Ch 41 Internal fracture fixation Flashcards

Question

List the 3 main design types of interlocking nails

Answer 1

Regular interlocking nail Angle stable interlocking nail Inverse interlocking nail

Answer 2

1 - Nail are placed near the neutral axis of the bone and are therefore subjected to compressive rather than bending forces during weight bearing 2 - Large area moment of inertia provides more resistance in bending compared to bone plates of a similar size 3 - Locking mechanism provides stability in torsion and compression 4 - Intramedullary location eliminates risk of failure via screw pull-out

Answer 3

A nail which fills approx 80% of the IM cavity, using a nail with smaller holes and using bolts to lock to nail to the bone

Answer 4

Nails are available ranging from 2.5 - 10mm diameter and 62 - 230mm length Cat and small dogs 5-15kg –> 3-4mm diameter nail Dogs 15-30kg –> 6mm nail Dogs up to 40kg –> 7mm nail Dogs over 40kg –> 8-10mm nail The diameter of the nail should be as large as possible without exceeding 70-90% of the diameter of the isthmus. 75% has been recommended when using the angle-stable nail he interlocking nail should span most of the length of the bone.181 Imbedding the nail ends in metaphyseal and epiphyseal cancellous bone increases bending stability of the nail as well as fatigue life

Answer 5

current angle-stable interlocking nail > improved by machining threads to the outer surface of the central portion of the Morse-tapered peg that screws into threads of nail. provides a rigid nail/bolt interface, cortical threads in the cis and trans sections of the bolt have been eliminated. strongest constructs with this nail system will be achieved by selecting a nail that fills approximately 80% of the medullary cavity, using a nail with the smaller holes, and using bolts to lock the nail to the bone. Bolts are more resistant to bending forces compared to screws Rotational instability is likely responsible for a reported nonhealing rate of 14% in dogs treated with second-generation regular interlocking nai > Development of the angle-stable interlocking nail has been shown to overcome concerns with instability in bending and torsion (pegs used as locking devices eliminate slack.) hour-glass shape increase AMI, and allow large locking mechanism, isk for mechanical failure reduced studies demonstrated that interfragmentary motion is reduced with use of the angle-stable interlocking nail placed at a distance one to two bone diameters

Answer 6

biologic osteosynthesis. Dynamization > removing one or more locking devices as bone healing progresses (increased axial micromovement) reaming IM cavity >loss of bone and medullary blood supply > hourglass shape of the angle-stable allow increased vascularity of the diaphyseal medullary cavity because of the smaller diameter Pre-op evaluation of radiographs: fracture lines, fissures, and available bone stock. fluoroscopy (aiming device reduce this need) Sharp nail tips should be blunted Traditionally, two locking devices. locking the nail with a single proximal and distal bolt is often sufficient. care radial nerve > i.e place bolt 45 degree

Answer 7

Mean bone healing time of fractures, via minimally invasive osteosynthesis principles, was reported to be 36 ± 9 days > reflect the combined biomechanical and biological advantages In a large clinical study (121 cases), 95% of patients had good or excellent functional outcome complications poor indications (e.g., use to treat a metaphyseal fracture with insufficient bone for screw insertion) or technical errors (e.g., empty screw hole near a fracture site). no major complications were noted in 41 fractures treated with the angle-stable interlocking nail Failure to successfully place the locking device in the most distal hole in the nail can result in premature dynamization (<1% with angle-stable) bolt; fracture of the bone through a drill hole; fracture of the bone proximal or distal to the interlocking nail; rotational instability; osteomyelitis; radial nerve paralysis; sciatic nerve damage;

Answer 8

Preservation of medullary blood supply Associated with less infection and fat embolism Histologically proven to be associated with more rapid healing times

Answer 9

Static Dynamic

Answer 10

Regular: 28% misplacement Angle-stable: less than 1%

Answer 11

Overall success 83 - 96% (mostly associated with traditional designs), more recent study 95% have good-excellent outcome Mean bone healing time 36 +/- 9 days

Answer 12

Overcome concerns regarding bending and torsional instability seen with the regular locking nail Use self-tapping, Morse tapered locking screw-cone pegs Hourglass shape nail allowing placement of locking devices with larger diameter, thereby decreasing the risk of failure of the nail at the level of the nail hole, or of the locking device itself. Hourglass shape also allows increased vascularity of diaphyseal medullary cavity

