Viola Bullmann

Dual-rod correction and instrumentation of idiopathic scoliosis with the Halm-Zielke instrumentation

Study Design. A prospective clinical and radiographic evaluation of 45 consecutive patients with idiopathic adolescent and adult scoliosis treated with anterior dual-rod Halm-Zielke instrumentation. Objectives. Clinical and radiographic evaluation with a minimum follow-up of 2 years. Summary of Background Data. Halm-Zielke instrumentation was developed to eliminate the disadvantages of Zielke instrumentation in terms of lack of primary stability and a kyphogenic effect. Methods. All patients underwent an identical anterior surgical technique with the Halm-Zielke instrumentation of the primary curve. The system is composed of a lid-plate, which is fixed to the lateral aspect of the vertebral body with two screws: a sunk screw anteriorly and a ventral derotation spondylodesis (VDS) screw posteriorly. The lid-plate design provides the lowest possible implant profile. The longitudinal components consist of a threaded rod and a solid, fluted rod. Correction is performed with both the threaded and the solid rod. The solid rod allows derotation and correction of the sagittal plane and provides primary stability. Results. Preoperative curves ranged from 35° to 92° Cobb angle. Final correction of the frontal plane averaged 67% within the instrumented levels and 59% for the total primary curve. The apical vertebral rotation of the primary curve was corrected by 52% on average without loss of correction during follow-up. Thoracolumbar kyphosis was present in 11 patients and corrected in all cases from an average of 20° to 2° after surgery and to 8° at follow-up. We observed two cases of implant failure with one resulting in a pseudarthrosis. Conclusion. Halm-Zielke instrumentation proved to be a major improvement of the original VDS-Zielke. It eliminates the kyphogenic effect and provides primary stability.

Revision of cannulated and perforated cement-augmented pedicle screws: a biomechanical study in human cadavers.

Study Design. Biomechanical investigation of primary and revised cement-augmented pedicle screws in comparison with unaugmented screws. Objective. To evaluate revision of cannulated pedicle screws and investigate cement-augmented and nonaugmented screws biomechanically, testing the torque of primary screws and axial pullout force of revised screws in cadaver vertebrae. Summary of Background Data. Cement augmentation increases the pullout force and stability of pedicle screws in vertebrae with low bone mineral density, but surgeons are concerned about complications during revision. Methods. Bone mineral density was measured using quantitative computed tomography (CT) in 23 osteoporotic thoracolumbar junction vertebrae from human cadavers. Cannulated pedicle screws, augmented with bone cement (on right) or unaugmented (left), were inserted into each vertebra. After CT control, extraction torque was measured and the pedicles were reinstrumented with larger-diameter screws. The right screws were augmented again, with another CT control, before pullout testing. Results. Mean vertebral bone density was 52.6 mg/cm3. No major screw malpositioning was observed on primary CTs. Cement leakage was observed anterolaterally and into the spinal canal. Mean maximal torque in augmented screws (1.2 Nm, SD: 0.6) differed significantly from nonaugmented screws (0.8 Nm, SD: 0.6). Screw removal did not lead to vertebral destruction. No relevant changes due to positioning or leakage were observed on CT after revision procedures compared with primary findings. Maximal pullout force in revised augmented screws (713.2 N, SD: 254.6) differed significantly compared with nonaugmented screws (554.0 N, SD: 296.5). Bone damage was observed in several vertebrae during pullout force testing in augmented screws. Conclusion. Revision of cement-augmented pedicle screws was feasible without bone destruction, and larger-diameter screws can be used in revision procedures. The pullout force after revision was significantly better in cement-augmented screws. During pullout testing, the cement-bone interface broke before the screw-cement interface in several vertebrae, fracturing the pedicles.

Validation of the pain sensitivity questionnaire in chronic pain patients.

