Bone Cyst Surgery: How CT Can Help

Introduction:
Subchondral cystic lesions (SCLs) including osseous cyst-like lesions in the equine limb pose a significant problem because of inflammation, cartilage degeneration and lameness. Surgical treatment is often recommended, especially in horses that are refractory to conservative management. This includes debridement of the cyst and depending on the surgeon’s preference, filling of the lesion with cancellous bone, osteochondral grafts, parathyroid hormone peptide (PTH1-34) or a combination of bone substitutes, growth factors and chondrocyte grafts or mesenchymal cells in fibrin glue.

Successful debridement depends on detection and precise localization of the subchondral lesions. A 30-50% change in bone density must be present before subchondral lesions can be seen on radiographs, and it must also be considered that in conventional radiography, the brightness on the film reflects the summation of the densities of all tissues penetrated by the x-ray beam. It is therefore not surprising that radiography has limited application for the detection of small SCLs as well as irregular subchondral defects.

Computed tomography (CT) is a useful method for the early diagnosis of SCLs because it allows determination of the exact location of the lesion as well as the presence of concurrent fissures, osteoarthritis, periosteal reaction and communication between the SCL and adjacent cartilage. A good visual understanding of SCLs by the surgeon aids in debridement of cysts and improves the outcome. Several studies have found that 3D imaging is superior to radiography for preoperative planning and intraoperative control of treatment in orthopaedic surgery of the equine limb as well as for postoperative evaluation.  [...]