Central Fixation Element Type and Size Affect Glenoid Baseplate Micromotion in Reverse Shoulder Arthroplasty
Bibliographic record
Abstract
Reverse shoulder arthroplasty (RSA) is typically performed in patients with injured or deficient rotator cuff muscles. Loosening remains to be one of the principal modes of implant failure and the main complication leading to revision. The objective of this study was to mechanically evaluate factors affecting baseplate fixation to inform clinicians of possible implant configurations that may decrease micromotion and reduce the risk of loosening. Delta XTEND™ baseplates (DePuy Synthes) were implanted into Sawbones™ polyurethane foam blocks (N = 40) and varied in terms of their method of central fixation (screw vs. peg), central length (13.5 vs. 23.5 mm), anterior-posterior peripheral screw type (nonlocking vs. locking), and bone density (10 vs. 25 pcf). Samples were cyclically loaded under compression and shear with a 500 N force at 60° to simulate peak loads during shoulder abduction. Implant-bone motion was measured using four linear variable differential transformers. A theoretical plane was used to interpolate micromotion at the four peripheral screw positions for each sample. Micromotion measurements yielded a mean absolute percentage error (MAPE) of (9.5 ± 2.6)%; average displacements at the implant-bone interface were analyzed with a Kruskal-Wallis H test and nonparametric univariate analysis (α = 0.05). Central peg fixation generated greater micromotion at all four screw positions when compared to central screw fixation (p < 0.001). Furthermore, 13.5 mm central elements generated greater micromotion at all four measurement positions than 23.5 mm samples (p = 0.001). A significant interaction existed between the method of central fixation and central element length at all four screw positions (p < 0.001), as well as between peripheral screw type and bone density at all four screw positions (p = 0.015). Use of a central compression screw and a greater central element length that engages with the cortex of the scapula may provide improved baseplate fixation and reduce interface micromotion. Use of locking screws in the anterior and posterior positions may also offset loss of fixation due to lower bone quality. Future work that considers other baseplate factors may reveal additional surgical considerations and factor interactions.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| 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) | 0.001 | 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".