Summary Pain Sensitivity Questionnaire scores correlate with results of experimental pain testing and reflect generalized enhancement of pain perception in chronic pain patients. ABSTRACT Recently, a self‐rating measure for pain perception based on imagined painful daily life situations, the Pain Sensitivity Questionnaire (PSQ), has been developed and shown to correlate with experimentally obtained pain intensity ratings in healthy subjects. Here, we assessed the validity of the PSQ for investigation of general pain perception (ie, pain perception outside the site of clinical pain) in chronic pain patients. PSQ scores were obtained in 134 chronic pain patients and compared to those of 185 healthy control subjects. In a subgroup of 46 chronic pain patients, we performed experimental pain testing outside the clinical pain site, including different modalities (heat, cold, pressure, and pinprick) and different measures (pain thresholds, pain intensity ratings). Results show that PSQ scores were significantly correlated with both experimental pain intensity ratings (Pearson’s r = 0.71, P < .001) and experimental pain thresholds (r = −0.52, P < .001). In addition, chronic pain patients exhibited significantly elevated PSQ scores as compared to healthy controls, consistent with the generalized increase of experimentally determined pain perception that has repeatedly been reported in chronic pain patients. These results demonstrate that the PSQ constitutes a valid self‐rating measure of pain perception outside the clinical pain site in chronic pain patients and might serve as an alternative to experimental assessment of pain perception outside the clinical pain site in situations where experimental pain testing is not feasible.

Raster stereography versus radiography in the long-term follow-up of idiopathic scoliosis.

Study Design Raster-stereographic and radiographic evaluation of idiopathic scoliosis without braces in a retrospective longitudinal long-term follow-up study. Objective To investigate the reliability and accuracy of raster stereography in comparison with radiography as the gold standard, using a longitudinal long-term study design in idiopathic scoliosis, to reduce the number of radiographs required during follow-up in scoliosis patients. Summary of Background Data It has been confirmed that raster stereography produces reliable data in patients with conservatively and surgically treated idiopathic scoliosis, up to a Cobb angle of 80 degrees. This means that the method can be used to replace radiography during the follow-up in these patients. However, no data have yet been published on the use of raster stereography in a longitudinal setting during a long-term follow-up period in comparison with radiography as the gold standard. Methods Raster stereographs and digitized anterior-posterior radiographs of 16 patients with idiopathic scoliosis were studied retrospectively in a longitudinal study design, with a mean follow-up period of 8 years (range 3 to 10 y). Lateral vertebral deviation and vertebral rotation were measured between C7 and L4 using raster stereography and radiography, compared with Cobb angles, and correlated. Results During the follow-up period, the Cobb angle increased on average by 13 degrees. The progression of lateral vertebral deviation measured using both techniques, and that of vertebral rotation measured with radiography, was greater than that of the Cobb angle, whereas that of raster-stereographic vertebral rotation was lower. However, there was an excellent correlation between the raster-stereographic and radiographic progression of these parameters (R2≥0.5). The mean difference between raster stereographs and radiographs was 3.21 mm for lateral vertebral deviation and 2.45 degrees for vertebral rotation. Conclusions Using the parameters of lateral vertebral deviation and vertebral rotation, raster stereography accurately reflects the radiographically measured progression of idiopathic scoliosis during the long-term follow-up, but these parameters are not directly comparable with the Cobb angle. In the follow-up of scoliosis patients, the authors would recommend a raster-stereographic examination every 3 to 6 months and a radiographic examination every 12 to 18 months only, provided that raster stereography does not show rapid deterioration of the scoliosis. The patients radiation exposure can be reduced using this approach.

Spontaneous correction and derotation of secondary curves after selective anterior fusion of idiopathic scoliosis.

