Motion preserving C1 ring lateral mass screw fixation with transverse rod for isolated unstable Jefferson fracture of atlas vertebra: a multicentric study. - Beucler N; Choucha A; Farah K; Meyer M; Dagain A; Fuentes S (European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2026)