Correction of eTPA angle in a toy breed dog

(clinical case)

• 3 y old, male Yorkshire presented to us as the owner is not
pleased with his walk and limb posture of the left hind limb
• History of trauma during the growing period
• No radiographic images performed after the trauma
• Radiographic studies performed on both hind limbs
revealed significant difference of the TPA angle of the left stifle joint
• TPA right tibia – 28.9 degree
• TPA left tibia – over 59 degree
• Deformity of the proximal tibia, resulting in a caudally
sloping tibial plateau has been found to predispose dogs
to a cranial cruciate ligament rupture (Read and Robins
1982, Selmi and Padilha Filho 2001, Macias, McKee and
May 2002

• Fractures involving the both growth plates (the one of the TT and
the tibial plateau) are nor rare in young toy breed dogs. They tend
to occur in the later stage of the immature skeleton when the
connection between both epiphyses is more solid. The combined
distractive forces from the quadriceps mechanism and caudally
directed shear forces from the hock extensors result in a typical
Salter-Harris type 2 injury (fracture line through both physeal lines
and caudal metaphyseal spike fragment)
• Terriers are overrepresented with respect to the development of
TT avulsion fractures, either alone or in combination with proximal
tibial physeal separation (Pratt 2001)
• These fracture may not be appreciated sometimes as a displaced
fractures when are radiographed with stifle in extension (especially
on the presence of intact fibula)
• Flexed view is strongly recommended in order to be demonstrated
how unstable actually they are
• In contrast, isolated TT avulsion injuries seem more often in very
young individuals – 3-5 months of age

• The aim of the surgery was to correct the
excessive TPA angle to a relatively
physiological ranges (based on the opposite
limb), avoiding excessive tibia shortening
and hopefully preventing further
degeneration of the cranial cruciate ligament
• A modified cranial closing wedge was
planned. It is a juxta-articular neutral wedge
equal in angle of the planned correction
(Wallace 2011, Frederick 2016) where the
wedge is removing a half or not more than
the cranial 2/3 of the proximal tibia
• Orthogonal plate fixation was planed using a
medially applied pre contoured micro T-plate
and cranial Micro cuttable support plate

Surgical procedure

• After approaching to the proximal aspect of the
medial tibia, a K-wire was inserted in the
metaphysis to be perpendicular to the tibial axis.
This K-wire was used to orient the distal cut of the
wedge and to be able to navigate the position of
the proximal tibial segment after the correction (in
term of prevention of iatrogenic frontal plane
• The distal cut was executed based on the
preoperative planning and a saw blade left in situ as
a plane for orientation of the plane of the proximal
cut. Both saw blades should be on the same plane
and the removed wedge to be isosceles triangle
• A neutrally positioned wedge with a base of 7.4mm
was removed (corresponding to an approximately
40 degree of TPA correction)

• After removing the wedge, two holes were
drilled behind the cranial tibial cortex above and
below the ostectomy and hemicerclage wire was
applied but not tied
• The upper cut of the wedge was continued along
the caudal tibial cortex
• The hemicerclage wire was then tied, assisting in
apposition of both tibial segments and closing of
the wedge
• The medial micro T-plate was applied first using
1.7mm screws
• The Y-part of the micro cuttable support plate
was used after removal of one of the lateral ears.
The aim of the position of this plate was to be
applied as proximal as possible, orthogonal to
the T-plate but at the same time avoiding drilling
through the patella tendon. The plate was fixed
only with two 1.3mm mono-cortical screws

Postoperative assessment

• Alignment – reduction of the TPA to 19 degree
was achieved postoperatively. Slight proximal
tibial varus might be appreciated on the AP view
• Apposition – medial translation of the proximal
tibial segment was noticed on the AP view and
it was most likely due to the contour of the Tplate and the desire of the surgeon to have a
good contact between the implant and the bony
surface. Still visible osteotomy at the cranial
• Apparatus – well positioned implants without
invading the joint space. It was noticed that the
second distal medial plate screw was breaking
off a piece of the medial cortex

6 months follow up clinical and radiographic examination

• Clinically dog is doing very well without any
• Alignment, Apposition and Apparatus seem
• Activity – there is complete bone healing
and remodelling at the level of the
osteotomy on both ML and AP views