IM=NTRAMEDULLARY NAILING

INTRAMEDULLARY NAILINGDR ASHWANI PANCHALJSS MEDICAL COLLEGEMYSOREINTRAMEDULLARY NAILING The intramedullary nail is commonly used for long-bone fracture fixation and has become the standard treatment of most long-bone diaphyseal and selected metaphyseal fractures1

To understand the intramedullary nail, knowledge of evolution and biomechanics are helpful 2HISTORYIn 16 th Century In Mexico Aztec physicians have placed wooden sticks into the medullary canals of patients with long bone non-union.

In Mid 1800s Ivory pegs were inserted into the medullary canal for non-union. In1917 s Hoglund of United States reported the use of autogenous bone as a intramedulary implant. 1930s In the United States, Rush and Rush described the use of Steinman pins placed in the medullary canal to treat fractures of the proximal ulna and proximal femur. 1940 s : The Evolution of Kntscher Nailing

Gerhard Kntscher was born in Germany in 19001931 : Smith-Petersen reported the success of stainless steel nails for the treatment of NOF #s

1940s:GerardKntscher developed V nail, Cloverleaf shaped and the Y nail.

His methods were based on two principles: stable fixation and closed nailing. ..Harvey C. Hansen and Dana M. Street developed a diamond shaped nail which is relied on the holding power of cancellous bone at both ends. He termed the word BoltLottes designed three flanged femur and tibial nails. Both nails employed a screw-on driver-extractor

1950s:Stryker designed a broach in a cloverleaf and diamond shaped pattern. It provided maximum holding power to resist torque and avoided reaming the entire canal circumference.

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Schneider designed his nail which incorporated a double-ended stud, self broaching and fluted with a square cross section1950s Interlocking Screws :Modny and Bambara introduced the transfixion intramedullary nail in 1953

Nailing of tibia is introduced by herzog in 1950.

Livingston bar,introduced a short I-beam pattern pointed nail at both ends,which had short slots for cross-pinning with screws

INTRODUCTION Today any fracture is stabilized by one of the two systems of fracture fixation . 1. compression system 2. splinting system Intramedullary fixation belongs to internal splinting system. Splintage may be defined as a construct in which micromotion can occur between bone & implant, providing only relative stability without interfragmentary compression. Depending on the anatomy the insertion can be ante grade and retrograde.

The entry point depends on the anatomy of the bone but is distant from the fracture site.

Intramedullary fixation techniques offer the advantages of closed reduction and closed fixation.

10INTRAMEDULLARY DEVICES ARE BROADLY CLASSIFIED INTO: A.CENTROMEDULLARY- K NAIL,FIRST GENERATION IM NAIL

B.CEPHALOMEDULLARY- GAMMA NAIL, RUSSELL TAYLOR NAIL,UNIFLEX, PFN

C.CONDYLOCEPHALIC NAIL-ENDER NAIL,LOTTES ETCcondylocephalic fixationAlso known as elastic stable intramedullary nailing (ESIN), is a primary definitvie fracture care (PDFC) in paediatric orthopaedic practice.

This method works by 3 point fixation or bundle nailing.

The elasticity of the construct allows for ideal cirumstances of micro-motion for rapid fracture healing.Nonreamed nails are actually not nails but pins. Their mechanical characteristics and use are different from IM nails. They are of smaller diameter and are more elastic.Their flexibility allows insertion through a cortical window. There are many different types of flexible nails, the best known are:- Lottes nails - Tibia Rush pins for all the long bones of the body Ender nailsMorote nails Nancy nails Prevot nails Bundle nails13

Intramedullary nails to be used as single without reaming.Schneider nail [ solid, four flutedcross section and self broaching ends.Harris condylocephalic nail [curved in two planes, and designed for percutaneous, retrograde fixation of extra capsular hip fractures.Lottes tibial nail specially curved to fit the tibia, and has triflanged cross section. 14

