29.1 Traditional Growing Rods

The techniques of three-dimensional correction and instrumentation for spinal deformities were introduced in Egypt in the late 1990s. A few years later, at Cairo University, surgeons started to learn and gain experience in instrumentation without fusion for the treatment of early onset scoliosis; most of this experience was acquired directly during training in the United Kingdom and from American spinal surgeons visiting spinal centers in Egypt. Experience remained limited to a handful of surgeons, and it took a while to convince the community of spinal physicians of the importance of growing rods as a valid safe and effective surgical treatment option for patients with early onset scoliosis.

The concept of the single submuscular rod was acquired from Hilali Noordeen, FRCS UK, and modified. The first construct used in Egypt had a proximal foundation consisting of an intrasegmental claw (proximal downward-facing transverse process hook and distal upward-facing facet hook) and a stainless steel sublaminar wire to increase stability and decrease the incidence of pullout failure; the distal foundation consisted of a single pedicle screw. The two rods, attached proximally and distally to the foundations, were connected via a longitudinal connector (tandem) with proximal and distal locking screws (Fig. 29.1). The second version of the single growing rod was acquired from David Marks, FRCS UK; the proximal foundation consisted of a double claw construct (claw in a claw) with double transverse process and double facet hooks, and the distal foundation consisted of adjacent pedicle screws (Fig. 29.2).

The results of the first series of patients who had early onset scoliosis treated with the single growing rod technique were published in 2005 in the Pan Arab Journal of Orthopaedics and Trauma. ¹ This was one of the first documented case series in the region on the use of growing instrumentation in early onset scoliosis. The study reviewed 12 patients with juvenile and infantile idiopathic early onset scoliosis, whose average age was 6 years and 2 months at the index surgery. The patients underwent surgery between 2001 and 2003; the average follow-up was 1 year and 10 months, and the average number of distractions per patient was 3.5. The wake-up test was routinely used. Three proximal hook pullouts and two rod fractures occurred.

This study was the basis for the first national recommendation and approval for centers and surgeons to start offering growing spine surgical treatment with serial distraction. The study concluded that growing rods could be a valid alternative for children with early onset scoliosis, who had very limited treatment options; however, the surgeons had to accept the high rate of complications and be able to deal with them. The study also recommended that an adequate orthotic capability be available, that surgeons be certain that the families of patients were willing to have their children undergo multiple procedures with anesthesia, and that the families be informed beforehand that at any stage the surgeon might have to discontinue the distraction procedure and proceed to a definitive instrumented fusion.

In subsequent studies, the single growing rod was used in different pathologic conditions, including congenital, syndromic, and neuromuscular scoliosis and neurofibromatosis; many studies done in Egypt were presented at various international meetings, including the 2005 International Meeting on Advanced Spine Techniques (IMAST) in Canada, the 2006 Scoliosis Research Society European and Middle East Meeting in Turkey, and the 2007 International Congress on Early Onset Scoliosis (ICEOS) in Spain. This international exposure enriched the experience of Egyptian surgeons and led to improvements in their techniques and results. The single rod construct remained the only option in Egypt for the surgical treatment of children with early onset scoliosis until a few years later, when Dr. Behrooz Akbarnia of the United States introduced the double rod construct, with its possible advantages. Since then, double rod constructs have become the standard of care for these children (Fig. 29.3).

Research done on the patients in Egypt treated with growing rods yielded three important original findings in the field of early onset scoliosis; the concepts were discussed for the first time worldwide and have clear implications for the management of these children. The first study looked at the growth of unsegmented bars in patients with congenital scoliosis treated with serial growing rod distraction. Unilateral bars have been identified as having absolutely no growth potential, and it has always been assumed that the concave side of a congenital curve does not grow. In this study, the unilateral bars appeared to grow during concave vertebral distraction with growing rods; their growth was much slower (about 25%) than that of the normal vertebrae in the same circumstances, and the growth appeared to be directly related to the number of distraction procedures (an increase in the bar of 3 to 4% per distraction). The coronal Cobb angle of the unsegmented bars also improved significantly in patients treated with concave growing rods; therefore, it may be possible to correct scoliosis due to unilateral bars with periodic distraction. In addition, the growth of unilateral bars during distraction may help in managing the pulmonary effects of congenital thoracic scoliosis. ²