Answer 13

Area moment of inertia is measured for an intrelocking nail using radius to the 4th power whereas for plates, it uses thickness to the third power The area moment of inertia of an 8mm ILN is approx 6.8x that of a 3.5mm DCP and approx 3.5x that of a 3.5mm broad DCP Area moment of inertia influences bending strength and stiffness

Answer 14

70% of the stripping torque

Answer 15

1 - Spanning long segments of bone (>3x length of the fractured segment) 2 - Limiting the screw-to-hole ratio to less than 0.5 3 - Limiting the distance between the plate and bone to <2mm 4 - Leaving at least 2-3 screw holes empty over the bone defect (This results in a weaker construct which may not always be the best for veterinary patients who will bear weight on the limb. It allows for micromotion and increased production of secondary callus)

Answer 16

The screw-plate interface

Answer 17

1 - Locking compression plate (LCP, Synthes) - oblong Combi holes allowing use of standard screws in compression or neutralisation mode or the use of locking screws in the threaded portion of the hole. The core diameter of these locking screws is larger than that of the same size standard cortical screws resulting in increased resistance to bending, and a star drive head allows for 65% greater insertional torque 2 - SOP (Orthomed) - Uses standard cortical screws that thread into the plate, allowing the screw head to press-fit into a recessed chamber 3 - Advanced Locking Plate System (ALPS, Kyon) - Uses a dual locking system - The plate hole has partial threads which lock the most proximal thread of the screw and the screw has a smooth tapered head that engages the matching plate hole 4 - Fixin System (Intrauma) - Uses a titanium insert which screws into the stainless steel plate. This insert then accommodates a screw with a morse taper head 5 - Polyaxial Locking Plate System (PAX, Securos) - The holes in the titanium plate have ridges and as the screw is inserted, the threaded head cuts its unique path into the ridges. Screws can be placed at an angle up to 10 degrees from vertical

Answer 18

Recommended plate span ratio 2-3 for comminuted fractures and 8-10 for simple fractures Recommended screw density 0.5-0.4

Answer 19

Regular bone plates secured to bone using screws such that, as the screw is tightened, the plate is compressed onto the surface of the bone. As a general rule, if 3 bicortical screws are placed, the fixation is considered secure. For the plate-bone attachment to remain rigid, the screws must remain tight. It is important that the plate be in direct contact with the bone These plates also necessitate accurate contouring absolute stability can be achieved by compressing fragments to one another. Several plate systems have screw holes that are sloped hole such that, when the screw is placed at the high end of the hole, and then tightened, the fragment that it is engaging is compressed onto the opposite fragment When a plate is loaded in bending, the pullout load resisted by the screws is greatly reduced when they are further from the fracture

Answer 20

the head of the screw locks into the plate and holds it rigidly in position, rather than pulling it to the bone. The most common method for locking is a threaded screw head engaging a threaded hole in the plate locking screws is that they are at a fixed angle to the plate and thus work together to keep plate attached to bone. 2 well-seated locked screws provide a mechanically safe attachment to a fragment. increased resistane to axial pullout (require all screws to pull out concurrently or bone to fail, and this is more than conventional screw pull out force = mechanical advantge **advantages** plate is not compressed to the bone, the periosteum does not need to be elevated. > help maintain the vascularity of bone not need to be accurately contoured. However, because the plate is slightly offset, bending and shear forces on the screws are much greater. single beam construct means bending loads distributed evenly accross all supporting screws, therefore reduce stress consentration at a single screw-bone interface locking screws generally have a larger core diameter and, thus, a larger AMI to resist these stresses **disadvantage** requirement to insert locking screws at a predetermined fixed angle to the bone plate options: screw hole in the plate can either be left empty or filled with a cortical bone screw that is directed away from the joint. Alternatively, a shorter locking screw >> might reduce the strength | bone stronger against compression than shear

Answer 21

A - Cortical screw B - Cancellous screw C - Partially threaded cancellous screw D - Shaft screw E - Cannulated screw (Kirschner wire is used to maintain reduction, and the screw is placed over the Kirschner wire, thus ensuring accurate placement.) F - Self-tapping screw (decreases the overall surface area of the bone-screw interface; therefore, the screw must be advanced so that the cutting flutes pass completely through (defined as 2 mm beyond) the far cortex )

Answer 22

The outer diameter of the screw and the strength of the material into which it is placed The core diameter determines the bending strength

