Proposition d'une nouvelle ostéotomie métatarsienne médiane: L'ostéotomie cervicale de raccourcissement axial (OCRA). Approche expérimentale comparative avec l'ostéotomie de Weil

The cervical shortening axial osteotomy, is a distal metatarsal osteotomy, preserving the joint, with a cylindrical piece of bone removed in the line of the metatarsal axis, and with the preservation of a stabilising bone block, on the head fragment. After a first mathematical and geometric analysis, this second experimental study on sawbones, was to compare Weil osteotomy, Weil osteotomy with resection of a bone slice on the proximal fragment, made after the proximal translation of the distal fragment, and the cervical shortening axial osteotomy. These were performed on 20 sawbones, divided into four groups: Weil osteotomies were performed in the first three groups: using a horizontal cut in group 1, a 10° oblique cut in group 2, and a 20° oblique cut in group 3; cervical shortening axial osteotomies were performed in group 4. In a second part, the Weil osteotomies were completed by bone slice resections on the proximal fragment. In each group, the head fragment was translated one centimeter proximally. The radiographic assessement used bony lanmarks to analyse morphological changes, and the projection of these landmarks on the horizontal line. The length, heigth, and declination angles variations were mesured. With an horizontal Weil osteotomy, we found no plantar displacement of the head, but an increased metatarsal declination angle, averaging 2.6°. In an oblique Weil osteotomy, head plantar displacement is associated with a greater metatarsal declination angle. For the 10° angle oblique oteotomy, the head's plantar displacement average 2.2 mm and the metatarsal declination angle 4.2° and for 20° angle oblique osteotomy, the head plantar displacement average 2.8 mm and the metatarsal declination angle 6.4°. The bone slice resection, made just after the proximal translation of the metatarsal head, in the Weil osteotomy, resulted in the correction of head plantar displacement and metatarsal angle modifications. For the 10° angle oblique Weil ostetomy, the head displacement is 1,8 mm dorsal, and the declination angle is reduce to 0.4°; and for an 20° oblique Weil osteotomy, the results are 2.2 mm for the head dorsal displacement, and 0.4° for the declination angle. In the shortening cervical axial osteotomy, the metatarsal head follow a dorsal displacement but also a plantar displacement secondary to the plantar bone block preserved on the distal fragment, resulting in a 1.2 mm dorsal position. The metatarsal declination angle is 1.6° greater

Proposition d'une nouvelle ostéotomie métatarsienne médiane: L'ostéotomie cervicale de raccourcissement axial (ORCA). Approche géométrique comparative avec l'ostéotomie de Weil

Lack of objective guidelines in surgical metatarsal osteotomies, justify this study's purpose that is to compare the Weil osteotomy, the Weil osteotomy with a slice of bone removed from the proximal fragment, and the axial osteotomy, through a mathematical geometric analysis. The cervical shortening axial osteotomy (CSAO) is an extraarticular axial osteotomy; its high stability is provided by retention of a plantar bone block on the distal fragment. In a right triangle, the hypotenuse is the metatarsal axis, one side is the horizontal plane, and the angle in between is the declination angle. For a 15° initial declination angle, and for 5 mm and 10 mm shortening, we calculate the length, heigth, and angle modifications. An horizontal Weil osteotomy cause a 1° to 2.5° change in plantar flexion. In an oblique Weil osteotomy the head's plantar displacement average 0.8 to 3.4 mm and the declination angle increase to 5.8°. The effects of a slice of bone removed from the proximal frgament in the Weil osteotomy are not the same if it was made before or after the head's proximal translation. Made before the head's translation, the resection of a slice of bone above the cephalic fragment, cause a plantar displacement, a plantar flexion of the metatarsal, and a great increase in the shortening effect. To be effective, it has to be done after the head's proximal translation. The advantages of the axial shortening osteotomy are the declination angle preservation, the dorsal head's displacement, from 1.5 to 3 mm. The vertical vector of a force "F" passing trouhg the metatarsal, is greater in a Weil osteotomy with plantar and proximal translation than in a theorical pure plantar translation osteotomy. The metatarsal plantar flexion angle increases the vertical vector force more than the head's plantar displacement