It appears that the managers or HODs have grip on their juniors because leadership wanted a "command and control" management style of the erstwhile era. Fault might not be with HODs or managers per se but with leadership because it is leadership that has allowed to foster culture of this kind. Who knows leadership also could be keeping HODs or Managers in tight grip. Therefore, check this factor first.
Nevertheless, if you wish to change the culture check whether you have buy in from the management. If yes, then think of introducing culture of performance. When the performance targets are given, HODs or managers have to attain the performance targets with and through their subordinates and they need to loosen their grip.
For further details, we may have discussion on telephone.