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These concerns are particularly germane in the lower extremity, in which the altered distri-bution of weight-bearing stresses leads to abnormal force concentrations across joints.1Furthe

Evaluation and Surgical Correction

Robert A Probe, MD

Abstract

After diaphyseal fracture healing, the

morphology of an involved bone is

rarely left unaffected, and some

alter-ation in length, rotalter-ation, angulalter-ation,

and translation is expected With

mod-ern fracture care, such deviations from

the original shape are generally small

in magnitude and well tolerated by

patients However, on rare occasions,

the change in bone morphology is

suf-ficient to cause concern Functional

im-pairment, cosmetic deformity, and the

long-term effect of malalignment on

joint integrity and stability are the most

important problems These concerns

are particularly germane in the lower

extremity, in which the altered

distri-bution of weight-bearing stresses leads

to abnormal force concentrations across

joints.1Furthermore, tilting of the knee

and ankle joint surfaces can lead to

detrimental shear stress within

artic-ular cartilage, as well as to changes

in joint contact area.2,3When these

con-ditions require management, an

os-teotomy must be designed to restore

normal alignment, length, and

hori-zontal joint line orientation It is crit-ical for the treating physician to fully assess and characterize these angu-lar malunions The physician also should understand the implications for the joint, the indications for an os-teotomy, and preoperative osteotomy planning

Normal Biomechanics of the Lower Extremity

To understand the pathomechanics of malunion, the surgeon first must have

a thorough knowledge of normal lower extremity mechanics Although differing methodologies of measure-ment and ethnic variation cause some discrepancies in reported values, a few generalizations are appropri-ate.4-7

The mechanical axis of the lower extremity passes from the femoral head through the calcaneal tuberos-ity Because of the variable position-ing of the tuberosity and the

difficul-ty in radiographic evaluation, this is most commonly approximated by us-ing the center of the femoral head and center of the ankle as the outermost points of a line defining the mechan-ical axis Using these two points as references, the average mechanical axis crosses the knee 10 mm medial

to its frontal plane center (Fig 1, A) Radiographically, this is

approximat-ed by the position of the mapproximat-edial tib-ial spine In the sagittal plane, the me-chanical axis from the center of the femoral head to the center of the an-kle lies just anterior to the center of rotation of the knee joint (Fig 1, B) Functionally, this anterior position of the mechanical axis is desirable be-cause it allows for passive locking of the knee in full extension

The mechanical axis of the tibia di-rectly coincides with the anatomic axis; however, because of the medial

Dr Probe is Chairman, Department of Ortho-paedics, Scott & White Memorial Hospital, Scott, Sherwood and Brindley Foundation, and Associ-ate Professor, The Texas A&M University Sys-tem Health Science Center, College of Medicine, Temple, TX.

Neither Dr Probe nor the department with which

he is affiliated has received anything of value from

or owns stock in a commercial company or insti-tution related directly or indirectly to the subject

of this article.

Reprint requests: Dr Probe, 2401 S 31st Street, Temple, TX 76508.

Copyright 2003 by the American Academy of Orthopaedic Surgeons.

The lower extremity has a mechanical axis with joint orientation that allows joint

longevity and efficiency in bipedal gait When normal alignment is lost because of

trauma or other conditions, deviations from this anatomic norm may be deleterious

to long-term joint function In fractures that have healed with angular malunion,

all facets of the deformity must be carefully considered, including alteration in length,

rotation, alignment, and translation Once all elements are fully defined, the effects

of the malunion on mechanical axis and joint orientation can be understood

Tech-niques for surgical correction include wedge, dome, and oblique osteotomies and

dis-traction osteogenesis Each method possesses characteristics appropriate for certain

clinical situations Judicious patient selection and thoughtful preoperative planning

may allow restoration of normal mechanics.

