Purpose of the study: The long-term results after surgical treatment of idiopathic scoliosis depends not only on the correction in the coronal plane but also the restoration of good sagittal balance and thus satisfactory sagittal curvatures. Recent publications have shown moderate correction of the thoracic hypokyphosis of idiopathic scoliosis with instrumentations using hooks and pedicular screws. We report results in the coronal and sagittal play with a reduction technique by simultaneous translation on two rods (ST2R).

Material and method: The radiographic parameters were measured preoperatively, at 6 weeks, at 1 year, and at last follow-up (range 2 – 7.4 years) in a consecutive series of 72 patients treated with posterior instrumentation and reduction using the ST2R system. The same operator performed all procedures using stable anchors (pedicle screws or self-stabilizing clamps). Screws and clamps had a threaded polyaxial extension which was linked to the rod by a connector. The deformity was reduced by progressively tightening the two rods alternatively using the nuts on the threaded extensions. This manoeuvre enabled the vertebrae to migrate progressively toward the rods, producing an anteroposterior translation.

Results: In the coronal plane, the mean main curvature was reduced from 54 to 17 and was maintained (70%) without loss of angle at last follow-up. There was not difference between the 56 patients with thoracic scoliosis (Lenke 1–4) and the 16 patients with thoracolumbar or lumbar scoliosis (Lenke 5 and 6). In the sagittal plane, for the patients with preoperative hypokyphosis (32 patients < 20), the mean kyphosis was significantly improved from 9 to 30 and remained stable at last follow-up (31) with a mean gain of 21 (p< 0.001). One patient still had hypokyphosis (18) at last follow-up. For patients with normal kyphosis preoperatively (> 20), the mean gain was 7.

Conclusion: In this consecutive series of 72 adolescents with idiopathic scoliosis, reduction by simultaneous translation on two rods was a simple and effect method which restored normal thoracic kyphosis.

Background: context: In Adolescent Idiopathic Scoliosis (AIS), the correction of thoracic hypokyphosis with hooks instrumentation and also with pedicle screws system is moderate.

Purpose: To compare radiographic results between two instrumentations with thoracic screws using two different

Methods: of reduction: cantilever reduction (CR group– MOSS-MIAMI system) versus simultaneous translation on two rods (ST group – PASSMED system).

Study design: Retrospective comparative analysis of two consecutive cohorts of patients treated by the same surgeon at a single hospital.

Patient sample: Forty-two adolescent idiopathic thoracic scoliosis (Lenke type 1, 2 and 3) underwent a posterior spinal fusion and instrumentation: 20 patients in CR group and 22 patients in the ST group. The minimum follow-up was two years (Mean follow-up: 71 months and 47 months).

Outcomes measures: Thoracic sagittal kyphosis between T4 and T12 and Cobb angle measurements of major and minor curves evaluated preoperatively, postoperatively and the final visit, by an independent observer.

Methods: In CR group, we have used polyaxial pedicle screws and one or two monoaxial thoracic hooks. In ST group, we have used polyaxial pedicle screws and poly-axial claws which provide same stability than screws. Three groups of preoperative kyphosis were generated: 11 patients with severe hypokyphosis (T4–T12 < 10°) (5 in CR group and 6 in ST group); 11 patients with mild hypokyphosis (between 10 and 20°) (respectively 4° vs 7°) and 20 with normokyphosis (> 20°) (respectively 11 vs 9).

Results: At the final follow-up, for patients with a severe preoperative hypokyphosis, the mean gain was 14 degrees in the CR group (8° preop to 22° postop) and 25° in the ST group (6° preop to 31 postop) (p< 0.05). For patients xith mild hypokyphosis, te mean gains were respectively 7 degrees (16° preop to 23° postop) and 18° (16° preop to 34° postop) (p< 0.05). After surgery, 3 patients of CR group had hypokyphosis alors que all patients had normal kyphosis (> 20°) in the ST group. In the coronal plane, the mean correction of scoliosis are similar in the two groups (75% vs 69% p=NS)

Discussion and Conclusion: In posterior instrumentation for AIS, simultaneous reduction on two rods provides a better correction of the thoracic kyphosis than the cantilever reduction in patient with preoperative hypokyphosis. This surgical technique seems to restore thoracic normal kyphosis.

Purpose: We present our experience with thoracic and lumbar pedicular screws for surgical correction of thoracic scoliosis.

Material and methods: Fifty patients with idiopathic scoliosis (mean age 20 years), underwent instrumentation with Moss Miami long-arm polyaxial pedicular screws. The point of entry into the pedicule was identified by progressive probing. Results were analysed at a mean follow-up of 3.5 years.