Answer 23

screw threads on the head that engage either a similar thread in the plate or cut their own thread into protrusions within the plate hole (e.g., PAX system, Securos). thread pitch of the head is half that of the shaft because they have a double lead. The thread profile on the shaft > finer pitch and less depth because these screws are designed less to resist pull-out and more to have bending strength. The Fixin system (Intrauma) > threaded bushing and a conical taper of the screw head In the string of pearls system (Orthomed), standard smooth head cortical screws are used; they lock into the “pearl” using a combination of thread at the base of the pearl and a contact “ridge” within the pear

Answer 24

With a fully threaded screw, the hole in the near cortex (glide hole) is drilled so the threads of the screw do not engage. As the screw is tightened, the screw head compresses the near fragment onto the far fragment to stabilize the fracture. T he optimal orientation of a lag screw is perpendicular to the fracture plane. A position screw is used to hold fragments in a specific location. They are placed with the threads engaging both near and far fragments (cis and trans, respectively).

Answer 25

plate in bridge/axial converts axial force into bending force due to unshared laoding (eccentirc loaction therefore increases bending moment) plate on tension surface decreased bending forces on plate 1.plate span 70% diaphysis (min. 50%) 2.contour 3.place scrw 0.5cm from # 4.compress only tranasverse or short oblique 5.minimum 4-6 cortices per fragment 6.plate size (weight, screw diameter <25-30%)

Answer 26

depend og dirct plate to bone and screw to bone friction to maintain fixation therefore rely on close contact/contour, failure of reduction can occur when axial load is greater than friction force (due to excessive shear force on construct) if axial overloads friction, contruct strength relies on screw to resist shear or ability of bone surrounding screw to resist compression > construct relies on single screw pull out strength ability of plate to resist bending related to stiff/strength of plate + resistnace of bone engaged by screw thread to shear forces (axial pull out) bending converted to shear stres along screw axis (resist determined by screw outer diameter + bone quality) shear strength of bone-screw interaces = weakest locking fixed angle construct does not need to rely on screw purchase > locked screw in plate converts shear to compressive at screw-bone interface, therefore failure dt bone compression failure.

Answer 27

Scalloping means that stress is not concentrated at the screw hole Reduces the area in direct contact with the bone to preserve the blood supply During contouring, a bend can be distributed over the whole plate, rather than mostly at the screw holes The underside of the screw hole has been opened more in LC-DCP as compared to DCP. This allows screws to be angled to a greater degree

Answer 28

A - Veterinary cuttable plate 2 sizes; one for 1.5/2.0 screws, second for 2.0/2.4/2.7 screws Thinner in profile. can be stacker for increased stiffness B - Semitubular plate Due to shape fits close to bone Much weaker that DCP, not really used in vet C - Lengthening plate Solid middle portion D - Reconstruction plate v-notched between holes and made of softer steel to allow contouring in all three directions Weaker than equivalent DCP Available in 2.0, 2.7 and 3.5

Answer 29

Construct stiffness is maximised ifs screws are placed at end of plate and near the fracture 2 screws per fragment minimum, little advantage to placing more that three in regards to axial stiffness Third screw towards fracture site increases stiffness Additional of a 4th screw per fragment increases torsional rigidity If the fracture gap is small (1mm) recommended to omit screws from 1-2 holes closest to fracture If fracture gap is large (6mm), placement of innermost screws as close to the fracture as practical is recommended

Answer 30

A - SOP B - ALPS (Advances Locking Plate System) Kyon C - Fixin system D - PAX (Polyaxial Locking plate system) Securos. Titanium

Answer 31

One bicortical and one monocortical With a plate-rod construct, a lineral increase in axial stiffness can be expected when extra screws are added, up to four monocortical per fragment

Answer 32

For every increase of 10% canal filling , plate strain was reduced by approx 20% Overall construct stiffness increased by 6%, 40% and 78% respectively when rods filled 30%, 40% and 50% respectively

Answer 33

In the 3.5 mm system, a broad plate was developed for veterinary use that is made from the same bar stock as the 4.5 mm plate (see Figure 41.25D). Because the screw holes are smaller for 3.5 mm screws than for 4.5 mm screws, this plate is stronger than the basic 4.5 mm dynamic compression plate. The dynamic compression plate is made so that, given a fracture with good bone contact between the major fragments, tightening the screws drives the bone ends together. This further stabilizes the fracture and, if absolute stability is achieved, allows primary bone healing

Answer 34

dynamic compression (laod sharing) neutralisation (shiled secondary implants from physiooogical loads) briding via MIO (resists all forces) butress (resists compressionand shear force in metaphysis) elastic (increased working length proprtionaml to increase compliance therefore reduce screw pull out in softer bone)

Answer 35

nonunion osteomyelitis sequestrum causes: iatrogenic ST truama, disruption of fracture heamatoma, periosteol necrosis, trauma from implants

Answer 36

Multi-fragmentary fractures of the diaphysis and metaphysis are most suitable for MIFR. Articular fractures: case-by-case basis but are generally better open Simple diaphyseal fractures are potential candidates for MIFR, but the advantages over interfragmentary compression in these applications is debatable.

