Abstract

The advantages of VDS according to Zielke with excellent 3-dimensional correction and shorter fusion levels in comparison to posterior instrumentation techniques are well known. A disadvantage is the necessity of long postoperative immobilization in a body cast or brace due to lack of primary stability. The aim of the VDS double-rod instrumentation is augmentation of the system with the possibility of postoperative treatment without plaster cast or braces. Following thoracolumbophrenotomy and ligation of the segmental vessels double-hole vertebra clamps are inserted. First VDS screws are placed in the posterior holes of these plates. With a 4-mm threaded compression rod correction is obtained by centripetal compressive forces on the nuts. Next VDS screws for the 5-mm threaded rod are inserted into the anterior holes of the vertebral clamps. The rod is implanted in a slightly compressive manner and augments the system. In a prospective study 8 patients, 4 with idiopathic and 4 with neuromuscular scoliotic deformities, underwent this surgical procedure and now have a follow-up of 2 years. Curves ranged from 45 degrees to 131 degrees Cobb angle. All patients were treated without plaster casts or braces postoperatively, but with only a semielastic vest for 4 to 6 months. Unusual intra- and postoperative complications have not been noted. Correction of the primary curve averaged 69.4% at follow-up. Tilt of the caudal end vertebra was corrected 75% to an average of 6.3 degrees. Spontaneous partial correction of the upper secondary curve was noted in all cases. Rod fracture of the 5-mm rod without fracture of the 4-mm rod at this level was seen in 1 patient without loss of correction. Solid fusion was achieved at every level in all patients. The sagittal plane was not adversely affected by the instrumentation. However, larger patient numbers and a longer follow-up are necessary.