Musculoskeletal System Flashcards
What are the phases of bone healing?
- Inflammatory phase
- Repair phase
- Remodelling phase
What are some general clinical signs of a fracture?
- Loss of function
(lameness) - Swelling
- Change in limb
length, alignment, or orientation- Affected limb is
usually shorter
- Affected limb is
- Abnormal range of
motion (ROM)- Reduced or increased
- Pain
- Crepitus
- Sensation of bone
grating against bone (crunching, grinding feeling)
- Sensation of bone
What factors does bone healing require?
- Adequate reduction and stability of the fracture site
- Allows for vascularisation of the fracture site (allow capillaries to grow in) and protects the bone cells in the fracture gap
- Absence of complicating factors
- Infection, for example
- Sufficient healing time
Describe bone gap healing.
- Seconary or indirect healing though callus formation
- Occurs with small gaps between fracture ends
- Occurs with minimal movements
- Lamellar bone forms directly in the fracture gap
- Intracortical remodelling through the fracture gap restores bone
What factors are required to describe a bone fracture?
- Aetiology
- Bones involved
- Position within bone
- Direction of fracture line(s)
- Number of fracture line(s)
- Relative displacement of fracture fragments
Describe an impacted fracture. How is it likely to be managed?
- Closed fracture that occurs when pressure is applied to both ends of the bone, causing it to split into two fragments that jam into each other and causes interlocking of cancellous bone
- Often stable and can be managed conservatively
What factors determine the frequency of radiographic views taken surrounding bone fracture repair and management?
- Baseline views must be taken pre-operatively for fracture fixation planning and immediately post-operative to assess repair
- Frequency of views above baseline is governed by:
- Anticipated rate of healing
- Presence of complicating factors
- Finance
- Intention to remove implants
What is immediate first aid advice to give to a pet owner who has a pet with an open fracture?
- Prevent contamination by covering open wounds
- Control haemorrhage
Describe the steps for treatment of an open fracture wound patient upon arrival to the hospital.
- Priority first line treatment upon entry to the hospital:
- Clip fracture area widely
- Lavage copiously with sterile saline or tap water from a shower head
- Debride all devitalilsed tissue
- Start open wound management
- Stabilize fracture and manage soft tissue injuries
- Prevent contamination progressing to infection
- Achieve rapid bone union and restore limb function
Describe biological osteosynthesis.
- Bone healing philosophy which aims to take full advantage of biological healing potential to maximize rate of fracture healing and create an optimal biological and mechanical environment for fracture repair
- Requires
- Maintenance of limb length and orientation
- Avoidance in creating further surgical trauma
What type of fracture support is a splint? In what cases is a splint indicated?
- External coaptation
- For short-term use or adjunctive support
- Okay for use in radius and ulna
- Limited used to distal hock
- Should be applied over cast padding and conforming bandage with spoon at the bottom
What are casts and when are they indicated for use? What types of casts are available and what are the advantages/disadvantages of each?
- Casts are a type of external coaptation which immobilizes a fractured joint above and below the fracture
- Indicated for fractures if expected healing time is within 6 weeks and fractures that are not under axial force as a cast does not counteract axial forces to fractured bone
- Types
- Plaster of Paris cast
- Cheap
- Easy to apply
- Conform well
- Take 8+ hours to dry fully
- Heavy to wear
- Radiodense
- Cannot get wet
- Fibreglass/resin casts
- Light and strong
- Does not soften when wet
- Conforms well
- Sets rapidly
- Radiolucent
- Requires an oscillating saw for removal
- Plaster of Paris cast
Give an example of an anatomical moulded splint.
- Splint made from thermoplastic materials
- Stronger and lighter than plaster of Paris (POP)
- Material needs to be quite hot before applying
- Can be awkward to use
Describe the steps in cast application for a fracture.
- Reduce fracture and maintain reduction
- Immobilize joint above fracture
- Immobilize the limb in a normal standing position
- Include the toes and, possibly, pads in the cast
- Cast should be applied with a 50% overlap with up to 6 layers
- Wait until cast is cured before allowing injured animal to walk
- Limb alignment should be assessed radiographically
Why do casts often require changing before bone union is complete?
- Swelling reduction changes the fitting of the cast on the limb
- Cast damage
What are some possible complications with cast use?
- Soft tissue complications
- Pressure sores can be caused due to poor cast application technique or loosening
- Ischemia can be caused which may progress to gangrene
- Fracture disease
- Muscle wasting, stiffness, osteoporosis, or tissue adhesion, for example
- Malunion
- Delayed union
- Dressing which is applied too tightly can cause a closed fracture to become an open fracture
Describe the application of bone pins for an external fixation system surgery.
