Thoracic Insufficiency Syndrome Laura Stoll November 2010

Normal thorax Spine + rib cage + sternum + diaphragm Lung development depends on thoracic growth Increase in T-spine height Symmetrical enlargement of rib cage through rib growth Correct orientation of ribs

Thoracic spine growth Birth-5 years: 1.4 cm/yr 6-10 years: 0.6 cm/yr Marked loss of T-spine height = severe reduction in thoracic volume for lungs Jarcho-Levin syndrome (spondylothoracic dysplasia) Single, short, block vertebra (1/4th normal height) High mortality due to respiratory complications Campbell RM, et al 2007; Ramirez N, et al

Rib contribution Birth - 2 years: 2 years-10 years: Ribs horizontal = growth of rib in length Increase in diameter of rib cage = square-shaped thoracic cross-section 2 years-10 years: Rib course downward = oval-shaped thoracic cross-section 10 years - skeletal maturity: Ribs grow rapidly = final rectangular shaped thoracic cross-section

Rib cage contributes to volume increase by expanding anteriolaterally - “buckethandle” biomechanism Diaphragm “piston” increases thoracic volume by downward excursion

Thoracic insufficiency syndrome Inability of the thorax to support normal respiration or lung growth Thoracic insufficiency syndrome does not equal respiratory insufficiency Dx based on H&P, imaging studies, V-P lung scans, PFTs, labs Campbell RM, et al 2003

Disorders of normal, stable thorax volume Causes extrinsic restrictive lung disease Scoliosis with absent or fused ribs Scoliosis with windswept deformity Jarcho Levine syndrome Jeune syndrome Jarcho Levin syndrome (multiple vertebral and rib fusion anomalies) Jeune syndrome (asphyxiating thoracic dysplasia)

AP and lateral chest radiograph of patient with Jarcho-Levin syndrome at 2 months of age shows crab-like chest appearance and limited bilateral lung aeration and multiple rib and vertebral body abnormalities. Jarcho-Levin Syndrome: symmetric "crab-like" chest that is caused by the ribs crowding and fusing at their origin at the spine and fanning out along their lengths. Can have various numbers and shapes of ribs as well as vertebral segmentation defects consisting of fusion or absence of vertebrae, hemivertebrae, and butterfly vertebrae. Mild scoliosis, secondary to the multiple hemivertebrae, is present in most patients.

Disorders of thorax’s ability to change volume CDH - decreased contraction of diaphragm Unilateral hemidiaphragm paralysis Anomalous insertion of the diaphragm in congenital scoliosis and rib anomalies Secondary thoracic insufficiency syndrome - torso collapsed on pelvis Campbell RM, et al 2004

This is a classification for thoracic volume-depletion deformities Developed by Robert Campbell on the basis of radiographs and CT studies of the thorax. Enables the surgeon to the best surgical approach. Type I and II: Asymmetric deformities, with unilateral volume-depletion deformities that require unilateral surgical expansion to restore thoracic volume and symmetry in the coronal plan. Type III deformities have a global thoracic volume deficit which may be due to either a symmetrical longitudinal constriction such as that in Jarcho-Levin syndrome or a symmetrical transverse-plane constriction such as that in Jeune asphyxiating thoracic dystrophy. Require bilateral staged surgical correction to either lengthen or laterally expand the symmetrically constricted thorax. Jarcho Levin syndrome (multiple vertebral and rib fusion anomalies, foreshortened thorax) Jeune syndrome (asphyxiating thoracic dysplasia) Campbell RM, et al 2007

Standard scoliosis: Thorax usually spacious, no rib cage deformities, near normal vital capacity Characterized by degree of curve on AP radiographs Tx: bracing or definitive spinal fusion

Exotic scoliosis Early onset Thorax distorted by spinal lordosis and curve rotation Often associated with rib-cage deformities: absent or fused ribs Volume depletion deformity and thoracic growth inhibition = adverse effects on lung growth

Can’t do conventional treatments (fusion): Bone stock may be insufficient Patient too small for standard implants for fusion Lung function may be too poor Will not address the 3D thoracic deformity Loss of growth of T-spine from early fusion would impact thoracic volume

VEPTR Vertical expandable prosthetic titanium rib Dr. Robert Campbell and Dr. Melvin Smith of Christus Santa Rosa Children’s Hospital in San Antonio, TX Received FDA approval in August 2004

Surgical Indications Rib fusion and progressive scoliosis Hypoplastic thorax syndrome Jeune’s syndrome Achondroplasia Jarcho-Levin syndrome VACTERL syndrome Flail chest syndrome Rib agenesis Acquired causes

