Restoring The Metatarsal Parabola With The Weil Osteotomy
To evaluate the metatarsal parabola, take a standard dorsoplantar projection in weightbearing on an orthoposer with a 15-degree projection angle. This view will allow you to do a standard evaluation of the foot bones, which should include measurement of the metatarsal protrusion distance. Remember, the second metatarsal should not exceed 2 mm respective to the first and third metatarsals at the phalangeal joint level. Davies and Saxby describe a simple postoperative measurement of metatarsal shortening that requires drawing a longitudinal bisection of the adjacent metatarsal and following it with two perpendicular lines that are tangent to the distal aspect of the bisected metatarsal and the second metatarsal.3 You can adapt this technique for preoperative evaluation of the metatarsal parabola.
A second view I find to be very informative is a dorsoplantar projection at 0 degrees with a lesion marker of soft wire taped to the area of callus. This will demonstrate the location of the callus at the corresponding MPJ for a stance phase lesion. Stance phase pathology results from an abnormal plantar declination or prominence of the affected metatarsal relative to the adjacent metatarsals. Excessive pressures induce nucleated hyperkeratotic lesions to develop.4 Propulsive phase lesions are often seen with MTPJ capsulitis and soreness at the end of the metatarsal. It is essential to use the 0-degree position with the wire marker since the 15-degree projection will artificially superimpose the wire marker in a more proximal location on the metatarsal. This will also help to determine if a callus is in a non-weightbearing area of the foot that will favor a nucleated porokeratosis or verruca as the pathology.
Evaluation in the sagittal plane using a sesamoid axial projection may be beneficial in borderline situations requiring elevation with shortening. This view has been debated with a questionable value to determine the relative declination of the metatarsal heads.5