In this section, the usage of mating features for assembly of implants is declared.
These Attributes establish a Cartesian coordinate system relative to the Frame of Reference of the implant. When two implants are assembled using a pair of mating features, a rigid spatial registration can be established, that transforms one Frame of Reference so that the mating features align. The figure below gives a simple example in 2D how two implants (symbolized by two rectangles) are matched according to a mating feature pair. For each 2D and 3D template present, a set of coordinates is assigned to each Mating Feature Sequence Item.
It is recommended to give Mating Features that are somehow related, the same Mating Feature ID (0068,63F0) in different implant templates. This may help applications to switch between components while keeping connections to other components. The Example in Figure ZZ.1-2 shows that the first and the last hole in the plates get the same Mating Feature ID in each Template.
The Mating Features are organized in sets of alternative features: Only one feature of any set shall be used for assembly with other components in one plan. This enables the definition of variants for one kind of contact a component can make while ensuring consistent plans.
An example for Mating Feature Sets is shown in Figure ZZ.1-3. A hip stem template shows a set of five mating features, drawn as circles on the tip of its cone. Different head components use different mating points, depending on the base radius of the conic intake on the head.
For each Item of the Mating Feature Sequence (0068,63E0), degrees of freedom can be specified. A degree of freedom is defined by one axis, and can be either rotational or translational. For each 2D and 3D template present, the geometric specifications of the mating points can be provided.
Instances of the Implant Assembly Template IOD are utilized to define intended combinations of implant templates. An Implant Assembly Template consists of a sequence of component type definitions (Component Type Sequence (0076,0032)) that references Implant Template Instances and assigns roles to the referenced implants. In the example in Figure ZZ.1-4, the component types "Stems" and "Heads" are defined. Four different stems and two different heads are referenced. Both groups are flagged mandatory and exclusive, i.e., a valid assembly requires exactly one representative of each group.
The Component Assembly Sequence (0076,0060) declares possible connections between components referenced by the component groups. Each sequence item refers to exactly two implant templates that are part of at least one component group in the same Implant Assembly Template Instance. An Component Assembly Sequence Item references one mating feature in each of the templates according to which the assembly is geometrically constrained. The double-pointed dashed lines represent the Items of the Component Assembly Sequence in Figure ZZ.1-4.