- Suspend the injured limb from hooks in the ceiling (radius and tibia) or with an intravenous stand (humerus and femur).
- Scrub the liberally clipped area with an antiseptic soap.
- If the fixation is being applied to the radius or tibia, leave the limb suspended during application of the external fixator. If the fixation is being applied to the humerus or femur, release the limb from the suspension after it has been draped.
- Make a small (1-cm) longitudinal skin incision over the proposed pin site.
- Use a hemostat to dissect bluntly through the soft tissue from the skin surface to the bone to create a soft tissue tunnel that allows free gliding motion of surrounding muscles around the fixation pin. The tunnel also prevents the pain and discomfort that can result from impingement of soft tissue against fixation pins. Create the soft tissue tunnel between large muscle bellies rather than through them, and avoid neurovascular structures.
Protect the soft tissue in the walls of the tunnel from trauma using a drill sleeve, or retract and stabilize the tissue with a hemostat. - Predrill the bone using a high revolutions per minute (RPM) speed drill and a twist drill bit 0.1 mm smaller than the core diameter of the fixation pin.
- Place the fixation pin through the drilled hole with a power drill, using low-
RPM speed. - Be sure the pin tip extends beyond the opposite cortex.
What are the factors invovled in pin selection for the application of external skeletal fixation.
- Patient fracture assessment score
- Bone cortical width
- Pin should be 20-25% cortical width
- Length of bone fragments
Describe how external skeletal fixation is compatible with the principles of biological osteosynthesis.
- Maintains alignment and lengths of limb
- Minimally disturbs fracture fragments
- Closed or minimally invasive application possible
- All fracture forces can be neutralized
- Encourages early weight bearing
What are some complications which may arise with the use of external skeletal fixator pins?
- Persistent pin tract drainage
- Best avoided by attention to soft tissue management
- Cannot be avoided at some sites
- Pin loosening
- Promotes pin tract discharge
How is the diameter and the length of the intramedullary pin selected for fracture repair?
- Diameter
- Should be selected to fill in the medullary canal at narrowest point. Radiographs of contralateral limb useful for assessment (allow 10-15% for magnification of radiograph)
- Length
- Pin should be seated in distal metaphysis and protrude slightly proximally for easy removal after healing
What are the methods of insertion of an intramedullary bone pin? Describe them. Which bones can each method be used on?
- Retrograde pinning
- Expose the fracture and insert the pin into the medullary canal of the appropriate bone segment. Drive the pin to exit the bone segment. Reduce fracture by driving pin across fracture line
- Can be done on humerus, femur, tibia and ulna
- Normograde pinning
- Inroduce the pin at the appropriate location at one end of the long bone and drive it down the medullary canal to the fracture to reduce the fracture. Continue to drive the pin until it seats in metaphyseal bone.
- Can be used for open or closed fracture
- Can be done on humerus, femur, and ulna
Describe the orthopaedic repair interlocking nail.
- Intramedullary pin which has been perforated to accept bone screws
- Neutralises all forces very effectively
- Pin resists bending
- Screws lock bone to pin resisting shortening, rotation, and shear force
- Can be technically challenging to use as requires specialized instrumentation or fluoroscopic guidance for use
What is a rush pin? How is it used?
- Type of intramedullary pin with a hooked end and ‘sledge runner’ tip
- Used in pairs
- Useful for metaphyseal fractures
- Useful especially for distal femur fractures
- May allow physeal growth to continue in skeletally immature animals
What is cerclage wire and how is it used?
- Monofilament orthopaedic wire commonly combined with intramedullary pinning
- Can be used with full cerclage or hemicerclage
- Requires wire twister and cutter for use
- Uses
- Provide interfragmentary compression
- Reduces the fracture gap
- Increases interfragmentary friction
- Enhances fracture stability
- Stops undisplaced fissures from opening up or propagating from the fracture site
How many twists should there be in an applied circlage wire?
3-4 twists
Describe the application of tension band wiring to a bone fracture.
- Reduce fracture and maintain with one or two Kirshner-wires
- Circlage wire is anchored in a transverse bone tunnel and passed around the ends of the pin(s) in a figure-of-eight fashion
- Wire is anchored by twisting bilaterally to ensure even tension
- Ends of the Kirshner wires are bent over and cut short
What are some options for bone internal stabilization post-operative care?