RUSH NAILS

SOLID, CIRCULAR IN CROSS SECTION, STRAIGHT,WITH A SHARP BEVELLED TIPS AND A HOOK AT THE DRIVING END. 15

Ender Nails, which are solid pins with an oblique tip and an eye in flange at the other end, were originally designed for percutaneous, closed treatment of extra capsular hip fractures16BIOMECHANICSEach nail is precurved to achieve 3-point fixation where the required precurve should be approximately 3 times the diameter of a long bone at its narrowest point.Part of the biomechanical stability is provided by the intact muscle envelope surrounding the long bone.

All currently available nails have beaked or hooked ends to allow satisfactory sliding down on insertion along inner surface of the diaphysis without impacting the opposite cortex.

Insertion points that do not lie opposite to one another produce differing internal tension and imbalance of the fracture stability and fixation.

The apex of the curvature should be at the level of the fracture site.

The nail diameter should be 40% of the narrowest medullary space diameter.

.Two nails of the same diameter and similarly prebent to be used.Commonest biomechanical error is lack of internal support.

There are two basic methods of IM pinning, they are: 1. Three point compression.2. Bundle nailing.

Most pins stabilize fracture by three point compression.

These pins are C- or S Shaped, they act like a spring. The equilibrium between the tensioned pin and the bone with its attached soft tissues will hold the alignment.20The principle of bundle nailing was introduced by Hackethal. He inserted many pins into the bone until they jammed within the medullary cavity to provide compression between the nails and the bone.

Both techniques should be seen more as IM splinting than rigid fixation.

Bending movements are neutralized, but telescoping and rotational torsion are not prevented with this techniqueBUNDLE PINNING

Flexible nail are usually simpler to use and can be inserted more quickly.

If infection intervenes, the complication of likely less severe. So can be used in tibia open fracture because of its less blood supply and its subcutaneous location.

Because of small size of forearm bones reaming is technically difficult, so unreamed nail have generally been used.23INTRAMEDULLARY INTERLOCKING NAILS:They are usually reamed nails in which interlocking is its newer modification.

The classic reamed nail is the hollow, open section nail of Kntscher.

Most other reamed nails are variations of the Kntscher nail such as the AO nail, and the various interlocking nails, such as the Grosse kempf, Klemm Alta, Russell Taylor, Uniflex, AO Universal and others.VARIOUS GENERATIONS OF NAILSConsecutive advancements of nails over years Can be grouped under three generations

1 st generation: primarily act as splints ,rotational stability is minimal , primarly relies on close fit Eg K nail , V nail 2 nd generation :Improved rotational stability due to locking screw Eg-Russel taylor nail3 rd generation: Nails with various designs to fit anatomocally as much as possible ,to aid the insertion and stability Eg -Nails with multiple curves ,multiple fixation systems Tibial nail with malleolar fixationThe integrated screw configuration is a fourth generation intramedullary nail concept combining the enhanced rotational stability of the TRIGEN Reconstruction Nail with the superior controlled sliding and compression of the IMHS implant. fourth generation intramedullary nails combining the rotational stability of the original RUSSELL-TAYLOR Reconstruction Nail with the enhanced sliding and compression of the IMHS Intramedullary Hip Screw. 25

Kuntscher nail, designed for open nailing.

Kuntscher nail designed for closed nailing which has a curved, tapered tip, and is slotted throughout.C.Grosse Kempf nail D.Alta intramedullary locking nail for the femur. This is solid section, cannulated nail with a hexagonal cross section with smooth flutes to enhance revascularization. .THE Grosse Kempf and Klemm nails were the first generation of locking nails. Many new second generation designs are available that address a wide range of problems in the femur, tibia and humerus. A locking nail for the forearm has not yet gained wide use. Nearly every fracture combination in the femur can be addressed by percutaneous fixation techniques26

Russell Taylor nail:

This is a second generation nail.

