow 1-cm transverse incisions in the midportion of the intercostal muscles above and below the ribs of attachment.

 

For best mechanical advantage, it should be placed adjacent to the tips of the transverse processes of the spine, around at least two ribs or a fused rib mass.

 

A Freer elevator is used to encircle the rib attachment to strip away the medial periosteum/pleural layer. The VEPTR trial is used to widen the soft tissue tunnel.

 

P.837

 

The VEPTR cradle cap is inserted in the superior incision facing laterally to avoid mediastinum structures then turned distally.

 

 

 

The VEPTR II rib cradle is next inserted, the two mated, and then locked by a distraction lock. When the two ribs or the fused rib mass is somewhat large, the extended cradle cap is used. The multiple rib attachment VEPTR II “stacked cradles” construct is seldom practical for this

procedure.

 

For very small children, the small stature rib cradles can be used.

 

The attached cradle is tested for stability.

 

If doubtful, include another rib distally to enhance strength.

 

Never extend to include the first rib because this may increase the risk of impingement of the device on the brachial plexus.

Thoracostomy

 

Once the superior attachment site is complete, the opening wedge thoracostomy can be performed at the apex of the fused chest wall.

 

Usually, there is a fibrous cleft present anteriorly in the fused ribs in line with the planned thoracostomy.

 

This is released with cautery, with a no. 4 Penfield retractor inserted to protect the underlying pleura, and then the thoracostomy is continued with a Kerrison rongeur, cutting a channel transversely through the rib fusion mass up to the transverse processes of the spine (TECH FIG 1A).

 

 

 

TECH FIG 1 • A. The opening wedge thoracostomy is cut from lateral to medial, with a no. 4 Penfield underneath protecting the lung. B. Distal attachment sites can be the lower ribs in a rib-to-rib VEPTR construct or to the proximal lumbar spine or the iliac crest for a VEPTR hybrid.

 

 

The osteotomized interval is then expanded with small lamina spreaders, and a Kittner sponge in a clamp is used to gently strip the pleura down proximal and distal.

 

Any bone bridge remaining medial is carefully resected with a rongeur with fused bone adjacent to the spine carefully pulled out laterally with a curved curette to avoid trauma to the spinal cord.

 

A second opening wedge thoracostomy, paralleling the first more distally, may be necessary when there is broad expanse of fused ribs.

 

The opening wedge thoracostomy is held open with a VEPTR II set rib retractor and the distal attachment sites are selected (TECH FIG 1B).

Distal Attachment Site

 

In patients older than 18 months, the spinal canal is adequate for a laminar hook, so either a proximal lumbar spine hook insertion is chosen for primary thoracic curves or an iliac crest S-hook insertion when there is lumbar spinal curve/pelvic obliquity.

 

In patients younger than 18 months, a hybrid VEPTR II use is not practical because the spinal canal is too small for a spinal hook,

 

P.838

so a single rib-to-rib VEPTR II device is implanted on the distal ribs just adjacent to the spine.

 

 

 

TECH FIG 2 • A rib-to-rib VEPTR II construct.

 

 

An inferior VEPTR II cradle site is prepared on a stable, relatively horizontal rib, usually the 9th or 10th rib, and then the VEPTR II is implanted and tensioned (TECH FIG 2).

 

In patients older than 18 months, a hybrid VEPTR II from ribs to proximal lumbar spine is used for more robust correction.

 

For the distal hook site, a longitudinal skin incision is made at the selected level of the lumbar spine, usually L2-L3, and a two-level unilateral exposure is made for insertion of a single lamina hook.

 

Care is taken to be below any areas of junctional kyphosis.

 

If there is considerable pelvic obliquity/lumbar curve, extending the hybrid VEPTR to the iliac crest is recommended.

Rib Sleeve and Lumbar Extension Implantation

 

With the hemithorax deformity corrected by the rib retractors across the thoracostomy, the hybrid VEPTR II size is chosen.

 

In general, 2 cm of proximal rod of the VEPTR II rib sleeve is needed to mate with the superior cradle, but if there is considerable kyphosis, a longer proximal rod segment is needed so that it can be bent to accommodate the deformity.

 

The expandable portion of the hybrid rib sleeve should end at the lower end of T12 and the lumbar extension spinal rod should be cut to extend distally 1.5 cm past the lumbar hook.

