A prosthesis including a subacromial spacer having a surface contoured to maintain an acromion in chosen distance to a humeral head upon rotation and fixation means to fixate the subacromial spacer to a humeral medullary cavity and/or an intramedullary fixator implanted or configured for implantation in the humeral medullary cavity. A surgical kit includes the prosthesis and a proximal humeral nail. The fixating means are connectable into a proximal opening of the proximal humeral nail. A method may include: creating a percutaneous passage from an outer-body space to a portion of a humeral head removing bony tissue to facilitate direct communication between the outer-body space and a humeral medullary cavity enclosed in the humeral head providing a prosthesis including a subacromial spacer having a surface and/or fixating the subacromial spacer to the humeral medullary cavity and/or an intramedullary fixator implanted or configured for implantation in the humeral medullary cavity.
