Developmental Orthopedic diseases Flashcards
Growth of long bones occurs thru
endochondral ossification
-increased length primarily contributed by metaphyseal side of growth plate
Two types growth plates
- discoid-typical physis at end of long bones
2. spheroid-centers of ossification in epiphysis and cuboidal bones of carpus and tarsus
7 zones of ossification cartilage to bone
- reserve zone-resting germinal chondrocytes
- proliferative zone-chondrocytes begin to divide
- zone of maturation (hypertrophy)-weakest zone, stop dividing
- zone of calcification-matrix becomes calcified
- zone of degeneration-vascular ingrowth
- primary spongiosa
- secondary spongiosa
Physiologic closure often precedes
radiographic closure
angular deformities definition
deviations of the alignment of the boney column in the frontal plane
Most angular deformities occur at the level of the
physis
angular limb deformities are referred to by
associated joint
Windswept
foals with valgus deviation of one tarsus and varus deviation of contralateral tarsus
Offset knees
lateral position of the metacarpus down the axis of the limb
Slight valgus is protective against injury in horses with
offset knees
Rotational deformities
pidgeon toed/splay footed
no treatment
Cuboidal bones of carpus and tarsus ossify in
Last 2-3 months of gestation
- premature foals have incomplete ossification
- soft cartilage suscepible to crushing
Normal conformation of neonate
Mild to moderate carpal valgus
External rotation
Goal at weaning
Have fetlock joint aligned straight with metacarpus/metatarsus and parallel to phalangeal joints
Weanling with no carpal valgus and no outward rotation likely to
become carpal varus and internally rotated as it grows
Perinatal factors angular deformity
- Incomplete ossification cuboidal bones
- premature/dysmature/twinned foals - Periarticular laxity-should resolve in 2-3 weeks of life
- Aberrant intrauterine ossification
Developmental factors angular deformity
- Nutrition-rapid growth/excessive weight gain
2. Trauma/excessive exercise
Diagnosis angular deformity
- Stand at face of each limb separately
- Eval radius relative to metacarpus
- Eval metacarpus/tarsus relative to foot
- Eval tibial to metatarsus
The toe should be facing same direction as
face of carpus
Evaluate breakover to see if foot travels in straight line
Indicates joints are aligned parallel to ground
Monitor foals every
2-4 weeks to see if deformities are improving
Radiographs indicated in foals at risk
incomplete ossification (to start early intervention to prevent crushing)
radiographing carpus and fetlocks
Dorsal-palmar view most important
Radigraphing tarsus
Dorso-plantar and lateromedial views required
-particularly to assess for collapse of cuboidal bones
Treatments
- Hoof care starting 1 month old - valgus rasp lateral wall
- Stall rest
- External coaptation - change q 1-2 weeks, switch to bandage for a few days when rads indicate closure
Stall rest schedule
- incomplete ossification of cuboidal bones
- rest up to 1 month, re radiograph biweekly - Severe angular limb deformity w/normal cuboidals
- 4-6 weeks and sx if not corrected - Periarticular laxity with normal cuboidals
- handwalk with mare 10-20 minutes/day or swim
- typically resolves in 2 weeks
- strict rest and coaptation contraindicated
Principal indication for use of splints or casts in foals with angular limb deformity
is incomplete ossification of cuboidal bones
Splints and casts should not extend
distal to fetlock
-tendons need to take some load
Surgery indicated when
- Deformity too severe to correct spontaneously
- Deformities worsening
- Deformities causing other deformities
Classifying deformities
- mild: < 5 degrees
- moderate: 5-10 degrees
- severe: > 10 degrees
Two kinds of surgical intervention
- Growth retardation on convex side
2. Growth acceleration on concave side
Periosteal stripping/ PT
Growth acceleration
- no over correction
- growth altered for 2-3 weeks after sx
- performed when significant amount of rapid growth potential still exists
- controversial
