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OFA指導手冊~如何使用健康資料庫與實行選擇性繁殖 <髖關節發育不全(4)> 

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OFA指導手冊~如何使用健康資料庫與實行選擇性繁殖 <髖關節發育不全(4)>

文章泡泡拔 » 2007-01-22, 23:29

轉載本系列文章請請註明出處:
犬髖關節狗友會(www.dogchd.net)泡泡拔 阮振維譯自www.offa.org

Radiographic assessment of the hip joint 髖關節的X光顯影評估


Modern breeds vary widely in body size, shape and pelvic conformation.
Because of these differences, OFA classifications are based on
comparisons among individuals of the same breed and age. Knowledge
of hip phenotype can be valuable for the breeder in selection against hip
dysplasia and in estimating the potential for an active working life. It
is assumed that radiographs submitted to OFA are generally screened
by the veterinarian and the more obvious cases of HD are probably
not submitted. Therefore, the actual frequency of HD in the general
population is not known, but has been approximated by Corley (1997)
and Rettenmaier (2002) to be higher than reported by OFA. However,
the main objective of the OFA is to identify phenotypically normal
animals as potential breeding candidates. Thus, the OFA reported breed
frequency of HD can be used as a benchmark for breeders to gauge their
breeding program’s relative position.


Historically, the diagnosis of HD has been determined by radiographic
examination of the hips according to the protocol established
by the American Veterinary Medical Association. In this standard hip
extended position (ventrodorsal view), the animal is placed on its back
with the pelvis symmetrical, both femurs extended and parallel, and
with the stifles (knees) rotated internally placing the patellas (knee caps)
on the midline. The radiograph should include the last two lumbar vertebra
and the stifl e joints. It is essential, particularly in marginal cases,
to obtain proper position and radiographic technique.


The radiographic criteria of subluxation, shallow acetabula, remodeling,
and/or secondary degenerative joint disease are well documented.
However, interpretation and application of these criteria differ between
breeds, age of evaluation and veterinarians.


Figure 1 provides the nomenclature of the hip structures that are evaluated
by the veterinary radiologist. The veterinary radiologist is concerned with
deviations in these structures from the breed normal, and with evidence of
subluxation and degenerative joint disease (also called arthritis, osteoarthritis,
or osteoarthrosis).

Multiple anatomic areas of the hip are evaluated (Fig. 1) including:

1. Craniolateral acetabular margin—Area where abnormal bone
spurs (osteophytes) develop as the dysplastic joint attempts to stabilize
the biomechanically unstable femoral head.


2. Cranial acetabular margin—Area visualized in conjunction with
the hip ball to assess the degree of congruity and confluence of the
hip joint.


3. Femoral head (hip ball) —Assessed to determine its fit into the
socket and degree of congruity with the cranial acetabular margin
forming the joint space.

4. Fovea capitus—Normal flattened area on ball for attachment of the
round ligament; can be mistaken for degenerative changes if there
is lack of familiarity or inexperience in interpretation of hip radiographs.


5. Acetabular notch—Area visualized to help assess depth of socket
or “degree of fit”.

6. Caudal acetabular rim—Area where bone spurs can form.

7. Dorsal acetabular margin—Area visualized to assess the depth of the
hip socket (acetabulum) and percent coverage of the femoral head.


8. Junction of femoral head and neck—Area visualized to assess Area visualized
to assess neck size, shape, and architecture of the femoral head/neck. The neck
of the hip ball is usually the earliest and most commonly affected area where
degenerative changes occur in a dysplastic joint. In the
dysplastic joint, new bone builds up at the site of attachment of the
joint capsule and muscular attachments. This is a result of abnormal
stress created by incongruent articulation of the ball with the
acetabulum during movement.


