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Anatomy Y2 > Equine Hindlimb > Flashcards

Equine Hindlimb Flashcards

1
Q

Briefly describe the arteries of the equine hindlimb.

A
  • Mainly cranial and caudal tibial
  • Cranial tibial perforates through the tarsal bones to the plantar surface
  • Vessels past the tarsus and as for the foreleg
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2
Q

Describe the venous supply of the equine hindlimb.

A

Satellite apart from enlarged medial and lateral saphenous vein. Medial saphenous large and palpable over dorsal hock.

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3
Q

What does the tibial nerve innervate in the equine hindlimb?

A

Tibia nerve will supply the majority of sensory innervation to the distal limb, and will supply the plantar and plantar metatarsal nerves

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4
Q

What will the deep fibular/peroneal nerve innervate in the equine hindlimb?

A

The dorsal metatarsal nerves and runs medial and lateral to the extensor tendons.

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5
Q

Describe the equine hip structure.

A
  • Uncommon cause for clinical problems in the horse as the hip is very stable
  • Thick musculature provides propulsion as well as support
  • Luxation requires serious trauma or congenital weakness
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6
Q

Name the 4 stabilising structure of the equine hip.

A
  • Deep acetabulum – holds femur well. Cartilage rim on dorsal lip deepens further
  • Ligament of the head of the femur – similar to in dogs but shorter and limits movement more
  • Accessory ligament – only in horse and donkey. It restricts abduction
  • Muscles of the hip
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7
Q

Describe the action of the ligament of the head of the femur.

A

Holds the femur into the acetabulum

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8
Q

Describe the action of the accessory ligament of the hip.

A

Accessory ligament of the hip runs form the medial side of the head distal to the articular surface to the prepubic tendon. Limits abduction that can occur die to tension in the ligament and partly due to the weight of viscera when standing, which weighs down on the pre-pubic tendon and stretch out this ligament.

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9
Q

Locate the 3 functional muscle groups of the equine hip.

A

Extensors – cranial to the hip and caudal to the hip

Flexors – all cranial to the hip

Adductors – medial to the hip

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10
Q

Describe abduction in the horse.

A

Some muscles have actions as abductors but this action is severely limited in horses by joint support structures.

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11
Q

Name the cranial hip extensors and what innervates them.

A

Cranial gluteal
Deep gluteal

Gluteal nerve

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12
Q

What is the position and function of the cranial gluteal muscle?

A

Dorsal lumbar fascia to the greater trochanter. Covers the tuber sacrale, which limits palpability.

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13
Q

What is the position and function of the deep gluteal muscle?

A

Deep to middle gluteal (caudal aspect). From dorsal ischium/acetabulum to the greater trochanter. Mostly dorsal joint support (‘abducts’).

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14
Q

Name and describe the caudal hip extensors and name the nerve that innervates them.

A

Hamstrings – biceps femoris, semitendinosus and semimembranosus.

Extra vertebral heads in the horse continue over the ischium and makes palpation of tuber ischii hard in normal horse, and contributes to very rounded rump.

All innervated by the sciatic nerve.

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15
Q

Name the hip flexor muscles.

A

Superficial gluteal
Iliopsoas
Sartorius
Tensor fascia lata
Rectus femoris

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16
Q

Describe the position and function of the superficial gluteal muscle.

A

Different function in the horse, as its insertion is much more distal on the 3rd trochanter, so is a flexor instead of extensor/abductor.

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17
Q

Name the adductors of the equine hip and their function.

A

Mostly to resist abduction. Origins and insertions similar to dog.

Superficially: gracilis and (minorly) sartorius, single belly

Deeper = pectineus and adductor

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18
Q

Describe the deep muscles of the equine hip and name the muscles.

A

Small hip ‘rotators’ will be more noticeable in the horse. These are of minimal clinical importance but mainly provide support to the hip joint.

Gemelli
Internal/external obturator
Quadratus femoris
Articularis coxae

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19
Q

When does the equine stifle joint become clinically significant?

