1.                        
Injury to the Collateral Cartilage and Collateral Ligament of the Distal Interphalangeal Joint
Intern: Laura A. Axiak, DVM*
Mentor: Natasha M. Werpy, DVM, Dipl. ACVR**
University of Florida
Large Animal Clinical Sciences*
Diagnostic Imaging Department**

2. Signalment & History 11 year old Warmblood gelding
                       
Signalment & History
11 year old Warmblood gelding
Event horse with long history of good performance
Problem: right forelimb lameness of 3 months duration
Previous treatment: routine coffin joint injections of both forelimbs

3. Lameness Examination Straight trot on hard ground
                       
Lameness Examination
Straight trot on hard ground
Grade 2.5/5 right forelimb
Circling on hard ground
Right forelimb lameness is exacerbated circling to the right
Palpation
No significant sensitivities identified
Flexion Test
Negative to proximal and distal limb flexion
Hoof Testers
No response

4. Lameness Video

5. Circling Left

6. Circling Right

7. Diagnostic Analgesia RF Palmar Digital Nerve Block
                       
Diagnostic Analgesia
RF Palmar Digital Nerve Block
90% improvement
RF Abaxial Sesamoid Nerve Block
no additional improvement
Lameness did not switch to left forelimb

8. Problem List Grade 2.5/5 right forelimb lameness Localized to the foot
                       
Problem List
Grade 2.5/5 right forelimb lameness
Localized to the foot
Exacerbated circling right
No palpable sensitivities
No response to hoof testers

9. Differential Diagnoses
                       
Differential Diagnoses
Lesions causing foot lameness are primarily caused by degenerative or traumatic injury localized to these structures:1
Bones: navicular bone, middle phalanx, distal phalanx
Tendons: deep digital flexor tendon, common digital extensor tendon
Ligaments: collateral sesamoidean ligament, impar ligament, collateral ligaments of the distal interphalangeal joint, distal digital annular ligament, chondrocoronal ligaments
Synovial structures: distal interphalangeal joint, navicular bursa, distal aspect of the digital tendon sheath
Other differentials may include foot pain, laminitis, keratoma, space occupying lesions, abscess or infection

10. Diagnostic Plan Radiographs of the Foot Ultrasound
                       
Diagnostic Plan
Radiographs of the Foot
Lateral Projection
Survey view of the distal phalanx, middle phalanx, navicular bone and articular surfaces
Horizontal DP Projection
Used to evaluate the distal interphalangeal joint space
65-degree Dorsoproximal-Palmarodistal Oblique
Aids in evaluation of the distal margin of the navicular bone
Palmaroproximal-Palmarodistal Oblique (Skyline)
Used to evaluate the navicular bone flexor surface and corticomedullary distinction in the navicular bone, as well as the palmar processes of the distal phalanx
Ultrasound
Advanced Imaging (MRI or CT)

11. Right Fore Foot Radiographs
                       
Right Fore Foot Radiographs
Horizontal DP
Lateral

12. 65 degree Dorsoproximal-Palmarodistal Oblique
Right Fore Foot Radiographs
65 degree Dorsoproximal-Palmarodistal Oblique
Lateral
White Outline: Mild enlargement of the lateral fossa of the distal phalanx with focal lucency at the insertion of the lateral collateral ligament (LCL) of the distal interphalangeal joint (DIP Joint)

13. Diagnostic Plan Radiographs Ultrasound of the Foot
                       
Diagnostic Plan
Radiographs
Ultrasound of the Foot
Dorsal approach at and immediately proximal to coronary band is used to evaluate:
Dorsal recess of the DIP Joint
Chondrocoronal ligaments and collateral ligaments of the DIP Joint
Palmar approach between the heel bulbs is used to evaluate:
Proximal aspect of the navicular bone flexor surface
Deep digital flexor tendon
Distal digital annular ligament, collateral sesamoidean ligament
Distal aspect of the digital tendon sheath, proximopalmar recess of the DIP Joint, proximal recess of the navicular bursa
Transcuneal (through the frog) approach is used to evaluate:
Distal aspect of the navicular bone flexor surface
Impar ligament
Distal recess of the navicular bursa, distopalmar recess of the DIP Joint
Advanced Imaging (MRI or CT)