Type I: Absent ribs and scoliosis Stabilization expansion thoracoplasty Stabilizes the flail chest-wall segment Laterally expands and lengthens the collapsed hemithorax section 2-3 VEPTR devices used

Fig. 5-A A four-year-old girl with type-I volume-depletion deformity from rib absence and scoliosis. Fig. 5-B The VEPTR stabilization expansion thoracoplasty lengthened and widened the constricted hemithorax and thereby increased the space available for lung to 90%, corrected the exotic scoliosis indirectly without growth inhibition, restored truncal balance, and corrected pelvic obliquity. Campbell RM, et al 2007

Type II - fused ribs and scoliosis Opening wedge thoracostomy Fused hemithorax is osteotomized transversely, lengthened until the thorax is equilibrated Those under 2 years old with no history spine surgery do best Campbell RM, et al 2007

Fig. 6-A 4yo boy with a type-II volume-depletion deformity resulting from fused ribs and scoliosis. The curve was 102ｰ, the space available for lung was 21% of normal, and the respiratory rate was elevated. Fig. 6-B VEPTR opening-wedge thoracostomy lengthened the constricted hemithorax by 200%, increasing the space available for lung to 64% of normal, reducing the curve to 45ｰ, and improving truncal balance and head tilt. Campbell RM, et al 2007

Type IIIa - Jarcho-Levin Syndrome Staged bilateral opening-wedge thoracostomies Rib-to-rib VEPTR devices Lengthen sequentially constricted hemithorax while correcting any associated scoliosis Campbell RM, et al 2007

Fig. 7-A A 3yo boy with a type-IIIa volume-depletion deformity from Jarcho-Levin syndrome. Fig. 7-B At the six-year follow-up, after staged bilateral VEPTR opening thoracostomies, growth of the thoracic spine and the thorax has occurred. Campbell RM, et al 2007

Type IIIb - Jeune syndrome or infantile scoliosis with windswept deformity Circumferential thoracic constriction Staged bilateral dynamic segmental curved VEPTR In windswept deformity scoliosis, concave chest is lengthened with opening-wedge thoracostomy, lengthening of hemithorax, stabilization with unilateral rib to spine or rib to pelvis VEPTR Campbell RM, et al 2007

Fig. 8-A An infant with a type-IIIb volume-depletion deformity from Jeune syndrome. Fig. 8-B After staged bilateral dynamic segmental posterolateral expansion thoracoplasties, improvement in the lateral width of the thorax is seen. Large segment of chest wall containing six to seven ribs is mobilized by rib osteotomies anteriorly near the costochondral junction and by osteotomies posteriorly just lateral to the transverse processes. Iatrogenic flail chest segment is acutely distracted outward, increasing thoracic volume and is attached by titanium slings to the VEPTR The diastasis betweent he osteomtoized ribs fills in with new bone and the new thoracic space fills in witth pleural effusion, but lung lucency is seen at about 6 months extending out. The second side is treated 3-6 months later. Periodic expansion continues to drive chest wall outward for continued gains in volume. Windswept: lysis of intercostal m.m. at the apex of the hemithorax constriction

VEPTR complications Prone to complications due to repetitive nature of maintenance surgeries Wound infection - 3.3% per procedure Skin slough Scarring Migration of fixation - 0.09 migrations/yr/pt Device breakage Brachial plexus injuries Campbell RM, et al 2007

Outcomes Improvement of percentile weight Decreased in ventilator dependence, increase in thoracic volume +/- increase in lung volume (and decrease in FVC) - benefit may lie more in stabilizing thorax and improving respiratory mechanics measured in other ways 10/21 patients had increased activity levels postoperatively Skaggs, et al; Campbell RM, et al 2007; Yazici, et al; Mayer, et al; Waldhausen, et al

Further defining thoracic insufficiency syndrome VEPTR new device. Long term follow-up studies still needed

References Campbell RM, et al. JBJS Am. 2003;85:399 Campbell RM, et al. JBJS Am. 2004;86Suppl1:51 Campbell RM, et al. JBJS Am. 2007;89-A:108 Mayer, et al. J Pediatr Orthop. 2009;29:35 Rameriz N, et al. JBJS Am. 2007;89:2663 Skaggs, et al. Spine. 2009;34:2530 Waldhausen JHT, et al. J Pediatr Surg. 2007;42:76 Yazici, et al. Spine. 2009;34:1800