The reliability of angular measurements in hallux valgus deformities

The purpose of this study was to determine the intra-observer and inter-observer reliability of physicians on a repetitive basis in making angular measurements of hallux valgus deformities. The hallux valgus angle, the 1-2 intermetatarsal angle, and the distal metatarsal articular angle and the assessment of congruency/subluxation of the first MTP joint were evaluated on a repetitive basis. Physicians were provided with a series of black and white photographs of radiographs with a hallux valgus deformity. Three different sets of photographs randomly ordered were sent at a minimum interval of six weeks to the participants. Participating physicians were extremely reliable in the measurement of the 1-2 metatarsal angle. 96.7% of the photographs were repeatedly measured within a range of 5 degrees or less. The angular measurements to determine the hallux valgus angle were slightly less reliable, but 86.2% of photos were repeatedly measured within a range of 5 degrees or less. In the measurement of the distal metatarsal articular angle, 58.9% of photographs were repeatedly measured within a range of 5 degrees or less. There was a wide range within physician evaluators who recognized very few congruent joints (2 of 21) and those who recognized several congruent joints (11 of 21). Most physicians appeared to be internally consistent in the assessment of MTP congruency; however, some photographs were much more difficult to assess than others. This study validates the reliability of the measurement of the hallux valgus and the 1-2 metatarsal angle. The inter-observer reliability in the measurement of the distal metatarsal articular angle is questioned.