Aruna

Vade,

MD

Rochelle

Eissenstat,

#{149}

Radiographic Procedures

Features

The successful treatment of leg length discrepancy depends not only on an accurate assessment of the pattern of growth of the femur and tibia but also on thorough understanding of the various treatment methods. The radiographic features of 43 leg lengthening sumgenes were studied retrospectively, and their significance in the treatment of children with leg length discrepancies was evaluated. The morbidities seen in our study indude leg deformities resulting from misalignment of bone segments and excessive stretching of soft tissues, and fractures, nonunions, and delayed unions at the lengthened sites, leading to prolonged application of traction devices. The overall frequency of morbidity was 148.8%. In the orthopedic literature, morbidity rates vary with the underlying reasons for leg length discrepancy, the type of bone lengthening procedure, and the type of complications included. Timely detection of radiographic abnormalities in the lengthened leg can contribute significantly to the successful treatment of leg length discrepancy. Index

terms:

45.1484, 45.451

44.458 #{149} Femur,

Tibia,

Bones,

Radiology

abnormalities,

45.458 #{149} Bones, abnormalities,

abnormalities,

MD

45.1484,

44.451, 44.458

45.458

1990; 174:531-537

Lengthening

EG length

discrepancies in childmen can occur secondary to congenital skeletal dysplasias, vascular malformations, or causes such as trauma, infection, paralysis, and tumoms (1,2). With use of bone age and a straight-line graph for leg length discrepancy

44.1484,

surgery, 44.1484.

of Bone

#{149}

or the

well-established

growth-remaining method of Andemson and Green, future growth and length discrepancy can be predicted (3). The morbidity associated with leg lengthening procedures (1,4-7) allows them to be used only for discrepancies that cannot be satisfactorily corrected with other methods. Classically, bone lengthening methods have involved either one-stage or gradual lengthening (8-11). The basic principles of bone lengthening procedures are osteotomy of the short bone, application of a mechanical distraction device to the bone segments proximal and distal to the osteotomy, and one-stage or gradual distraction of the bone segments. This may be followed by plating of the bone segments on waiting for the development of a bridging bone callus before removal of the hardware. Recently, several groups of investigatons have attempted to improve existing techniques while reducing complication mates (12-14). The purpose of our study was to compare the callus distraction and Wagner methods (11) of bone lengthening and to determine whether madiologic monitoring of bone lengthening and healing was important for early detection and treatment of complications.

PATIENTS I

sity

From of

the

Department

Illinois

Medical

of Radiology, Center

at Chicago,

Univer1740

W Taylor St. Chicago, IL 60612. From the 1988 RSNA annual meeting. Received March 13, 1989; revision requested April 17; revision received August 31; accepted September 8. Ad-

dress t

reprint RSNA,

requests 1990

to A.V.

Leg

radiographs

had undergone surgeries

were

AND

for leg length

leg lengthening

evaluated

retrospectively.

ho,

congenital

discrepancies dysplasias,

included trauma,

lengthening same leg, lengthening

factors poand

os-

underwent

underwent

leg,

relengthen-

ing of a bone after complete healing. Altogether, 43 bone lengthening surgeries (21 by the Wagner method and 22 by the callus distraction method) were evaluated. Of the 22 callus distraction lengthenings, three were done with the Iiizarov

technique.

Callus

distraction

a method of lengthening bone grafting (ii). After early callus is elongated sive axial distraction.

Wagner

Method

(callotasis)

is

a bone without osteotomy the by slow, progres-

(Fig

1)

Stage 1.-After open middiaphyseal osteotomy of the short bone, with initial diastasis of 0.5-1 cm, external pins are applied for distraction of the bone segments. The osteotomy gap is stretched at a distraction rate of 1.5-2 mm/d for several weeks. Stage 2.-External traction pins are removed, and a side plate and screws are applied to the osteotomy segments. In the

second

operation,

iliac crest

cancellous

bone is grafted into the diastasis. Weight bearing is not permitted for a long period to allow the graft to incorporate. Stage 3.-The side plate and screws are

removed

after

occurred

at the

osteotomy

from

months

may

take

mature

bone

bridging gap,

which

to more

than

has a

year. After removal of the hardware, gradual weight bearing is permitted. Callus

Distraction

Method

(Fig

2)

