An article published in Spine compares the cervical sagittal balance of two adolescent idiopathic scoliosis correction constructs — pedicle screws and hybrid instrumentation using hooks and pedicle screws.
The study included two series of 25 nonconsecutive patients with Lenke type-I AIS who underwent spinal fusion. In the first series, patients were treated with thoracic pedicle screw constructs; in the second series, patients were treated with hybrid constructs. Patients were followed for two years. The researchers found:
1. There was a lordic effect on the T5-T12 kyphosis after surgery in both groups. The average loss for the hybrid group was 6.1 degrees and the average loss for the pedicle screw group was 77 degrees. A study published in 2006 comparing pedicle screw and hybrid instrumentation for posterior spinal fusion in scoliosis correction found pedicle screw instrumentation can offer a "significantly better major curve correction and postoperative pulmonary function values without neurologic problems compared with hybrid constructs."
2. The only intergroup differences were in the sagittal C2-C7 Cobb angle. There was an average kyphotic trend in the pedicle screw group — -5.2 degrees — when compared with the average lordic trend in the hybrid group — 1.8 degrees.
3. Patients with upper instrumented vertebra at T4 or below showed a lordic effect in both groups. However it was more evident in the hybrid construct.
4. Patients with upper-instrumented vertebra at T3 or higher had a more severe kyphotic effect. However, the effect was more severe among patients in the pedicle screw group. A study examining patient volume for scoliosis surgery in New York and California found spinal fusion was the most common operation for scoliosis surgery between 1992 and 2001, but only a relatively small number of surgeons were performing it. Technology and training advancement since then has impacted procedure availability and outcomes.
5. The study authors concluded that the cervical spine has a tendency to decompensate and acquire a kyphotic sagittal profile regardless of the surgical technique used. "Constructs based on all pedicle screws have a stronger hypokyphotic effect on the thoracic spine, with a predisposition to greater decompensation of the cervical spine," they noted. "Kyphotic changes in the C2-C7 sagittal alignment introduced by scoliosis correction are correlated with the level of the upper instrumented vertebra."
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