Term
| What are the eight components of a complete orthopedic exam? |
|
Definition
| signalment, history, gait evaluation, standing exam, recumbent exam (best to assess shoulder/hip range of motion), sedated exam + radiographic exam (get better positioning and less stressful for patient), any additional diagnostic tests (joint tap, MRI etc.) |
|
|
Term
| What is the most likely diagnoses for palmigrade stance in a puppy vs. adult? |
|
Definition
puppy --> flexor tendon laxity
adult --> carpal hyperextension |
|
|
Term
| What is one way to empirically distinguish neurologic lesions from musculoskeletal lesions on PE? |
|
Definition
dragging the limb (ie. weakness) is more common with neurologic lesions while limping or carrying the limb is more likely orthopedic
*** exception: disc protrusion into laterally into the brachial or pelvic plexi result in animals that carry their affected limb due to neurologic injury |
|
|
Term
| What is a positive sit test for cranial cruciate disease? |
|
Definition
| sitting with the haunches out to the side rather than square on |
|
|
Term
| What disease is associated with the patient shifting their weight forward at the walk? |
|
Definition
|
|
Term
| When evaluating lameness at the walk a patient's head will bob down on which limb, sound or lame? |
|
Definition
down on sound!
*** throwing head up when stepping on the lame leg redistributes some of the weight to the hind limbs |
|
|
Term
| Why is it important to palpate both limbs at the same time when performing the standing orthopedic examination? |
|
Definition
| this allows you to better compare muscle mass, joint distention (effusion or soft tissue thickening) and abnormal posture between limbs |
|
|
Term
| What is the easiest way to test for cranial cruciate ligament rupture in a large dog? |
|
Definition
| tibial compression and cranial thrust (cranial drawer is easier on smaller dogs) |
|
|
Term
| When over the course of the orthopedic exam should you examine the limb that you suspect is affected? |
|
Definition
| check suspect limb last for more accurate assessment of pain comparative to response to manipulation of normal limbs |
|
|
Term
| What disease should you suspect if you elicit a painful response when palpating the metaphyseal regions of long bones in young dogs? |
|
Definition
|
|
Term
| What are the anatomic landmarks for placing your hands when performing a cranial drawer test (assess integrity of CCL)? |
|
Definition
proximal hand: place thumb on fabella and index finger on patella
distal hand: place thumb of head of the fibula and index finder of tibial tuberosity |
|
|
Term
| What should you always do prior to sedated orthopedic exam? |
|
Definition
| Localize the lesion first because sedation will minimize response to painful stimulus (ie. manipulation of affected structures) **** sedated exam is best for assessing joint laxity and range of motion |
|
|
Term
| What does the ortolani test assess? |
|
Definition
| positive ortolani indicated laxity/subluxation of the coxofemoral joint which can be seen in young dogs with hip dysplasia |
|
|
Term
| What is the most common fracture etiology in vet med? |
|
Definition
| direct overloading (ex. hit by car, gunshot) |
|
|
Term
| What fracture etiology is more commonly seen in young animals? |
|
Definition
| indirect overloading (ex. avulsion from muscle contraction <-- young patients do not have completely ossified physes) |
|
|
Term
| What is the definition of a pathologic fracture? |
|
Definition
fracture occurs when bone is placed under normal physiologic stresses
*** due to structural abnormalities in the bone (ex. osteosarcoma) |
|
|
Term
| How can you distinguish a closed fracture from an open fracture in cases where there is no obvious laceration/wound (ex. puncture wounds)? |
|
Definition
| presence of gas pockets in soft tissue on radiographs indicates an open fracture |
|
|
Term
| How are open fractures further classified? |
|
Definition
grade 1: bone breaks the skin but is not sticking outside of the body
grade 2: 1-3 cm wound
grade 3: >3cm wound, extensive soft tissue trauma <-- all gunshot wounds |
|
|
Term
| What types of fractures are associated with low force trauma? high force? |
|
Definition
simple (two pieces) and segmental (three pieces) are associated with low force trauma (ex. pathologic fracture)
comminuted (multiple fragments) is associated with high impact trauma (ex. gunshot) |
|
|
Term
| What is a greenstick fracture and what age of dog is more commonly affected? |
|
Definition
| incomplete fracture that occurs when bones bend and partially break, more common in young dogs because their bone is softer and less dense than adults |
|
|
Term
| What type of force can produce a butterfly fracture segment? |
|
Definition
| transverse aka bending force, the area of compression where the force is applied is more resistant to breaking than the cortex that is being bent so the fracture courses obliquely around the point of greatest compression |
|
|
Term
| What is the difference between an oblique fracture and a spiral fracture? |
|
Definition
| all four cortices are visible on a spiral fracture |
|
|
Term
| What is the most common site of a compression fracture? |
