BACKGROUND:The displacement change parameters of the bone structure of the first metatarsal bone at the two-dimensional level of hallux valgus deformity are of great significance for clinical diagnosis and treatment,while the quantitative analysis of the three-dimensional deformity index may have some influences on the postoperative efficacy. OBJECTIVE:To explore the quantitative change of the three-dimensional deformity index of the first metatarsal bone after routine osteotomy and orthosis for hallux valgus deformity and to provide reference for clinical work. METHODS:100 patients with hallux valgus deformity(foot)in Hengshui People's Hospital from October 2020 to April 2023 were selected and all of them underwent conventional osteotomy and orthosis.Foot function was assessed by the American Orthopedic Foot and Ankle Society Ankle-Hindfoot Scale 6 months after surgery.Anterolateral X-rays of the foot in weight-bearing position and CT images in simulated weight-bearing position were taken before surgery and 6 months after surgery.The three-dimensional deformity indexes of the first metatarsal bone before and after surgery were quantitatively analyzed in patients with different ages,genders and therapeutic effects,including first-second intermetatarsal angle,hallux valgus angle,distal metatarsal articular angle,tibial sesamaid position,and first metatarsal rotation α angle.The value of the difference of three-dimensional deformity indexes of the first metatarsal bone before and after operation in evaluating the curative effect was analyzed. RESULTS AND CONCLUSION:(1)Six months after operation,the American Orthopedic Foot and Ankle Society score was 75-98(88.25±4.14)points,among which 56 cases were excellent,28 cases were good,14 cases were average,and 2 cases were poor.The excellent and good rate was 84%(84/100).(2)Compared with the preoperative results,first-second intermetatarsal angle,hallux valgus angle,distal metatarsal articular angle,tibial sesamaid position,and first metatarsal rotation α angle were significantly improved in patients of different ages and genders 6 months after surgery(P<0.05).First-second intermetatarsal angle,hallux valgus angle,distal metatarsal articular angle,tibial sesamaid position,and first metatarsal rotation α angle were all lower in patients with good curative effect 6 months after surgery than those with poor curative effect,and the difference before and after surgery was greater than those with poor curative effect(P<0.05).(3)The area under the curve of the difference evaluation of the first metatarsal three-dimensional deformity index before and after surgery was above 0.7,and the area under the curve of the combined evaluation of all indexes was the largest(0.902),which was significantly greater than the first metatarsal rotation α angle and distal metatarsal articular angle(P<0.05).(4)The quantitative analysis of the three-dimensional deformity index of the first metatarsal in patients with hallux valgus deformity is related to the postoperative effect,which has important guiding significance for improving the accuracy and comprehensiveness of preoperative evaluation and improving the treatment plan.