Harrington and Cotrel-Dubousset instrumentation in adolescent idiopathic scoliosis. Long-term functional and radiographic outcomes.

Background: Previous studies have shown that the long-term clinical outcome does not correlate with the radiographic outcome in patients treated with Harrington instrumentation for adolescent idiopathic scoliosis. Cotrel-Dubousset instrumentation has been reported to provide better correction radiographically, but it is unclear whether it provides better long-term clinical or functional outcomes. We are not aware of any long-term studies comparing Harrington and Cotrel-Dubousset instrumentation.

Methods: Seventy-eight patients in whom adolescent idiopathic scoliosis was treated with Harrington instrumentation and fifty-seven in whom it was treated with Cotrel-Dubousset instrumentation participated in this study. The mean duration of follow-up was 20.8 years for the Harrington instrumentation group and 13.0 years for the Cotrel-Dubousset instrumentation group. The mean age at the time of follow-up was thirty-six years and twenty-eight years, respectively. Radiographs were made preoperatively and at the two-year and final follow-up examinations. The Scoliosis Research Society questionnaire was completed, a physical examination was performed, and spinal mobility and non-dynamometric trunk strength were measured at the final follow-up visit.

Results: The mean preoperative Cobb angle of the thoracic curves was 53 degrees in the Harrington instrumentation group and 55 degrees in the Cotrel-Dubousset instrumentation group. The mean numbers of vertebrae included in the instrumentation were 10.7 and 9.9, respectively. At the two-year follow-up evaluation, the mean postoperative Cobb angles were 38 degrees and 25 degrees, respectively (p < 0.0001). At the final follow-up evaluation, the mean angles were 45 degrees and 32 degrees (p < 0.0001). No significant difference in thoracic kyphosis or lumbar lordosis was observed between the study groups at the final follow-up evaluation. The average score on the Scoliosis Research Society questionnaire was 97 points in both groups. Measurements of non-dynamometric trunk strength corresponded with age and sex-adjusted reference values, on the average, but patients with Cotrel-Dubousset instrumentation performed significantly better in the squatting test (p = 0.010). Abnormal lumbar extension and trunk side-bending were significantly more common in the Harrington instrumentation group (p = 0.050 and p = 0.0061, respectively). Complications were recorded for nine (12%) of the patients treated with Harrington instrumentation and fifteen (26%) of those treated with Cotrel-Dubousset instrumentation (p = 0.027).

Conclusions: Cotrel-Dubousset instrumentation yielded better long-term functional and radiographic outcomes in patients with adolescent idiopathic scoliosis than did Harrington instrumentation. However, complications were more common in the Cotrel-Dubousset instrumentation group.