|
Definition
| vertebral compression fractures are most common |
|
|
Term
| Fractures heal fastest through which region of a long bone? |
|
Definition
| better blood supply at the metaphysis than the diaphysis so fractures through the metaphysis heal fastest |
|
|
Term
| What is a salter-harris type 1 fracture? |
|
Definition
fracture occurs through the physis
** only occurs in immature animals with open physes |
|
|
Term
| What is a salter-harris type 2 fracture? |
|
Definition
| fracture occurs through physis and metaphysis |
|
|
Term
| What is a salter-harris type three fracture? |
|
Definition
| fracture occurs through physis and epiphysis <-- intra-articular fracture, poorer prognosis than type 1 and 2 |
|
|
Term
| What is a salter-harris type 4 fracture? |
|
Definition
| fracture through physis, metaphysis, and epiphysis <-- intra-articular fracture, poorer prognosis than type 1 and 2 |
|
|
Term
| What is a salter-harris type five fracture? |
|
Definition
| symmetrical physeal compression --> kills chondrocytes resulting in growth arrest at the affected physis |
|
|
Term
| What is a salter-harris type 6 fracture? |
|
Definition
| asymmetrical physeal compression --> chondrocytes are killed at regions of compression resulting in assmetrical physeal growth --> angular limb deformities |
|
|
Term
| How do you describe fracture displacement? |
|
Definition
| always describe displacement of distal fragment relative to proximal fragment |
|
|
Term
| What are the two types of bone matrix and what are their major components? |
|
Definition
organic <- mainly type 1 collagen + osteocytes/blasts and other structural (ex. glycosaminoglycans) and regulatory proteins (ex. BMP)
inorganic <- hydroxyapatite (CaPo4OH) and citrate |
|
|
Term
| What is the function of osteoclasts? |
|
Definition
| resorb bone (ex. after injury, or normal remodeling secondary to physiologic forces) |
|
|
Term
| Which physical characteristic of bone is attributable to the organic (structural/regulatory proteins and cells)? Inorganic (hydroxyapatite + citrate)? |
|
Definition
organic component of bone contributes flexibility but is weak
Inorganic component of bone contributes strength but is brittle
*** combined organic and inorganic components of bone are stronger per unit weight than either substance is alone |
|
|
Term
| How is the strength of bone defined? |
|
Definition
maximum load the bone can withstand before it deforms (yield point) and ultimately breaks
*** inorganic phase of bone (hydroxyapatite and citrate) contribute to the strength of bone |
|
|
Term
| How is the stiffness of bone defined? |
|
Definition
as a measure of elasticity <- can be described as the degree of displacement (deformation) of the bone in response to a given force applied to that bone
*** organic phase (cells and structural/regulatory proteins) contributes flexibility/elasticity to the bone |
|
|
Term
| When a bone breaks microscopically which histologic component is the place that fails first structurally? |
|
Definition
| bone breaks along cement lines between osteons (concentric rings of bone surrounding osteocytes, functional unit of compact aka cortical bone) |
|
|
Term
| T/F material properties of bone are independent of geometry |
|
Definition
TRUE
**** if you took a cube of cortical bone and a cube of cancelous bone and applied the same force to both, the cortical bone would have the greatest strength |
|
|
Term
| What two components of a bone contribute to its unique biomechanical properties? |
|
Definition
structural properties (ie. length, cross sectional area, distribution around neutral axis <-- is. diameter)
+
material properties (ie. cortical bone is stronger than cancellous bone) |
|
|
Term
| How does the effect of deformation differ when a force is applied quickly to a bone vs. when a force is applied slowly (ex. gunshot vs. "superman")? |
|
Definition
When a force is applied quickly (gunshot) the yield point and loading rate are higher than when a force is applied more slowly ("superman") --> the bone absorbs more energy before it breaks when force is quickly applied --> resultant fracture is more comminuted with high impact injuries
**** this property is called viscoelasticity |
|
|
Term
| What is anisotrophy and how does it relate to bone biomechanics? |
|
Definition
anisotropy refers to the directional component of the load applied to the bone
Why does this matter?
****** because osteons (functional units of cortical bone, contain osteocytes within concentric rings of bone) are always aligned parallel to the long axis of the bone, so the bone is always strongest when a compressive force is applied and weakest when a horizontal force is applied |
|
|
Term
| What biomechanical property of bone is conveyed by the term plastic deformation? |
|
Definition
| plastic deformation refers the the phase of bone deformation that occurs after the yield point has been surpassed but before the bone breaks (ie. point of maximum deformation) |
|
|
Term
| How can you calculate the amount of strain (deformation that occurs as a result of externally applied forces) on a bone? |
|
Definition
change in length/original length
Why is this important?
