Fracture implants Flashcards

Question

What does pin loosening and migration proximally indicate?

Answer 1

Instability and movement at the fracture site

Answer 2

Pin penetrated the cartilage at the time of insertion - retraction and redirection is ofter is often not successful at correcting this.

Answer 3

The pin should be long enough to sit in the cancellous bone in the metaphysis and, if removal is planned, the other end needs to be long enough for retrieval once the fracture has healed.

Answer 4

active distracting forces are counteracted and converted into compressive forces.

Answer 5

The tensile forces exerted by contraction of muscles on fractures such as those involving the olecranon, greater trochanter, medial malleolus, acromion of the scapula, os calcaneus or tibial tuberosity can be overcome & converted into compressive forces by inserting two Kirschner wires and a tension band wire

Answer 6

Reduce the fracture Place two parallel K wires perpendicular to the fracture K wires should just penetrate the far bone cortex A transverse hole is drilled through the diaphysis distal to the fracture site Cerclage wire is inserted in a figure-8 pattern going around the protruding K wires and tightened K wires bent over and ends cut

Answer 7

This procedure refers to a circle of wire that completely (cerclage) or partially (hemicerclage) goes around the circumference of the bone. This is NOT used as the sole method of fixation on any type of long bone fracture.

Answer 8

Cats and small dogs: 22 gauge Medium dogs: 20 gauge Large dogs: 18 gauge

Answer 9

Long oblique fracture Use at least two wires to prevent pivoting Must use additional primary fixation Must NOT be used in comminuted fractures Apply tightly Restrict the use of the wires to areas where the bone can be reconstructed - not unreduced fractures Should be placed 0.5cm from the fracture line and a gap of 1 to 1.5cm WIres should be placed at narrowest part of bone or with a K wire to prevent slippage Use pliers to twist wires- cut leaving 3 twists

Answer 10

Very infrequesntly used Holes drilled through the bone on either side of the fracture and wire passed through

Answer 11

Narrower thread Coarser pitch Used primarily in diaphyseal or cortical bone

Answer 12

Can be partially or fully thread Wider thread due to less dense bone Finer pitch (less threads) weaker than cortical screws Used to compress fragments of epiphyseal or metaphyseal bone

Answer 13

usually in the metaphyseal or epiphyseal area (cancellous bone which heals quickly). If fractures are articular the fracture fragments should be compressed to ensure a stable repair and primary bone healing. To accomplish interfragmentary compression screw threads should not engage in the near cortex (cis) only the far one (trans). Inserting a screw in this fashion makes it a lag screw.

Answer 14

The near fragment must be ‘overdrilled’ with a hole equal in size to the diameter of the screw threads – the glide hole so threads do not engage the near cortex. A hole equal in diameter to the screw core is drilled in the far cortex – the thread hole. An insert guide is placed in the glide hole prior to drilling the thread hole to ensure that the hole is drilled at the correct angle.

Answer 15

Oblique diaphyseal fractures or fractures with large bone fragments can be reduced and stabilised with lag screws. (Lag screws are preferable to cerclage wires as they can be placed to give more compression) Similarly to cerclage wires, screws are never used in isolation for repair of diaphyseal fractures but they are usually combined with plates.

Answer 16

Commonly used are 1.5mm, 2mm, 2.4mm (more recently introduced), 2.7mm and 3.5mm. To drill the hole, a drill bit one size smaller is used (eg a 2.7mm drill bit for a 3.5mm screw). For conventional screws, the hole needs to be tapped with a tap of the same size as the screw (3.5mm tap for a 3.5mm screw).

Answer 17

Have a little tap attached to their tip

Answer 18

Have a flatter pitch compared to cortical screws and a threaded head, which locks into the plate. They are also self tapping

Answer 19

Specialised equipment is available for placing interlocking nails in dogs and cats. Nails are available in 4.0,4.7, 6.0 and 8.0mm sizes. They have 3 to 4 preplaced holes / nail and a temporary jig that attaches to the nail so once inside the bone a screw can be placed from the outside of the leg through the bone into the nail. The advantage is that rotation, compression and nail migration are prevented and the nail is placed inside the bone – biomechanically a good position for resistance to bending. Suitable fractures are mid diaphyseal, comminuted fractures in straight bones.

