Radiographic validation of the Manchester scale for the classification of hallux valgus deformity

Hallux valgus is a common orthopaedic condition affecting elderly people. Grading the severity of the condition commonly involves obtaining measurements from radiographs, which may not be feasible or necessary in some clinical or research settings. Recently, a non-invasive clinical assessment tool (the Manchester scale), consisting of four standardized photographs, has been developed; however, its validity has not yet been determined. Therefore, the objective of this study was to determine the validity of this tool by correlating Manchester scale scores with hallux valgus measurements obtained from radiographs.

Weight-bearing dorsoplantar foot radiographs were obtained from 95 subjects (31 men and 64 women) aged 62-94 yr (mean 78.6, s.d. 6.5), and measurements of the hallux abductus angle, intermetatarsal angle and hallux interphalangeal adbuctus angle were performed. These measurements were then correlated with the Manchester scale scores (none, mild, moderate or severe).

The Manchester scale score was highly correlated with hallux abductus angle (Spearman's rho = 0.73, P<0.01) and moderately associated with intermetatarsal angle (rho = 0.49, P<0.01) measurements obtained from radiographs. Analysis of variance revealed significant differences in mean hallux abductus angles [F3 = 119.99, P<0.001] and intermetatarsal angles [F3 =29.56, P<0.001] between the four Manchester scale categories.

These findings indicate that the Manchester scale provides a valid representation of the degree of hallux valgus deformity determined from radiographic measurement of hallux abductus angle and intermetatarsal angle. We therefore recommend the use of this instrument as a simple, non-invasive screening tool for clinical and research purposes.