Radiographic Analysis of Psoas Morphology and its Association With Neurovascular Structures at L4-5 With Reference to Lateral Approaches
Bibliographic record
Abstract
STUDY DESIGN: Retrospective imaging review. OBJECTIVE: Utilize magnetic resonance imaging (MRI) to expand the anatomical description of psoas morphology and its association with neurovascular structures at L4-5. SUMMARY OF BACKGROUND DATA: Anatomical psoas muscle variants may present a greater risk of neurovascular injury at the L4-5 level during lateral transpsoas approaches. METHODS: Axial L4-5 sections of consecutive patients who obtained lumbar MRIs were analyzed. Teardrop psoas morphology was assessed qualitatively. MRI described psoas morphology and proximity of neurovascular structures, whereas plain radiographs were evaluated for lumbosacral transitional vertebrae (LSTV). Teardrop morphology was tested for associations with radiographic measurements using t tests and χ analysis. RESULTS: Fifty teardrop and 476 nonteardrop psoas muscles were identified. Teardrop morphology was associated with greater longitudinal length (53.1 vs. 49.3 mm, P = 0.012), and shorter transverse length (34.9 vs. 44.8 mm, P < 0.001) compared with nonteardrop. Teardrop morphology was associated with anterior and lateral migration of the psoas with greater distance between the anterior borders of the psoas and disc (13.5 vs. 6.3 mm, P < 0.001), and greater distance between the medial border of the psoas to the lateral disc border (1.6 vs. 0.5 mm, P < 0.001). Teardrop morphology was associated with a higher incidence of the lumbar plexus migrating anteriorly adjacent to the middle-third of the disc (43.4% vs. 17.6%, P < 0.001) and the iliac vasculature being more laterally and posteriorly located, adjacent to the anterior-third of the disc (43.4% vs. 30.0%, P = 0.047). Teardrop morphology was not associated with presence of LSTV (3.8% vs. 7.6%, P = 0.306). CONCLUSION: The current study provides detailed metrics of teardrop psoas muscles and surrounding structures. The study confirms that the presence of teardrop anatomy on L4-5 axial imaging is associated with anterior migration of the lumbar plexus and posterolateral migration of the iliac vasculature which may increase the risk of neurovascular injury during direct and oblique-lateral lumbar spine procedures. LEVEL OF EVIDENCE: 3.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".