A frontal plane metatarsal rotational (pronation) has been documented in a high percentage of hallux valgus patients. Pathoanatomical concepts leading to pronation are still debated. Nevertheless, there is no consensus on how to measure this component of the deformity. The aim of the present study was to compare three commonly used radiographic methods to measure the frontal plane deformity in hallux valgus deformity, such as 1. Round sign of the lateral edge of the first metatarsal head on anterior-posterior radiograph, 2. Non-weightbearing CT-scan and 3. Bernard's axial projection of the first metatarsal head. Afterwards, feet were dissected, and a direct measurement of the pronation was done. Our data showed that alpha angle measurements made through the Bernard's axial projection were closer with those obtained during the dissection compared to those made through the CT-scan. The main finding of our study is that osteoarthritic changes at the metatarso-sesamoid joint play an important role in severe hallux valgus cases. The proposed radiographic methods allow surgeons to verify whether rotation can be corrected during Hallux Valgus procedures and to determine which procedure may be the best for each patient.
Keywords: Bernard's axial projection; foot anatomy; frontal plane; hallux valgus; non-weightbearing CT; pronation.
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