The second study was planned to assess the controversial complication of pedicle screw migration; this was the first case series ever to document, quantify, and classify the change of position of distal pedicle screws in relation to the vertebral bodies in children with spinal implants. The change in position of the distal pedicle screws of growing rods in relation to the vertebral bodies was described as “pedicle screw migration, shift or drift?” Pedicle screws in growing rods are subjected to serial distractive forces that push them down during every distraction, in addition to the continuous growth and remodeling of the vertebral bodies during the treatment period; these two factors can affect their position within a vertebra. Two types of migration were identified in this study: one within the pedicle, with pedicle elongation, and the second through and distal to the pedicle. Apart from implant prominence, none of the patients experienced adverse clinical consequences related to this change (Fig. 29.4). The study concluded that a change in distal pedicle screw position with time is a frequent occurrence in single growing rods. ³

The third study was the first case series to use computed tomography (CT) to evaluate noninstrumented, nonfused segments of the spine in growing rod graduates with early onset scoliosis. The behavior of the growing spine after many years of distraction in regard to stiffness and spontaneous fusion, as well as the possibility of curve progression after maturity, remain controversial issues. This area of research is of great importance to understand not only the response of the vertebrae to long periods of serial distractions but also the need for final fusion at the end of the distraction program. In five patients younger than 9 years of age who had idiopathic early onset scoliosis, treatment was started with a single submuscular growing rod. They were evaluated more than 6 years after the index surgery, a minimum of six distractions, and a minimum of 2 years of follow-up after the last distraction with plain anteroposterior and lateral standing radiographs and with CT and sagittal, coronal, and axial reconstructions. The CT scans showed complete fusion of the facet joints at the levels studied; however, they showed severe degeneration and narrowing of the disk spaces without complete fusion. Also noted were a disproportionate ratio of vertebral body to disk height, irregular end plates, and the overall appearance of an arthritic spine (Fig. 29.5). The CT findings showed a stiff, nonmobile, fixed spine with probably little or no potential for curve progression. We concluded that after a reasonable follow-up period, growing rod graduates with satisfactory results could be treated by removing the growing rods, without the need for final fusion surgery. ⁴

In 2006, the Egyptian patients who had early onset scoliosis treated with growing rods were reviewed and included in the data of the Growing Spine Study Group (GSSG), based in the United States. At present, Cairo is still the only center representing Africa and the Middle East that is included in the GSSG, which is supported by the Growing Spine Foundation. The GSSG furthers medical education and scientific research with the purpose of optimizing outcomes in patients who have early onset scoliosis. This specialized study group is currently taking the lead worldwide in documenting and exploring the best strategies for the management of early onset scoliosis and is the main driving force behind most of the current research in pediatric spinal deformity.

Two landmark papers published by the GSSG looked at patients with early onset scoliosis; some of these cases were done in Egypt and the papers were co-authored by an Egyptian investigator. One was the first multicenter case series to evaluate the use of growing rods in congenital scoliosis. It reviewed 19 patients from the international multicenter GSSG database with progressive congenital spinal deformities who underwent growing rod surgery and had a minimum of 2 years of follow-up. The mean age at surgery was 6.9 years, the mean number of affected vertebrae per patient was 5.2, and the mean number of lengthening procedures per patient was 4.2. Spinal deformity, spinal growth, and space available for lung all improved. Complications occurred in 8 patients (42%), and there were 14 complications in 100 procedures (14%), with no neurologic complications. The study concluded that growing rods with serial distractions could reliably improve deformity correction in congenital scoliosis, enhance spinal growth (T1-S1 length), and increase space available for lung without any significant increase in the complication rate owing to the congenital nature of the deformities. ⁵

Another study was the first dedicated multicenter study to evaluate the clinical and radiographic complications associated with growing rod treatment. Previous reports have indicated high rates of complications after nonfusion surgery in patients with early onset scoliosis. Between 1987 and 2005, 140 patients met the inclusion criteria and underwent a total of 897 growing rod procedures. The mean age at the initial surgery was 6 years, and the mean duration of follow-up was 5 years. Of the 140 patients, 81 (58%) had at least one complication. The authors concluded that regardless of treatment modality, the management of early onset scoliosis is prolonged; therefore, complications are frequent and should be expected. Complications can be reduced by delaying the initial implantation of growing rods if possible, using dual rods, and limiting the number of lengthening procedures. Submuscular placement reduces the complications of wounds and implant prominence and reduces the number of unplanned operations. ⁶