Chapter 77 - Principles of fracture treatment Flashcards
What types of fractures can be considered minor in horses?
Chip fractures of the carpus.
What are examples of severe fractures causing non-weight-bearing lameness?
Multiffragment failures of the third metacarpal/metatarsal bone (MCIII/MTIII).
What management techniques are unique to equine long bone fractures?
External coaptation and internal fixation.
What fractures may be managed with a bandage alone?
Fractures of MCII/IV or MTII/IV.
Why might radiography initially fail to detect fractures in horses?
Fractures may not be visible until 7–10 days after trauma.
What is the purpose of applying a splint bandage in fissure fractures?
To prevent fractures from evolving into complete breaks.
What is the Anderson Sling used for?
Supporting horses during fracture healing and post-fixation periods.
When is scintigraphy used in fracture diagnosis?
2–3 days after trauma to locate bony lesions.
How often should splint bandages be changed?
Every 3–4 days, more frequently in hot and humid climates.
What determines the management of a fissure fracture?
Configuration and width of the fracture gap.
What fractures should always be treated surgically?
Fissure fractures penetrating a joint.
What materials are preferred for casts?
Fiberglass.
Why are fiberglass casts advantageous?
Lightweight and breathable, improving animal comfort.
What is the first sign of complications under a cast?
Hot areas, edema, or foul odors.
Why should the first cast change occur after 3–4 days?
To address subsiding swelling and prevent looseness.
What interval is recommended for cast changes in foals?
Every 10–14 days.
What can prolonged external coaptation lead to in joints?
Cartilage degeneration and joint disease.
How does skin trauma from casts affect fracture healing?
It can lead to infection and compromise healing.
What is the risk of “compartment syndrome” under a cast?
Tissue necrosis due to swelling and pressure.
How can cast maintenance extend its usefulness?
How can cast maintenance extend its usefulness?
Hosing with water daily.
What causes foot pain after cast removal?
Expansion of the hoof after being constricted.
How can joint pain post-cast removal be alleviated?
Anti-inflammatory drugs.
What type of fractures are suitable for nonsurgical management?
Deltoid tubercle, nonarticular patellar fractures, and fissure fractures of radius/tibia.
What causes loss of proteoglycans in articular cartilage?
Immobility during prolonged casting.
What soft tissue issues result from cast use?
Weakness, inelasticity, and reduced joint motion.
Name the type of fractures amenable for stall rest
deltoid tubercle,
nonarticular patellar fractures,
fissure fractures of the radius and tibia,
fractures of the scapular spine
Fissure fractures penetrating a joint should always…
Fissure fractures penetrating a joint should always be treated surgically.
Figure 77-2. Craniocaudal (left) and lateromedial (right) radiographic views of a fissure fracture in the proximal metaphysis of the tibia of an adult horse.
Figure 77-1. An adult horse suffering from a fissure fracture of the tibia, supported by a rescue net. The net, which is applied relatively snugly to allow the horse to rest in it, is tolerated very well.
Why does equine bone healing occur more slowly compared to other species?
Equine bones have a slower remodeling process and less efficient healing than ruminants, small animals, and humans.
What are two external fixation techniques used in horses?
Transfixation pin casts and external fixators.
What is the main biomechanical principle behind the high bending stiffness of pins?
It depends on the modulus of elasticity and the area moment of inertia, which increases significantly with the pin diameter.
Why do multifragment fractures heal better than simple fractures with transfixation pin casting?
Micromotion is distributed across more fragments, reducing stress and strain in the fracture gaps.
what type of fractures is transfixation pin casting particularly effective for?
Comminuted fractures of the phalanges and distal MCIII/MTIII, and MCP joint injuries.
What is the recommended pin diameter range for transfixation pin casting in horses?
4 to 6.3 mm.
Why is pin divergence recommended during placement?
Divergence of 30 degrees strengthens fixation and lowers the risk of postoperative fracture.
Bending stiffness is defined by
Bending stiffness is defined by the product E (modulus of elasticity) × I (area moment of inertia)
Most pins and implants are made of
316L surgical steel
The area moment of inertia of cylindrical objects is defineda formula which is it?
The area moment of inertia of cylindrical objects is defined by
I = π × r4/4.
As I is calculated from the fourth power of the radius (r), small increases in the diameter have a great effect on bending stiffness
what is the recommended diameter of the pin?
Therefore it is recommended that pin tracts are in the range of 20% of bone diameter.
Each pin should diverge from the frontal plane for X to 15 degrees so that the pins diverge from each other by Y degrees, which results in a stronger fixation and lower risk for postoperative fracture
Each pin should diverge from the frontal plane for 10 to 15 degrees so that the pins diverge from each other by 30 degrees, which results in a stronger fixation and lower risk for postoperative fracture
The transifxation pins should be separated by
2 to 4 cm
what is the best way to reduce heat control?
