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  Discussion on Osteoarthritis of the talocalcaneal joint
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DrO

Posted on Wednesday, May 25, 2005 - 9:57 am:

All the news about hock lameness (see yesterdays post) is not good. A previously poorly defined cause of hock lameness has been better defined and may be more common than previously thought. When you read about arthritis in the hock you would think there are just 4 joints but that is not so. There is a fifth isolated joint of some size: the talocalcaneal joint. This joint lies between the bone that sticks out prominently behind the hock, the calcaneous, and the internal talus, which is the bone that up the hinge joint of the hock. Unlike the hinge joint the talocalcaneal joint is fixed and does not contribute substantially to the motion of the hock.

This joint can occasionally be effected by osteoarthritis. The problem is that it is hard to localize pain to this joint using diagnostic blocks and the prognosis for return to full soundness is poor. TO arthritis should be suspected when a moderate to severe lameness has come up quickly that refers to the hock. A good lateral radiograph will reveal degenerative changes in the TO joint which should then put heavy suspicion on the joint.


Equine Vet J. 2005 Mar;37(2):166-71.
Osteoarthritis of the talocalcaneal joint in 18 horses.

Smith RK, Dyson SJ, Schramme MC, Head MJ, Payne RJ, Platt D, Walmsley J.

Department of Veterinary Clinical Sciences, Royal Veterinary College, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK.

REASONS FOR PERFORMING STUDY: Talocalcaneal osteoarthritis (TO) is an uncommon cause of moderate to severe hindlimb lameness, on which only isolated case reports have been published to date. OBJECTIVES: To review the clinical features of TO and determine optimal methods for diagnosis, management and prognosis. METHODS: The case records from 4 referral centres of 18 horses showing hindlimb lameness considered, as a result of clinical investigation, to be caused by TO, were reviewed. RESULTS: TO affected mature sports and pleasure horses (age 7-16 years) and caused moderate to severe lameness, usually of sudden onset with no obvious inciting cause. There were few localising signs, other than worsening of lameness by hock flexion. Tarsocrural joint analgesia produced improvement in lameness in 6/11 horses (55%) and perineural analgesia of the tibial and fibular nerves complete soundness in 6/14 horses (43%) in which it was performed; 7/14 horses (50%) showed a further substantial improvement. Radiological findings included subchondral bone lysis and sclerosis and irregular joint space width, seen most obviously in a lateromedial view. Nuclear scintigraphy revealed marked uptake of radiopharmaceutical predominantly plantaromedially in the region of the talus in the 7 horses in which it was performed. Fourteen horses were treated conservatively with box- or pasture-rest, with or without intra-articular corticosteroids, hyaluronic acid or polysulphated glycosaminoglycan, and all remained lame. Intra-articular corticosteroids appeared to have no effect in any horse. Of 10 horses receiving conservative management only, 6 were subjected to euthanasia, 3 were retired and 1 remained in light work, but was still lame. Two horses treated by either partial tibial and fibular neurectomy or subchondral forage failed to regain soundness and were retired. Six horses were treated by surgical arthrodesis of the talocalcaneal joint with 2 or three 5.5 mm AO screws introduced obliquely across the joint from the plantarolateral aspect of the calcaneus, which resulted in improvement in lameness in all cases. CONCLUSIONS: Osteoarthritis of the talocalcaneal joint causes acute onset severe lameness, but clinical findings and diagnostic analgesia often fail to identify precisely the site of pain. Consistent radiographic changes suggested TO was contributing to the lameness and this diagnosis was supported by nuclear scintigraphy. The poor success of conservative treatment (including intra-articular medication) suggests that surgical arthrodesis is the treatment of choice, although the prognosis is still poor for a return to full soundness. POTENTIAL RELEVANCE: The clinical features described should facilitate more accurate diagnosis and prognosis. A novel surgical treatment is described which appears to offer significant improvement in the lameness. Further work is necessary to determine the causes of this condition and more effective management.
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