Injections can be an excellent treatment option for certain spinal conditions.  They aim to place local anaesthetic and steroid around the area causing the pain to reduce inflammation in that area.  The effect of the steroid may well wear off over time but, if used for conditions such as slipped discs, the underlying condition may have resolved spontaneously by the time the steroid wears off.  It is a daycase procedure and is often done under local anaesthetic.