****** different tissues can withstand different amounts of strain before the cells cannot mantain homeostasis and die, of all the structural tissues bone can withstand the smallest amount of strain (<1%) < cartilage (10%) < granulation tissue (100%) |
|
|
Term
| If you repair a fracture without perfect anatomic allignment and take radiographs a couple weeks later why might the fracture gap look larger than your post surgical rads? |
|
Definition
small gap --> high interfragmentary strain (strain= change in gap width when an external force is applied (ie. walking)/ original length of gap)
If you increase the size of the gap (ie. the numerator) by increasing oestoclast bone resorption at the fragment ends you will decrease the overall strain on the fracture allowing osteoblasts to lay down callus and stabilize the fracture |
|
|
Term
| When a tensile load is placed on a bone what is the area that experiences the maximum stress? |
|
Definition
tensile force (ie. muscle pulling on a tendon attached to bone) causes the bone to lengthen and narrow ---> point of maximum stress occurs perpendicular to the loading force (debonding of osteons along cement lines)
*** remember osteons are arranged parallel with the long axis of the bone, so if the fracture occurs along cement lines between the osteons it's a vertically oriented fracture ie. avulsion fracture |
|
|
Term
| When a compressive force is placed on a bone what is the area that experiences the maximum stress? |
|
Definition
| compressive force (ie. hit from behind) causes the bone to widen and shorten --> maximum stress is perpendicular to the load (shear stresses cause oblique fractures in osteons) |
|
|
Term
| When a bending force (compressive + tensile) is applied to a bone, what area fails first? |
|
Definition
| bone fails first at area in tension ---> bone fractures obliquely around point of greatest compression resulting in the formation of a butterfly fragment |
|
|
Term
| What type of fracture results for a torsional loading force on a bone? |
|
Definition
spiral or oblique fracture
*** point of maximum stress is at a 30 degree angle to the neutral axis (ie. center) of the bone |
|
|
Term
| T/F the ability of a bone to resist tensile and compressive forces is a function of its cross sectional area |
|
Definition
TRUE
**** so a very wide short bone has the same capacity to resist tensile and compressive forces as a long narrow bone as long as they have the same cross sectional area |
|
|
Term
| What physical shape of bone can best withstand bending forces? |
|
Definition
Wider diameter bones (ie. cortex further from neutral axis) can best withstand bending forces because the radius of a cyclinder is the greatest contributor to it's area moment of inertia (ie. the capacity of a structure to withstand bending forces) AMI=(1/4)(pi)(r^4)
**** so the tibia will break distally because the proximal metaphysis and diaphysis have a larger diameter despite having thinner cortical bone than the distal diaphysis/metaphysis |
|
|
Term
Place these three forces in order of bone's capacity to withstand them:
tension
shear
compression |
|
Definition
| compression > tension > shear |
|
|
Term
| How do muscles help protect bones against tensile stress? |
|
Definition
| When attached muscles contract they produce compressive stress that act to neutralize the tensile stresses |
|
|
Term
| How does wolf's law relate to fracture healing? |
|
Definition
| Wolf's law states that bone either gains or looses cortical and cancellous bone in relation to the degree of stress sustained <-- this means you need to have the patient continue to use the fractured limb during the healing process because some stress is necessary to stimulate the osteoblasts to lay down new bone |
|
|
Term
| T/F the difference between a delayed union and a nonunion fracture is very subjective |
|
Definition
TRUE <- esp hard to differentiate via radiographs
**** technically a delayed union refers to a fracture where some healing is still continuing but at a slower pace then anticipated, while a non-union refers to a fracture where all healing has ceased and union is NOT possible without surgical intervention |
|
|
Term
| Why do younger animals heal fractures quicker than older animals? |
|
Definition
| younger animals have thicker periosteum (this is where the osteoblasts are located) |
|
|
Term
| What are some potential causes of delayed to non-union fracture healing? |
|
Definition
poor imombilization and inadequate reduction (ie. strain >1% at the fracture site --> surpasses bone's critical strain rate)
Impaired blood supply (esp. a problem with high energy highly comminuted fractures ---> associated with more soft tissue injury)
presence of infection
loss of bone (ie. no osteoconductive capacity at fracture site) |
|
|
Term
| What three processes are all necessary for bone healing to occur? |
|
Definition
osteogenesis <-- bone forming cells (ie. osteoblasts, located in the periosteum)
osteoinduction <-- signaling proteins that induce recruitment, differentiation, and proliferation of osteoblasts (ex. BMP)
osteoconduction <-- scaffold for osteoblasts to build off of (ex. bone allograft for large gap fractures) |
|
|
Term
| What material provides elements that contribute to all three processes necessary for bone healing (osteogenesis, osteoinduction, osteoconduction)? |
|
Definition
fresh autogenous bone graft
**** harvest cancellous bone from long bone metaphyses and illial wing/crest <-- this is the gold standard for enhanced fracture healing but is associated with donor site morbidity |
|
|
Term
| If fresh autogenous bone graft is not practical or available what other materials can be used that contain osteogenic potential? |
|
Definition
| mesenchymal stem cells derived from bone marrow or adipose <-- need to induce osteogenesis using BMP, IGF, VEGF etc. |
|
|
Term
| What are some benefits to using bone allograft over fresh autogenous bone graft? |
