Case Study: Daisy
Distal Femoral Ostectomy
Deformity Assessment
Daisy the Husky mix had a standard case of medial patellar luxation in her right hindlimb. Along with a TPLO to treat her torn crucial ligament, she required a lateral closing wedge DFO to correct her varus deformity. We used CAD software to determine the aLDFA and anteversion angle correction.
Before
After
Before
After
Planned
Correction
We removed a small wedge from Daisy's femur about 32mm proximal to the distal end using 3D software. We then repositioned the two segments of her femur to correct her aLDFA. We rotated the proximal portion of the femur to correct the anteversion angle. We set the final position of the proximal and distal halves to ensure easy application of the DFO plate.
Reduction Guide Design
Daisy's CORA and corresponding cut location was very distal, and her femur had many osteophytes. These two factors required a minimal distal footprint for the reduction guide. We chose 2.0mm pins to optimize for both the size of the femur and the small reduction guide footprint. We added features to easily grab the reduction guide for sliding on and off the bone and inscriptions to indicate the client case number and intended guide orientation.
Ostectomy Guide Design
We designed this ostectomy guide to wrap around about 150 degrees of the bone and extend toward the intercondylar groove to ensure it would self locate. We included two cut surfaces to guide a 35mm blade during the incision. Finally, we added support structures and inscriptions on the guide.
Completed Prints
We printed two reduction guides and two osteotomy guides from biocompatible resin and one pre-op and one post-op bone model in a standard, non-biocompatible resin. We drilled out the holes in the guides to ensure appropriate clearance fits with the pins. The osteotomy guide fit the pre-op bone as anticipated, and the reduction guide could slide easily onto the post-op bone.
Surgical Outcome
The surgeon reported that Daisy's operation went smoothly, with the guides functioning exactly as intended in the surgical plan. Along with the standard TPLO to treat her cranial cruciate ligament tear, the DFO corrected her varus deformity. Daisy's post op radiographs can be seen to the left.