The Importance of Spino-Pelvic Balance in L5–S1 Developmental Spondylolisthesis
Bibliographic record
Abstract
STUDY DESIGN: A review article. OBJECTIVES: The purpose of this article is to review pertinent radiologic measurements for the evaluation of spino-pelvic balance in developmental spondylolisthesis, based on the experience of the Spinal Deformity Study Group. SUMMARY OF BACKGROUND DATA: Over the past decade, pelvic morphology has been shown to significantly influence spino-pelvic balance of the human trunk in normal and pathologic conditions. This finding has important implications for the evaluation and treatment of developmental spondylolisthesis and has fostered a renewed interest in the radiologic evaluation of spino-pelvic balance in this condition. METHODS: The lateral standing radiographs of the spine and pelvis of subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence, sacral slope, pelvic tilt, L5 incidence angle, lumbosacral angle, lumbar lordosis, thoracic kyphosis, and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of an adult and child reference population. RESULTS: The pelvic shape, best quantified by the pelvic incidence angle, determines the position of the sacral endplate. The spine reacts to this position by adapting through lumbar lordosis, the amount of lordosis increasing as the sacral slope increases in order to balance the trunk in the upright position. Pelvic incidence, sacral slope, pelvic tilt, and lumbar lordosis are found to be significantly greater in subjects with developmental spondylolisthesis, while thoracic kyphosis is significantly lower when compared to a reference population. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases, suggesting that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Studies also indicate that pelvic incidence is unaffected by surgical reduction and instrumentation. Pelvic tilt, sacral slope, and thoracic kyphosis are slightly affected, while grade, L5 incidence angle, lumbosacral angle, and shape of the lumbar spine are significantly improved after surgery. A postoperative improvement in L5 incidence angle and lumbosacral angle appears correlated with a better outcome while subjects with a poor outcome have a higher preoperative grade. CONCLUSIONS: Spino-pelvic balance in the sagittal plane can be considered as an open linear chain linking the head to the pelvis where the shape and orientation of each successive anatomic segment are closely related and influence the adjacent segment. Pelvic morphology and spino-pelvic balance are abnormal in developmental spondylolisthesis. These abnormalities should be quantified on lateral standing radiographs of the spine and pelvis and have important implications for the evaluation and treatment of this pathologic condition.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".