Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

142. Limb Lengthening Using the Ilizarov Method or a Monoplanar Fixator

Roger F. Widmann, Purushottam A. Gholve, and Arkady Blyakher

DEFINITION

images Limb lengthening is a surgical procedure performed to lengthen a bone.

images In the Ilizarov method, lengthening is accomplished by gradual bone distraction through a low-energy, atraumatic corticotomy site. The bone fragments are controlled via stable bone fixation using half-pins and tensioned wires through bone that are rigidly fixed to an external ring fixator or arch.11

images When a monoplanar fixator is used, lengthening is accomplished by distraction of the atraumatic corticotomy of the bone.9,18

ANATOMY

images Using the Ilizarov method, one can lengthen bones of both the upper and lower extremities, including bones of the hand and foot and the surrounding soft tissue.

images The most commonly lengthened bones in the lower extremity include the tibia and fibula, the femur, and the metatarsal. In the upper extremity, the most commonly lengthened bones are the humerus, the radius and ulna, and the metacarpal bones.

images Consideration is given to lengthening of the surrounding soft tissues, which include the muscle tendon unit, neurovascular bundle, and skin.11

images During bone lengthening, the tension in the surrounding soft tissue may predispose the lengthened segment to deformity12,19:

images Femur: varus and procurvatum

images Tibia: valgus and procurvatum

images Humerus: varus and procurvatum

images Radius and ulna: has a tendency to collapse in the interosseous space, which may cause synostosis

images Metatarsal and metacarpal: apex dorsal angulation

images During large lengthening, care is necessary to prevent subluxation or dislocation of the adjacent joint.19

images Femoral lengthening, especially in the setting of congenital short femur, may result in hip or knee subluxation or dislocation secondary to associated deficient acetabular coverage at the hip and the high frequency of deficient cruciate ligaments at the knee.

images Tibial lengthening may cause knee or ankle subluxation and progressive equinus deformity of the foot.

images Metatarsal and metacarpal lengthening can cause metatarsoor metacarpophalangeal subluxation.

images All of these issues are considered during any lengthening procedure.

PATHOGENESIS

images The term distraction osteogenesis implies synthesis of new bone by slow, gradual (no more than 1 mm per 24 hours) controlled distraction of the bone fragments under conditions of rigid fixation.11

images The new bone is formed mostly by intramembranous ossification and, to a lesser extent, through endochondral ossification.9,11

images To provide maximum construct stability and to minimize soft tissue trauma, it is important to maintain the two fragments well apposed to each other following the corticotomy.

images Distraction is a good tool for influencing reparative regeneration of both the bone and the soft tissue (“stretching tension,” as described by Ilizarov). However, the new regenerate ossifies and remodels slowly.

images Gradually removing distraction and applying mild compression increases the rate of remodeling. Therefore, the regenerate becomes more rigid against bending loads.

images To prevent any shortening of the segment from compression, preliminary over-distraction of up to 0.5 to 1 cm may be performed.

images Functional load is a strong stimulus for the improvement of blood flow and allows organic remodeling of the regenerated osseous part. The extent of load depends on the stability of fragments and the amount of regenerate.

NATURAL HISTORY

images The natural history of the limb-length discrepancy (LLD) depends on the condition causing the LLD.16,22 A partial list of causes follows:

images Congenital shortening: Proximal focal femoral deficiency, coxa vara, congenital short femur, fibula and tibia hemimelia, hemiatrophy

images Congenital lengthening: Overgrowth syndromes such as hemihypertrophy, Beckwith-Weidemann syndrome, KlippelTrenaunay-Weber syndrome, and Parke-Weber syndrome

images Skeletal dysplasia or tumor: Multiple hereditary exostoses may result in limb shortening on the affected side as growth cartilage cells are diverted to the cartilage tumor.18 Radiation for malignancies adjacent to the physis may result in growth suppression or complete destruction of physeal cartilage cells, resulting in limb-length discrepancy or angular deformity.

images Infection: Physeal destruction may result from physeal invasion from adjacent metaphyseal or epiphyseal bacterial osteomyelitis, or direct physeal involvement in the case of intracapsular joint physes such as at the hip and shoulder.

