Ex vivo equine medial tibial plateau contact pressure with an intact medial femoral condyle, with a medial femoral condylar defect, and after placement of a transcondylar screw through the condylar defect.

The research article investigates how a defect in the Medial Femoral Condyle (MFC) of a horse’s knee and treatment with a transcondylar screw impact pressure on the medial tibial plateau. The conditions studied include an intact MFC, an MFC with a defect, and a defect treated with a screw.

Research Methodology

The research experiment was conducted on six stifle joints, extracted from four horses. The test involved axial loading of the joints to 1800 N at three different angles: 155°, 145°, and 130°. The loading was administered under three different conditions:

• With an intact Medial Femoral Condyle (MFC)
• With an MFC presenting a 15mm circular osteochondral defect
• With a transcondylar screw inserted in lag fashion through the defect

The pressure exerted on the medial tibial plateau, the area of contact, the peak pressure, and the force were measured using an electronic pressure sensor, Tekscan®. This data was used to calculate the stress load, which was broken down further into its components in three sub-regions of the medial plateau: the cranial, caudal, and central regions.

Results Analysis

The results showed that increased flexion led to higher contact area, force, and stress load on the medial tibial plateau in all the conditions. The presence of an MFC defect significantly reduced the force at both flexion angles and the contact area at 145°. However, the insertion of transcondylar screw managed to restore the force to the levels of an intact medial femoral condyle at 130°, also reducing the contact area when the joint was extended.

Contact Maps Conclusions

Contact maps of an intact MFC displayed pressure peaks on the central cartilage at all angles studied. They also showed an expansion of contact pressure and area, as well as a caudal movement during flexion. However, with an MFC defect, the caudal and abaxial pressure movement was amplified during flexion without any further change upon insertion of the screw.

Overall Conclusions

The findings of the study indicate that the stifle flexion increases the force, contact area, and stress load on the medial tibial plateau, with most pronounced impacts occurring caudally. It also reveals that an MFC defect changes the load on the medial tibial plateau, but the insertion of a transcondylar screw can reverse some of these changes.