Perhaps a sharp end is protruding, or the geometry is all wrong. This is called a mal-union . In other cases, the two ends of the bone never get close enough to allow the bridge of fibrous tissue to form. This called a non-union . This involves an operation to expose the bone, clean it up, attach the plate or pin and sew up.
Reduction is the medical term for lining up the two ends of the bone.
By contrast, a Closed Reduction would be where the bone ends are manipulated without breaking the skin. Internal Fixation means that the plate or pin is fixed directly to the bone from within. A Closed Reduction is not generally much use because, without direct access to the bones, there is no way to fix the reduction in place. The effectiveness of a closed reduction depends entirely on how the bones are naturally aligned by the surrounding muscle. In theory clavicular rings are designed to create and maintain a closed reduction, but in practice they do seem any more effective than no treatment at all.