Dynamic External Fixation System - Operative Guidelines

Operative Guidelines

Dynamic External Fixation System

l Ease of Application

l Possibility to reduce fracture with minimum Instrumentation

l Post operative repositioning of the Bone possible

l Ability to compress or distract

Office & Works :

EL - 32, " J " Block, MIDC Bhosari, Pune 411 026 India.

Tel : 91-20- 27129462, 27129448 Fax : 91-20-46768107

Email:[email protected]

www.pitkar.com

Developed with scientific & clinical inputs

from Dr. Mangal Parihar ,

orthopedic surgeon,

Sir H. N. Hospital, Mumbai, India.

S. H. PITKARORTHOTOOLS PVT. LTD.

In the past, surgeons often reserved external skeletal fixation for the most severe types

of fracture, especially those associated with extensive damage to the soft tissues. This

was due largely to the type of equipment available, which at the time, was heavy,

cumbersome and difficult and time consuming to apply. Furthermore, these early

external fixation devices were expected to provide a measure of rigidity similar to that

provided by internal fixation with a plate and screws. In the latter instance, fractures

unite by the extremely slow process of primary bone healing, without the formation of

external bridging callus. Under the conditions of total rigidity provided by a plate and

screws, union may take in excess of one year and refracture and time-related osteolysis

are recognized complications.

It has also been suggested that optimal primary bone healing will not be achieved if

movement at the fracture site is more than 5-10 microns. In practice it is extremely

difficult to avoid a movement of less than 10 microns with any external fixation device ,

and with this type of equipment therefore, primary bone healing is discouraged.

On the other hand, the devices originally available did provide a substantial measure of

uncompromising rigidity which, while valuable in the early stages of fracture healing, did

not encourage the formation of external bridging callus, which is dependent upon some

movement at the fracture site.

It therefore follows that conventional external fixation devices may encourage neither

primary bone healing, nor external callus formation to best advantage, resulting in a

prolongation of overall healing time. These features', together with the fear of pin track

infection, accounted for the understandable reservations expressed by many surgeons

regarding the use of external skeletal fixation.

The lightweight, unilateral Dynamic External Fixation (DEF) was designed specifically to

address the problems inherent in classical external fixation techniques and thereby to

widen the applicability of this form of fracture treatment far beyond its original confines.

To this end it has undergone extensive bio-mechanical evaluation at various locations.

The basic philosophy of fracture treatment with the DEF is respect for, and enhancement

of the natural physiological process of fracture healing, which demands rigidity in the

early stages and a degree of movement at the fracture site in the later stages of the

healing process. The manner in which the DEF achieves this is summarized below:

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THE DYNAMIC EXTERNAL FIXATION PHILOSOPHY

Dynamic External Fixation SystemDynamic External Fixation System


1. Minimal disturbance of the fracture site in the initial period following

fracture

a) The DEF provides a degree of stiffness comparable with that of the double frame

Hoffmann-Vidal fixator controlling lateral bending and torque forces during the

initial phase of treatment.

This stability derives in part from alignment of the body of the DEF with the long axis

of the bone to be treated, partly through the inherent rigidity of the device and the

screws, and partly as a result of screw geometry. The ability to lock the body in the

rigid mode, allows early mobilization and weight bearing, encouraging bone

metabolism.

b) The screws are placed in the bone on either side of, and well away from the fracture

site. The net result is to permit organisation of the haematoma to proceed under the

most favorable conditions possible, and to allow the initial external callus collar to

form.

2. Stimulation of external bridging callus formation at the appropriate time

in the healing cycle, by controlled axial movement

The DEF incorporates a telescopic function within its body, which can be activated at

any given time by loosening a locking nut. This immediately converts the DEF from a

rigid to a dynamic mode, which allows a minute and controlled amount of movement

to occur at the fracture site (Dynamisation) on partial or complete weight bearing,

while preventing torque and rotational forces. Following release of the locking nut,

good alignment is maintained and abundant external callus formation encouraged,

leading to rapid union of the fracture.

The precise time at which dynamization should occur is dependent upon a variety of

factors.

It should also be noted that this same telescopic function can be adapted to provide

controlled distraction or compression which may be indicated in certain situations

e.g. limb lengthening and the treatment of non-unions of bone.

