Geometric replacements for defective bone

In the repair of bone voids and deficiencies, rather than forming a planar, angled surface that could result in a “slip plane,” an implant features a defined geometric pattern such as a stair-step, which mates with a corresponding stair-step pattern formed on the bone. Screws or alternative fasteners extend through one or more of the stair-step patterns, and into the bone, such that local interface around each fastener is substantially transverse to the axis of the fastener, thereby achieving a set of effective, compression bond. As such, shear stresses that might be associated with an angled, planar fixation are converted to compressive forces, leading to a longer life and a reduced need for revision. Although in the preferred embodiment the plurality of surfaces defines a stair-step having right angles, other geometric patterns are applicable, so long as an irregular defect may be made more regular, and/or compressive forces are used to prevent shear stress. Cementation for may be used for fixation, and/or bone in-growth/on-growth. Although the invention is described in terms of the repair of a deficient acetabulum, the general idea is applicable to any region of the bone including, without limitation, glenoid repair, and tibial repair.