J Am Acad Orthop Surg 2003;11:302-311

position of the femoral head relative

to the shaft, there is a difference

be-tween the mechanical and anatomic

axes of the femur The femoral

me-chanical axis is the line from the

cen-ter of the femoral head to the cencen-ter

of the knee; the anatomic axis is the

line from the piriformis fossa to the

center of the knee In an individual

of average size, the anatomic axis is

in 6° of valgus compared with the

me-chanical axis This angle may be

in-creased in shorter femurs and

de-creased in longer femurs, making

comparison with the contralateral

side beneficial

Joint Orientation

The frontal plane orientation of the joints also should be defined The neck-shaft angle commonly has been used for the hip and proximal femur; however, this value is depen-dent on landmarks that change ra-diographically with different de-grees of hip rotation An alternative method, described by Chao et al,4is the proximal femoral orientation an-gle This angle is formed by the di-vergence of a line from the tip of the greater trochanter to the center of the femoral head and the femoral mechanical axis Although individ-ual variation may be present, 90°

(parallel to the floor) is a reasonable estimate in the absence of compara-tive contralateral films (Fig 2) In stance, the knee joint line is oriented

in 3° of valgus relative to the me-chanical axis As a result, the distal femoral articular surface is in slight valgus relative to the femoral me-chanical axis, and the proximal tibial articular surface is in slight varus relative to its mechanical axis This knee valgus is valuable because, during gait, the limb assumes a 3°

varus position as the foot is planted beneath the body’s center of gravity

The medial inclination of the limb makes the knee axis parallel to the floor during weight bearing The orientation of the ankle joint is usu-ally perpendicular to the mechanical axis.4Individual patients may dem-onstrate deviation from these popu-lation averages and, when available, the joint inclination of a normal op-posite side provides valuable com-parative information

Patient Evaluation

Deformity Assessment

Accurate malunion surgery begins with precise definition of the defor-mity Implications of a corrective os-teotomy cannot be known unless the malunion is precisely characterized

three-dimensionally Leg-length dis-crepancy can be estimated with cal-ibrated blocks leveling the anterior superior iliac spines to palpation The relative contribution of the tibia to the length discrepancy can be estimated with the patient prone and the knees flexed 90° In this position, the dis-crepancy in sole height usually can

be attributed to the tibia, with the re-mainder of the discrepancy

account-ed for by the femur Increasaccount-ed preci-sion can be obtained with leg-length radiographs on a ruler or with com-puted tomography.8Overall limb ro-tational differences can be estimated

by comparing maximal internal and external rotation of the lower limbs The tibial component can be

ascer-Figure 1 A,The frontal plane mechanical

axis (dashed line) of the lower extremity

ex-tends from the center of the femoral head,

across the medial tibial spine, to the center

of the ankle B, The sagittal plane

mechani-cal axis (dashed line) extends from the

ter of the femoral head, anterior to the

cen-ter of rotation of the knee, to the cencen-ter of the

ankle.

Figure 2 Frontal plane orientation of the lower extremity joints The center of the fem-oral head to the tip of the trochanter line should be parallel to the floor The knee is in 3° of valgus, and the ankle typically is ori-ented parallel to the floor.

