  The introduction of modified bond-defects in spin-Peierls systems is
investigated in a model of antiferromagnetic Heisenberg spin chains coupled to
adiabatic phonons. Generically, new low-energy magnetic or non-magnetic
excitations appear below the bulk spin gap energy. When two adjacent bonds are
modified, these excitations can be interpreted in terms of boundstates of a
soliton with the localized spin-1/2 located on the impurity site. It is shown
that the confining potential occurs even in the case of {\it isolated} chains.
