Purpose: Constitutional factors responsible for hallux falgus and hallux rigidus remain unclear. The purpose of this work was to compare the radiological feature of the forefoot in three populations with “normal” feet, hallux rigidis, and hallux valgus.
Material and methods: One standard protocol was used within the same unit to obtain dorsoplantar AP views of the foot in the standing position in all subjects. Fifty “normal” feet, with no apparent deformation, callosity, or pain, were selected among the orthopaedic unit personnel; mean age of the 25 subjects was 30.3±9.6 years, and 44% were women. The 30 patients with hallux rigidus were operated on at a mean age of 57.4±10.7 years, and 48.4% were women. The 50 patients with hallux valgus were operated on at a mean age of 50.8±12.8 year and 92% were women.
All radiograms were digitalised (Vidar VXR-12 plus) and analysed by four observers using the FootLog software which provides semiautomatic measurements. The following parameters were recorded: distance between the lateral sesamoid and the second metatarsal (LS-M2), the M1P1 angle (for the diaphyseal and mechanical axes of M1), the diaphyseal and mechanical distal metatarsal articular angle (DMAA) of M1, Meschan’s angle (M1–M2–M5), the distance between a line perpendicular to the axis of the foot drawn through the centre of the lateral sesamoid and the centre of the head of M4 (MS4–M4) (a corrective factor was introduced for the MS4–M4 distance to account for the displacement of the lateral sesamoid in hallux valgus), the M1 index = d1-D2 (length of the head of M1/MS4 – length of the head of M2/MS4), maestro 1 = d2–d3, maestro 2 = d3–d4, maestro 3 = d4–d5. The measured parameters were recorded automatically on an Excel data sheet and statistical analysis was performed with SPSS 9.0.
Results and discussion: Intra- and inter-observer reproducibility of measurements and morphological classifications were excellent. The LS/M2 distance was comparable in the three populations, proving that the lateral sesamoid is relatively fixed compared with the M2 and enabling its use as reference for the MS4 line. The Meschan angle did not discriminate between the three populations, likewise for the mean M1/M2 index, the M1P1, M1M2, and DMAA angles which were different in the three populations; there were 2° to 3° variations for the mechanical or shaft axis. The morphotype analysis demonstrated objective evidence of morphological differences of the forefoot in the three populations. The hallux rigidus group showed a predominance of the index plus and plus-minus with long M23 lateral patterns, while the hallux valgus group exhibited a predominance of M4M5 hypoplasia.
Discussion: Morphotypic definition of the metatarsals is an interesting approach providing a measurable way of interpreting forefoot disorders and guide surgical correction. These results should be confirmed with measures in larger series, which can be accomplished with FootLog software. It would also be useful to combine radiological studies with baropodometric studies.