tained by having the patient sit with

the knees flexed 90° and the ankles

at neutral In this position, the

differ-ence in the projection of the foot will

describe the rotational difference

within the tibias Obtaining a

comput-ed tomography scan through the

fem-oral neck, supracondylar femur, and

distal tibia and comparing the

rota-tional position of the two extremities

gives a very accurate measurement of

rotational deformity.9

Angular deformity is usually

es-timated by superimposing

intersect-ing lines centered in the medullary

ca-nal of the proximal and distal

fragments on both anteroposterior

(AP) and lateral radiographs

How-ever, this technique is subject to

er-ror if a short metaphyseal segment is

present because it can be difficult to

accurately determine the axis

Phys-iologic bowing of the femur or the

tib-ia also can make drawing accurate

lines along the medullary canal

dif-ficult Milner10reviewed a series of

malunited tibial fractures and found

an error range of 11.7° (from−6.2° to

5.5°) in the coronal plane when

rely-ing on the medullary canal as an axis

reference Increased accuracy may be

achieved by using a reversed

radio-graph of the contralateral side as a

template The mechanical axis may be

drawn on the uninjured side,

fol-lowed by superimposition of the side

with the deformity on which the

proximal and distal mechanical axes

have been drawn Divergence of the

proximal and distal mechanical axes

indicates true angular deformity

The point of intersection of the

proximal and distal axes has been

called the center of rotation of

angu-lation.11In cases of pure angulation,

this intersection occurs at the apex of

the deformity In cases of angulation

with translation, the center of rotation

of angulation is moved away from the

site of maximal angular deformity, at

a distance proportional to the amount

of translation (Fig 3)

One advantage of this method of

biplanar radiographic assessment is

its simplicity: sagittal and frontal plane deformity can be estimated with any set of standard radiographs

A second advantage is that the effects

of the malunion on both the frontal and sagittal plane mechanical axes can be estimated The principal dis-advantage is that this method rarely defines the true magnitude and ori-entation of the angular deformity.12

If angulation is seen on both AP and lateral radiographs, the true magni-tude of angulation will be greater than that seen on either view, and the plane of deformity usually is some-where in between With the

deformi-ty measured on AP and lateral radio-graphs, trigonometric calculations can help define the true plane and po-sition of the deformity, according to the following formula:12

Orientation angle from frontal plane = arc tan

tan (lateral) tan (anteroposterior) True magnitude = arc tan

√tan2(lateral) + tan2(anteroposterior) Alternatively, the plane and mag-nitude of the deformity may be de-fined on fluoroscopic examination All extremities with angular

deformi-ty may be rotated into a plane in which no angular deformity is seen

on fluoroscopy Orthogonal to this plane is the plane of maximal angu-lar deformity Quantitative assess-ment of the deformity can be obtained from the radiographs in this projec-tion

Once the magnitude of the defor-mity is defined, its effects on joint me-chanics must be assessed This is a function of the magnitude and direc-tion of the angular deformity as well

as its location within the leg For ex-ample, a 20° valgus deformity in the subtrochanteric region of the femur will result mainly in leg lengthening, but a 20° valgus deformity of the su-pracondylar region will result in shortening and substantial lateral translation of the mechanical axis Computer-modeled effects on length, mechanical axis, and joint ori-entation of various 20° malunions are listed in Table 1 The variability in me-chanical consequences of these malunions underscores the necessity

of considering both the magnitude and location of the malunion In gen-eral, as the deformity approaches the knee, the mechanical axis is

translat-ed mtranslat-edially for a varus deformity and laterally for a valgus deformity An-gular malunions around the knee also have the greatest effect on leg length

As the deformity approaches the hip

or ankle, effects on the mechanical axis are diminished; however, the ad-jacent joint becomes increasingly malaligned

Figure 3 In cases of combined translation and angulation, the center of rotation of angulation (dark dot) may be defined such that rotation centered on this point will correct both deformities This point is defined

by the intersection of the mechanical axes of the proximal and distal segments (dashed lines).

Mathematical formulas and

nomo-grams have been developed to assist

in the understanding of the

mechan-ical effects of particular malunions.13,14

Puno et al13described trigonometric

methods of calculating these effects;

however, because many physicians are

not familiar with this methodology,

it is more common for the

mechan-ical axis and joint orientation to be

measured radiographically These

measurements should be taken on a

full-length radiograph from a 51-in

cassette, covering the hip to the

an-kle The beam should be centered on

the knee, with the patella pointing

di-rectly forward and the x-ray tube 10

feet away The line from the femoral

head to the center of the ankle defines

the mechanical axis A perpendicular

line from the mechanical axis to the

medial tibial spine defines the moment

arm of axis deviation Malalignment

of the knee may be estimated from this

long leg radiograph; however,

dedi-cated AP views of the hip and ankle

are preferred for measurement of their

respective orientation because of the

parallax error on long leg radiographs

Limb axis translation also has an

effect on mechanical axis shift as well

as joint orientation Angulation and

translation have been shown to be

in-dependent of each other, with the

di-rection and magnitude of the two de-formities unrelated.12The composite effects of these two variables are best discerned by review of long leg, weight-bearing radiographs

