Biomechanical investigation of the association between suspensory ligament injury and lateral condylar fracture in thoroughbred racehorses.

The study explores the potential link between injuries in the medial branch of the suspensory ligament (MBSL) in horses and the occurrence of lateral condylar fractures, through an investigation involving seven thoroughbred horse cadavers.

Study Design and Methodology

• The design of the research was an in vitro biomechanical experiment performed on seven thoroughbred horse cadavers’ right forelimbs.
• Several measurements were made on different parts of the limb, such as the third metacarpal bone’s (MC3) lateral and medial condylar, as well as dorsal, and abaxial bone surface strains, and distal joint angles.
• This was done before and after partial transection of the MBSL, a process similar to a partial cut to the ligament, to simulate injury.
• The strains on the bone and angles of the joints were observed and compared under varying axial limb compression loads, specifically at 1,400-, 3,000-, and 5,600-N loads.

Results and Findings

• As the axial load was increased, strains on all bone locations also increased.
• After the MBSL was partially transected, all lateral condylar bone strains were found to be significantly higher, indicating increased pressure or stress on these areas due to the ligament injury.
• Medial condylar bone strain on the abaxial surface was significantly lower after partially cutting the MBSL.
• The joints at the distal parts of the limb, meanwhile, were seen to become more flexed or extended as the axial load increased. However, these changes were not significantly different even after partially transecting the MBSL.

Conclusions and Clinical Relevance

• The findings suggested that partial transection, or “damage,” to the MBSL results in increased in vitro lateral condylar bone surface strains in the MC3.
• In practical terms, this implies that injuries to the medial branch of the suspensory ligament in thoroughbred horses could result in an increased risk of lateral condylar fractures.
• The increased bone strain in the lateral condyle caused by the loss of integrity in the suspensory ligament is consistent with the conditions promoting such fractures.