Nonreamed nails are actually not nails but pins. ir mechanical characteristics and use are different from IM nails. y are of smaller diameter and are more elastic. ir flexibility allows insertion through a cortical window. re are many different types of flexible nails, best known are:- Lottes nails - Tibia Rush pins – for all long bones of body Ender nails
required precurve should be approximately 3 times diameter of a long bone at its narrowest point. Part of biomechanical stability is provided by intact muscle envelope surrounding long bone. beaked or hooked ends to allow satisfactory sliding down on insertion along inner surface of diaphysis without impacting opposite cortex. Two nails of same diameter and similarly prebent to be used. Insertion points that do not lie opposite to one anor produce differing internal tension and imbalance of fracture stability and fixation.
avoid early weight bearing following use of TENs in treatment of paediatric femoral fracture due to pain and muscle spasm in immediate period after surgery. We recommend start of weight bearing to be delayed until appearance of early callus formation at three to four weeks time following fixation. This in fact will furr support TENs that function eventually will become redundant once callus fully consolidate.
equilibrium between tensioned pin and bone with its attached soft tissues will hold alignment
Various types of load act on an IM nail: torsion, compression, tension and bending Physiologic loading is a combination of all se forces Various types of load act on an IM nail: torsion, compression, tension and bending
It should be strong enough and provide sufficient stability to maintain alignment and position, including prevention of rotation; it should include interlocking transfixing screws as necessary. It should be constructed so that contact-compression forces can impact fracture surfaces, a desirable physiological stimulus to union. It should be placed so that it is accessible for easy removal; attachments are provided to facilitate removal
Modulus is ability to resist deformation in tension cross-sectional shape of 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 edge length
Nails with Sharp corners or fluted edges has more polar movement inertia
Cloverleaf design resist bending most effectively .Presence of slot reduces torsional strength . It is more rigid when slot is placed in tensile side
Cloverleaf design resist bending most effectively Presence of slot reduces torsional strength It is most rigid when slot is placed in tensile side (anterolateral) Slot in compression side buckling
diameter of a nail should always be measured with a circular guage.
In reamed nailing, width of nail is better determined by feel of reamers than by radiographic measurements, although approximate size to be used can be determined from preoperative radiographs.
Governs how easily a nail can be inserted as well as bone/ nail mismatch, in turn influences stability of fixation of nail in bone.
Biomechanically, unlocked nails attain stability by a curvature mismatch between bone and nail, inducing a longitudinal interference fit.
When inserting nail , axial force is necessary as nail must bend to fit curvature of medularly canal .
insertion force generates hoop stress in bone ( Circumferential expansion stress )
Greater insertion force higher hoop stress. Larger hoop stress can split bone
-Length of a nail spanning fracture site from its distal point of fixation in proximal fragment to proximal point of fixation in distal fragment
Un supported portion of nail between two major fragments
Surgeon’s Techniques to modify L 1.Medullary reaming Prepares uniform canal improves nail-bone contact Decreases L 2. Interlocking Fixing nail to bone at specific points
Medullary reaming prepares a uniform canal and improves nail- bone fixation Towards the fracture,thus reducing the working length.
The 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.
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 sites
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 stability
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.
Medullary 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 nailIM 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 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
With all metallic implants, there is a relative race between bone healing and implant failure.
Spectrum of indications has been extended by newer invention and techniques
Fracture stabilized by one of two systems
Intramedullary fixation - internal splinting
Splintage -micro motion between bone & implant
Relative stability without interfragmentary compression.
Entry point - distant from fracture site – hematoma retained.
Closed reduction and fixation (biological)
Eg –K nail , V nail
• Locking screw -
• Non- slotted.
• Eg-russel taylor nail,
• Fit anatomically as
much as possible
• Aid insertion and
• Titanium alloy
• Eg-trigen nail, universal
femoral nail nails with
• Tibial nail with
Entry Portals :
Russell taylor nail
Contained within medullary canal
Usually inserted from piriformis fossa
Proximal locking bolts - transverse or
oblique in pertrochanter
Requires LT be attached to proximal
fragment for adequate # stabilization
second generation nails
More efficient load transfer than SHS
Shorter lever arm of IM device decreases
tensile strain on implant - low risk of implant
screws/blade inserted cephald into femoral
head and neck.