Study Design. Clinical, rasterstereographic, and radiographic evaluation of spontaneous vertebral derotation of secondary curves in idiopathic scoliosis following selective anterior correction and fusion of the primary curve. Objective. To quantify spontaneous vertebral derotation in secondary curves after selective anterior correction with attention to cosmetic outcome. Summary of Background Data. While the derotational effect of anterior instrumentation techniques on the instrumented curve is well understood, there is a paucity on data of the rotational behavior of the noninstrumented secondary curves. Methods. A total of 43 patients with idiopathic scoliosis (16 with thoracic curves in group 1 and 27 with thoracolumbar/lumbar curves in group 2) underwent selective anterior instrumentation. Vertebral rotation was analyzed before surgery and, on average, 20 months after surgery using digital radiometric rotation analysis, back shape analysis with rasterstereography, and scoliometer measurement. Results. In Group 1, there was a significant spontaneous vertebral derotation of the secondary lumbar curves by 14.2% (range from 12.7° to 10.9°) in the digital radiometric rotation analysis, surface derotation amounted to 49% (range from 9.6° to 4.9°) in the rasterstereography, and to 70% in the clinical scoliometer measurement (range from 8.0° to 2.4°). In group 2, there was an increase of rotation of the noninstrumented secondary thoracic curves by 30% (range from 5.0° to 6.5°) in digital radiometry, by 32.9% in the rasterstereography (range from 8.5° to 11.3°), and a 28.3% increase in scoliometer measurement (range from 6.0° to 7.7°). Conclusion. Selective anterior instrumentation and fusion of primary thoracic curves results in satisfactory spontaneous vertebral and high surface derotation of the secondary lumbar curves. However, in primary thoracolumbar or lumbar curves, an increase of both vertebral and surface rotation of the secondary thoracic curve was noted. This increase can impair cosmetic outcome.

Rasterstereographic analysis of axial back surface rotation in standing versus forward bending posture in idiopathic scoliosis

The forward bending test according to Adams and rib hump quantification by scoliometer are common clinical examination techniques in idiopathic scoliosis, although precise data about the change of axial surface rotation in forward bending posture are not available. In a pilot study the influence of leg length inequalities on the back shape of five normal subjects was clarified. Then 91 patients with idiopathic scoliosis with Cobb-angles between 20° and 82° were examined by rasterstereography, a 3D back surface analysis system. The axial back surface rotation in standing posture was compared with that in forward bending posture and additionally with a scoliometer measurement in forward bending posture. The changes of back shape in forward bending posture were correlated with the Cobb-angle, the level of the apex of the scoliotic primary curve and the age of the patient. Averaged over all patients, the back surface rotation amplitude increased from 23.1° in standing to 26.3° in forward bending posture. The standard deviation of this difference was high (6.1°). The correlation of back surface rotation amplitude in standing with that in forward bending posture was poor (R2=0.41) as was the correlation of back surface rotation in standing posture with the scoliometer in forward bending posture measured rotation (R2=0.35). No significant correlation could be found between the change of back shape in forward bending and the degree of deformity (R2=0.07), likewise no correlation with the height of the apex of the scoliosis (R2=0.005) and the age of the patient (R2=0.001). Before forward bending test leg length inequalities have to be compensated accurately. Compared to the standing posture, forward bending changes back surface rotation. However, this change varies greatly between patients, and is independent of the type and degree of scoliosis. Furthermore remarkable differences were found between scoliometer measurement of the rib hump and rasterstereographic measurement of the vertebral rotation. Therefore the forward bending test and the identification of idiopathic scoliosis rotation by scoliometer can be markedly different compared to rasterstereographic surface measurement in the standing posture.

The position of the aorta relative to the spine before and after anterior instrumentation in right thoracic scoliosis.

