Structure & Function of the Pelvic Limb Flashcards
Describe the role of the pelvic limb in locomotion.
- Synsarcosis - muscular attachment of limb that increases effective limb length with free range of motion
- Proximal pelvic limb is mor robust and is relatively fixed to the trunk at the sacroiliac joint
- Thoracic limb is relatively more columnar
Role of pelvic limb:
Power and repulsion-
-drive the body forward
- power the body upwards / over obstacles (running)
- kicking (defence)
Some non-locomotory function-
- eg: scratching / cocking the leg
Hindlimb is more highly adapted for locomotion only
Human/bear/ape - plantigrade posture allow for a long lever to have a large stride
Carnivore - digitigrade posture is more angular
Ungulates (horse/deer/etc…) - unguligrade with shorter but more robust proximal limb but distal limb is longer and reduces more distally
Discuss differences in pelvic limb anatomical structure between the major veterinary species and how this relates to their locomotor.
Joints of the pelvic limb:
- 3 joints in the stifle (knee)-
— femorotibial ; patellofemoral ; superior tibiofibular
- 3 joints in the tarsus (ankle)-
—tibiotarsal ; intertarsal ; tarsometatarsal
- sacroiliac
- coxofemoral (hip)
Pelvic girdle:
Main site of muscle attachment in the hind limb
Most ventral part of the bone is the pubis - made of right and left side with central pubis symphysis joint
Wings of the ilium are broad and adapted for muscle attachment
Bottom of pelvis is the ischium - with the ischial tuberosity (seat bones) to the sides with a central ischial symphysis
Acetabulum - where ilium, pubis and ischium meet (ball and socket joint)
Hip joint:
In the acetabulum sits the proximal femoral head
Rest of femur connected via weak femoral neck
Distal end of femur has 2 condyles which sit on the surface of the tibia
(horses have shorter and thicker femurs with a more formed femoral neck for strength)
Hip extension-
- Gluteals (deep/middle/superficial)
- Hamstrings (semimembranous/semitendinous/biceps femoris)
Hip flexion:
- Cranial thigh muscles (sartorius/quadriceps femoris/tensor fasciae latae)
Hip adduction-abduction:
- adduction - medial thigh muscles
- abduction - lateral gluteal muscles
Knee:
- Tibial plateau - flattened area
- Menisci can be found within the stifle joint
- Canine patella is an oval shape that sits between 2 tibial condyles
- Patella-locking mechanism - asymmetrical with different size condyles to lock the patella into an enlarged ridge that allows the horse to stand for long period of time - energy efficient
Patella:
- Sesamoid bone embedded in tendon - quadricep femoris inserted on top to increase leverage, protection and to reduce friction
- Shape varies between species but:
- Articular facet with femur
- Cranial facet under skin
- Basis for muscle attachment
- Apex faces distally
Patella locking enabled in the horse
Fibula does not form part of the stifle joint (sits more distally)
Fibula is reduced distally in the horse to reduce their distal mass
Stifle joint motion:
- Stifle flexion (located caudally to the stifle) - hamstrings / gastrocnemius
- Stifle extension (located front of the thigh) - quadriceps (predominantly)
- Horses have 6 bones in their tarsus - sometimes 7 if bones I & II are not fused
- Talus has trochlear ridges that form the articulation with the distal end of the tibia to allow the hinge motion
- Calcaneus - prominent projection for the attachment of muscles and for muscle extension
- Nomenclature is the same for tarsus as in carpus
Canine tarsus:
- Less distinct trochlear
- Smaller central tarsal
- Reduced and separate I-IV
- Four metatarsal bones
Reciprocal apparatus (horse) - peroneus tertius and superficial digital flexor act as rigid struts where one cannot move without the other (they will both flex/extend)
Function-
- Swing phase = clear limb from ground
- Stance phase = part of passive stay apparatus
- In support of extended limb
Lumbosacral plexus supplies all pelvic limb structures with nerves and blood vessels