A
  • Uncommon cause of lameness
  • Patella can be locked to limit stifle flexion while resting as part of the passive stay apparatus.
  • Can cause lameness if ‘stuck’ in upward fixation
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20
Q

How is the equine stifle joint different to the canine stifle joint?

A
  • Enlarged medial femoral condyle
  • Tripartite (has 3 sections) patellar ligament attaches patellar to the tibia
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21
Q

How are the equine and canine stifle joints similar?

A
  • Muscle insertions on patella and tibial tuberosity via patella tendon and ligaments as in the dog
  • Has same set of menisci and cruciate ligaments as in the dog
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22
Q

Describe the structure of the patellar ligaments and link this to locomotion at the patella.

A
  • Enlarged medial femoral condyle
  • Hook shaped structure is the patella cartilage, over condyle
  • This is lifted medially by musculature, particularly the medial vastus, and then drops the patella over the medial femoral condyle.
  • Medial patella ligament will hook up to the medial side, intermediate patella ligament that will stay lateral to that medial femoral condyle and the lateral patellar ligament that is the most lateral structure.
  • Fatty pads sit between these
  • Medial vastus will also allow for unlocking so that other muscles can pull the patella laterally to come back into moving position.
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23
Q

Name the 3 main articulating parts of the equine stifle joint.

A

Femoropatellar
Lateral femorotibial
Medial femorotibial

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24
Q

Describe the communication of the synovial compartments of the stifle joint.

A

Each of the articulating parts has its own synovial compartment: the medial femorotibial and femoropatellar usually communicate but the lateral femorotibial is separate. This is important for injections and blood sampling.

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25
Q

Name the 4 extensors of the stifle joint and state where they originate.

A

Quadriceps femoris:

Vastus lateralis – originate from femoral shaft

Vastus intermedius – originate from femoral shaft

Vastus medialis – originate from femoral shaft

Rectus femoris – origin on ilium, cranial to the acetabulum

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26
Q

What nerve innervates the extensor muscles of the stifle and how do these extensors act?

A

Act via the patella and patellar tendon/ligament

All innervated by the femoral nerve

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27
Q

Name the flexors of the stifle and their innervation.

A

Hamstrings – biceps femoris, semitendinosus, semimembranosus. Innervate dby the sciatic nerve.

Gastrocnemius (minor). Innervated by the tibial nerve.

Popliteus (minor). Innervated by the tibial nerve.

Superficial digital flexor (potential, not in itself activating flexion). Innervated by the tibial nerve.

28
Q

What are bi/multiarticular muscles?

A
  • If a muscle crosses the palmer/plantar surface of the limb, there are slightly different set sof names and actions.
  • In the forelimb, a muscle that runs palmarly to the entire distal limb will cause flexion of all of the joints.
  • In the hindlimb, a muscle that runs plantarly to the enture distal limb will cause flexion of the digital joints and extension of the hock joint itself.

Digital flexors (and flex stifle) = hock extensors

29
Q

Name the 4 joint levels in the tarsus.

A

Tarsocrural
Proximal intertarsal
Distal intertarsal
Tarsometatarsal

30
Q

Describe the communication of the synovial compartments of the tarsus.

A

Capsule for tarsocrural and proximal intertarsal usually communicates. Distal intertarsal is separate form the proximal intertarsal. Distal intertarsal occasionally communicates with the tarsometatarsal joint.

31
Q

Name the hock flexor muscles.

A

Fibularis tertius
Cranial tibial
Long digital extensor
Lateral digital extensor

No fibularis longus like in the dog

32
Q

Describe the fibularis tertius.

A
  • Very tendinous and very minimal muscle tissue.
  • Part of the reciprocal apparatus.
  • Shares origin with the long digital extensor.
  • Thick tendinous band that runs cranially down the face of the tibia.
  • Innervated by the fibular nerve.
33
Q

Describe cranial tibial.

