Chapter 14 Disorders of the Pelvic Limb: Diagnosis and Treatment 361Additional treatment options are limited
for chronic or refractory cases. Eighteen dogs
with gracilis or semitendinosus myopathy
were treated with various methods (Lewis et al.,
1997). Eight received medical management
either alone or prior to surgery. There was no
apparent response. Fifteen dogs were treated
with one or more surgical procedures. Lameness
resolved following transection, partial excision,
or complete resection of the affected muscle.
However, it recurred 6 weeks to 5 months fol
lowing surgery. Adjunctive medical treatment
did not change the outcome. Myectomy of
the entire gracilis muscle is no more success
ful as the gait abnormality may return within
3–5 months due to semitendinosus involvement
(Lewis et al., 1997).
Hip dysplasia
Pathophysiology
Hip dysplasia (HD) can be defined as abnor
mal development of the hip joint, resulting in
coxofemoral laxity due to decreased coverage
of the femoral head by the acetabulum and
ineffective soft tissue stabilization of the joint
(Demko & McLaughlin, 2005; Lopez, 2012).
Abnormal kinematics result in joint capsule
stretching, cartilage erosion, subchondral bone
fracture, periarticular fibrosis, and new bone
formation (Dassler, 2003). Disease progression
results in degenerative and inflammatory
changes characteristic of osteoarthritis (OA)
(Dassler, 2003).
Hip dysplasia is the most common develop
mental orthopedic condition in dogs and is
highly breed dependent (Witsberger et al., 2008;
Smith et al., 2012). Despite attempts at eradica
tion of the condition through selective breeding
programs, the prevalence of HD remains very
high within certain breeds (Coopman et al.,
2008; Witsberger et al., 2008; Smith et al., 2012).
A review of over 1.2 million dogs between 1964
and 2003 reported the prevalence and risk fac
tors for HD in over 50 breeds (Witsberger et al.,
2008). Newfoundlands, Rottweilers, German
Shepherd Dogs, and retrievers are among the
most commonly affected breeds, with preva
lences up to 17% (Witsberger et al., 2008). Smith
and colleagues (2012) followed a colony of
Labrador Retrievers over their life span and
found that despite breeding for an expected
HD incidence between 26% and 51%, in fact
98% of the dogs had evidence of HD at the time
of death. These studies highlight the fact that
HD is a complex condition with many factors
involved in the development, progression, and
recognition of the disease.
Hip dysplasia is a polygenic, heritable condi
tion, in which the phenotypic expression can be
influenced by reproductive status, age, body
condition and conformation, diet, and other
environmental factors (Spain et al., 2004; Demko
& McLaughlin, 2005; Witsberger et al., 2008;
Smith et al., 2012). Castrated male dogs are
significantly more likely to be affected by HD,
and an association has been shown between
gonadectomy at <5 months of age and the
development of HD in both males and females
(Spain et al., 2004; Witsberger et al., 2008).
Kealy, Smith and others found that the devel
opment and progression of HD was signifi
cantly delayed or decreased in dogs maintained
at a lean body condition through caloric restric
tion compared to litter‐matched pairs of a
higher body condition score (Kealy et al., 2002;
Smith et al., 2012). When all dogs in this study
were pooled, a linear relationship was seen
between age and prevalence of HD. A conclu
sion of this study was that selecting breeding
dogs based on phenotype (young age, lean
body condition) does not ensure elimination of
the HD genotype (Smith et al., 2012).DiagnosisDogs with HD often show clinical signs follow
ing a bimodal curve: 4 months to 3–4 years and
>7 years of age (Smith et al., 2012; Witsberger
et al., 2008). Puppies and young dogs with HD
present with a history of decreased activity
or reluctance to jump or climb stairs, bunny‐
hopping gait, underdeveloped pelvic limbs
with a narrow stance, and pain or vocalization
with manipulation (Dassler, 2003; Demko &
McLaughlin, 2005). Mature dogs with symp
toms related to OA of the hips show varying
degrees of lameness that is worse after rest and
heavy exercise, reluctance to jump, pelvic limb
atrophy, and behavior changes associated with
pain (Demko & McLaughlin, 2005).