[Minimally Invasive Hallux Valgus Surgery: First Experience].

PURPOSE OF THE STUDY The Minimally Invasive Chevron Akin (MICA) is a percutaneous technique used to correct hallux valgus deformity. The combination of distal osteotomy of the first metatarsal and the proximal phalanx of the big toe stabilized with internal fixation was used over the last decade. The retrospective study presents the results of measurements performed on preoperative and postoperative X-rays and offers a comparison with conventional osteotomies. MATERIAL AND METHODS The study population consists of 76 patients who underwent 93 operations between 2015 and 2018 at the Department of Orthopaedics, 1st Faculty of Medicine, Charles University in Prague. The mean age of patients was 50.2 years (range 18-74 years). The study evaluates and measures the parameters and the attributes of interest on weight-bearing X-rays of the foot before and after the operation at 6-week or 3-month follow-ups. The first intermetatarsal angle was measured according to the mechanical and the anatomic axis of the first metatarsal bone. Apart from that, the displacement of the first metatarsal head in the osteotomy, hallux valgus angle and distal metatarsal articular angle were analysed. The position of the medial sesamoid bone and the congruency of the first metatarsophalangeal joint were evaluated as well. RESULTS The mean hallux valgus angle was 33.2° ± 7.3° and 10.2° ± 5.8° postoperatively. The mean value of the first mechanical intermetatarsal angle decreased from 12.4° ± 2.8° to 7.4° ± 2.5° postoperatively. The mean value of the first anatomic intermetatarsal angle increased from 13.7° ± 3.6° to 17.4° ± 4.6°. The used technique restored the congruency of the first metatarsophalangeal joint in 85 cases (91%). The mean lateral displacement of the metatarsal head fragment was 50% of its width (range 18% to 84%). The mean X-ray exposure during the operation was 0.58 mGy and the personnel were exposed to radiation for 79 seconds on average. DISCUSSION One of many questions raised with regard to hallux valgus surgery is the choice of the right technique in order to achieve proper position of the big toe. The surgeon should have the opportunity to use a technique that provides the possibility to change orientation of the metatarsal head articular surface in three anatomic planes. Our study found out that the displacement of the metatarsal head using the MICA technique in transversal plane is from 4 mm to 18 mm (in 20 mm diameter of the head). The method thus offers a possibility to correct mild, moderate and partially severe deformities as well. The main disadvantage of the method is the necessity to use a C-arm at the operating theatre. CONCLUSIONS The Minimally Invasive Chevron Akin (MICA) is a percutaneous technique to correct hallux valgus deformity based on two extraarticular osteotomies of the proximal phalanx of the big toe and the distal part of the first metatarsal bone. The method using stable internal fixation with two screws offers a possibility to change the orientation of the articular surface of the metatarsal head in sagittal, transversal, and even in frontal plane, and is useful to correct mild and moderate deformities. Key words: hallux valgus, minimally invasive technique, percutaneous technique, chevron osteotomy, Akin osteotomy.