PATIENTS AND METHODS
Between 1989 and 1994, 30 patients with idiopathic scoliosis were treated at the Department of Orthopaedic Surgery. Aristotelian University of Thessaloniki. They were 21 girls and 9 boys with a mean age of 15 (11-21) years. All patients underwent posterior spinal fusion and segmental spinal instrumentation using 2 Luque 1 rods (8 patients, 1989 - 1990) or a Hartshill rectangle (22 patients, 1991 - 1994) with sublaminar wiring. Spinal deformities by the Cobb method averaged 660 (450 - 1120). There were 16 thoracic (1 double thoracic). 10 thoracolymbar and 4 double major curves (right thoracic, left lumbar).
All procedures were performed by 2 of the authors and all patients were reviewed by AGC at the latest follow-up which averaged 4 (2-6) years postoperatively 3 patients who had neuromusular spinal deformity were not included in this study.
Preoperative evaluation of all patients was standard and included a neurological examination, routine blood evaluation. AP and lateral standing radiographs, right and left maximum bending radiographs, chest radiograph, electrocardiogram amd pulmonary function tests. CT or MRI were performed when indicated. Clinical photographs were taken preoperatively and 1 year postoperatively. In 10 patients who underwent fusion with a Hartshill rectangle the rotation of the apical vertebra was evaluated pre -and postoperatively by CT (Aaro and Dahlborn 1982).
The last 19 patients followed protocol of autologous blood transfusion with blood collection starting 3 to 5 weeks preoperatively. Intraoperatively salvaged red blood cells were also used. The patient under general anesthesia and prophylactic antibiotic therapy, was placed prone on the operating table with thw hips flexed. The surgical technique consisted of a standard posterior midline approach to the spine to cover the entire deformity and extended caudally to the sacrum to the subcutaneous fat only, in order to expose the right posterior iliac for obtaining the bone graft.. After exposing all the posterior elements of the spine up to the articular processes in the thoracic region, a release of the contracted soft tissues on the concave side was performed. Additionally, all the facets of the vertebrae to be fused were excised, as well as the central portion of the ligamentum flavum.
Segmental spinal instrumentation was carried out by passing 18 gauge cold - worked 316-L stainless steel wire as 2 double loops arount the lamina of each end vertecbra and as one double loop around the other laminae of the curve. This double wire was finally cut at the end and the 2 wires were separated. 2 Luque rods or a Hartshill rectangle of 0,64 cm thickness were securely fixed by twisting the wires with a Robinson jet wire twister (Luque 1982. Dove 1987). All the rods were already contoured into the appropriate Kyphosis and/or lordosis. When the correction time exceeded 60 minutes, a wake-up test was performed.
Copious autologous grafts, obtained form the outer surface of ilium, was placed in the facelectomy areas and the decorticated costotransverse processes.

RESULTS
Correction by preoperative bending radiographs averaged 460 (190-800), while postoperative correction on standing radiographs averaged 270 (190-480-57% correction) Figure 1). In all cases but 1, the preoperative correction was exceeded at surgery on an average of 150 (00-290).
During the first 12 months postoperatively, loss of correction ranged from 20-120 (Figure 2). After this period, no change of the curve was noted. The final result was a curve with a range between 190 and 480 (average 290, correction 55%). These results do not include I patient with broken wires and I patient with broken rods (Table 1). CT showed an average correction of rotation of 30 (00-80).
An average of 3,9 unit/patient of intraoperatively salvaged red blood cells were collected for 19 patients for reinfusion. None og these patients required allogenic transfusion. In contrast, an average of 7,1 unit/patient was required for first II patients who did not follow the autologous transfusion program.
Rods broke in only one 11 -year- old with thoracolumbar scoliosis (T8-L3) of 700 who was treated with a double L Luque rod system without fusion. The curve was corrected to 330, but one year postoperatively a kyphosis developed above the instrumented region. A second operation was performed to extend the rods up to T2 with satisfactory correction of the kyphosis. 5 months later, the original rods broke at the T12-L1 level with substantial loss of correction (curve 600). The patient was reoperated using a Cotrel-Dubousset system and bone grafting.
Wires broke in 4 patients. In 3 patients, the wires of the neutral cephalad or caudal vertebrac broke 6, 12 and 14 months postoperatively with minimal loss of correction. In the found patient with a thoracolumbar curve of 650 which had been corrected to 190 with a Hartshill rectangle, the wires broke at 4 levels, 8 months postoperatively the patient felt a snapping pain and a 220 loss of correction was seen radiographically. The patient refused reoperation and a final correction of 450 was achieved by bracing.
Sliding between the L-rods was observed in 6 patients (Figure 3). The ends had completely disengaged in 2 patients without loss of correction, but with a difference between pre and postoperative height of 5 and 9 cm, respectively.
There were no postoperative motor or sensory deficits, and the wake-up test successful in all 30 patients.
One patient treated with 2 Luque rods, developed deep wound infection and empyema in the right pulmonary cavity. After thorough irrigation and debridement and placement of a chest drain, the infection subsided in 2 weeks. The metal work was not removed. Antibiotic therapy was given for 3 months with solid fusion and a loss of correction o 60.

