Distraction index and Norberg angle to distinguish dysplastic and non-dysplastic hips based on FCI score

Abstract

Objective Radiographic hip scoring according to the Fédération Cynologique Internationale (FCI) and PennHIP (Pennsylvania Hip Improvement Program) method was performed with the purpose to compare the PennHIP and FCI results as well as coxofemoral joint laxity by correlation of Norberg angle and distraction index measurements.

Materials and methods A total of 167 dogs of various breeds presented for official screening examination in a veterinary teaching hospital in Germany were included. Using receiver operating characteristic analysis, the best Norberg angle and distraction index cut-off values to distinguish between dysplastic and non-dysplastic groups based on FCI grades and to distinguish between lax and tight hip joints according to the PennHIP proposal were calculated.

Results More than one third (38.2 %) of dogs that passed the breeding criterions according to FCI (grades A and B) were in the half of the population with lax hip joints and should not be used for breeding according to the PennHIP proposal. A cut-off value for the distraction index of 0.44 with sensitivity of 82.7 % and specificity of 84.2 % was superior to the best cut-off value for the Norberg angle at 101.8° with sensitivity of 82.7 % and specificity of 71.9 % to discriminate between non-dysplastic joints (A, B) and dysplastic joints (C, D, E).

Conclusions and clinical relevance Our results show a limited impact of laxity on the FCI grading. Breeding selection processes that are based on the FCI method could profit by an additional and complementary use of the distraction index.

Zusammenfassung

Gegenstand und Ziel Ziel der Studie war, die Ergebnisse der Röntgenuntersuchung auf Hüftgelenkdysplasie gemäß Fédération Cynologique Internationale (FCI) und PennHIP-Methode (Pennsylvania Hip Improvement Program) sowie den Einfluss der Hüftgelenklaxizität durch Korrelation von Norberg-Winkel und Distraktionsindex zu vergleichen.

Material and Methoden Die Untersuchung umfasste 167 Hunde verschiedener Rassen, die zur offiziellen Zuchtuntersuchung an einer Universitätstierklinik in Deutschland vorgestellt wurden. Mittels ROC-Analyse wurden Grenzwerte für Norberg-Winkel und Distraktionsindex zur Unterscheidung zwischen dysplastischen und nicht dysplastischen Hüftgelenken basierend auf den Ergebnissen der FCI-Methode sowie zur Unterscheidung zwischen lockeren und straffen Hüftgelenken gemäß den PennHIP-Empfehlungen berechnet.

Ergebnisse Mehr als ein Drittel (38,2 %) der Hunde, die die Zuchtkriterien nach FCI (Grad A und B) erfüllten, gehörten zur Hälfte der Population mit lockeren Hüftgelenken und sollten gemäß PennHIP-Empfehlungen nicht zur Zucht eingesetzt werden. Der Grenzwert von 0,44 für den Distraktionsindex war mit einer Sensitivität von 82,7 % und einer Spezifität von 84,21 % dem Grenzwert von 101,8° für den Norberg-Winkel mit einer Sensitivität von 82,7 % und einer Spezifität von 71,9 % zur Unterscheidung zwischen nicht dysplastischen Gelenken (A, B) und dysplastischen Gelenken (C, D, E) nach FCI überlegen.

Schlussfolgerungen und klinische Relevanz Unsere Ergebnisse zeigen einen limitierten Einfluss der Gelenklaxizität auf die Bewertung nach FCI. Zuchtauswahlverfahren, die auf der FCI-Methode basieren, könnten durch eine ergänzende Nutzung des Distraktionsindex profitieren.

Key words

Dog - hip dysplasia - radiography - PennHIP - Fédération Cynologique Internationale

Schlüsselwörter

Hund - Hüftgelenksdyplasie - Röntgen - PennHIP - Fédération Cynologique Internationale

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