3. Minimisation of complications by respecting bone biology

The major problems with external fixation, which have prevented it from replacing

internal fixation in many indications, are pin track infection and pin loosening. These

are frequently a consequence of flexion of the screws on weight bearing. The design


of the screws is a major feature of the system and plays an important role in the

prevention of pin-associated problems.

The screws used are tapered, self-tapping screws differing in pitch design

depending upon whether they are to pass through cortical or cancellous bone. In

either case the pitch is constructed to produce optimal bone grip with minimal

damage to bone substance.

A thread diameter of 6 mm at the bone cortex closest to the fixator ensures that

minimal flexion of the screw will occur at the screw-cortex interface under normal

functional loads.

This feature, coupled with the inherent rigidity of the fixator and its axial alignment

with the bone is responsible for the excellent stability of the system. Since screw

flexion is very limited, this prevents the compressibility factor of bone (average 15.0

Kg/mm) from being exceeded at contact points between screw and bone. The

likelihood of osteolysis/osteitis occurring is thus minimised. In addition, the

technique of dynamisation stimulates bone formation at the pin sites, further

discouraging osteolysis.

4. Ease of surgeon tuition; ease of application; ease of removal

Finally, mention must be made of the ease and rapidity with which the DEF can be

applied and removed. This is particularly germane to the situation in the A c c i d e n t

and Emergency room where multiple trauma cases are regularly encountered. The

DEF is applied in minutes (average 20-30 minutes after

familiarisation with the technique) and this implies shorter periods of anaesthesia in

these severely compromised patients.

Since the screws are conical in shape they can be removed with ease as an out-

patient procedure without the need for general or local anaesthesia.

DEF



4

GENERAL OPERATIVE TECHNIQUE

NOTE : This is demonstrated in relation to the femur but applies to any long bone.

The fracture should always be approximately reduced before the fixator is applied.

The use of image intensifier is advisable.

THE PRINCIPLE: Screws are inserted into the shortest or most difficult segment first.

A broad incision in the skin is required for each screw

so that the skin around the screw is not too taut. This

shows the incision being made for the first screw. The

underlying fascia also requires broad dissection to

ensure that it is not taut around the screws, since this

would cause discomfort to the patient.

A screw guide of suitable length is inserted into the

incision using a trocar to enable the mid-line of

cortex to be located. It is important to ensure that

the screw guide is perpendicular to the longitudinal

axis of the bone.

Using gentle pressure to keep the screw guide in

contact with the cortex, withdraw the trocar, and,

using a hammer, tap the screw guide lightly to

engage its distal end in the cortex.

The correct size of drill guide is now inserted into

the screw guide for the drill to be used. Insert the

correct size drill bit, fitted with a drill stop, into the

drill guide.

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Insert the selected screw into the screw guide and

turn the self tapping screw with the T wrench.

Minimum force is required at first and when the first

cortex is engaged, the screw can be tightened with

little effort. If excessive resistance is encountered at

this stage, it is possible that the screw is not

following exactly its pre-drilled path. Under such

circumstances the screw should be withdrawn using

the T-wrench and reinserted along the correct path.

An increase in resistance is felt as the screw

penetrates the second cortex in normal cortical

bone.

When inserting screws into cancellous bone or poor

quality bone, this change in resistance is not felt and

an image intensifier should be used in these

circumstances to verify that the second cortex has

been penetrated.


Ensure that the drill completely penetrates the

second cortex. Remove the drill bit and drill guide

keeping pressure on the screw guide handle.


Drill through the first cortex up to the second

cortex, making sure that the drill is at right angles

to the bone. A power drill may be used at speeds

not exceeding 500-600 r.p.m. Excessive drill

speeds should not be used, to avoid overheating

the bone, since this may result in local necrosis

and an increased risk of osteolysis.


The Dynamic External Fixator is then attached in

place of the template assembly. The surgeon should

ensure that the central locking out is seated opposite

the bone and that the Allen wrench fitting points (in

the cams) face upwards. Positions the fixator at least

1 cm from the skin to allow for post-operative swelling

and for cleaning. It is essential to fit the body parallel to the major axis of the segment

being treated, so that the forces which occur during dynamisation are equally

distributed over the entire circumference of the bone segment. Tighten the clamp

screws first, using the Allen wrench. Each clamp screw should be tightened a little at a

time until is well seated, and finafly firmly locked. If the two outside holes of the clamp

have not been used it is good practice to place a dummy screw in the vacant outer

clamp hole. This prevents abnormal stressed when locking the clamp screws.


