Hallux Pronation in Hallux Valgus: Experimental and Radiographic Study.

Toe pronation is a frequent sign in hallux valgus (HV), but it is difficult to assess and quantify. The aim of this study was to evaluate the relation between big toe pronation with both radiological and clinical findings and to determine if toe pronation is an influential factor in severity of HV. Six big toe donor proximal phalanges were used to create a radiographic calibrating system controlling their pronation at 0° to 60°. A linear regression model was used to predict proximal phalanx pronation in radiographs. Big toe pronation in HV was clinically evaluated with a prospective study using 132 patients from our surgical waiting list and a control group of 30 patients without HV. Patients standing barefoot on a rigid platform were used to obtain the nail-floor angle. We obtained the following angles: HV, intermetatarsal, interphalangeal, distal articular set angle, proximal articular set angle, first metatarsal pronation, proximal phalanx pronation, and sesamoid bones displacement. We obtained an equation to predict proximal phalanx pronation according to the proportion of the rotated phalanx (p < .001, r = 0.98), and used an intraclass reliability test to assess the intra-/interobserver reliability (p < .001, intraclass correlation [ICC] = 0.89/p < .001, ICC = 0.82). We found that the relation between HV severity and proximal phalanx pronation, nail-floor angle, and first metatarsal pronation was statistically significant (p < .0001, r = 0.64). Proximal phalanx pronation and nail-floor angle should be considered to classify the severity of HV. Using a mathematical formula, we can predict proximal phalanx pronation on radiographs. Clinical Level of Evidence.