Answer 37

diaphyseal alignment is restored via indirect reduction methods the fracture site is left undisturbed somewhat flexible, rather than rigid, fixation is achieved longest possible plate that spans these landmarks is selected and precontoured based on radiographs of the intact contralateral bone. inserted into an epiperiosteal tunnel created by using a blunt instrument use of intraoperative fluoroscopy Awareness of “safe” and “unsafe” MIFR zones/corridors for MIFR implant placement is vital

Answer 38

To reduce the stress in the plate and strengthen the construct, an intramedullary pin or an orthogonal plate may be added. While direct comparison between these two studies is not possible, the increase in stiffness when an orthogonal plate is used appears to be greater A disadvantages of orthogonal plating is the potential for greater “surgeon inflicted” damage to the soft tissues, One situation where orthogonal plating may be advantageous over a plate-rod construct is for increasing purchase in small proximal or distal fragments. An intramedullary pin will only add to construct stiffness and reduce plate stress if it is firmly engaged in both ends of the bone. If it is not, small deflections in the plate will just shift the pin a little, and it will not help reduce the stress on the plate or screws. For small fragments, it may not be possible to seat the pin well, and bicortical screw purchase becomes important.

Answer 39

Reported advantages of MIO/MIPO techniques in human and veterinary: - reduced postoperative pain - preservation of the fracture hematoma - improved vascularization of the fracture site - more rapid healing - fewer wound complications, - faster return to normal function compared with open approaches.29,36 Disadvantages - technical difficulty of the learning process - longer operating times - prolonged healing - fracture malreduction - radiation safety issues associated with intraoperative fluoroscopy. Because of the conflicting evidence, Kulkarni et al 36 advocated an individual approach to each fracture based on a cost/benefit analysis.

Answer 40

two small angle-stable interlocking nails (I-Loc and Targon) with that of locking compression plates (LCP). We showed that I-Loc nails provided greater torsional stability than size-matched Targon nails and LCPs.

Answer 41

in vivo loads are extremely difficult to replicate by quasistatic mechanical testing. two main methods: ‘screw pushout’ from the plate hole apply cantilever-bending load to the screw with a force directed perpendicular to the screw long axis not generalizable across different types and manufacturers of locking bone plates. off-axis insertion degrees results in about a 50% reduction in screw push-out strength and cantilever bending of the locking screws. reduced strength of screw with cross threading is probably more than adequate to maintain construct stability in canine patients, although cyclic loading are currently unknown. Cross-threading of the screw head into the locking plate hole can impair the stability of the fixation, resulting in screw loosening and screw ‘back-out’.

Answer 42

One study published in this issue of the journal reported that the initial pushout forces of locking screws inserted axially with a torque of 1.5 Nm into 3.5-mm locking compression plates (4,356 266N) and 3.5-mm polyaxial locking plates (3,992 84 N) were reduced by about half with five degrees of off-axis insertion.2 The pushout forces for the five degree off-axis screws were increased slightly by tightening the screws to 2.5 Nm. The 3.5 PLS is more sensitive to the screw insertion angle than to the insertion torque, whereas the 3.5 LCP is affected by both factors. Placing 3.5 LCP locking screws off-axis significantly reduces the screw holding strength

Answer 43

Study Design Ex vivo biomechanical study. Materials and Methods Thirteen pairs of cadaveric humeri After removal of the fragment forceps, leaving only the cortical screw (Time point 3: T3), both the interfragmentary compression and area of compression remain significantly greater in the lag screw group. Conclusion Lag screws generate a greater force of compression and area of compression compared with position screws in this mature ovine humeral condylar fracture model. preferred option in mature bone; however, this would require clinical investigation to confirm

Answer 44

SAMPLE 48 synthetic bone block samples Anchors inserted at 45° had a higher maximum load to failure than those inserted at 90°. Constructs with 2 strands of suture had a greater pullout strength regardless of the direction of pull The strength of the anchor construct is likely increased with the use of double-loaded anchors inserted at 45°. Clinicians should consider using 2 strands in clinical cases. The exact mechanism for increased strength of the 2-stranded constructs has not been determined.

