Vertical expandable prosthetic titanium rib (VEPTR) implants may be used in children with severe spinal deformities during the growth period before definite spinal fusion. The purpose of this study was to evaluate spinal deformities before, during and after VEPTR treatment, with special focus on potential differences between congenital and neuromuscular scoliosis.
Retrospective cohort study on a population of 15 children with a continuous documentation starting before VEPTR treatment and ending with the removal of hardware prior to spinal fusion. Radiologic measurements of scoliosis and of pelvic obliquity were performed in anteroposterior radiographs, while kyphosis, lordosis and spinal length were evaluated in lateral radiographs. Measurements were conducted before and after initial VEPTR implantation, in two years intervals during VEPTR treatment as well as before and after final VEPTR explanation.
Initial implantation of VEPTR was able to significantly reduce the main curve, which increased again over time. However, scoliosis in children with congenital spinal deformity remained stable after implant removal, whereas neuromuscular scoliosis showed a significant deterioration of the main curve immediately after VEPTR removal. Bending films pre VEPTR and after explanation showed 50% and 24% curve flexibility, respectively. The primary achieved correction of pelvic obliquity remained unchanged after implant removal in patients with congenital scoliosis, but deteriorated in neuromuscular children.
After removal of long-standing VEPTR implants, spinal deformity in children with congenital scoliosis remained unchanged, suggesting an observing approach in the future. Bilateral VEPTR treatment using rib-to-pelvis constructs without touching the spine preserved some spinal flexibility in children with neuromuscular scoliosis.
Level of Evidence
Therapeutic Level IV
Progressive spinal deformity in children often requires early and repetitive surgical treatment. In the last decades, several growth-friendly devices such as vertical expandable prosthetic titanium rib (VEPTR) implants [1, 2], magnetically controlled devices [3, 4], growing rods [5, 6] and other growth-guided implants [7, 8] have been used to achieve this goal. However, the majority of these constructs serve as interim solutions, requiring definitive spinal fusion in puberty . Recently, several problems connected with these pediatric implants have been reported [10–13]. Many of these devices may lead to stiffness of the spine due to auto fusion and ossifications, thus making the definitive spinal fusion more complex [9, 10]. Additionally, this may also lead to a longer fusion area than initially assumed. Another major problem poses the recently identified asymptomatic bacterial colonization of the implant [12, 13]. Routinely, growth-friendly implants are removed at the same surgery as definitive spinal fusion. If bacteria colonizing the growth-friendly implants infect the final spondylodesis devices, severe local infection with multiple surgeries, septicemia and potentially life-threatening events may occur . To avoid the latter complications, juvenile patients had their definitive spinal fusion in average 8 months after explanation of long-standing VEPTR devices allowing analysis of the flexibility of spinal deformity after VEPTR treatment. In this group curve pattern changes were analyzed focusing on the behavior of frontal and sagittal profiles in adolescents with neuromuscular or congenital scoliosis after VEPTR treatment.
Material and Methods
In accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration, we conducted a retrospective case study on children who underwent surgical implantation of VEPTR implants, several expansion surgeries and removal of VEPTR implants before final fusion. Fifteen patients met the inclusion criteria, which comprised (1) diagnosis as either neuromuscular or congenital scoliosis (2) evident indication for a surgical intervention and (3) complete documentation of VEPTR treatment from the point before intervention to removal of implants. Twelve patients received definite spinal fusion after VEPTR treatment. Patients underwent implantation of VEPTR devices between ribs and the lumbar spine with a second lateral implant from rib-to-rib or bilateral devices between ribs and the pelvis. Repetitive expansion surgeries were performed approximately every six months. Clinical data such as gender, diagnosis, age at initial VEPTR implantation, type of construct and ability to walk were obtained. Measurements of digitally available radiographs were performed using the radiologic processing program Centricity (GE Healthcare). All radiographs matching the following criteria were analyzed: standing or sitting anteroposterior, lateral and bending radiographs pre- and post-VEPTR implantation, anteroposterior and lateral radiographs in two-year-intervals during VEPTR treatment as well as pre and post VEPTR removal at the latest possible follow-up. Again, after final implant removal bending films were obtained. Measurements of the Cobb angle  of the main curve (mainly thoracic or thoracolumbar) and the associated cranial (mainly cervical) and caudal (mainly lumbar) curve and pelvic obliquity were conducted in every anteroposterior radiograph. Curve angles on bending film were also obtained. In the lateral radiographs, measurements of the kyphosis and lordosis and spinal length were performed. For the latter, the distance between the center of T1 and the sacrum was measured. Pelvic obliquity was measured by evaluating the angle between a horizontal line and a straight line between the iliac crests. For evaluation of inter-observer errors, all measurements were done by two independent investigators. The acquired data were analyzed statistically using the computer program Statistica 13.0 (Dell, USA). Analysis of variance and post-hoc tests were adopted. All data are presented as mean ± standard error of the mean and statistical significance was defined with levels as p<0.05 (*), p<0.01 (**) and p<0.001 (***).
