Page 70 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.2 The foal and developing animal 45

VetBooks.ir LATERAL LUXATION OF THE PATELLA hocks in extreme flexion (Fig. 1.79). Lateromedial,
caudocranial and flexed skyline radiographs are use-
Lateral luxation of the patella is a rare condition
repair can be attempted in unilateral cases where
in most breeds, but it is commonly seen in min- ful to confirm the condition (Fig. 1.80). Surgical
iature Shetlands and other small breeds. It can be underlying bony development is adequate. The lat-
uni- or bilateral. A hereditary mode of transmission eral patellar retinaculum is incised and the medial
involving a monogenic autosomal recessive gene in patellar retinaculum and fascia imbricated. Some
Shetland ponies is cited. The condition is usually surgeons also perform a trochleoplasty. The progno-
due to hypoplasia of the lateral trochlear ridge of the sis is guarded in unilateral cases and appears guarded
femur (Fig. 1.78). Bilaterally affected foals typically to poor in bilateral cases, although miniature breeds
present with a ‘squatting’ stance, with hips, stifles and can cope quite well with milder bilateral deformities.

1.78 1.80

Fig. 1.78 Post-mortem specimen of the distal
femur of a foal that presented with bilateral patellar
luxation. Note the rather flattened hypoplastic
lateral trochlear ridge (on the left) and shallow
trochlear groove.

1.79

Fig. 1.80 Craniocaudal radiograph of the stifle joint
of the foal in 1.79 showing the patella luxated laterally
outside the plane of the femur (arrow).

Fig. 1.79 Typical squatting stance of a foal with
bilateral patellar luxation.