Z angle - Dog - axes and angles - Tibia - vet-Anatomy
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Z angle

Z angle

  • Acronym: ZA

Definition

Stephan Mahler

The Z-angle is a measurement used to assess the anatomy of the tibia and its modification in predisposed dogs or dogs at risk for cranial cruciate ligament rupture. It is determined from a mediolateral radiograph of the tibial. The X-ray beam is centred at the stifle joint, with the normal standing joint angles of the pelvic limb. The mediolateral projection is considered acceptable when the medial condyle and lateral condyle of femur are superimposed.

The Z-angle is the angle between the mechanical tibial axis and a line joining the most cranial aspect of the tibial tuberosity to the midpoint between the medial intercondylar tubercle and the lateral intercondylar tubercule.

The following values have been published for the Z-angle in healthy dogs:

  • German Shepherd and Basset hound population : 63.00° (53.00-72.50) Guénégo et al 2017

  • Small breed dogs : 70.02 +/- 5.6° (Aertsens et al. 2015)

  • Large breeds : 64.0 +/- 4.7° (Aertsens et al. 2015)

  • Labrador Retrievers : 58.8 +/- 3.2° (Vedrine et al. 2013)

  • Yorkshire Terriers : 69.2 +/-4.5° (Vedrine et al. 2013)

  • Small breed dogs : 70.4+/-9° (Witte 2015)

References

  • Aertsens A, Rincon Alvarez J, Poncet CM, Beaufrère H, Ragetly GR. Comparison of the tibia plateau angle between small and large dogs with cranial cruciate ligament disease. Vet Comp Orthop Traumatol. 2015;28(6):385-90. doi: 10.3415/VCOT-14-12-0180. Epub 2015 Sep 18. PMID: 26382888.

  • Guénégo L, Payot M, Charru P, Verwaerde P. Comparison of tibial anatomic-mechanical axis angle between predisposed dogs and dogs at low risk for cranial cruciate ligament rupture. Vet J. 2017 Jul;225:35-41. doi: 10.1016/j.tvjl.2017.04.011. Epub 2017 May 3. PMID: 28720297.

  • Vedrine B, Guillemot A, Fontaine D, Ragetly GR, Etchepareborde S. Comparative anatomy of the proximal tibia in healthy Labrador Retrievers and Yorkshire Terriers. Vet Comp Orthop Traumatol. 2013;26(4):266-70. doi: 10.3415/VCOT-12-02-0018. Epub 2013 Apr 24.

  • Witte PG. Tibial anatomy in normal small breed dogs including anisometry of various extracapsular stabilizing suture attachment sites. Vet Comp Orthop Traumatol. 2015;28(5):331-8. doi: 10.3415/VCOT-14-12-0186. Epub 2015 Jul 21. PMID: 26195139.

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