Collar-button wires effective anchors in multi-hook spinal fusions

Combined instrumentation in AIS patients improves stability and also maintains correction.

CHICAGO — Using concave collar-button wires as anchors in multi-hook rod systems enhances stability and maintains correction of spinal fusion in adolescent idiopathic scoliosis patients, Florida researchers found.

Jose A. Herrera-Soto, MD, of Arnold Palmer Pediatric Orthopedics in Orlando, Fla., and colleagues from Cincinnatti Children’s Hospital, conducted the study, which included 67 children with adolescent idiopathic scoliosis (AIS). They found spinal fusion instruments augmented with concave collar-button wires yielded a 74% mean correction and 2° mean correction loss at two years’ minimum follow-up.

“The technique compares favorably to, if not exceeding, the performance of other systems,” Herrera-Soto said here at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting. “We believe that multi-hook dual rod systems with multiple anchors using the collar-button wires is a safe method [that] doesn’t invade the canal. It enhances stability and maintains correction.”

The study included 45 girls with an average age of 13.8 years and 22 boys with an average age of 14.2 years. All children had spinal curves greater than 45° and both radiographic evidence of progression and failed bracing, Herrera-Soto said, noting no patients had thoracolumbar curves.

Surgeons performed spinal fusion using a multi-hook dual rod system with concave collar-button wires. Twenty-four patients received an additional anterior release and fusion using video-assisted thorascopic surgeries (VATS). Surgeons used iliac crest or rib bone autografts for the posterior spinal fusions and fibular allografts for the VATS procedures, Herrera-Soto said.

Postoperatively, all patients completed six weeks of full-time bracing followed by a weaning period of another six weeks.

Preoperatively, patients had a mean Cobb angle of 58.6° in the frontal plane and 25° in the sagittal plane. Immediately postop, the major frontal plane curve reduced to a mean 14°. There was no change in sagittal curves, Herrera-Soto said.

“The correction of the major curve average was 74%. When combined [with] VATS and posterior fusion, it went up to 89%,” he said, noting posterior fusion alone yielded a mean 70% improvement.

All patients showed solid fusion. At a mean 36 months’ follow-up, the major curve’s mean Cobb angle nonsignificantly increased to 16° in the frontal plane (P>.05). But there was no difference in loss of correction between treatment groups.

Researchers also found no cases of pseudoarthrosis, rod breakage or hook pullout, although some nonsignificant incidental wire breakage was noted. “Frontal plane correction was obtained and maintained. No junctional kyphosis was noted or neurologic injuries,” Herrera-Soto said.

Complications included three delayed infections (4.5%) at three years postop. The implants were removed without fixation loss. Other complications included six pleural effusions, one superior mesenteric artery syndrome and four early coronal alignment losses. Pleural effusions required thoracentesis, including four thoracoplasties and two post-VATS.

For more information:
Herrera-Soto J, Crawford A, Al-Sayyad M, et al. The use of multiple anchors for correction of idiopathic scoliosis. #416. Presented at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting. March 22-26, 2006. Chicago.