Use of a 3D laser scan technique to compare the surface geometry of the medial coronoid process in dogs affected with medial compartment disease with unaffected controls

Subchondral bone surface geometry of the medial coronoid process was examined in 20 grossly normal elbow joints of adult German Shepherd dogs (GSDs) and compared with results obtained from 10 joints of adult GSDs and 12 joints of adult Rottweilers affected with bilateral fragmentation of the medial coronoid process (FMCP). Additionally, seven dogs (4 GSDs and 3 Rottweilers) with unilateral FMCP were investigated. The subchondral contour of the ulnar trochlear notch was digitised to obtain the 3D coordinates of its surface points. Geometry was investigated in two defined section planes along the longitudinal and transverse axes of the medial coronoid process. The coordinates of the surface points in the section planes were normalised along one axis and geometry was estimated by the position of the surface points along its third coordinate and by calculation of the angle of inclination of the medial coronoid process.Subchondral bone surface geometry was not related to the type of fragmentation (i.e. single sagittal versus multiple sagittal or transverse fragmentation). No differences were noted when comparing joints of dogs affected unilaterally with FMCP and their contralateral normal joints. In addition, no differences in geometry were seen between GSDs affected with fragmentation and normal GSDs. The most evident differences were found between Rottweilers affected with FMCP and normal GSDs as well as FMCP affected GSDs. The results suggest that subchondral bone geometry (geometric incongruity) plays no role in the development of FMCP. Geometric differences between breeds were more prevalent than differences between normal joints and those affected with FMCP within one breed.