Symptom Assessment

Other important considerations in patient evaluation include the status

of local muscle strength, ligamentous stability, cartilage integrity, and range

of motion of the joints of the affected extremity Mild medial mechanical axis displacement (varus) may be poorly tolerated with incompetent lateral ligaments of the knee.15 Sim-ilarly, if the medial chondral surface

of the knee has been damaged, me-dial axis deviation is likely to exac-erbate arthritic symptoms Ankle malalignment may be well tolerated

in the setting of a supple subtalar joint, but a foot with a stiff subtalar joint will be intolerant to minor de-grees of ankle malalignment.3

Final-ly, a well-developed quadriceps mus-cle may compensate for posterior displacement of the sagittal plane me-chanical axis; however, a patient with

a weak muscle likely would experi-ence symptomatic buckling of the knee

Symptoms attributable to mal-union may be apparent immediately

after fracture healing or may mani-fest over a longer period of time Short-term consequences are infrequent and usually arise when a malunion is se-vere enough to exceed the compen-satory limits of adjacent joints For ex-ample, a procurvatum deformity of the distal femur, which places the sag-ittal plane mechanical axis posterior

to the knee and thus prevents lock-ing of the knee durlock-ing the stance phase

of gait, could be expected to be symp-tomatic immediately Likewise, a patient with a varus distal tibial malunion that exceeds the compen-satory valgus effect that can be ob-tained through the subtalar joint would experience disruption of gait mechanics and noticeable symptoms

Chronic Effects of Malunions

Delayed-onset symptoms caused by altered mechanical forces on the joints are more common than immediate symptoms Although a direct causal relationship between joint deteriora-tion and altered mechanical loads re-sulting from malunion has not been established, an increasing number of animal, cadaveric, and clinical stud-ies support this hypothesis In a rab-bit model in which 30° angular malunions were created in the prox-imal tibia, Wu et al16observed histo-logic changes in both cartilage and bone on the overloaded condyle over

a 34-week period The cartilage dem-onstrated irregularity and loss of the superficial horizontal layer, as well as clefts extending into the transition zone The subchondral bone showed increased thickness and decreased porosity The location of chondral changes showed direct correlation with changes in the subchondral plate, suggesting that increased sub-chondral plate stiffness may play a causative role in the overlying carti-lage changes

Simulated malunions of varying degrees and directions in human

ca-Table 1

Mechanical Implications of Various 20° Frontal Plane Malunions*

Malunion

Length Change

Mechanical Axis Change

Knee Orientation

Ankle Orientation 20° subtrochanteric

valgus

+11 mm 14 mm

lateral

2° valgus 2° valgus 20° subtrochanteric

medial

2° varus 2° varus 20° supracondylar

varus

−11 mm 64 mm

medial

10° varus 10° varus 20° proximal tibia

medial

8° valgus 12° varus 20° distal tibia

varus

−4 mm 12 mm

medial

1° valgus 19° varus

* Malunion consequences derived with computer modeling software

(LightwaveMod-eler; Newtek, San Antonio, TX) Leg length changes reflect the absolute distance from

the top of the femoral head to the ankle and not actual bone segment lengthening.

