Randomized Clinical Study on Surgical Techniques with Different Pedicle Screw Densities in the Treatment of Adolescent Idiopathic Scoliosis Types Lenke 1A and 1B
Authors: Gotfryd Alberto , Avanzi Osmar 
Published: May 2015

Introduction

Advances in surgical instrumentation for the correction of vertebral deformities have been followed by the use of an increased number of implants in the construct. These advances have allowed greater correction, especially in complex cases. The use of pedicle screws throughout all anatomical levels of the spine has provided satisfactory correction of spinal deformities of large curves (between 70 and 100) through a single posterior approach, thus avoiding thoracotomy for intervertebral disc release. Nonetheless, the impact of the screw density on clinical, functional, and radiographic results of adolescent idiopathic scoliosis (AIS) treatment is still controversial. To the authors' knowledge, there is no clinical randomized study to date correlating two different surgical techniques using different pedicle screws densities (defined as the proportion of screws and number of pedicles being fused) and costs in patients with AIS.

Material and Methods

Forty-six patients with Lenke 1A/1B AIS and main thoracic curves to the right, 45 to 70, were operated using a posterior approach and free-hand technique. Once included in the study, patients were randomly allocated to one of the two groups with different techniques for surgical correction of the thoracic deformities. A member of the nursing team who was not involved in the research made the randomization using 46 identical, opaque, sealed envelopes, each containing one of the two group allocations and mixed them up in a box before the beginning of patient recruitment for this study. Group 1 was treated with 10 screws in strategically determined vertebrae: 4 in the base, 3 in the central vertebrae, and 3 in the superior vertebrae. In Group 2, the principles of segmental instrumentation were followed, treating all pedicles on the concavity side, except for the apical vertebra, and alternate pedicles on the convexity side, using 10 to 14 screws. Screw density was calculated as the ratio between the number of screws and pedicles fused.

Results

Groups were homogeneous regarding preoperative clinical and functional variables, surgery time, and intraoperative bleeding volume. Group 2 had a higher number of screws, average density of pedicle screws, and cost of treatment ( p = 0.000). The number of fused levels was similar between the groups. Two years postoperatively, all radiographic variables were homogeneous between the groups (mean correction of main thoracic curve was 68.5% in Group 1 and 67.9% in Group 2), but Group 2 achieved better clinical correction of the thoracic hump ( p = 0.000). Both presented significant improvement in the five domains of Scoliosis Research Society Score 30.

Conclusion

In AIS patients with Lenke 1A/B curves of 45 to 70, treatment with a higher pedicle screw density construct was significantly more expensive but had statistically similar functional results and radiographic correction. The denser construct achieved better correction of the thoracic hump 2 years after surgery.