images Paralysis: Poliomyelitis and cerebral palsy as well as other nervous system afflictions in children typically result in shortening on the more affected side.

images Trauma: Direct injury to growth plate, posttraumatic bone loss or shortening, and overgrowth following femoral fracture

images Miscellaneous: Slipped capital femoral epiphysis, LeggCalvé-Perthes disease

images Upper extremity discrepancy or shortening usually does not cause major functional problems, but may result in significant cosmetic deformities.

images Predicted lower extremity discrepancy of 3 to 5 cm may be dealt with by long-leg epiphysiodesis in children or by leg lengthening using the Ilizarov technique. LLD greater than 5 cm usually is amenable to leg lengthening.22

images In children, the LLD at maturity can be predicted in a variety of ways:

images The arithmetic method13

images The growth remaining method1

images The Moseley straight line method15

images The Paley multiplier technique20

images Untreated LLD of more than 3 cm may result in pelvic obliquity, visual gait disturbance, short-legged gait, or structural/nonstructural scoliosis.22

images LLD greater than 5.5% of the long leg has been shown to decrease the efficiency of gait, as determined from kinetic data.21

PATIENT HISTORY AND PHYSICAL FINDINGS

images The common symptoms at presentation are limp, compensatory gait mechanics, pelvic obliquity, and nonstructural scoliosis.

images Physical findings depend on the etiologic factors.22

images In hemihypertrophy (both syndromic and nonsyndromic), the affected extremity may be larger in both length and girth. In classic hemihypertrophy, upper extremity hypertrophy as well as hemifacial asymmetry may be present. Vascular overgrowth syndromes may be associated with cutaneous or deep hemangiomas, which may alter surgical approaches to attempted limb equalization.

images Clinically, LLD is best measured by the block test, in which the shorter leg is placed on increasingly larger measured blocks until the posterior iliac crest is level. Discrepancies as small as 2 cm are accurately detected by this method, and detection of discrepancies is largely unaffected by patient size or body mass. Direct measurement of leg length from anterosuperior iliac spine to the tip of medial or lateral malleolus is significantly less accurate.

images Apparent leg length is measured with the patient supine with the legs parallel to each other. The landmarks are the umbilicus to the tip of medial malleolus. Pelvic obliquity and fixed deformities of the hip and knee affect the reading.

images True leg length is measured from the anterior superior iliac spine to the tip of the medial malleolus. It is important to place the legs in identical positions to measure true leg length.

images If the patient has a 20-degree abduction deformity of right hip, the left hip is placed in 20 degrees of abduction to measure true length.22

images Range of motion is noted for all joints, primarily the hip, knee, ankle, and subtalar joints. The ankle joint range of motion is measured with the knee in extension and flexion.

IMAGING AND OTHER DIAGNOSTIC STUDIES

images Plain radiographs are helpful to document the objective measurement of LLD (FIG 1).

images Full-length (hip to ankle) anteroposterior (AP) radiographs are obtained in standing position with both patellae facing directly anteriorly. The appropriate-sized block is placed beneath the shorter leg to level the pelvis. A long x-ray cassette (51-inch) is used with the x-ray beam center focused on the knee from a distance of 10 feet. A radiolucent ruler often is used to assist in calculation of limb discrepancies.

images

FIG 1  A. Supine radiograph of a 10-year-old boy with a posteromedial bow of the tibia and a 4.5-cm leg length discrepancy. B. AP standing radiograph of a 6-year-old boy with a congenital short femur and a 4-cm limb length discrepancy.

images Other radiographic techniques described in the literature include teleoroentgenogram, orthoroentgenogram, and the criterion standard: the slit scanogram and the CT scanogram.10,14

images The CT scanogram is as precise in measuring LLD as the slit scanogram and it has the added benefit of more easily measuring LLD in the setting of joint contractures.