|
Definition
unlimited amounts, no donor morbidity, no live cells <-- decreased risk of rejection
*** but no osteogenic or osteoinductive capacity |
|
|
Term
| What two materials can be used to confer osteoinductive capacity to a graft? |
|
Definition
demineralized bone matrix <-- demineralization is necessary to activate BMP
purified BMP <-- very effective but extremely expensive |
|
|
Term
| What is the major difference in radiographic appearance between delayed union fractures and non-unions? |
|
Definition
| non-union fractures are characterized by sclerotic regions of cortical bone extending across the fracture line |
|
|
Term
| If you identify a viable non-union where the reduction of the fracture site is adequate what treatment can be done to encourage healing to resume? |
|
Definition
| apply stable fixation (reduce strain) +/- compression (plate or external fixator) |
|
|
Term
| what are four etiologies of nonviable non-unions? |
|
Definition
dystrophic (ie. poor vascular supply)
necrotic (secondary to infection and motion at the fracture site, can lead to formation of bone sequestrum)
large defect with significant bone loss
atrophic (two ends of the fracture seal over with sclerotic cortical bone to form little points <-- most commonly occurs in the ulna) |
|
|
Term
| What is the radiographic appearance of a viable non-union? |
|
Definition
either hypertrophic <-- generally the result of inadequate fracture stabilization with extensive callous deposition
Oligotrophic <-- often the result of inadequate reduction, limited callous formation, may not be viable despite surgical intervention and often difficult to differentiate from atrophic nonunion (inadequate blood supply) |
|
|
Term
| What are the principles of surgical treatment for non-viable nonunions? |
|
Definition
| reflect periosteum --> remove fibrous soft tissue and sclerotic ends of the fragments (this opens the medullary canal) --> pack fracture defect with a bone graft (ideally fresh autogenous cancellous bone) and apply stable fixation (4-6 months) |
|
|
Term
| Intramedullary pins are best at resisting what kind of forces? |
|
Definition
| bending forces (but pretty lousy at resisting tension, compression or torsion when used alone) |
|
|
Term
| How do interlocking nails allow an IM pin to become a more effective fracture stabilization method? |
|
Definition
| transcortical screws placed through the IM pin (nail) add resistance to rotational, tensile and compressive forces, in addition to resistance to bending. The screws also fix the pin within the medullary canal preventing migration. |
|
|
Term
| In what circumstance would you choose a model 22 interlocking nail over a model 11? |
|
Definition
the model numbers refer to the distance between the locking holes in the IM pin. Because it's important to fill all the holes with screws (otherwise you get a weak point in the fixation device) and it's also important to avoid placing screws across the fracture site, model 11 nails are ideal for VERY DISTAL OR PROXIMAL METAPHYSEAL FRACTURES
*** locking holes can either come (top-bottom) -> 2-2, 2-1, 1-2 (2-1 + 11 model is best for distal metaphyseal fractures, 1-2 + 22 model is best for proximal metaphyseal fractures <-- only need to fit one screw into the distal or proximal fracture fragment) |
|
|
Term
| T/F when choosing the diameter of an interlock nail it is ideal to pick the largest diamteter that will fit within the medullary canal of the patient |
|
Definition
|
|
Term
| What is an extension rod and why is it best to use the shortest one possible? |
|
Definition
extension rods connect to the top of the intramedullary nail, you attach the aiming device to the extension rod which allows you to drill holes in the bone that allign with the locking holes in the intramedullary nail
The shorter the extension rod the more accuracy when drilling the more distal holes |
|
|
Term
| Interlocking nails can be used to fix fractures in which three bones? |
|
Definition
closed fractures of the humerus, femur, and tibia
*** ends of the bones cannot be completely covered by articular cartillage ex. radius (otherwise the defect made by driving the IM pin through would result in OA) additionally the medullary cavity must be of sufficient diameter to receive the IM pin without causing fissures in the cortical bone |
|
|
Term
| What type of interlocking fixation component is better able to resist bending, screws or bolts? |
|
Definition
bolts can better resist bending because they have a larger diameter (core diameter of a screw is smaller than that of the same sized bolt because the threads contribute to the diameter) <-- only use screws if the cortex is too dense for the bolt to engage both cortices ie. large animals
*** remember AMI=resistance to bending and for a cylinder (ex. bolt) AMI is dependent upon radius^4 |
|
|
Term
| In what order should the locking bolts be placed into the IM nail? |
|
Definition
| Lock the bottom hole first (distal fragment as a greater likelihood of becoming displaced than the proximal fragment), ensure spacial allignment (rotate around IM nail if not alligned) and then lock the proximal fragment |
|
|
Term
| Which type of fracture repair heals fastest, biological or anatomic? |
|
Definition
biologic (mean healing time was 6 months, compaired to 8 months associated with anatomic fracture repair)
*** study found NO difference in complications between anatomic and biologic fracture repair surgeries |
|
|
Term
| What is the most common complication associated with the use of interlocking nails for fracture repair? |
|
Definition
| IM nail bends or breaks (10%) <-- most likely secondary to using an undersized nail or placing the interlocking hole across the fracture site) |
|
|
Term
| What is the impact of an angular limb deformity that exceeds an animals ability to compensate? |
|
Definition
| abnormal stress and strain on joints --> degenerative joint disease |
