Subchondral cyst-like lesions
There are 2 possible causes for the development of subchondral bone cysts,
either the manifestation of osteochondrosis with thickened necrotic cartilage
persisting as a localized defect within the subchondral bone or localized
trauma causing focal damage primarily to the articular cartilage but also the
underlying subchondral bone. Cyst formation follows osteolysis caused by
cyclical fluid pressure from the synovial fluid.
The developmental form is obviously found primarily in young horses while the
traumatic form is seen in mature athletes. Young horses present with mild
lameness, frequently bilateral. Mature athletes can present with acute, severe
lameness that proves non-responsive to rest. Cyst-like lesions are best are
seen best on the caudocranial or caudolateral-craniomedial oblique
projections, but recently a distoproximal flexed lateromedial projection proved
especially informative for assessment of the articular surface at the entrance
of the cyst (Barrett et al. 2014).
Conservative management (i.e. 6 months rest) may restore soundness but
only in a limited number of cases. Arthroscopic medication of bone cysts with
corticosteroids is an effective treatment that is currently favoured by most
surgeons (Wilderjans 2015). We find this treatment much more effective than
medication with ultrasound guidance because arthroscopic medication
ensures corticosteroid delivery into the bone cyst, while ultrasound guided
medication is usually done somewhere random near the stifle. Arthroscopic
medication also enables concurrent assessment for any concurrent joint
pathology and removal of detached cartilage from the cloaca of the cyst.
Cases where corticosteroid injection has failed can be treated by surgical
debridement of the cyst while maintaining as much of the subchondral bone in
the region of the cloaca as possible. Cartilage resurfacing techniques using
autogenic chondrocyte or stem cell implantation or autogenic bone-cartilage
transplants have been reported but are not practical without a cell-culture
laboratory on site. More recently, a transcondylar screw technique has been
reported to give good results.
Selected Bibliography
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Barrett MF and Selberg K (2012) How to Obtain Flexed Lateral Oblique Radiographs of the Equine Stifle.
th
Proceedings of the 58 AAEP, Anaheim, USA, pp. 383-387.
Dyson, S. (1994) Stifle trauma in the event horse. Equine vet. Educ. 6, 234-240.
Dyson, S., Wright, I., Kold, S. and Vatistas, N. (1992) Clinical and radiographic features, treatment and
outcome in 15 horses with fracture of the medial aspect of the patella. Equine vet. J. 24, 264-268.
Ferris DJ, Frisbie DD, Kisiday JD, McIlwraith CW, Hague BA, Major MD, Schneider RK, Zubrod CJ, Kawcak
CE, Goodrich LR. Clinical Outcome After Intra-Articular Administration of Bone Marrow Derived Mesenchymal
Stem Cells in 33 Horses With Stifle Injury. Vet Surg. 2014 Jan 16. doi: 10.1111/j.1532-950X.2014.12100.x
Fowlie JG, Arnoczky SP, Lavagnino M, Stick JA. Stifle extension results in differential tensile forces developing
between abaxial and axial components of the cranial meniscotibial ligament of the equine medial meniscus: a
mechanistic explanation for meniscal tear patterns. Equine Vet J. 2012 Sep;44(5):554-8.
Hendrickson DA, Nixon AJ. A lateral approach for synovial fluid aspiration and joint injection of the
femoropatellar joint of the horse. Equine Vet J 1992;24:399-401.
Murphy JM, Fink DJ, Hunziker EB, Barry FP. Stem cell therapy in a caprine model of osteoarthritis. Arthritis
Rheum. 2003 Dec;48(12):3464-74.
Ortved KF, Nixon AJ, Mohammed HO, et al: Treatment of subchondral cystic lesions of the medial femoral
condyle of mature horses with growth factor enhanced chondrocyte grafts: a retrospective study of 49 cases.
Equine Vet J 2012;44:606–613
Reeves MJ, Trotter FW, Kainer RA. Anatomical and functional communications between the synovial sacs of
the equine stifle joint. Equine Vet J 1991;23:215-218.
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February
2016
East
London
Convention
Centre,
East
London,
South
Africa
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