Page 211 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

186 CHAPTER 1

VetBooks.ir medical and surgical, have been described, suggest- deep peroneal nerve supplying the small tarsal joints
can be performed and carries a success rate of 65%.
ing that none provide complete cure in all cases.
Determining the treatment is dependent on the
eral anaesthetic time, extensive soft-tissue dissection
clinical and radiographic findings, use of the horse, The technique, however, requires a prolonged gen-
response to previous treatments and financial con- and is only effective for 1–2 years because of rein-
straints. Horses with mild or no radiographic change nervation. It is therefore rarely employed.
are best treated with intra-articular medication and
a systemic NSAID such as phenylbutazone. Either Prognosis
triamcinolone (4–10 mg/joint up to a total dose of The prognosis varies from guarded to poor depend-
18–20 mg in a 500 kg horse) or methylprednisolone ing on the joint(s) affected, the severity and chro-
acetate (20–40 mg/joint) can be used with or with- nicity of articular changes, secondary causes of
out hyaluronan. This treatment invariably produces lameness or back pain, the type of work carried
an improvement in lameness and frequently results out by the horse and response to treatment. Those
in soundness; however, many horses suffer recurrent horses that show a good response to intra-articular
lameness after a variable period of time. Prolonged medication will often continue in work for some
rest is not beneficial, and these horses should be kept time with the aid of ongoing medication. Those that
in a box for 24–72 hours and then gradually returned show a poor response to intra-articular medication
to work. The biphosphonate drugs tiludronate (i/v) present a greater challenge and are the group most
and clodronate (i/m) are used for the treatment of likely to require arthrodesis.
distal tarsal OA with studies suggesting mild but
positive results in some cases. A change in work pro- TARSOCRURAL SYNOVITIS (BOG SPAVIN)
gramme, either in type or degree, can be very useful
in decreasing the degree of lameness. Severe radio- Definition/overview
graphic changes or failure to respond to conservative The term bog spavin has been used traditionally
management justifies more radical intervention. to describe excessive distension of the tarsocural
Surgical arthrodesis can be performed in a num- (TC) joint with synovial fluid subsequent to acute or
ber of ways, including simple drilling across the joint chronic synovitis.
(3–6 tracts with a 3.2–4.5 mm drill bit), with or with-
out the addition of cancellous bone graft after drill- Aetiology/pathophysiology
ing, T-plates and 4 cm long, 9 mm diameter Bagby The most defined cause of bog spavin includes vari-
baskets filled with cancellous bone placed across able manifestations of OCD. Lesions are recorded in
the joints. The most common technique involves several different anatomical sites and with different
the drilling of three 3.2–4.5 mm tracts across the presentations. Other well-defined causes include OA,
affected joints. The prognosis for soundness with trauma, sepsis, haemarthrosis and intra-articular
these techniques is 60–75%. Chemical arthrodesis fractures. Mineral or vitamin deficiencies have also
was achieved in the past by injecting a caustic agent, been implicated without clear scientific evidence.
monoiodoacetic acid, into the affected joints, usu- Horses can suffer distension of the joint without clear
ally under general anaesthesia, with a success rate of lameness or inciting pathology, sometimes referred
40–80%. More recently, 70% ethanol has been used to as idiopathic synovitis. TC joint effusion can also
with more successful results. Whatever technique be a manifestation of continuous cartilage micro-
is used, it should be noted that ankylosis can take trauma as a result of poor conformation, particularly
9–18 months. Cutting the cunean tendon is thought straight hocks. TC joint effusion can be more evi-
to reduce pressure over the medial aspect of the dis- dent after a period of box rest, particularly in older,
tal tarsal joints but is less commonly used as a sole well used jumping and dressage horses; however, this
procedure as it is unlikely to restore soundness in should disappear once exercise is initiated. Joint cap-
the long term. Localised partial neurectomy of the sule sprain, with or without damage to the collateral
branches of the tibial nerve and neurectomy of the ligaments, may also cause TC effusion.