|
|
Term
| What is the most common location of the initial lesion that results in development of angular limb deformities in small animals? |
|
Definition
| distal ulnar physis <- 100% of the longitudinal growth of the ulna originates from the distal physis, when this is damaged the radius continues to grow resulting in cranial bowing of the radius with carpus valgus (lateral deviation) |
|
|
Term
| Why is the distal ulnar physis especially susceptible to premature closure ---> angular limb deformity? |
|
Definition
distal ulnar phsysis is the only physis in the body that is conically shaped and is therefore more susceptible to injury from shear forces resulting in death of the chondrocytes and premature closure of the physis
*** remember, 100% of the growth of the ulna is derived from the distal ulnar physis |
|
|
Term
| Why does cranial bowing develop secondary to premature closure of the distal ulnar physis? |
|
Definition
| because the radius grows fastest from its distal physis (60%) --> cranial bowing and carpus valgus |
|
|
Term
| What is the main clinical sign associated with premature closure of the distal ulnar physis? |
|
Definition
| pain on elbow manipulation <-- secondary to ulnar subluxation |
|
|
Term
| What four radiographic changes are appreciable on the ulnar of a dog with premature closure of the distal ulnar physis? |
|
Definition
damaged anconeal process
flattened trochlear notch
fragmented coronoid process (-->DJD)
gap between ulnar styloid and carpal |
|
|
Term
| What are the two most important goals of surgical correction of angular limb deformities of the antebrachium? |
|
Definition
re-establish elbow congruency
correct radial malalignment
*** correcting length discrepancies is less important as the animal can accomodate for up to a 25% difference in length between limbs) |
|
|
Term
| What is the surgical correction of choice for a young patient that presents with lameness and mild elbow subluxation but no angular limb deformity? |
|
Definition
distal ulnar osteotomy
**this allows the radius to continue to grow normally and removed pressure on the anconeal process eliminating the elbow subluxation, it is important to place a fat graft in the area of bone resection to prevent the ulnar from rehealing too quickly (these young patients have excellent osteogenic capacity) |
|
|
Term
| What is the surgical correction of choice for a patient with limited growth potential that presents with marked lameness and elbow subluxation but no angular limb deformity? |
|
Definition
dynamic proximal ulnar osteotomy
*** oblique cut to avoid joint capsule and interosseous ligament, the tension of the triceps tendon on the olecronon of the ulna as the muscle contracts pulls the proximal ulna back into alignment minimizing the elbow subluxation and removing pressure on the anconeal process |
|
|
Term
| When realigning the radius to correct an angular limb deformity, which bone must also be cut? |
|
Definition
|
|
Term
| How can you correct an angular limb deformity in the antebrachium without shortening the limb? |
|
Definition
| make a dome cut (as far distal as possible) <-- is allow you to correct deformity via rotation (vs. wedge osteotomy) |
|
|
Term
| What are the four elements that need to be addressed when performing corrective surgery for angular limb deformities? |
|
Definition
ALeRT
alignment
length
rotation
translation (ie. do the joints function smoothly) |
|
|
Term
| What type of fixation is generally best to use in older animals with limited growth potential after or in conjunction with surgical repair of angular limb deformities (ie. ulnar osteotomy + corrective radial osteotomy)? |
|
Definition
static fixation (ex. plate, or external skeletal fixator)
*** can also try dynamic fixation ie. distraction osteogenesis to restore length to a limb |
|
|
Term
| T/F a large amount of force is necessary to cause a joint luxation and therefore you should always thoroughly examine any animal presenting with a luxation for life threatening injuries |
|
Definition
TRUE
assess for injuries like pneumothorax, abdominal trauma/hemorrhage etc.
***** vs. congenital luxations that are generally associated with dysplastic joints (ex. hip dysplasia) |
|
|
Term
| What is the most common presentation of a shoulder luxation? |
|
Definition
traumatic luxation is quite uncommon due to extensive soft tissue support of this joint. Large breed dogs are more at risk for traumatic shoulder luxation and lateral displacement of the humerus is more commonly associated with traumatic luxations.
congenital luxation has been described in shelties and toy poodles and is associated with medial luxation of the humerous and dysplasia of the glenoid and/or humeral head |
|
|
Term
| What are some techniques for maintaining reduction of the shoulder joint following a traumatic luxation? |
|
Definition
medial displacement (more commonly associated with congenital luxation) --> medial transposition of the biceps tendon + prosthetic glenohumeral ligament
lateral displacement --> closed reduction and velpeau sling (maintains carpus, elbow, and shoulder in stable flexation) |
|
|
Term
| What is the treatment for congenital shoulder luxation (shelties, toy poodles)? |
|
Definition
excision arthroplasty or arthrodesis
**** remember, medial displacement of the humerus is more commonly associated with congenital luxation and dysplasia of the glenoid and/or humeral head |
|
|
Term
| What is the most common deviation secondary to traumatic elbow luxation? |
|
Definition
lateral or caudolateral
*** trochlea of the humeral condyle prevents the radius and ulna from luxating medially |
|
|
Term
| What joint is most commonly luxated in dogs? |
|
Definition
hip (aka coxofemoral joint)
either congenital hip dysplasia or hit-by-car (50% have concurrent major injuries, remember it takes a lot of force to instigate joint luxation, always do a throughout PE!)
