§  Produces elongation

§  Creates avulsion fractures

§  Occurs at apophyses (traction physes)

·         Olecranon

·         Calcaneus

·         Greater trochanter

·         Tibial tuberosity

o   Yorkies, pit bulls, etc

·         Patellar fracture

§  Skeletally immature animals

§  Opposite force of tension

§  Rare, because we fight gravity all the time

§  Vertebral bodies more common

§  Tends to create short oblique fractures

§  Bone is strongest in this mode of loading

§  E.g. running into a wall

§  Bone is weakest in this mode of loading

§  Rectangle to parallelogram example

§  Lateral condylar fracture (humeral and femoral), tibial plateau fracture, fracture of glenoid cavity, carpal and tarsal bone fractures

§  Small dogs especially (purse dogs)

§  Results in compressive and tensile forces surface (concave and convex differential)

§  Causes transverse or short oblique fractures

§  Fracture initiates on the convex surface with max tensile strength and extends to concave surface

§  Commonly diaphyseal

o   loaded in angular deformation around a central axis

§  Spiral fractures

a fracture that occurs in young animals, due to bending forces, and involving opposing cortices is called:

• involves one cortex
• usually radiate away from more substantial fractures
• result from direct forces or iatrogenic during surgical repair

Comminuted

• At least three fracture segments
• Fracture lines intersect
•  Higher kinetic energy trauma
• Multiple forces involved

Segmental

• At least three fracture segments
• Fracture lines do not intersect
• Bending and other forces
• May have large avascular segment

1. epiphysis
2. physis and metaphysis
3. physis and epiphysis (articular)
4. epiphysis, physis, and metaphysis (articular)
5. compression of physis

·         Type I

o   Clean soft tissue laceration <1cm (depending on size of patient)

·         Type II

o   Soft tissue laceration >1 cm, mild trauma, no flaps or avulsion

·         Type IIIa,b,c  

o   Soft tissue damage, up to extensive, not enough to cover wound, possible arterial supply damaged

stabilization

§  Means by which the fracture segments and frags are maintained in position

§  Major fracture segments should be maintained in functional position

·         Inflammatory phase

·         Reparative phase

·         Remodeling phase

·         Strength dependent on callus formation

·         Leave hematoma, promotes healing

• spontaneous fracture healing
• immobilization or fixation that does not provide rigid stabilization of a fracture
• inflammatory and reparative phases
• hematoma replaced by callus formation by mesenchymal cells
• cartilage replaced by bone

• precise reduction and rigid (generally internal) fixation
• Gap healing: gaps less than 200-500 microns filled by direct bone formation
• disorganized woven bone remodelled by Haversian remodeling
• Contact healing: osteoclasts form cutting cones that advance across fracture line forming resorption cavity

1. periosteal disruption results in some callus formation
2. sequential events are important, so get rads right after surgery
3. radiographic appearance of a fracture usually lags behind clinical signs
4. character and amount of callus is important in distinguishing normal fracture healing from osteomyelitis

under compression in presence of O2-->bone

under compression without O2-->cartilage

under tension-->fibrous tissue

1. to enhance fracture healing (complex, delayed union, nonunion)
2. to replace areas of bone loss arising from excision of neoplastic lesions, osteomyelitis, trauma, cysts
3. to stimulate bone fusion in arthrodeses

cancellous (autogenous)-proximal humerus, ileum, proximal tibia

cortical (allograft or autogenous)-ribs or ulna

corticocancellous bone 

1. osteogenesis-new bone formation directly from graft osteoblasts or graft osteoprogenitor cells. only from fresh autogenous
2. osteoinduction-recruitment of pluripotent osteoprogenitor or mesenchymal stem cells
3. osteoconduction-acting as scaffolding for ingrowth of vessels and migration of osteoblasts and precursors
4. immediate-structural support is provided only by cortical grafts when they are incorporated into rigid fixation of fracture defect

§  Callus expected to be evident in 2-4 weeks

§  Fracture line may initially widen

• direct visualization
• significant trauma to fracture and surrounding tissue

1. type and location of fracture
2. single vs multiple fractures, concurrent ortho abnormalities
3. signalment
4. concurrent soft tissue damage
5. behavior and use of animal

• intramedullary fixation
• cerclage wires
• screws
• plates

• coaptation (casts, splints, bandages)
• external fixators

• limit limb function
• still a substantial amount of motion at fracture site
• require constant monitoring/changing
• animals tend to destroy them
• can induce fracture disease with prolonged use