Proximal locking into the femoral head enhances its stability in hip fractures

Brooker Wills nail fixing a fracture of the femur, an AP roentgenogram. This nail has flanges deployed through slots in the tip of the nail for distal stability. 28LOCKING NAILS :Except for the Brooker Wills nail with its flanges and the expandable tip of the Seidel nail, which is used exclusively for the humerus, all current designs use two distal transverse cross locking screws, as in the Alta intramedullary rod

Proximal fixation includes inclined screws as in the Grosse Kempf nail, two transverse screws, as in the Alta, and specialized screws though the nail designed to secure fixation in the femoral head, as in the Russell Taylor

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Gamma nail: This intramedullary device is designed for proximal intramedullary fixation of intertrochanteric and some subtrochanterc fractues.

BIOMECHANICSWhen placed in a fractured long bone, IM nails act as internal splints with load-sharing characteristics.

Various types of load act on an IM nail: torsion, compression, tension and bending

Physiologic loading is a combination of all these forces

Elastic deformation is the principle of nail stability. As a nail is hammered into the IM canal, it induces strain, which results in a radially orientated force. This force is proportional to the contact area between the bone and the nail and produces friction that stops the nail from pulling out 31

Bending moment = F x DF = ForceD

F = ForceDThe bending moment for the plate is greater due to the force being applied over a larger distance.IM NailPlateD = distance from force to implant.

Nail cross section is round resisting loads equally in all directions.

Plate cross-section is rectangular resisting greater loads in one plane versus the other. BIOMECHANICSThe amount of load borne by the nail depends on the stability of the fracture/implant construct.

This stability is determined by

1.Nail Characteristics 2.Number and orientation of locking screws 3.Distance of the locking screw from the fracture site 4.Reaming or non reaming 5.Quality of the bone

IM nails are assumed to bear most of the load initially, then gradually transfer it to the bone as the fracture heals.Secondary displacement due to bending of the nail is rare if a standard reamed Kuntscher nail is used, as the large diameter implant is the main stabilizer. The weak point is the resistance to axial forces and torsion, as the stability depends on the friction between the bone and the nail. This is a minor problem in simple oblique or transverse fractures, as the contact of the two main fragments provides adequate stability. With comminuted fractures., this is not the case, and the standard Kuntscher nail does not prevent shortening in comminuted fractures34BIOMECHANICSSeveral factors contribute to the overall biomechanical profile and resulting structural stiffness of an IM nail. Chief among them are

a)Material properties b)Cross-sectional shape c)Diameter Curvesd)Length and working length e)Extreme ends of the nail f) Supplementary fixation devices 35 Material properties Metallurgy less important than other parameters for stiffness of an IM Nail.

Most of them are fabricated from stainless steel, with a small number from titanium.

Titanium alloy has a modulus of elasticity closely approximates that of cortical bone ( Modulus is ability to resist deformation in tension The material must be stiff . Titanium are 1.6 times stiffer and elastic modulus is 50% lower than steel nail The cross-sectional shape of the nail ,Diameter determines its bending and torsional strengths( Resistance of a structure to torsion or twisting force is called polar movement of inertia )

Circular nail has polar movement of inertia proportional to its diameter, in square nail its proportional to the edge length

Nails with Sharp corners or fluted edges has more polar movement inertia

Cloverleaf design resist bending most effectively .Presence of slot reduces the torsional strength . It is more rigid when slot is placed in tensile sideCROSS SECTIONAL SHAPESA-Schneider B-Diamond C-Sampson fluted D- Kuntscher E-Rush F-Ender G- Mondy H-Halloran I- Huckstep J-AO/ASIF K-Grosse Kempf L-Russell-Taylor

Diameter :

Nail diameter affects bending rigidity of nail.

For a solid circular nail, the bending rigidity is proportional to the third power of nail diameter

Torsional rigidity is proportional to the fourth power of diameter .

