Intraoperative checking of the first ray rotation and sesamoid position through sonographic assistance

INTRODUCTION: Hallux valgus (HV) deformity affects the orientation of the metatarsophalangeal (MTP) joint in three planes. Displacement in the coronal plane results in axial rotation of the first metatarsal, with progressive subluxation of the first MTP joint. Multiple techniques have been described to correct the malrotation itself. However, none of them have checked intraoperatively the final position of the first metatarsal head and sesamoids previous to the fixation of the Lapidus procedure or first metatarsal bone osteotomies. The aim of this article is to describe a novel technique to check the first ray rotation and sesamoids position through sonographic assistance. MATERIALS AND METHODS: Before fixation of the Lapidus procedure, with the ankle in maximal dorsiflexion, the surgeon takes the linear ultrasound probe and places it on the sole to visualize the sesamoids, which should be viewed at the same level, with the flexor hallucis longus (FHL) centered between both. Once the ideal position of the head of the first ray has been achieved, temporary fixation with K-wires is performed over the first TMT joint and M1–M2 joint for further sonographic verification of the sesamoids beneath the first metatarsal head. The height of the sesamoids relative to the second metatarsal head should be checked by sonographic control too. RESULTS: Four patients were included. Three females and one male. Their mean age was 76.4 years (R 61–72). Their mean BMI was 29 (R 27.5–32.24). The mean IMA (intermetatarsal angle) was 18.2 (R 17.2–19) degrees and the mean MPA (metatarsophalangeal angle) was 50 (R 36–63) degrees. CONCLUSIONS: Sonographic assistance, is a widely available, inexpensive, and comparative imaging technique that can guide the first ray rotation and sesamoids position in HV surgery, theoretically improving radiological outcomes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00402-022-04359-8.