Page 365 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

340 CHAPTER 1

VetBooks.ir Management most breeds, Friesian horses appear to be particu-
larly predisposed. The reason for this is unclear.
Conservative treatment with rest and controlled
Septic (infectious) ISL desmopathy with osteitis of
exercise as for SL branch desmitis is advocated.
the axial border of the PSB is associated with either
Prognosis infectious arthritis or tenosynovitis and is a serious
The results are variable and there may be persis- complication of these conditions.
tent or recurrent lameness. SDSL injuries carry a
guarded prognosis, although there have only been Clinical presentation
few reports and there is insufficient data to make this Lameness is usually acute and severe, and this
a general rule. Incidental observation of old lesions author has not encountered clinically silent radio-
in rare cases suggests that complete resolution of the graphic or ultrasonographic signs of severe des-
lameness is possible, despite persistence of an abnor- mopathy. However, discrete entheseopathy of the
mal ligament on ultrasonography. axial borders of the PSBs (without erosions) may
be occasionally encountered as an incidental find-
INTERSESAMOIDEAN ing on survey radiographs in horses with no overt
LIGAMENT DESMOPATHY clinical signs.

Definition/overview Differential diagnosis
The intersesamoidean ligament (ISL) is a strong, Any condition related to the metacarpo/metatarso-
short ligament that joins together the two PSBs. phalangeal joint or the DFT sheath.
With transversely oriented fibres, it is actually
part of the palmar/plantar fetlock joint capsule. Diagnosis
Its dorsal aspect is lined by synovial membrane; Clinical examination
its palmar aspect is continuous with the proximal Lameness should be referred to pain arising from
scutum (i.e. fibrocartilage that covers the PSB and the metacarpophalangeal joint area, with variable
forms a gliding surface for the DDFT). response to fetlock flexion and marked improvement
Injury to this strong ligament is rare but can after distal metacarpal/metatarsal analgesia (‘lower
lead to severe, persistent lameness. It is difficult to four-point or six-point nerve block’). It may be par-
diagnose and very few reports have been published. tially or totally alleviated by intrasynovial analgesia
A post-mortem study revealed a prevalence of ISL of the fetlock joint or digital sheath.
injuries of 26%, most of which showed no associ-
ated clinical signs. These lesions were visible on Radiography
survey fetlock radiographs. In the author’s experi- Typically, good-quality dorsopalmar/ dorsoplantar
ence, radiographic evidence of ISL desmopathy radiographs will show remodelling of the axial
is extremely rare and the findings in this German borders of the PSBs with irregular erosions,
study may relate to a specific case load. fragmentation and mineralisation within the
intersesamoidean space (see Chapter 1.4, Figs. 1.236,
Aetiology/pathophysiology 1.237). Several dorsopalmar/ dorsoplantar projec-
The aetiology is unclear but is probably due to tions at different angles may help to better image
mechanical overload. The ISL is submitted to tre- the lesions. Avulsion fractures are usually associ-
mendous tensile forces, spreading the two PSBs ated with a longitudinal radiolucent line separat-
apart as the horse puts weight on the limb, via pres- ing a thin fragment on the axial surface of the PSB.
sure from the flexor tendons and the sagittal groove There may occasionally be visible widening of the
of the distal metacarpus/metatarsus. The latter space between the two PSBs. Infectious osteitis is
also creates torsional/shearing forces when weight characterised by marked, irregular lysis of the axial
bearing is asymmetrical. Although described in border of one or both PSBs, which may extend to