TPLO
– tibial plateau levelling osteotomy
vs.
closing wedge osteotomy – CWO
Die
TPLO – Technik wurde 1993 von Slocum und Devine patentiert. Sie
ist in den USA sehr populär- wir ziehen die CWO – Technik
vor, erstens weil wir das Instrumentarium nicht von Slocum Nflg.
kaufen müssen und zweitens ist sie in allen chirurgisch
ausgerichteten Praxen oder Kliniken ohne Weiteres durchführbar:
Measuring
angles
Draw lines on a lateral radiograph of the tibia to
calculate the required angle of the wedge to bring the tibial plateau
slope back to 6 degrees.
The longitudinal line should run
from the intercondylar eminence of the tibia proximally to medial
malleolus distally.
The
distal cut of the wedge will be at right angles to this line and
positioned just at the point where the tibial crest begins to slope
down towards the shaft.
The angle of the plateau is
represented by a line drawn from the most cranial aspect of the
plateau to the most proximal point of the fibular head.
Deduct
6 degrees from the measured angle and this becomes the angle of the
wedge to be cut from the tibia. Draw this on the radiograph with the
apex level with the caudal border of the tibia.
Measure the
distance on the cranial edge of the tibial crest from the proximal to
distal lines ( usually about 10 – 12 mm).
Surgery
Free
drape the leg to be operated with the dog in dorsal recumbency. Then
allow the dog to roll to lateral recumbency with the side to be
operated on the table.
Make a parapatellar skin incision and
extend it distally along the cranial edge of the tibia for half to
2/3 its length. Avoid the medial saphenous vessels. Incise the medial
fascia of the leg and retract the caudal belly of the sartorius to
expose the medial collateral ligament.
Perform the caudomedial
arthrotomy and observe the caudal horn of the medial meniscus. If it
is fixed and not diseased, leave it alone. If freely mobile, remove
the caudal horn. Flush the joint and close it with 2/0 monofilament
absorbable suture material.
Free the cranial tibial muscle
from the bone in the region of the anterior tibial crest and pack
gauze sponges around the shaft.
With a sterile straight edge,
estimate the site for the perpendicular cut to the long axis and
measure proximally along the shaft the predetermined distance to
locate the proximal site for the wedge incision. Mark these sites
with an osteotome or bone rasp.
Bore two holes in the tibial
crest, one above and one below the wedge to enable an 18gauge hemi
cercelage wire to be placed once the wedge is removed.
Use
sterile towels or packs to ensure that the leg is parallel to the
table. Have an assistant hold the leg below the hock to maintain
correct alignment.
With an oscillating saw score the two
sites, the cut halfway through the distal mark, then halfway through
the proximal mark, and then complete the distal cut and finally the
proximal cut. Save the wedge bone in a blood soaked sponge.
Place
the hemi cercelage wire then approximate the cranial edges of the
tibial crest and tighten the wire. This stabilizes the bone,
neutralizes rotational forces and facilitates placing of an
appropriate sized plate with three holes in the proximal fragment and
four holes in the distal fragment.
I am currently using a
Veterinary instrumentation 3.5 broad “T” plate for the
purpose. It requires little moulding and together with the cercelage
wire is very strong.
Flush the wound then dry it and place the
cancellous bone harvested from the removed wedge in the step at the
caudal edge of the shaft of the tibia.
Close the wound in
layers, take a check radiograph the apply a soft support dressing for
3 to 5 days.
Advise the owner to strictly rest their dog for 4
weeks. Free exercise should not be permitted. Take follow-up
radiographs at 6 weeks to assess healing. It is expected that healing
should be complete in 10-12 weeks.
Expected outcome: 90%
excellent function.
Institut
für tierärztliche Fortbildung
Hamburg
www.Hamburger-Fortbildungstage.de
Dr.
Bruce Christie, Melbourne
Dr. Itamar Tsur, Jerusalem