14. Dorsal Ultrasound Approach
                       
Dorsal Ultrasound Approach CC P2 CL CL P2 P3
KEY
DIP – dorsal recess of the DIP Joint
EP – extensor process of the distal phalanx (P3)
P2 – middle phalanx
CC – collateral cartilage
CL – collateral ligament
Collateral Ligaments of the DIP Joint
Originate on medial and lateral eminences of P2
Insert in collateral fossae (depressions) of P3 medial and lateral to the EP
At level of coronary band
10 and 2 o’clock
Concavity of P2
Oval in shape

15. Ultrasound of the Collateral Ligaments of the DIP Joint
                       
Ultrasound of the Collateral Ligaments of the DIP Joint
Probe Position Longitudinal
Probe Position Transverse
Dorsal recess of DIP Joint

16. Right Fore Ultrasound Images
                       
Right Fore Ultrasound Images
MCL and LCL side by side images
*Palmar is to the left of each image * *
MCL
LCL
LCL P2 P2 P2
White Arrow: Area of well defined fiber disruption in the dorsal aspect of the LCL of the DIP Joint at the level of the middle phalanx
Red Arrows: Peri-ligamentous tissue proliferation and swelling with edema and/or displaced ligament fibers

17. Right Fore Ultrasound Images
                       
Right Fore Ultrasound Images
Dorsal recess of DIP Joint
LCL of the DIP Joint
*Palmar is to the left of each image * *
DIP
LCL P2 P2
Dorsal recess of DIP Joint
White Arrows: Moderate proliferative synovitis in the DIP Joint
Red Arrow: Peri-ligamentous tissue proliferation and swelling

18. Diagnostic Plan Radiographs of the Foot Ultrasound
                       
Diagnostic Plan
Radiographs of the Foot
Ultrasound
Advanced Imaging (MRI or CT)
High-field MRI of the right fore foot was performed using multiplanar proton density with and without fat suppression, T2-weighted FSE, STIR and steady-state free precession sequences
Comparative images of the left fore foot were included in the study

19. Proton Density (PD) Transverse Images
                       
LCL Fiber Disruption
Localizer
Proton Density (PD) Transverse Images
Lateral
Palmar
White Arrows: Extensive fiber disruption in the LCL of the DIP Joint throughout its length

20. T2-weighted Dorsal PD Frontal PD Frontal Localizer
Lateral
Lateral
PD Frontal
Distal
Distal
Localizer
White Arrows: DIP Joint recess extension into region of fiber disruption in the LCL of the DIP Joint

21. LCL Injury: Ultrasound Compared to MRI
                       
LCL Injury: Ultrasound Compared to MRI
Palmar
Palmar

22. Partial Thickness Articular Cartilage Defects in DIP Joint
PD Sagittal
T2-weighted Dorsal
Lateral
Lateral
Distal
Distal

23.                        
MRI Diagnosis
Extensive fiber disruption in the LCL of the DIP Joint throughout its length
Separation of the lateral collateral cartilage (LCC) from the lateral palmar process of the distal phalanx
DIP Joint recess extends into region of fiber disruption in the LCL of the DIP Joint in the area where the LCC is separated from the distal phalanx
Mild to moderate resorption of the lateral fossa of the distal phalanx

24. Additional MRI Findings
                       
Additional MRI Findings
Moderate proliferative synovitis in the DIP Joint
Mild to moderate multifocal partial thickness articular cartilage defects in the DIP Joint with moderate proliferative synovitis

25.                        
Comments
The alterations in the fluid distribution and the appearance of fiber disruption are likely explained by the differences between weight bearing US images and non-weight bearing MRI images

