A spinal fixation system comprising a bone screw, a body, and a pressure cap. The bone screw may comprise a head at a proximal end and a bone connection element at a distal end. The body may comprise a proximal end, a distal end, a mounting rod receiving channel at the proximal end and a bone screw head receiving channel at the distal end. A proximal end of the pressure cap may comprise two side walls disposed apart from each other and one biasing member on each side wall. A distal end of the pressure cap may comprise a surface operable to contact at least a portion of the head of the bone screw. The pressure cap may be operable to exert pressure on the bone screw when a mounting rod is biased against the proximal end of the pressure cap.