**** most commonly luxated craniodorsal |
|
|
Term
| Why is it a good thing that most hip luxations occur craniodorsal? |
|
Definition
| because caudosorsal luxation has a high probability of concurrent sciatic nerve injury and ventral luxation is associated with avulsion fractures of the greater trochanter of the femur <--- both tend to require open reduction |
|
|
Term
| What are some concurrent soft tissue injuries associated with luxation of the coxofemoral joint? |
|
Definition
torn joint capsule and femoral head ligament
gluteal muscle trauma
labral (ie. cartilagenous) fractures
***** additionally young animals with open physeas can develop avulsion fractures at the femoral head where the ligament attaches |
|
|
Term
| How can the thumb test be used to diagnose coxofemoral luxation? |
|
Definition
place your thumb between the greater trochanter of the femur and the ischiatic tuberosity of the pelvis and rotate the femur ---> in a normal animal that doesn't have a luxation the greater trochanter will pinch your finger against the ischiatic tuberosity
*** definitive dx via orthogonal rads (VD and lateral) |
|
|
Term
| After successfully performing a closed hip reduction why is it important to continue to manipulate the affected limb for 5-10 minutes? |
|
Definition
This manipulation forces the hematoma and any soft tissues out of the joint space to better ensure that the joint will remain reduced
*** in fact it's so important to continue maintaining pressure on the joint that animals are then placed in an ehmer sling (abduction + internal rotation) following successful closed reduction |
|
|
Term
| What two techniques can be used to ensure that the hip remains reduced following closed reduction of a luxation? |
|
Definition
ehmer sling (abduction + internal rotation)
deVita pin (blindly drive a pin over the neck of the femur to prevent dorsal luxation <-- risk of damaging the sciatic nerve)
**** need to check these patients frequently to ensure that the joint has not reluxated. If the joint remains luxated <5 days closed reduction is no longer a viable option. |
|
|
Term
| If there's too much injury to perform a closed reduction for a hip luxation what surgical techniques can be used from an open reduction approach? |
|
Definition
capsulorrhaphy (suture the torn ends of the joint capsule together)
or if the joint capsule is too damaged can create a synthetic capsule by driving two pins into the acetebulum and running suture material around the neck of the femur and the head of the pins (think of those manilla envelopes with the original string closure) |
|
|
Term
| T/F closed hip reductions are generally very successful with a low failure rate |
|
Definition
FALSE
47-65% failure rate <-- however, closed reduction is associated with the least patient morbidity so if it's possible it should ALWAYS be attempted before open reduction (unless >5 days have elapsed since the joint luxated) |
|
|
Term
| What type of joint luxation is more common in cats than dogs? |
|
Definition
stifle
**** these are generally traumatic luxations that involve all major ligaments (cranial and caudal cruciates, medial and lateral collateral ligaments +/- meniscal detachment) REFER!!!! |
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Term
| T/F the best way to manage traumatic luxation of the carpus or tarsus is via external coaptation |
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Definition
FALSE
**** once splint or bandage material is removed the reduction fails, requires surgical therapy in the form of either primary repair or arthrodesis |
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Term
| What three elements of fracture repair should be considered to restore patient function as quickly as possible? |
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Definition
anatomic reduction (ie. allignment and apposition of fracture fragments)
internal fixation
limit external coaption (ie. splints/castst) <-- bone needs to experience some forces to stimulate healing |
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Term
| Cerclage wires can best resist what types of forces? |
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Definition
rotational +/- shear
*** must have perfect anatomic allignment and good stability until boney healing has occured otherwise repair will FAIL <-- always use with ADDITIONAL support (IM pins or plates) |
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Term
| Why should you never apply just a single circlage wire to a fracture? |
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Definition
| always apply 2 or more, a single wire acts as a fulcrum for bending forces |
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Term
| What type of fracture is best suited for repair via circlage wires? |
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Definition
| simple oblique fractures (the length of the fracture is 2 times the diameter of the bone) |
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Term
| What type of force can an IM pin best withstand? |
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Definition
bending forces
*** however NO ability to withstand rotational forces so must always be used in combination with either cerclage wires, external fixator, interlock screws or a splint |
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Term
| What is the weakest region of a physis? |
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Definition
| zone of hypertrophy <-- this region contains lots of cells and minimal amounts of matrix material and is weaker than ligamentous attachements to the bone |
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Term
| Why are physeal fractures that involve the zone of proliferation associated with a poorer prognosis than those that just involve the zone of hypertrophy (more common)? |
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Definition
| fracture healing is associated with mineralization --> if the zone of proliferation is involved in the fracture this mineralization effectively closes the physis prematurely --> can result in angular limb deformities |
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Term
| T/F knowing the salter harris classification of a physeal fracture is useful but has limited prognostic applications |
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Definition
TRUE
because ultimitely it is the histologic zone of the physis that has the greatest impact on prognosis (ie. fractures involving the zone of proliferation have are worse prognosis than those involving the zone of hypertrophy) <-- cannot determine what zone is affected by salter harris classification, need histopathology |
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Term
| What type of fracture repair is best for avulsion fractures? |
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Definition
tension bands (ie. pin and figure of eight tension band wire to fix a tibial tuberosity avulsion)
*** weak resistance to bending forces |
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Term
| When fixing an avulsion fracture using pins and a figure of eight tension band wire what is the optimal positioning for the pins? |
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Definition
| place pins perpendicular to the plane of the fracture |
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Term
| T/F screws are sized based off their outer diamter (ie. including the threads) |
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Definition
TRUE
*** this is important because you should choose a drill bit that matches the internal diameter of the screw when pre-drilling holes to place a plate <-- we want the screws to engage in the cortical bone! |
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Term
| T/F plate size is determined by the external diameter of the screw |
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Definition
TRUE
a 4.5 dynamic compression plate takes 4.5 mm screws
*** remember to predrill your holes with a drill bit that matches the INTERNAL diameter of the screw in order to ensure that the threads engage with the cortical bone
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Term
| Why is a limited contact dynamic (LC-DCP) compression plate superior to a plain dynamic compression plate (DCP)? |
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Definition
LC-DCP has evenly spaced screw holes along its entire surface while DCP has a central area with no holes (this is meant to correspond with the fracture line on the bone). The region of he plate overlying the fracture (ie. without the hole) is stronger than the adjacent regions of the plate. This creates an area of stress concentration at the adjacent hole and increases plate failure secondary to cyclic fatigue at that location.
