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Reliability of Visual Estimation of the First Intermetatarsal Angle
Midori Higashi1, David Shofler2, Karim Manji3
1Resident Physician, Swedish Medical Center, Seattle, WA.
Summary
Physicians often visually estimate the first intermetatarsal (IM) angle for hallux abducto valgus surgery. This study found visual estimation is less accurate for larger angles, suggesting direct measurement is more reliable for surgical decisions.
Area of Science:
- Orthopedics
- Radiology
- Surgical Decision-Making
Background:
- The first intermetatarsal (IM) angle is crucial for surgical planning in hallux abducto valgus.
- Physicians frequently rely on visual estimation of the IM angle rather than direct measurement.
Purpose of the Study:
- To assess the accuracy of visual estimation of the radiographic first intermetatarsal (IM) angle compared to direct measurement.
- To evaluate how physician experience and angle size affect estimation accuracy.
Main Methods:
- 45 participants (students, residents, attending physicians) visually estimated IM angles (6°-19°) from radiographs.
- Interrater reliability was calculated using intraclass correlation (ICC).
- Estimation accuracy was compared between larger (>10°) and smaller (≤10°) IM angles.
Main Results:
- Attending physicians' visual estimates differed from measured values by 3.28° ± 1.56°.
- Interrater reliability (ICC) increased with experience: students (0.426), residents (0.476), attending physicians (0.656).
- Larger IM angles (>10°) were estimated less accurately (3.96° ± 1.60°) than smaller angles (3.14° ± 0.79°).
Conclusions:
- Visual estimation of the first IM angle can be inaccurate, particularly for larger angles.
- Estimation accuracy and reliability improve with clinical experience.
- Direct measurement of the IM angle is recommended for accurate surgical decision-making in hallux abducto valgus.
