Introduction

The graphic representation of bone axes and joint angles provides an in-depth understanding of the biomechanics and pathological processes that can affect the thoracic and pelvic limbs in dogs. The use of precise, reproducible measurements guarantees reliable, comparable values within an animal and from one study to the other. 
These measurements have been particularly refined for understanding angular deformities of the long bones, coxofemoral and elbow dysplasia, congenital luxation of the patella and rupture of the cranial cruciate ligament. They are also an essential step in planning corrective (surgical) procedures and evaluating their results.
In this module, we have grouped together the main radiology measurements described in canine orthopedics, including pelvimetry. The anatomical landmarks required for these measurements have been highlighted.
 

Material and methods

Radiographic exams and CT scans of the thoracic and pelvic limbs of dogs were provided by Dr Susanne Boroffka, DVM,  dipl. ECVDI, PhD (Utrecht, Netherlands) and Thierry Boulet, DVM, Certificate of Advanced Education in Animal Osteoarticular Traumatology and Orthopedics (St Jean de Védas, France).

Measures were drawn on the images by Stephan Mahler DVM, MA, MSc, PhD (Veterinary Anatomist - IMAIOS). They have been grouped into different themes:

• Bones
• Bony landmarks
• Bone axes
• Joint orientation lines
• Joint orientation angles
• Bone measurements 
• Bone areas
• Percentages and indexes

Definitions of the measures were systematically proposed. Normal values of the anatomical measurements found in the literature were supplemented.

List of abbreviations: 
a-mAA: Anatomical-mechanical axis angle
AAA: Acetabular anteversion angle
aCdDFA: Anatomic caudal distal femoral angle
aCdDRA: Anatomic caudal distal radial angle
aCdPFA: Anatomic caudal proximal femoral angle
aCdPRA: Anatomic caudal proximal radial angle
aCrPRA: Anatomic cranial proximal radial angle
AD: Acetabular depth
aFA: Anatomic femoral axis
aHA: Anatomic humeral axis
AI: Acetabular index
AIA: Acetabular index angle
aLDFA: Anatomic lateral distal femoral angle
aLDHA: Anatomic lateral distal humeral angle
aLDRA: Anatomic lateral distal radial angle
aLPFA: Anatomic lateral proximal femoral angle
aMPHA: Anatomic medial proximal humeral angle
aMPRA: Anatomic medial proximal radial angle
aRA: Anatomic radial axis
aTA: Anatomical tibial axis
AW: Acetabular width
BAD: Bi-acetabular distance
BID: Bi-iliac distance
CD: Conjugata diagonalis
CdCTA: Caudal condylar tibial axis
CEA: Center-edge angle
DAA: Distal angle of anteversion
DaFA: Distal anatomic femoral axis
DASA: Dorsal acetabular sector angle
DCrTA: Distal cranial tibial axis
DFHCAI: Dorsal femoral head coverage area index
DFHCWI: Dorsal femoral head coverage width index
DFJOL: Distal femoral joint orientation line
DHJOL: Distal humeral joint orientation line
DPTA: Diaphyseal proximal tibial angle
DRJOL: Distal radial joint orientation line
DTJOL: Distal tibial joint orientation line
ECA: Elbow compression angle
ERP: Elbow rotational position
FHCP: Femoral head coverage percentage
FIA: Femoral inclination angle
FNA: Femoral neck axis
FNAA: Femoral neck anteversion angle
FPA: Femoral procurvation angle
FTA: Femoral trochanteric angle
FVA: Femoral varus angle
GTI: Greater tubercle inclination
GTO: Greater tubercle offset
HASA: Horizontal acetabular sector angle
HTA: Humeral torsion angle
HTEA: Horizontal toit externe angle
HTED: Humeral transepicondylar distance
IA: Iliac axis
ID: Distraction index
LBID: Lateral bi-ischiatic distance
MBID: Medial bi-ischiatic distance
mCaPHA: Mechanical caudal proximal humeral angle
mCdDFA: Mechanical caudal distal femoral angle
mCdDTA: Mechanical caudal distal tibial angle
mCdPFA: Mechanical caudal proximal femoral angle
mCdPTA: Mechanical caudal proximal tibial angle
mCMA: Mechanical carpus/metacarpus axis
mCrDHA: Mechanical cranial distal humeral angle
mCrDTA: Mechanical cranial distal tibial angle
mCrPTA: Mechanical cranial proximal tibial angle
mFA: Mechanical femoral axis
mHA: Mechanical humeral axis
mLDFA: Mechanical lateral distal femoral angle
mLDHA: Mechanical lateral distal humeral angle
mLDRA: Mechanical lateral distal radial angle
mLDTA: Mechanical lateral distal tibial angle
mLPCMA: Mechanical lateral proximal carpus/metacarpus angle
mLPFA: Mechanical lateral proximal femoral angle
mLPTA: Mechanical lateral proximal tibial angle
mMDTA: Mechanical medial distal tibial angle
mMPHA: Mechanical medial proximal humeral angle
mMPRA: Mechanical medial proximal radial angle
mMPTA: Mechanical medial proximal tibial angle
mRA: Mechanical radial axis
mTA: Mechanical tibial axis
NA: Norberg angle
PAA: Proximal angle of anteversion
PaFA: Proximal anatomic femoral axis
PFJOL: Proximal femoral joint orientation line
PHJOL: Proximal humeral joint orientation line
PRJOL: Proximal radial joint orientation line
PTA: Patellar tendon angle
PTA: Proximal tibial axis
PTJOL: Proximal tibial joint orientation line
PTTA: Proximal tibial tuberosity angle
QA: Quadriceps angle
RTA: Radial torsion angle
rTTW: Relative tibial tuberosity width
SD: Diameter sagittalis
TCTA: Transcondylar tibial axis
TPA: Tibial plateau angle
TPO: Tibial plateau orientation
TTA: Tibial torsion angle
TV: Tibial valgus
VASA: Ventral acetabular sector angle
ZA: Z angle
θ: θ angle