Answer 45

Conclusions: Plate A, which is wider, thicker and has a greater spacing between pearls, was mechanically superior to Plate B in four-point bending under single-cycle load-to-failure and sinusoidal cyclic loading. Clinical relevance: Although mechanical differences were identified in four-point bending, in vivo biomechanical performance remains undetermined. By selecting Plate B, the clinician may gain bone purchase through a greater number of pearls and thus screws per unit length, however, the inferior mechanical characteristics,

Answer 46

Results The three-screw constructs were stiffer than the two-screw constructs and a construct with three screws per fragment would survive longer than a construct with two screws per fragment. Due to bending, the lever arm to the middle of the gap increased with increased working length causing larger bending moments

Answer 47

Pancarpal arthrodesis was performed with ALPS on 15 limbs from 12 dogs, and HDCP on 14 limbs from11dogs Major and minor complications and surgical site infection rates were not statistically different between the two groups. Plate fracture occurred in 2/15 ALPS PCA and screw loosening occurred in 4/14 HDCP PCA. Full function was achieved in 8/12 and 8/11 The use of ALPS offers comparable performance to HDCP for PCA

Answer 48

1.0 mm wire. Methods: The peak load resisted by each cerclage type was determined (n = 6). Conclusion: Double-loop cerclage will be tighter and are better able to resist cycling than twist or single-loop cerclage. Clinical significance: Use of double-loop cerclage to stabilize bone fragments or prevent fissure propagation can be expected to provide greater resistance to loosening than twist or single-loop cerclage, both initially and with repeated loading.

Answer 49

retrospective multicenter case series reports the use of the PLS in 40 fractures in dogs and cats. All animals achieved radiographic union, and very few complications occurred. Ancillary fixation was used in 27 of 40 fractures. We found that 38 of 40 fractures achieved radiographic union without complications, which is similar to the results of other studies (81%–96.8%) in which other veterinary locking plate systems have been investigated The use of ancillary fixation in most fractures (27/40) was justified on the basis of findings of a biomechanical study in which LCP had a greater stiffness and bending strength compared with PLS plates

Answer 50

Prospective small I-Loc interlocking nail in 30 feline mean MC fill of ≤50%. no major complications faster healing times (7.2 weeks) Overreduction of the distal femoral fragment was performed.

Answer 51

Experimental. wire configuration on resistance to fragment distraction without k-wires (brass) 4 configurations The Double Loop was the strongest and most stable: ~3x greater initial tension, resisting ~2x greater load before failure at 2 mm. creating more tension in a TB construct during tying means that it will resist greater loads before it begins to loosen

Answer 52

Neurovascular structures were only damaged at the medial side of the distal humerus (10/32). We conclude that the TVS can be safely applied percutaneously to the tibia and with limitations to the femur in normal cadaveric cats without fluoroscopy. Despite the limitations of a cadaveric study, the high number of complications is leading us to consider the humerus not safe for the TVS. A learning curve has to be expected and technical recommendations should be respected to decrease complications.

Answer 53

locking compression plate (LCP) and conical coupling plate (CCP) The LCP constructs were significantly stiffer and stronger than the CCP constructs Clinical Significance LCP may be a more suitable implant for stabilizing complex diaphyseal tibial fractures in cats. Additional supplemental fixation should be considered when using CCP to stabilize unreconstructed diaphyseal tibial fractures in cats. In previous studies that found no difference, there was no offset maintained between the plate and the bone or bone mode

Answer 54

compare the locking compression plate (LCP) with polyaxial locking system (PLS) PLS plates were on average 30% weaker than LCP plates. Mode of failure (plate bending single cycle, breakage in fatigue > not screw!) micro-CT > only partial contact of the screw head with the plate hole. - LCP – mean amount of thread connection 28.85% - PLS – mean amount of thread connection 16.2% weaker bending properties of the PLS compared with LCP (risk large fracture gap)

Answer 55

Omission of the third innermost locking screw during bridging osteosynthesis subjected to bending forces led to a 20% reduction in construct stiffness and increased relative displacement (+39.6%) but did not change fatigue life.

