Page 325 - Canine Lameness

18.5 ­rct al egy ofctrf oo o ralarorro ron o 297

cruciate ligament pathology, once the tendon is weakened, minor trauma may cause acute exacer-
bation of lameness, which may be the first time that owners notice the abnormality.
Palpation of the entire CCT should be performed as described for cases with traumatic rupture.
It is essential to evaluate the other pelvic limb, since approximately 50% of cases are bilaterally
affected (Gamble et al. 2017). Underlying conditions such as Cushing’s disease and long-term ster-
oid and perhaps enrofloxacin (Lim et al. 2008) administration should be excluded.
Radiographs may show soft tissue swelling of the affected region (most commonly at the inser-
tion at the tuber calcanei), avulsion fragments, enthesopathy, or dystrophic calcification of the
tendon (Figure 18.8). The latter can be difficult to differentiate from an avulsion fragment, but with
dystrophic calcification, the tuber calcanei does not show a defect, and multiple foci of calcifica-
tion are often present. Ultrasonography is more sensitive than palpation or radiography and facili-
tates the identification of the specific tendons involved as well as the severity of the disruption TARSAL REGION
(Gamble et al. 2017). Ultrasonography therefore provides a simple, noninvasive, and cost-effective
method to evaluate the CCT.
There is a lack of peer-reviewed literature comparing available treatment options for this disease.
Surgical repair is generally recommended (Corr et al. 2010), but treatment with orthotics com-
bined with surgery or as a sole treatment has also been reported (Wallace 2012; Mich 2014).

18.5.3 Luxation of the Superficial Digital Flexor Tendon

Luxation of the SDFT is an infrequent condition that results in pelvic limb lameness due to dis-
placement of the tendon at the level of the calcaneus. The tendon generally luxates laterally due to
disruption of the medial retinaculum. The condition may be triggered by mild trauma, although a
traumatic event is not always observed. While osseous abnormalities of the calcaneus have been
proposed as the underlying etiology (Reinke and Mughannam 1994), a weaker attachment on the
medial side has been suggested as the main cause by Kara (1998). Shetland Sheepdogs appear to be
predisposed (Solanti et al. 2002) but other breeds are also affected.
Patients show varying degrees of lameness depending on the acuity of the condition. Initially
dogs may be non-weight-bearing on the limb, but most dogs have a low-grade lameness at the
time of presentation. Some dogs show a skipping gait as is observed with patellar luxations.
Swelling will be palpable and sometimes visible over the tip of the calcaneus. In some cases,
bursitis is severe, causing the swelling to be fluctuant. In relatively acute cases, the diagnosis is
made by a popping sensation as the tendon displaces (Video 18.2). The SDF may become fixed in
its displaced condition when the condition is chronic. In this case, there is no palpable popping,
but the focal swelling remains. Radiographs should be taken to rule out other osseous pathology.
Luxation of the SDFT may be confused with Type IIc Achilles tendinopathy, and ultrasonogra-
phy can be used to confirm the integrity of the CCT, which differentiates this condition from all
other CCT pathologies. Ultrasonography is also useful for identifying chronic SDF luxations.
Surgical imbrication of the torn or stretched retinaculum usually gives good results, except in
some chronically affected dogs.

Video 18.2

Superficial digital flexor tendon luxation.