Abstract
Introduction
Conventional growing systems allow spinal growth to continue and prevent curve progression but need multiple interventions that increase the risk of infection, complications of anesthesia. A more advanced, less invasive method is the remotely distractible, magnetically controlled growing rod (MCGR) system which has been developed to allow frequent non-invasive distractions. This is the first series focusing on the conversion of failed growing implant to MCGR.
Materials and Methods
A prospective single center study from 11/2012 to 8/2015 with consecutive patients with progressive deformity and implant failure. Five children have been converted to MCGR; one boy and 4 girls; mean age 11.9 years. The scoliosis was infantile in two and neuromuscular in 3 cases. Four patients had VEPTR and one had a conventional growing rod.
Results
Mean preoperative Cobb angle was 56.6°, thoracic kyphosis 59.6° and spinal length (T1-S1) 339mm. The upper fixation level was T3-T5 with a lower fixation to T11 and L2 in the infantile scoliosis and L3 in two neuromuscular cases. One neuromuscular scoliosis was fixed with hooks to the iliac crest. Mean operative time was 135 minutes and blood loss 217 ml. Mean postoperative Cobb angle was 48.1°, thoracic kyphosis of 49.8% and spinal length 379mm. During this study a total of 15 distractions have been performed to all children. At final FU (mean of 21.8m), mean Cobb angle was 48° (total additional correction of 2.5°), thoracic kyphosis of 51.5° (total additional correction of 3.2°) and spinal length of 387 mm (total spinal growth of 33 mm). One case reached to final fusion after 2 distractions. Double rods have been the rule with exception of one neuromuscular case. This single rod was broken after 6 months and replaced by a double rod system. The other complication was a proximal junctional kyphosis (PJK) that occurred primarily after VEPTR and again after magnetic rod.
Conclusion
Although conversion of implant failure from VEPTR and growing rod systems to MCGR is a good option to allow growth of the instrumented segment, this gives limited results when performed at a relatively older age. The postoperative correction in these cases is relatively limited due to prior correction by the older systems. One complication related to the implant occurred with single rod construct. Correction by MCGR will face the same challenge to prevent PJK, like other growing rod systems. The new technique provided a non-surgical repeated (sometimes outpatient) distractions.