DISCUSSION
The spine is a segmental structure. For maximum correction of a given deformity and maximum stabilization, the spine should be fixed at each level of the deformity. The optimum system for spinal fixation would be one which controls segmentally the entire vertebral frond, middle and back, and one which is safe and easy to use providing sufficient fixation with no need for external support and minimal incidence of complications, such as pseudarthrosis, failure of the implant and neurological deficits. Additionally the xost of the implant should be taken in account. Segmental wiring with the use of a double paravertebral bar or even better two bars welded into a rectangle, seems to fulfill many of the above criteria.
Correction of the scoliotic curve in this series was satisfactory and in most cases surpassed the "safety" limit (degrees of maximum preoperative bending correction plus 100) (Luque 1982). None of the rods or rectangles were contoured in a scoliotic shape to avoid over correction. They were placed straight and were only contoured in the appropriate kyphosis or lordosis.
The length of the operating time that correction took place by twisting gradually the wires was more than one hour. This fact in addition to the absence of any motor or sensory neurological deficit suggest that correction over the "safety" limits can be achieved. By using segmental wiring the spinal cord is not stretched as the deformity moves sideways. This is in contrast to other techniques in which distraction is applied, often leading to postoperative neurological problems (MacEwen et al. 1975. Wilber et al. 1984). Currently wa app;y as much intraoperative correction as possible and neurological deficit has been noted in 46 patients.
The Hartshill rectangle is believed to improve both stability and correction of rotation of the 2L rods system (Dove 1987). Correction of rotation was not observed in the present study, where the average correction of rotation of 30 was considered insignificant.
The complication of broken rods in the case with Luque trolleys occurred because the rods of 0.48 cm thickness were not protected by bone grafting. On the other hand, the rectangle which was 0.64 cm thick was never observed to break. It appears that the elasticity of the wires may permit some movement in the multisegmental junctions and thus, wire breakage is more common that rod breakage.
Wires that broke in this series were the cephalad and caudal ones at the level of the end vertebrae. Examination of postoperative radiographs indicated that the rectangle did not conform with the lamina and the repeated bending movement at this level lead to breakage. There are no definite guidelines on which rod size should be used, however, thicker rods which do not protrude seem to be preferable (Herndon er al. 1987). Disengagement of the ends of the L rods is undesirable and may occur either because of inadequate wiring technique or because of substatial growth. In this regard, if an increase in height is expected, L rods longer than the expected height should be chosen.
Loss of correction was minimal in the present study and occurred in the first 12 months. The incidence of broken rods and the magnitude of lost correction have been related to the absence of bone grafting (Herndon et al. 1987). Our wiring technique which combines a simple symmetric twist with a double twist over the graft and not the rod, seems to offer a satisfactory fusion, as the corticocancellous bone graft slices are well-stabilized on the decorticated costotransverse or transverse processes.
Although the need for postoperative support has been suggested by many authors (Broadstone et al. 1984. Nasca 1984, Winter 1985), our findings clearly suggest that segmental internal fixation does not require bracing, particularly not for thoracic curves (Christodoulou et al. 1987).

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