The Role of Vertebral Body Tethering in Treating Skeletally Immature Scoliosis

Growing rods in Early Onset Scoliosis: The current scenario

Background and aims

The treatment of early onset scoliosis is a challenge. Some curves resolve spontaneously, while the more aggressive ones require surgical intervention. Several surgical strategies have been explored in this unique group of patients, though the distraction based growing rods are the mainstay of treatment. The aim of this paper is to consider the current scenario with the surgical treatment for early onset scoliosis with growing rods.

Methods

This is a narrative review that explores the various types of growing rod options that are currently available. The results, as reported in literature, are discussed. The complications and problems with the commonly used growing rods are explored, based on the reported literature and on retrieval analysis that we have published. We discuss some of the newer modifications of growing rods.

Results

There is no real consensus on the ideal timing for the surgery or ways to assess the outcomes of the treatment. The Cobb angle measurement and measures of thoracic growth are surrogate markers. The main indication for surgery is to an increase in the thoracic dimensions and allowing for lung growth. Measures that are linked to lung function are more useful. We report some newer MRI scanning technology. Distraction-based growing rods have been reported to produce consistent and good results. Frequent return to theatre with the Traditional Growing Rods (TGR) and the metallosis related problems with the MCGR are reported.

Conclusions

We have learned a lot from the TGR and MCGR experiences. There is a scope for ongoing research to improve the design of the implant systems and better assess the outcomes on lung function. This review outlines these and helps identify the future trends.

The timing of tether breakage influences clinical results after VBT

INTRODUCTION

Tether breakage is a frequent mechanical complications after vertebral body tethering (VBT), but not all patients with a breakage show loss of correction. The reason of this clinical finding has not yet been clarified. We hypothesized that the integrity of the tether is relevant only in the early stages after VBT, when it drives growth modulation and tissue remodelling. After these mechanisms have taken place, the tether loses its function and a breakage will not alter the new shape of the spine. Thus, tether breakage would have a greater clinical relevance when occurring shortly after surgery.

METHODS

All consecutive patients who underwent VBT and had a min. 2-year follow-up were included. The difference in curve magnitude between the 1st standing x-ray and the last follow-up was calculated (ΔCobb). For each curve, the presence and timing of tether breakage were recorded. The curves were grouped according to if and when the breakage was observed (no breakage, breakage at 0-6 months, 6-12 months, > 12 months). The ΔCobb was compared among these groups with the analysis of variance (ANOVA).

RESULTS

Data from 152 curves were available: 68 with no breakage, 12 with a breakage at 0-6 months, 37 at 6-12 months and 35 > 12 months. The ANOVA found significant difference in the ΔCobb among the groups (Sum of square 2553.59; degree of freedom 3; mean of square 851.1; Fisher test 13.8; P < 0.0001). Patients with no breakage or breakage at > 12 months had similar ΔCobb (mean 4.8° and 7.8°, respectively, P = 0.3), smaller than the 0-6 or 6-12 groups (15.8° and 13.8°, respectively).

CONCLUSION

Tether breakage leads to a consistent loss of correction when occurring within the first 12 months, while it has limited clinical relevance when occurring later on.