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Chapter 6. PELVIC
LIMB (DOG)
Identify the following features in the
skeleton and locate them in live dog and in radiographs .
6.1
SKELETON:
- Os coxae:
- crest of ilium, position of
sacroiliac joint; shaft (body) of ilium; acetabulum: acetabular
notch and; acetabular fossa; tuber ischii; shaft (body) of ischium
; ischiatic spine.
-
- Femur:
- head (articular): fovea capitis
(for attachment of ligament) neck trochanter major; trochanteric
ridge; trochanteric fossa; trochanter minor; condyles:
intercondylar fossa; epicondyles trochlea
-
- Patella
- Fibula:
- head or proximal extremity,
shaft; distal extremity (lateral malleolus)
-
- Tibia
- condyles: intercondylar fossa;
popliteal notch; tuberosity; crest; medial malleolus.
-
- Pes:
- Tarsus:
- talus; central (sometimes
dislocated or; fractured in greyhounds) TI, II, III, &
IV.
- Metatarsals, digits, sesamoids
-- similar to corresponding structures of manus.
6.2
MUSCLES
- A more complete knowledge of
position of muscles in dog is required than in horse because of
greater frequency of remediable dislocations and fracture in dog.
For structures below tarsus, see thoracic limb and merely
substitute metatarsal for metacarpal, plantar for palmar,
etc.
6.3
REDUCTION OF FRACTURES:
- 6.3.1 SHAFT OF FEMUR AND
TIBIA
-
- 6.3.1.1 Closed
manipulation (i.e., with minimal incision of skin a no
reflection of tissues for the purpose of inserting an
intramedullary pin).
-
- Femur:
- Insert pin through skin and
muscle, and slide along medial surface of trochanter major to
trochanteric fossa. Reverse nailing is more common because of
difficulty in aligning pin through trochanteric fossa. Curve of
distal extremity precludes complete insertion of intramedullary
pin. Sciatic N. close to trochanteric fossa.
-
- Tibia:
- Through skin and along medial
border of patellar lig. to tuberosity of tibia which is entered
just cranial to medial meniscus. An alternative: a point about
halfway between tuberosity of tibia and medial condyle and 1/4"
below this point.
-
- 6.3.1.2 Open Reduction
i.e., involving skin incision; (sometimes quite
- extensive) and reflection of
tissue.
-
- Femur:
- lateral approach:- Trochanter
major to lateral epicondyle. Cut fascia lata cranial to edge of
biceps. Reach bone between biceps and vastus lateralis. In
fracture of distal extremity at, or close to, epiphyseal line
(very common), rush pins may be inserted on either side of
trochlea. Approaches, lateral or medial: (The flexor muscles of
stifle displace the distal epiphysis backwards, and, cortex being
thin here, intramedullary pinning is unsuitable.)
-
- Tibia:
- Craniomedial approach. For open
reduction and for plating, remember position of saphenous vessels
and Nn. (m. tibialis cranialis is in front of bone, m. deep
digital flexor behind, and proximally is the insertion of m.
popliteus and that of m. semitendinosus.)
-
- 6.3.2 JOINTS
- 6.3.2.1 The sacroiliac
joint: is an articulation of stability rather than mobility.
The ilia articulate with the sacrum by means of rough surfaces
covered by fibrocartilage, forming a joint which does not easily
disarticulate. Around the periphery of the articular areas, bands
of strong collagenous tissue reinforce the
fibrocartilage.
- The sacrotuberous ligament
(modified sacrosciatic ligament of large animals) runs from the
last sacral and first coccygeal vertebrae to the tuber ischii.
Several muscles are attached to it.
-
- 6.3.2.2 The hip joint:
(coxofemoral joint)
- Is an enarthrodial joint whose
main movements are flexion and extension; but in the dog its range
of movement is much more considerable than in large animals.
Considerably more adduction, abduction, circumduction, and
rotation are possible in this species. The head of the femur is
more than hemispherical and the acetabulum is wide and
deep.
- The ligament of the head of the
femur:
- attachments:- fossa acetabuli
and fovea capitis. The ligament is quite strong, but its length
permits a wide range of movement. The joint capsule, attached on
the one hand close to the acetabular margin and on the other to
the neck of the femur a short distance from the articular margin
of the head. The capsule is roomy but possesses no pouches, and
its fibrous tunic has no appreciable thickenings . The depth of
the acetabulum is slightly increased by the fibrocartilage which
surrounds its rim, and this bridges the acetabular notch as the
transverse acetabular ligament, helping to prevent
ventromedial dislocation of the joint. The great range of movement
allowed by the hip joint not only renders it liable to injury but
is also responsible for subjecting the more distal joints, and
especially the stifle, to strain.
- Conformation of the normal hip
joints should be studied radiographically and the normal picture
imprinted on your memory before you encounter the abnormal in the
form of hip dysplasia.
