234 Surgical Treatment
(A) (B) (C)(D) (E) (F)Figure 28.6 (A) Preoperative lateral radiograph of the stifle joint in full but not forced extension. Different breeds of
dogs will have differing full extension joint angles. (B) The circles outline the femoral condyle and the tibial plateau,
respectively; a line (#1) is drawn between the centers of these two circles; a second line (#2) drawn perpendicular to #1
between the circles is the common tangent of the joint surfaces; finally, a third line (#3) parallel to line #1 is drawn that
passes through the cranial-most origin of the patella tendon at the distal pole. This is the planned tuberosity position in
order to obtain a patellar tendon angle of 90◦. Note that the distance to move the most proximal point of the tibial
tuberosity to line #3 is NOT equivalent to the cage width (blue arrowheads, and also see panel D). A straight or distally
curved osteotomy can be planned for the tibial tuberosity (dotted lines). In this case, a curved line is selected to provide
more craniocaudal width due to the concave shape of the cranial border of the tibial crest (see panel C). (C) The outline
(red) of the tibial tuberosity is selected to match the planned osteotomy from panel B; note the length of the patellar
tendon (the orange line between the two orange arrowheads). (D) The tibial tuberosity is moved cranially so that the
proximal point of the tibial tuberosity intersects with the line #3, indicating the appropriate advancement distance. Note
that the position of the patella is unchanged (orange line between the two orange arrowheads). Therefore, the distal end
of the osteotomized tuberosity must move proximally (yellow arrows). The appropriate cage template is selected that