davers have been used to

demon-strate changes in contact pressures

within the joint.1-3 McKellop et al1

used pressure-sensitive film to

dem-onstrate doubling of contact pressure

across the knee with simulated 20°

malunions in both varus and valgus

directions Tarr et al2demonstrated

that simulated malunions in the

dis-tal third of the tibia could alter the

shape and diminish the size of

tibio-talar contact In subsequent

experi-mental work, Ting et al3

demonstrat-ed that simulatdemonstrat-ed subtalar stiffness

potentiated these mechanical

alter-ations The conclusions of these

stud-ies are that simulated malunions

ap-pear to alter contact pressure within

adjacent joints and that these

chang-es are maximized as the deformity is

placed closer to the joint

The finding that may be

extrapo-lated from these animal and

cadav-eric data is that the presence of an

al-tered mechanical environment within

the joint places the joint at increased

risk for degenerative arthropathy

Puno et al17reviewed 27 patients with

28 tibial shaft fractures a mean of 8.2

years after injury They measured

ar-ticular malalignment rather than just

the degree of malunion This

distinc-tion is important because it takes into

consideration both the magnitude and

location of the malalignment

Regres-sion analysis showed that the

great-er the ankle malalignment, the

poor-er the ankle function scores The knee

did not show similar results;

howev-er, mean malalignment in the knee was

only 1.3° compared with 6.6° in the

ankle Kyro et al18compared the

func-tion of 17 patients with tibial malunion

to that of 47 patients without malunion

and found significantly (P < 0.05) more

subjective complaints and

function-al limitations in patients with

angu-lation >5° In another series of 14

pa-tients with malaligned tibial or femoral

fractures followed up at a mean of 31.7

years, there was progressive knee

de-formity thought to be directly

relat-ed to a combination of the calculatrelat-ed

increased angular force on the tibial

plateau and time from original

inju-ry.19This seems to document the det-rimental effects of altered mechanical axis on long-term joint function van der Schoot et al20reviewed 88 patients

at a mean follow-up of 15 years after tibial fracture They found a

statisti-cally significant (P < 0.001)

relation-ship between tibial malalignment and degenerative changes in the knee and ankle

Not all of the literature supports this thesis of long-term detrimental effect Merchant and Dietz21reviewed

37 patients after tibial shaft fracture

at a mean follow-up of 29 years In patients with >5° varus,

radiograph-ic arthrosis was noted in the ankles;

however, there was no correlation with the degree of malunion and knee or ankle function scores Milner et al22 reviewed 164 patients at a minimum

of 30 years after treatment of tibial shaft fracture They found increased subtalar stiffness associated with an-gular malunion but no statistically sig-nificant association of malunion with ankle or knee arthritis This study is valuable because it confirms that mi-nor degrees of malunion are

tolerat-ed at the knee and ankle; however, ex-panding these conclusions to more severe deformities is not warranted because only 4% of patients had healed with coronal plane malunion≥10° Be-cause of these conflicting reports, as-cribing long-term functional deficit to malunion remains controversial, es-pecially because the effect of the orig-inal extremity trauma on the joint sur-face cannot be accurately determined.23

Surgical Indications

Common indications for malunion correction include ligamentous insta-bility on the convex side of the de-formity,15leg-length discrepancy >2

cm, inability to place the foot in a plan-tigrade position, and unicondylar ar-thritis of the knee However, the symp-toms caused by these mechanical alterations frequently can be improved

nonsurgically Load-transferring

brac-es, shoe orthosbrac-es, shoe lifts, and an-algesics all may have potential ben-efit and should be tried before surgical intervention If these prove to be in-effective in relieving symptoms, os-teotomy may be considered The origin of pain in patients with angular malunion may be multifac-torial and is often unclear Potential etiologies include overloaded liga-mentous structures, local muscle and tendon irritation, and tensile strain of bone Theoretically, all of these

sourc-es of pain could be improved by cor-rective osteotomy

Uncertainty about the long-term outcome of malunion often has made decision-making problematic, espe-cially for patients with

asymptomat-ic angular malunion The mainstay of treatment in this group is patient ed-ucation about future risk of degener-ative arthritis At minimum, patients should be made aware that

osteoto-my is a treatment option should symptoms develop There are no de-finitive criteria to determine

wheth-er osteotomy is indicated; howevwheth-er,

in active individuals, commonly used guidelines are varus malalignment of the knee or ankle >10°, valgus mala-lignment of the knee or ankle >15°,

or a 20-mm medial shift in the me-chanical axis

A patient considering osteotomy for cosmetic reasons must have a clear understanding of the risk and mag-nitude of the contemplated procedure and have realistic expectations re-garding outcome Joint fibrosis, mus-cle weakness, and articular changes all may contribute to posttraumatic limb dysfunction and are not gener-ally improved with malunion correc-tion