Answer 20

Many different types of bone plates Can be inserted in different modes. Plates may be inserted to function as a compression plate, neutralisation plate or bridging plate.

Answer 21

Compression of a fracture surface improves friction at the fracture site, minimises gap formation, encourages load sharing between implant and bone and is optimal for primary or direct bone union. There are two types of compression. When a plate is applied as a compression plate it implies that the static compression of fracture fragments is present.

Answer 22

usually achieved by the application of a self compressing plate (DCP) (but can also be achieved by the use of a regular (round hole) plate and a compressing device).

Answer 23

Transverse fractures, osteotomies, or arthrodeses

Answer 24

Results from the muscular tension across the bone during weight bearing. The plate should be applied so it is under tension and the fracture fragments under compression (tension band principle). The plate must be applied to the tension side of the bone. The tension side of the bone is related to its anatomy and musculature.

Answer 25

Cranial or medial

Answer 26

Cranial or lateral

Answer 27

Craniomedial or cranial

Answer 28

This plate is also applied to the tension side of the bone to neutralise or overcome the forces (torsional, bending, compressive or distraction) to which the fractured bone may be subjected during healing. Interfragmentary compression is supplied by lag screws or cerclage wires that are used to reconstruct the cylinder of bone. The plate is applied across the reconstructed bone. Fractures suitable for neutralisation plates include unstable fractures or osteotomies that can be anatomically reconstructed using lag screws or cerclage wires. Most useful for simple oblique/spiral fractures.

Answer 29

The plate is used to shore up fragments of bone thereby maintaining bone length. A relatively larger plate should be selected when the plate is being used as a bridging plate. There is some overlap in terminology with ‘biological plating’ where fragments are left unreconstructed to minimise disruption of blood supply.

Answer 30

Unreconsrtuctable plate

Answer 31

Tension band principle Minimum of two (or three) screws applied either side of a fracture Minimum distance a screw is placed from fracture line is 5mm Longer plate is better Contouring the plate for conventional plates to maintain anatomical reduction Prestressing the plate advisable for transverse fractures Selection of proper plate size and screws is important Try not to leave an empty screw hole over the fracture

Answer 32

Plates are loose, broken or bent Plate acts as a thermal conductor - lameness in cold weather especially associated with tibial or radial fractures Plate causes stress protection or interferes with the vascular supply to the bone resulting in osteoporosis. Plate crosses a growth plate Plate causes irritation – lick granuloma occasionally seen with superficial plates Infection – if the fracture is stable then the plate should be left in place until healing has occurred prior to plate removal Some surgeons will remove the plate routinely once the bone has healed – this generally should not be done sooner than 5 months after fracture repair in an adult animal

Answer 33

Dynamic compression plate (DCP) - conventional plate Locking compression plate (LCP) Acetabular plate Cuttable plates Lengthening plate T plates Reconstruction plates

Answer 34

The design of the screw holes in this plate is based on the spherical gliding principle. As the screw is tightened the spherical screw head glides towards the centre of the plate until the deepest portion of the plate is reached. The result is the bone fragment attached to the screw is displaced at the same time towards the fracture which results in compression of the fracture line. When the load guide is used the fracture is compressed approximately 1mm for a 3.5mm plate. A maximum of four screws (two each side of the fracture) can be inserted in the load position which results in a maximum of 4mm compression.

Answer 35

This plate can be used with standard screws to create interfragmental or axial compression or with locking screws to create a stable plate-screw connection without loss of reduction, regardless of plate modelling.

Answer 36

Plate available in long lengths which are CUT to the desired length. Particularly useful for cat long bone fractures or MT/MC fractures in large dogs. Plates can be stacked (use two together – one on top of each other) to increase strength. Sizes available to take 1.5mm / 2.0mm & 2.7mm screws.P

Answer 37

Plate has a central portion without holes so useful in unreconstructable diaphyseal fractures as a buttress plate

Answer 38

Useful in fractures with a small distal or proximal fragment as they allow placement of 2 to 3 screws in the fragment.

Answer 39

Plates can be contoured in 3 planes – bent, twisted and curved to allow accurate contouring and reconstruction of awkward shaped bones like the pelvis or mandible.

Answer 40

Salvage procedure Plate over a joint

Answer 41

Parts of the joint are removed e.g. head of the femur

Answer 42

Parts of the joint are replaced - can be surface or the whole end of a bone