Radiographic validation of a self-report instrument for hallux valgus

Hallux valgus (HV) is a common condition causing substantial morbidity. Radiographic assessment is the gold standard for grading severity but is not always feasible in clinical/research settings. HV line-drawings, consisting of five drawings for each foot depicting a sequential increase in HV angle of 15°, have been clinically validated for self-reporting severity. We aimed to undertake radiographic validation of this self-report instrument.

Adults aged ≥50 from four GP practices were sent a health survey. Responders self-reported HV severity for each foot using the line-drawing instrument. Those reporting foot pain in the last year had radiographs taken at a research clinic from which intermetatarsal, hallux abductus and hallux interphalangeal abductus angles were calculated. Ten feet were randomly selected for each HV line-drawing grade for both feet. Associations between self-reported HV line drawings and radiographic measurements were assessed using Spearman's ρ correlation coefficients, mean radiographic angle measurement (95% confidence interval) and one-way analysis of variance.

Increasing HV line-drawing grade was positively correlated with radiographic measurements for intermetatarsal and hallux abductus angles (Spearman's ρ = 0.602, p < 0.001; 0.821, p < 0.001, respectively). Hallux interphalangeal abductus angle showed an inverse correlation with increasing line-drawing grade (-0.204, p = 0.053). Differences in radiographic measures between HV line drawing grades were significant for intermetatarsal (F = 13.98, p < 0.001) hallux abductus (F = 38.90, p < 0.001) but not hallux interphalangeal abductus angle (F = 2.21, p = 0.075).

Grading HV severity by self-reported HV line-drawings provides a valid representation of deformity determined from radiographic measurements and is a useful screening/self-reporting tool.