DIFFERENTIAL DIAGNOSIS

images True shortening (eg, femoral or tibial)

images Apparent shortening due to dislocated hip

images Apparent shortening from contractures

images Angular deformity causing apparent shortening

images Overgrowth syndrome with both increased length and limb girth: hemihypertrophy

images Congenital limb deficiency (beware knee joint instability)

NONOPERATIVE MANAGEMENT

images Nonoperative management is based on the amount of discrepancy16 :

images 0 to 2 cm: no treatment

images 2 to 6 cm: shoe lift (option for epiphysiodesis or lengthening in this range)

images More than 20 cm: extension prosthesis

SURGICAL MANAGEMENT

Preoperative Planning

Ilizarov Method

images Accurate radiographic measurement of current discrepancy and calculation of projected LLD at maturity

images Determination of which bony segment is affected

images Assessment of compensatory mechanics used for walking: equinus gait, circumduction, vaulting, or combination21

images Assessment of contractures: eg, extra- or intra-articular, bony

images Assessment of associated deformities: eg, angulation, translation, and rotation

images Long-leg standing radiographs in both planes help determine malalignment.

images

FIG 2  Either a template (A) or an actual ring (B) may be used to measure the ring size.

images Stability or laxity of joints (hip, knee, ankle) is determined clinically and radiographically.

images Skin condition: eg, open defect, scar tissue

images Planning for corticotomy level, for lengthening as well as for correction of associated deformity with appropriate room for wire or half-pin fixation.

images Determine optimum frame configuration, with or without inclusion of the adjacent joint.

images Details on ring size, half-pin, or K-wire placement

images Single-stage lengthening of 10% to 15% of bone length is associated with fewer complications.2

images Technical consideration.

images The Ilizarov frame may be constructed before surgery. The design of the frame and the number of rings and arches depend on the amount of lengthening planned.

images Separate threaded connecting rods are used between each ring block and the next. A rod spanning two or more rings allows less flexibility if adjustments are needed.

images Adequate skin clearance of at least 2 to 3 cm must be maintained circumferentially under the ring. Small rings are more rigid than large rings, but smaller rings may hinder skin care and may cause soft tissue compression if there is postoperative swelling.

images A template or an actual ring can be used to select the appropriate ring size (FIG 2).

images Due to the changing diameter of each limb segment, different ring sizes may be required for a single limb segment (for example, the diameter of the proximal arch for the femur typically is larger than the distal ring).

Monoplanar Fixation

images True measures of current discrepancy and calculation of projected LLD

images Compensation mechanisms used during walking: equinus gait, circumduction, vaulting

images Assessment of contractures: extra- or intra-articular

images Associated deformity: angulation, translation, and rotation

images Stability or laxity of joints: eg, hip, knee, ankle

images Skin condition: eg, open defect, scar tissue

images Long-leg films showing hip, knee, and ankle for lower extremity; and similar long films for the upper extremity

images Planning for corticotomy level; osteotomy level if needed for correction of associated deformity; and planning for points of fixation

images Choose appropriate size arch, rods, rail, half-pin and/or K-wires.

images Choose the appropriate size of the fixator (pediatric or adult)

Positioning

images Lower extremity: Supine position on any radiolucent table (eg, Jackson table)

images Upper extremity: Supine position with arm over a radiolucent table

images Intraoperative fluoroscopy (for both the AP and lateral images)

images For the Ilizarov method.

images Place rolled sheets (as bumps) beneath the ipsilateral buttock and proximal tibia, leaving the femur free (FIG 3A). Similarly, for the tibia, a rolled sheet is placed beneath distal femur and ankle to create space for the tibial frame (FIG 3B).

images Place a sandbag beneath the ipsilateral shoulder/scapula and rolled sheets (as bump) beneath the humerus and radius ulna to create a space for the frame.

images For monoplanar fixator use, place rolled sheet (as bumps) beneath the femur and tibia to create working space for application of the frame.

images

FIG 3  A. Patient positioned over the radiolucent table with a bump under the ipsilateral buttock and proximal tibia, leaving the femur relatively free. B. Patient positioned over the radiolucent table with a bump under the distal femur and ipsilateral ankle, leaving the tibia relatively free.

