Effects of Single‐Foot Centered and Double‐Foot Centered X‐ray Projection on Hallux Valgus Measurement

OBJECTIVE: To investigate whether use of single‐foot centered and double‐foot centered weight‐bearing X‐rays has an impact on the relevant indicators of hallux valgus. METHODS: A total of 55 female patients from the Department of Ankle Surgery of Beijing Tongren Hospital with hallux valgus (110 feet) were collected from September to December 2015. The age of these patients ranged from 18 to 43 years, with an average age of 47.9 ± 8.5 years. All selected patients fit the diagnostic criteria of hallux valgus and had weight‐bearing single foot centered and double foot centered radiographs taken. During the projection, all patients were instructed to stand on the X‐ray box, with the knee joint straightened and legs perpendicular to the floor. The projection center of the single foot was directed at the lateral part of the scaphoid bone of the foot, while the projection center was directed at the position between the scaphoid bones of both feet for the double‐foot shooting. The hallux valgus angle (HAV), the intermetatarsal angle between the first and second metatarsals (IMA), the intermetatarsal angle between the first and fifth metatarsals (IM1‐5), and the metatarsal adduction angle (MAA) were measured and examined. The difference between these two shooting conditions was compared and analyzed. RESULTS: The differences in X‐ray measurement results (IMA, HAV, IM1‐5, and MMA) between different measures for the same patient were not statistically significant. The values of HAV, IMA, IM1‐5, and MAA are common indexes for evaluating hallux valgus. The average IMA was 15.9° for single‐foot centered and 14.1° for double‐foot centered X‐rays. The average HAV was 30.2° for single‐foot centered and 29.7° for double‐foot centered X‐rays. The average IM1‐5 was 31.1° for single‐foot centered and 29.7° for double‐foot centered X‐rays. The average of metatarsal adduction angle was 13.8° for single‐foot centered and 14.1° for double‐foot centered X‐rays. The differences between single‐foot centered and double‐foot centered X‐rays were statistically significant in terms of the measurement index (P < 0.05). In addition, compared with double‐foot centered weight‐bearing X‐rays, the focus of single‐foot centered X‐rays was located on the lateral part of the scaphoid bone of the foot, and the ray was closer to the vertical foot in the single‐foot centered weight‐bearing X‐ray. CONCLUSION: When the weight‐bearing position and projection distance are the same, the single‐foot centered weight‐bearing X‐ray is more effective in evaluating the severity of hallux valgus compared with the double‐foot centered weight‐bearing X‐ray.