Data of 15 scoliotic children (12 female, 3 male) were reviewed pre and post VEPTR implantation, half-time of VEPTR treatment (average 2.9 years), last measurement with the VEPTR devices implanted (average 5.5 years) and latest examination after removal of all VEPTR implants (average 6.3 years). In the ten cases of neuromuscular scoliosis, diagnosis was spinal muscular atrophy, cerebral palsy and type-IV collagen deficiency. All of them were non-ambulatory. The mean age of this group at initial VEPTR surgery was 8.7 years. The five cases of congenital scoliosis had typical vertebral body malformation with unilateral unsegmented bars, failure of formation and segmentation as well as fused ribs. All of them were able to walk. Their mean age at VEPTR implantation was 4.3 years (figure 1). Patients were treated with rib-to-lumbar spine implants (n=6), bilateral rib-to-pelvis implants (n=7), or had device conversions from the first to the second VEPTR construct (n=2) (table 1).
The main curve was corrected from mean angles of 72° (congenital) and 52° (neuromuscular) prior to VEPTR treatment to 48° (p=0.024) and 37° (p<0.001) respectively immediately after surgery (figure 2). This correction was maintained during the first 2.9 years, but deteriorated again to 61° and 49° at the 5.5 years follow-up. In neuromuscular children, the main curve increased significantly (p<0.001) directly after VEPTR explanation, whereas this curve remained stable in congenital scoliotic patients after VEPTR removal. Furthermore, analyzing the bending films pre implantation and after removal of the implants in ten children, a correction of the main thoracic curve of 50% (67.7° to 36°) could be initially achieved versus 24% (77.7° to 59.3°) correction, respectively (p=0.06).
Development of pelvic obliquity displayed significant differences between congenital and neuromuscular children. Children with congenital scoliosis did not have a relevant pelvic obliquity and this did not change throughout the treatment (figure 3). In children with neuromuscular scoliosis, pelvic obliquity was initially corrected by VEPTR implantation (from 12° to 4°) and during the first follow-up (5°). However, longer follow-up (8°) and explanation of VEPTR devices (9°) diminished the positive effects on pelvic position.
Kyphosis and lordosis
In the sagittal plane, kyphosis measured around 45° for both patient groups before the first surgery. Kyphosis could not be reduced by spinal implantation, but instead even worsened during VEPTR treatment exceeding baseline values during follow-up. Lordosis values averaged 36° prior to surgical intervention. Again, VEPTR treatment failed to achieve any correction in both patient groups either directly after surgery or during follow-up. In contrast to kyphosis values, lordosis remained on a constant level.
The spinal length averaged 262 mm for congenital and 287 mm for neuromuscular patients before surgery. For congenital scoliosis, spinal length increased steadily in the course of VEPTR treatment representing roughly a normal growth curve. In contrast, children with neuromuscular scoliosis experienced a sudden increase (32 mm) of spinal length immediately upon VEPTR surgery, but had an unchanged curve thereafter.
Distraction based spinal implants such as the VEPTR device are commonly used in children with spinal deformities and thoracic insufficiency syndrome. Several studies have shown that implantation and repetitive lengthening of VEPTR implants achieve correction of the scoliotic curves [1, 16–19], as well as possibly improve thoracic insufficiency syndrome  and support spinal growth in congenital scoliosis . In these children, definite spinal fusion remains the standard surgical treatment endpoint at puberty. Most clinicians perform VEPTR removal and definitive spondylodesis within one surgery. However, recent data suggest a two-staged procedure with at least some weeks in between when converting from the VEPTR system to spondylodesis to minimize implant-transmitted infection from one to the other implant system [12, 13]. To our knowledge, there are no studies available regarding the changes in spinal deformities after VEPTR explanation. Therefore, we observed spinal curve changes in children with long-standing VEPTR implants after explanation and prior to definitive spinal fusion.