TECHNIQUES

LIMB LENGTHENING USING THE ILIZAROV METHOD

Tibial Lengthening

Wire Insertion

images The wire insertion site is determined by local anatomy and the use of cross-sectional anatomic atlases to protect and avoid damage to blood vessels, nerves, and tendons.

images In small children, 1.5-mm fixation wires are used; in adolescents and adults, 1.8-mm fixation wires are used. The wires usually are tensioned to 100 kg in children and to 130 kg in adults.

images The wire is introduced from the side nearest the neurovascular bundle. This helps prevent inadvertent injury to the neurovascular structures.

images Initially the wire is gently pushed through the soft tissue until it hits bone cortex. The center of the bone is located, and the wire is drilled through the cortex. It is important not to bend the wire while drilling.

images The wire is prevented from bending by a short lever arm on the wire that holds the wire with a wet sponge or by use of a protective soft tissue sleeve (TECH FIG 1).

images After piercing the far cortex, the lowest possible drill speed is used to further insert the wire. After exiting the far skin, the wire is inserted further by tapping with a mallet.

images The wire is fixed to the ring without bending the wire. Bent wires will move the bony fragments on tensioning.

images Any tension or puckering of the skin at wire insertion or exit is corrected by releasing the surrounding skin or fascia with the help of a no. 15 blade on a scalpel.

Half-Pin Insertion

images Hydroxyapatite-coated half-pins are recommended, because they achieve better fixation and are associated with lower rates of infection and loosening.3

images The size of the half-pin should not exceed one-third the diameter of the bone segment being fixed.

images Freehand techniqu.

images Identify the optimal site for pin insertion.

images Incise the skin over the insertion site, and then dissect down to the bone using a hemostat.

images Now drill the bone (both cortices) through a protective drill sleeve.

images The half-pin is introduced in the drilled track. The pin traverses only 1 to 2 mm through the far cortex, confirmed with fluoroscope.

images The half-pin is attached to the ring or arch, which is positioned perpendicular to the bone segment.

images If the half-pin insertion is not perpendicular to the bone, a post and half-pin fixation bolt are utilized.

images Ring guide techniqu.

images First the ring or arch is fixed perpendicular to the bone with a wire.

images Depending on the optimal site for pin insertion, the half-pin fixation bolt or Rancho cube is attached to the ring.

images Now the sleeve is introduced through the half-pin fixation bolt or cube, and the skin site is marked.

images The skin is incised and dissected to the bone using a hemostat.

images The sleeve is advanced further to contact the bone.

images The drill is introduced through the sleeve, and the bone is drilled (both cortices).

images The half-pin is introduced in the drilled track. The pin traverses 1 to 2 mm through the far cortex, and this is confirmed fluoroscopically.

images The half-pin fixation bolt or the cube is tightened over the pin.

Fibular Osteotomy and Anterior Compartment Fasciotomy

images The osteotomy is done at the junction of the proximal and middle thirds of the fibula. Avoid osteotomies of both the tibia and fibula at same level.

images The fibula is approached laterally through the plane between the peroneus longus and the lateral intermuscular septum. The periosteum is incised with a sharp knife and is elevated circumferentially with a periosteal elevator.

images

TECH FIG 1  Bending of wire during insertion is prevented by holding the wire with a wet sponge (A) or with a protective soft tissue sleeve (B).

images A Hohmann or Bennett retractor then is placed around the exposed fibula to protect the surrounding soft tissue.

images The fibula is osteotomized, either with an oscillating saw or using an osteotome, after placing several drill holes through both cortices. Irrigation fluid is used to prevent thermal necrosis while using the saw or drill.

images An oblique osteotomy is used to have larger contact area between the two fragments.

images The skin and subcutaneous tissues are closed without closing the underlying fascia.

images Now the skin is incised over the tibial corticotomy site. The corticotomy site usually is the proximal metaphysis.

images Prophylactic fasciotomy of the anterior compartment may be performed by releasing the anterior compartment fascia distally and proximally with a Metzenbaum scissor.

images We recommend fasciotomy before the frame is mounted, because more space is available to work. However it can be done later after mounting the frame.

images Now a temporary suture is placed over the proximal tibial incision, deferring the corticotomy until later in the procedure.

