Prevention of Crankshaft Phenomenon with Posterior Pedicle Screw Fixation in Scoliosis of Immature Spine: Is it Possible?

Scoliosis correction in the immature spine frequently necessitates additional anterior surgery to prevent crankshaft phenomenon. With the advent of posterior segmental pedicle screw fixation, it is unclear whether or not additional anterior surgery is necessary to prevent crankshaft.

Purpose: To evaluate the clinical results of posterior only surgery with segmental pedicle screw fixation in skeletally immature scoliosis patients.

Materials and Methods: Seventeen scoliosis patients with 22 structural thoracic curves (10 idiopathic, 4 congenital and 3 others; 3 males and 14 females) treated with segmental pedicle screw fixation were retrospectively reviewed for deformity progression of more than 10° in coronal plane, rib vertebral angle difference (RVAD) progression of more than 10°, or evidence of progressive caudal or cephalad deformity after posterior spinal fusion. All patients were Risser O at index operation. The average age of patient at index operation was 10.4 years (range: 7.2-11.8), and the average follow up was 4.0 years (range: 3.0-5.4). All patients were Risser 4 or 5 at latest follow up.

Results: Eight patients had open triradiate cartilage at the time of surgery. Six patients were prior to their peak height velocity (PHV), 5 during their PHV, and 6 past PHV. The preoperative index curve of 55º was corrected to 21º (62%) at latest follow up and the non-structural curve of 31º was corrected to 10º (68%). Preoperative 27º of thoracic kyphosis was improved to 34º. The RVAD was 23º preoperatively and 13º postoperatively. No patient showed a 10° or more progression of the index curve or RVAD after surgery. One patient had progression of deformity caudal to the instrumented segments. There was no neurological or screw related complications.

Conclusions: Posterior segmental pedicle screw fixation in skeletally immature patients with scoliosis may be effective in preventing crankshaft phenomenon. This negates the need for anterior surgery in these patients.