Interestingly shown for the first time, the main curve of children with congenital scoliosis remained stable after removal of the VEPTR implants. In contrast, kyphotic deformity was poorly controlled over a long-term VEPTR treatment as described before [17, 19, 21]. However, kyphosis in congenital scoliosis did not progress after implant removal, thus suggesting an overall stiff spinal situation. In case of an acceptable kyphosis therapeutic management of congenital scoliosis after VEPTR removal should be reconsidered and possibly, congenital patients could be spared from subsequent spinal fusion surgery with the risk of severe complications. Spinal length increased slowly over time during VEPTR treatment as described previously . Contrary, neuromuscular patients experienced marked initial curve correction by VEPTR implantation and deterioration of scoliosis immediately after explanation reflecting the flexibility of neuromuscular spinal deformities. Analysing bending films pre VEPTR implantation and after removal, curve reduction reflecting spinal flexibility was 50% versus 24% respectively. Previously reported increased stiffness and limited correction potential over time in children with spinal deformity and growing rod treatment  does not seem to apply to the same extend to flexible scoliosis in neuromuscular patients with VEPTR devices. In these patients, this spinal “no-touch technique” is beneficial in order to prevent stiffness and auto fusion and to reduce the risks in definitive spinal fusion as described by Lattig et al. . Flexibility of neuromuscular spines was also confirmed by analysing the spinal length, which responded significantly to VEPTR implantation only in neuromuscular patients. The commonly seen increased pelvic obliquity in neuromuscular patients due to hip dislocation could be sufficiently controlled with bilateral VEPTR constructs and increased during long-term treatment and after implant removal Our study shows different outcomes of spinal deformities in congenital scoliosis compared to neuromuscular children after implant removal at the beginning of puberty. However, the reported data only base on a congenital subset of five and a neuromuscular subset of ten children and result from heterogeneous patient groups regarding age at VEPTR implantation, length of treatment and underlying etiology. Therefore, further studies analyzing different impact of treatment in neuromuscular and congenital patients might be helpful.
Bilateral VEPTR treatment without touching the spine retains spinal flexibility in children with neuromuscular scoliosis. In congenital scoliosis, however, spinal deformity remains unchanged after removal of long-time VEPTR implants, indicating an overall stiff spinal situation. In these cases, subsequent spinal fusion surgery should be reconsidered. Conflicts of Interest and Source of Funding Authors Andrea S Gantner, Lena Braunschweig, Konstantinos Tsaknakis, Heiko M Lorenz and Anna K Hell declare that they have no conflict of interest and no source of funding was received for this study.
Figure 1. Poster anterior (A-C) and lateral radiographs (D-F) of a 14-year-old girl with congenital scoliosis and a thoracic curve of 40 ° at the end of VEPTR treatment (A), which remained stable 4 months (B) and 16 months (C) after VEPTR removal.
Figure 2. Development of the main curve in patients with congenital (n=5, circles) and neuromuscular (n=10, squares) scoliosis pre and post VEPTR surgery, half-time of treatment, final measurement with VEPTR implant and after explanation of the VEPTR device. Data show the mean ± standard error of the mean and p-values refer to the pre-surgical value, if not indicated otherwise.
Figure 3. Development of pelvic obliquity in patients with congenital (n=5, circles) and neuromuscular (n=10, squares) scoliosis pre and post VEPTR surgery, half-time of treatment, final measurement with VEPTR implant and after explanation of the VEPTR device. Data show the mean ± standard error of the mean and p-values refer to the pre-surgical value.
Table 1 Overview of patient characteristics
1. Campbell RM Jr, Smith MD, Mayes TC, Mangos JA, Willey-Courand DB, Kose N et al. The characteristics of thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis. J Bone Joint Surg Am. 2003, 85–A(3): 399–408.
2. Campbell RM Jr, Smith MD, Hell-Vocke AK. Expansion thoracoplasty: the surgical technique of opening-wedge thoracostomy. Surgical technique. J Bone Joint Surg Am. 2004, 86–A Suppl 1: 51–64.
3. Akbarnia BA, Cheung K, Noordeen H, Elsebaie H, Yazici M, Dannawi Z et al. Next generation of growth-sparing techniques: preliminary clinical results of a magnetically controlled growing rod in 14 patients with early-onset scoliosis. Spine. 2013, 38(8): 665–670.