§  Generally requires sedation or anesthesia

1. §  Radiograph the limb following application
2. §  Take two orthogonal view radiographs
3. §  Include joint proximal and distal to injury
4. §  1. White tape stirrups with tongue depressors
5. §  2. Spread toes (to accommodate swelling) and leave exposed
6. §  3. Rigid pre-formed splints: pad depression (more padding)
7. §  3. Malleable splints: pad protuberances (less padding)
8. §  4. Apply cling snuggly, turn stirrups back up to prevent sliding down

§  Temporary immobilization of musculoskeletal injuries

§  Fractures (particularly young animals) (bc heals quickly, less time in cast)

§  Fractures of distal extremities

§  Simple, relatively stable fractures

§  Ligament and tendon injuries (without or post surgery)

§  Temporary immobilization

§  Prevent swelling and further displacement

§  Injuries distal to humeral condyle

§  Injuries distal to femoral condyles

§  “spoon splints”

§  Injuries distal to carpus and hock

§  Inappropriate for fractures of radius and ulna

§  Prevents weight bearing

§  Used for scapular fractures, some shoulder injuries and as non-weight bearing sling for forelimb

§  Prevents weight bearing

§  Hock, thigh, hock

§  Flexes, abducts and internally rotates hip

§  Used following reduction of coxofemoral luxations

§  Non weight bearing

§  Stifle and hock maintained at 90º

§  Used to prevent quad tie down by maintaining the quadriceps mechanism in extension

• lateral coaptation that extends from digits to over midline. 
• forelimb injuries including and proximal to elbow
• e.g. elbow luxations, some scapular humeral luxations, scapular fractures and occasionally humeral fractures. 
• rarely hindlimb

• aluminum rod traction splint
• walking splint with padded elliptical ring around groin or axillae with rods projecting distal to paw
• often misused/abused: can act as fulcrum against fracture
• for fractures distal to elbow and stifle
• risk of strangulation and loosening

• prevents weight-bearing on forelimb
• allows movement in shoulder and elbow
• carpus maximally flexed and bandaged

·         Can be used as primary or adjunctive stabilization

·         Comminuted fractures

·         Open fractures

·         Infected and nonunion fractures

·         Arthrodesis

·         Transarticular stabilization

·         Limb deformities

o   Type 1

§  Utilizes half pin splintage (pins pass thru both cortices of bone but only on skin surface) and is uniplanar and unilateral

§  Pins loaded in cantilever bending

o   Type 2

§  Utilizes full pin splintage (pins pass thru both cortices of bone and two skin surfaces) and is uniplanar but bilateral

§  Pins loaded in four-point bending, more stability

• Type 3- full and half pin spintage. biplanar

·         Half and full pin

·         Easier to apply with comparable stability

·         heavy gauge stainless steel wire placed circumferentially around bone to provide fragment apposition and adjunctive fixation

·         must be open reduction

·         some rotational, bending, shearing force neutralization, some fragment apposition. But ADJUNCTIVE

• no

·         resistance to axial rotational, bending and shear forces is dependent on the frictional forces generated when interdigitating intricacies of the fracture surfaces are statically compressed, thus complete 360º anatomic reconstruction is mandatory

§  both phases of application occur simultaneously (tighten and secure)

§  limits wire tension bc wire is bent before it is tight

§  twist to braid, not to wrap around. Apply traction while twisting

§  leave 3 twists, do not bend tail down (lose tension). Will stick out into soft tissue, careful where you leave it

§  wants to sit oblique, so position as you tighten down.

§  Provide greater resistance to distractive forces

§  Simpler to apply

§  Can be re-tightened

§  More economical

§  More cumbersome to apply for some people

§  Final tension not as good

§  Twist protrudes into soft tissue

§  wire tightened and subsequently secured by bending

§  wire pulled thru single plane during application

§  wants to sit perpendicular, unlike twist knot

§  tighten with rocket, bend 90º, cut end.