-
- 6.3.2.3 Coxofemoral luxation
:
- Is said to be the most common
dislocation met with in small animal practice. Nevertheless, the
depth of the acetabulum, in the dog, is such that recent
dislocation (without damage to the acetabulum or head or neck of
the femur) if once reduced correctly is said to remain in position
in spite of ligamentous rupture and with no supportive treatment.
The bones forming the joint are of course held fairly firmly in
position by the muscles which arise and/or insert close to the
joint.
- It is said that trauma which
would produce coxofemoral luxation in an older dog will, however,
fracture the neck or cause epiphyseal separation in a young dog
(under one year).
- Dislocation of the head of the
femur is nearly always dorsocranial; occasionally dorsally only,
and rarely ventrocaudally.
- Intracapsular fractures are
more serious than extracapsular ones because, in the former, blood
supply to femoral head affected, and in the latter retained.
Vessels in the ligament of the head of the femur supply only a
small area of the head.
-
- 6.3.2.4 Craniolateral
approach to hip joint and femoral neck.
- Incision dorsal and cranial to
greater trochanter and through m. tensor fasciae latae. Joint
approached by a muscle split incision through triangle formed by
rectus femoris cranially, the femur and vastus lateralis caudally,
and the middle gluteal dorsally. There are several other
approaches to the hip joint.
-
-
-
- 6.3.2.4 The stifle
joint
- What was mentioned about the
stifle joint of the horse, (up to and including the collateral
ligaments) applies also to the dog. Note the most obvious
differences in the stifle of the dog, different shape of patella,
single patellar ligament, equal size of lips of trochlea of
femur, presence of three sesamoids in addition to the patella; the
fabellae, two in origin of m. gastrocnemius and one in origin of
m. popliteus). .
- The incidence of injuries of
this joint in the dog is far higher than in the horse, not simply
because of the greater numbers of this species generally dealt
with in practice, but because of functional
considerations.
- Movements of stifle and hock in
the dog are not 'synchronized' as in the horse (m. superficial
digital flexor is a proper muscle in dog, not the 'mechanical'
structure we find in horse. There is no femorocalcanean tendon in
dog, and the peroneus tertius is represented in dog by a
non-functional fascial strip.) There is a greater range of
mobility in dog's stifle - greater degree of flexion and
extension, also, due to greater mobility of hip joint, greater
degree of inward and outward rotation, and also abduction and
adduction. It is not surprising, therefore, that injuries of
stifle (and hip) should be so common in dog.
- It is true to say that in
flexion, the femoral condyles and menisci move back on the tibia,
thereby tensing cranial cruciate and meniscal
ligaments; conversely, in extension the femoral condyles and
menisci move forward on the tibia, thereby tensing caudal
cruciate and meniscal ligaments. But it is obvious that, in
over-flexion and over-extension, both cranial and caudal ligaments
will be involved, and it would be necessary to know how much
inward and outward rotation and how much abduction and adduction
is taking place at the same time inorder to determine which
movements cause the rupture of which ligaments, and which
ligaments are ruptured first. It is certainly obvious enough that,
in over-flexion and over-extension, forces are being exerted to
draw femoral and tibial condyles apart and any such force is bound
to stretch both cruciate and collateral ligaments; and any
stretching of these structures is bound to give rise to such
distortion and abnormal mobility within the joint itself, that
meniscal ligaments rupture and damage to the meniscus near the
joint capsule (from which it receives its blood supply) are almost
certain complicating factors. The medial meniscus is more often
damaged than the lateral one. The cranial cruciate ligament is
more often damaged than the caudal one, and medial meniscus damage
is often co-existent with cranial cruciate damage.
- Rupture of a cruciate ligament
produces abnormal mobility in a craniocaudal direction. In rupture
of the cranial cruciate, the tibia can be moved forward on the
femur; in rupture of the caudal cruciate, the tibia can be moved
backward on the femur. These abnormal movements must be produced
without either flexing or extending the joint. Surgical correction
of the cranial cruciate rupture has been effected by cutting a
strip from fascia lata, leaving distal end attached, and threading
it through femoral and tibial tunnels to be anchored at medial
aspect of tibia; but this is just one of many different methods of
replacing ruptured cruciate ligament.
- Rupture of one of the
collateral ligaments facilitates abnormal mobility in a
mediolateral direction, and a joint space can be felt at the side
of the rupture. The abnormal mobility becomes more marked if the
capsule and the meniscus have been torn also. Surgical correction
has been effected by suturing a strip of fascia over the ruptured
ligament. Luxation of the patella is more often medial than
lateral.
-
- 6.3.2.5 Tarsal
joint:-
- Fracture and/or dislocation of
central tarsal occurs, and with it, stretching of plantar
ligament. In fracture of calcaneus, plates and/or screws are used.
Fractures of one or both malleoli occurs with or without rupture
of collateral ligaments.
