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 25-28 September, 2018 | Singapore
edge of the greater trochanter with the dorsal edge of the lesser trochanter.
A Hatt spoon curette is used to cut the round ligament and luxate the head. This is the best instrument by far for this part of the surgery as it combines leverage of the femoral head with a cutting tip. The Hatt spoon curette is relatively cheap and much better and easier to use than a “hip disarticulator”.
Cutting the round ligament requires careful force and
is made simpler if the surgical assistant is externally rotating the femoral head to tension the ligament as it is being cut. The curette is used like an ice cream scoop.
When the ligament is completely cut the leg will be able to be externally rotated (supinated) 90 degrees so that the stifle joint and hock joint are perpendicular to the table and the femoral head will “pop out” out of the acetabulum (move laterally).
If you have not completely cut the round ligament you will not be able to externally rotate the leg 90 degrees and the femoral head will remain partly tethered to or within the acetabulum.
The femur is externally rotated so that the stifle is at 90 degrees to normal. Continue to blunt and sharp dissect the joint capsule / vastus muscles so that you can palpate the lesser trochanter. Elevation on the medial aspect of the femur is important to achieve this and now the femur can be externally rotated 90 degrees this is much easier than before the ligament was cut. Keeping the scalpel blade inside the joint capsule and in contact with the bone as you elevate the medial capsular tissue prevents any iatrogenic damage.
Push a blunt elevator or other blunt instrument ventral to the gluteal tendon insertion on the greater trochanter to identify where the medial edge of the greater trochanter is. Make a mark on the bone at this point.
The lesser trochanter is on the caudal edge of the medial aspect of the femur and is the point of insertion of the iliopsoas muscle. Palpate either the lesser trochanter or the tubular insertion of the iliopsoas muscle on the trochanter so that you can make a mark on the cranial surface of the femur at the dorsal edge of the lesser trochanter. In some dogs you can visualize the tendon of insertion.
If you cant palpate either the tendon or the lesser trochanter it is probably because you have not elevated the medial capsular tissue far enough ventrally. Progress this elevation if necessary until you can confidently identify the lesser trochanter.
Mark a line on the cranial surface of the femur connecting the medial aspect of the greater trochanter with the dorsal aspect of the lesser trochanter. Ensure the capsule and vastus is reflected sufficiently to achieve
this.
Ensure your assistant is holding the femur at 90 degrees external rotation (supination). This is critical to achieving the correct plane of excision and limiting the amount of rasping you need to do after the excision.
The assistant can ensure the leg is externally rotated 90 degrees by using the stifle joint and hock joint
as “handles” and ensuring that they are both held perpendicular to the table / floor.
The assistant needs to focus on this while you complete the excision. The most common mistake is for the assistant to allow some internal rotation of the limb during the cut. This inevitably leads to insufficient neck being removed with an angular piece of bone remaining on the caudal aspect of the neck which then needs to be removed. It is your responsibility because they are working under your direction. J
A sagittal saw with a fine sharp blade is the best instrument to make the cut in the femoral neck. It has the advantage of accuracy, lack of propagation into fracture of the caudal part of the neck and it leaves a smooth surface. Provided the cut plane is correct there is no need to rasp an ostectomy made with a sagittal saw. A good sagittal saw is one of the best pieces of equipment to simplify this surgery.
The other alternative if a sagittal saw is not available is an osteotome. This is not as good as a sagittal saw as it creates a rougher cut necessitating rasping to a smooth surface. It also has the tendency to cause small fractures of the caudal surface of the femoral neck. This is less likely with a sharp osteotome that.
It is important to note the difference between an osteotome and a chisel. Chisels are not suitable
for bone surgery. Osteotomes have a symmetric or equilateral triangular tip and cut in the direction that the shaft is aimed. Chisels have an
asymmetric tip or right angle triangular tip and do not cut in the direction the shaft is aimed.
The importance of using a sharp osteotome of an appropriate size for the animal can’t be understated.
What about Gigli wire? This needs to be properly placed without entrapping caudal soft tissues and has the disadvantage that when it is placed under tension to make the cut it tends to migrate medially to the narrowest part of the neck which is usually the mid part of the neck. In doing so this leaves a significant part
of the femoral neck that is not removed. Insufficient or partial removal of the femoral neck is one of the main causes of postoperative morbidity and poor long-term function after excision arthroplasty.
Confirm that your assistant has the leg externally rotat- ed at 90 degrees – the stifle and hock joints should be
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43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS







































































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