Stage 1.-After open osteotomy at the diaphysis of the short bone, external pins for distraction of the bone segments are

The distracted to the original When

on radiographs

ranged

Six patients

of two long bones in the two patients underwent of one long bone in each

and five patients

teotomy.

who

gradual

Patient ages at the time of surgery from 9 to 161/2 years. The causative

and 19 femurs.

applied. turned

METHODS

of 30 children

teomyelitis. Length discrepancies at the time of surgery ranged from 2.8 to 8 cm. Bone lengthening was done in 24 tibias

callus

after

segments are reposition after osformation

7 days,

is seen

the oste-

otomy gap is stretched with a distraction rate of 0.25 mm four times a day. New callus is generated with each lengthening. A monolateral axial traction device (matching that used in the Wagner method) is 531

b.

a.

Figure

1. leg length

Wagner

method.

used

as an external matures.

Full

fixator weight

while

the cal-

bearing

is per-

mitted during the distraction stage. Stage 2.-External traction pins are memoved after bridging of mature bone has occurred at the osteotorny gap, which is usually by 6 months. The average lengthening index (the time bridging) is 1 mo/cm.

The callotasis

I!izarov method

for

technique of bone

mature

makes

bone

use of the

lengthening.

However, the peniosteum and hence the medullary circulation are kept intact by closed corticotomy, and distraction of callus is done by a circular vides three-dimensional

bone

that of

segments.

Antenoposterior

532

fixator control

.

Radiology

and

lateral

radio-

prothe

d.

C.

Radiographs

of 4 cm. The osteotomy gap gap of 3 cm was filled with bone graft material bridging at the osteotomy gap is evident (d).

tomy bone

lus

Right tibia, discrepancy

from 1 i ‘/2-year-old boy with congenital hypoplasia was stretched for 4 weeks (a, b). At the time of plating (c).

A 5#{176} medial

bowing

of the

tibia

(b)

graphs of the lengthened bone, including the proximal and distal joints, were obtamed at 2-3-week intervals from the time of osteotomy to the removal and irregularly

follow-up

period

to 2 years. All with particular

ranged radiographs attention

time of hardware thereafter. The

from

3 months

were

viewed to (a) alignment

of bone segments; (b) length of the osteotomy gap; (c) initial appearance and hater maturity of the callus; (d) bending or breaking of metallic hardware; (e) radiolucency around pins; (f) cehlulitis or softtissue site;

necrosis (g) adajcent

adjacent joint

to the lengthened subluxations, disho-

cations, or contracture deformities; (h) fractures at the lengthened site in the bone segments.

and and/or

was

corrected

of the right lower extremity and a of the bone segments, the osteoat the time of plating (c). Excellent

RESULTS of major and miseen with the two methods of bone lengthening are tabulated in Tables 1 and 2. Minor complications were those that were treated and resolved during the lengthening period, and major cornplications were those that led to limb deformity, premature termination of lengthening procedure, nonunion, late fractures, replacement of mechanical traction devices, or repeat osteotomies. The radiographic complications nor

The frequencies complications

February

1990

Figure

2.

of 6.5 cm. time there

Left tibia,

two-stage

The osteotomy was good bone

callotasis

gap was bridging.

procedure.

stretched

for

Radiographs

3 months

from

(a, b, c), and

1 1 V2-year-old the

external

boy with traction

history

device

of polio

was

sion

a leg length

after

deformities

(ii)

distal head (n strength

and

and

removed

genu

of the

migration = 1), (iii) leading

valgum

deformity (n necrosis (n complications

matic

(d),

ankle

of the

at which

(n fibular

decreased to hip

and

1),

=

muscle subluxations

knee

flexion

6), and (iv) soft-tissue 1); and (e) long-term such as stress or tnau-

fractures

(Fig7)(n

discrepancy

6 months

at the

lengthened

site

2).

