Herp Musculoskeletal Disorders & Orthopedics

Question 1

Describe the muscle physiology of reptiles.

Whata re the three types of muscle fibers?

What are the features of tonic fibers? Which taxa has more tonic fibers?

What are the features of twitch fibers? Which taxa has more twitch fibers?

Answer 1

1. Muscle Physiology
   
   1. Reptiles, amphibians, and birds have three types of muscle fibers: broad white, narrow red, intermediate
   2. Reptile muscle fibers can also be classified as twitch and tonic fibers
      
      1. Snakes have more tonic muscles than lizards
   3. Features of tonic fibers:
      
      1. Slow action
      2. Underdeveloped sarcotubular system
      3. Poorly organized myofibrils
      4. Only support junction potentials but not action potentials
      5. Have very more T tubule diads than triads
   4. Features of twitch fibers:
      
      1. More T tubule triads than diads
      2. More organized myofibrils
   5. The sarcomeres of reptiles have:
      
      1. Thick filaments (A bands) of similar size across taxa
      2. Thin filaments (I bands) that vary in size across taxa

Question 2

Which reptiles have haversion bone?

Where is vascular bone located in reptile bones?

How do reptile bones grow?

What are the three differences between squamate and chelonian/crocodilian bones?

What are the phases of healing?

Answer 2

1. Bone Physiology
   
   1. Haversian bone is present in cortical bone in chelonians and crocodiles, but not in snakes and lizards
   2. Reptiles have primary vascular or nonvascular bone
      
      1. Primary vascular bone has canals oriented longitudinally
      2. Nonvascular bone is fine or coarse cancellous bone which eventually becomes compact
   3. Reptile bones grow as the endosteal cortex is expanded upon and moves inward, then the periosteal layer of the cortex grows, which widens the diaphysis
   4. There is no reliable way to correlate rings of bones to age because rings can be resorbed
   5. Bones of squamates differ from chelonians and crocodilians because:
      
      1. Cancellous trabeculae in the mid-diaphysis of long bones is limited, but extensive at the ends of long bones
      2. Almost all bones are nonvascular
      3. No Haversian system of remodelling
   6. Healing is slower because of ectothermic nature
   7. Phases of bone healing:
      
      1. Rapid epithelialization
      2. Sequestration of dead bony fragments
      3. Proliferation of dural periosteum
      4. Organization and fibrosis of the callus
      5. Osteoblast differentiation
      6. Osteogenesis
      7. Bony union
   8. Early fracture repair is defined by proliferative tissue (blastema) around the hematoma at the fracture site
      
      1. Turns into cartilage
      2. No secondary cartilage development in the fracture callus

Question 3

Describe the unique features of the amphibian musculoskeletal system.

What bones do caecilians lack? What is unique about their ribs?

What bones do siren salamanders lack?

What is unique about the anatomy of the anuran hindlimbs?

Answer 3

• Amphibians (adults)
  
  • Caecilians lack pelvic girdle, pectoral girdle, and sacrum
    
    • Also have double-headed ribs
  • Siren salamanders lack a pelvic girdle +/- digits
  • Anurans have a reduced sacrum, modified pelvic girdle
    
    • Urostyle = fused tail vertebrae retained in pelvis
    • Radioulna = fused radius and ulna
    • Tibiofibula = fused tibia, fibula, and tarsal bones
    • Calcaneum and astragalus are fused metatarsals
    • Ilium has an extra joint with the sacrum

Question 4

Describe the unique features of the ophidian musculoskeletal system.

Which family has vestigial limbs?

What bones articulate between the mandible and the skull?

What is unique about the musculature and vertebrae?

Answer 4

1. Ophidia
   
   1. Only boids have vestigial limbs (spurs)
   2. Quadrate bone articulates between mandible and skull
   3. Lack cervical vertebrae but have cervical musculature

Question 5

Describve the unique features of the lizard musculoskeletal anatomy.

What directions do the elbow and wrist move in?

What are three unique characteristics of chameleon MS?

How many phalanges are in each digit?

How does tail autotomy occur?

For regeneration purposes, what methods can be performed for amputation?