 

To form a tunnel in the paraspinal muscles for the device between incisions, a Kelly clamp is threaded from the proximal incision into the lumbar incision and used to pull a no. 20 chest tube back into the proximal wound.

 

The assembled and sized VEPTR II, distraction lock in place, is threaded into the chest tube proximally, and the tube is used to guide the device into the distal wound through the soft tissue tunnel.

 

The distal rod is then threaded through the closed hook, and the proximal rod attached to the superior cradle, and the device is distracted.

 

The rib retractors are then removed.

 

The thoracostomy interval should remain distracted apart.

 

A second rib-to-rib VEPTR device, if needed, is usually placed in the posterior axillary line (TECH FIG 3A).

 

The medial hybrid VEPTR II device is distracted a final time.

 

Extending the lumbar extension to the iliac crest is performed in a similar fashion (TECH FIG 3B).

Closure

 

Closure is in the usual thoracotomy fashion, but first, the musculocutaneous flaps are stretched to perform closure without tension (TECH FIG 4A).

 

A chest tube can be used if there is a large pleural leak on Valsalva maneuver with irrigant in the chest, but this is seldom the case.

 

Two round Jackson-Pratt drains are placed, along with a deep pain catheter for ropivacaine infusion postoperatively.

 

Weight-bearing AP and lateral spine radiographs are taken within the week after surgery (TECH FIG 4B).

 

 

P.839

 

 

 

TECH FIG 3 • A. Implantation of rib sleeve/lumbar extension. B. Implantation of VEPTR II hybrid to pelvis.

 

 

 

TECH FIG 4 • A. The skin/muscle flaps are stretched vigorously for at least 10 seconds. B. Immediate postoperative radiograph of the 2 1/2-year-old female treated with opening wedge thoracostomy and a hybrid VEPTR I, which had more expansion capability than a VEPTR II for the limited area where it had to be placed, and a rib-to-rib VEPTR II. The medial hybrid VEPTR could not be placed more proximally

because of poor bone stock.

 

 

 

• Vertical Expandable Prosthetic Titanium Rib Lengthening

P.840

 

The devices are lengthened on schedule at least twice a year in outpatient surgery (TECH FIG 5A).

 

Device expansion access is through 3-cm skin incisions, the distraction locks are removed, and the devices are extended slowly over several minutes, stopping when the reactive force is excessive.

 

A new distraction lock is inserted.

 

Expansion can be as minimal as 0.5 cm in a very tightly constricted chest and as much as 2.0 cm when the patient has had a growth spurt.

 

 

 

TECH FIG 5 • A. VEPTR lengthening. A 3-cm incision is made parallel to the distraction lock, the lock removed, and the device lengthened until the reactive force mounts rapidly, then the device is locked. B. Five-year follow-up. To improve longitudinal expansion of the constricted hemithorax, a second opening wedge thoracostomy was performed 2 years after implant with more proximal positioning of the rib cradle because of improved bone stock.

 

 

Lengthening continues through skeletal maturity, with replacement as needed of completely expanded device through limited incisions proximal and distal.

 

Infrequently, a second opening wedge thoracostomy may be needed (TECH FIG 5B).

Kyphosis Correction

 

When the proximal rods of the VEPTR II are bent to accommodate kyphosis, during lengthening procedures, the rods can be accessed through separate incisions and straightened slightly by in situ benders to reduce the kyphosis (TECH FIG 6).

 

This can be repeated as much as needed.

 

TECH FIG 6 • Kyphosis correction. During a lengthening procedure, separate 2-cm incisions are made parallel to the middle of the proximal rods of the VEPTR II; the rods bent into kyphosis are gently straightened until the reactive force increases significantly. This can be done at each lengthening until the kyphosis is substantially reduced.

 

 

 

PEARLS AND PITFALLS
	Inadequate ▪ Correction in the initial implant surgery cannot be addressed by expanding the correction of devices later, so every effort should be made to completely correct the the thoracic asymmetry between the concave and convex hemithorax with the initial deformity procedure.     Poor soft ▪ Diet supplementation, along with an oral appetite stimulant such as Periactin, tissue may be adequate. If not, tube feedings or gastric percutaneous endoscopic coverage for gastrostomy (PEG) feedings are useful. A body weight at the 25th percentile of devices normal, or greater, reduces the risk of skin slough over devices. preoperative     Iatrogenic ▪ The superior VEPTR cradle site should be placed at the superior aspect of the proximal curve but not into the flexible spine above it because of the risk of a proximal compensatory compensatory curve. curves     Acute ▪ Rare but can be encountered with closure because of the altered proximal thoracic outlet thoracic anatomy, so both pulse oximeter and upper extremity evoked potentials are monitored for loss of signal, and any changes are addressed by altering

 

	syndrome closure to let the scapula retract itself more proximal.