Large diameter with same cross-section are both stiffer and stronger than smaller ones.

Some nails are designed in a such a way that stiffness doesnt vary with diameter. The diameter of a nail should always be measured with a circular guage.

In reamed nailing, the width of nail is better determined by the feel of the reamers than by radiographic measurements, although the approximate size to be used can be determined from preoperative radiographs.

Nail Diameter (mm)Stainless Steel (X 106 )Titanium (X 106 )1040.020.01152.026.01269.034.51388.844.414112.156.415139.169.616170.175.117241.4120.7Flexural rigidity (EI) of slotted cloverleaf IM Nails (1mm wall thickness) (Nmm2)Obtain preoperative radiographs of the fractured long bone, including the proximal and distal joints.

If there is any question, obtain an anteroposterior radiograph of the opposite normal limb at a tube distance of 1meter. A nail of the appropriate size should be taped to the side of the limb for reference, or a radiographic ruler can be used, alternatively a Kuntscher measuring device the ossimeter may be used to measure length and width. The ossimeter has two scales, one of which takes into account the magnification caused by the X-ray at a 1 m tube distance.-In most cases, a nail reaching to within 1 to 2 cm of the subchondral bone distally is indicated.Size length

CURVES Longitudinal (Anterior) bow

Governs how easily a nail can be inserted as well as bone/ nail mismatch, in turn influences the stability of fixation of the nail in the bone.

Complete congruency minimizes normal forces and hence little frictional component to nails fixation.

Conversely, gross mismatch increases frictional component of fixation and inadequate fracture reduction.Femoral nail designs have considerably less curve, with radius ranging from 186 to 300 cm

Herzog bend Tibial nail also has a smooth 11 bend in the anterioposterior direction at junction of upper one third and lower two third .

Mismatch in the radius of curvature between the nail and the femur can lead to distal anterior cortical perforation

When inserting nail , axial force is necessary as the nail must bend to fit the curvature of the medularly canal .

The insertion force generates hoop stress in the bone ( Circumferential expansion stress )

Greater the insertion force higher the hoop stress. Larger hoop stress can split the bone

Over reaming the entry hole by 0.5-1mm ,selecting entry point posterior to the central axis reduce the hoop stressExample :The ideal starting point for insertion of an antegrade femoral nail is in the posterior portion of the piriformis fossa . It reduces the hoop stress

Length and working length

A-Total nail length- total anatomical length B-Working length- -Length of a nail spanning the fracture site from its distal point of fixation in the proximal fragment to proximal point of fixation in the distal fragment

-Length between proximal and distal point of firm fixation to the bone

-Un supported portion of the nail between two major fragments

Working length is affected by various factors

Type of force (Bending ,Torsion )

Type of fracture

Interlocking

ReamingWorking length:The bending stiffness of anail is inversely proportinal to the square of its working LengthThe torsional stiffness is inversely proportional to its working length.Shorter the working length stronger the fixation

Medullary reaming prepares a uniform canal and improves nail- bone fixation Towards the fracture,thus reducing the working length.

Interlockingscews alsso modify the working length in torsion by fixing the nail to the bone specific points.the torsional stability is substantially improved by this technique and is directly related to distance between two points.

49INTERLOCKINGInterlocking screws are recommended for most cases of IM nailing.

The number of interlocks used is based on fracture location, amount of fracture comminution , and the fit of the nail within the canal.

Placing screws in multiple planes may lead to a reduction of minor movementThe principle of interlocking nailing is different. The nail is locked to the bone by inserting screws through the bone and the screw holes. The resistance to axial and torsional forces is mainly dependent on the screw bone interface, and the length of the bone is maintained even if there is a bone defect.