An effective method of heat control is to initially drill a smaller hole, followed by stepwise enlargement through larger drill bits.
what is the temperature within the bone associated with bone necrosis in drilling?
55ºC = loosening
A pin with a diameter that is** X mm larger** than the prepared hole (radial preload of 0.1 mm) provides the best pin holding strength with the least weakening of the bone surrounding the implant.
A pin with a diameter that is 0.1 mm larger than the prepared hole (radial preload of 0.1 mm) provides the best pin holding strength with the least weakening of the bone surrounding the implant.
What is the benefit of step drill bits compared to sequential drilling?
They allow quicker preparation of holes without exceeding the thermal damage threshold for bone.
What temperature threshold must not be exceeded to avoid thermal bone damage?
47°C for more than 1 minute.
What type of pins are recommended for transfixation pin casting, and why?
Positive-profile pins because they resist pullout forces and minimize loosening.
What can happen if pinholes exceed 10% of the bone’s diameter?
Significant reduction in torsional strength and increased risk of fractures.
What is the purpose of using cold sterile saline during drilling?
To reduce heat and prevent thermal damage to the bone.
What materials are typically used for the fiberglass cast layer?
Fiberglass cast tape, applied over stockinet and padding.
Why should threaded pins engage both cortices?
To ensure stability and prevent loosening.
What additional step is taken to secure pin ends within the cast?
They are incorporated into the cast using dowels or acrylic layers.
What is the recommended action when a pin becomes loos
Immediate removal and possible replacement at a different location.
What is the most common complication of transfixation pin casting?
Pin tract infection leading to loosening.
What leads to ring sequestrum formation around pins?
Weight bearing and osteolysis around the pin.
Why should diaphyseal pins be avoided?
They have a higher risk of complications like sequestrum formation and pathologic fractures.
What complication can occur due to insufficient distance between skin and fixation devices?
Skin necrosis due to swelling.
Advantages of transfixation pin casting
minimal load on the fracture site
and minimal distraction
and movement between the fragments
what is the ideal cast padding layer in mm?
5 to 7mm layer of fiberglass cast
disadvantages of external coaptation
development of cast disease, osteoporosis,
contracted hooves,
tendon laxity, apply to this type of treatment
how much time can the transfixation be maintained before simple casting?
6 to 8 weeks
Pin tract infection with ring sequestrum formation can occur and is preceded by a sudden onset of lameness occurs typically in which type of horses?
heavy horse (>500kgs) after 2 weeks place a new pin after removal in a new place
Name types of external fixation
The Steinmann pins and Schanz screws pins with a threaded end)
Why has the use of external skeletal fixators in horses been largely abandoned?
Due to complex application and high complication rates.
What is the limitation of CESFs in equine fracture management?
They are primarily effective in cattle and rarely in foals.
What is a major determinant of axial stability in transfixation pin casting?
The fiberglass cast material.
What indicates pin tract infection?
Sudden onset of lameness.
How is drainage from a pin tract managed?
Curetting and flushing the tract.
What precautions are taken during a cast change involving pin removal?
Temporary filling of the tract with antiseptic-soaked sponges.
Why is early recognition of pin loosening critical?
To prevent severe complications such as pathologic fractures and sepsis.
What risk does osteoporosis pose during fixation?
It weakens the bone, increasing the likelihood of pathologic fractures.
What is “cast disease”?
Complications like osteoporosis, contracted hooves, and tendon laxity caused by prolonged casting.
What design feature of pins can prevent stress concentration?
A tapered thread-run-out (TRO) feature.
If several pins are loose what should you do?
Depending on the degree of fracture healing, it is important that pins be removed one at a time
What is ORIF in internal fixation?
Open Reduction and Internal Fixation, involving wide skin opening and tissue separation to stabilize fractures.
Why is minimally invasive plating preferred in some cases?
It preserves the hematoma and growth factors around the fracture, improving healing outcomes.
Why are multifragment radius fractures with caudal defects not suitable for surgery?
They have poor healing potential due to stress cycling leading to implant failure.
What is the purpose of a drill guide in fracture treatment?
Stabilizes the drill bit, reduces tissue trauma, and prevents bit slippage.
Why are sharp drill bits important in equine fracture treatment?
To minimize heat generation and improve precision during drilling.
How does the plate-bending press help in equine fracture treatment?
Allows precise contouring of plates to match bone curvature without damage.
What is the primary function of cortex screws?
Provide strong fixation in dense cortical bone.
Why are cancellous screws rarely used in equine fixation?
They are designed for soft bone and are less effective in equine cortical bone.
What is unique about cannulated screws?
They have a central canal for guide wires, improving accuracy.
What are Acutrack screws, and when are they used?
Tapered, self-compressing screws used for specific equine fracture repairs.
