Gait, Conformation & Lameness
During slow-motion examination of a horse, the clinician marks the instant at which the toe leaves the ground and the limb transitions from stance into swing.
What is breakover?
A dog requires cerebrospinal fluid collection from the most commonly used cranial site. The needle is introduced through the atlanto-occipital space to enter this enlarged region of the subarachnoid space.
What is the cerebello-medullary cistern (cisterna magna)?
A mutation prevents calcium from binding to the regulatory protein that normally initiates movement of tropomyosin away from actin’s active sites.
What is troponin C?
Following segmental myofiber necrosis, these normally quiescent cells become activated and supply the precursor cells needed for regeneration.
What are satellite cells?
A horse develops rapid atrophy of the supraspinatus and infraspinatus muscles, producing a prominent scapular spine and lateral instability of the shoulder.
What is suprascapular nerve injury, or Sweeney?
A horse is difficult to identify as lame while walking or trotting in a straight line. The lameness becomes consistently apparent when the horse is lunged on a circle. Using the AAEP system presented in the lecture, this is the most appropriate grade.
What is Grade 2 of 5 lameness?
Grade 2 is difficult to observe under some circumstances but can be made consistently apparent under specific conditions.
A surgeon approaching the vertebral column identifies the muscle group dorsal to the transverse processes and supplied by the dorsal branches of the spinal nerves.
What are the epaxial muscles?
A muscle biopsy is obtained while the muscle is maximally contracted. The thin and thick filaments have not changed length, but two sarcomeric regions have become narrower while one remains constant.
What are the I band and H zone becoming narrower while the A band remains constant?
A muscle biopsy shows segmental coagulative necrosis followed by macrophage invasion and myoblast formation. Despite an adequate satellite-cell response, the affected region heals by fibrosis because this structure was destroyed.
What is the basal lamina?
Successful myofiber regeneration depends heavily on preservation of the basal lamina.
A dog sustains an injury to the radial nerve proximal to its branches to the triceps brachii. This major functional deficit is expected because the triceps is the principal muscle responsible for this action.
What is extension of the elbow?
A horse highers its head each time the left forelimb accepts weight and lowers its head when the right forelimb accepts weight. This is the limb that should initially be localized as painful.
What is the left forelimb?
In forelimb lameness, the head rises as the painful limb bears weight and falls as the sound limb bears weight.
During a dorsal spinal approach, the surgeon reflects the most medial epaxial system adjacent to the spinous processes. This system is particularly relevant during a laminectomy and contributes to vertebral stabilization.
What is the transversospinalis system?
From lateral to medial, the major epaxial systems are iliocostalis, longissimus, and transversospinalis.
A motor neuron generates a normal action potential, but acetylcholine cannot produce adequate depolarization of the motor end plate. The most immediate downstream consequence is failure of this event.
What is propagation of a muscle action potential along the sarcolemma and into the T-tubules?
Several rapidly growing calves develop weakness and pale skeletal muscle containing mineralized streaks. Their diet was deficient in two antioxidant nutrients.
What is nutritional myopathy caused by selenium and vitamin E deficiency?
During weight bearing, weakness of these muscles permits the thoracic limbs to abduct away from the body rather than remaining securely adducted beneath the trunk.
What are the superficial pectoral muscles?
The superficial pectorals adduct a non-weight-bearing limb and help prevent abduction during weight bearing.
A mature horse stands with both forefeet rotated medially. During the swing phase, each distal limb travels outward before returning inward toward the line of progression. This gait pattern is most consistent with the horse’s conformation.
What is paddling associated with a toed-in conformation?
A dog presents with lumbosacral pain, an arched back, hindlimb lameness, and urinary incontinence. Degenerative tissue located between adjacent vertebral arches is contributing to stenosis.
what ligament is affected?
What is the interarcuate ligament?
A horse increases muscular force during acceleration without requiring every individual myofiber to produce more force. The nervous system accomplishes this primarily through this mechanism.
What is recruitment of additional motor units?
A male puppy develops progressive weakness. Muscle biopsies show repeated cycles of necrosis and attempted regeneration caused by fragility of the myofiber membrane. The defective structural protein is this one.
What is dystrophin?
A horse with severe muscle rigidity requires short-term intravenous anesthesia. The clinician selects a centrally acting relaxant used with xylazine and ketamine, but avoids administering it to the fully awake horse.
What is guaifenesin?
The combination of guaifenesin, xylazine, and ketamine is commonly called “triple drip.”
A performance horse has a subtle gait abnormality that worsened shortly after a new farrier changed the hoof balance. The horse is less lame after rest but worsens with exercise. Before performing diagnostic analgesia, this is the most important next step.
What is a complete static and dynamic orthopedic examination that includes assessment of conformation and hoof balance?
The history should guide, but not replace, systematic evaluation of posture, symmetry, gait, affected circumstances, and recent management changes.
Extra:explain the difference of static vs dynamic
A thoracic intervertebral disc herniation is considered less likely between T2 and T11 because this structure connects the heads of adjacent ribs and provides additional disc stabilization.
what ligament is this?
What is the intercapital ligament?
Damage to this ligament can contribute to vertebral pain and instability.
A tendon is stretched during weight bearing and recoils during propulsion. Loss of this property would increase the muscular energy required for locomotion even if muscle contraction remained normal.
What is the tendon’s ability to store and release elastic energy?
Tendons transmit force to bone, stabilize joints, and reduce the metabolic cost of locomotion by storing and releasing elastic energy.
A dog has exercise-associated weakness that improves after rest. Muscle fibers and peripheral nerves are structurally intact, but antibodies interfere with postsynaptic transmission. This is the primary target.
What are nicotinic acetylcholine receptors at the neuromuscular junction?
This pattern is most consistent with myasthenia gravis rather than a primary degenerative myopathy.
A mechanically ventilated patient receives a drug that competes with acetylcholine for postsynaptic nicotinic receptors. The patient becomes paralyzed but is still capable of perceiving pain unless other drugs are administered.
What is a competitive nondepolarizing neuromuscular blocker?
Neuromuscular blockers produce paralysis, not unconsciousness, sedation, or analgesia. They must be used with appropriate anesthesia and ventilatory support.