Objectives

To determine the limits of spinal displacement before the onset of neurophysiological changes during spinal surgery. Assessing if the type of force applied or the section of the adjacent nerve roots increases the tolerance to displacement.

Purpose of the study: Fixing the pedicles can be difficult to achieve during surgical treatment of scoliosis involving the thoracic spine because of the vertebral rotation raising the risk of neurological and vascular disorders. Use of extrapedicular thoracic screws has been proposed for more adapted and safe fixation. No clinical data has been published concerning the safety of these screws.

Material and methods: This multicentric retrospective clinical and radiological study included 467 thoracic screws in 34 patients operated for scoliosis. Neurophysiological monitoring was used for all procedures. Screws were positioned free hand without radioscopic control. Pedicular screws were inserted in T10, T11, T12. Extra-pedicular screws were inserted for thoracic vertebrae above T10 to T4. Correction was achieved with rods bent in situ. The purpose of this study was to evaluate the position of the thoracic screws within the vertebral body and in relation to the great vessels and the cord. The position of the screws in the thoracic spine was studied by two independent observers reading multiple thin-slice CT images. The observers noted malposition as: 1) penetration into the canal more than 2 mm, 2) less than 1 cm hold in the vertebral body, 3) screw protrusion more than 2 mm beyond the vertebral cortical.

Results: Screw malposition was observed for 9 of 161 pedicular screws (5.4%) and for 21 of 306 (6.8%) thoracic screws. None of the screw malpositions had a clinical expression. There was one episode of thoracic effusion associated with thoracoplasty. Two patients required revision (one for poor indication and one for disincarceration). There were no postoperative deep infections. Three cases of intercostals neuralgia subsided within three months.

Conclusion: Insertion of thoracic screws for fixation and correction is a useful technique with few complications. It enables better 3D correction and better control of the deformation. Screw malposition in this series was similar to that observed with classical pedicular techniques. There was no major complication associated with thoracic screws.

Introduction and purpose: We present the results of our surgical method involving nerve decompression, reduction and circumferential spinal fusion via posterior approach for severe spondylolisthesis.

Materials and methods: We studied 14 patients with spondylolisthesis and slippage greater than 50%; mean age 24. Mean slip angle 37° and mean preoperative slip 74%.

Procedure: Via a posterior approach we performed neural decompression and placed pedicle screws in L5-S1 (in one case we instrumented L4 for associated L4-L5 spondylolisthesis) and iliac screws (except in three cases). We removed the annulus fibrosus, the L5-S1 disc and the rounded proximal edge of the sacrum. Following distraction of L5-S1 we inserted bone graft cages (from 3 to 5). We adjusted the bars with spanners to reduce slippage and achieve final curvature of the spine.

The cases were monitored with evoked potentials and epidural catheter.

We studied preoperative, postoperative and final check X-rays. The clinical histories were also reviewed.

Results: One rupture of the dura. Two patients with anterior slippage of a cage. One posterior slippage of L5 screws, without revision surgery. One postoperative infection resolved by surgical cleaning and antibiotic therapy.

After mean follow-up of 32 months the radiographic study showed no pseudoarthrosis. Final mean slippage was 15% and slip angle 5°. Ten patients had no pain or physical limitations. Two presented mild lumbar discomfort and occasional limitation.

Conclusions: The procedure we used was shown to be effective in correcting the deformity with excellent clinical results.

Background: Tibial valgus, a known complication of leg lengthening by external fixation, has been related to stability of the bonefixator system and, in particular to pin loosening. Hydroxyapatite coating has been reported to enhance the quality of the bone-pin interface. The aim of this study was to compare the incidence of axial deformity between tibial lengthening procedures with hydroxyapatite-coated and non-coated external-fixation pins.

Methods: A prospective trial was conducted on 34 symmetrical tibial lengthenings in 17 pathologically-short patients. For each pair of bones, one side to be lengthened with hydroxyapatite-coated pins and the other with standard uncoated pins were randomly selected. The bone angle in the frontal plane was measured before the operation and at the end of the fixation period. The difference was calculated and compared between lengthenings performed with coated and uncoated pins.

Results: Mean deviation into valgus of the tibiae was 6.5° with hydroxyapatite-coated pins and 12.5° with uncoated pins (p=0.023). Other factors previously related to valgus deformity did not significantly differ between groups.

Conclusions: Tibial lengthenings performed with hydroxyapatite-coated external-fixation pins are less prone to axial deviation in the frontal plane than those without it.