- Controlled exercise for rapid return to normal weight bearing and avoidance of muscle-wasting and joint stiffness (especially important following articular fracture repair)
- Physiotherapy
- Passive flexion-extension exercises
- Hydrotherapy
Describe what the arrows are pointing out in the the following dorsomedial-planterolateral oblique radiograph of a metatarsal region of a Warmblood gelding:
There is a large
oval-shaped sequestrum (black arrow)
surrounded by a relatively radiolucent area axially (an involucrum) with
periosteal new bone (white arrows) consistent with osteomyelitis. Note
the variable radiopacity of the overlying soft tissues.
What are the radiographic features of osteomyelitis?
- Bone destruction
- Periosteal new bone formation
- Results in an irregular, “fuzzy” appearance to the bone
- Possible soft tissue swelling
- Sequestrum formation
- Surrounded by radiodense and angular bone formation
- Devascularisation of a portion of bone with necrosis and resorption of surrounding bone leaving a ‘floating’ piece which acts as a reservoir for infection (avascular is not penetrated by antibiotics)
- Involucrum
- Thick sheath of periosteal new bone surrounding a sequestrum
- Delayed healing or non-union
What is a radiographic sign of a viable hypertrophic non-union fracture? What can be done to improve the healing?
- Significant callus is indicative that non-unionised bone is attempting to heal
- Treatment of hypertrophic non-union fracture
- Remove loose implants and stabilize fragments
- Acquire fracture culture and sensitivity
- Use of bone graft (does not usually require a bone graft)
What creates a non-viable, dystrophic, non-union fracture?
Inadequate blood supply
What are the radiographic signs and treatment options of an atrophic, non-viable, non-union bone fracture? In which bones are these commonly found?
- Radiographically shows no evidence of attempt to heal (biological inactivity)
- Bone ends are sclerotic and atrophied
- Medullary cavity may seal over
- Fracture gaps fill will fibrous tissue
- Formation of pseudoarthrosis
- Treatment (aggressive)
- Open approach to be used
- Debride fracture ends to viable bleeding bone
- Tissue samples for culture and sensitivity
- Bone healing has to be stimulated
- Requires rigid stabilization with plate and screws
- Common in distal radius and ulna in toy breed dog
- Final sequel of a non-viable, non-union fracture repair
What is quadriceps contracture? How can it be avoided and how may it be treated?
- Quadriceps muscle becomes adherent to fracture site which leads to:
- Progressive decrease in range of stifle joint mobility
- Stifle and hock overextension
- Is avoided by avoiding penetrating muscle masses during external skeletal fixation (ESF) whenever possible
- Treatment
- Surgical release of adhesions
- Muscle/tendon lengthening if necessary to allow normal range of motion (ROM) at stifle joint
- Passive and active physiotherapy are vital following surgical correction
What causes bone implant failure?
- Combination of biologic and mechanical factors that lead to implant loosening or breakage over time
- Inappropriate implant size selecton
- Errors in implant placement
- Infection
- Patient comorbidies (obesity, for example)
- Discord in biomechanical environment
- Cyclic loading
- Large cortical defects
- Fracture of plates through unfilled holes
What is a bone autograft? Where is it collected from? What are the advantages/disadvantages of using this bone graft?
- Bone graft taken, usually from cancellous bone, in which the donor and recipient is the same individual
- Highly cellular but mechanically weak
- Collection from
- Lateral tuberosity of humerus
- Medial proximal tibia
- Greater trochanter of femur
- Wing of ilium
- Advantages
- No immune response
- Greatest osteogenic effect (high cellularity)
- No risk of cross infection
- Disadvantages
- Extra operating sites must be prepped and accessed
- Large quantities can be difficult to obtain
- Must be kept in moist swab in surgical area until use
What is a bone allograft? From where is it usually taken? What are the advantages/disadvantages of its use?
- Donor and recipient are animals of the same species
- Main use is for limb salvage
- Usually taken from cortical bone
- Advantages
- Can be banked
- Convenient
- Unlimited quantity available
- Disadvantages
- Immunogenic
- Slow incorporation into host bone (3-4 years)
- High risk of cross infection
- Surgery requires strict asepsis with implantation of dead bone
What is a bone syngenesiograph?
Bone graft in which the donor and recipient are blood relatives
What is a bone isograft?
Bone graft in which the donor and the recipient have identical genetic background
What is a bone xenograft?
Bone for which the donor and the recipient are from different species
Describe the mechanism of action of a bone graft.
