Geometric features of proximal cllosing wedge osteotomy in the treatment of hallux valgus / 中国组织工程研究

ABSTRACT

BACKGROUND: With the wide application of the proximal closing wedge osteotomy in treatment of hallux valgus deformity, the metatarsal shortening and metatarsal elevation are constantly being mentioned. Scholars even think that the operation is complicated, the technical requirements are high, and the incidence of complications is high, and other osteotomy should be used instead. However, through literature research and clinical experience, it is found that the facts are not completely the case. OBJECTIVE: To perform geometric study of the plane and the physical model of the proximal closing wedge osteotomy so as to reasonably evaluate the effect of this technique on metatarsal shortening and metatarsal elevation. METHODS: The research was divided into four stages, in which the first three stages were plane geometric researches, with weight-bearing frontal image of the patient with hallux valgus as the research materials; the fourth one was solid geometric research, with plaster model of the first metatarsal bone as the research material. In research I (Stage I), the changes in 1/2 inter-metatarsal angle, length of the first metatarsal and distal metatarsal articular angle were learnt through angle adjustment after clipping when the distance from the wedge osteotomy vertex to medial border of the first tarsometatarsal joint was different (B, A, C, D respectively from the near to the distant, with a distance of 10 mm). In research II (Stage II), the changes in 1/2 inter-metatarsal angle, length of the first metatarsal and distal metatarsal articular angle were learnt through angle adjustment after clipping when the distance from the wedge osteotomy vertex to medial and lateral connection of the first tarsometatarsal joint was same, and the distance from the wedge osteotomy vertex to axis of the first metatarsal bone was different. In research III (Stage III), the changes in the above-mentioned research indexes were studied through angle adjustment after clipping when the wedge osteotomy vertex and wedge angle were fixed, but the proximal osteotomy line slope was different. Research IV (Stage IV) was the simulated osteotomy comparison, osteotomy perpendicular to metatarsal backbone or perpendicular to the horizontal plane was conducted on the model through plaster casting, and then osteotomy section was closed; the changes in elevation of the metatarsal head, 1/2 inter-metatarsal angle and length of the first metatarsal bone were measured. RESULTS AND CONCLUSION: (1) Results of plane geometry The closer the wedge osteotomy vertex was to the proximal end, the larger the correction gained was and the smaller the changes in the distal metatarsal articular angle were, but the shortening was more obvious. Moreover, the closer the wedge osteotomy vertex was to the axis of the metatarsal bone, the smaller the shortening was; if only the proximal osteotomy line was different, the indices were the same. (2) Results of stereoscopic geometry In the case of the same osteotomy angle, the cuneiform bone of the same angle was intercepted, and the degree of correction was obviously greater than that of the plane geometry. This should be related to the thickness of the osteotomy saw and the loss of bone mass caused by the osteotomy. The metatarsal bone was significantly higher after correction when perpendicular to the metatarsal stem compared with that perpendicular to the horizontal surface. In 1/2 inter-metatarsal angle, the difference between the two was only 1°. In metatarsal shortening, it was smaller when perpendicular to the metatarsal stem compared with that perpendicular to the horizontal surface. (3) In conclusion, a. the optimal wedge osteotomy vertex is not at the medial border of the joint but is 1 cm from the medial border of the joint; then, it will approach the axis of the metatarsal. In this way, good correction, steady fixation and further reduction of metatarsal shortening can be achieved. b. The optimal direction of the oscillating saw blade is perpendicular to horizontal plane; however, an approximately perpendicular position to the horizontal plane is acceptable. It does not affect the effect of orthopedics, and further reduces the metatarsal shortening. When the bony closure is closed, the distal end of the metatarsal bone is taken to avoid the elevation of the metatarsal bone with a 2 mm step with the proximal end. c. The angle selection of proximal osteotomy surface can be placed on the metatarsal stem according to the internal fixation condition, and it can also form an acute angle with the metatarsal stem, so that the effect of osteotomy will not be changed.