[Effect of Harrington instrumentation spondylodesis on scoliotic thoracic deformity. A retrospective 5-year analysis]

Harrington-Instrumentation (HI) was the golden standard of scoliosis surgery for more than two decades and is still frequently used. The effects of instrumentation on rib hump reduction in long term follow-up is not well documented. 104 patients with idiopathic thoracic scoliosis were studied with a minimum follow-up of five years (min. 5 y., max. 8 years).

The rib-cage deformity was determined as rib hump index (RHi) by measuring the rib hump to the depression. The long term effect of HI was investigated using full standing AP radiographs. Measuring cobb angle (CA), translation (TA) and rotation of apical vetebra (RA) were obtained for every patient preoperatively, postoperatively and at follow-up. Patient were analysed in 3 different groups. Single curve thoracic scoliosis (n = 54) (King III and IV), double curve thoracic/lumbar scoliosis (n = 35) (King I and II) and double curve thoracic scoliosis (n = 15) (King V).

With an average preoperative measurement of 62.7 degrees and a postoperative measurement angle of 32.9 degrees the correction of CA achieved is 47.5% (23-73%). The mean thoracic translation improved by 50% (0-100%). Rotation of the scoliosis was not reduced significant. In follow up studies no loss of correction in frontal plane deformity was obtained. The mean RHi in all groups was seen to improve by 25-30% (min. 0%, max. 60%), depending on form of scoliosis. In group of patients King II/III scoliosis (n = 52) the mean RHi increased measurably to 11.5% (min. 0%, max. 50%) correction at long term follow up. In group of patients King I/II scoliosis average RHi was increased from 31% (5-100%) to 21% correction. The mean RHi correction in the group of patients King V scoliosis correction rate of 26% (0-50%) was unchanged at long term follow up.

HI leads to a permanent and stable improvement of the frontal plane including apical vertebral translation. HI does not have derotational capabilities. The effect of the rib-cage deformity was less impressive with loss of correction at follow up.