DISCUSSION Leg performed

lengthening when

years of age and tic, bone healing childhood,

the

surgery the

is ideally

patient

soft tissues is as good patient’s

is 15-16

are elasas that in

motivation

better than that in childhood, the remaining growth potential that

were

encountered

in our

series

of 43 bone lengthening procedures were also grouped as follows: (a) those related to alignment and sition

of segments related

25); (b) those maturity

of

callus

174

across

Number

#{149}

po-

(Figs lb. ic, 3) (n to extent and the

oste-

otomy gap: (i) immature callus ing (n = 7), (ii) delayed union (77 = 7), (iii)stress fractures (n

Volume

and (iv) early callus formation

2

bnidg(Fig 4) 7),

(Fig

5) and excessive (n 3); (c) those

me-

hated to fixation devices: (i) mechanical failure or fatigue of fixation device leading to fracture, bending, or dislodgment of pins (Fig 6) (n = 4) and (ii) loosening or infection at pin sites (n = 6); (d) those related to overstretching of muscles, vessels, on nerves: (i) tahipes equinus and even-

negligible crepancy be 7 cm

(ii). If the leg length at maturity is anticipated on less, corrective surgery

is

and is disto

can be done as one operative lengthening procedure. If the length discrepancy at maturity is anticipated to be 7-12 cm or over 12 cm, two on three lengthening procedures may be necessary, and the first surgery is performed when the patient is either 12 on 8 years old, respectively (ii).

Radiology

#{149} 533

Careful required

serial radiohogic to ascertain the

studies are length of

the osteotomy gap, alignment of the bone segments, maturity and extent of callus formation, and bone bridging at the osteotomy gap. Radiographs obtained immediately after osteotomy show the site of osteotomy and location of the external traction pins, the proximal

which are inserted into and distal bone seg-

ments. In rare instances, bone may fortuitously result

of trauma,

the short fracture as the

obviating

the

oste-

otomy. Bone lengthening can be achieved at the site of fracture by placement of traction devices on the segments. Angulation deformity of the short bone can also be corrected at the time of lengthening. Problems can be anticipated if the pins or osteotomy are noted to be angled mathem than orthogonal with respect to the longitudinal axis of the bone on both the antemoposteriom and true lateral radiognaphs. During the second stage, when extemnal traction is applied to pull apart the bone segments, carefully posi-

tioned antemopostenior and lateral views of the lengthening bone must be obtained each time the device is adjusted and whenever clinical signs or symptoms appear. The length of the gap must be measured, and angulam misahignments

and

position

dis-

placements must be assessed. If misalignment or displacement of the bone segments is detected early, connection can be achieved during furthem lengthening (Fig 3) or plating. The Ihizarov technique uses the circulam fixaton device, which is versatile and allows circumferential thmee-dimensional deformities adequately

a.

b.

Figure

development

callus, teotomy

be evaluated. bone callus continuous.

Later,

en bone and the

converts trabecular

dent

plain

the

on

trabeculam

sumes

a still

this

radiographs.

bone more

in the mature

Radiology

#{149}

method.

Radiographs

tibial

fragment

of Bone Lengthening

deformities

device callus

Callotasis with Monolateral Axial Traction (a 19)

Ca!!otasis with Ilizarov Technique (a 2(67)

1(5)

3(16)

0(0)

0(0) 1 (5)

3(16) 1 (5)

0(0) 1 (33)

2 (10)

1 (5)

0(0)

3 (14)

1 (5)

0(0)

0 (0) 1 (5)

1 (5) 0 (0)

0(0) 0(0)

10 (48)

26 (137)

3)

pin leading

de-

failure

Note-Percentages

bone, is evi-

Method

due

Soft-tissue necrosis Total no. of complications

wov-

Procedures

device

to mechanical

shreds of and dis-

Oilier disfurther

leading

Joint deformities to soft-tissue contractures

vice

with during

16 (84)

Fractures Nonunion at osteotomy gap

Persistent

1 i-year-old girl partially corrected

was

2 (10)

failure to mechanical failure

from (a)

with Monolateral Axial Traction (n = 21)

Mechanical Premature

the osmust

3 (100)

in parentheses.

Finally,

gap

as-

appear-

ance, differentiating into cortex and meduhlary space, continuous with the bone above and below the gap. 534

of distal

Angulation

osteolysis

primary

to trabecular structure

angulation (b).

