Findings:
- The medial fossa of the distal phalanx is moderately to severely widened with smooth rounded margins and a central region of increased T2 and T1 hyperintensity (yellow arrows). Additionally, there is moderate resorption affecting the lateral fossa of the distal interphalangeal joint collateral ligament insertions.
- The medial distal interphalangeal joint collateral ligament is severely thickened with moderate to severe palmar fiber disruption at the distal phalanx insertion. Mild to moderate fiber abnormalities and peri-ligamentous soft tissue thickening extends proximally to the origin (blue arrows). Similar but less extensive mild to moderate changes at noted within the lateral distal interphalangeal joint collateral ligament.
- The distal interphalangeal joint capsule is moderately to severely thickened and distended with effusion. Mild to moderate osteophyte formation is seen along the periarticular margins.
- At the impar ligament insertion on the plantar aspect of the distal phalanx, mild to moderate enthesophyte formation is seen. Additionally, there is mild compact bone fluid and/or demineralization of the deep digital flexor tendon insertion.
- The navicular bone has moderate synovial invagination enlargement and a coarse trabecular bone pattern. The navicular bursa contains a mild to moderate amount of effusion.
- Along the periarticular margins of the proximal interphalangeal joint, mild osteophyte formation is seen. A focal defect articular cartilage is noted in the mid aspect of the joint located lateral of midline affecting the middle phalanx.
- The deep digital flexor tendon has mild dorsal margin fraying and fibrillation at the level of the middle phalanx.
- There is mild to moderate bilateral collateral cartilage ossification.
Conclusions:
- Severe desmopathy and enthesopathy, medial collateral ligament of the left distal interphalangeal joint
- Moderate to marked proliferative synovitis and mild arthrosis, left distal interphalangeal joint
- Mild to moderate impar ligament insertional enthesopathy and mild compact bone fluid and/or demineralization of the deep digital flexor tendon insertion, distal phalanx
- Mild to moderate desmopathy, lateral collateral ligament of the distal interphalangeal joint
- Moderate synovial invagination enlargement with a coarse trabecular bone pattern, navicular bone
- Mild to moderate left navicular bursitis
- Mild left deep digital flexor tendinopathy
- Mild to moderate collateral cartilage ossification, distal phalanx
- Mild osteoarthrosis and focal articular cartilage defect, proximal interphalangeal joint
Case follow-up:
- Radiograph-guided PRP injections at the distal insertion of the left DIP medial collateral ligament.
A little bit more…
- The collateral ligaments of the DIP joint are located on the dorsomedial and dorsolateral aspect of the joint (Zubrod et al.)
- origin: depression on the middle phalanx
- insertion: distal phalanx abaxial to the extensor process
- Lateral/medial strain may be a cause of injury, such as secondary to exercising on uneven surface, hoof imbalance, angular limb deformity, and abrupt stopping/turning (Zubrod et al.).
- Injuries can happen anywhere (body and insertions) (Zubrod et al.).
- In a Study by Beasley et al., out of 48 horses..
- 27 lesions were distal to the coronary band
- 15 were proximal to the coronary band
- 5 lesions involved the entire ligament
- 1 CL had proximal and distal focal lesions
- Reported to represent 3.5% of the foot lamenesses in a referral institution by Turner et al.
- Has a 15–30% prevalence in horses with chronic lameness and who undergo MRI (Gutierrez‐Nibeyro et al.).
- In some cases, mild soft tissue swelling can be seen on the dorsomedial or dorsolateral aspect of the coronary band (Gutierrez‐Nibeyro et al.).
- Approximately 2/3 of patients have no radiographic abnormalities (Zubrod et al.).
- The most proximal aspect of the ligament can be assessed with ultrasound, and advanced imaging is necessary to evaluate the remainder of the ligament (Gutierrez‐Nibeyro et al.).
- MRI features (Dyson et al., Zubrod et al., Gutierrez‐Nibeyro et al.):
- Increases STIR and T2 signal intensity within the ligament, periligamentous tissues and/or bone at insertion(s)
- Thickening of the affected ligament
- Fiber disruption (heterogeneity and/or tear)
- Increased signal intensity the collateral ligaments should be interpreted with caution because normal collateral ligaments that are oriented at an angle of 55±10° to the static magnetic field may have increased signal intensity
- Poor prognosis for return to soundness. Often times, other lesions are present which may be contributing to the lameness (Gutierrez‐Nibeyro et al.).
- No significant association between severity or lesion location and time to return to work in horses that recover
- Local therapies (biologics) and shockwave may help with recovery.
References:
- Dyson SJ, Murray R, Schramme M, Branch M. Collateral desmitis of the distal interphalangeal joint in 18 horses (2001–2002). Equine veterinary journal. 2004 Mar;36(2):160-6.
- Fürst AE, Lischer CJ. Other clinical problems of the equine foot. Veterinary Clinics: Equine Practice. 2021 Dec 1;37(3):695-721.
- Zubrod CJ, Farnsworth KD, Tucker RL, Ragle CA. Injury of the collateral ligaments of the distal interphalangeal joint diagnosed by magnetic resonance. Veterinary Radiology & Ultrasound. 2005 Jan;46(1):11-6.
- 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 veterinary journal. 2008 Sep;40(6):538-44.
- Gutierrez‐Nibeyro SD, White NA, Werpy NM, Tyrrell L, Allen KA, Sullins KE, Mitchell RD. Magnetic resonance imaging findings of desmopathy of the collateral ligaments of the equine distal interphalangeal joint. Veterinary Radiology & Ultrasound. 2009 Jan;50(1):21-31.
- Turner TA, Sage AM. Desmitis of the distal interphalangeal collateral ligaments: 22 cases. InProc. Am. Ass. equine Practnrs 2002 (Vol. 48, pp. 343-346).