Figure 77-8. Proper technique of plate contouring with the bending press. (A) Plate contouring should be performed with the lever in approximately the horizontal position. This allows the best control over the amount of bending achieved. (B) The resting plate for the plate to be bent (a) and the anvil (b) have complementary contours, allowing plate bending without damaging the plate. The resting plate can be moved up and down (arrow) with the turning nut (c) at the bottom of the bending press. (C) For a convex bend, the plate is positioned toward the center of the bending press matching the contours of the resting plate and anvil. (D) For a concave bend, the plate is positioned toward the front of the bending press, again matching the contours of the resting plate and anvil. (E) Trying to achieve a gentle bend in the plate with the lever in this position is not possible; an acute excessive bend will be the result. The turning nut should be turned to lower the resting plate until the lever is in a horizontal position.
Figure 77-10. Schematic drawing of a 7.3-mm cannulated screw with the guide pin inserted and half of the shaft removed. Insert: the reverse-cutting design of threads, which facilitates screw removal after healing of the fracture.
Figure 77-13. Lag technique, shown on a lateral condylar fracture of the distal MTIII. (A) The cis-cortex is overdrilled. (B) The insert drill bit is placed into the glide hole and advanced past the fracture plane, and the concentric thread hole is drilled across the trans-cortex. (C) A depression for the screw head is prepared with the countersink. (D) The required length of the screw is determined with the depth gauge. (E) The threads are cut into the thread hole with the tap. (F) The screw of predetermined length is inserted and solidly tightened with the hexagonal-tipped screwdriver.
what is the name of the device devoleped to remove in case of the head of the screw is stripped?
A special screw-retrieval instrument, the so-called conical extraction screw, has been designed for such situations (Figure 77-15).
Figure 77-24. Preoperative (A) and postoperative (B & C) radiographs of a metaphyseal fracture of MTIII in an adult Icelandic pony. The fracture was repaired with a laterally applied DCS plate and a shorter dorsal DCP.
Figure 77-27. Repair of a simple oblique fracture of MCIII with two cortex screws applied in lag technique combined with a broad 12-hole LCP as a neutralization plate. (A) The large pointed reduction forceps maintains alignment of the fractured bone during implantation of the two 3.5-mm cortex screws. (B) The two screws are implanted and the reduction forceps is removed. (C) A 12-hole broad LCP is applied to the dorsolateral aspect of the bone. Note: in this plate only cortex screw are used. The plate was overbent at the fracture site, allowing introduction of an aluminum template between the bone and the plate. (D) A thread hole is drilled across the bone through the second most distal plate hole with the help of the universal drill guide in load position (no vertical pressure is applied to the drill bit and it is positioned at distal end of the DCU portion of the combi-hole).
Continued
(E) The screw is inserted but not completely tightened, followed by preparation of a drill hole in neutral position (pressure is applied to the drill guide, which positions it in the neutral position of the DCU portion of the combi-hole). Note the central part of the drill guide is protruding over the drill guide at the opposite end of the plate. The second screw is inserted and both are alternately tightened, placing the fracture under axial compression. (F) An additional drill hole is prepared in neutral position in the distal fragment, followed by screw insertion and tightening. (G) A cortex screw is implanted in lag fashion across the fracture plane. (H) The remaining screw holes are prepared in neutral position, all the screws are inserted and tightened.
Figure 77-32. Application of two LCPs to an oblique midshaft MCIII fracture. (A) The fracture is reduced and stabilized by the two 3.5-mm cortex screws applied in lag fashion. A 10-hole broad veterinary LCP is applied to the bone with the plate holder and temporarily fixed in place with the push-pull device. By turning the piston clockwise (arrow), the plate is pressed onto the bone surface. (B) To facilitate good plate-bone contact along the entire plate, cortex screws are implanted and tightened using the plate screw technique at both ends and in the center near the fracture. Once in place, the lateral 11-hole narrow veterinary LCP is applied to the bone using the same technique. Note that the plate can be applied farther distad on the lateral aspect of the bone than on the dorsal aspect. (C) Next the holes where locking screws are to be inserted are selected and the drill guides twisted into the threaded portion of the combi-hole. Because the plate is solidly fixed to the bone, all four drill guides provided in the set are applied, followed by drilling all four holes. (D) The locking head screws are inserted and tightened. The four drill sleeves for the locking head screws are then placed into selected plate holes of the lateral plate, making sure that screws can be placed perpendicularly without interfering with previously inserted implants. (E) All the remaining plate holes are filled with cortex screws inserted using the plate screw technique. Where indicated, lag technique is applied to increase interfragmentary compression.
Figure 77-34. Preoperative (A) and postoperative (B) radiographs of an oblique, spiral radial fracture. The fracture was repaired with a 17-hole 5.5/5.0-mm veterinary LCP cranially and an 18-hole 4.5/5.0-mm human femoral LCP (a slightly axially bent plate) laterally.
Figure 77-43. This long oblique humeral fracture (A) was treated with an intramedullary interlocking nail. To provide a greater screw-bone contact area, washers were used. The craniocaudal (B) and lateromedial (C) 2-month follow-up radiographs show progressive bone healing in the fracture gap. Bone length is maintained.
