## Radiographic Discrimination: Rigid vs Flexible CTEV ### The Talus-First Metatarsal Angle (TMA) **Key Point:** The talus-first metatarsal angle (TMA) on the anteroposterior radiograph is the most sensitive radiographic discriminator between rigid and flexible CTEV. A TMA > 30° indicates significant forefoot adduction and is characteristic of rigid CTEV, whereas flexible CTEV shows a TMA closer to normal (< 20°) or that improves significantly with passive dorsiflexion and eversion. ### Radiographic Angles in CTEV | Angle | Normal | Flexible CTEV | Rigid CTEV | | --- | --- | --- | --- | | **Talus-1st MT angle (AP)** | 0–15° | 15–25° | > 30° | | **Calcaneal pitch (lateral)** | 20–30° | 10–20° | < 10° | | **Tibiocalcaneal angle (lateral)** | 80–90° | 50–70° | < 50° | | **Navicular position** | Lateral to talus | Slightly medial | Severely medial | ### Clinical Correlation **Clinical Pearl:** Flexible CTEV often corrects passively or with gentle stretching, and radiographs taken during dorsiflexion and eversion show improvement in the TMA and other angles. Rigid CTEV shows persistent deformity on stress views, indicating structural osseous or ligamentous constraints. ### High-Yield Concept **High-Yield:** The TMA is the **primary screening angle** on AP radiographs; a persistently elevated TMA (> 30°) despite Ponseti casting suggests rigid CTEV and may warrant earlier surgical intervention (e.g., posteromedial release). ### Mnemonic **Mnemonic: RIGID-TMA** — Rigid CTEV = TMA > 30°, Inflexible on stress views, Gross forefoot adduction, Imaging shows persistent deformity, Demands earlier surgical consideration. [cite:Tuli's Tuberculosis of the Skeletal System & Orthopedic Surgery 5e Ch 18; Campbell's Operative Orthopaedics 13e Ch 32]
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