Equine vet. J. (2006) 38 (4) 375-378
Oral hyaluronan gel reduces post operative tarsocrural
effusion in the yearling Thoroughbred
Rood and Riddle Equine Hospital, PO Box 12070, Lexington,
Kentucky, 40580-2070, USA. †Department of Statistics, University of
Lexington, Kentucky 40506-0027, USA.
Keywords: horse; thoroughbred; joint effusion; oral hyaluronan;
osteochondritis dissecans; hyaluronan; arthroscopic; tarsocrural
administration. The efficacy of intra-articular and i.v. use
has been evaluated but the oral route has yet to be examined.
Objectives: To determine the effect of oral hyaluronan gel
on joint effusion following arthroscopic surgery for
osteochondritis dissecans (OCD) of the tarsocrural joint of
yearling Thoroughbreds.
Methods: Forty-eight yearlings diagnosed with unilateral or
bilateral osteochondritis dessicans (OCD) of the tarsus were
arbitrarily chosen prior to arthroscopic surgery. The
yearlings were included only if they had mild or no synovial
effusion pre-surgery. Twenty-four of the yearlings (27 joints)
were treated with 100 mg of HA orally for 30 days post
operatively and 24 (30 joints) with a placebo orally for
30 days. At 30 days post operation, a blinded examiner
scored the effusion of the dorsomedial tarsocrural joint
individually using a scale of 0 to 5 (0 = no effusion, 1 = barely
palpable effusion, 2 = palpable effusion [without plantar
effusion], 3 = golf ball sized effusion with plantar effusion,
4 = tennis ball sized effusion with plantar effusion,
5 = > tennis ball sized effusion with plantar effusion). Half
grades were allowed and OCD lesion sizes and locations
were compared.
Results: A total of 57 joints were examined, of which 33 had
OCD of the distal intermediate ridge of the tibia, 19 OCD of
the distal lateral trochlear ridge of the talus and 5 OCD of
the medial malleolus. The mean 30 day effusion score of the
HA treated group (27 joints) was 0.67 while the mean of the
30 day placebo group (30 joints) was 2.05 (P≤0.0001).
Similar results were noted when comparing treated vs.
placebo for each lesion location as well as for lesion sizes.
Conclusions and potential relevance: Oral preparations of
hyaluronan are being used to treat joint disease in horse.
Anecdotal reports supporting the efficacy of these
preparations already exist. This study provides objective
evidence that oral HA reduces joint effusion post operatively
following the arthroscopic removal of an OCD lesion in the
tarsocrural joint.
Many Thoroughbred yearlings routinely undergo survey
radiographs at age 10–12 months to detect the presence of bone
abnormalities that may affect athletic performance. Many
surgically correctable lesions are found during these surveys.
Most lesions are found prior to the development of synovial
effusion, however a few present clinically with lameness and/or
joint effusion. A common surgical lesion is osteochondritis
dissecans (OCD), which is most frequently located in
the stifle (femoropatellar), hock (tarsocrural), fetlock,
(metacarpophalangeal and metatarsophalangeal) and shoulder
(scapulohumeral) joints. Osteochondritis dissecans is classified as
a growth disorder within the developmental orthopedic disease
complex and is considered a manifestation of osteochondrosis
(Beeman and McIlwraith 1986; MacIlwraith 1993).
Osteochondritis dissecans of the tarsocrural joint is found most
frequently in Standardbreds, but has been documented in many
other breeds including the Thoroughbred (McIlwraith et al. 1991).
The most common sites involved, in order of decreasing
frequency are the distal intermediate ridge of the tibia, distal
lateral trochlear ridge of the talus and medial malleolus of the
distal tibia.
Intra-articular hyaluronan (HA) has been used in the horse for
the past thirty years (Rydell et al. 1970). More recently, i.v.
administration has been shown to be effective in reducing the
degree of lameness associated with joint disease (Kawcak et al.
1997). Oral HA formulated for the horse has been available for the
past 4 years and anecdotal reports have suggested that its use has
been effective in treating synovial effusion and lameness.
Hyaluronan is a glycosaminoglycan ubiquitous in all
vertebrates and is an integral component of both synovial fluid
and articular cartilage in normal synovial joints. Hyaluronan
provides the viscoelasticity property to the synovial fluid and is
responsible for the boundary lubrication of the synovial
membrane and articular cartilage (Howard and McIlwraith 1996).
Recent studies on HA have examined normal turnover and
metabolism (Fraser and Laurent 1989), changes in lymphatic flow
(Reed 1992), absorption through skin (Brown et al. 1999),
changes in blood levels in various diseased states (Engstrom-
Laurent 1989) and immunomodulary effects (Pirnazar et al.
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