Leave the screw guide in position and apply one

end of the template to it. Using the grooves on

the template clamp as a reference point, make

the second incision. If possible, fit the screws into

the grooves furthest apart. Repeat the screw

insertion procedure.

Normally only 2 screws per clamp are required. In

poor quality bone, overweight patients,

particularly unstable fractures, and/or if the

fixator is more than 6 cm from the nearest cortex,

3 screws per clamp are recommended.

Before placement of the screws in the second bone

fragment following the steps as above, the template

body must be adjusted to the correct length. Make

sure it is neither completely closed nor fully open.

This will allow for final reduction and dynamic axial

compression.

Attempt to maintain the initial reduction whilst

applying the remaining screws. Remove the template

and screw guides.



Final fracture reduction is achieved using

manipulation forceps, attached to the two clamps. In

this way, manipulation force and control are facilitated

while keeping the surgeon's hands clear of X-ray

exposure during the reduction procedure. A theatre

assistant must assist in locking first the ball joints and

then the central body locking nut once a reduction

that respects the loading axis has been achieved.

Compression and distraction can be achieved by

placing the compressor/distractor unit into the cam

recesses, using the Allen wrench and with the body

locking screw loose. (360° clockwise = 1 mm.

compression and 360° anticlockwise = 1 mm.

distraction). Compression is NEVER recommended in

a fresh fracture. This completes application of the

Dynamic External Fixator.

With the fixator in place, the associated joints are

flexed and extended under anaesthesia to release

muscle and fascia tension and thereby ensure a full

range of associated joint movement. If skin tension

around the pins is observed, this should be released

by extending the skin incision until tension is

released.


POST-OPERATIVE MANAGEMENT

GENERAL MEASURES

1. Joint Function

Joint function should be checked regularly

while the fixator is in place.

2. Fracture Reduction

If the fracture has not been reduced

correctly at the time of operation, the

required axial corrections can be made in

the immediate post-operative period. If the

patient's condition permits, this can usually

be achieved without the need for general

anaesthetic, using the manipulation forceps

to reposition the bone segments.

If the patient's condition would not allow

such correction to be made immediately

after the operation, it is acceptable to wait 2-

3 weeks until a partial bony bridge has

formed between the segments. The plastic

callus can then be manipulated to achieve

the desired reduction.

3. Pin Care

The skin around the screws should be

treated on the day following application of

the Dynamic Axial Fixator and thereafter

every one to two days. The skin is first

cleaned with either ether or saline, and then

treated with any non basic disinfectant such

as a quatemary ammonium disinfectant or a

mercuric derivative e.g. mercurochrome.

The skin around the screws should then be

POSSIBLE COMPLICATION AND THEIR

SOLUTION

Should a degree of joint stiftness appear, this

can usually be overcome by a regular

programme of physiotherapy. In exceptional

cases it may be necessary to achieve

mobility through manipulation under

anaesthesia. In femoral applications, 50°-

60° of articular restriction is permitted since

a full range of mobility is normally regained

3-4 weeks after fixator removal.

If union is allowed to occur in the presence

of malalignment at the fracture site (which

should never occur if appropriate control is

exercised), further corrective surgery may

be required.

There may be some loss of serum especially

in overweight patients, and with femoral

screws.

This should not be mistaken for infection and

is not a true complication. It may be the

result of excessive patient mobility and

subsequent irritation of the tissues around

the screws.

Normal care on pin cleaning is required.



Where inflammation is seen and exudation is

more abundant, it is recommended that the

pin track be injected with an appropriate

antibiotic for 7-10 days.

Where exudation is clearly infective in origin

with the skin around the screw reddish and

warm, antibiotics should be applied locally

for 7-10 days, moistening the gauze around

the screws with antibiotic solution. Systemic

antibiotic therapy should also be

administered.

Should local conditions not improve, the

patient should return to hospital for more

aggressive therapy, including possible

removal of the screw of screws involved.

If X-rays taken in the pre-dynamisation

phase show signs of osteolysis around the

screws, it is advisable to change the site of

the screw using any other slot in the fixator

clamp.