50STATIC LOCKING when screws placed proximal and distal to the fracture site. This restrict translation and rotation at the fracture site. Indications communited , spiral,pathologicalfractures Fractures with bone loss lengthning or shortening osteotomies , Atropic non union

It achieves BRIDGING FIXATION through which fracture is often held in distraction , a favourable environment for periosteal callus formation exists and healing rather than nonunion is rule.To improve the screw hold, different techniques have been invented. Vecsei suggested a dowel bolt for fixation in osteoporotic bone. A similar technique is the so called modular screw, where the locking screw is inserted into bilaterally placed screws with a high thread depth. The aim of this technique is to increase the surface area with the bone. Some nails have a twisted blade instead of the proximal interlocking screw. In the distal femur, interlocking with a bladelike device has been shown to be 41% stiffer and 20% stronger than with conventional locking bolts. The number and orientation of the interlocking screws influence the stability of the nail bone construct.

51DYNAMIC LOCKING

It achieves additional rotational control of a fragment with large medullary canal or short epi-metaphyseal fragment.

It is effective only when the contact area between the major fragments is atleast 50% of the cortical circumference.

With axial loading, working length in bending and torsion is reduced as nail bends and abuts against the cortex near the fracture, improving the nail-bone contactDYNAMISATION:No longer std. practice to dynamize an interlocked nail by removing the locked screws .

It is indicated when there is a risk of development of nonunion or established pseudoarthrosis.

The screws are then removed from the longer fragments, maintaining adequate control of shorter fragment. Premature removal may cause shortening, instability and nonunion.when malalignment develops during nailinsertion,placement of blocking screw, and nail reinsertion improves alignment.

Most reliable in proximal and distal shaft fractures of tibia.

A posteriorly placed screw prevents anterior angulation and laterally placed screw prevents valgus angulation.

Poller screw Screw strengthCharacterised by an outer diameter, root diameter and pitch.

Shape of the threads at their base determines stress concentration (sharp v/s rounded).

Pullout strength is dependent on the outer diameter.

The largest diameter of the screw which can be used is limited by the diameter of the nail.

Increasing the diameter of the screws reduces the cross section of the nail at its hole and their by predisposes to failure.

Stability depends on the locking screw diameter for a given nail diameter. In general, 4 to 5 mm for humeral nails and 5 to 6 mm for tibial and femoral nails.

Nail hole size should not exceed 50% of the nail diameter.

Interlocking screws undergo four-point bending loads, with higher screw stresses seen at the most distal locking sitesThe number of locking screws is determined based on fracture location and stability.

In general, one proximal one distal screw is sufficient for stable fractures.The location of the distal locking screws affects the biomechanics of the fracture .

The closer the fracture to the distal locking screws, the nail has less cortical contact , which leads to increased stress on the locking screws.

More distal the locking screw is from fracture site, the fracture becomes more rotationally stable .

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Orientation of the proximal femur locking screws has little effect on fixation stability, with both oblique and transverse proximal locking screws showing equal axial load to failure.

. - Oblique ( angled to nail axis, not 90) proximal locking screws appear to increase the stability of proximal tibia fractures compared with transverse ( 90 to nail axis) locking screws.

However, oblique or transverse orientation of the distal screws in distal-third tibia fractures has minimal effect on stabilityEXTREME ENDS OF NAILSK-nail has slot/eye in the either ends for attachment of extraction hook .one end is tapered to facilitate the insertion .

Present version of cannulated locking screw contains cylinderical proximal end with internally threaded core to allow firm attachment of driver and extracter.Holes for interlocking screws present either ends .

Some nails have slots near the distal end for placement of anti rotation screw

Slot- Anterior slot - improved flexibility- Posterior slot - increased bending strengthNon-slotted - increased torsional stiffness, increased strength in smaller sizes. Unknown if its of any clinical advantage.CLOSED AND OPEN NAILINGClosed nailing :- Fluoroscopy is used to achieve fracture reduction . - Medullary cavity is entered through one end of the bone antegrade .eg-Piriformis fossa in femur .Closed antegrade nailing is the method of choice .

