Shoulder muscle synergies before and after reverse total shoulder arthroplasty
Bibliographic record
Abstract
Abstract Background Reverse total shoulder arthroplasty (rTSA) has become a standard treatment for symptomatic massive rotator cuff tears (MRCT). While clinical outcomes are generally satisfactory, significant variability in functional recovery raises questions about the extent of inter-individual neuromuscular adaptations and motor restoration. This study aimed to assess the neuromuscular impact of rTSA by analysing superficial shoulder muscle activity and synergies. Methods Asymptomatic shoulders (n=20) and symptomatic shoulders undergoing rTSA (n=20) were assessed before and after surgery. Participants performed four functional tasks while surface electromyography was used to quantified muscle activity. Synergies of the anterior (DELTA), middle (DELTM), and posterior deltoid (DELTP), middle (TRAPM) and upper trapezius (TRAPS), and serratus anterior (SERRA) were computed. Results Symptomatic MRCT was associated with a significant increase in activity of DELTM, TRAPS, and SERRA (p < 0.001). Postoperatively, DELTM (p = 0.003) and TRAPS (p = 0.039) remained significantly more active. Although the number of muscle synergies (n = 2) remained stable across groups, significant differences in muscle weightings were found preoperatively for TRAPS and DELTP (p < 0.001). Also, cosine similarity increased postoperatively by 15.96% for synergy 1 and 37.42% for synergy 2, indicating a greater resemblance to the asymptomatic synergy pattern (p < 0.001). Conclusion Changes in muscles activities and synergy patterns, marked by the emergence of compensatory roles for scapular stabilizers and the deltoid, highlight the disruption of motor control associated with MRCT. Following rTSA, motor coordination was substantially restored, supporting improved functional autonomy in daily tasks. Highlights - Muscle activation and synergy analyses reveal altered motor control in shoulders with massive rotator cuff tear. - Deltoid and scapular stabilizers show compensatory roles preoperatively. - Reverse total shoulder arthroplasty leads to partial restoration of physiological coordination patterns. - Synergy profiles shift significantly toward asymptomatic motor strategies after surgery.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".