K NAIL- HISTORY, DESIGN AND BASIC PRINCIPLES

DEEPAK CHAUHAN (J.R.orthopaedics)

MODERATOR-Prof.VIJAY G.GONI

History of Intramedullary nailingThe beginnings -16th century In Mexico aztec physicians have Placed wooden sticks in to the

medullary canal of patients with long bone non-unions.

Mid 1800s Ivory pegs were inserted in to

the medullary canal.In 1917s-hoglund of the united states

reported use of autogenous bone as intramedullary implant

Evolution of KÜNTSCHER NAILING

Gerhard Küntscher was born in1900 in Germany. Development occurred during World War-2(1939-42) while Germany was at war, Küntscher was deployed as Chief medical officer in german army. The german military had the upper hand in treating soldiers with the IM nail and having return to fighting status in few weeks. Worldwide knowledge was not established Until prisoners of war returned to their home Countries carrying Kuntscher legacy in form of Of Steel nail in their legs.

The technique of femoral neck nailing described by smith –peterson has been expanded by Küntscher for the nailing of long shaft bones.

His original intramedullary nail was a V-shaped stainless steel that was inserted antegrade.

Küntscher first reported use of V-shaped nail in 1940.

Early in the development of his technique,he recommended inserting the nail through a portal remote from fracture site-differs from all operative fracture methods used in the past.

By late 1940- küntscher abandon use of the V-shaped nail design in favour of another design-the cloverleaf nail.

Küntscher first nail in a human was inserted in 1939 & reported at university of Keil medical society on dec 1939.

His method was essentially unknown in U.S. during war and was first Described in US march,1945,Time magazine article,entitled“Amazing Thighbone”.

Küntscher published his his first book in 1945 on intramedullary nailing.

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Principle of KÜNTSCHER nailing (GERHARD B. G. KÜNTSCHER J Bone Joint Surg Am. 1958;40:17-26.)

The basic principle -stable osteosynthesis through - flexible impingement of nail in the bone

- adequate friction of the nail in both fracture fragments .

The device firmly impinged in the bone by elastic forces in such a way that a carpenter’s nail becomes impinged in wood.

However the analogy does not follow in every detail.As in cross section a carpenter’s nail is almost

rigid,when driven in to wood,it pushes wood aside.by contrast medullary cavity is quite rigid; therefore to achieve elastic impingement,the cross section of nail must be design to have elasticity with a V profile or even better clover-leaf design.

Drawings showing cross sections of two types of intramedullary nails.the V nail is compressible in only one direction,whereas the

clover-leaf nail is compressible in two directions,these directions being right angles to each other.

V - nail Cloverleaf nail

A SIMPLE EXPERIMENT DEMONSTRATES THE ELASTIC COMPRESSIBILITY OF THE CLOVER –LEAF NAIL.If a clover –leaf nail 12mm in width is mounted in to a vise,it can be compressed about 3 mm but will immediately recover its original shape,when released from the vise.

Use of this principle of elasticity will achieve the idea of complete and permanent immobilization of the fragments and offers an absolute guarantee of bone union.There are two reasons for this:

1.Lateral movement can be eliminated only if the nail occupies the entire width of canal througout its length.this can’t be accomplished with a solid rod which can not be compressed for varying canal width.

A solid nail (left) will not occupy the full width of the medullary canal in most places since its

diameter must be selected to fit the narrowest portion of the canal. A nail with an elastic cross section (right ) will adjust to

the constrictions of the medullary canal.

Solid nail Elastic nail

2.The second reason also of great importance.

.Bone resorption will soon loosen a solid rod(left),even though at first this rod accurately fit inside canal.

. However nail with a compressible cross section (right)will expand during bone resorption

. This nail is designed to render the mechanical effects of bone resorption ineffective.

Solid nail elastic nail

DESIGN-femoral ‘K’ nail (THE TECHNIQUE OF INTRAMEDULLARY NAILING GERHARD KÜNTSCHER, MD and RICHARD MAATZ, MD Professor ReaderSurgeons, Department of Surgery, Kiel University Hospital

Cross section-roughly V or cloverleaf shaped

Sheet metal thickness reduced on back-provides compressibility

Hollow core-admits guide wireSlot-anterolaterally tension sideEye- at both endsCommon sizes-lengths-

30,34,36,38,40,42cm diameter-8,9 and 10 mm

Protude at least 3cm from trochanter Standard femur K nail-

Special designsTapered end- subtrochanteric

fractureY nail- peritrochanteric fracture

Some cases Saw teeth at its tip- for bone containing central callus.eg-refracture,delayed union

TIBIAL NAILSDouble nailsCurved in shapeCross section-U shapedLengths-24-39 cm,at 1.5 cm

increments largest diameter-8 and 9 mmTwo designs of spreading nail- Deflect to spread nail Rotate to spread nail

Deflect to spread nailTwo nails spreads distally by means of an

inclined plane on outer nail

The inclined plane on outer nail & rear wall of bone tube provides deflecting surfaces - make inner nail veer in posterior direction

Outer nail should be inserted first.Resistant to bendingUsed in fractures distal to isthmus-long

oblique fractures or segmental bone loss(anterior edge).

