Radiographic Validation of Self Reported Line Drawings for Hallux Valgus: A Valid Virtual Self Reporting Tool in General Practise?

Problem

Hallux valgus (HV) is a common condition in general practice. Clinical and radiographic assessment is the gold standard, however during the current COVID pandemic and as part of a general move to virtual consultations, this is not always possible. HV line-drawings, consisting of five drawings for each foot depicting a sequential increase in HV angle of 15 degrees, have been developed and clinically validated for self-reporting severity . We aimed to undertake radiographic validation of the self-report HV line-drawing instrument.

Approach

Adults aged ≥50 from four GP practices in North Staffordshire were sent a health survey. Responders self-reported HV by selecting the line-drawing that best represented the angulation of the great toe whilst standing. Those reporting foot pain in the last year were invited to attend a research clinic where foot radiographs were taken from which intermetatarsal, hallux abductus and hallux interphalangeal abductus angles were calculated. Ten feet were randomly selected for each HV line-drawing grade for left and right feet. Associations between self-reported HV line drawings and radiographic measurements were assessed using Spearman’s p correlation coefficients, mean radiographic angle measurement (95% Confidence Interval) and one-way analysis of variance (ANOVA).

Findings

Self-reported HV line drawing severity of 0, 15, 30, 45, and 60 degrees showed an associated radiographic hallux abductus angle mean and (95% CI) of 7.7 (8.8, 10.2), 12.6 (9.8, 15.8), 20.7 (16.9, 24.5), 28.4 (23.9, 32.9), 43.1 (33.2, 53). Differences in radiographic measures between the HV line drawing grades were significant for intermetatarsal angle (F= 13.98, p<0.001) and hallux abductus angle (F= 38.895, p<0.001) but not hallux interphalangeal abductus angle (F=2.205, p=0.075).

Increasing self-reported HV line-drawing grade was positively correlated with radiographic measurements for intermetatarsal angle and hallux abductus angle (Spearman’s Rho=0.602, p<0.000; 0.821, p<0.001 respectively). Hallux interphalangeal abductus angle showed an inverse correlation with increasing HV angle severity (-0.204, p=0.053).

Consequences

Self-report of HV severity by line-drawings provides a valid representation of the deformity determined from radiographic measurements, suggesting that line-drawings could be used for virtual self-report of HV to GPs to guide treatment and referral .