- Sources of osteopregenitor cells arise from:
- Within the graft (Osteogenesis)
- The surrounding tissue (Osteoinduction)
- Provides a mechanical support such as a scaffold for bone cell invasion (Osteoconduction)
What are the uses of bone grafting?
- Filling defects
- For limb salvage, for example
- To encourage healing
- In a comminuted fracture, non-union, or arthrodesis, for example
Describe the radiographic assessment of suspected hip luxation.
- Two orthogonal views should always be taken
- Check for pelvic or avulsion fractures which may stop reduction
- End of femoral head may be resting in the acetabulum (avulsion)
- Assess for the presence of hip displasia which makes closed reduction less likely to succeed
- Check for shallowness of acetabulum which make reduce the stability of the hip after healing
Describe the use of the Ehmer sling for closed reduction of coxofemoral luxation. What important factors must be considered for use?
- Prevents weight bearing on repaired limb
- Maintains internal rotation of the femur and enhances hip stability
- Correct application is critical to avoid vascular compromise
- Difficult to maintain on cats
When is coxofemoral open reduction indicated?
- Failure of closed reduction
- Re-luxation
- Acetabular fracture
- Significant hip dysplasia (HD) or osteoarthritis (OA) present
- Contralateral limb injury
Describe the application of the iliofemoral suture. In which surgery would this procedure be indicated?
- Iliofemoral suture application
- Craniolateral approach
- Bone tunnels prepared in femoral neck and ventral ilium just cranial to the hip
- Suture is tied with hip abducted and stifle joint is internally rotated
- Gives the joint time to heal
- Indicated for coxofemoral capsular repair
Describe the method for performing a dorsal capsulorrhapy. For which conditon is this procedure indicated?
- Indicated for capsular repair for open reduction of coxofermoral luxation
- Method
- Place two screws with flat metal washers or bone anchors in the dorsal rim of the acetabulum. Insert one anchor at the 10 o’clock position and one at the 1 o’clock position (on a left hip).
- Drill a hole through the femoral neck in the trochanteric fossa to accept suture (or place a third screw and washer or anchor in the trochanteric fossa)
- Pass orthopedic suture or heavy non-absorbable suture in a figure-eight pattern between the acetabular anchors and trochanteric fossa.
- Tie the sutures tight enough to maintain reduction but not so tight that they will tear with normal ambulation.
Describe the toggle
pin fixation method in terms of orthopaedic repair. What is this surgery used for?
- Used to correct coxofemoral luxation
- Replacement of the ligament of the femoral head (LFH; teres ligament) with a prosthetic ligament
- Steps
- LFH is anchored on the medial aspect of the acetabulum with a toggle pin which passes through acetabulum at origin of LFH and passes into femoral head at insertion of LFH
- Pin passes through a second transverse bone tunnel and exists femur on lateral aspect of femur
Describe coxofemoral transarticular pin orthopaedic surgery. What is this surgery used for?
- Used for coxofemoral luxation repair
- Replaces the ligament of the femoral head with a stainless steel (SS) pin
- Steps
- Drill a hole retrograde from the fovea capitis
- Insert intramedullary pin until tip is visible
- Reduce luxation
- Drive pin 4-5mm further though acetabular wall
- Bend pin over and cut off
- Remove pin 4-6 weeks later
Describe the use of the DeVita pin for orthopaedic surgery. What are the possible complications for its use?
- Maintains reduction following craniodorsal luxation
- Intramedullary pin inserted ventral to tuber ischium, dorsal to femoral neck and through the ventral aspect of the ilium
- Possible complications
- Risk of sciatic nerve injury as it passes close to the sciatic nerve
- Reluxation
- Pin migration
What disorder is being indicated in the following radiograph? What is the pathogenesis and treatment of this conditon?
- Avascular necrosis of the femoral head
- Pathogenesis
- Inherited basis in some breeds such as terriers and other small breeds
- Develops due to inadequate blood supply to the femoral head during development causing avascular necrosis, tranbecular collapse, inadequate cartilage support, and collapse of the femoral head with weight bearing
- Treatment
- Femoral head and neck excision
- Total hip replacement
What is an osteotomy?
An osteotomy is a surgical operation whereby a bone is cut to shorten or lengthen it or to change its alignment
For which conditions is femoral head and neck excision (ostectomy) indicated? Describe the technique.
- Salvage procedure used to treat avascular necrosis of the femoral head and hip dysplasia
- Allows rapid and predictable return to function
- Technique
- Uses cranio-lateral approach to the hip joint to maintains gluteal integrity
- Femoral head is luxated and stifle is externally rotated to 90 degrees
- The ligament of the femoral head (LFH) must be sectioned to allow adequate visualisation
- Entire femoral head and neck are removed to ensure to avoid leaving any bone spurs
What is hip dysplasia? Describe the aetiopathogenesis.