-
- 6.3.3 NERVES
- Lumbosacral plexus:
ventral branches of last four lumbar and first two sacral (L4-7
& S1,2) go to the lumbosacral plexus and then from this to the
pelvic limb proceed the following nerves:
-
- Femoral N. (L4,5,6)
supplies m. quadriceps femoris (extensor of stifle): gives off
saphenous N. (just before it plunges into this muscle) which,
after supplying m. sartorius, becomes cutaneous on medial aspect
of limb, ending as part of dorsal N. supply to digit
II.
-
- Obturator N. (L4,5,6)
passes down medial aspect of shaft of ilium (covered partly by m.
obturator internus) and runs through obturator foramen to supply
adductor group of muscles.
-
- Gluteal Nn. (L6,7 &
S1,2) supply gluteal muscles and m. tensor fasciae
latae.
-
- Sciatic N. (L6,7 &
S1,2). From greater sciatic notch, it passes back between deep and
middle gluteal muscles, then turns down behind hip joint. It lies
quite near this joint and the trochanteric fossa which is a site
of intramedullary pinning and runs down between biceps and
semitendinosus muscles. It gives off the peroneal N. and continues
as the tibial N. The tibial N. runs down between the two
heads of gastrocnemius, then travels down craniomedial aspect of
common calcanean tendon and divides into the plantar Nn., which
innervate the plantar aspect of the pes.The peroneal N.
runs across lateral face of lateral head of gastrocnemius and just
below stifle it divides into superficial and deep branches, both
of which supply the whole of the dorsal aspect of the pes (the
saphenous N. assists minimally in supplying digit II).
-
- A knowledge of cutaneous
nerve distribution is necessary for testing integrity of nerve
reflexes.
-
- 6.3.3
VESSELS
- 6.3.4.1 ARTERIAL: The
position of the main arterial trunk should be followed out in the
dissected limbs. The femoral artery (in which the pulse is
very easily felt) lies in the femoral canal along with saphenous
N. (cranially) and femoral vein (caudally). Boundaries of femoral
canal are m. sartorius cranially and m. pectineus caudally.
Femoral artery is continued as popliteal artery which
(along with vein) lies close against caudal aspect of stifle
joint. Deviating forward and outward, the popliteal is then
continued through the interosseous space (between tibia and
fibula) as cranial tibial artery which runs down between
tibia and muscles and crosses the flexor aspect of the hock as the
dorsal pedal artery (dorsal artery of pes): in this
position, as it lies between tendons of mm. tibialis cranialis and
extensor longus, its pulse can be felt quite distinctly. Then it
disappears between metatarsals II and III as perforating
metatarsal artery. Just before this, it gives off (small)
dorsal metatarsal arteries, and just as the perforating metatarsal
emerges at the plantar aspect of the paw, it gives off large
plantar metatarsal arteries which supply most of the blood
of the paw. The rest of the blood supply to the plantar aspect of
the paw is derived from caudal branch of the saphenous branch of
the femoral artery.
-
- 6.3.4.2
Venous:
- There are satellite veins to
all the main arteries. The large subcutaneous vein of the pelvic
limb is commonly referred to simply as the aphenous vein, but
strictly speaking the saphenous vein, satellite of the saphenous
artery, is on the medial aspect of the limb as in all our species;
and the one on the lateral aspect, large and used for intravenous
injections, is the lateral saphenous vein. Follow the
course of this vein on the dissected limbs. It drains the dorsal
aspect of the pes, runs backward and upward on the lateral aspect
of the leg just above tarsus and, receiving a large radical from
the lateral plantar aspect of pes, reaches the caudal border of
gastrocnemius, then goes deeply disappearing between biceps and
semitendinosus and joins femoral vein. Just above the level of
tarsus, it has an anastomosis round cranial aspect of leg with
medial saphenous vein.
-
- 6.3.4.3 Lymphatics
- Popliteal lymph node: the only
palpable node on pelvic limb of dog. Situated caudally, almost
subcutaneously, among some fat and partly between biceps and
semitendinosus, it is almost in line with caudal aspect of stifle
joint.
-
-
6.4
CLINICAL CONSIDERATION:
- The following are some
surgical considerations relevant :
-
- Nerve
paralyses
-
- Sites of joint puncture
(surgical)
-
- Fractures of head of
femur,-distal femoral shaft, tarsal bones
-
- Hip
dysplasia
-
- Luxation of
patella
-
- Rupture of ligaments of
stifle joint (cruciate, meniscal) Sites of pulse
-
- Lateral saphenous
venipuncture;
-
- Common surgical approaches
to fracture sites;
-
- Surgical approaches to
joints;
-
- Palpable lymph
nodes;
-
- Cutaneous
innervation
-
-
-
-
-
- inner pelvic muscle of the
dog
-
- muscles surrounding hip
joint-dog
- ligamentws of stifle
joint-dog
- menisci ligments and cruciate
ligaments of stifle joint-dog
-
- Caudal surface
- Lateral surface