Kathy:
I want to thank you for your extensive review of
the literature on hip assessment. It was quite lucid
and extremely helpful. Is the Norberg technique
utilized in this country?
Roger B Baskin
--- Kathy Yonkers <[EMAIL PROTECTED]> wrote:
> Roger...I know you like research so I thought I
> would share the following
> overview of the literature.
>
> I have been the process of evaluating the "widely
> used" systems that are
> available for the breeder. I have reviewed websites
> and their related
> publications and came up that it is inclusive which
> is the superior
> predictor, at this point in time. I have found that
> there are the clinical
> examination (which only demonstrated overt CHD/DJD
> changes). the subjective
> system (OFA) and two objective systems (Norberg
> angle and Penn Hip).
> Interesting that the Norberg angle which is widely
> used in Europe/OZ does
> not correlate to the findings or predictors of OFA.
> The Penn Hip system is
> unique due to its incorporation of a positioning
> device (like the Norberg
> Angle does) and a qualitative evaluation like OFA
> (CHD/DJD qualitative
> reading is taken from the standard hip extended
> view). This encourages
> "congruent validity" in its findings.
>
> Roger. ..with this great variation of these
> systems...it is difficult to
> obtain a true incidence of the disease. If cost is
> not an issue, a breeder
> may be best served by having both systems of
> evaluation performed. So in
> other words, it is too early to predict which system
> will truly have an
> impact on the incidence of disease (especially since
> we do not know what
> that true incidence is)...
>
> The following is "food for thought" only...This is
> an overall of these
> systems by various researchers and specialists. It
> is up to each breeder to
> decide what system they are comfortable with...
>
> Regards,
> Kathy Yonkers
> Stuarthome CKCS
> USA
>
>
> Definitions:
> Canine Hip Dysplasia (CHD)- abnormal structures of
> the hip and surrounding
> area.
> Degenerative Joint Disease (DJD)- presentation of
> osteoarthritis
>
> Clinical Presentation of CHD: 5 months to 12 months
> for the severe form of
> hip dysplasia; later for the chronic form (must have
> DJD changes to
> demonstrate this level of symptoms)
> * Abnormal Gait
> * "Bunny-hopping" When Running
> * Thigh Muscle Atrophy (loss of muscle mass)
> * Pain (difficult to measure)
> * Low Exercise Tolerance
> * Reluctance to Climb Stairs
> * Audible "click" When Walking or during manual
> manipulation of the hips
> * Increased Intertrochanteric Width ("points of
> hips" are wider than normal)
>
> These clinical signs can mimic other
> conditions...and it would only
> demonstrate frank CHD when DJD becomes problematic
> (severe form).
>
> The breeder will need radiographic film and/or
> series to determine the level
> of hip joint laxity and/or appearance of DJD in
> their dogs...while
> remembering radiographs will only demonstrate
> historical issues (hard tissue
> changes), not current or active disease. You will
> need an orthopedist
> specialist to perform a clinical examination and
> correlate this to the
> radiographic examination. Past history of injuries
> need to be
> addressed...injuries do impact on developing DJD,
> even in absent of familial
> traits. Also environmental factors (as reviewed in
> the literature) needs to
> be figured in such as: diet, history of trauma,
> level of exercise, and rate
> of growth.
>
> So here is where the maize begins...you have one (1)
> subjective system and
> two (2) objective systems that are widely
> used...each has advantages and
> disadvantages and they cannot be used
> interchangeable (apples and oranges):
>
> There are three (3) methods for diagnosis and
> prediction of predisposition
> to CHD/DJD in canines:
>
> 1) hip extension radiograph method (OFA),
> 2) stress radiographic diagnostic method (Norberg
> angle). and
> 3) combination (Penn Hip).
>
> These methods are categorized based on the
> positioning of the dog while the
> radiograph is taken. The first method (OFA) is the
> most common method in
> which the dog, while lying on its back, has its rear
> legs fully extended
> with the knees rotated inward. The second method
> (Norberg angle) requires
> that the dog be anesthetized and while lying on its
> back, the dog has its
> legs positioned as they would be if the dog were
> standing. A custom-designed
> device is placed between the legs which forces them
> apart, thereby
> displacing the ball of the femur from the hip socket
> and allowing for
> observation of joint laxity. The third method (Penn
> Hip) combines both
> positioning methods in a modified fashion (see
> below).
>
> Subjective Type:
> I. The OFA method
> http://www.offa.org
>
> OFA have a schematic scoring system of phenotypes
> that each radiologists
> draw their independent decision on while viewing one
> standard hip extension
> radiograph using a 7-point scale. This method is a
> qualitative (looks at
> quality...examiners may have a different subjective
> evaluation of the same
> radiograph) method because no form of measurement is
> utilized. Instead this
> method is based on subjective visual criteria such
> as degree of joint laxity
> (subluxation) and the presence of degenerative joint
> disease (DJD).
>
> Problems with this systems...intra-rator (score made
> by same examiner on
> same radiographs submitted under different
> conditions) grading can vary; No
> standardized positioning device is used to prevent
> artifacts. No computer
> assisted software is used to grade the radiographs
> or check for incorrect
> positioning variation. No specific training beyond
> entry level training is
> required of the veterinarian to have them
> �certified� in this performing OFA
> radiographic positioning. Vet schools vary in level
> of instruction of the
> technique, thus level of competency can vary between
> clinicians. Inter-rator
> reliability (the scores between different examiners)
> of the three rators is
> reported at 73.5% level calibration, which is below
> average for clinical
> research purposes, thus indicating subjectivity. If
> radiographs are
> resubmitted for a future re-evaluation...a prior ID
> # is required for the
> case. this identification could create bias in the
> rator(s) and thus
> influence the sensitivity/specificity (false
> positives and false negatives)
> levels to stay within an acceptable range.
>
> This schematic grading might give the breeder the
> feeling that they do not
> have to be concern if the grading is good or better
> when there is subjective
> variation within the system. The breeder might use
> it to market their dogs,
> and thus create a false sense of security to the
> consumer. Example...Is your
> good truly a good...etc??? Not all films taken are
> send in to the data bank
> by clinicians...so they are unable to measure true
> success of system over
> given time without question of bias.
>
> The true advantage is the low level of cost to
> breeder;
=== message truncated ===
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