3-Foot Standing AP versus 45° PA Radiograph for Osteoarthritis of the Knee
Bibliographic record
Abstract
OBJECTIVE: Flexion and erect standing radiographs were evaluated in the current study to compare their sensitivity in detecting articular cartilage wear. DESIGN: Prospective cohort study. SETTING: A tertiary care hospital outpatient orthopedic clinic. PATIENTS: All patients with osteoarthritis of the knee ages 40 to 75 scheduled for arthroscopic debridement between March 1995 and November 1997 were considered for the current study. INTERVENTION: Radiographs were obtained 1 week preoperatively in both the 3-foot standing anteroposterior (AP) and a 45 degrees posteroanterior (PA) flexion weight-bearing projection. Joint space height was measured with a ruler in millimeters at the narrowest point of each compartment. All radiographs were assessed by two independent observers who were blinded to the arthroscopic findings and clinical symptoms of the subjects. MAIN OUTCOME MEASURES: Prediction accuracy of each radiograph for severe Grade IV articular cartilage wear in tibio-femoral compartments. RESULTS: One hundred fifty-two patients with a mean (+/- SD) age of 60.5+/-8.5 years were enrolled in the study. Fifty-one percent were female. Twelve patients were categorized as having severe lateral compartment articular chondropathy (Grade IV) at the time of arthroscopy. The lateral joint space height averaged 1.0+/-1.7 mm SD on the 45 degrees PA radiograph compared with 2.7+/-1.1 mm SD on the 3-foot standing AP view. Using a cutoff of 2 mm or less, the 45 degrees PA view was much more sensitive (83% versus 42%) at correctly detecting the most severe chondropathy. Forty-one patients were classified with severe Grade IV medial compartment chondropathy at arthroscopy. There was little difference in the average joint space height measured by the 45 degrees PA view (1.4+/-1.4 mm SD) or the 3-foot standing AP view (1.9+/-1.6 mm SD). A number of cutoff measures were evaluated, but no significant advantage could be found for either view in evaluating the medial compartment severity. CONCLUSIONS: The bilateral 45 degrees PA is superior for detecting lateral compartment wear but offers no advantage on the medial side. This view should be considered as the screening radiograph of choice in evaluating osteoarthritis of the knee.
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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 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".