[Specific spondylitis]. / Spezifische Spondylitis.

Tuberculosis of the spine usually occurs with a latency period after primary infection with tuberculosis (TB) and the most frequent agent is Mycobacterium tuberculosis. The rate of TB has increased due to the impact of acquired immunodeficiency syndrome (AIDS) and more than 50% of skeletal tuberculosis is localized in the spine. Spinal tuberculosis was discovered by Pott in 1776. Magnetic resonance imaging (MRI) with gadolineum is the most sensitive imaging method. Diagnostic accuracy is given by direct detection of Mycobacterium tuberculosis by punction or biopsy. Granuloma of the spine can lead to abscesses, severe spinal deformity with instability and potentially paraplegia. Chemotherapy is effective with a minimum duration of 6-12 months. In cases with neurological deficits and severe deformity there is an additional indication for surgical therapy. In the acute phase a posterior instrumentation, anterior debridement and reconstruction of the defect is indicated. After recovery of the spinal tuberculosis Pott's kyphosis could remain and operative correction can be managed by pedicle substraction osteotomy.

[Pedicle screw augmentation from a biomechanical perspective]. / Pedikelschraubenaugmentation aus biomechanischer Sicht.

Severe osteoporosis is a serious problem in the instrumentation during spine surgery. Besides kyphosis, adjacent vertebral fractures and of course pedicle screw loosening and implant pullout are frequent challenges in instrumentation of the osteoporotic spine. In addition to screw diameter and length, bone mineral density has the most important impact on the stability of a pedicle screw. In cases of severe osteoporosis cement augmentation increases the stability of a pedicle screw. Pullout force can be increased with augmentation by 96-278%. Nowadays, there are two different procedures for augmentation: cement augmentation of the vertebra before inserting the screw into the soft, fresh cement or augmentation via a perforated screw that has already been inserted.The main problem in augmentation techniques are cement leakages. In both techniques leakages may occur. The problem of leakages seems to be less severe in the augmentation technique via the perforated screw, because cement application can be stopped immediately if the onset of leakage is noticed. Even surgical revision of cement augmented screws is not a major clinical problem based on recent biomechanical studies. The revision screw can be chosen 1 mm thicker and can be cement augmented again without technical problems.

[Posterior operative correction of idiopathic scoliosis. Value of pedicle screws versus hooks]. / Dorsale operative Korrektur der idiopathischen Skoliose. Stellenwert von Pedikelschrauben vs. Haken.

Posterior correction and fusion of scoliosis with multisegmental instrumentation systems was developed by Cotrel-Dubousset in the 1980s. Initially correction and instrumentation was performed using hooks only. Later pedicle screws were implemented first for the lumbar and then for the thoracic spine. Nowadays instrumentation based on pedicle screws only is well established for posterior scoliosis surgery. Biomechanical studies demonstrated higher pull-out forces for pedicle than for hook constructs.In clinical studies several authors reported better Cobb angle correction of the primary and the secondary curves and less loss of correction in pedicle screw versus hook instrumentations. Furthermore, pedicle screw instrumentation allows fewer segments to be fused, especially caudally, and thus saving mobile segments. In most of these publications there were no differences in operation time, blood loss and complication rates. In summary, there is better curve correction without an increased risk using multisegmental pedicle screw instrumentation in modern posterior scoliosis surgery.

Morphometric analysis of thoracic and lumbar vertebrae in idiopathic scoliosis.

STUDY DESIGN: Prospective study on the morphometry of 337 pedicles in 29 patients with idiopathic scoliosis. OBJECTIVES: To analyze by means of computed tomographic scans the vertebral morphometry in idiopathic scoliosis treated by pedicle screw instrumentation. SUMMARY OF BACKGROUND DATA: Although several studies exist on the vertebrae's morphometry in normal spines, little is known concerning the morphometry of scoliotic vertebrae. METHODS: The pedicles' morphometry between T5 and L4 was analyzed by computed tomographic scans in 29 surgically treated patients with idiopathic right thoracic scoliosis. Measurements included chord length, endosteal transverse pedicle width, transverse pedicle angle, and pedicle length. RESULTS: The endosteal transverse pedicle width was significantly smaller (P < 0.05) on the concavity in the apical region of the thoracic spine and measured between 2.5 and 4.2 mm in the middle thoracic spine (T5-T9) and between 4.2 and 5.9 mm in the lower thoracic spine (T10-T12). In the lumbar spine, the width varied between 4.8 and 9.5 mm without significant differences between the concave and convex sides (P > 0.05). The chord length was shortest at T5, measuring 37 mm and increased gradually to 50 mm at L3 with significantly larger dimensions in male patients and on the concavity of the apical region in the thoracic spine (P < 0.05). The pedicle length varied minimally, with a range of between 20 and 22 mm, and was relatively consistent throughout the thoracic and lumbar spine. The transverse pedicle angle varied between 6 degrees in the lower thoracic spine and 12 degrees in the upper thoracic and lower lumbar spine. CONCLUSION: The morphometry in scoliotic vertebrae is substantially different from that of vertebrae in normal spines, with an asymmetrical intravertebral deformity shown in scoliotic vertebrae. Pedicle screw instrumentation on the concavity in the apical region of thoracic curves appears critical because of the small endosteal pedicle width.

Pedicle screw instrumentation of the thoracic spine in idiopathic scoliosis.

STUDY DESIGN: A prospective study of the accuracy of thoracic pedicle screw placement in patients with idiopathic scoliosis. OBJECTIVES: To evaluate the accuracy of thoracic pedicle screw placement in the surgical management of idiopathic scoliosis and to establish its risks and benefits. SUMMARY OF BACKGROUND DATA: Lumbar pedicle screw instrumentation has proven to be reliable and effective in the surgical management of scoliosis. No reports exist on the accuracy and benefits of pedicle screw instrumentation of the thoracic spine in scoliosis surgery. METHODS: One hundred and twenty thoracic pedicle screws in 32 consecutively treated patients with idiopathic scoliosis were investigated immediately after surgery by computed tomography scans that were analyzed by three examiners. RESULTS: Thirty (25%) of the screws penetrated the pedicle cortex or the vertebral body anterior cortex. Ten screws (8.3%) penetrated the medial cortex of the pedicle by an average of 1.5 mm and a maximum of 3.0 mm. Seventeen screws (14.2%) penetrated laterally by an average of 2.1 mm. There were two cases of caudad penetration. Three screws penetrated the anterior vertebral cortex, of which two also penetrated the pedicle cortex. Also, one of these three screws was replaced because of its direct proximity to the thoracic aorta. There were no neurologic complications. The correlation between the pedicle cortical penetration rate and the preoperative Cobb angle, vertebral rotation or level, or site of screw insertion was statistically insignificant (P > 0.05). Curve correction in the cases of mainly hook instrumentation averaged 52.5% versus 59.2% in the cases of mainly screw instrumentation. This difference was statistically insignificant (P > 0.05). CONCLUSIONS: Pedicle or vertebral body cortical penetration occurred with 25% of the screws but with no neurologic compromise. Curve correction was slightly greater than with hooks, but not to a statistically significant extent.