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Background
The vertical expandable prosthetic titanium rib (VEPTR) (“the titanium rib”) (Synthes Spine, West Chester, PA) has been used in expansion thoracoplasty to treat thoracic insufficiency syndrome (TIS) in children. In this procedure, the titanium rib is used as a chest wall distractor to directly treat segmental hemithorax hypoplasia from fused ribs by lengthening and expanding the constricted hemithorax, and improve the capacity of the underlying lung. In addition, the titanium rib may indirectly correct scoliosis in the young child without the need for spine fusion. Surgical alternatives to the titanium rib include in situ spinal fusion, implantation of plastic sheets, artificial ribs from cadaver donor ribs or autograft (rib sections split from contralateral ribs). However, unlike the titanium rib, these surgical procedures are static treatments and are not adaptable as the child grows.
The U.S. Food and Drug Administration (FDA) has granted a humanitarian use device approval for VEPTR for treatment of thoracic insufficiency syndrome (TIS) in skeletally immature patients. The FDA defines TIS as the inability of the thorax to support normal respiration or lung growth. The FDA notes that, for purposes of identifying potential TIS patients, the categories in which TIS patients fall are as follows:
According to the FDA, the VEPTR device should not be used under the following conditions:
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Absence of proximal ribs for attachment of the VEPTR;
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Absent diaphragmatic function;
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Age below 6 months;
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Age beyond skeletal maturity;
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Inadequate soft tissue for coverage of the VEPTR;
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Inadequate strength of the bone (ribs/spine) for attachment of the VEPTR;
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Infection at the operative site;
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Known allergy to any of the device materials.
Approval as a humanitarian use device was based on the results of a 14-year, prospective, multi-center clinical trial of the VEPTR device in 247 children with TIS between 6 months of age up to the age of skeletal maturity. Treatment with the VEPTR device was shown to maintain or improve the assisted ventilatory rating (AVR) scores in 92 % of patients, and the patient survival rate in the VEPTR clinical trial was 95.1 %. The FDA determined that the probable benefits associated with patients implanted with the VETPR device outweigh the risk present for this patient population. The FDA noted that TIS is frequently terminal with non-surgical treatment. The FDA noted that the ability of VEPTR to be expanded allows growth of the thoracic spine and lungs while controlling severe scoliosis. The use of the VEPTR may require a 6-week pre-operative period of halo traction.
Campbell et al (2004) reported on the outcome of VEPTR in 27 children (mean age of 3.2 years at time of surgery) with congenital scoliosis associated with fused ribs who were followed for a mean duration of 5.7 years. Interval pulmonary function studies were analyzed to determine trends with regard to changes in vital capacity in the period following treatment. Sixteen subjects had such interval studies, at a mean of 3.1 years (range of 2 to 6.7 years) post-operatively. The first post-operative test demonstrated a mean vital capacity of 0.679 L (range of 0.37 to 1.7 L), or 49 % (range of 33 % to 68 %) of the predicted normal vital capacity, whereas the mean vital capacity at the time of follow-up was 0.91 L (range of 0.51 to 2.1 L), or 47 % (range of 25 % to 66 %) of the predicted normal vital capacity. There was a total of 52 complications in 22 patients, with the most common being asymptomatic proximal migration of the device through the ribs in 7 patients.
Samdani et al (2009) examined bilateral use of the VEPTR attached to the pelvis as a novel treatment for children with severe, early onset scoliosis. A total of 11 children were included in this study. The authors conducted a retrospective review and collected the following data: clinical diagnosis, age at surgery, number of lengthening procedures, and complications. In addition, pre- and post-operative radiographs were reviewed to measure maximum Cobb angle (both thoracic and lumbar), thoracic height, total spine height as measured from T1 to S1, thoracic kyphosis (T2 to T12), and lumbar lordosis (L1 to S1). The average patient age at surgery was 71 months; the mean pre-operative thoracic Cobb angle was 81.7 degrees. This angle was corrected to 50.6 degrees immediately post-operatively, and this correction was maintained; at the most recent follow-up the curves averaged 58 degrees. Similarly, the pre-operative kyphosis (T2 to T12) angle measured 43 degrees pre-operatively, 23 degrees immediately post-operatively, and 37 degrees at the most recent follow-up evaluation. Patients underwent a total of 41 lengthening procedures (average of 3.7 lengthening procedures per patient), and overall spine length increased from 23.1 cm pre-operatively, to 27.3 cm immediately post-operatively, to 29.4 cm at the final follow-up (average of 25 months). Four (36.4 %) of the 11 patients experienced complications. This was a small study; its findings need to be validated by future studies.
Shah and colleagues (2009) stated that surgical correction is generally indicated as the primary form of management in children with severe early onset scoliosis. Even so, conservative, non-surgical treatment is always considered first, as surgical correction carries significant concomitant consequences, including but not limited to crankshaft phenomenon and, more importantly, inhibition of further spine, lung, and chest growth in skeletally immature patients. Fusionless surgical procedures assuage some of these risks, as they are characteristically associated with techniques necessitating spinal fusion. One device looks particularly promising in treating and managing severe early onset scoliosis -- the VEPTR is a device that was initially targeted toward children with TIS. Despite its promising results in correction of severe early onset scoliosis, as well as associated rib and chest wall deformities, the VEPTR nevertheless has a complication rate comparable to other fusionless techniques. Continued modifications and research will hopefully beget a device that permits thoracic and spinal growth in skeletally immature patients yet with fewer post-operative complications.