Rotate to spread nailAlso consists two nailsOuter nail-standard patternInner nail-circular cross section

and a lazy S shape

Inner nail should be inserted firstOnly for transverse or short

oblique fractures,bone loss(posterior cortex)

A=outer nailB=inner nail

Instruments Nail guide-solid,circular cross

section Length-64 cm,diameter-3mm Awl- with an offset four sided tip

Impactor-facilitates insertion of nail,allows hammer blows directed along main axis of middle portion of nail.

nail guide

Awl

Tibial nail impactor

Slotted hammer-most suitable instrument for extraction even very firm seated nail

Kuntscher extractor-threaded rod& Spring system combines traction

and hammer blows. pretension needs to reset with every blow

Slotted hammer with extraction hook

c b

aa=threaded rod with fitting for hammerb=spacer=prevent bone damage at instrument placement siteC=extension

Reamers-

Nail bender- allows nail contouring(other than femoral nails)

Stepped scale- for radiographic determination of medullary cavity diameter

Reduction apparatus-

Positioning

Küntscher policies:1.if a fracture is “nailable” it should be

nailed.2.nailing will be done in patients that are

at particular risk if kept at bed rest in cast or on traction.

3.nailing will be performed to manage fractures that are notoriously difficult,such as smooth transverse fracture.

4.one particular indication in spontaneous fracture of metastatic bones.

Uses

Fractures- femur ,tibia,humerus,forearm,clavicle.

Compound fractures,gun-shot fractures.

For non union,delay union.Correction of malunion.Congenital or aquired deformitiesarthrodesis

Criteria of nailing- fractures?Criteria of nailing will depend on shape of the boneSite of the fracturePattern of fractureThere are no definite cut –offs between suitability

grades- this is why fractures are best classified as “very suitable”-absolute indications

“suitable” “borderline” extended indications “unsuitable”

Intramedullary nailing is ruled out in all intra-articular fractures :

nail may force fragments apart that are still in reasonable contact.

the device will not be able to obtain an adequate purchase.

the joint may be at risk from nail intrusion.

Femur fractures-nailing criteriaVery suitable-transverse fractures

and oblique fractures with a short-fragment medullary cavity providing at least 8 cm of “nail-suitable” medullary cavity.

Secure against angulation,lateral displacement and shortening.

Risk of rotation-little in oblique fracture,more with transverse fracture

Immediate weight bearing allowed

“Suitable” fractures- spiral fractures

well secure against angulation and lateral displacement.

Shortening will occur with rotational malalignment-as smooth fragments will slip past each other when loaded.

No weight-bearing before the end of 3rd week.

Unsuitable fractures- supracondylar fracture with

separation of condyles(Y or T fracture)-

Peritrochanteric fractures-head end of standard nail would not obtain sufficient purchase in trochanter..but they are very suitable with Y nail.

Butterfly and segmental fractures

very suitable-large fragments with a bone defect on one side OR non-communited third fragment in segmental fracture.

.Lateral dispalcement ruled out.secured against angulation..shortening is not possible-one side continuous cortex..immediate weight bearing

Communited fractures- “suitable”

secure against displacement and angulation.

Great risk of shortening and malrotation.

Supplementary support –skeletal traction may require

Weight bearing once sufficient callus formed.

Tibia fracturesCompared to femur –conditions

are more adverse.Nail has to be curved-since

introduced from lateral entry point.

Very frequently producing displacement of fracture in to recurvation.

Unlike femur,most of the thing depends on shape of medullary cavity..

Nailing criteria :tibia fractures criteria of nailing in tibia dependson diameter of the nail (n) diameter of medullary cavity

at fracture site (m) thickness of cortex (k)If m-n<_k the fracture is

“suitable”(depending on fracture pattern).

If m-n>k the fracture is“unsuitable”

Proximal -third transverse fractures-The difference

between medullary cavity diameter and the nail diameter is equal to or greater than thickness of the cortex.In all these cases all fracture patterns are “unsuitable” with the standard nail.

Fragments are secured against rotational only,but may displace in all other directions

. m-n<k (borderline)

. lateral dislacement. protected against all other displacements by great friction b/w bone & nail at x.

.No supplementary support require..moblization at end of 3 week

Proximal third oblique fractures (border line)

.conditions are same like oblique fractures but there is strong torque forces which can not be neutralize by nail..Supplementary long leg cast requiredProximal third (spiral

fractures)-”borderline”

“Unsuitable”(m-n>k)since the nail can not prevent major anguation

Proximal third Butterfly and Communited fractures

Middle -third tibia fracturesHere the diameter of the medullary

cavity will be the same as that of nail-all fractures in this part suitable for nailing.

Nail will fit snugly & provide adequate friction

Transverse fracture & oblique fracture- “very suitable” .

Spiral fractures- “suitable”as risk of rotation

Middle third butterfly fractures-“Borderline”-for standard nail Very suitable- for spreading nail . An anterior

butterfly fragment should be managed with deflect to spread nail.

.A posterior fragment –managed with rotate to spread nail.

Distal third tibia fracturesSpreading nail are useful-splayed

pattern at distal end of this double nail provide greater overall diameter.

Oblique or transverse fractures: m-n<k “unsuitable for standard double nail very suitable -spreading nail.

Nail removal.Earlier removal may be indicated in

following: 1.displaced fragments and nail is

making impossible to obtain reduction. 2.migrating nail-threatening joints or

soft tissue at its end 3.bent or broken nail 4.in children after achieving sound

union.

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