Open nailing :- Performed in lessthan ideal operation room conditions - Antegrade nailing is prefered .- In retrograde method nail is inserted in to the proximal fragment through fracture site and brought out at one end of the bone ,after reduction nail is driven in to the distal fragment - Infection and non union is six and ten times greater in open nailingFRACTURE REDUCTIONThe earlier a fracture is nailed, easier is the reduction. Shortly after injury, the hydraulic effects of edematous fluid can cause shortening and rigidity of the limb segment, which may make fracture reduction extremely difficult. If nailing is not done before this degree of edema, gentle traction may be required to regain length and alignment gradually.

In femur, the reduction is most easily achieved by placing the distal fragment in neutral position, avoiding tightness of the iliotibial band, which could otherwise result in shortening and a fixed valgus deformity.

As the tibia is subcutaneous, direct manipulation results in reduction in most cases.- In upper extremity, reduction is achieved by a combination of manipulation of the proximal fragment with the nail and direct manipulation of the distal fragment and fracture site .- In open nailing, the key to reduction is to angle the fracture. - The corners of the cortices of the proximal and distal fragments are approximated at an acute angle, and the fracture is then straightened into appropriate alignment.

ENTRY SITES:With reamed rods, which are generally fairly rigid, the entry site must be directly above the intramedullary canal. Eccentric entry sites, particularly in the femur and tibia, can result in incarceration of the nail or comminution.

For nonreamed, flexible nails, an eccentric entry site is usually used to take advantage of three point fixation of the curved nail within the medullary canal. Generally these nails are inserted distally through the supracondylar flares of the long bones

66ENTRY SITES

The entry site for reamed nails is in the thin cortex at the base of the greater trochanter at the site of its junction with the superior aspect of the femoral neck.ANTEGRADE NAILING FOR FEMUR:

Most usual entry point is just lateral to the to articular surface of the humeral head and just medial to the greater tuberosity

Tibia nailing direct route is through the patellar tendon into the bone just proximal to the tibial tubercle , but to avoid injury to the patellar tendon, most surgeons now enter just medial to the patellar tendon

Retrograde IM nailing

3 cm longitudinal incision approximately 1 cm from the medial border of patella, beginning about 2 cm proximal to distal pole of the patellaA cortical window was made at tip of radial styloid and MICRONAIL was inserted with help of jig.3 distal locking screws inserted

BIOMECHANICS OF IM REAMINGIM reaming can act to increase the contact area between the nail and cortical bone by smoothing internal surfaces.

When the nail is the same size as the reamer, 1 mm of reaming can increase the contact area by 38% .

Reaming reduces the working length and increase the stability.

More reaming allows insertion of a larger-diameter nail, which provides more rigidity in bending and torsion. Biomechanically, reamed nails provide better fixation stability than do unreamed nailsMedullary canal is more or less like an hour-glass than a perfect cylinder. Reaming is an attempt to make the canal of uniform size to adapt the bone to the nail. The size of the canal limits the size of the nail.

Reamers must be sharp, and the surgeon must consider the relationship between the size of the reamers and the nail.A 12mm reamer is not necessary equal in diameter to a 12mm nail. Because flexible reamers follow a curvilinear pathway, overreaming is usually necessary for most nails. Most nail require overreaming from 0.5 to 2mm over the size of the nail, depending on the type of nail, the configuration of the fracture, and the canal of the bone.

75REAMING TECHNIQUE:Insert a ball-tipped reaming guide pin across the fracture to the subchondral bone in the distal fragment begin with an end cutting reamer, generally 8.5 to 9.0 mm in diameter.

On the first pass of the reamer past the fracture site, visualize it on the fluoroscope to ensure that reaming is progressing appropriately.