4. Cheung KM, Cheung JP, Samartzis D, Mak KC, Wong YW, Cheung WY et al. Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series. Lancet. 2012, May 26;379(9830):1967-1974.
5. Klemme WR, Denis F, Winter RB, Lonstein JW, Koop SE. Spinal instrumentation without fusion for progressive scoliosis in young children. J Pediatr Orthop. 1997, 17(6): 734-742.
6. Akbarnia BA, Marks DS, Boachie-Adjei O, Thompson AG, Asher MA. Dual growing rod technique for the treatment of progressive early-onset scoliosis: a multicenter study. Spine. 2005, 30: S46-57.
7. Latalski M, Fatyga M, Ko?towski K, Menartowicz P, Repko M, Filipovi? M. Guided-growth implants in the treatment of early onset scoliosis. A pilot study. Ortop Traumatol Rehabil. 2013, 15(1): 23-29.
8. McCarthy RE, Luhmann S, Lenke L, McCullough FL. The Shilla growth guidance technique for early-onset spinal deformities at 2-year follow-up: a preliminary report. J Pediatr Orthop. 2014, 34(1): 1–7.
9. Lattig F, Taurman R, Hell AK. Treatment of Early Onset Spinal Deformity (EOSD) with VEPTR: A Challenge for the Final Correction Spondylodesis: A Case Series. Clin Spine Surg. 2016, 29(5): E246-251.
10. Sankar WN, Skaggs DL, Yazici M, Johnston CE 2nd, Shah SA, Javidan P et al. Lengthening of dual growing rods and the law of diminishing returns. Spine. 2011, 36: 806–809.
11. Groenefeld B, Hell AK. Ossifications after vertical expandable prosthetic titanium rib treatment in children with thoracic insufficiency syndrome and scoliosis. Spine. 2013, 38: E819- 823.
12. Plaass C, Hasler CC, Heininger U, Studer D. Bacterial colonization of VEPTR implants under repeated expansions in children with severe early onset spinal deformities. Eur Spine J. 2016, 25(2): 549-556.
13. Wagner L, Braunschweig L, Eiffert H, Tsaknakis K, Kamin D, D’Este E et al. Detection of Bacteria Colonizing Titanium Spinal Implants in Children. Surg Infect (Larchmt). 2018,19(1):71-77.
14. Shah MQ, Zardad MS, Khan A, Ahmed S, Awan AS, Mohammad T. Surgical Site Infection In Orthopaedic Implants And Its Common Bacteria With Their Sensitivities To Antibiotics, In Open Reduction Internal Fixation. J Ayub Med Coll Abbottabad JAMC. 2017, 29: 50–53.
15. Cobb J. Outline for the study of scoliosis. Am Acad Orthop Surg. 1948, 261-275.
16. Emans JB, Caubet JF, Ordonez CL, Lee EY, Ciarlo M. The treatment of spine and chest wall deformities with fused ribs by expansion thoracostomy and insertion of vertical expand - able prosthetic titanium rib: growth of thoracic spine and im - provement of lung volumes. Spine. 2005, 30: S58-68.
17. Hasler C-C, Mehrkens A, Hefti F. Efficacy and safety of VEPTR instrumentation for progressive spine deformities in young children without rib fusions. Eur Spine J. 2010, 19(3): 400-408.
18. Wimmer C, Wallnoefer P, Pfandlsteiner T. [Operative treat - ment of scolioses with the VEPTR instrumentation]. Oper Or - thopadie Traumatol. 2010, 22(2): 123-136.
19. Samdani AF, Ranade A, Dolch HJ, Williams R, St Hilaire T, Cahill P et al. Bilateral use of the vertical expandable prosthetic titanium rib attached to the pelvis: a novel treatment for sco - liosis in the growing spine. J Neurosurg Spine. 2009, 10: 287- 292.
20. Campbell RM, Hell-Vocke AK. Growth of the thoracic spine in congenital scoliosis after expansion thoracoplasty. J Bone Joint Surg Am. 2003, 85–A(3): 409-420.
21. Gantner AS, Braunschweig L, Tsaknakis K, Lorenz HM, Hell AK. Spinal deformity changes in children with long-term ver - tical expandable prosthetic titanium rib (VEPTR) treatment. Spine J Off J North Am Spine Soc. 2017.