Page 323 - Canine Lameness

18.5 ­rct al egy ofctrf oo o ralarorro ron o 295

Box 18.1 Grading of Pathology of the CCT (Meutstege 1993)
1) Type I = complete rupture
(a) Stance = plantigrade

2) Type II = partial rupture
(a) Stance = slightly increased hock flexion
i) Type IIa affects the musculotendinous junction
ii) Type IIb is similar to Type I but has an intact paratenon and therefore dogs are not
completely plantigrade
iii) Type IIc affects the GT only (with intact SDFT) resulting in increased flexor tension
on the digits (“crab claw”)
3) Type III = tendinosis only TARSAL REGION
(a) Stance = normal

and digit flexion. The conjoined tendon inserts medially on the tuber calcanei and plays a minor
role in tarsal extension.
A classification system (Box 18.1) that differentiates conditions causing structural changes of the
CCT based on location and severity of injury has been described (Meutstege 1993). An important
distinction should be made between acute, traumatic (e.g. Type I) rupture and a chronic, degenera-
tive (e.g. Type IIc) process, since the treatment differs substantially (Figure 18.8). Another rarely
encountered condition is luxation of the SDFT. Pathology affecting the origin of the gastrocnemius
muscle (e.g. avulsion and myotendinopathy) is also rare and discussed in Chapter 19.

18.5.1 Traumatic Rupture

Traumatic rupture may occur at any level of the CCT, with the musculotendinous junction and
insertion most commonly affected. Disruption may involve any of the five structures of the CCT but
most commonly affects all tendons (i.e. Type I or Type IIb injuries). Border Collies frequently sus-
tain these injuries (Corr et al. 2010), but obviously any dog may suffer from trauma. Lacerations may
be due to external trauma (e.g. sharp lacerations) or occur during exercising; the injury may be open
or closed. While open injuries simplify establishing a diagnosis based on the visible disruption of the
skin (and visibly disrupted tendon in some cases), closed injuries are diagnosed based on palpation
of the tendon and the associated plantigrade stance (i.e. the entire pes touching the ground;
Figure 18.8). However, recent literature (Corr et al. 2010; Gamble et al. 2017) has shown that plan-
tigrade stance (note that plantigrade stance was defined more loosely as an increased flexion angle
by these authors) does not always predict the specific tendons affected but is more likely to be pre-
sent in patients with injury at the musculotendinous junction. Palpation of a gap between the rup-
tured ends of the tendon is facilitated by stretching the CCT, which is accomplished by extending
the stifle and flexing the tarsus (Figure 18.4). The entire CCT should be palpated, since diffuse inju-
ries or injuries at multiple sites have been reported. Radiographs should be performed to rule out
any fractures or other osseous abnormalities. Ultrasonography can be utilized to determine the
exact location and extent of CCT disruption, and a grading system for this has been reported
(Gamble et al. 2017). As with palpation of the tendon, dynamic evaluation while the CCT is stretched
can help identify pathology. Treatment of acute injuries generally involves surgical apposition of the
tendon ends followed by some form of external or internal support while the tendon is healing.