§  greater tension than twist knots

§  does not protrude into soft tissue

§  cannot re-tighten

§  more cumbersome to some to apply

§  increased cost compared with twist wires

pin and tension band fixation

§  converts distractive forces to compressive forces

§  tensile forces on protuberances

§  tensileàcompressive forces

equal and opposite force with figure 8 wire

Name the weakest link in the external skeletal fixation system, and how this relates to 

postoperative morbidity. 

o The weakest link in any external skeletal fixation construct is the bone-pin 

interface, pin design and application have a substantial effect on the 

stability of the bone-pin interface

List the attributes which make external skeletal fixation an excellent choice of 

immobilization for comminuted fractures

o It keeps the comminuted fracture from collapsing because each segment 

can be fixed to the external rod by pins.

o The apparatus and the bone are bearing the weight

• affords the surgeon greater latitude in fixation pin placement because the 
• fixation pins need not all be aligned in the same longitudinal plane, can use any pin diameter because not constrained by connecting clamp, most acrylics are 
• radiolucent which facilitates postop assessment of reduction and fracture healing, 
• light weight so encourages an early return of function
• inexpensive

• Normograde-pin is inserted at one end of the bone, driven across the fracture and seated in the opposite metaphysic
• Retrograde-pin is inserted at the fracture site and driven proximally or distally through the metaphysic and/or epiphysis

§  Trocar (sharp, cuts bone) (most common)

§  Threaded (partially) NO PLACE IN VETMED FOR INTRAMEDULLARY PINNING (cancellous bone won't hold threads) (stressed, can break) (NO, NO, NO!)

§  Chisel (two sided) can be used if you want to deflect off endosteal cortex

• Sepsis
• In comminuted fracture alone, but may be combined with cerclage wires
• If there is excessive motion at the fracture site
• Fractures of the radius 

State the forces Steinmann pins effectively counteract

• fumes produced during polymerization of the acrylic are toxic, 
• reduction is difficult to maintain if acrylic column is used as primary stabilization because of lack of rigidity of the system until acrylic is hardened, 
• more appropriately sited to be used as adjunctive stabilization
• exothermic; can burn
• can't remove an individual pin if need be

• smaller core diameter=less resistant to bending forces
• thread-smooth interface is a stress concentrator, especially if near the cortex

twist drill for pilot hole

low speed, hi torque (hi speed will thermal necrose bone)

most distal and proximal first, then work towards center

ideally, 70 degrees to long axis of bone especially with smooth pins

o   1. Proximal epiphyseal/metaphyseal cancellous bone

o   2. Endosteal surface of diaphysis

o   3. Distal epiphyseal/metaphyseal cancellous bone

1. Type I: adjunctive in combination with intramedullary pin, which is left protruding through skin and "tied in" to connecting frame. 
2. Type II: limited to use below stifle or elbow. difficult to line up all pins on same plane. sometimes only proximal and distal pins are full-pin splintage and negative profile. very stable
3. Type III: used in very large patients with highly unstable fractures. most stable configuration. 

padding between skin and connecting bar

sterile nonadherent gauze over open wounds

wrapped to minimize soft tissue movement

skin-pin interfaces cleaned regularly with saline or chlorhex

recheck every few weeks

• tension side
• min 2-3 screws
•  minimum distance from the fracture line: 5mm or 1 screw diameter

§  cortical

·         thicker core

·         more threads

§  cancellous (softer)

·         steep pitch

·         fewer threads

§  plate

·         fasten an implant to bone

§  positional

·         holds fragment in fixed position

§  lag

·         provides compression

·         Axial compression is accomplished by inserting eccentrically the first screws on either side of the fracture line

§  Compression

·         Tension band plate

·         Self compressing

§  Neutralization

·         Protection of other fixations

does NOT provide compression

§  Bridging (buttressing)

·         Plate bridges the fracture area

bone column NOT reconstructed

never applied with compression

·         Open fractures

·         Across growth plate

·         Limited finances

·         Small fracture fragments

·         Limited experience of surgeon

o   Compression

§  Simple transverse, short oblique fractures

o   Neutralization

§  Used in oblique fractures

o   Bridging

§  Comminuted

• Palpable instability at fracture site
• Muscle atrophy
• Limb deformity
• Impaired limb function
• Variable pain, lameness
• Fracture margins distinct
• Pseudoarthrosis
• Sealed marrow cavity
• Serial evaluation reveals arrest or regression of healing

·         Biologically active (viable)

§  Close to delayed union

§  Hypertrophic, slightly hypertrophic, oligotrophic

·         Biologically inactive (non-viable)

§  Dystrophic, necrotic, defect, atrophic

§  Acute

·         Lameness, swelling, heat, pain, pyrexia

§  Chronic

·         Lameness, swelling, pain, muscle atrophy, drainage

what is an involucrum?

cloaca?

periosteal reaction around a sequestrum.

opening in involucrum. 