9. Trochanteric fossa—Area to assess for any microtrabecular bone
changes or new bone proliferation.




Radiographic assessment of the hip joint 髖關節的X光顯影評估

現今的犬貓品種在體型大小、外觀與骨盆結構上,存在著相當的差異。因為有這些差異
,所以OFA的分級是依據相同品種、相同年齡的動物之間所做的比較,而訂定出來的。髖關節的
表現型資訊,對於繁殖者來說是非常有價值的,他們可以利用這些資訊來實行繁殖篩選以對抗HD
,也可以審慎評估動物個體是否有潛能發展活躍的工作生涯。

OFA會假設動物的X光片在被送到OFA之前,已經由獸醫師做過約略的評估,因此大部分明顯看得
出患有HD的病例,也許不會再將X光送給OFA。所以,髖關節發育不全(HD)在一般族群中的確實
發生率是多少,並沒有辦法確實的被知道。不過Corley (1997)與Rettenmaier (2002)曾經做過約
略的統計,得到的發生率是高於OFA所報告的。

儘管如此,OFA的主要目標是去定義出何謂正常的髖關節,並讓繁殖者能依這些標準找
出適合繁殖的候選動物。
因此,繁殖者可以視OFA所報告的HD發生率為一個基準點,用以調
整自己的繁殖機制。

在HD的診斷歷史上,髖關節診斷的標準程序是由美國獸醫醫學協會(A.V.M.A.)所建立的。在標準的髖
關節延展狀態下(VD view:腹背視角),動物必須背朝下躺著,骨盆保持對稱,兩條腿的股骨必須平行
伸展,同時伴隨著後膝向內旋轉,使膝蓋骨能夠置於中線上。X光片必須包含最後兩節腰椎和膝關節。
適當的延展位置和X光拍攝技術是必須的,尤其是遇到狀況不明顯的病例時。

在X光片的判讀上,髖關節的次鬆弛、太淺的髖臼、骨骼重塑與二次退化性關節炎
都已經有一定的準則來診斷,而且都已經被相當的證明其正確性。不過這些準則的解釋與應用,會隨著
不同的品種、檢查時的年齡與不同的獸醫,而有所不同。

圖1提供了髖關節各個結構的命名,獸醫放射顯影專家在作髖關節檢查時,將會針對這幾個地方作評估。
獸醫放射顯影專家注意的是,受檢查的動物在這些結構與同品種的正常動物有何差異,以及是否可看到
次鬆弛與退化性關節炎的證據。

圖1中的多個解剖區域將在檢查時被審慎評估,包含了:

1. Craniolateral acetabular margin(髖臼邊緣側蓋骨) — 當發育不全的髖關節,試圖要在生物力學機制上去穩定不穩定的股骨頭時,
會在此處生成骨刺。

2. Cranial acetabular margin(髖臼邊緣蓋骨) – 可以看見髖臼與股骨頭會在此處產生連結,針對此處進行評估可以得知髖關節的一致
性與契合度為何。

3. Femoral head(股骨頭or髖關節球) – 評估此處以確認球狀部位與窩狀部位是否適當地吻合,確認股骨頭與髖臼邊緣蓋骨之間的一致性
,並評估關節間的空間是否恰當。

4. Fovea capitus(股骨頭小窩) – 位於股骨頭球狀部位的正常平坦區域,是提供給圓形韌帶產生連結的地方;如果對於X光片的診斷解釋
不熟悉或缺乏經驗,有可能誤解此處是因為HD而產生的退化性變化。

5. Acetabular notch(髖臼凹口) – 顯影在X光上可幫助評髖臼的深度或“吻合程度”。

6. Caudal acetabular rim(髖臼尾緣) – 可能在此處生成骨刺。

7. Dorsal acetabular margin(髖臼背緣) – 可幫助評估髖臼的深度與股骨頭的包覆百分比。

8. Junction of femoral head and neck(股骨頭與股骨頸連接處) – 此處的顯影可幫助評估股骨頸的大小、形狀與股骨頸/頭的構造。
一個發育不全的髖關節,其最早也最常因受到影響而產生退化性變化的地方,就是髖關節球的頸部。

在發育不全的髖關節中,新的骨頭會在關節囊、肌肉與股骨產生連結的地方被建立起來,這是因為在
運動時,股骨頭與髖臼在接合上的不一致性,在此處產生了不正常的壓迫。

9. Trochanteric fossa(轉節窩) – 評估此處是否有任何微樑骨的變化或新骨增生。
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文章: 85
註冊時間: 2006-02-04, 18:01
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