Sometimes there is more than just one pathological reason for back pain and it seems in your case as well.
If your husband has uncorrected misalignments in his sacrum and spine then the resulting muscle tension will continue to stress his body and cause further pain.
You may try to re-align and relax the spine doing the exercises we recommend in the Dorn Method: http://www.dorn-method.com/index_files/SelfHelpExercises.htm
A gentle stretching of the Spine (not with a machine) is also helpful.
Blessings
Thomas