Surgical Planning

Correction of angular deformity re-quires decisions to be made about the location and type of osteotomy and the method of osteotomy

stabiliza-tion Selection of an osteotomy site is

a balance between the geometrically

ideal position and biologic factors

Ideally, the angular correction should

be centered coincident with the

cen-ter of rotation of angulation, although

other considerations, such as the

quality of the soft-tissue envelope, the

healing potential of the osteotomized

bone, and the ability to provide rigid

internal fixation, may justify

move-ment of the osteotomy site from the

center of rotation of angulation

How-ever, if the osteotomy site is moved

from the center of rotation of

angu-lation, the intercalary segment

re-mains angulated, which will create a

secondary translation deformity

Of-ten these secondary deformities are

clinically insignificant; however, their

presence should be anticipated and

their consequences considered If the

preoperative plan suggests notable

deformity, accommodating

transla-tion may be planned for the distal

seg-ment

Each type of osteotomy—closing

wedge, opening wedge, neutral wedge,

dome, and oblique osteotomy and

dis-traction osteogenesis—has inherent

characteristics that should be

consid-ered in surgical decision-making

Clos-ing wedge osteotomy, in which the

cen-ter of rotation is on the concave side

of the deformity, is the most common

method of angular correction The

ad-vantages of this technique include the

ability to apply it directly at the

cen-ter of rotation of angulation, the

re-sultant contact of viable bone, and the

precision the osteotomy affords There

are several drawbacks to the closing

wedge osteotomy: extensive surgical

exposure is required; ligaments and

tendons that cross the osteotomy are

functionally lengthened; and the bone

segment is shortened with the removal

of the triangular wedge of bone The

length lost in the osteotomized bone

segment is equal to half the height of

the triangle’s base More complex are

the changes in leg length that result

from correction of the angular

defor-mity These changes are dependent on

the direction, location, and magnitude

of the deformity Despite the removal

of bone, a net increase in leg length often results from the correction No-mograms have been developed to as-sist in the estimation of overall leg length change from corrective oste-otomy.14Some qualitative conclusions can be drawn from these nomograms:

(1) correction of varus deformity al-ways results in leg lengthening, (2) the amount of lengthening from varus cor-rection is greatest adjacent to the hip and diminishes as the osteotomy ap-proaches the ankle, (3) correction of valgus deformity in the proximal third

of the femur leads to limb shorten-ing, and (4) length gains from correc-tion of distal valgus deformities are greatest at the knee and diminish to-ward the ankle

The advantages of opening wedge osteotomy are regained length and the ability to do the osteotomy

per-cutaneously or with an intramedul-lary saw The amount of lengthening

is equal to half the height of the dis-tracted triangular base The amount

of linear bone lengthening will be ad-ditive to any length derived from limb straightening The primary dis-advantages of this technique include the potential for introduction of un-wanted length and creation of a tri-angular bone defect In adults, trian-gular bone defect often must be filled with graft, which incurs the morbid-ity associated with graft harvest and

a risk of osteotomy nonunion Neutral wedge osteotomy (Fig 4) combines closing and opening wedge osteotomies A closing wedge osteot-omy is done on the convex side of the deformity, with the apex of the

resect-ed triangle in the middle of the os-teotomy site Opposing the surfaces

of the closing wedge creates an open-ing wedge on the contralateral side

Figure 4 Neutral wedge osteotomy combines the features of closing (A) and opening (B)

wedge osteotomies The resected wedge may be used on the contralateral side as an osteo-genic graft.

