Hip DysplasiaDiagnosis and Classification SchemesErica Fields, DVM
Cause(s) of Hip DysplasiaMultifactorialHeritable disorder Nutritional factors (overnutrition)Early exercise types/amountsEven season of birth has been shown to affect expression
Thrall, Textbook of Vet Rad and Ohlerth, et al. 2000.
Not Just DogsYes, we usually associate hip dysplasia with large, working-breed dogs, BUTCats and small or toy breed dogs can also be affectedIncidence in DSH estimated at 6.6%, Maine Coons up to 21%Some large breed dogs more susceptible than others (GSD vs. Greyhound)
Thrall. 4th ed Textbook of Vet Rad. 2002.
Signs of Hip DysplasiaPhysical examinationWalking Ortolanihands on trochanters during normal walkpalpate for laxityOrtolani signdorsal recumbency, abduct hips, feel for clunk Young dogsBardens Hip Liftlateral recumbency, anesthetized, lift hip laterally. Greater than 5-6 mm movement=positiveGait abnormalities (swing/bunny hop)
WSAVA Congress Proceedings 2002 and 2005
Signs of Hip Dysplasia (contd)Radiographic signsJoint laxity (distraction index, subluxation)Osteoarthritic changesEnthesophytosis at insertion of joint capsule on caudal aspect of femoral neck (Morgan line)OsteophytesFemoral head/neck remodelingAcetabular remodelingSubchondral sclerosis of femoral head/acetabulum
Thrall, 4th ed. Textbook of Vet Rad
What about cats?Coxofemoral subluxationMost degenerative changes appear on the craniodorsal acetabulum, not the femoral head and neck
Thrall 4th ed Textbook of Vet Rad
Radiographic Detection of Hip DysplasiaMANY methodseach has its advantagesOFA viewextended hip VDDAR viewbetter visualization of acetabular rim bluntingUltrasonographic evaluationPennHIP distraction methodEuropean (Federation Cynologique International)five point quality scale numerical system based on 6 factorsBritish (BVA) systemGerman system
OFA ClassificationsExtended hip VD pelvis viewConsensus of 3 boarded radiologistsBased on evaluation of 9 anatomic areas (craniolateral acetabular rim, cranial acetabular margin, femoral head, fovea capitis, acetabular notch, caudal acetabular rim, dorsal acetabular margin, femoral head/neck junction, trochlear fossa)
OFA guidelines (contd)Radiographs must be performed after 24 mos of agebased on a study showing that only 16% of dysplastic GSDs were diagnosed at 6 mos, as compared to 95% at 24 mosSix classes1 through 6 (excellent, good, fair, borderline, mild, moderate, severe)
Ohlerth, et al. J Sm An Pract 2003.
Pros and ConsOFA ProEasy to perform, no special tools or certifications neededGood identification of osteoarthritic changesLarge centralized databaseWell-recognized and established in the breeding communityCompares dogs within breeds
Pros and ConsOFA ConsExtended hip view may artificially tighten joint Not a physiologic positionSelection bias (really bad ones dont get submitted)Final eval cant be done before 24 monthsdelays breeding timesLittle eval of laxity
DAR viewCan supplement other views to better evaluate changes in dorsal acetabular rimUsed in planning for TPO proceduresBlunting of DAR caused by microfractures due to altered load bearing
WSAVA World Congress 2002
Ultrasound evaluationAccepted method in infantsIn development in dogsDone with a distraction device in place, longitudinal view in inguinal regiondynamic studyDifficult to perform accurately, variation may alter measurementsOnly appears to be reliable in predicting true negatives
Ohlerth et al. J Sm An Pract. 2003
PennHIPThree viewsstandard OFA view, compression view with legs bent at 90 degrees, distraction view with legs bent at 90 degreesAll radiographs are submitted to central databaseDistraction index calculated based on hip geometryDistraction indices correlated to likelihood of OA development for various breeds
PennHIPPros and ConsProsCan be performed as early as 4-5 mos, resulting in better breeder screeningAnatomic positioningmore functional evaluation and less artificial joint tighteningLess selection biasEvaluates laxity, an early cause/indicator of CHD
Thrall 4th ed Textbook of Vet Rad
PennHIPPros and ConsConsSpecialized device and training necessaryMust submit all radiographs
To get around these disadvantages, some people have tried to develop other techniques, including using wooden distractors or performing Ortolani and calculating subluxation
Thrall 4th ed and Ohlerth, et al 2003
Federation Cynologique Internationale System (FCI)Uses 6 criteria that are scored 0-5 (0 good, 5 bad)Norberg angle (more on this later)Coverage of femoral head by acetabular rimCraniodorsal acetabular rim conformation/osteophytosisSubchondral bone sclerosis Femoral head/neck shape and osteophytosisJoint capsule insertion enthesophytosis
Ohlerth et al. AJVR 2001
British Veterinary Association12 mos minimum age; no maximumNo resubmissions (unlike OFA, where prelim eval is allowed)VD extended hip (OFA) viewNine criteria evaluated and scored 0-6 PER HIP. Scores for hips are added for a total scorebest score is 0/worst is 53 for each hip, or 106 total score.Breed mean scores are published
www.bva.co.uk/public
BVA CriteriaNorberg angleSubluxationCranial acetabular edgeDorsal acetabular edgeCranial effective acetabular rimAcetabular fossaCaudal acetabular edgeFemoral head/neck osteophytosisFemoral head remodeling
www.bva.co.uk/public
Comparison of Different Scoring Systems OFA FCI (Euro) BVA (Aust/UK) SV (Ger)
E A-1 0-4 (no >3/hip) NormalGA-2 5-10 (no >6/hip) NormalF B-1 11-18 NormalB B-2 19-25 Fast NormM C 26-35 Noch ZugelassenMod D 36-50 MittlereS E 51-106 Schwere
www.offa.org
Norberg AngleUsed in many evaluation strategiesEvaluation of cranial acetabular morphology and subluxationA line is drawn between center points of both femoral heads and lines drawn from each femoral head center to the craniolateral aspect of DARAngle is calculated between 2 lines
Tomlinson et al AJVR 2000
Norberg AngleTraditionally, Norberg angle of greater than 105 degrees and acetabular coverage of greater than 50% is considered normalA study of 4 most common breeds in OFA registry compared NA, coverage, and OFA classificationThe 105/50 rule does not hold constant across breeds. Norberg angles from 92.6 (Goldens) to 101.9 (Rotties) are correlated with normal OFA
Tomlinson et al. AJVR 2000
ReferencesAllan G.: Radiographic signs of joint disease. In Thrall, D (ed): Textbook of Veterinary Radiology, 4th ed. Philadelphia. WB Saunders Co, 2002. pp 190-195. Ohlerth S, Busato A, Rauch M, Weber U, Lang J. Comparison of three distraction methods and conventional radiography for early diagnosis of canine hip dysplasia. Journal of Small Animal Practice. 2003 44:524-529. Ohlerth S, Lang J, Busato A, Gaillard C. Estimation of genetic population variables for six radiographic criteria of hip dysplasia in a colony of Labrador Retrievers. AJVR 2001 62(6): 846-852.Tomlinson JL, Johnson JC. Quantification of measurement of femoral head coverage and Norberg angle within and among four breeds of dogs. AJVR 2000 61(12): 1492-1500.www.bva.co.uk/publicwww.offa.org