A

Most cranial muscle but only at the proximal end of the tibia.

Innervated by the fibular nerve.

34
Q

Describe long digital extensor.

A

Shared origin with fibularis tertius. Large and fleshy. Fuses with the lateral digital extensor. Innervated by the fibular nerve.

35
Q

Describe lateral digital extensor.

A

Large and fleshy. Originate son the lateral collateral ligament of the stifle and fuse with the long digital extensor before the distal limb at mid metatarsus. Innervated by the fibular nerve.

36
Q

Name the hock extensor muscles.

A

Gastrocnemius
Superficial digital flexor
Deep digital flexor

37
Q

Describe the position of gastrocnemius.

A

Medial and lateral. Originate son distal end of the femur and inserting on the calcaneus.

38
Q

Describe the position of superficial digital flexor.

A

Inserts on calcaneus and P1-2. Very little muscle structure.

39
Q

Describe the position of deep digital flexor.

A

Originates as 3 bellies, inserts of P3, along caudal aspect of the tibia. Tendon passes medially to calcaneus.

40
Q

Name and describe the 2 tendinous specialised muscles of the reciprocal apparatus.

A

Superficial digital flexor – to make sure this stays in place if the patella is locked. Tethers the point of the calcaneus to the femur and prevent is moving away from the femur and prevent tarsus from folding.

Fibularis (peroneus) tertius

41
Q

What must occur for reciprocal apparatus?

A

Stifle and hock movements are coupled – stifle and hock must flex and extend in tandem. Cause the limb to extend the stifle and flex the hock or flex the stifle and flex the hock at the same time.

42
Q

Explain what would happen if the superficial digital flexor was ruptured?

A

If the superficial digital flexor was ruptured, the hock can continue to flex even when the stifle is locked into position and passive stay apparatus in this region is broken. This is an issue for weightbearing as it will tend towards either the animal collapsing or needing to use a lot more muscular effort to help keep them straight.

43
Q

Explain what would happen if the fibularis tertius was ruptured.

A

If fibularis tertius is ruptured, the horse can extend the hock despite the stifle remining flexed/without extending the stifle. Meaning it can rupture without any effect on weightbearing. But this may prevent the fibularis tertius from helping during locomotion. One theory is that fibularis tertius is storing elastic energy to help flex the hock, so rupture causes a reduced efficiency in forward locomotion.

44
Q

What can be confused with the tarsocrural compartment?

A

Deep digital flexor tendon in the tarsal sheath runs in sustentacular groove of the talus. Swelling of this can be confused with tarsocrural compartment between the tibia and tarsus.

45
Q

What is the function of the calcaneal bursa?

A

Protects the superficial digital flexor tendon as it runs over the calcaneus.

SDFT also has an attachment to the calcaneus, is involved in reciprocal apparatus and some check-ligament like function (prevent hyperextension of digits, but not seen in equine hindlimb, very small).

46
Q

What are the tarsal support structures?

A

Very strong collateral ligaments – short and long portions, medially and laterally.

Long plantar ligament – resists hyperextension of the foot and digital joints. Allows for reciprocal apparatus to function successfully

47
Q

What is the function of equine passive stay apparatus?

A

Reduce energy expenditure at quiet standing.
Some components support cursorial behaviours by preventing joint hyperextension during landing and returning energy of landing via elastic storage.

48
Q

What is involved in hindlimb passive stay apparatus?

A

Less columnar and more flexed throughout the limb than the forelimb.

The hip, stifle and hock all tend to flex with weight bearing. The stay apparatus helps prevent this in the leg. Comprises of the patella locking system, proximal reciprocal apparatus and plantar support structures more distally.

49
Q

Describe the patella locking system.

A

Body mass is applied through the hip joint. The stifle needs to be able to flex and extend so that the animal can run fast.