If the osteotomy apex is moved

slight-ly to the concave side of the middle

of the deformity, the resected

trian-gle of bone may be used as graft for

the resultant opening wedge defect

The rationale for movement of the

apex in a concave direction is to

ac-commodate for the bone lost in the

resected triangle from the passage of

a saw blade In this combined

osteot-omy, the point of rotation is the apex

of the closing wedge osteotomy, and

bone segment length should remain

unchanged

Dome osteotomy uses a bony cut

followed by correctional rotation

across this arced surface (Fig 5) The

arc of the osteotomy can be

consid-ered to be a portion of a circle, with

the center of the circle defining the

point of rotation of the osteotomy The

orientation of the concavity of the

dome is critical because its direction

defines the point of rotation Ideally,

this point of rotation will coincide with the center of rotation of angu-lation so that limb transangu-lation is not introduced Although the bone will

be restored to normal alignment over-all, residual angular deformity

with-in the segment of bone between the point of rotation and the osteotomy will remain This residual malaligned segment creates translation at the os-teotomy site Creating a dome with

as short a radius as practicable will minimize the translational effects of this segment Dome osteotomy is tra-ditionally done in the metaphyseal portion of long bones This allows the osteotomy to be made through can-cellous bone, with its inherent supe-rior healing capabilities The dome os-teotomy is advantageous because adjustments can be made in angular correction, no bone resection is re-quired, and the contacting metaphy-seal bone usually heals rapidly The primary disadvantages of the dome osteotomy are that it is generally re-stricted to metaphyseal sections of bone, angular correction is tied to translation across the osteotomy site, and there is no capacity to correct for rotation

Combined deformities of angula-tion and rotaangula-tion may be managed by creating an osteotomy oblique to the long axis of the bone If a tibia is split along the coronal plane, rotation of the anterior and posterior halves will result in only an angular change of these two parts If a horizontal osteot-omy is made in the middiaphysis, rotation of proximal and distal seg-ments results in only rotational change Between these two extremes are osteotomies that, when rotated, result in both rotational and angular correction This principle may be used

to create the single-cut osteotomy for correction of angulation and ro-tation.24,25The orientation of this os-teotomy has been defined by math-ematical formulas;24,25 the most straightforward determination of ori-entation is defined by the following formula:24

Angle from long axis in no-angu-lation view = arc tan

axial rotation angular deformity Intraoperatively, the no-angulation view of the bone is found with fluo-roscopy The cut is created with the width of the blade turned parallel to this plane, deviating away from the long axis of the bone by the defined angle (Fig 6) In malunions in which the angular deformity predominates, this cut becomes steep and difficult

to execute Advantages of this osteot-omy include a large surface area for healing and the ability to perform in-terfragmentary fixation and add length by sliding along the

osteoto-my surface after rotation

Angular correction also can be achieved with distraction osteogen-esis,26using hinges incorporated into

an external fixation frame The

hing-es are placed on the convex side of the deformity with the axis serving

as the point of rotational correction, thus creating a trapezoidal opening wedge, which has the potential of adding length An additional benefit

is that, after angular correction, the surgeon has the ability to resolve any residual length discrepancy with fur-ther distraction Placement of the hinges proximal or distal to the apex

of angulation may additionally allow for simultaneous translational correc-tion (Fig 7) Recently developed soft-ware advancements have expanded the capabilities of distraction osteo-genesis by allowing for the simulta-neous correction of length, angula-tion, translaangula-tion, and rotation with a single frame.27 Despite these frame advances, distraction osteogenesis continues to require prolonged peri-ods of external fixation with its atten-dant complications, including pin-tract infections, joint conpin-tracture, and delayed regenerate formation Be-cause of these potential difficulties, this technique is generally reserved for patients with complex

multipla-Figure 5 A and B, Dome osteotomies are

created as an arc with the point of rotation

(dot) centered at the center of rotation of

an-gulation Angular correction is correlated to

translation The larger the radius, the more

translation produced by a given angular

cor-rection.