26. Positive Contrast Arthrogram (PCA) of the DIP Joint
                       
Positive Contrast Arthrogram (PCA) of the DIP Joint
PCA performed post-MRI as a possible method for monitoring healing, to aid in determining the best time frame for a recheck MRI and to confirm communication with DIP Joint

27. Positive Contrast Arthrogram (PCA) of the DIP Joint
                       
Positive Contrast Arthrogram (PCA) of the DIP Joint
Horizontal DP View
65 Degree Dorsoproximal-Palmarodistal Oblique
Lateral
Lateral
Lateral

28. MRI Compared to Arthrogram
                       
MRI Compared to Arthrogram
Lateral
Lateral
Distal
White Arrows: DIP Joint recess extension into region of fiber disruption in the LCL of the DIP Joint

29. MRI Compared to Arthrogram
                       
MRI Compared to Arthrogram
Lateral
Lateral
Dorsal
Red Box: DIP Joint recess extension into region of LCL of the DIP Joint
White Box: No contrast identified in region of MCL of the DIP joint
Dorsal

30.                        
Therapeutic Plan
Treatment: Ultrasound-guided intra-lesional injection of lateral collateral ligament of the DIP joint with regenerative therapies (stem cells or PRP)
Rehabilitation Program: Rest and hand walking for 4-6 months with recheck diagnostic imaging before any increase in exercise

31.                        
Prognosis
LCL and LCC injury is severe representing permanent structural injury
Extensive fiber disruption in LCL with dorsal DIP joint extension into lesion will have a prolonged healing time
Prognosis for return to previous level of exercise is fair to poor

32.                        
Discussion
Injuries to the collateral ligament of the DIP Joint occur frequently in the axial margin towards the palmar aspect of the ligament at the insertion on the distal phalanx.2,3
Associated osseous abnormalities may include enthesophyte formation, bone fluid, bone loss or the development of an osseous cyst-like lesion.4

33.                        
Osseous injuries are reported to have a higher incidence in the distal phalanx immediately distal and palmar to the insertion of the collateral ligament rather than at the origin on the middle phalanx.3,5
Infrequently, it may be possible to see these changes radiographically, but the majority of these injuries are diagnosed using MRI.4

34.                        
In our experience, collateral ligament tears are frequently occupied by the DIP Joint recesses, especially when located at the level of the DIP Joint or the distal phalanx.
A PCA could be a consideration in cases with an osseous cyst-like lesion on radiographs and ultrasound abnormalities that are not able to have a MRI study.
In addition, this case demonstrates injury to the collateral cartilage in conjunction with collateral ligament injury.

35.                        
Outcome
We have seen several cases. However, only two cases have had a recheck MRI study.
On a 7 month post-injury recheck MRI the collateral ligament had improved, but still had significant abnormalities.
However, the collateral cartilages remained fully separated from the distal phalanx and this space was occupied by the DIP Joint recess.

36.                        
Acknowledgements
The authors would like to acknowledge Dr. Christiana Ober and Dr. Lisa Casinella for referring this interesting case.

37. Further Reading & References
                       
Further Reading & References
Vallance SA, Bell RJ, Spriet M, et al. Comparisons of computed tomography, contrast-enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 2: Lesion identification. Equine Vet J. 2012;44:
Gutierrez-Nibeyro SD, White NA, Werpy NM, et al. Magnetic resonance imaging findings of desmopathy of the collateral ligaments of the equine distal interphalangeal joint. Vet Rad & Ultrasound. 2009;50:21-31.
Dyson S, Blunden T, Murray R. The collateral ligaments of the distal interphalangeal joint: Magnetic resonance imaging and post mortem observations in 25 lame and 12 control horses. Equine Vet J. 2008;40:
Dakin SG, Dyson SJ, Murray RC, et al. Osseous abnormalities associated with collateral desmopathy of the distal interphalangeal joint: Part 1. Equine Vet J. 2009;41:
Dyson SJ, Murray R, Schramme M, et al. Collateral desmitis of the distal interphalangeal joint in 18 horses ( ). Equine Vet J. 2004;36: