Hindlimb Week Flashcards
What is blurring and how can we overcome this?
- Involuntary Movement e.g. Breathing
- Voluntary Movement e.g. Of limbs
HOW CAN WE OVERCOME THIS? - Sedation or anaesthesia- gives control over breathing and reduces conscious movement
- Positioning aids can hold the animal in place
What is geometric distortion?
If an object is positioned obliquely to the beam.
OR
Not in the centre of the beam.
What is the order to ensure a diagnostic radiograph?
- Positioning
- Centring
- Collimation
- Exposure
- Labelling
- Artefacts
What are some key safety issues with radiography?
- harmful to living tissues.
- general cell damage can cause cancer, infertility, cataracts, aplastic anaemia.
What are the 2 orthogonal view?
- Mediolateral (ML)
- Craniocaudal (CrCd)
What are the 4 standard views of the equine limb?
- Lateromedial (LM)
- Dorsopalmar / Dorsoplantar (DP)
Two 45 Oblique views:
- DorsoLateral-Planta(/palma)roMedial Oblique (DLPMO)
- DorsoMedial-Planta(/palma)roLateral Oblique (DMPLO)
How is stride length in the horse enhanced?
- Mediolaterally flattened thorax with the scapula positioned laterally.
- Scapula and shoulder joint free to move.
- Ulna becomes vestigial (olecranon increasing lever action of triceps.)
- Elongation of the distal bones particularly in the metacarpus/tarsus and digit.
How is stride rate enhanced?
- Concentration of musculature proximally ( concurrent reliance on passive mechanics.)
- Reduction to a single digit (with concurrent elongation of the lightest segments of the limb.)
- Brachium is relatively short and highly muscular.
What are the anatomical features of the thoracic limb? ( compared to the hindlimb)
- Carry more static body weight (60%)
- Translate horizontal velocity provided by hindlimbs whilst minimising wasteful vertical energy
- Shorter and straighter than hindlimb
- Connected to the trunk only by muscle and ligament (not bone to bone articulation)
- Broader, more rounded hoof
- Energy storage (tendons)
How are tendons able to store kinetic energy?
- Potential energy is stored in stretched tendons.
- Stored energy is converted back to kinetic energy.
What are the anatomical features of the pelvic limb? (compared to the thoracic limb)
- Longer and more angular than the thoracic limb.
- Osseous articulation to the trunk (axial skeleton) through a sacroiliac joint.
- Musculature capable of simultaneously extending hip, stifle, & hock.
- Narrower, more pointed hoof.
- Provide the forward impulsion of the horse.
What are the 3 elements that make up the stay apparatus of the pelvic limb?
1) Patella locking- when a horse rests its weight, the stifle can extend beyond a certain point. This causes the patella to move to the proximal extremity of the trochlear groove, a medial twist then results in the medial ridge protruding between the middle and medial patellar ligaments with the patellar cartilage hooking over the trochlea tubercle. Thus the patella is locked and further flexion is not possible. This results in an immobile stifle joint and so no muscle activity is needed to maintain the leg in this position; thus allowing the horse to rest a lot of its weight on this leg.
2) Reciprocal apparatus- there are two tendinous cords(Peroneus tertius and the Superficial digital flexor) which cause united movement of the stifle and hock. This allows powerful extensor muscles sited proximally to act upon the distal limb.
3) Suspensory apparatus- the suspensory ligament (interosseous muscle) originates in the proximal metacarpal/tarsal region, this runs to the proximal sesamoid bones and then continues in a series of distal sesamoidean ligaments, it maintains the fetlock in a position of mild hyper-extension.
What are the elements that make up the stay apparatus of the thoracic limb?
- -Serratus ventralis forms a suspensory sling, the shoulder is maintained in extension by:
- Supraspinatus muscle.
- Co-operative antagonism of the biceps, which has extensive inelastic tendinous components, with reciprocal contraction of the triceps.
- -The superficial digital flexor muscle, continues past the carpus as a thick tendon, this creates a ligamentous connection from the distal radius to the pastern that can help prevent extension of the carpal and fetlock joint without muscle contractions.
- -The deep digital flexor also forms a thick tendon just proximal to the carpus. This ligamentous tissue between the metacarpal region and distal phalanx helps prevent extension of the fetlock , pastern and coffin joints.
- -The bony column through the carpus minimises muscular effort, the Lacerates fibrosus which runs through extensor carpi radialis prevents carpal flexion.
What is the purpose of fracture fixation?
- minimise strain of fracture callus
- allow healing to occur
- spatial realignment
- takes load until bone strong enough
- weight bearing on limb
- reconstruct the original structure
- neutralise forces acting on fracture site
What are the 5 fixation options and give some details on each
Splints and casts:
- immobilise fracture
- do not directly contact bone
- rigid material
External fixator:
- for complex fractures
- used where there is high risk of infection
Plates and screw:
- resist all 3 forces
- screws apply friction between plate and bone
apply compression between fragments
- plates involve an internal splint and hold fractured parts in alignment, it allows compression between fracture ends and load transfer
- long bones are loaded eccentrically which results in tension side and compression side, the position plate on tension side helps counteract load compressing on opposite side.
Intramedullary rod:
- little resistance to axial compression or torsion
- resist bending forces
Interlocking nails:
- resist all 3 forces
- central nail resists bending
- screws/bolts prevent collapse under compressive force, prevent rotation with torsional force and are placed away from fracture to avoid weakening it.
