DOES SPACER LENGTH OF FLEXIBLE POSTERIOR STABILIZATION SYSTEM HAVE AN EFFECT ON RANGE OF MOTION
Bibliographic record
Abstract
The Dynesys is a flexible posterior stabilization system that is designed to preserve intersegmental kinematics and reduce loading at the facet joints. The purpose of this study was to determine if the length of the Dynesys spacer has an effect on range of motion (ROM) at the implanted level. Spacer length was found to significantly affect ROM in all three loading directions with and without a follower preload. The longer spacer increased ROM and the shorter spacer decreased ROM, largely due to differences in segmental compression between the two. The Dynesys, a flexible posterior stabilization system that provides an alternative to fusion, is designed to preserve intersegmental kinematics and alleviate loading at the facet joints. Recent biomechanical evidence suggests that motion with Dynesys is less than the intact spine (Schmoelz, 2003). The purpose of this investigation was to determine if the length of the Dynesys spacer contributes to differences in range of motion (ROM) at the implanted level. Ten cadaveric lumbar spine segments (L2-L5) were tested by applying a pure moment of ±7.5Nm in three directions of loading with and without a follower preload of 600N. Test conditions included: intact, injury at L3-L4, Dynesys at L3-L4 (standard spacer), long spacer (+2mm), and short spacer (−2mm). Intervertebral rotations were measured using an optoelectronic camera. Pressure sensors placed inside the joint capsules measured facet loads. Statistical significance was determined using repeated measures ANOVA. Spacer length had a significant effect on ROM in all three loading directions with and without a follower preload. Initial contact loads within the facet joints were 150% and 64% that of the standard spacer for the short and long spacer, respectively. The magnitude of distraction of the segment affects ROM. Shorter spacers increased segmental compression of the intervertebral disc and facet joints and therefore reduced ROM. With a follower preload, the segment is further compressed and ROM is further reduced. The results contribute to an understanding of the design of such implants and could help guide future research. Funding: Synos Foundation, Switzerland, National Science and Engineering Research Council of Canada (NSERC) Please contact author for table or diagram.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".