  • Muscles of the quadriceps femoris help move the patella into position to lock it into place.
  • Vastus medialis is needed to be a little activated to ensure the patella stays in position.
  • To unlock this, the vastus medialis will activate again to help lift everything and then be joined by vastus lateralis to pull everything laterally to unlock the stifle.
  • Because the vastus medialis is so important here, if something happens to the femoral nerve, the system is disturbed and may prevent the animal from having this restful quiet standing.
50
Q

What is the function of the plantar tarsal fibrocartilage?

A

Ensures bones of the distal portion of the hock joint, tarsus, calcaneus and metatarsal bones, act as a single long structure.

51
Q

Outine how the hock and stifle flex in tandem.

A
  1. When the stifle is extended, the superficial digital flexor limits hock flexion.
  2. When the stifle is flex, peroneus tertius limits hock extension.
  3. Superficial digital flexor is important in weight bearing and forward propulsion of the animal.
  4. Fibularis tertius is important in limb swing phase – forward propulsion of the limb but is not essential to weight bearing.
  5. Both fibularis tertius and SDF contribute to elastic energy storage.
52
Q

Outline the superficial digital flexor’s role in standing.

A

Flexion of hock is limited by the proximal portion of the SDF when the stifle is locked.

53
Q

Describe the distal support against hyperextension.

A
  • DDF and SDF tendons provide resistance to hyperextension, just as in the forelimb.
  • Minimal/if any ligaments from the flexor tendons in the hindlimb and the function is provided by reciprocal apparatus.
  • SDF attaches to calcaneus, which provides some prevention to hyperextension.
  • Small check ligaments on DDF to proximal metatarsal III.
54
Q

What parts of the equine proximal hindlimb appear to have more developed musculature than in the dog or cow?

A

The rump/croup area – it has larger muscle bulk dorsal to the ischium and ilium. This is due to larger hip extensor muscles. The hamstrings in particular have additional vertebral heads which attach to the sacrum, tail vertebrae and sacrosciatic ligament. The middle gluteal is also larger and has a wide attachment at its origin.

55
Q

What is the significance of the third trochanter? What action does the muscle attaching here have? Is this different to the dog?

A

The third trochanter is the site of insertion for the superficial gluteal. It is a hip flexor in the horse. It is an extensor in the dog. This is because the tochanter is more distal on the femur in the horse, and thus changes from being a type 1 lever extensor in the dog to a type 3 lever flexor in the horse.

56
Q

Which side femoral trochlear ridge is largest? Why?

A

Medial – it allows the patella to lock over it.

57
Q

The point of the hip is formed by what?

A

Tuber coxae of the pelvis

58
Q

The point of the hock is formed by what?

A

The calcaneus

59
Q

What are the 3 tubers of the equine pelvis?

A

Tuber coxae
Tuber sacrale
Tuber ischii

60
Q

Describe the equine pelvis in comparison with the canine pelvis.

A

In comparison with the canine pelvis, where the ilium is oblong and positioned obliquely, the equine ilium is triangular and positioned nearly vertical bringing the sacroiliac joint more above the hip joint.

The dorsal iliac spine of the canine pelvis is much more prominent in the equine, forming the tuber sacrale. The ventral iliac spine of the canine is also more prominent in the equine, extending laterally to form the tuber coxae/point of the hip

61
Q

How do the tibia and fibula of the equine differ from the canine?

A

Fused

62
Q

Which tendon passes plantar to the navicular bone in the horse hind limb?

A

Deep digital flexor tendon

63
Q

Which type of limb movement requires the obturator nerve?

A

Adduction

64
Q

What are the major functions of the long digital extensor muscle?

A

Flexion of the hock, extension of the digit

65
Q

In the horse, which ligaments help to limit movement of the tibio-talar (hock) joint to flexion and extension only?

A

Collateral ligaments

66
Q

Which ligament in the stifle of dogs is most important in resisting cranial movement/translation of the proximal tibia in relation to the distal femur?

A

Cranial cruciate ligament

Anatomy Y2 (15 decks)

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