nar deformity, length discrepancy, or

compromised soft tissue

The final component of surgical

planning is to determine the method

of osteotomy stabilization Cast

im-mobilization has the potential

advan-tage of allowing postoperative

adjust-ments, although the less rigid control

of osteotomy alignment is a

draw-back External fixation also allows

postoperative adjustment and

pro-vides increased rigidity relative to

casting However, pin-tract

complica-tions and the prolonged period of use

necessary for diaphyseal osteotomy

detract from its utility Locked

in-tramedullary devices can be used to

stabilize an osteotomy; if the

medul-lary canal remains, insertion of a rod

may help restore alignment.28 The

disadvantage is that a second

surgi-cal site is required for insertion Plate

fixation has been used most

common-ly in osteotomy stabilization Because open exposure is generally required for osteotomy, plate application may

be done through that incision The plate also may serve as an adjunctive tool for realignment If placed on the convex side, the plate may be fixed

to one end of the bone and a compres-sion device attached to pull the bone back into alignment.29 Another ad-vantage of plate fixation over in-tramedullary rods is the ability to sta-bilize short metaphyseal segments

Results

Because of the relative infrequency of corrective osteotomy for malunion, there is a dearth of clinical series dem-onstrating patient outcomes Graehl

et al30 reported on supramalleolar dome and wedge osteotomies done

in eight patients with tibial malunion Although complications were fre-quent, the seven patients who main-tained correction reported symptom-atic improvement Sanders et al31 performed oblique single-cut osteot-omies in 15 patients with tibial defor-mity Mean deformity was 14° in the coronal plane and 13° in the sagittal plane, with mean shortening of 2.2

cm In the 12 patients with adequate follow-up, osteotomy healed in 10 at

a mean of 4.5 months All 10 were able

to return to preinjury employment and were pleased with the surgical re-sult Average postoperative

deformi-ty correction was to within 1° in the coronal plane and 2° in the sagittal plane, with an average lengthening

of 1.3 cm Two failures were noted: one wound dehiscence and one frac-tured plate Based on their

experienc-es, the authors recommended this technique for correction of angular tibial deformity They were somewhat disappointed with their results in re-gaining limb length and

recommend-ed that distraction techniques be con-sidered if length discrepancy exceeds 2.5 cm No mention was made of pre-operative rotational deformity or the rotational changes necessarily in-curred with this technique.32 Sangeorzan et al33reported on four patients with combined rotational and angular deformity of the tibia With mathematical planning, all four patients obtained correction of angu-lation and rotation with a single-cut osteotomy One patient had postop-erative infection, which resolved with débridement and delayed primary closure In their series of 23 pediat-ric and adult patients treated for lower extremity deformity, Tetsworth and Paley23demonstrated the effec-tiveness of Ilizarov methodology in correcting deformity The average mechanical axis deviation was re-duced from 48 to 8.6 mm; the obliq-uity of the knee joint improved from 16° to 3° However, complications

Figure 6 A,Simultaneous correction of both angulation and translation is possible with

single-cut osteotomies B, The saw blade is oriented parallel to the plane of maximum

an-gular deformity at an angle of inclination (short dashed line) derived from a mathematical

formula Long dashed line = long axis of the bone.

were frequent, with universal

occur-rence of pin-tract infection and a 36%

incidence of major complications

Av-erage frame time was 158 days, and marked improvement occurred in the latter half of the study This suggests

that, as with many of these complex techniques, experience contributes to successful results

Summary

Normal lower extremity alignment is ideal for a mechanically efficient bi-pedal gait When components of the lower extremity are traumatically al-tered, function may be affected A thorough understanding of the signif-icance of the altered mechanics and

a preoperative plan that allows com-plete rectification of this

multifacet-ed, complex problem is necessary be-fore attempting surgical management

of lower extremity malunion The complexity of osteotomy and distrac-tion osteogenesis, and the compro-mise in local tissues imparted by pre-vious trauma, make these procedures susceptible to complication It is im-perative for the surgeon and patient

to consider fully the risks and ben-efits during the decision-making pro-cess

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