Special care should be taken when

repositioning a screw since osteolysis

usually implies that the procedure for screw

insertion (see above, B1 -12) has not been

strictly adhered to.

It osteolysis occurs in the EARLY

dynamisation phase, it may be necessary to

remove frame and screws and apply a

functional brace.

If osteolysis occurs in the LATE dynamisation

phase, it is usually possible to leave the

entire assembly in place until final healing is

achieved, provided the situation is regularly

reviewed.

covered with sterile gauze.

Some surgeons prefer simple cleaning and a

shower with no further care, or just sterile

gauze around the screws thus not

interfering with natural crust formation.

4. Weightbearing

The degree of weightbearing applied will be

dependent upon a number of variables e.g.:

the type of fracture, the type of ORTHOFIX

frame used, bone/fixator distance, total

weight of the patient, the extent of fracture

repair, the physical condition of the patient,

the presence or absence of multiple trauma

in the same, or other limbs, the pain

threshold, and the emotional state of the

patient.

N.B. For the alleviation of pain, non-steroidal

antiinflamatory agents should be avoided

GENERAL MEASURES POSSIBLE COMPLICATION AND

THEIR SOLUTION


and simple analgesics e.g. paracetamol,

given if required.

5. Dynamisation

The time point at which dynamisation

should commence will depend upon the

factors listed under point 4 above. To

commence dynamisation, the central

locking nut is released (loosened). Fracture

site compression is then tested manually.

The ideal indication for commencement of

dynamisation is movement of 1-2 mm of the

fracture site. The gap in the body of the

fixator is measured, after which the patient

ambulates with partial weightbearing for a

few minutes. The gap measurement is then

repeated.

10

If the fixator has been applied with the

telescope fully closed, dynamisation will

NOT be possible. Under such circumstances

it may be possible to replace the fixator body

with a shorter model. This can be performed

as an out-patient procedure by fitting

another fixator outside the first to keep the

bone segments in position, while removing

the original fixator and replacing it with the

shorter model.

If there is insufficient space on the non-

threaded part of the screw outside the

original fixator for application of the

temporary fixator, the former may be moved

outwards by sliding it on the screws to create

the required space for the application of the

shorter model between the skin and the

repositioned original fixator.

If the original fixator was itself a short body

model, and the inner slots of the two clamps

are engaged, repositioning of one screw is

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THEIR SOLUTION


6. An Outline Programme for Fracture

Management

The following should be considered as a very

basic and flexible guide to fracture

management, since the actual time points at

which weight-bearing/dynamisation will

occur will depend upon those variables

described above, as well as upon whether

the fracture is stable or unstable. As a

general rule, however, it can be stated that

dynamisation for stable fractures would

ideally occur 2-4 weeks postoperatively, and

for unstable fractures, 5-8 weeks

postoperatively.

A) Stable Fractures

With stable fractures, 30% weight-bearing

should start from day one and increase to

75% by two to three weeks after operation,

at which point dynamisation is started.

Weight-bearing is gradually increased to

100% over the next three weeks and the

device can generally be removed after a

further week of full 100% weight-bearing.

B) Unstable Fractures

For unstable fractures, 15% weight-bearing

should start from day one and increase to

75% within 40 to 60 days after the

operation, by which time there should be

radiological evidence of callus formation.


the only solution. If one of the inner slots of

the clamp is free, the position of the clamp

can be adjusted relative to the screws to

permit dynamisation.

If an adequate gap exists but axial

telescopic movement is difficult to achieve,

this may be due to excessive friction

between male and female components of

the device, where perfect parallelism

between it and the diaphyseal axis of the

bone does not exist. This may be overcome

by moving one or both clamps slightly by

sliding them on the screws until the axial

telescopic system is released and

dynamisation occurs freely.

Alternatively, it may be the result of minimal

torsion or bending of the body which may

occur when the fixator is almost fully open.

Under these circumstances the existing

fixator body may be replaced by the next

larger model where possible, i.e. standard in

place of short, long in place of standard.


THEIR SOLUTION


Dynamisation is started at this point and

weight-bearing is gradually increased to

100% over the next four weeks. The device

can generally be removed after further week

of full 100% weight-bearing.