Transphyseal bridge (TPB)
Growth retardation
- implant fixed at either side of physis, removed when correction acheived
- Screw and wire technique
- Correction can lag 2-3 weeks after placement
- can cause significant SC scarring
Transphyseal screw (TPS)
Growth retardation
- fetlock/carpus/tarsus deformities
- breach of physis causes concern for overcorrection after removal from damage
- correction begins immediately
- more cosmetic
Advanced surgical correction
- Closing wedge ostectomy
2. Step osteotomoy/ostectomy
Three common locations congenital hyperflexion
- Distal interphalangeal joint
- Fetlock joint
- Carpus
Treatment of congenital hyperflexion
- limited exercise
- oxytetracycline
- acute renal failure possible - Splinting
- splints should extend to the ground
- fetlock and carpal contracture - Heel extension
- Analgesia
- Surgery
acquired hyperflexion most often involves
coffin/fetlock joint
Acquired hyperflexion associated with
Pain as major precipitating factor, leading to activation of flexor withdrawal reflex
Possible inciting causes of acquired hyperflexion
- trauma
- joint sepsis
- chronic lameness
- physitis
- OCD
- Excess nutrition
Hyperflexion treatment
- Address nutrition if it has changed
- Controlled exercise if not too painful
- ANALGESIA
- Hoof care-gradually lower heel
- Cast-incorporate hoof, rarely used
Desmotomy of ALDDFT
Complication: excessive fibroplasia
Pressure bandage post-op 3 weeks
Prognosis if treated < 1 yr old 86% return to work
Prognosis if treated > 1 yr old 78%
Tenotomy of DDFT reserved for
severe deformities-considered a salvage procedure
Fetlock joint contracture commonly occurs
between 10-18 months of age
- growth spurt in distal radial physis
- forelimb more common than hind
- frustrating to treat
Classification fetlock contracture
Mild: < 180 degrees flexion
-fetlock remains palmpar/plantar to toe
Moderate: > 180 degrees extension when standing
-fetlock dorsal to toe but can extend to 180 when walking
Severe: > 180 degrees flexion at all times, flexor tendons and suspensory ligament are lax, extensor tendon is taught, resist further flexion
-may knuckle over if neglected
Hoofcare theories for fetlock contracture
- Heel elevation
- decrease tension on DDFT and increase strain on SDFT - Lower heel
- invoke reverse myotactic reflex - Toe extension
- prolong breakover thus stretching palmar soft tissue structures
Fetlock contracture splints
May promote laxity and stretch palmar structures at fetlock is pullback into splint
-early cases only
Fetlock contracture sx
- Desmotomy of ALDDFT
2. Desmotomy of accessory ligament of superficial digital flexor Tendon
Static cervical stenotic myelopathy tends to occur
C3-C5 or
C5-C7 (T1)
Dynamic cervical stenotic myelopathy
C5-C7 (T1)
Surgery for wobblers not until
- Thorough neuro exam
- Plain cervical rads
- Testing to rule out dz (EPM)
- Myelogram to confirm sites of compression
Factors influence prognosis of surgery for wobblers
- Number of sites of compression (3 or more is poor)
- Static or dynamic (dynamic may be better)
- Pre-operative grade (1-4) expect 1-2 grades impr
- duration of signs?
- Temperament/age/intended use of horse
Wobblers length of rehab after sx
1 yr
Wobblers prognosis after sx
60% return to intended function
88% improved at least 1 grade
60% improved at least 2 grades
Wobblers surgical procedure
Metal cylinder (basket) called Kerf Cut Cynlinder bridges intervertebral disk and joint of vertebral bodies. Stabilizes and causes eventual fusion.
Wobblers sx complications
- Seroma formation
- Infection
- Vertebral body fx
- Implant migration
- Recurrent laryngeal neuropathy
- Horner’s syndrome
- Airway obstruction upon extubation
Accipitoatlantoaxial Malformation (OAAM)
- most common in arabian foals (inherited recessive)
- small abnormal atlas, abnormally fused with occiput
- hypoplastic and malformed dens-can sublux
- Foals usually euthanised
The abnormal/lack of articulation between atlas and occuput
Often leads to scoliosis
OAAM Clinical signs
- Ataxia
- Scoliosis
- Clicking noise when head manipulated