The symmetrical design of the LC-DCP allows the load to be shared across the entire plate conferring greater resistance to cyclic fatigue |
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Term
| How do plates make use of the spherical gliding principal to induce dynamic compression at a fracture site? |
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Definition
| The plates have a small slope in the screw holes. As the screw is tightened it slides down the slope pulling the bone in that direction. Place two compression screws, one at either side of the fracture, place all the other screws in neutralization |
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Term
| How can lag screws be used to increase interfragmentary compression (and resist shear forces)? |
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Definition
| Lag screw refers to overdrilling the cis (near) cortex so that as the threads engage in the (far)cortex the two fragments are compressed |
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Term
| What are the three applications for using a bone plate for fracture repair? |
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Definition
buttress (bony column is not reconstructed, try to place the the defect under the plate <- ie. the plate is the reconstruction)
neutralization (bony column is reconstructed but all of the screws are placed in neutralization <- ie. in this case the plate supports the reconstruction)
dynamic compression (bony column is reconstructed, use DCP +/- lag screws for interfragmentary compression) <-- this is especially effective for simple transverse fractures |
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Term
| Pin-plate constructs are generally indicated for what kind of fractures? |
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Definition
non-reconstructable fractures that will require buttress plating (esp. with gap fractures affecting the trans cortex <-- this is the region of tension when bending forces are applied, and bones deform at regions of tension before they deform at regions of compression)
*** remember IM pins are best at resisting bending forces |
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Term
| When placing a bone plate, how many cortices should be secured by a screw? |
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Definition
| 6 (either at least 3 screws that span both cis and trans cortices, or some combination of biocortical and monocortical screws) |
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Term
| What are the three types of fracture healing? |
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Definition
direct (primary [contact healing w/ cutting cones] and secondary [gaps >1mm with interfragmentary strain >2%, bone resorption occurs at fracture end --> increased size of gap results in decreased interfragmentary strain, if gap is too large --->indirect healing occurs] osteonal reconstruction)
indirect (inflammation --> soft callus --> hard callus --> remodelling)
distraction osteogenesis (ie. wolf's law occurs secondary to tensile stress as well as compressive forces) |
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Term
| When dealing with an intrarticular fracture what type of healing should you aim to achieve? |
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Definition
primary osteonal reconstruction (no callus formation, less damage to articular cartilage)
**** remember, bone can only tolerate 1% interfragmentary strain, so absolute stability and anatomic reduction (gap < 1mm) is required to achieve primary osteonal reconstruction |
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Term
| How are osteoblasts and osteoclasts distributed throughout a cutting cone? |
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Definition
osteoclasts are at the front of the cutting cone (bone resorption)
osteoblasts are at the rear of the cutting cone (bone formation)
*** resorption and formation occur simultaneously at a rate of 50-80 um/day an is initiated at the ends of osteons in proximity with the fracture site |
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Term
| What are the four stages of indirect bone healing? |
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Definition
inflammation
soft callus
hard callus
remodelling |
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Term
| What processes contribute to the inflammatory stage of indirect bone healing? |
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Definition
| hemorrhage and hematoma formation -> WBC phagocytize necrotic bone and other debris/bacteria --> release of growth factors and other proteins that regulate angiogenesis and cell differentiation --> formation of granulation tissue |
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Term
| What processes contribute to the soft callus stage of indirect bone healing? |
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Definition
fibrous tissue forms at the peripheral edges of the fracture (best vascularity) while fibrocartilage forms at the center of the fracture (limited vascularity)
*** the more interfragmentary strain there is the greater the callus formation (b/c the callus functions to stablize the bone) |
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Term
| How does the soft callus of indirect bone healing develop into a hard callus? |
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Definition
| both intramembranous ossification (mineralization of the fibrous connective tissue at the periphery of the fracture) AND endochondral ossification (mineralization of the fibrocartilage at the center of the fracture) |
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Term
| What is Wolf's law and how does it relate to the remodeling phase of indirect bone healing? |
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Definition
wolf's law states that bone is formed in response to a mechanical load
*** so in order for the callus to reduce in size you must place some load on the fractured bone <-- requires months to years for complete remodeling to occur |
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Term
| What type of ossification generally occurs secondary to distraction osteogenesis? |
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Definition
| intramembranous (ie. mineralization of fibrous connective tissue) |
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Term
| What is the difference between a bone graft and an implant? |
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Definition
| bone graft inovlves the transfer of living tissue while an implant is composed of non-viable material |
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Term
| Where should you collect an autogenous bone graft from and how should you store it prior to use? |
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Definition
| collect from metaphyseal regions of long bones. Do not store graft in saline or allow prolonged exposure to air as both will kill the osteogenic cells in the graft --> ideally place graft immediately into recipient bone |
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Term
| What are some indications for bone grafts? |
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Definition
nonunion fractures
highly comminuted fractures
arthrodesis
limb salvage
**** When in doubt...put a graft in it! |
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Term
| What three principles must be followed when using indirect reduction of fracture fragments for minimally invasive fracture repair? |
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Definition
reduction of parent fragments (ie. the two biggest pieces)
re-establish limb length
realign joint surfaces
*** minimally invasive fracture repair is not appropriate for intrarticular fractures where it is paramount to minimize callous formation (otherwise, OA and DJD) |
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Term
| What are some advantages of using minimally invasive fracture repair? |
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Definition
preservation of original fracture hematoma (contains progenitor stem cell, BMP and other cytokines/regulatory proteins that induce osteogenesis) <-- preservation of original fracture hematoma is MOST important element of minimally invasive fracture repair
minimal disturbances to surrounding soft tissue structures and blood supply
decreased risk of developing post-op infection |
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Term
| What are some practical considerations that must be addressed prior to attempting minimally invasive fracture repair? |
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Definition
| benefits (decreased intra-op and healing time) can only be obtained with adequate surgen experience and equipment (intra-op C arm and radiolucent operating table, interlocking nails, external fixators, and locking plate system) |
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Term
| What are four indications for using a minimally invasive approach to fracture repair? |
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Definition
highly comminuted fracture
severe soft tissue injury
fracture is indirectly reducable (ie. NOT pelvic fractures)
need safe zones for implant insertion (ex. can't place an interlocking nail though a bone that is completely covered by articular cartilage on both ends <- ex. radius)) |
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Term
| What is the most common problem encountered when attempting to correct a fracture using a minimally invasive approach? |
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Definition
failure to achieve adequate stability
*** other problems include malreduction (parent fragment or articular surfaces mallaligned) and inadvertent soft tissue injury (ex. sciatic nerve damage when placing interlock nail into the femur or muscle/vascular injury secondary to external fixation) |
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Term
| What are the four types of external skeletal fixators? |
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Definition
Linear fixators
Circular fixators (adjustable, allows for stablization from multiple planes)
Hybrid fixators (combo of linear and circular)
Acrylic fixators (very adaptable, good for jaw fractures) |
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Term
| What are the three categories of fracture stabilization? |
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Definition
internal fixation (IM pin, cerlage wire, plates etc.)
