Because congenital scoliosis may present a major challenge to the orthopaedic surgeon, many options for treatment are available, including the CGA procedure. However, CGA [19
] requires an anterior surgery for completeness of the hemiepiphysiodesis and minor correction at the time of surgery, and therefore, unpredictability of the curve behavior has been observed. By modifying the procedure to include pedicle screw fixation of the anomalous convex levels and concave distraction of the entire curve, we aimed to eliminate these shortcomings. We therefore asked whether the modified CGA procedure involving a multilevel pedicle screw convex growth arrest combined with a single growing rod would correct the coronal Cobb angles and sagittal local and global kyphotic angles with a low number of complications.
However, there were certain limitations of this study. First, we had a small number of patients. We intended this as a preliminary review to determine whether the procedure was worth pursuing. Second, we had a relatively short final followup of a minimum of 26 months and mean of 24 months. We cannot ensure the corrections will be maintained although we will continue to follow these patients. Third, we did not include any length/growth measurements of the anomalous segments. The radiographs were not scaled; therefore, any length measurement made on these films would not reflect the actual lengths. However, we do believe the progressive angular correction seen on serial radiographic measurements indicated the epiphysiodesis effect was present and spine growth was enabled. Fourth, we had only one observer measure the curves at followup. These measurements are prone to interobserver variability and small differences cannot be reliably judged. Finally, we have no pulmonary functional data to report and therefore cannot comment on the effect of this technique for improvement of pulmonary functions.
Compared with the conventional (uninstrumented) CGA, the technique we describe uses an instrumented convex hemiepiphysiodesis of the anomalous segment along with fusionless distraction of the whole curve. The potential advantages of this modification are that instrumentation on the convex side provides a complete hemiepiphysiodesis at the anterior and posterior convex sides, obviating the need for anterior surgery and enabling compression-rotation maneuvers for initial acute correction. The fact that our patients have not experienced any symptomatic pseudarthrosis and correction loss in addition to no substantial change in the sagittal plane of the instrumented levels during the 2-year followup may indicate posterior pedicle screws might control growth of the anterior column. However, additional followup and imaging studies are needed to confirm whether pedicle screws will control anterior growth or provide anterior convex growth arrest. The immediate correction rates were better and the final followup Cobb angles and kyphosis angles compared favorably with those reported in other series of conventional CGA [15
]. The end result of uninstrumented CGA reportedly controls the coronal curve (stabilization effect), improvement in curve size (correction effect), and increase in curve size (progression) [2
]. Numerous clinical studies have compared the current technique in terms of possible end results of the CGA procedure [1
] (Table ). The current technique seems to be more effective than the uninstrumented CGA, as there was no progression in the curve size but there was correction in all patients. Control of the whole curve by the concave growing rod also helped obtain immediate correction of coronal plane balance problems when compared with uninstrumented CGA.
Comparison of results of uninstrumented traditional CGA and instrumented CGA with concave distraction
Several other modifications of the CGA procedure have been described [4
]. Cheung et al. modified the CGA procedure by adding concave distraction with a single Harrington rod and hook construct [4
]. They recommended this procedure for children with severe deformities and decompensation [4
]. Concave distraction produced immediate improvement in coronal balance, eliminating the need to wait for uncertain growth-mediated correction in patients who undergo convex fusion only. However, they used an anterior approach to complete hemiepiphysiodesis [4
]. All deformities in their series were thoracolumbar curves which included a complete hemivertebra. Mean correction after a followup of 10.8 years was 41% [4
]. In contrast, all patients in our study had more complex mixed deformities in the midthoracic spine. Followup was shorter but the correction magnitude was comparable to that reported by Cheung et al. [4
]. We expect further correction would occur with additional distractions.
Another alternative of limited fusion techniques for treatment of congenital scoliosis is growing rods. Growing rod treatment is an alternative method for treatment of young children with a long curve and with a relatively flexible apical deformity including congenitally deformed vertebrae [8
]. However, growing rods may not control the apex of congenital curves with stiff anomalous segments involving more than four vertebrae, as were the typical case samples in the current study [23
]. In our series we had control of the apex by convex screws and hemiephysiodesis and still had the opportunity to control and further correct the curve via the concave growing rod.
Another option for rigid, long sweeping congenital curves may be posterior vertebral column resection (PVCR) [14
]. Successful management of rigid severe curves was reported by Lenke et al. [14
]. However, this technique might have caused shortening of the thoracic spine in our patients and might necessitate fusion of at least four additional thoracic levels (two above and two below) for fixation after resection of the anomalous segments, thus interfering with thoracic growth and lung development in small children. Moreover, this procedure is technically difficult and carries more neurologic risk compared with less complex procedures [4
]. Therefore we believe our technique might provide advantages over PVCR, such as being an easier technique with less major complications, shorter fusion, and it preserves the length of the spinal column while controlling and even correcting the curve in the coronal plane.
Four of our five patients experienced some complications, as observed during followup, including partial pullout of the proximal, distal, or both pedicle screws of the concave distracted curves. This type of complication would not have been seen with the traditional CGA as no screws were used. However, this type of complication has been reported in series that used growing rod techniques and has been accepted as natural history rather than a complication [8
]. We originally used single pedicle screws at both ends and these cases were revised with pedicle screw changes during the planned distraction surgeries (Fig. ). Single-level fixation in fusionless instrumentation poses a substantial risk for failure; therefore, our recommendation is to put pedicle screws over two levels at the proximal and distal end vertebrae. One of the advantages of the current technique compared with uninstrumented CGA is the lack of pulmonary complications as no anterior approach was performed. Uzumcugil et al. reported pulmonary complications in six (19%) patients, all related to anterior surgery to provide anterior hemiephysiodesis [19
Despite the limitations mentioned, we believe this modified procedure may be appropriate for certain congenital spinal deformities. The rationale for this technique is that pedicle screws control growth of the anomalous vertebral segments in the longitudinal [13
] and transverse planes [5
], obviating the need for an anterior fusion, while permitting spinal growth on the concave side of the anomalous segments as a result of distraction [3
]. The procedure is a less invasive alternative for complex congenital curves, which otherwise may require multiple osteotomies and longer thoracic fusions. We recommend this technique for young children with multiple anomalous vertebrae and upper thoracic deformities, especially with long sweeping curves. However, care must be taken during distractions to prevent potential screw pull-out and to avoid iatrogenic kyphosis.