X-ray control should be carried out when the

patient is released from hospital after the

operation, at which time fixator ball joint

locking strength should also be scheduled

every 20-30 days.

On each occasion, X-rays should be taken,

the condition of the skin around he screws

should be reviewed, clamp locking nuts

retightened, and ball joint checked. If

necessary the body of the fixator may be

briefly removed to enable un-obstructed X-

rays to be taken for evaluation of healing

progress. It is not generally recommended

that patients bathe fully while the fixator is

in place but some surgeons allow it,

provided disinfectants are used in the

washing water.

7. Fixator Removal

Once there is clinical and radiological

evidence of fracture healing, the fixator is

removed as an outpatient procedure. First

the central locking nut is tightened to

maintain the exact length of the fixator prior

to removal in case the fracture should

require a further period of fixation.

The fracture can be manipulated after

removal of the fixator to ensure that clinical

healing has been achieved. If there is any

doubt over clinical and radiological healing

and provided the screws are well-tolerated,

the fixator can remain in situ for a further

period of two weeks.


If there is evidence that fractur healing is

impaired as a result of local or general

conditions, simple static compression can be

applied to achieve better fracture site

stability. As soon as X-rays indicate an

improvement in the quality of the bony

callus dynamisation can commence /

recommence.

Falls:

Should the patient fall accidentally, clinical

and radiological evaluation should be

performed. If there is no sign of movement

at the fracture site, the tightness of the ball

joints should be checked.


THEIR SOLUTION


If, on the other hand, there is clinical

evidence of complete healing but prudence

suggests a final clinical test, the screws can

be left in situ for a further week and full

weight-bearing allowed.

The fixator may be given to the patient and if

any problem arises in relation to the

fracture, the patient can return to the

hospital or the surgeon for the device to be

refitted without the need for an operation.

If no further problems have been

encountered at the end of this one week

period, the screws can be removed without

performing an X-ray. If the surgeon is

confident that clinical and radiological

healing has been achieved, the fixator

screws can be removed immediately as a

simple out-patient procedure. The screw

entry holes are then usually treated every

two days until they close spontaneously,

which normally takes place after 7-10 days.

To ensure full follow-up documentation of

the case, an X-ray should be taken at one or

two months from final healing and removal

of the fixator.


THEIR SOLUTION



Instruments

Part No. C 511001000

Part No. C 511101000

Part No. C 510001000

Part No. C 515001000

Part No. C 514001000

Part No. Description

Template for large & medium Dynamic External Fixator

Template for Small Dynamic External Fixator

Spanner Universal Joint

Manipulating Forcep

Trocar

Screw Guide

C 512001000 8 X6X60 mm

C 512101000 8 X6X100 mm

Dynamic External Fixator

Part No. Description C 154031000 LargeC 154021000 Medium C 154011000 Small

T-End Clamp

Part No. C 175001000

Self Adjusting Clamp with medium Dynamic External Fixator

Part No. C 187001000



Drill Guide

C 513001000 6X3.2X40 mm

C 513101000 6X3.2X80mm

C 513201000 6X5X40mm

C 513301000 6X5X80mm

Part No. Description

Container for Dynamic External Fixation System

Part No. Description H 849001000 For AppliancesH 850001000 For Instruments

Container for Dynamic Ext. Fixation system - Part No.

Part No. Tray accepts the following : Qty.

C 154011000 Small Kit 1C 154021000 Medium Kit 1C 154031000 Big Kit 1C 175001000 T End Clamp 1C 184001000 Self Adjusting clamp 1

Container for Dynamic Ext. Fixation System Instruments - Part No H 850001000

Part No. Tray accepts the following : Qty. C 511001000 Template for large and medium DAFIX 1C 511101000 Template for small DAFIX 1C 515001000 Manipulating forcep 2C 514001000 Trocar 1C 512001000 Guide Screw 8 x 6 x 60 mm 6C 513001000 Drill guides 6 x 3.2 x 40 mm 6C 513101000 Drill guides 6 x 3.2 x 80 mm 6C 513201000 Drill guides 6 x 5 x 40 mm 6C 513301000 Drill guides 6 x 5 x 80 mm 6C 512101000 Guide Screw 8 x 6 x 100 mm 6

Appliances H 849001000

All Instruments are non - marked



Dynamic External Fixation System - Operative Guidelines

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