Answer 5

1. Lacertilia
   
   1. Very complex pectoral girdle
   2. Elbow moves mediolaterally
   3. Wrist moves dorsoventrally
   4. Typical lacertilians have 9 carpals = 3 rows = 3 proximal + 1 middle + 5 distal
   5. Chameleons have:
      
      1. Poorly developed olecranon, which allows for upright posture
      2. Chameleons have 5 carpals = 2 rows = 3 proximal + 2 distal
      3. Digits 1-3 form medial part of “pincer”, digits 4-5 form lateral part
      4. Symmetrical stifles oriented in line with femur
   6. Lacertilian acetabulum is formed by ilium, ischium, and pubis
   7. Lacertilian stifles have asymmetrical condyles perpendicular to the long axis of the femur
   8. Two tarsal bones typically (3-4), but Sphenodons have 3 (3-5)
   9. Phalangeal formulua = 2-3-4-5-4
   10. Tail autonomy can occur in iguanids and geckos
       
       1. Fracture planes through vertebral body and neural arch
       2. For tail amputation, breaking along fracture plane or surgical amputation both regenerated the tail (in a study in leopard geckos)
2. Amphisbaenia
   
   1. No limbs
   2. Locomote with lateral undulation

Question 6

Describe the unique features of the chelonian MS anatomy.

What are the three different ways chelonians retract their neck?

How many vertebrae do chelonians have?

What are the bones of the chelonian pectoral girdle?

How many phalanges are in the forlimb digits? What about the hindlimb digits?

Answer 6

1. Chelonians
   
   1. Shell = carapace (dorsal) + plastron (ventral)
   2. Turtles that cannot retract normally:
      
      1. Sea turtles can’t retract at all
      2. Pleurodira retract horizontally
      3. Cryptodira retract vertically
   3. Vertebral column = 18 presacral vertebrae = 8 cervical, 10 trunk
   4. Ribs are engulfed in dermal bone and are attached by unmineralized collagen
      
      1. Zig zag pattern seen on rads = suture lines of unmineralized collagen
   5. Chelonians have a complex pectoral girdle
   6. Chelonian humeri are arched
   7. Five metacarpals with phalangeal formula 2-3-3-3-2 (aquartic) or 2-2-2-2-2(1) (terrestrial)
   8. Toes of turtles:
      
      1. Freshwater = 2-3-3-3-3
      2. Terrestrial = 2-2-2-2-1(0)
      3. Marine (2-2-3-3-4)
   9. Sea turtles have a very flat femur
   10. Rectus abdominis and testoiliacus anchor pelvis to the shell

Question 7

What are three unque features of the crocodilian skull?

Answer 7

1. Crocodilians
   
   1. Expanded premaxilla that isolates external nares from the maxilla
   2. Squamosal bones overhang and protect tympanic mambranes
   3. Skull bones are pneumatized

Question 8

Describe the locomotion of the various reptile taxa.

What are the five modes of snake locomotion?

What are the three modes of lizard locomotion?

What are the two modes of crocodilian locomotion?

Answer 8

1. Locomotion
   
   1. Snakes move in five modes
      
      1. Lateral undulation: propagation of lateral bending along body; requires friction
      2. Sidewinding: lateral bending but segments are lifted off surface
      3. Concertina: front and back halves alternate between bending and straight
      4. Rectilinear: ventral scales are lifted up and forward then down and back
      5. Slide-pushing: Irregular, vigorous lateral undulations on a smooth surface
   2. Lizards
      
      1. Lateral bending of the trunk helps with forward propulsion
      2. Sprawling posture (humerus and femur aren’t vertical)
      3. Over 50 species can exhibit bipedal locomotion
      4. Varanids can stand up on hind legs and tails
   3. Crocodilians
      
      1. High walk or belly walk

Question 9

What two nutritional deficiencies result in myopathies in reptiles?

What are the associated clinical signs?

What are the risk factors?

What is the prognosis?

Answer 9

1. Vitamin E and Selenium Deficiency
   
   1. Signs: steatitis, fat necrosis, and muscular degeneration, hard (fat) swelling in coelom or tail
   2. Risk factors: diet high in polyunsaturated fatty acids, rancid fats/oils
   3. Caused necrosis in crocodiles
   4. Diagnosis via biopsy or necropsy
   5. Poor prognosis, but vitamin E supplementation may help
   6. Prevent by storing fit properly (0-22F for <4-6 months)

Question 10

Describe the metabolic bone diseases of herps.

