Impact of Size and Shape of Equine Femoral Subchondral Bone Cysts With a Transcondylar Screw on Predicted Bone Formation Area in a Finite Element Model.

The research investigates the influence of the size and shape of horse femoral subchondral bone cysts on the effectiveness of a surgical treatment involving a transcondylar screw. The research finds that larger cysts, particularly those of greater height, respond best to this treatment method.

Introduction to Equine Subchondral Bone Cysts and Their Treatment

• Subchondral bone cysts (SBCs) are a common problem in horses, particularly yearlings intended for performance. They usually develop in the medial femoral condyle (MFC) and often cause lameness and secondary injuries to the meniscus and tibial cartilage.
• A surgical technique involving the insertion of a transcondylar lag screw (TLS) across an affected MFC has been shown to be successful in resolving lameness and promoting healing of the SBC.
• This is because, as shown through finite element analysis in a previous study, the TLS stimulates bone formation on the inner surface of the SBC, and changes the direction of surface compression to align with the screw axis.

Objective and Methodology of the Study

• This research extends the previous finite element analysis by testing several sizes and shapes of SBCs in a new equine stifle finite element model (FEM).
• The goal was to determine how the size of the cyst impacts the ability of the TLS to stimulate bone formation.

Key Findings of the Research

• The research found that a transcondylar screw works best in stimulating bone formation in cysts of greater height, and increases stress stimulus in the bone around the cyst, promoting bone apposition (the addition of new bone).
• The screw also directs compression across the cyst, which aids in healing. If the screw can fully penetrate the cyst, its use is recommended for treating SBCs.

Future Research Recommendations

• The researchers acknowledge that their findings apply best to larger cysts that can be accessed by a TLS. Smaller cysts that can’t be accessed by the current screw surgical approach remain a challenge.
• Future research could study the efficacy of a dual-pitch headless screw, which may be able to reach and treat smaller cysts effectively.