External fixation
External coaptation (casts, splints etc.) |
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Term
| What are the three different components that are present in all types of external skeletal fixators? |
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Definition
fixation elements (engage the bone ie. smooth or threaded pins)
connection elements (connect fixation elements)
clamps (secure fixation elements to connecting elements) |
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Term
| What is the difference between threaded external fixator pins to be used in cortical bone vs. those intended for use in cancellous bone? |
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Definition
| pins for use in cortical bone have threads that are closer together (smaller pitch?) than those intended for cancellous bone |
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Term
| Where are the screws located on a pin intended for use in bilateral frame placement vs. those intended for half pin placement? |
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Definition
| pins intended for bilateral frame external fixation have threads centered in the middle of the pin while those intended for half pin placement have threads on just one end (ie. end threaded) |
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Term
| fixation wires are used in what type of external fixation devices? |
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Definition
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Term
| What are some benefits of using an olive wire rather than a smooth wire as a fixation element (circular or hybrid external fixation systems only)? |
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Definition
| the olive wires prevent the bone from sliding along the wire, and can also be used to create compression |
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Term
| What are some benefits of using external skeletal fixators for fracture repair? |
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Definition
allows for closed reduction and stablization <-- less surgically induced soft tissue trauma
no permanent implants
economical (everything but the fixation elements can be reused)
more versatile than any other method |
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Term
| What are some disadvantages to using external skeletal fixation for fracture repair? |
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Definition
Requires more aftercare by owner
Requires removal under sedation/anesthesia
Can be cumbersome by pet and by owner
Can make some forms of physical therapy more difficult to perform |
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Term
| When planning for application of an external skeletal fixator what soft tissue considerations must be made? |
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Definition
| Want to avoid placing fixation elements in any skin wounds, also want to avoid placing fixation elements through large muscles (ex. lateral aspect of the femur) |
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Term
| You can use a unilateral uniplanar external fixation connection element for what kind of fractures? |
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Definition
| adequate for most fractures where load sharing is present (i.e.transverse, short oblique, incomplete, minimally comminuted) *** IM pin can be added to increase stiffness |
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Term
| What kind of fractures can be addressed using bilateral uniplanar frame configuration? |
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Definition
| Good for fractures where load sharing is not present (long oblique, comminuted) |
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Term
| when would you use a biplanar frame configuration over a bilateral uniplanar frame configuration for external skeletal fixation? |
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Definition
comminuted fractures with extensive soft tissue injury that preclude pin placement in one plane
**** remember, we want to avoid placing fixation elements through lacerations/wounds |
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Term
| How many pins per fragment is ideal for external fixation? How should the pins be arranged along the connection elements? |
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Definition
| ideally 3-4 pins per fracture fragment, arranged to evenly span the length of the fragment |
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Term
| Where should the first pin be placed (for external skeletal fixation)? |
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Definition
| should be placed in the most proximal region of the proximal fracture segment (place a needle in the joint space as a landmark) |
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Term
| Where can you collect free (ie. non-vascularized) bone autographs? |
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Definition
| proximal humerus, shaft of illeum, ribs, proximal tibia |
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Term
| T/F When placing pins for external fixation devices you should always be sure to place the pin so that it goes engages both coritces |
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Definition
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Term
| What are the 4 A's of external fixator application? |
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Definition
Alignment-are the joints
above and below the fracture
in the same plane?
Apposition-are the fractured
bone ends close to each
other?
Apparatus-have any of the
“rules” regarding number, size
and distribution of pins been
broken
Activity-will this fixation
method allow a normal range
of activity? |
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Term
| How often should you take follow up rads after repairing a fracture using external fixation? |
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Definition
Radiographs are
rechecked 3-4 weeks
after surgery and
again at 7-9 weeks
after surgery |
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Term
| T/F a patient can return to full activity once the external fixator is removed |
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Definition
FALSE
*** reccomend restricting activity for another 2-3 weeks after removal of the external fixator |
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