– 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:
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).
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.
für tierärztliche Fortbildung
Bruce Christie, Melbourne
Dr. Itamar Tsur, Jerusalem