Complication

of mineralized

Initially, the are amorphous

Wagner

Wagner

With monowith both the techniques-

its extent in bridging gap, and its maturity

tibia,

Table 2 Major Complications

misalignments of bone segments are much more difficult to correct and notational changes almost impossible to connect.

The

Right

ease. Lateral distraction

control, so that angulation can be opportunely and corrected, decreasing the

frequency of malunions. lateral fixators-used Wagner and callotasis

3.

Animal

experiments

callotasis

and for

methods

biochemical bone

healing

have

provide

conditions (7).

New

shown

that

biologic

favorable bone

for-

mation

is better

under

controlled

progressive mechanical distraction, which is provided by callotasis with 0.25

mm

of distraction

four

times

February

a 1990

5a.

4-

4, 5. (4) Right femur, callotasis procedure. Radiograph tooth nadiolucency (arrow) at the center of the callus 9 months layed union. (5) Right tibia, callotasis procedure. Radiographs ca!lotasis. Fifteen days after the osteotomy, excessive anterior (a). The proximal pins were replaced, but rapid callus formation could not be achieved without increasing the deformity. The much as was desired.

day

versus

2 mm

day.

That

preservation

mow

optimizes

of distraction of

once bone

distraction

a

mar-

is disputed

by some

authors (7,13). DeBastiani et al showed that if the Wagner monolateral fixatom is used with the biohogic principles incorporated by Iiizamov, better results could be obtamed without the need for bone grafting (13). During

the

traction

stage,

sive bone bridging occurs teotomy gap. One should inspect the gap to determine the

developing

pears

trabeculam

continuous

and

longitudinal

lines

maturation fracture site.

of

A sawtoothlike may

center

represent

bone

union

or a stress

4,

In

evaluation

Volume

aligned stress.

our

zone

either

delayed

fracture of

differentiation

was

174

2

Number

#{149}

may

callus,

seven

difficult

fractures

union.

In

tion

from

either of

delayed

event,

continued

device

as

til complete our patients had buckling level during another two at that site. Premature mation

with

of the

stress

an

Comeradiobone

treatment use

external

the

trac-

fixatom

un-

of

healing occurs. Two of with sawtooth hucencies fractures of bone at that the traction stage, and patients had nonunion

on excessive callus forbe a problem because greater force must be applied to increase the gap. Greaten stress may lead to bending on breaking of the pins or misalignment of the bone

ap-

If callus

lucent

at the

which 7).

bone

does not proceed, a stress may occur at this weaker

develop

cases,

pmogres-

at the oscarefully whether

from 9-year-old girl with polio who underwent callotasis and showed a sawafter osteotomy. This healed in another 4 months and probably represents defrom 12-year-old girl with congenital shortening of the tibia who underwent angu!ation at the osteotomy site due to premature callus formation was seen caused a valgus deformity at the osteotomy site (b); further lengthening tibia healed with the deformity present (C) and could not be lengthened as

the basis of radiogmaphs alone. lation with pain and follow-up graphs is needed to differentiate

consists

5c.

5b.

Figures

(Figs such

on

segments,

can

also

as

was

seen

in

three

of

our

patients who underwent calhotasis. Further lengthening may not be possible without a repeat osteotomy (Fig 6). Acute fractures above or below the ends of the plate may occur dun-

callus bridging and lead to delay in removal of hardware, as happened in one of our patients. The bone segments must be carefully observed, particularly at the pin insertion sites, for signs of mechanical loosening or infection because either of these could lead to misalignment of the pins or fracture at the pin site, which may end the procedure. In one paing

tient

the

mechanical

months

after

to be placed ing.

After removed

fixatom

surgery

and

in a cast

for

fell the

off 4

leg

further

had

heal-

the traction device has (stage 3 of the Wagner

been

method or stage 2 of the cahlotasis method), the immediate postopenative radiogmaphs can show whether any

at the

fracture

on

pin

tracks.

infection

has

If the

mature

at the

moval, sequent

there is more chance deformity to occur.

patients

who

time

had

occurred

callus

is im-

of hardware

immature

mefor subOf seven callus

Radiology

at

.

535

I