The role of computed tomography in evaluation of subchondral osseous lesions in seven horses with chronic synovitis.

This research article deals with seven cases of lameness in horses which turned out to be severe, persistent and suddenly onset. The study used scintigraphy and computer tomography as major diagnostic tools to identify and evaluate subchondral osseous lesions, suspects of occult fracture or osteomyelitis, that could potentially be causative of the observed lameness.

Methodology

The following protocol was enacted to gather the necessary data for the study:

• Localization of the lameness was undertaken with it being found to affect the front fetlock joint in two horses and the tibiotarsal joint in the remaining five.
• A commonality was found among five of the horses, all of which had a history of intra-articular injections into the affected joint prior to the presentation of symptoms.
• All horses showed signs of joint effusion and flexion tests came out positive.
• Intraarticular anaesthesia was enacted, which led to a complete cessation of the lameness in four cases, while nerve conduction block proximal to the joint improved lameness in one case.
• A cytology examination of fluid drawn from the affected joints identified regular joint fluid in one horse while the other six showed an increase in nucleated cell counts and total protein. In two of these horses, the presence of bacteria was also confirmed.
• Start-up radiographs were used to check for any significant changes that could help explain the lameness. Such changes, however, were either non-existent in four of the cases or insufficiently explanatory in the remaining ones.

Results

Upon gathering and evaluating the collected data, the following results were obtained:

• In six of the cases where scintigraphy was done, intense focal isotope uptake was noted in the area of suspicion. This area corresponded to the proximal portion of the first phalanx in two cases as well as the distal tibia and talus in the other four.
• Computed tomography, which was performed to detect any apparent fractures or osteomyelitis, identified hypodense lesions with hyperdense halos in the subchondral bone. These were located in the sagittal groove of the first phalanx in two cases, the cochlea of the distal tibia in another two and in the intertrochlear portion of the talus in three cases.
• CT scans also revealed communication between the lesion and the joint space in five of the cases.
• A post-mortem examination of one case revealed the presence of synovitis and a chronic bone abscess, also known as a Brodie’s abscess, which was communicating with the joint space.