fusion could have occurred. Comparison of laser, MIA and drilled arthrodesis
in horses without abnormalities of the distal tarsal joints suggested that laser
resulted in more extensive chondrocyte death although the effect appeared
focal, while drilled arthrodesis resulted in more evidence of joint space
narrowing and fusion (Scruton et al. 2005). Experimental laser treatment of
normal distal tarsal joints produced minimal localized cartilage necrosis and
the defects eventually filled with mostly fibrous tissue (Scruton et al. 2005;
Zubrod et al. 2005). The authors concluded that ankylosis occurred earlier
after drilling of the distal tarsal joints than after laser-facilitated arthrodesis,
although clinically affected horses may respond differently than the normal
horses in the study. In a similar study comparing the effects of MIA, surgical
drilling and laser on distal tarsal joints without osteoarthritis, Zubrod et al.
(2005) concluded that surgical drilling and MIA resulted in more bone bridging
of the distal 2 tarsal joints, than laser surgery. However, laser surgery
seemingly caused less pain and discomfort to horses in the immediate
postoperative period. It is possible that the mechanism of action of laser lies in
elimination of sensation in the fibrous joint capsule through boiling of synovial
fluid. The potential advantage of laser treatment compared to surgical drilling
of the joint spaces is a more rapid return to activity. Horses treated with the
laser returned to normal activity in a few weeks compared to 6 to 17 months
after surgical drilling.
Some prominent clinicians have challenged the concept that joint fusion is
desirable, because pain should disappear. Their reservation stems from the
realization that the distal tarsal joints are responsible for the dissipation of the
twisting or torsional forces and shear stress in the distal tarsal area. It is
claimed that fusion of these joints concentrates torsional forces, and stress
fracture of the central or the third tarsal bones may occur or OA of the
proximal intertarsal jointmay develop. Even so, it begs the question how horse
that have become refractory to all other treatments should be managed if they
can no longer perform adequately.
Subchondral fenestration
Elevated intramedullary bone pressure has been proposed as a source of
lameness in horses with OA; pressure in horses with diseased tarsi was
approximately 50% higher than that from normal horses (Sonnichsen and
Svalastoga 1985). A modified drilling procedure coursing obliquely distad to
proximad through MT3, DIT, and TMT joints terminating within the central
tarsal bone has been described (Jansson 1995). Although it is not possible to
separate the effect of medullary decompression from immobilization due to
bone healing across the drill sites, this technique was reported to be as
effective as other techniques described. Although this technique has been
shown to reduce intraosseous pressures effectively, it has proved
disappointing in alleviating lameness in my experience.
Partial neurectomy of the Tibial and Deep Peroneal Nerves
The results of an improved method of partial tibial and deep peroneal
neurectomy were reported in 24 Warmblood horses (Imschoot et al. 1990).
Complete tibial and peroneal neurectomy as previously reported (Dyson 1996)
15-‐18
February
2016
East
London
Convention
Centre,
East
London,
South
Africa
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