In vivo distraction force and length measurements of growing rods: which factors influence the ability to lengthen?

STUDY DESIGN: Prospective, intraoperative force measurement in consecutive lengthening procedures in a series of growing-rod patients undergoing lengthening. OBJECTIVE: The purpose of this study was to measure the forces and amount of distraction over time in early onset scoliosis patients treated with growing rods. SUMMARY OF BACKGROUND DATA: Growing rods are one of the current techniques used in the treatment of early onset scoliosis, and the goal of the growing-rod technique is to achieve deformity correction, maintaining spinal growth at the same time. Gradual stiffening or spontaneous fusion of the spine can interfere with the ability to lengthen. In addition, diminished acquired length with serial distraction are common observations and need to be evaluated and quantified. METHODS: Distraction forces were measured prospectively during 60 consecutive lengthening procedures in 26 patients. All patients had single submuscular rod constructs with side-to-side connectors. For each measurement, output from a transducer on a dedicated pair of distraction calipers was recorded at zero load status and the force was then recorded at every 1 mm lengthening; length was obtained at each event and was recorded in millimeters. RESULTS: The force required to distract the spine doubled at the 5th lengthening procedure (mean 368 N ± 54 N), and the distraction force was significantly higher at the fifth lengthening compared with the previous lengthening (P <0.01). Mean length achieved at each distraction decreased over time such that by the fifth lengthening, consistently 8 mm or less was achieved. CONCLUSION: Distraction forces increase significantly after repeated lengthening of growing-rod constructs, and the length obtained at each procedure exhibits a decreasing trend.

Anterior instrumentation and correction of congenital spinal deformities under age of four without hemivertebrectomy: a new alternative.

STUDY DESIGN: Retrospective clinical and radiologic evaluation of a single-stage partial corpectomy of the hemivertebra with anterior instrumentation and simultaneous posterior noninstrumented fusion. OBJECTIVE: To determine the safety and efficacy of a new technique in the management of progressive congenital spinal deformities due to failure of formation in the very young age. SUMMARY OF BACKGROUND DATA: Several techniques have been reported for the surgical treatment of young children with congenital spinal deformities. There have been concerns regarding epidural bleeding, neurologic complications, pedicle screws placement, implant failure, and prominence of posterior constructs in this very young age group. A single-stage partial corpectomy of the hemivertebra with anterior instrumentation and simultaneous posterior noninstrumented fusion can offer a new alternative which can avoid these concerns. METHODS: Twelve patients with progressive congenital spinal deformities due to failure of formation were retrospectively reviewed after adopting the above mentioned technique. All patients included in the study presented with a single hemivertebra. The mean age at time of surgery was 2 years 7 months (range, 1 year and 9 months to 3 years and 10 months). The average follow-up period was 3 years and 1 month (range, 2 years to 4 years and 5 months). RESULTS: There were no cases of intra or postoperative neurologic or implant related complications. There was 1 superficial infection. All patients showed solid radiologic fusion. The mean scoliosis angle improved from 48.3° (range, 34°-58°) preoperative to 17.2° (range, 11°-25°). The mean angle of kyphosis improved from 23.2° (range, 16°-57°) before surgery to 11.7° (range, 4°-16°). CONCLUSION: A single-stage partial corpectomy of the hemivertebra with anterior instrumentation and simultaneous posterior noninstrumented fusion offers a safe alternative method in treating patients with congenital hemivertebra under the age of 4 years.