Comparison of Long-Term Functional and Radiologic Outcomes After Harrington Instrumentation and Spondylodesis in Adolescent Idiopathic Scoliosis

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Abstract
A retrospective follow-up study of adolescent idiopathic scoliosis after Harrington instrumentation and spondylodesis was conducted. To correlate radiographic parameters with the Scoliosis Research Society questionnaire in terms of patient outcome, clinical findings, spine mobility, and trunk strength measurements. Previous studies have shown that long-term radiologic correction can be achieved with Harrington instrumentation. It seems, however, that radiologic correction does not correlate with patient outcome. There are no previous studies on long-term results of functional outcome, including spine mobility and trunk strength measurements, after operative treatment of adolescent idiopathic scoliosis, as compared with findings in the normal population. Of 98 consecutive patients who underwent surgery with Harrington distraction rod and posterior spondylodesis in 1979, 78 (80%) (11 males; mean age, 36 years) participated in the study. The average follow-up period was 20.8 years (range, 19.1–22.4 years). Radiographs were obtained before surgery, at the 2-year follow-up assessment, and at the 20-year follow-up assessment. Additionally, physical examination was performed, and the Scoliosis Research Society questionnaire was completed. Spine mobility and nondynamometric trunk strength measurements were obtained at the 20-year follow-up assessment. The mean Cobb angle of the instrumented thoracic curve was 53° ± 10° before surgery, and 38° ± 11° at the 2-year follow-up assessment. At the 20-year follow-up assessment, the mean angle was 45° ± 12°. Degenerative changes in the noninstrumented lumbar spine (sclerosis of facets, endplate sclerosis, osteophyte formation) were noted in 17 patients (22%). Ten patients (13%) reported having low back pain often or very often at rest according to the Scoliosis Research Society questionnaire. No correlation was found between the Cobb angle of the thoracic or lumbar curves at follow-up assessment and the Scoliosis Research Society total score or back pain indexes. Neither was any association found between the Scoliosis Research Society total score and the spondylodesis fusion level. However, the magnitude of the thoracic curve at follow-up assessment showed a significant inverse correlation with the scores for Scoliosis Research Society questions about cosmetic aspects. The nondynamometric trunk strength measurements corresponded with the reference values, on the average, but did not show any correlation with the magnitude of the thoracic or lumbar curves or with the Scoliosis Research Society total score or back pain indexes. Spine mobility, especially trunk side bending, was diminished in 59% of the patients, and did not correlate with the Scoliosis Research Society total score or individual indexes. In patients with adolescent idiopathic scoliosis who undergo surgery with Harrington instrumentation, the overall long-term clinical outcome does not correlate with the radiologic outcome. However, a significant inverse correlation was found between the magnitude of the primary thoracic curve at follow-up assessment and the scores for questions on cosmetic matters in the Scoliosis Research Society questionnaire. Spine mobility is diminished as a result of spondylodesis, but the patients perform, on the average, as well as the normal population in nondynamometric trunk strength measurements.