Advances in the Canine Cranial Cruciate Ligament, 2nd edition

Epidemiology of Cruciate Ligament Rupture 111

Table 14.1 Potential risk factors for cruciate ligament rupture in dogs based on current evidence.

Category Potential risk factors

Age 4–8 years

Reproductive status Neutered (before 1 year may increase further)

Breed Newfoundland

Rottweiler

Labrador Retriever

Bulldog

Boxer

Chow Chow

American Staffordshire Terrier

Weight >22 kg

Body condition Overweight or obese

Intended function Unknown

Stifle anatomy Narrow intercondylar notch

Excessive tibial plateau angle (degree varies among

reports,> 28 ◦,> 32 ◦,> 35 ◦)

Relatively small proximal tibial craniocaudal width

Cranial angulation of the proximal tibia

Distal femoral torsion

Schwandtet al. 2006; Guerreroet al. 2007; Cabr-
eraet al. 2008; Inauenet al. 2009; Ragetlyet al.
2011; Fulleret al. 2014b; Hayneset al. 2015).
Anatomic factors that are associated with a pre-
disposition to CR include a narrow intercondy-
lar notch, excessive or pathologic (i.e., outside
the 95% confidence intervals for the population)
tibial plateau angle, a relatively small proxi-
mal tibial width, cranial angulation of the proxi-
mal tibia, and distal femoral torsion (Table 14.1).
While a great number of studies have focused
on the effects of tibial plateau angle and patellar
tendon angle, no study has definitively shown
either of these as significant risk factors for CR
in dogs. Theories andex vivoresearch have
suggested that increased CrCL strain and an
increased shear component of total joint force
when each of these angles is considered high
based on reference ranges in dogs (Warzee
et al. 2001; Reif & Probst 2003; Kowaleskiet al.
2005; Shahar & Milgram 2006; Apeltet al. 2007;
Duerret al. 2007; Kimet al. 2008; Kipferet al.
2008; Hayneset al. 2015). One study reported
that a multiple logistic regression model using
the combination of tibial plateau angle and
femoral anteversion angle was able to discrim-
inate between case and control limbs with an
area under the ROC curve of 96% (Ragetly

et al. 2011). This suggested that a multivariate

approach may provide further insight into the

effect of tibial morphology as a risk factor. Other

studies have reported no significant effect of

proximal tibial morphology on the risk of CrCL

rupture (Wilkeet al. 2002; Reif & Probst 2003;

Guastellaet al. 2008; Fulleret al. 2014a). The

wide spectrum of results supporting or negat-

ing the effect of conformational variables on

the risk of CR provides further support for the

overall complexity of the condition. While bony

conformation may contribute to CR in some

way, there remains no definitive evidence that

it is a primary causal factor.

Bilateral CrCL rupture

Perhaps one of the greatest risk factors for

developing a CR is having already been diag-

nosed with the condition. The incidence of

bilateral ruptures diagnosed on initial clinical

presentation is in the range of 11% to 17% (de

Bruinet al. 2007; Cabreraet al. 2008; Buoteet al.

2009). The incidence of contralateral rupture

after initial diagnosis is between 22% and

54% (de Bruinet al. 2007; Cabreraet al. 2008;

Buoteet al. 2009; Griersonet al. 2011; Fuller