C o n d y l o c e p h a l i c F i x a t i o n
Elastic stable intramedullary nailing (ESIN) - primary definitive
paediatric fracture care .
3 – point fixation or bundle nailing.
Elastic and small - micro-motion for rapid fracture healing.
Flexible -insertion through a cortical window.
Opposite Apex of curvature - at level of fracture
Nail diameter - 40% of narrowest
medullary canal diameter
Entry point - opposite to one another
Used without reaming.
Commonest biomechanical error is lack of
Schneider nail [ solid, four fluted cross section
and self broaching ends.
Harris condylocephalic nail [curved in two
planes, and designed for percutaneous,
retrograde fixation of extra capsular hip
Lottes tibial nail specially curved to fit tibia,
and has triflanged cross section.
Solid pins with oblique tip and an eye
in flange at or end
Designed for percutaneous, closed
treatment of extra capsular hip
Intended for fractures of diaphyseal
or metaphyseal fractures of long bones
like femur, tibia, febula, humerus,
radius and ulna.
Pointed tip facilitates easy insertion.
Curve at top prevents rotation and
C- or S – shaped, act like spring.
Principle introduced by hackethal.
Many pins are inserted in to bone until
jammed within medullary cavity to provide
compression between nails and bone.
Bending movements neutralized, but
telescoping and rotational torsion not
Diaphyseal fractures of long bones
High proximal and low distal fractures of
Floating hip, floating knee, floating elbow.
Aseptic and septic non-union
Osteoporotic long bone fractures
Open fractures up to grade IIIA
Narrow and anomalous medullary canal
Open growth plates
Prior malunion - prevents nail placement
History of intramedullary infection
Associated ipsilateral femoral neck or acetabular fracture (relative)
Mechanics (K Nail)
Elastic deformation or “elastic
locking” of nail within medullary
Adequate friction of nail in both
To achieve elastic impingement-
“V” profile or even better “clover-leaf”
Compressible in two directions
Directions right angles to each
V Nail Clover Leaf Nail
Compressible in only one
F = Force Bending moment = F x D
Bending moment for plate
greater due to force being applied
over larger distance.
D = distance from force
• Nail cross section round
• Resisting loads equally in all
• Plate cross section
rectangular resisting greater
loads in one plane versus the
- compressive loads borne
by bony cortex
- compressive loads
transferred to interlocking
screws (“four-point bending
of screws ”)
Ideal Intramedullary Nail
Strong and stable - maintain alignment and position
Prevent rotation - interlocking transfixing screws
Promote union - contact-compression forces at fracture
Accessible for easy removal
Adequate preoperative planning
Patient tolerance to a major surgical procedure
Availability of nails of suitable length and diameter
Suitable instruments, trained assistants, and optimal hospital
Closed nailing techniques - whenever possible
Pre Operative Planning
• Bone Morphology
• Canal Dimensions
• Fracture Personality
• Fracture Extensions
Length Of Nail
• Radiographs of contra lateral
• Traction radiographs
• Palpable greater trochanter to
• TMD (tibial tubercle–medial
malleolar distance) for tibial
Diameter Of Nail
• Narrowest portion of
femoral canal at femoral
isthmus – lateral
• 1.0 to 1.5 mm greater in
diameter than anticipated
Preoperative radiographs of fractured long bone
with proximal and distal joints
AP radiograph of opposite normal limb at a tube
distance of 1meter
Kuntscher measuring device :
Ossimeter used to measure length and width
Magnification is taken in to account
Stability determined by
Number and orientation of locking screws
Distance of locking screw from fracture site
Reaming or non reaming
Quality of bone
IM nails assumed to bear most of load initially,gradually
transfer it to bone as fracture heals.