In a retrospective study, Smith et al (2009) reviewed their experience in treating patients with idiopathic infantile scoliosis (IIS), especially as newer technologies, such as the VEPTR, emerge. These investigators reviewed 31 consecutive patients with a primary diagnosis of IIS. Patients were screened to ensure that there were no confounding congenital anomalies or co-morbidities that may have contributed to the spinal deformity. The average age at the time of initial treatment was 25 months. Treatment modalities included bracing, serial body casting, and VEPTR. Pre-treatment, post-treatment, and most recent Cobb angles were compared to assess the overall curve correction, and patient charts were reviewed for the occurrence of complications. Of the 31 patients, 17 were treated with a brace, 9 of whom had curve progression and went on to other forms of treatment. Of the 8 who did respond, there was an overall improvement of 51.2 %. The 10 patients who received body casts, who had a mean pre-operative Cobb angle of 50.4 degrees, demonstrated an average correction of 59.0 %, with only a few skin irritations reported. The 10 patients treated with VEPTR devices demonstrated a mean pre-operative Cobb angle of 90.0 degrees, and an average correction of 33.8 % was attained. Three of the VEPTR-treated patients (33 %) experienced minor problems. The authors concluded that these findings suggested that body casting has utility for patients with smaller, flexible spinal curves. Bracing had limited utility, with high levels of progression and the need for secondary treatments. The VEPTR device appears to be a viable alternative for large-magnitude curves.
Reinker and colleagues (2011) examined if VEPTR controls progression in patients with kyphoscoliosis and, if so, what methods might be used to improve control of deformity progression in these patients. These researchers retrospectively reviewed 14 patients who had VEPTR treatment of early-onset kyphoscoliosis. Degrees of kyphosis and scoliosis before, during, and after treatment were measured, and levels of instrumentation, thoracic dimensions, and complications were recorded. Minimum follow-up was 1.7 years (average of 5.8 years; range of 1.7 to 12.8 years). While scoliosis was stabilized, kyphosis increased a mean of 22° at last follow-up. Supple kyphosis became rigid during treatment. Proximal cradle cut-out was a recurring problem. Distal anchors placed too proximally had inadequate lever arms to control kyphosis. The authors concluded that progression of kyphosis can be minimized during VEPTR treatment by early extension of the construct to the second ribs bilaterally, distal extension of hybrid constructs to the pelvis, use of bilateral hybrid VEPTR implants, and use of re-designed VEPTR constructs that enhance fixation at the upper end. They noted that while these early findings suggest these devices control progression of kyphosis, longer follow-up with more patients are needed to confirm the concept in these patients.
Gadepalli and colleagues (2011) noted that VEPTR insertion and expansion has been advocated to increase thoracic volume and pulmonary function in patients with TIS. These investigators reviewed their experience with VEPTR implantation to determine if lung function and growth is augmented, to determine the children's functional status, and if the scoliosis is controlled. From 2006 to 2010, 29 insertions and 57 expansions were performed in 26 patients at the authors' institution. Demographic data were reviewed in conjunction with complications, scoliosis angles, pulmonary function tests (PFTs), and computed tomography-guided 3D reconstructions to determine lung volumes; and quality of life scores were determined using a modified Scoliosis Research Society (SRS) questionnaire pre-operatively and post-operatively. The groups were also stratified by age (because of lung growth potential), disease (congenital or infantile scoliosis, Jeune syndrome, neuromuscular, other structural thoracic disorders), and sex. Analyses using SPSS (SPSS, Chicago, Ill) were performed with p < 0.05 considered significant. Each patient underwent 3.03 ± 1.8 surgeries, spending 0.97 ± 1.8 days in the intensive care unit and 4.41 ± 6 days in the hospital for each procedure. Mean age was 90.7 ± 41 months. Of the 36 complications, most were because of infection (n = 12), half requiring operative repair (hardware removal). The average PFT percent predicted values for forced expiratory volume in 1 second, forced vital capacity, and RV were 54.6 ± 22, 58.1 ± 24, and 145.3 ± 112, respectively, pre-operatively and 51.8 ± 20, 55.9 ± 20, and 105.6 ± 31, respectively, post-operatively. The lung volumes measured by computed tomography when corrected for age do not increase significantly post-operatively. The mean Cobb measurement for the pre-operative major curves was 64.7° and post-operatively was 46.1° for those curves measured pre-operatively, for a 29 % curve improvement. All post-operative curves had a mean of 56.4° and 58.1° at final follow-up, a 3 % curve increase. The SRS scores for patients remained unchanged and no statistical difference was seen from pre-operative to post-operative values. No statistically significant difference was seen in complications, PFT (forced expiratory volume in 1 second, forced vital capacity, RV), lung volumes, scoliosis angles, and SRS scores between sex, age, and disease categories. The authors concluded that there was mild improvement in scoliosis angles but no improvement in lung function and volume. Scoliosis Research Society scores indicated that the children have near normal function both before and after VEPTR placement. Pulmonary function, lung volume, and patient subjective assessments did not increase dramatically after VEPTR placement, although scoliosis angles improved.
Lieber et al (2012) noted that various surgical techniques have been described for repair of chest wall defects in Poland syndrome. These investigators described the case of a 16-year old boy who underwent autologous rib transposition after sternal osteotomy. Chest wall stabilization was achieved using a combination of K-wires and VEPTR. Reconstruction of the soft tissue defect was accomplished by combined latissimus dorsi muscle flap and Permacol patch. This approach might be considered an effective 1-stage treatment option of this condition in post-pubescent boys. The findings of this case study need to be validated by well-designed studies.
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