What is the most common? What is it due to?

What are the associated clinical signs? Which animals are most commonly affected?

How does renal secondary hyperparathyroidism occur?

How are these diseases diagnosed and treated?

Answer 10

• Metabolic Bone Diseases
  
  • Nutritional secondary hyperparathyroidism = most common MBD
    
    • Dietary deficiency of Ca or Vitamin D₃ or inadequate UVB exposure
    • Signs: thickening/swelling of mandibles, lameness, pathologic fractures, hypocalcemic tetany, tremors, muscle fasciculations, paralysis, paresis, horizontal rotation of scapulae, cloacal/rectal prolapse, anorexia, stunted growth, toe swelling, misshapen shell
    • More common in diurnal, insectivorous, and herbivorous species
    • Normal vitamin D schedule: cholesterol + UVB → D₃ → 1,25(OH)D (calcitriol)
    • Excessive parathyroid hormone occurs in response to hypocalcemia, causing calcium uptake from bones → osteopenia causes weak bones
      
      • PTH also increases the intestinal calcium absorption
  • Renal secondary hyperparathyroidism
    
    • Chronic renal disease → hyperphosphatemia → low calcitriol → soft tissue calcification, renal osteodystrophy, and hypocalcemia
  • Diagnosis is based on signalment, history, diet, clinical signs, and radiographs
    
    • Ionized calcium is a more accurate representation of calcium stores, but only decreased in end stage disease
    • Mineralization of tissues occurs at >12 mmol/L, but disease tissue (kidneys) can mineralize at 9-12 mmol/L
  • Therapy
    
    • Oral vitamin D is not as effective as exposure to UVB in bearded dragons
    • Parenteral calcium supplementation
    • Hydration
    • Oral vitamin A
  • Prognosis and Prevention
    
    • Guarded to poor prognosis with significant organ dysfunction
    • Tremors, ataxia, and cloacal prolapse are early signs
    • Fibrous osteodystrophy, fractures, and paralysis are poor prognostic indicators

Question 11

Describe the nonmetabolic bone diseases of reptiles.

What pathogens may cause polyarthritis in crocodilians?

What causes gout? What about pseudogout? How are these treated?

What pathogens are associated with spinal osteopathy?

What parasite can result in supernumerary limbs in amphibians?

What is spindly leg syndrome?

Answer 11

• Osteomyelitis and Arthritis
  
  • Poor husbandry → immunocompromise → infection
  • Toes are susceptible from external trauma or vascular compromise
  • Mycoplasma alligatoris and crocodyli cause polyarthritis in crocodilians
  • Diagnosed by radiographic lytic lesions, bone biopsy, culture
  • Treat with surgical debridement, antimicrobial therapy, analgesia
• Noninfectious arthropathy and gout
  
  • Gout = metabolic dz with overproduction or underexcretion of uric acid → hyperuricemia → deposition of monosodium urate in tissues
    
    • Radiolucent deposits around joints
    • Visceral or articular
  • Pseudogout = hydroxyapatite or calcium pyrophosphate dihydrate deposition
    
    • Radiodense deposits around joints
  • Risk factors = dehydration, high protein diets, stress, renal dysfunction, vitamin ABCorE
  • Diagnosis with biochem, FNA, radiographs, ultrasound (urate=increased echogenicity)
  • Treat with rehydration, allopurinol (reduce UA production by competitively inhibiting xanthine oxidase), +/- surgical removal
• Spinal Osteopathy
  
  • Observed in lizards, turtles, snakes
  • Thought to be chronic bacterial osteomyelitis → anklyoses
    
    • Salmonella, Klebsiella, Morganella in snakes
  • Diagnosis with imaging, culture, biopsy
  • Long term antibiotics may be helpful but poor prognosis overall
• Tail Disorders
  
  • Avascular necrosis causes distal tail to be hard, dry, and stiff
  • Iguana hemipenes can swell significantly in the tail during breeding season
• Supernumerary Limbs
  
  • Caused by digenic trematodes (Ribeiroia ondatra) in hind limb amphibians
    
    • Penetrates skin in cercarial larval stage to form cysts
  • High mortality, do not survive to maturity
  • Causes polydactyly, polymelia, and jaw malformations
  • Associated with exposure to herbicide atrazine in northern leopard tree frogs
  • No treatment
• Spindly Leg
  
  • Developmental abnormality of the forelimb of amphibians
  • One or both forelimbs fail to erupt normally
  • Fata disease
  • Supplement with vitamin B
• Overgrown rhamphotheca and nails may be lack of wear or excess protein

Question 12

Describe the management of fractures in herp species using external coaptation.