 

 

 

P.841

POSTOPERATIVE CARE

 

Most patients can be extubated soon after surgery.

 

 

There is a 50% risk of a transfusion because of the dead space beneath the large flaps created.

 

The chest tube, if present, is removed when drainage is less than 1 mL/kg/day, and the round Jackson-Pratt drains are removed when the drainage for each is 20 mL or less per day.

 

No bracing is necessary.

 

Patients are mobilized to ambulation as soon as tolerated.

 

Postoperative assessment should include standing AP and lateral radiographs of the spine.

 

 

OUTCOMES

For VEPTR treatment of fused ribs and congenital scoliosis, the average scoliosis curve was 74 degrees preoperatively and 49 degrees at postoperative follow-up.3

The ratio of the radiographic height of the concave lung divided by the height of the convex lung, the SAL, improved from 63% to 80%.

Mean increase in height of the thoracic spine was 0.71 cm per year. Patients who underwent surgery before age 2 years did best in percentage of predicted forced vital capacity (FVC).

Complications included device infection (1.9 % per procedure), skin slough (18 % of patients), and asymptomatic migration of devices (32% of patients).

Once the patients have reached skeletal maturity, the VEPTRs controlling the spinal deformity can be removed and a definitive spine fusion performed.

VEPTR devices stabilizing rib cage deformity should be retained.

Yearly follow-up with radiographs and pulmonary function studies are recommended.

Magnetic expansion capabilities for the VEPTR device, much like the MAGEC growing rod, will likely be available in the near future.

 

COMPLICATIONS

Infections can be resolved most of the time by débridement and irrigation with loose approximation of the wound to allow granulation tissue to cover devices and wound vacuum-assisted closure (VAC) treatment.

Recurrent infections are best addressed by temporary removal of the central portion of the devices, with reinsertion done once the infection is resolved.

Skin slough is treated by débridement, usually rotational muscle grafts, and primary closure.

Sometimes, it is necessary to use soft tissue expanders to provide skin coverage over the devices. Upward migration of the superior rib cradle can usually be addressed by reanchoring it to the reformed

 

rib of original attachment through a limited exposure, often done during regularly scheduled procedures.

Spinal hooks that have migrated distally can be reseated at a lower level. Spinal hooks migrating distally into the iliac crest can be removed and then reanchored onto the reformed iliac crest.

 

 

REFERENCES

1. Campbell RM Jr, Smith MD. Thoracic insufficiency syndrome and exotic scoliosis. J Bone Joint Surg Am 2007;89(suppl 1):108-122.

    

    

2. Campbell RM Jr, Smith MD, Mayes TC, et al. The characteristics of thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis. J Bone Joint Surg Am 2003;85:399-408.

    

    

3. Campbell RM Jr, Smith MD, Mayes TC, et al. The effect of opening wedge thoracostomy on thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis. J Bone Joint Surg Am 2004;86:1659-1674.

    

    

4. Maisenbacher MK, Han JS, O'Brien ML, et al. Molecular analysis of congenital scoliosis: a candidate gene approach. Hum Genet 2005;116: 416-419.

    

    

5. Oakes DF. Neonatal/Pediatric Respiratory Care: A Critical Care Pocket Guide, ed 2. Old Town, ME: Health Educator Publications, 1994.

    

    

6. Pehrsson K, Larsson S, Oden A, et al. Long-term follow-up of patients with untreated scoliosis. A study of mortality, causes of death, and symptoms. Spine 1992;17:1091-1096.

    

    

7. Skaggs DL, Sankar WN, Albrektson J, et al. Weight gain following vertical expandable prosthetic titanium ribs surgery in children with thoracic insufficiency syndrome. Spine 2009;34:2530-2533.

    

    

8. Sparrow DB, Chapman G, Smith AJ, et al. A mechanism for gene-environment interaction in the etiology of congenital scoliosis. Cell 2012;149:295-306.