Atrophy of bone and soft tissues with resultant fibrosis and degenerative joint disease associated with healing fractures

soft tissue trauma, ischemia, instability, swelling, deformity, loss of function, etc. 

• Rigid extension of the affected limb (usually prevents stifle from bending, and limb carried cranially)
• stifle may be bent in genu recurvatum (caudally)
• muscle atrophy and leg shortening
• Associated with femoral fractures in immature dog
• caused by soft tissue trauma, instability, and prolonged improper immobilization

useful in short oblique or transverse diaphyseal fractures. 

provides multiple points of fixation and thus increase rotational stability.

multiple (5) pins are inserted, then more pins inserted in the center to push the original pins against the cortex

smaller diameter, more elastic

intramedullary or transcortical pins in small dogs and cats, pin and tension band fixation, and cross pins

• specially tempered, round intramedullary pins that are elastic
• used in pairs for metaphyseal region fractues.
• dynamic three-point fixation
• no attempt to fill medullary cavity
• not often used in vetmed, but Kirschner and Steinmanns used in this nature

• nails positioned within medullary cavity centrally, not eccentrically like plates
• resists bending and axial and rotational forces
• humerus, femur, tibia
• placed in limited open reduction (or closed or open), and highly comminuted fracture segments do not have to be anatomically reconstructed. 
• good for delayed and nonunion fractures
• At least one screw proximal and distal to fracture
• economical
• application fast and simple

• Pins are inserted at angle such that pins deflect off endosteal cortical surfaces,
• May provide added strength 
• Cross PROXIMAL to fracture
• Commonly used in metaphyseal or physeal fractures

§  Preferably normograde placement

·         Just medial to greater trochanter

·         AVOID sciatic nerve

·         Push laterally and cranially in fossa, then advance down

§  Over reduction (straighten it out a little to implant straight implant into a curved bone. A little gapping, but will heal, implant will seat well) (dogs especially)

·         Allows better purchase distally

·         Prevents anatomic reconstruction

·         Easily augmented with external fixation

§  Normograde (unless in cat, you can do retro)

·         Craniomedial aspect of tibial plateau

·         Extra-articular, cranial to menisci

§  Do not enter hock distally

·         Cut off the tip of the pin

§  Retrograde (but also can do normograde)

§  exits proximally through greater tubercle

§  seated distally in or proximal to medial portion of condyle

§  Not amenable to intramedullary fixation

§  Don’t do it

§  Stress pinning of physeal fractures is acceptable

§  Retro or normograde

§  Rarely sufficient as sole means of stabilization

§  Incorporated with tension band technique

§  Used to supplement radial repairs

§  both phases of application occur simultaneously (tighten and secure)

§  limits wire tension bc wire is bent before it is tight

§  twist to braid, not to wrap around. Apply traction while twisting

§  leave 3 twists, do not bend tail down (lose tension). Will stick out into soft tissue, careful where you leave it

§  wants to sit oblique, so position as you tighten down.

§  Provide greater resistance to distractive forces

§  Simpler to apply

§  Can be re-tightened

§  More economical

§  More cumbersome to apply for some people

§  Final tension not as good

§  Twist protrudes into soft tissue

§  wire tightened and subsequently secured by bending

§  wire pulled thru single plane during application

§  wants to sit perpendicular, unlike twist knot

§  tighten with rocket, bend 90º, cut end.

§  greater tension than twist knots

§  does not protrude into soft tissue

§  cannot re-tighten

§  more cumbersome to some to apply

§  increased cost compared with twist wires

• repair of long bone fractures, at or near the metaphysis where the bone changes diameter
• passed through holes drilled through adjacent cortices. 

e.g. figure-of-eight

§  converts distractive forces to compressive forces

§  used to stabilize osteotomies and fractures at traction apophyses

§  tensile forces on protuberances

§  tensileàcompressive forces

pins placed parallel to each other and perpendicular to the fracture line

1. anatomic reduction
2. stable internal fixation
3. atraumatic technique of bone and soft tissue manipulation
4. early pain-free active mobilization after surgery

1. plate on the tension side of the bone
2. appropriate size plate and screws
3. a minimum of 2-3 screws, 4-6 cortices per fragment
4. plate applied directly on the bone
5. min distance from the fracture line: 5mm or 1 screw diameter
6. plate is contoured to the bone shape and surface

• location near joint interfering with function/range
• loose implant
• infection
• in cold environments, superficial plates get cold
• potential for corrosion
• stress protection (Wolff's law says you should let natural forces strengthen the bone. plates will atrophy the bone)

• adequate interval of time for fracture healing but healing incomplete
• healing progressing but slower than expected
• long bones should heal by 3-4 months in adults, 1-2 months in puppies

• hyperparathyroidism
• hyperadrenocorticism 
• DM
• renal disease
• intestinal malabsorption

poor vascularity.

instability and subsequent motion.

