Quantifying the Stress in Stress Radiography to Determine Sufficient Laxity of the Coxofemoral Joint in Sedated Dogs

Abstract

Objective

It is well-established that hip joint laxity is the primary cause of degenerative changes in canine hip dysplasia, although some fundamental characteristics of stress radiography are still scarce, especially regarding the appropriate applied force. The objective of this study was to validate the recently published force–laxity relationship from a cadaver study and to determine the force necessary to measure a sufficient proportion of laxity present in coxofemoral joints in sedated dogs.

Study Design

Twenty-one dogs (10 Beagles and 11 Labrador Retrievers) underwent a radiographic protocol, including stress radiographs with increasing force, using the Vezzoni Modified Badertscher Distension-measuring Device. The Laxity Index (LI) and osteoarthritis (OA) were scored.

Results

The force–laxity curves and the maximal Laxity Index (LI_max) were not significantly influenced by OA, gender or side. Weight was significantly associated with LI_max and the force–laxity curves. Ninety per cent of hip joints achieved sufficient laxity at a force of 80.45 N, which is practically achievable and less than that in cadavers. Bias due to low LI_max in the Labrador Retriever group and the only presence of radiographic signs of mild OA in the Beagle group should be considered.

Conclusion

This study confirmed the relation between applied force and LI, the robustness of this stress radiography technique and the use of a minimum 80.45 N of measured force to reach sufficient LI. Future studies with inclusion criteria regarding a broad LI_max range and OA scores should be conducted.

Keywords

canine hip dysplasia - stress radiography - force-measuring device

Contributors' Statement

L.V., T.B., B.B. and J.S. designed the experiment. L.V. performed the experiments and the measurements. B.B. performed the statistical analysis. All authors discussed the results. L.V. wrote the manuscript with contributions of B.B., S.H., K.V., T.B. and J.S. All authors agreed to the final manuscript.

^‡ These authors contributed equally to this article.

Publication History

Received: 21 March 2025

Accepted: 19 August 2025

Article published online:
17 September 2025

• References

• 1 Henricson B, Norberg I, Olsson SE. On the etiology and pathogenesis of hip dysplasia: a comparative review. J Small Anim Pract 1966; 7 (11) 673-688
• 2 Vezzoni A, Dravelli G, Corbari A. et al. Early diagnosis of canine hip dysplasia. Eur J Companion Anim Pract 2005; 15: 173-184
• 3 Smith GK, Gregor TP, Rhodes WH, Biery DN. Coxofemoral joint laxity from distraction radiography and its contemporaneous and prospective correlation with laxity, subjective score, and evidence of degenerative joint disease from conventional hip-extended radiography in dogs. Am J Vet Res 1993; 54 (07) 1021-1042
• 4 Santana A, Alves-Pimenta S, Martins J, Colaço B, Ginja M. Imaging diagnosis of canine hip dysplasia with and without human exposure to ionizing radiation. Vet J 2021; 276: 105745
• 5 Broeckx BJG, Vezzoni A, Bogaerts E. et al. Comparison of three methods to quantify laxity in the canine hip joint. Vet Comp Orthop Traumatol 2018; 31 (01) 23-29
• 6 Bertal M, Vezzoni A, Houdellier B. et al. Intra- and inter-observer variability of measurements of the laxity index on stress radiographs performed with the Vezzoni-modified Badertscher hip distension device. Vet Comp Orthop Traumatol 2018; 31 (04) 246-251
• 7 Bertal M, De Rycke L, Vezzoni A, Polis I, Saunders JH, Broeckx BJG. Technical repeatability and reproducibility of the stress radiographs performed with the Vezzoni-modified Badertscher hip distension device. Vet Comp Orthop Traumatol 2019; 32 (01) 67-72
• 8 Bertal M, Vezzoni A, Van der Vekens E, Polis I, Saunders JH, Broeckx BJG. Analysis of a Laxity Index database and comparison with the Fédération Cynologique Internationale grades of this population. Vet Comp Orthop Traumatol 2021; 34 (02) 108-114
• 9 Smith GK, Mayhew PD, Kapatkin AS, McKelvie PJ, Shofer FS, Gregor TP. Evaluation of risk factors for degenerative joint disease associated with hip dysplasia in German Shepherd Dogs, Golden Retrievers, Labrador Retrievers, and Rottweilers. J Am Vet Med Assoc 2001; 219 (12) 1719-1724
• 10 Vandekerckhove LMJ, Herregodts S, Saunders JH, Broeckx BJG. Development and validation of a device to measure the force applied to the coxofemoral joint during stress radiography for early diagnosis of canine hip dysplasia. Med Eng Phys 2023; 112: 103953
• 11 Vandekerckhove LMJ, Herregodts S, Saunders JH, Broeckx BJG. Quantifying the stress in stress radiographs to determine sufficient laxity of the coxofemoral joint: A canine hip dysplasia cadaveric study. Vet Comp Orthop Traumatol 2024; 37 (01) 23-29
• 12 Todhunter RJ, Garrison SJ, Jordan J. et al. Gene expression in hip soft tissues in incipient canine hip dysplasia and osteoarthritis. J Orthop Res 2019; 37 (02) 313-324
• 13 Munro R, Munro HMC. Estimation of time since death. In: Animal Abuse and Unlawful Killing. Elsevier; 2008: 88-93
• 14 Smith GK, LaFond E, Heyman SJ, Cofone MA, Gregor TP. Biomechanical characterization of passive laxity of the hip joint in dogs. Am J Vet Res 1997; 58 (10) 1078-1082
• 15 Heyman SJ, Smith GK, Cofone MA. Biomechanical study of the effect of coxofemoral positioning on passive hip joint laxity in dogs. Am J Vet Res 1993; 54 (02) 210-215