Answer 12

MARMS - 108. External Coaptation

1. General Principles
   
   1. Reptiles rarely have comminuted or open fractures due to slow impact forces and elastic skin
   2. Bone healing takes 6 to 18 months
   3. MBD fractures do well with external coaptation because hardware doesn’t work
   4. External coaptation uses bandages, splints, or slings to immobilize a fracture
2. External Coaptation
   
   1. Forelimb fractures should include a wrap around the body
   2. Hindlimbs can be wrapped with the tail
   3. Small splints can also be applied
   4. Chelonian fractures can be pushed into the shell to immobilize the limb
   5. Snakes can have their body casted for spinal luxations/fractures

Question 13

Describe the management of bone fractures in herp species with fracture fixation.

What animals may be poor candidates for fracture fixation?

What are some common complications with these procedures in reptiles?

What are some common sources for bone grafts?

Answer 13

MARMS - 109. Fracture Fixation

1. Fracture Fixation
   
   1. Bones with MBD may be a poor candidate for fixation with hardware because the bones are too soft
   2. Alternative to expensive Steinmann pins and orthopedic wires = Kirschner wires and spinal needles
   3. External skeletal fixation can be a good option, but not in chelonians or aquatic animals
      
      1. Must be cleaned daily
   4. Complications in reptiles: hardware loosening prior to fracture healing, osteomyelitis
2. Bone Grafting
   
   1. Osteogenic grafts supply bone forming cells
   2. Osteoinductive grafts induce bone formation where none will occur
   3. Osteoconductive grafts provide a scaffold for bone formation
   4. Sources for bone grafts:
      
      1. In large reptiles, proximal humerus or femur
      2. In small reptiles, wing of ilium
      3. Rib
3. Arthrodesis
   
   1. You can do arthrodesis, if absolutely needed
   2. In an iguana elbow, arthrodesis took 12 weeks

Question 14

Describe limb amputation in herp species.

What are the indications?

Amputation is typically performed at what locations?

What are some common complications?

Describe the techniques commonly used.

Answer 14

MARMS – 111. Limb Amputation

Conditions necessitating amputation:

• Chronic dysecdysis around a toe/wire/string around a limb- leading to ischemic injury
• Uncontrolled pain or infection
• Osteomyeliitis
• Highly comminuted fractures and nonunions
• Neoplasia

Location

• Phalangeal lesions- usually amputated to level of metacarpus/tarsus
• Forelimb- disarticulation of scapulohumeral joint or removal of scapula
• Hindlimb- osteotomy at mid-diaphysis of femur, disarticulation of coxofemoral joint and acetabulectomy.

Complications

• Gait change, seroma, neuroma, phantom pain, and cervical disc herniation
• Partial limb amps- usually reserved for small lizards and chelonians

Techniques

• Skin incised distal to amputation for flap and tension-free closure
• Muscle bellies transected at distal insertions or distally as possible and dissected proximal to allow for adequate padding.
• Soft tissue ideally transected using radiosurgery or laser to reduce hemorrhage.
• Inject nerves with lidocaine or bupivicaine to minimize postop pain
  
  • Consider intrathecal in chelonians (chapt 51)
• Chelonians prosthesis
  
  • Wheeled devices work best on firm level ground
  • Half-balls best on natural ground

Question 15

What are some common causes of tail abnormalities in reptiles?

What species have tail autotomy? What ones do not? What species lost that ability with maturity?

Answer 15

MARMS – 168. Tail Damage

• Mechanical, Traumatic, Infectious, and physiological
• Used for social signaling, locomotion, predator avoidance, and prey luring, fat storage
• Caudal autotomy (tail drop)
  
  • Not in chameleons, most agamids, monitors, helodermatids, xenosaurids, and lanthanotids), and tuataras
  • but has also been reported in some snakes and amphisbaenids.
  • Lost with maturity: including Ctenosaura, Cyclura, Iguana, Sauromalus, and some Tiliqua

Clinical Presentation

• Ascending vascular necrosis is common in green iguana, bearded dragon, monitors, tegus, and others
  
  • Aggressive defensive animals slapping tails against wall
  • Vessel calcification, thromboembolism
  • Bacterial causes
• Inspissated or abscessed scent glands
• Hemipenes that are impacted, swollen..
• Thermal burns, stuck to tape
• Rodent bite
• Chelonians- juveniles- lose tails or tips with retained shed when kept in low humidity environment.

