The Epidemiology, Risk of Recurrence, and Functional Outcome After an Acute Traumatic Posterior Dislocation of the Shoulder
Bibliographic record
Abstract
BACKGROUND: Posterior glenohumeral dislocation is less common than anterior dislocation, and less is known about its epidemiology, functional outcome, and complications. The purposes of this study were to determine the epidemiology and demographics of posterior dislocations and to assess the risk of recurrence and the functional outcome after treatment. METHODS: We performed a retrospective review of a prospective audit of the cases of 112 patients who sustained 120 posterior glenohumeral dislocations. Patients were treated with relocation, immobilization, and then physical therapy. Functional outcome was assessed with the Western Ontario Shoulder Instability Index (WOSI) and the limb-specific Disabilities of the Arm, Shoulder and Hand score (DASH) during the two years after the dislocation. RESULTS: The prevalence of posterior dislocation was 1.1 per 100,000 population per year, with peaks in male patients between twenty and forty-nine years old, and in the elderly patients over seventy years old. Most dislocations (67%) were produced by a traumatic accident, with most of the remainder produced by seizures. Twenty patients (twenty-three shoulders) developed recurrent instability. On survival analysis, 17.7% (95% confidence interval, 10.8% to 24.6%) of the shoulders developed recurrent instability within the first year. On multivariable analysis, an age of less than forty years, dislocation during a seizure, and a large reverse Hill-Sachs lesion (>1.5 cm3) were predictive of recurrent instability. Small persistent functional deficits were detected with the WOSI and DASH at two years. CONCLUSIONS: The prevalence of posterior dislocation is low. The most common complication after this injury is recurrent instability, which occurs at an early stage in 17.7% of shoulders within the first year after dislocation. The risk is highest in patients who are less than forty years old, sustain the dislocation during a seizure, and have a large humeral head defect. The risk is lower for most patients who sustain the injury from a traumatic accident, especially if they are older and have a small anterior humeral head defect. There are persistent deficits of shoulder function within the first two years after the injury.
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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 | 0.008 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".