Results: Mean angle of the main instrumented curvature was 54° preoperatively and 14° postoperatively (75% initial reduction, 53% bending), and 15° at last-follow-up (74% correction). The non-instrumented lumbar curvature improved from 34° to 10°, giving a spontaneous correction of 72° (49° bending) at last follow-up. Inclination of of the first non-instrumented vertebra was 11° preoperatively and 6° at last follow-up. Kyphosis was improved in all cases with a mean gain of 10° for kyphotic spines.

Discussion: Morphological correction of scoliosis deformation and the long-term outcome depend on the quality of the initial reduction. Monitoring the spinal cord during the procedure enables best quality reduction.

In the frontal plane, corrections with hooks have varied from 38% to 55% depending on the series. This percentage improves to 60% when the lumbar curvature is instrumented with screws. Like Suk and Harms, we have found greater than 70% correction when the entire curvature is screwed using lumbar and thoracic pedicular screws. In the sagittal plane, results of hook instrumentations have been less than satisfactory for many authors (Betz, Rhee...). The improvement obtained with pedicular screws results from two effects: the stability of the construct which remains stable during reduction manœuvres allowing application of strong force, and the polyaxis arrangement allowing inserting the rods in all the screws simultaneously and thus distributing the reduction forces. The long-arm screws are brought into contact with the rod progressively by tightening the nuts bringing the vertebrae into line with the rod. We have not had any complication after insertion of 550 screws. We have not used distraction which we consider dangerous for the neurological structures nor contraction at the thoracic stage which induces lordosis.

Conclusion: The stability of the pedicular screw instrumentation for scoliosis allows clear improvement in the quality of the reduction.

Introduction: Some authors (Suk, Barr, Hamill ...) showed that lumbar and thoracic pedicle screws provided adequate reduction of scoliosis. Quality of reduction depends on primary stability of the vertebral anchors. If the anchor has a good primary stability, reduction forces are entirely transferred to the vertebra, which results in reduction of the deformity, whereas, if the anchor has a poor primary stability, it will move when subjected to reduction forces, and this will result in inadequate reduction. Lumbar screws which are advocated by many authors, are extensively used. Thoracic screws are only used by a limited number of surgeons, as most surgeons favour hooks. Polyaxiality facilitates rod positioning; it eliminates the orthogonal stresses that are generated during tightening and which are known to be responsible for screw fracture. The drawback manoeuvre consists in applying forces directly to the vertebra via the anchor; the deformity is reduced by gently translating the vertebra towards the rod. The polyaxial vertebral claw that we are presenting here is a self-stabilising implant that provides the same primary stability as the screw and allows application of multidirectional drawback forces.

Materials and methods: The system consists of self-stabilising vertebral anchors, either screws or claws. Each anchor is polyaxial and features a threaded extension that allows translation of the vertebra towards the rod. Connection of the screw or claw to the rod is provided by connecting clamps. The first operative step consists of inserting the vertebral anchors, favouring the apex of the deformity. The insertion technique is described in detail. The claw is locked independently, prior to securing the rod on to the claw. The second operative step consists of positioning the rods which are bent to the ideal sagittal curve. Polyaxiality and threaded extensions make rod positioning an easy step. Progressive tightening of the nuts results in correction of the deformity as it slowly moves the vertebrae towards the rods. The translation force is distributed over all the anchors, ensuring a gentle reduction manoeuvre with no risk of back out of the implants. Approaching vertebrae at the end of the reduction manoeuvre results in vertebral derotation. It is not necessary to use distraction which is considered hazardous.

Results: 35 such instrumentations have been used in patients with idiopathic scoliosis over the previous 12 months. We have used an average of nine screws and four claws per patient, mainly thoracic pedicle/transverse claws. Main curve correction was 71% (average curve was 59° preoperatively and 17° postoperatively). Average correction of the uninstrumented lumbar curve was 73%. The upper curve improved from 34° to 15°. The slope of the first uninstrumented vertebra was 14° pre-operatively and 6° postoperatively. In the sagittal plane, the average angle of thoracic kyphosis in hollow backs (kyphosis less than 15°) was 9°, increasing up to 27° postoperatively.

Discussion: This instrumentation is characterised by stable implants which provide a quality of reduction similar to that achieved with pedicle screws. Vertebral claws are easy to insert and have a better primary stability than screws.

Poly-axiality is a common feature to all the implants of this system; it greatly facilitates placement of the implants and allows to apply traction simultaneously to all the anchors, which results in progressive, gentle reduction. Simultaneous traction application ensures adequate correction of the thoracic kyphosis (gain of 18°). As a matter of fact, severe kyphosis can be bent into the rods, and translation of the vertebrae towards the rods is very easy. Adequate reduction of the main curve results in correction of the underlying lumbar curve and shifting of the first uninstrumented vertebra into a more horizontal position.

Conclusion: This instrumentation based on stable poly-axial implants, should allow to improve the quality of reduction of scoliosis.