Imaging

Question 1

Nagahiro AJVR 2023

MPL gr 4 classified according to Singleton -> skeletally mature and immature

Answer 1

Immature group had higher aLDFA and lower QML/FL

median ALDFA 99, immature 109, mature 95 -> not all grade 4s have abnormal ALDFA! (94-98 normal)

QML/FL overall lower in both groups vs normal (0.87-1.0 normal)
immature <0.8

Grade 4 MPLs <10mo more likely to require DFOs or segmental femoral osteotomy

Question 2

Concurrent CrCL

Answer 2

20% middle-older dogs
50% small dogs
10% grade 4 MPLs - mean age 6mo, risk increases with increasing age

Question 3

Trochlear anatomy

4 CT, 1 U/S
1 retrospective blinded

Answer 3

Measuring trochlear depth

1) Petazzoni VCOT 2018
-Normal dogs, CT
-Maximal depth of trochlea was 46% of patellar thickness (0.46)
-Breed variation

2) Longo VS 2020
-Cadaveric, normal dogs, CT
-Deepest trochlear points were between P25 and P50
-P25 most precise and accurate for measuring trochlear depth

3) Longo VS 2023
-CT dogs with and dogs without MPL at P25
-Without MPL dogs had deeper groove
-Small dogs shallower than medium/large
-Sulcus angle <134 small dogs, <128 large dogs -trochleoplasty cutoff?

4) Sasaki VCOT 2022
-CT sulcus angle of small dogs with and without MPL
-Deepest portion of trochlea was tangent to femoral trochlea 15deg to anatomic axis of femur
-Sulcus angle higher in gr 3 and 4 vs normal
-No diff in gr 1 and 2

5) Sasaki VCOT 2023
-U/S sulcus angle
-Maturation of femoral trochlea complete by 6mo

6) Matchwick VCOT 2021
-Retrospective blinded
-Measuring trochlear depth of 3 brachy breeds using T/P ratio
-Pugs 0.45, Frenchies 0.38, English Bulldogs 0.4
-Mean T/P sg reduced in brachys

Question 4

Patellar positioning

IS
Mod IS
Angular based index

Answer 4

Insall-Salvati
1) Ocal VCOT 2020
-Mod IS
-Cranial patellar lig length (instead of caudal patella)

2) Murakami VCOT 2023
-MPL vs control
-Rads in full stifle extension needed to recognise proximal patella
-11 stifles in MPL and 1 in control group had functional patella alta

Angular based index
3) Allberg VCOT 2020
-Caudal aspect of femoral and tibial condyles and apex of patella was insensitive to joint angle variation
-Unaffected by TT displacement
-> Tested by Giansetto VCOT 2023 - patella was distally displaced after MMP but is not predictive of patellar luxation

Question 5

QML / FL

Answer 5

1) Nagahiro VS 2023
-Small dogs with MPL
-QML/FL increases with increasing age in affected dogs
-Grade 4 MPLs had sig lower QML/FL

2) Murakami VCOT 2020
-Effect of limb position
-Normal dogs, CT
-QML/FL increased with hip extended or stifle extended - avoid these positions

Question 6

Femoral torsion

CT graphical method
AMM
BMM

Answer 6

CT graphical method (arc and chord)
1) Eby VS 2020
-14 normal, 14 bone deformities a/w patellar lux
-Geometric methods provided accurate estimate of distal femoral transverse bone morphology and allowed for accurate correction of torsion

3D volumetric reconstruction of CT
2) Serck VS 2021
-Axial measurement method - femoral head and neck angle to transcondylar axis, axial view
-Biplanar measurement method - trig to derive angle of anteversion of femoral neck wrt proximal femoral axis
-Both can be used to measure femoral torsion

Question 7

Femoral varus

Caudocranial rads

Deg of ALDFA where DFO is required is controversial
-Lee BMC 2020: computer model, ALDFA >103deg resulted in MPL in absence of other factors

Answer 7

Rads VS CT
1) Clark VCOT 2023
-Caudocranial rads
-Bland-Altman plot shows trend of higher measurements in rads vs CT as ALDFA increases
-Rads overestimated ALDFA by 1.8deg vs CT
-Rads useful to exclude those with true ALDFA >102deg (98% NPV)
-15deg wide range of agreement which hinders comparability of measurements between the 2 methods

Craniocaudal rads:
2) Dudley VRU 2006: CT and rads were accurate to femoral anatomic preparations
3) Aper VRU 2005: CT accurate to direct anatomic rads for tibial torsion
4) Newman VCOT 2017: CT needed to mitigate inaccuracies due to positioning
5) Jackson VS 2012: elevation of femur >5deg sig changes ALDFA

Question 8

Tibial torsion

3D volume rendering
Axial method
Cortical arc length

Answer 8

1) Longo VS 2021
-Cadaveric study, normal dogs
-3D volume rendering and AMM both methods accurate and precise

2) Longo VS 2022
-Retrospective
-CT cortical arc length
-Femoral and tibial derotational osteotomies
-9% major comp - higher comp rate when both performed in same limb
-94% good outcome