• dx by serial radiographs
• autogenous cancellous bone graft
• vascularized graft
• bone forage
• if inadequate/interrupted fixation, use more rigid fixation (e.g. plates and screws)
• if infected: remove implants to resolve osteitis and osteomyelitis

·         Biologically active (viable)

·         Biologically inactive (non-viable)

§  Hypertrophic- abundant hypervascularized callus, unstable fracture

§  Slightly hypertrophic-inadequate callus, mild sclerosis of medullary cavity, rotational instability

§  Oligotrophic-no visible callus, ends of medullary cavity sealed at fracture site, rounding of fracture ends, fibrous tissue and blood vessels between fragment edges, still capable of biological response. Significant displacement of fracture fragments

• Dystrophic-secondary fragment has healed, main fragment unhealed and devoid of callus
• Necrotic-highly comminuted fractures in poorly vascularized areas. major fragments eventually die without being incorporated in callis
• Defect-loss or resorption of fragments
• Atrophic-above 3 can lead to this type, significant bone resorption and osteoporosis

• osteitis, osteomyelitis
• drainage from one or more fistulas
• periosteal new bone formation and lucency, especially around implants
• sequestra and implant loosening

• infection
• inadequate reduction
• soft tissue disruption
• inadequate internal fixation

inadequate blood supply

takes longer to reestablish 

• sclerosis of bone ends at fracture site
• no bony progress or change over 3 month period
• progressive bowing at fracture site
• bone atrophy
• excess callus around fracture site with radiolucent lines in the callus itself

nuclear scintigraphy. 

photopenic (cold spot) because of decreased or absent radiopharmaceutical uptake at fracture site

• rigid internal fixation
• opening of sealed medullary cavity followed by autogenous bone grafting and rigid fixation

• removal of all necrotic and avascular bone, 
• opening of medullary cavity, 
• autogenous cancellous bone grafting. 
• rigid fixation

inflammation of cortex and marrow components

can be:

1. hematogenous in foals,
2. spread from adjacent soft tissue,
3. penetrating wound,
4. secondary to fracture repair

• failure of host tissue cells to integrate with surface minimizes effects of local defense mechanisms
• provides surface for biofilm which further isolates bacteria from host defenses

• high concentraiton of prophylactic antibiotics during surgery
• minimize surgery time 
• thorough soft-tissue and bone debridement
• irrigation/hydration intra-operatively
• culturing at conclusion of surgery

don't forget drainage and debridement

penicillin for gram positive with amikacin or gentamicin for 4-6 weeks.

• 3-4 perfusions. often with systemic antimicrobial administration and debridement. requires tourniquet proximal to infected area.
• intraosseous and IV regional perfusions used. 
• antibiotic-impregnanted beads (PMMA)
• penicillins, AG, cephalosporins (bactericidal at low doses, water-soluble, powdered form, heat stable)

angular

rotational

distracted

over-riding

1. impaired limb function
2. stenosis of pelvic canal
3. jaw malocclusion
4. patellar luxation

• blastomycosis
• cryptococcus
• nocardia
• actinomyces
• coccidiomycosis

• soft tissue swelling
• irregular periosteal reaction
• long zone of transition
• may be difficult to distinguish from normal healing bone or bone tumor
• sequestrum

• early fracture treatment
• rigid fixation
• early return to function
• 90-90 sling

A. normal bone

B. callus

C. involucrum

D. cloaca

E. sequestrum

• cannot place positive profile pins directly thru clamps
• pre-drilling pilot hols difficult
• difficult to place series of parallel full-pin splintage pins
• not radiolucent
• limited diameter pins
• connecting rod is relatively weak

increased stability with less complex frames

no need for double connecting bars

§  Preserve local fracture environment (vasc supply)

§  Bridging osteosynthesis (external skeletal fixation, plates, or intramedullary fixation)

§  Approaches: closed or limited open reductions

§  Trend over past decade to move away from anatomic reconstruction to biologic approach