Answer 56

90 client-owned animals. pre-contoured angle-stable ILN for femoral, tibial and humeral fractures - median %medullary canal fill 76.5% - restoration of full function in 97.1% complication rate of 11.5% including 1 catastrophic complication, 3 implant failures (mainly due to technical errors), 1 bone refracture, and 2 superficial surgical site infections. biomechanical tests are also needed to evaluate the advantages and disadvantages of the third orthogonal screw.

Answer 57

prospective SPRINT (Study to Prospectively evaluate Reamed Intramedullary Nails in patients with Tibia fractures) trial was a multi-center blinded randomized trial in humans comparing unreamed to reamed nailing of 1,319 tibial shaft fractures. Consistent with the systematic review findings, the study results supported the use of reamed nailing in closed fractures compared to unreamed nailing reamed intramedullary nailing resulted in lower re-operation rates and lower nonunion rates, with no difference in implant failure, mortality, and ARDS incidence angle-stable interlockingdesignshavebeen developed to combat rotational slack.59 Bone preparation techniques remain a topic of discussion, particularly regarding reaming. concernwith reaming the medullary canal is loss of endosteal circulation and theoretical reduction in healing potential, along with an increased systemic inflammatory load.1,50 In veterinary practice, there is also a concern that reaming may weaken the thin cortices of the long bones. bone marrow embolization, acute respiratory distress syndrome (ARDS), and leukocyte activation in lung tissue.53 Subsequent studies in both veterinary and human literature have called this into question pros increasing the nail size from7 to 8mmincreases the bending stiffness

Answer 58

(1) achievement of adequate nail diameter and stiffness to counteract bending forces, (2) proximal and distal locking with angle-stable bolts to control torsional and axial loads (3) anatomical precontouring (prebending) of interlocking nails to match the three-dimensional geometry of the marrow cavity

Answer 59

longer working length → lower stiffness in bending and torsion, higher plate strain in bending - increased plate-bone distance → decreased stiffness in torsion, no effect in bending Working length was the major determinant of construct stiffness and strain, with plate–bone distance only having a detectable effect in torsional loading construct with a longer working length would be at greater risk of implant failure than a construct with a shorter working length when the fracture configuration forces the use of a longer working length, efforts should be made to minimize the plate–bone distance to optimize construct stiffness.

Answer 60

in vitro 3.5-mm locking compression plate (LCP) at three primary plate working lengths without and with an orthogonal 2.7-mm LCP. Orthogonal plate application resulted in higher bending and torsional construct stiffness and lower strain over the primary plate in bending Working length had an inverse relationship with construct stiffness in bending and torsion and a direct relationship with strain > mitigated by the application of an orthogonal plate stiffness in four-point bending was equal between constructs and increased compared with the single-plate constructs. The increase was 40% for the short working length, 65% for the medium working length, and 80% for the long working length constructs. Plate strain was reduced after addition of the orthogonal plate Two concepts intersect in the clinical application of bridging plates—optimal fracture gap strain, influenced by construct stiffness, and plate or screw fatigue, impacted by plate stress (directly related to strain) and applied load (patient activity). we do not really know what the optimal construct stiffness should be so that there will be just the right amount of strain to accelerate callus formation and maturation In highly comminuted fractures, a plate will have a long working length. Contrary to opinions in the past, we know that strain, and, hence, stress will be higher in these plates. The yield load, where permanent deformation will occur, is also lower.

Answer 61

experimental study with tibial fracture models. 10 tibial recurvatum, Constructs in the BENT group sustained 20% and 34% greater maximum and yield loads, respectively, than STRT constructs pre-bending I-Loc AS-ILNs provided mechanical advantages by increasing their ability to resist bending resulting from eccentric compressive loads superior mechanical properties = reduced compliance and increased maximum compressive and yield loads could be explained in part by the differences in the length of the bending moment arm between groups

Answer 62

Constructs with clamps on a single side had a significantly higher yield load, yield displacement and bending strength, but the constructs with alternating clamps had a significantly higher initial torsional stiffness Torque applied to initial screw placement may play a role in reducing clamp slippage. the SOP-LC locking mechanism, using standard (AO) cortical screws that thread into the bottom portion of the clamp. 316L stainless steel rod available in different diameters that could be cut to the required length and contoured threedimensionally, coupled with special clamps that could be positioned anywhere along the rod 3.5mm system (which has a 5mm diameter rod) possessed increased bending stiffness compared with the equivalent 3.5mmDCP and limited contact dynamic compression plate (LC-DCP). In contrast, when evaluated in torsion the CRIF had decreased torsional stiffness

Answer 63

These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.