A composition comprising: a first synthetic precursor possessing first functional groups and having a molecular weight of from 100 to 1500 Da, a second synthetic precursor comprising a multi-armed precursor possessing a core and from 3 to 12 arms, the arms each comprising a polyethylene glycol having a molecular weight from 250 to 3000 Da and possessing second functional groups at the ends thereof; wherein the first functional groups crosslink with the second functional groups thereby forming a biodegradable hydrogel which swells from -50% to 50%, for use in the treatment of tissue inside the vertebral column of a patient.