Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae.

OBJECTIVES: Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). MATERIALS AND METHODS: A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. RESULTS: Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. CONCLUSION: Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine.Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res 2016;5:419-426.

[Reproducibility of readings of ISO C 3D and CT lumbar pedicle screw scans]. / Reproduzierbarkeit der Befundung von lumbalen Pedikelschraubenpositionen mit ISO C 3D und CT.

PURPOSE: This study was conducted to evaluate the reproducibility of the reading of lumbar pedicle screw scans using a C-arm-based imaging system in comparison to computed tomography. The influence of the technique and the experience of the rater should be determined. MATERIALS AND METHODS: The lumbar spines of 23 patients were stabilized using 102 pedicle screws. The position of the screws was controlled intraoperatively using an Arcadis Orbic 3D scanner. All scans were evaluated independently by three raters. The position of the implants in reference to the pedicle walls was described. Additionally, another 100 lumbar pedicle screws in 16 patients were evaluated postoperatively with a multirow CT. Kappa according to Fleiss was calculated for the reproducibility of the rater statements. Each rater repeated the analysis of 24 screws to assess the intraobserver variance. RESULTS: The reports of the CT scans showed significantly less variation. The consent of all 3 raters was achieved in 79.4 vs. 65.1 % of cases. The Kappa values were 0.56 and 0.29, respectively. Poor results were obtained especially for the medial pedicle wall (consent 70.0 vs. 50.0 %). The influence of the experience of the rater was not able to be verified. CONCLUSION: The image quality of the ISO C 3D is worse than that of multirow CT scans for the evaluation of lumbar pedicle screws. This causes greater variance among the rater reports. We stopped using the ISO C 3D technique intraoperatively for the implantation of lumbar pedicle screws.

Peri-prosthetic bone density after implantation of a custom-made femoral component. A five-year follow-up.

Peri-prosthetic bone loss caused by stress shielding may be associated with aseptic loosening of femoral components. In order to increase primary stability and to reduce stress shielding, a three-dimensional, cementless individual femoral (Evolution K) component was manufactured using pre-operative CT scans. Using dual energy x-ray absorptiometry, peri-prosthetic bone density was measured in 43 patients, three months, six months, 3.6 and 4.6 years after surgery. At final follow-up there was a significant reduction in mean bone density in the proximal Gruen zones of -30.3% (zone 7) and -22.8% (zone 1). The density in the other zones declined by a mean of between -4% and -16%. We conclude that the manufacture of a three-dimensional, custom-made femoral component could not prevent a reduction in peri-prosthetic bone density.

Multiple skeletal metastases from a giant cell tumour of the distal fibula with fatal outcome.

A giant cell tumour is a primary lesion of bone of intermediate severity. Its histogenesis is unclear. In a few cases pulmonary metastases have been described. Multiple skeletal metastases in the absence of sarcomatous change have been observed. We present a case report of a 25-year-old woman with a recurrent giant cell tumour of the distal fibula. After a second recurrence and six years after the initial diagnosis, she rapidly developed multiple bony metastases. The outcome was fatal.