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This is an experimental study on human cadaver spines. The objective of this study is to compare the pullout forces between three screw augmentation methods and two different screw designs. Surgical interventions of patients with osteoporosis increase following the epidemiological development. Biomechanically the pedicle provides the strongest screw fixation in healthy bone, whereas in osteoporosis all areas of the vertebra are affected by the disease. This explains the high screw failure rates in those patients. Therefore PMMA augmentation of screws is often mandatory. This study involved investigation of the pullout forces of augmented transpedicular screws in five human lumbar spines (L1-L4). Each spine was treated with four different methods: non-augmented unperforated (solid) screw, perforated screw with vertebroplasty augmentation, solid screw with vertebroplasty augmentation and solid screw with balloon kyphoplasty augmentation. Screws were augmented with Polymethylmethacrylate (PMMA). The pullout forces were measured for each treatment with an Instron testing device. The bone mineral density was measured for each vertebra with Micro-CT. The statistical analysis was performed with a two-sided independent student t test. Forty screws (10 per group and level) were inserted. The vertebroplasty-augmented screws showed a significant higher pullout force (mean 918.5 N, P = 0.001) than control (mean 51 N), the balloon kyphoplasty group did not improve the pullout force significantly (mean 781 N, P > 0.05). However, leakage occurred in some cases treated with perforated screws. All spines showed osteoporosis on Micro-CT. Vertebroplasty-augmented screws, augmentation of perforated screws and balloon kyphoplasty augmented screws show higher pullout resistance than non-augmented screws. Significant higher pullout forces were only reached in the vertebroplasty augmented vertebra. The perforated screw design led to epidural leakage due to the position of the perforation in the screw. The position of the most proximal perforation is critical, depending on screw design and proper insertion depth. Nevertheless, using a properly designed perforated screw will facilitate augmentation and instrumentation in osteoporotic spines.

We report a prospective, stratified study of 60 PCA-cups and 60 RM-polyethylene cups which have been followed for a median time of 90 months, with annual radiography.The radiological migration of cups was measured by the computer-assisted EBRA method. A number of threshold migration rates from 1 mm in the first year to 1 mm in five years have been assessed and related to clinically determined revision rates. A total of 28 cups showed a total migration of 1 mm or more within the first two years; 13 of these cups have required revision and been exchanged. The survival curves of cups which had previously shown early migration were considerably different from those without early migration. For cups with a migration of less than 1 mm within the first two years the mean survival at 96 months was 0.96 ± 0.02; for migrating cups, it was 0.63 ± 0.11 (log-rank test, p = 0.0001; chi-square value = 39.4).Early migration is a good predictor for late loosening of hip sockets.

We asked 78 chronic low back pain patients to report on their usual pain intensity, and on the lifestyle changes caused by their pain, on a horizontally-oriented visual analogue scale (VAS). Also, the usual and the current pain intensities were examined on a vertical VAS. Statistical analysis showed normal distribution of data in the measurement of usual pain on the horizontal VAS, but no homogeneous distribution on the vertical VAS. Therefore, in the measurement of chronic low back pain VAS should be used horizontally rather than vertically, because of higher sensitivity. The intensity of usual pain was significantly correlated with the degree of lifestyle change. No correlation was found between current and usual pain. There was no significant difference in the failure rate between the vertical and horizontal VAS. Also, there was no reduction of the failure rate by giving additional oral explanations in the use of the scale to the patient. Owing to a negative influence in distribution of rates and an increase in the failure rate, complex questions should be avoided. A short written introduction to the scale is sufficient, and oral explanations are not essential.

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