Radiographs:
- Within the stifle joint, adjacent to the lateral intercondylar eminence, there is a well-defined, irregularly marginated and round mineral opaque fragment (yellow arrows). Best seen on the lateromedial projection, adjacent to this osseous fragment, there is a focal, well-defined concavity and irregularity of the medial intercondylar eminence with mild osseous proliferation.
- Only seen on the caudocranial projection, at the base of the intercondylar eminences, there are numerous, punctate lucencies.
Ultrasound:
- The cranial tibial meniscal ligament is enlarged with an abnormal contour and heterogeneous and disorganized fiber pattern, worst in the cranioproximal portion of the ligament. Mild enthesiopathy is seen at the attachment of the cranial tibial meniscal ligament.
- In the region of the intertubercular eminences of the tibia, a focal, hyperechoic, irregularly and shadowing fragment is seen.
- The medial femorotibial joint contains a small to moderate amount of joint effusion. Along the joint margins, mild osteophyte formation is seen.
Conclusions:
- Right stifle intra-articular mineralized body and adjacent medial intercondylar eminence irregularity. Considerations include fracture of the medial intercondylar eminence of the tibia or ligamentous avulsion (e.g. cranial cruciate ligament, or lateral meniscotibial ligament), dystrophic mineralization, or less likely an osteochondral fragment.
- The punctate lucencies seen at the base of the intercondylar eminences are thought to represent vascular ingrowth or synovial invaginations
- Cranial meniscotibial desmopathy
- Mild right stifle osteoarthrosis and synovitis
Arthroscopy:
- Arthroscopic evaluation of the right femorotibial joint revealed moderate to severe chondromalasia of the medial femoral condyle, moderate fraying and fibrillation of the medial and lateral cranial meniscotibial ligaments, and mild to moderate fraying and fibrillation of the medial and lateral menisci. There was a transverse linear defect in the medial intercondylar eminence. Attempts to isolate the lateral intercondylar eminence osseous fragment were made, but due to the important soft tissue structures that would need to be disrupted, such as the cranial and caudal cruciate ligament, further attempts were aborted.
- Given the cartilage damage, the prognosis for athletic performance was deemed poor; however, prognosis for pastures soundness is thought good. Continued exercise can ultimately lead to further progression of the osteoarthritis in the right stifle joint. Intra-articular steroid injections were recommended to decrease the inflammation, and allow comfortable ambulation. Long term use of a COX-2 specific non-steroidal anti-inflammatory medications may also help manage discomfort.
A little bit more…
- Fractures of the medial intercondylar eminence of the tibia are not avulsion injuries and are often due to trauma. Lateral motion of the medial femoral condyle during trauma, combined with the outward rotation of the tibia during stifle joint extension, may contribute to fracture.
- These should not be confused for avulsion injuries at the distal attachment of the cranial cruciate ligament, as one study noted it to remain intact in ~30% of the horses. Some horses with medial intercondylar eminence fractures may also have damage to the CraCL due to their close anatomical proximity. Iatrogenic damage to the CraCL during medial intercondylar eminence fragment removal has been reported. Experimental studies suggest combined mid-substance CraCL failure and medial intercondylar eminence of the tibia fracture occur more frequently in older animals, though further research is needed (Rubio‐Martínez et al.).
- Affected horses show varying degrees of lameness and damage to articular soft tissue structures. Other soft tissue structures were less frequently involved, but injuries may result from the initial trauma or joint instability. The cranial ligament of the medial meniscus, located directly cranial to the medial intercondylar eminence of the tibia, was the second most frequently injured structure. Damage to the articular cartilage of the medial femoral condyle was present in 66% of horses, often mild, likely due to the close apposition of the medial intercondylar eminence of the tibia and medial femoral condyle (Rubio‐Martínez et al.).
- Radiographs are effective in identifying medial intercondylar eminence of the tibia fractures, with the caudocranial view being most useful. Ultrasonography can identify fractures and soft tissue injuries in many cases but given the intra-articular location of these fragments, visualization with ultrasound may be difficult. Advanced imaging modalities like CT and MRI are superior if able to image the proximal limb (dependent on CT/MRI systems and size of horse).
- Arthroscopic approaches vary, with the lateral approach to the cranial compartment of the MFTJ being most common. Preoperative imaging is recommended to assess the location of displaced medial intercondylar eminence of the tibia fragments. Arthroscopic removal of medial intercondylar eminence of the tibia fractures generally result in a good prognosis, with 76.19% of horses reported as sound and 65% returning to previous or intended use (Rubio‐Martínez et al.). Early removal of fragments is advised to minimize damage to articular soft tissue structures and improve prognosis.
References:
- Rubio‐Martínez LM, Redding WR, Bladon B, Wilderjans H, Payne RJ, Tessier C, Geffroy O, Parker R, Bell C, Collingwood FA. Fracture of the medial intercondylar eminence of the tibia in horses treated by arthroscopic fragment removal (21 horses). Equine veterinary journal. 2018 Jan;50(1):60-4.