Factors contributing to biomechanical profile :
Length and working length
Ends of nail
Titanium alloy and 316l
Modulus of elasticity
Titanium alloy – same as
SS – twice as cortical bone
Determines bending and
Polar moment of inertia
Circular nail diameter
Square nail edge length
High in nails with sharp
corners or fluted edges
Nail diameter affects bending rigidity
solid circular nail,
Bending rigidity third power of nail
Torsional rigidity fourth power of
Large diameter with same cross-
section are both stiffer and stronger
than smaller ones.
Long bones have curved medullary cavities
Nails contoured to accommodate curves of bone
Straight, curved or helical
Average radius of curvature of femur - 120(±36) cm.
Complete congruency minimizes normal forces and
hence little frictional component to nail’s fixation.
Femoral nail designs have considerably less curve,
with radius ranging from 150 to 300 cm
Im nails - straighter (larger radius) than femoral canal
Angle of herzog :
11o bend in AP direction at junction of upper
1/3rd and lower 2/3rd of tibia nail
Mismatch in radius of curvature –
Distal anterior cortical perforation
more reaming required during insertion
Circumferential expansion stress
during nail insertion
Larger hoop stress can split bone
Hoop stress reduction :
Use flexible nails
Over-ream entry hole by 0.5 to 1 cm
Selection of ideal entry point
Posterior - loss of
Ideal - posterior portion
of piriformis fossa
Anterior - generates
huge forces, can lead to
bursting of proximal
A-Total nail length - Anatomical length
B-working length - length between proximal and
distal point of firm fixation to
Affected by various factors
Type of force (Bending ,Torsion )
Type of fracture
Interlocking and dynamization
Shorter working length stronger fixation
Transverse fracture has a shorter working length than
Torsional stiffness 1/ to l
Bending stiffness 1/ to l2
Surgeon’s techniques to modify “ l ”
Slot/eye in ends for extraction
One end tapered to facilitate insertion .
Holes for interlocking screws
Some nails have slots near distal end
for placement of anti rotation screw
Posterior slot -
stiffness and strength
in smaller sizes
Interlocking of nail
Recommended for most cases of IM nailing.
Resistance to axial and torsional forces depends on
screw – bone interface
Length of bone maintained even in bone defect.
Number of interlocks :
Amount of fracture comminution
Fit of nail within canal.
Placing screws in multiple planes - reduction of minor movement
Location of distal locking screws affects
biomechanics of fracture
Distal locking screws
Closer to fracture site - less cortical contact -
increased stress on locking screws
Distal from fracture site - fracture becomes
more rotationally stable
Interlocking screws positioned at least 2 cm
from fracture provides sufficient stability
Poller /blocking screws
Centers IM nail.
Planned and inserted before
IM nail insertion.
Saggital or coronal plane.
Screws placed proximal and distal to fracture site
Restrict translation and rotation at fracture site.
Acts as a “bridging fixation”
Fractures with bone loss
Atropic non union
Screws inserted only at one end (short fragment)
Unlocked end stabilized by snug fit inside medullary cavity
Prerequisite: at least 50% cortical circumferential contact
Fractures with good bone contact
With axial loading , working length in bending and torsion is
reduced - improving nail-bone contact
Never done in progressive normal healing
Caution: premature dynamisation adds to
shortening, instability and non-union.
Dynamic locking of axially and rotationally stable
fractures at time of initial fracture fixation
Removing interlocking screw from longer fragment
/ moving proximal interlocking screw from static to
dynamic slot in nail
Done in long bone delayed union and nonunion
Reamed Versus Unreamed
Endosteal thermo-necrosis & endosteal cortical blood supply disruption
Minimized by using sharp reamers with deep cutting flutes.
Reaming - slow and smooth.
Endosteal blood supply regenerates rapidly - high healing rates in reamed
No difference in infection rates
No overall difference in time to union
Reamed Versus Unreamed
Reamed nail :
High chance of embolization of bone marrow fat to lungs but this phenomenon is limited &
Fat extravasation greatest during insertion of nail in medullary cavity
Not dependent upon increased intra medullary pressure
Reamed nailing generally report no statistical difference in pulmonary complications
as compared to unreamed nailing
Open intramedullary nailing
Primary indication :
Failure to do closed nailing
Fractures requiring intramedullary fixation in existing
internal fixation device.
