Fractures of the Distal Phalanx and Associated Soft Tissue and Osseous Abnormalities in 22 Horses With Ossified Sclerotic Ungual Cartilages Diagnosed With Magnetic Resonance Imaging

Abstract

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.

Evaluation of the diagnostic accuracy of skeletal scintigraphy for the causes of front foot pain determined by magnetic resonance imaging

“…Excellent agreement between radiographic and scintigraphic grades of ossification of the ungular cartilages has been previously identified, and all cartilages with a fracture had corresponding increased radiopharmaceutical uptake . Injuries to these structures are typically traumatic in origin and are associated with osseous remodeling . Increased deposition of radiopharmaceutical occurs at sites undergoing active modeling or remodeling, in association with osteoblastic activity .…”

“…11 Injuries to these structures are typically traumatic in origin and are associated with osseous remodeling. 2,8,9,12,15,16 Increased deposition of radiopharmaceutical occurs at sites undergoing active modeling or remodeling, in association with osteoblastic activity. 17 When ungular cartilages were analyzed alone, the agreement was stronger than when combined with chondral ligaments.…”

Magnetic resonance protocols in equine lameness examination, used sequences, and interpretation

“…PD, T2w and STIR images were consistent with inflammation/degenerative changes, while decreased signal on PD and T2w is consistent with fibrosis/scaring (Selberg andWerpy 2011). Maher et al (2011) have suggested that tendon lesions with increased signal on PD images without signal increase on STIR and T2w images can be associated with degeneration.…”

“…Hematoma, bone hemorrhage in most cases appears as increased signal on both T1-and T2w images (Selberg andWerpy 2011, Werpy 2012).…”

“…Sclerosis of the ossified ungual cartilage was observed as an area of low signal intensity on T1w and PD images (Selberg and Werpy 2011).…”