- Disparity between skeletal and muscular growth which leads to the primary lesion of hip laxity which allows hip subluxation
- Aetiopathogenesis
- Affects many breeds (primarily large breeds) and cats (predominantly maine coon cats)
- Development disease of the coxofemoral joint
- Subject to environmental influences
- Inherited predisposition
Describe the primary lesion of hip displasia.
- Primary lesion is subluxation
- Forces distribute unevenly over the acetabulum and femoral head and are concentrated over a small area causing fracture, fray, tear, synovitis, degeneration, and pain
What is being shown in the following radiograph?
Severe hip dysplasia with advanced degenerative joint disease ventrodorsal radiograph). Extensive new bone production on femoral necks creates impression of flattening of femoral head (arrow).
What is the Norberg angle? What is it used for?
* The angle made with immaginary line connecting the centers of each femoral head and nother line extending from each femoral head center to its craniodorsal acetabular rim. The angle formed by the intersection of two lines is the Norberg angle.
* Gives an ‘objective’ measure of coxofemoral subluxation with ‘normal’ considered to be >105 degrees
What are the treatment options for hip dysplasia?
- Conservative
- Clinical signs will improve in many dogs following the period of rapid growth
- Weight loss
- Exercise regulation
- Analgesia
- Surgical
- Triple pelvic osteotomy
- Femoral head and neck excision
- Total hip arthroplasty for older dogs
What are Sharpey’s fibres?
Sharpey’s fibres (bone fibres, or perforating fibres) are a matrix of connective tissue consisting of bundles of strong collagenous fibres connecting periosteum to bone. They are part of the outer fibrous layer of periosteum, entering into the outer circumferential and interstitial lamellae of bone tissue.
What is the ortolani test?
Orthopaedic test for subluxation. It provides information about the integrity of the dorsal acetabular rim (DAR).
Describe the triple pelvic osteotomy. For which patients is this procedure indicated? What are some potential complications with this procedure?
- Orthopedic procedure which isolates the acetabulum and rotates the pelvic bones to increase the femoral head cover, improve hip joint congruity and slow/halt the development of osteoarthrosis
- Indications
- Hip dysplasia
- Significant patient lamenesss
- Minimal degenerative changes
- Intact dorsal acetabular rim (DAR; can be assessed with ortolani test)
- Young animals of less than 10 months of age
- Complications
- Poor owner/patient compliance
- Implant failure
- Sciatic paralysis
- Narrowed pelvic canal
What is total hip arthroplasy (THA)? When is this sugery indicated? What are some potential complications of THA?
- Salvage procedure of the hip joint in which the hip joint is replaced
- Indicated for older patients with hip displasia that are
- Unresponsive to conservative management
- Have no presence of systemic disease
- Have no presence of neuromuscular disease
- Have no other causes of lameness
- Have no source of bacterial infection (teeth and ears have to be clear because of the artificial material inserted in body)
- Complications
- Pulmonary embolism, femoral fracture, luxation, sepsis, aseptic loosening
What are osteocytes?
Terminally differentiated osteoblasts that are encased in bone matrix during osteosynthesis
What are osteoprogenitor cells?
Cells of various stages which become osteoblasts
What is parathyroid hormone? What are its actions?
- Hormone secreted by chief cells in the parathyroid glands in response to low plasma calcium ion concentration
- Increases plasma calcium concentration by
- Mobilizing calcium from bone
- Calcium is released as osteoblasts are diplaced from the bone and replaced by osteoclasts
- Increasing calcium reabsorption and urinary phosphate excretion in the distal tubule of the nephron
- Increasing calcium absorption from the small intestine
- Mobilizing calcium from bone
What is calcitonin? Describe its action(s).
- Hormone secreted by parafollicular cells (C cells) in the thyroid gland during times of hypercalcaemic stress
- Lowers plasma calcium concentration by allowing osteoblasts access to bone surface and decreasing bone resorption
How is Vitamin D3 obtained and processed by cats and dogs? What are its actions?
- Hormone obtained from the diet or produced in the skin via effect of UV light. It is metabolized to the active form (calcitriol) in the kidney by 1-α-hydroxylase, catalyzed by parathyroid hormone.
- Active form increases plasma calcium concentration by increasing absoption from the small intestine and bone demineralization
