Tailor Made 3D Chevron Osteotomy on WBCT Measurements. Does the Dress Match its Design?

Research Type: Level 4 – Case series Introduction/Purpose: Objective: Three-dimensional correction of hallux valgus (HV) by first metatarsal osteotomy, including correction of pronation and translation of first metatarsal head, can be planned using preoperative weight bearing conebeam imaging (WBCT). The aim of our study was to compare preoperative planning with the surgical correction obtained in a continuous series of HV. Hypothesis: Planning the first metatarsal osteotomy in 3D allows precise osteotomy with reliable post-operative results. Methods: Fifty consecutive patients (44 women, 6 men, aged 14-80 years) with hallux valgus underwent a chevron osteotomy of the first metatarsal. Pre- and postoperative measurements at 4 months on WBCT included pronation of the head of the first metatarsal relative to the ground (MRA) and Metatarsal-Sesamoid Offset (MSO) to assess the amount of supination and lateral translation to be applied in the chevron osteotomy. The objectives were: (i) Hallux valgus angle (M1-P1) < 15°, (ii) M1-M2 intermetatarsal angle < 10°, (iii) Metatarsal Rotation Angle (MRA) =0° and Metatarso Sesamoidal Offset MSO=0mm. The sesamoid rotation angle (SRA), the metatarsal sesamoid rotation angle (MSRA) and the subluxation of the sesamoids according to Clapham and Hardy were also measured. Results: The mean preoperative and postoperative MRA was 8.5° (SD=8.8) and 0.9° (SD=7), respectively (p < 0,001) The mean preoperative MSO and mean postoperative MSO were 7.5mm (SD=2.5) and 1.7mm (SD=1.3) respectively (p < 0,001). The mean preoperative and postoperative M1-P1 angles were 32.0° (SD=8.5°) and 9.6° (SD=4.6) respectively (p < 0,001). The mean preoperative and postoperative M1-M2 angles were 15.4° (SD=2.9°) and 7.1° (SD=2.5) respectively (p < 0,001). The mean preoperative and postoperative Clapham and Hardy were 4,8 (SD=1,3) and 1,9 (SD=0,8) (p < 0,001) The mean difference between the programmed MRA and the MRA obtained was 0.9° (SD=7). The mean difference between the programmed MSO and the obtained MSO was 1.7 (SD=1.3) Conclusion: The results confirmed our initial hypothesis, i.e. the effectiveness of programming in achieving precise, three-dimensional correction of hallux valgus. The use of a dedicated ancillary could improve the osteotomy accuracy. Planning of first metatarsal pronation correction and sesamoid reduction on weight bearing CT slices.