Light source-induced error in computer-assisted image analysis with a video-based system

Biomechanical Evaluation of Cervical Spine Fixation After Healing in a Destabilized Cervical Spine Model in Sheep: A Comparison of the Anterior Plating and Posterior Wiring Techniques

BACKGROUND

We conducted biomechanical evaluation of the anterior plating and posterior wiring techniques for cervical spine stabilization after a course of healing in sheep.

METHODS

Seventeen sheep were included, and six of which underwent sham operations (group A, n=6). The other eleven received complete C2-C3 destabilization, followed by intervertebral bone grafting and cervical stabilization either with anterior plating (group B, n=5) or posterior wiring (group C, n=6) techniques. These animals were killed 6 months later. Ligamentous spines (C1-C5) were subjected to the relevantly applied loads. The load-deformation data of the C2-C3 and C3-C4 functional units were recorded and analyzed.

RESULTS

At the C2-C3 functional unit, group B had the least motion ranges in flexion, lateral bending, and rotation loads than did the other two groups. Significantly smaller motion ranges of lateral bending and rotation loads were found in group B than in group C (p<0.05). Compared with group A, group C had a decreased motion range in flexion load but showed increased motion range in rotation load. Consequently, group B had superior intervertebral fusion and less osteophyte than did group C. At the C3-C4 functional unit, group B showed significantly decreased motion ranges in extension and lateral bending loads (p<0.05), while group C did not.

CONCLUSION

The results indicated that the anterior plate-stabilized spines were more stable over time than did the posterior-wired spines. This biomechanical advantage eventually resulted in superior intervertebral fusion masses in the former, although it also induced a slightly decreased motion range at the contiguous functional unit. In exclusively posterior wired-spines, the weakness for opposing rotation loads might contribute to the formation of osteophytes at the fusion functional unit. These data point out that the mode and stability of implant fixation systems greatly influence the biomechanical redistribution and bone-adaptive remodeling process during healing, which are closely related to the bone graft maturation and osteophytic formations at the fusion level and the occurrence of stiffening problems at the contiguous levels.

Influence of developer exhaustion on accuracy of quantitative digital subtraction radiography: an in vitro study

OBJECTIVE

The aim of the study was to evaluate the influence of developer exhaustion on accuracy of quantitative digital subtraction radiography.

STUDY DESIGN

Six objects, each incorporating a section of dry human mandible, were radiographed with 4 exposure times. Baseline films were processed in fresh solutions, whereas follow-up films were processed in fresh and in increasingly exhausted solutions (ie, 1, 2, and 3 weeks old). Bone loss and bone gain were computer simulated in 17 regions of interest on baseline radiographs. Area and volume of changes in mineralization were measured in subtracted images, obtained by subtraction of baseline from their corresponding follow-up radiographs. Friedman's 2-way analysis of variance by ranks and Wilcoxon signed-rank test were used for statistical analysis.

RESULTS

Because of exhausted developer, bone loss was relatively underestimated from 6.6% to 16.5% (P <.05), whereas bone gain was relatively overestimated from 9.7% to 16.7% (P <.05).

CONCLUSIONS

This in vitro study demonstrates that films for quantitative digital subtraction radiography should be processed in fresh developer or error might be introduced.