Spinal fixation system capable of being mounted on a vertebra of the spine to attach auna rod (10), said vertebra a rear wall in the vicinity of which rod and sidewalls extiendedicha from protruding ribs and / or transverse processes, the system comprising a piece (12) capable of binding arranged in front of said rib and / or said apófisistransversa, and bondable to said rod (10) a flexible tie (42) of elongate shape capable of bonding together said junction piece and menosuna rib and / or a transverse process and means (36) adjustable locking integral with said connecting part and capable of maintaining InPlace mate fixed simultaneously said junction piece with respect to said rod and at least a portion dedicha ligation with respect to said connection piece in order to block dedicha relative displacement rod (10) and said vertebra in opposite directions relative to one another, with the sistemacaracterizado that: said piece (12) connecting two elements (14, 20) longitudinal the first ends (16,22 ) are joined together so that said two elements are pivotable relative to each other andthe central parts of two opposing faces can be supported respectively on both sides dedicha rod (10), said means (36) locking adjustable susceptible to force the segundosextremos (18, 24) of said longitudinal elements towards each other and hold them in fixed position relative to the other unocon such that said d os elements form a vise and enclose dichavarilla, whereby said connecting part is liable to remain in fixed position relative adicha rod.Sistema de fijación vertebral susceptible de montarse en una vértebra de la columna vertebral para unirla auna varilla (10), presentando dicha vértebra una pared posterior en la proximidad de la cual se extiendedicha varilla y paredes laterales desde las que sobresalen las costillas y/o las apófisis transversas,comprendiendo el sistema una pieza (12) de unión susceptible de disponerse enfrente de dicha costilla y/o de dicha apófisistransversa,
