gms | German Medical Science

Ventral Derotation Spondylodesis according to Zielke achieves good three-dimensional corrections of idiopathic thoracolumbar scolioses. In spite of a recommended cast treatment postoperatively the high rate of rod breakages represents a problem. By keeping to the correcting principle developed by Zielke anterior doublerod instrumentation is to be stable, however, in a similar way as posterior doublerod systems and is to facilitate brace-free postoperative care.

Retrospectively we performed clinical and radiologic follow-up of two groups of patients with idiopathic thoracolumbar scoliosis (King-II, -III and -IV) undergoing an operation with posterior approach (USS instrumentation, posterior group, n=104) in 1997 and 1998 or being corrected with an anterior fusion (micomed instrumentation, anterior group, n=37) between 2000 and 2001. The average age for operation was 15+5 years, follow-up was performed after 3+1 years. All those patients getting ventrodorsal spondylodeses combined or whose operation was less than 12 months ago were excluded.

Preoperative measurements of the major and lateral curve, the lateral profile, rotation and balance (C7 to S1) did not show any significant differences apart from a more severe scoliotic curve in the lumbar spine for the anterior group with appropriately higher lumbar rotation. Postoperatively we noticed similar corrections of the thoracic major and lumbar curve in both groups which ranged from 49% to 56% (posterior or anterior group: thoracic curve 24+9° versus 25+12°, lumbar 16+8° versus 21+14°). A slightly kyphogenic effect on the thoracic spine only occurred in the anterior patient group (from 24+13° to 27+13°). In addition correction of thoracic and lumbar rotation in the anterior group by 37% or 30% was more significant than in the posterior group by 27% or 20%. Impact of posterior technique on the balance of the spine which was corrected by 3mm towards the midline was definitely more favorable whereas it deteriorated on an average of 7 mm to the left in the posterior group. The number of fused segments was significantly smaller in the anterior group with 7±1 vertebral bodies (posterior: 11±1 vertebral bodies). Rates of complication (material breakages, loosening of screws, delayed infections, lumbar decompensations, secondary hemorrhage) were identical with 9% or 10% in both groups. We had never to observe neurological deficits.

Anterior and posterior doublerod instrumentations result in approximately comparable corrections for idiopathic thoracic scolioses. In case of posterior technique, however, 4 vertebral bodies less were integrated in spondylodesis on average. Furthermore balance of the spine is improved by the anterior technique, by posterior technique, however, it is declined.