It is safest to ream progressively in 0.5 1mm increments.76REAMING TECHNIQUE

LOCAL CHANGES:Both reamed and unreamed nails cause damage to the endosteal blood supply. Experimental data suggest that reamed nailing deleteriously affects nutrient artery blood flow, but cortical blood supply is significantly reduced after reamed nailing compared with unreamed nailing.Reaming is also associated with the potential risk of fat necrosisBlunt reamers and the use of reamers larger in diameter than the medullary canal Lead to increased temperature , therefore it suggested that long bones with very narrow canals should first be reamed manually or an alternative treatment method should be used.78LOCAL CHANGES:Some surgeons believe that unreamed nailing is advantageous in the treatment of Gustilo III B open fractures, citing higher infection rates.Clinical studies of both tibial and femoral fractures show that reamed nailing of fractures with low grade soft tissue injuries significantly reduces the rates of nonunion and implant failure in comparison with unreamed nailing. In fractures with an intact soft tissue envelope, reaming of the medullary cavity increases significantly the circulation within the surrounding muscles. This increased circulation may improve fracture healing Reaming does not increase the risk of compartment syndrome.

79SYSTEMIC CHANGESFat embolism due to IM reaming was described by Kuntscher. Fat embolism due to passage of IM contents into the bloodstream can occur only in the IM pressure associated with instrumentation exceeds the physiologic IM pressure and out weighs the effects of the normal blood flow.

The incidence of fat embolism is more with femoral reaming,. Reaming of the tibia does not lead to a significant increase of IM pressure, and intraoperative echocardiography does not show significant fat embolism in reamed tibial fractures.

The use of a venting hole to reduce the IM pressure increase during reaming is controversial.

80Advantages

Allows insertion of larger-sized implants which helps in weight bearing and joint function during the healing process.- Improves nail-bone cortical contact across the working length of the implant and directs fracture fragments into a more anatomical position.- From a biologic standpoint, provides systemic factors to promote mitosis of osteogenic stem cells and to stimulate osteogenesis.

Disadvantages

Eccentric reaming may lead to malreduction of the fracture.

- Destroys all medullary vessels, resulting in a initial decrease in endosteal blood flow and in turn decreased immune response and delay in early healing of the involved cortices.

- In open fractures, avascular and nonviable fragments causes increased susceptibility to infections.

Side effects- Heat: a rise in temperature upto 44.6 C had a negative effect on fracture healing.Cell enzymes get damaged and cannot fullfill their function.The threshold value of heat induced osteonecrosis is 47C.- Pressure: hydraulic pressure builds up in the cavity which far exceeds that of blood pressure and is independent of the size of the reamer.It acts as a piston in sleeve which is filled with a mixture of medullary fat, blood, blood clots and bone debris.High intramedullary pressure forces contents into the cortical bone and systemic circulation.TECHNIQUE FOR INTERLOCKING:A long, very sharp awl, mounted on a T handle, must be used to pinpoint the area of penetration of the bone to avoid exposing the surgeons hands to the direct beam of the fluoroscope.

Bring the awl into the fluoroscope image, placing it directly over the screw hole image. Mark the location for the skin incisions.

Make a 1 cm longitudinal incision directly over the screw hole. Insert the awl percutaneously to the cortex of the bone. 83Again, bring the tip of the awl into the fluoroscopic image at an angle to the fluoroscope beam and locate the tip of the awl directly in the middle of the screw hole, make a hole in cortex.

Once this hole is made, insert the appropriately sized drill point and, while maintaining alignment with fluoroscope head, drill the hole through the rod and medial cortex.

Verify its position on the anteroposterior view, and then insert the appropriately sized screw.

Lateral fluoroscopic view of the distal screws in Grosse Kempf nail:The hole, which is to be cross locked is in the center of the screen and is perfectly superimposed85WEIGHT BEARING AFTER IM NAILINGSegmentally comminuted diaphyseal fracture without bony contact and nails with a 12-mm diameter and two distal locking bolts could with stand the typical biomechanical forces of weight bearing.

In patients who retain diaphyseal bony contact after fracture fixation, nails with a diameter