Less expensive equipment required than for closed nailing.
No special fracture table / preliminary traction
Absolute anatomical reduction
Direct observation of bone - undisplaced / undetected comminution
Improved rotational alignment and stability.
Prevents torquing and twisting in segmental fractures
In nonunions, opening of medullary canals of sclerotic bone is easier.
Fracture hematoma evacuated.
Bone shavings created by reaming medullary canal often are lost.
Infection rate increased.
Rate of union decreased.
If a locking nail is used, locking is difficult without image intensification
Nailing in open fractures
If initial debridement adequate and timely , definitive stabilization with
reamed intramedullary nailing
with severe soft tissue injuries that require a second debridement,
temporary external fixation reasonable
increased risk of infection after use of external fixation pins longer than 2
weeks followed by reamed intramedullary nailing.
Rapid initial management approach allows delayed conversion to a
medullary implant at 5 to 10 days.
Nailing in open fractures
Fractures with delay in initial debridement of more than
8 hours - staged nailing.
Acceptable complication rate (11 % infection rate in type
iii open fractures)
No relationship between infection rate, non union with
timing of nailing or associated soft tissue injury
Aseptic non unions
Without bone defects - primary im nailing or exchange
nailing if well aligned
With bone defects - im nailing with bone grafting
corticocancellous graft material - harvested with
ria(little donor morbidity)
Biological effects :
Reaming of medullary canal – promotes union
Mechanical effects :
Larger-diameter intramedullary nail – improved
Exchage nail – atleast 1mm larger than
Canal reaming until osseous tissue observed
in reaming flutes
Removal of current
Reaming of medullary
Placement of an larger
Septic non union
Main aim - eradicating infection
Osseous stability important in management of infected nonunion
Stabilization with antibiotic impregnated cement coated nail after serial
Cement nail elute high concentration of antibiotic in local sites for up to 36 weeks.
Nailing in damage control orthopaedics (DCO)/early total care (ETC)
In polytrauma , early femoral stabilization decreases incidence of
severe fat embolism and pulmonary complications (ARDS).
Nailing with reaming will not increase pulmonary complications
Early intramedullary nailing may be deleterious and is associated with
elevation of certain proinflammatory markers - (il)-6.
Early external fixation of long bone fractures followed by delayed
intramedullary nailing – high risk patients.
Nailing in damage control orthopaedics (DCO)/early total care (ETC)
50% (↓) in mortality patients who underwent femoral shaft
fracture stabilization beyond 12 hours
This timing was hypothesized to allow for adequate
Exact and optimal timing of femoral shaft fracture nailing
remains unclear in polytrauma(esp. Chest injuries)
Patient request(after union)
Pain, swelling secondary to backing out of implant.
Full weight bearing immediately after removal
Femoral nail removed after 24-36 months , tibial nail 18-24 months
When fracture healing is delayed or nonunion occurs.
IM nails usually fail in predictable patterns.
fail at fracture site or through a screw hole or slot.
screw breakage or fracturing of nail at locking hole sites(proximal
hole of distal interlocks )
Nickel-titanium shape-modifiable alloys
can improve stability as they change shape after
insertion and recover curvature as they warm.
IM nails coated with bmp
Implant of choice in diaphyseal fractures
Multiple factors determine final construct stiffness,
should be understood and considered when
choosing IM nail
Ideal intramedullary nail is yet to be invented
Campbell operative orthopaedics 12th edition
Rockwood and green – fractures in adults 8th edition
Elements of fracture fracture fixation – anand J.Thakur(3rd edition)
History of intramedullary nailing ,matw R. Bong, M.D., Kenneth J.
Koval,m.D., And kenneth A. Egol, M.D., Bulletin of NYU hospital for
joint diseases • volume 64, numbers 3 & 4, 2006