Question 16

Describe the procedure for tail amputaiton in reptiles.

What species have autotomy along the length of the tail?

What species have autotomy restricted to the tail base?

What taxa do NOT have autotomy?

How do you amputate a tail to allow for regrowth?

Answer 16

MARMS – 112. Tail Amputation

Indications

• Trauma, bite wounds, infection, or neoplasia
• Prox enough to removal of affected tissue, but distal enough to leave functional tail
• Avoid the hemipenes

Variations

• Postygal vert autonomy (along with length of tail): Dibamidae, Anelyropsidae, Lacertidae, Cordylidae, Xantusiidae, Scincidae, Teiidae, Anguidae, and Anniellidae
• Restricted to most basal postpygal vertebrae close to base of tail: Gekkonidae
• Lack of autonomy planes in caudal vert: Agamids
• No vertebral fractures or autotomy found in Varanidae, Lanthanotidae, Helodermatidae, and Chemeonidae.
• Rare in snakes, but has been reported in some colubrids

Techniques

• If tail autonomy - aseptically scrub tail and hold base with one hand, and then use other hand to bend tail sharply laterally to effectively amputate
  
  • Alternatively, can use a scalpel to completely sever the tail.
  • Do not suture tail tip (or tail may not regrow), bandage may be applied
    
    • Can use ring-block or sedation

Question 17

Describe the use of photobiomodulation in reptiles.

How does it work?

When should it be used? When should it be avoided?

What is the therapeutic plan like?

Answer 17

MARMS – 129. Low Level LASER Therapy (Photobiomodulation)

1. Low-level laser therapy = photobiomodulation
   
   1. Laser light is absorbed by photoreceptor cells (hemoglobin, cytochrome c oxidase, melanin)
   2. Cells store energy and use it to increase the production of ATP
   3. Local and systemic effects:
      
      1. Improved wound healing
      2. Analgesia
      3. Anti-inflammatory
2. Wound Healing
   
   1. Fibroblast proliferation and migration increases collagen production, granulation tissue contraction, and improved wound strength
   2. Promotes epitheliogenesis and tissue healing
3. Equipment and Techniques
   
   1. Emission mode = continuous, chopped, or super-pulse
   2. Power = Photons arriving at tissue over time (expressed in Watts)
   3. Wavelength = ability of laser to penetrate tissues (expressed in nanometers)
   4. Class IV laser have the ability to damage eyesight
   5. Ability of laser to penetrate tissues is related to power, wavelength, and treatment time
      
      1. Also affected by skin pigment, thickness, temperature, etc.
   6. PPE for both patient and operator necessary
4. Therapeutic Effects
   
   1. Ball pythons with surgical wounds had better collagen maturation when treated with laser therapy
   2. Do not use a laser on neoplasia, as it may increase growth rate.
5. Therapeutic Plan
   
   1. Initial: Daily or every other day for 7 days
   2. Transitional: Twice weekly until condition resolved
   3. Maintenance: once or twice monthly for chronic conditions

Question 18

What are some of the common causes of digit abnormalities in reptiles?

Answer 18

MARMS – 148. Digit Abnormalities

• Commonly encountered
• Usually associated with husbandry problems
• Ischemia
  
  • Strangulation injuries from substrate, fibers, or hair
  • Dysecdysis
    
    • Inadequate environmental humidity or generalized illness
  • Can ascend and infect other digits or proximal limb
  • Amputation
• Swollen Toes & Joints
  
  • Trauma, infection, fractures, fibrous osteodystophy, gout, neoplasia, and “pseudogout”
• Twitching toes
  
  • Nutritional or renal secondary hyperparathyroidism and hypocalcemic gravid lizards
    
    • Low calcium
• Skin Abnormalities
  
  • Necrotic, sloughing, or discolored skin by be caused by burns, trauma, and ectoparasites
  • Poor husbandry