Study Design. Preoperative magnetic resonance images (MRI) and postoperative axial computed tomography (CT) scans in 25 consecutive patients with idiopathic right thoracic adolescent scoliosis (AIS) and anterior correction and fusion with a dual rod system were analyzed in a prospective study. Objectives. Evaluation of the spatial relations between the vertebral body and the aorta and the relative migration of the aorta due to the anterior correction and instrumentation in right thoracic scoliosis patients. Summary of Background Data. In anterior scoliosis surgery, bicortical screw purchase is performed to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. For a safe screw placement, knowledge of both the preoperative topographic relation of aorta and vertebral body and its changes due to surgical correction is crucial. Recent studies reported on a more lateral and posterior position of the aorta in AIS patients. However, there are hardly any data on the changes of the aortic position after anterior curve correction available in the current literature. Methods. All 25 patients underwent an identical anterior surgical technique with standard open approach and dual rod instrumentation of the primary curve. Preoperative MRI and postoperative sequential CT scans of 180 vertebrae were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, closest distance between aorta and the vertebral body, the aorta-vertebral angle, and the position of the aorta in relation to the spinal canal. Results. Before surgery, the aorta is positioned posterolaterally with an aorta-vertebral angle of between 78° and 92° (between T5 and T10). Between T11 and L2, the aorta is positioned more anteromedially with an aorta-vertebral angle from 62° (T11) to 16° (L2). After surgery, the aorta has migrated from a posterolateral to a more anteromedial position. This migration is maximal at the apex vertebra with an average change of the aorta-vertebral angle of 31.4°. Whereas the distance between the aorta and the vertebral body increases at the upper and lower fusion levels, the aorta moves significantly closer to the vertebral body at the curve apex due to surgical correction. In patients with thoracic hypokyphosis, the aorta is positioned significantly more posterior than in patients with hyperkyphosis. Conclusions. This MRI and CT based study of 25 patients with thoracic AIS treated by standard open dual rod and dual screw instrumentation demonstrates a migration of the aorta by 31° from a more posterolateral position before surgery to a more anteromedial position after surgery at the curve apex. Scoliosis surgeons should be aware of these changes; any excessive contralateral screw penetration must be avoided at any level.

Anterior dual rod instrumentation in idiopathic thoracic scoliosis: a computed tomography analysis of screw placement relative to the aorta and the spinal canal.

Study Design. Axial computed tomography scans (CT) in 20 consecutive patients with idiopathic right thoracic scoliosis and anterior correction and fusion with a dual rod dual screw system. Objectives. CT evaluation of screw position in anterior dual rod instrumentation relative to the aorta and the spinal canal. Summary of Background Data. In anterior scoliosis surgery, bicortical screw purchase is used to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. Data on the accuracy of dual screw instrumentation in thoracic scoliosis are missing. Methods. All 20 patients underwent an identical anterior surgical technique with double thoracotomy approach and dual rod instrumentation of the primary curve. Postoperative sequential CT scans were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, distance from the aorta to the closest point of the vertebral body cortex, distance between the tip of the screws and the aorta, distance between the screw and the spinal canal, and the amount of contralateral screw penetration. A total amount of 226 screws were evaluated. Results. All screws were placed correctly without any critical proximity to the aorta or spinal canal. A total of 198 of 226 screws (88%) had a bicortical purchase. Thirteen screw tips (5.8%) were within 1 to 3 mm proximity to the aorta. All other screws were more than 3 mm distant from the aorta. The closest proximity of the screw tips to the thoracic aorta was found at the upper end vertebrae (T5, T6, or T7). There were no screws perforating the spinal canal. Conclusion. Anterior instrumentation and correction of thoracic scoliosis with a dual rod dual screw system enable a correct and safe screw placement using a standard open approach. Excessive bicortical screw perforation should be avoided in order not to endanger the thoracic aorta.

Giant Cell Tumors of the Axial Skeleton

Background. We report on 19 cases of giant cell tumor of bone (GCT) affecting the spine or sacrum and evaluate the outcome of different treatment modalities. Methods. Nineteen patients with GCT of the spine (n = 6) or sacrum (n = 13) have been included in this study. The mean followup was 51.6 months. Ten sacral GCT were treated by intralesional procedures of which 4 also received embolization, and 3 with irradiation only. All spinal GCT were surgically treated. Results. Two (15.4%) patients with sacral and 4 (66.7%) with spinal tumors had a local recurrence, two of the letter developed pulmonary metastases. One local recurrence of the spine was successfully treated by serial arterial embolization, a procedure previously described only for sacral tumors. At last followup, 9 patients had no evidence of disease, 8 had stable disease, 1 had progressive disease, 1 died due to disease. Six patients had neurological deficits. Conclusions. GCT of the axial skeleton have a high local recurrence rate. Neurological deficits are common. En-bloc spondylectomy combined with embolization is the treatment of choice. In case of inoperability, serial arterial embolization seems to be an alternative not only for sacral but also for spinal tumors.

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.