Influence of pedicle screw instrumentation on growth potential of the immature vertebra

English Keywords:Pedicle screw  Neurocentral synchondrosis  Vertebral body  Spinal canal  Growth

English Abstract:

  【Abstract】 Objectives: To explore the influence of pedicle screw instrumentation on the growth of immature spine at a very young age. Methods: Between January 2000 and December 2016, individuals who had bilateral pedicle screw instrumentation were reviewed. Patients younger than 5 years old with a minimal follow-up of 5 years were included. Anteroposterior diameter of vertebral body, pedicle length of both sides, anteroposterior diameter, transverse diameter and area of spinal canal were measured on CT images before surgery and at final follow-up. Parameters of instrumented vertebrae and adjacent non-instrumented vertebrae were compared. Growth value was calculated as: preoperative value - postoperative value, and growth percentage were calculated as: growth value divided by the final follow-up value. Subgroups of thoracic vertebrae and lumbar vertebrae were compared, respectively. Statistical analyses were performed. Results: 13 patients with congenital spinal deformity were enrolled. The average age at surgery was 3.4±1.1(range, 2-5) years old, and the average follow-up was 7.2±2.2(range, 5-11) years. Osteotomy and short instrumentation with pedicle screws were performed on each case. A total of 69 segments was measured, including 43 instrumented vertebrae and 26 adjacent non-instrumented vertebrae. Significant increases of all parameters were noted at final follow-up. The growth value(2.2±1.7mm vs 1.1±1.3mm), the area of spinal canal(72.8±48.5mm2 vs 39.2±26.3mm2), the growth percentage of anteroposterior diameter[(11.2±7.1)% vs (6.0±6.0)%] and area of the spinal canal[(21.3±11.6)% vs (13.4±8.1)%], the anteroposterior diameter of vertebral body(3.8±2.5mm vs 6.1±3.0mm) and its growth percentage[(20.5±12.1)% vs (28.1±11.0)%] had significant differences between instrumented vertebrae and non-instrumented vertebrae(P＜0.05). Similar results were noted in lumbar region. Shape-change phenomenon was found in non-instrumented vertebrae and not apparent in instrumented vertebrae. Conclusions: Pedicle screw instrumentation may slow down the growth of vertebral body, indirectly speed up the growth of spinal canal and hinder the shape-change phenomenon of lumbar spinal canal. But the influence is quite slight and the significant development occurs in instrumented vertebrae. So pedicle screw instrumentation may not make a great difference on the growth of immature vertebrae in children younger than 5 years old.