Ilizarov Frame Application

images For simple lengthening (without deformity), three rings (or two rings and one arch) are used.

images Introduce a transverse proximal tibial wire perpendicular to the shaft and below the growth plate in children (TECH FIG 2, #1).

images To avoid penetrating the joint capsule, the transverse wire should be no closer than 14 mm to the subchondral bone of the proximal tibia.

images Attach the proximal ring (previously constructed frame) to this wire, and tension the wire with a wire tensioner. Adequate ring clearance from the soft tissues must be verified circumferentially.

images Another transverse wire is introduced in the distal metaphysis of the tibia proximal to the distal growth plate and fixed to the distal ring (TECH FIG 2, #2).

images The biomechanical and anatomic axis of the tibia is the same in the absence of deformity.

images The lengthening rods are placed parallel to the biomechanical axis. Radiographically, the rods should be parallel to the posterior cortex on the lateral view and parallel to the longitudinal axis of the tibia on the AP view.

images Next a wire is placed proximally, passing from lateral to medial. This wire enters the fibular head (just distal to the proximal fibular growth plate), traversing the tibia and exiting through the anteromedial tibial cortex.

images Care is necessary to prevent damage to the peroneal nerve, which is in close proximity to the fibular neck.

images The wire is then fixed and tensioned to the proximal ring.

images Now two half-pins are placed in the most proximal ring. In this configuration, there should ideally be 90 degrees of angulation between the two pins (TECH FIG 2, #3).

images Usually a half-pin fixation bolt is required with one half-pin and a one-hole cube for the other half-pin, so that the pins are placed at slightly different levels.

images It is important not to damage the tibial tubercle and proximal tibial physis while placing the half-pins or wires.

images Next, a wire is placed distally through the fibula and tibia just above the growth plate at the level of the syndesmosis (TECH FIG 2, #4). This wire is attached and tensioned to the distal ring.

images Place the fibula-tibia wire more than 12.2 mm from the distal tibia subchondral surface to avoid capsular penetration and the risk of joint sepsis.

images A half-pin is introduced just proximal to the distal ring in an anteromedial direction. It is then fixed to the distal ring (TECH FIG 2, #5).

images One or two half-pins are similarly introduced just above and below the middle ring and are securely fixed to the middle ring (TECH FIG 2, #6).

images The connecting rods between the proximal and middle rings are then disconnected, and attention is directed to the corticotomy site.

images Extra-periosteal dissection is performed at the proximal tibial metaphyseal osteotomy site.

images

TECH FIG 2  The sequence and placement of K-wires or halfpins in tibial lengthening. 1, Proximal transverse tibial wire perpendicular to the shaft and below the growth plate in children. This wire is placed anterior to the fibula head. 2, Transverse wire in the distal metaphysis of the tibia proximal to the distal growth plate. 3, Two half-pins are inserted proximally, one above and one below the proximal ring at an approximate angle of 90 degrees to one another. 4, Distal wire through the fibula and tibia above the growth plate at level of syndesmosis. 5, Distal tibial half-pin is introduced in the anteromedial direction. 6, One or two half-pins are introduced, just above and below the middle ring.

images

TECH FIG 3  A. Multiple drill holes are made in the anterior/anteromedial tibial cortex. B. A 5-mm osteotome is advanced through the bone at the level of drill holes in a regulated manner. Lateral fluoroscopic imaging is helpful to judge depth.

images The periosteum is not elevated circumferentially, in order to preserve the blood supply.

Corticotomy

images Multiple drill holes are made in both tibial cortices from anterior to posterior. If necessary, additional drill holes can be made at the same level from another point over the anteromedial cortex (TECH FIG 3A).

images A 5-mm osteotome is advanced through the bone at the level of the drill holes (TECH FIG 3B).

images First the anteromedial cortex is osteotomized, followed by the anterolateral cortex. Each time the osteotome passes through the far cortex, it is twisted with a wrench to cause a controlled fracture in the cortex.

images Finally, a wider osteotome is seated in the posterior cortex and twisted with a 14-mm wrench to break the posterior cortex.

images The corticotomy is confirmed by externally rotating the distal block. Internal rotation is avoided, because it places tension on the common peroneal nerve. The fragments are rotated back to the normal reduced position.

images The rods between the proximal and distal blocks are reconnected as they were before the corticotomy, and the osteotomy is reduced.

images The use of square nuts or clickers on the connecting rods allows future distraction.

Wound Closure

images The skin is closed without closing the underlying fascia.

images Check that all the nuts and bolts are tight.

images Put a dressing (eg, Xeroform [Covidien, Mansfield, MA], sponges) around the wires and half-pins. Pressure dressing is applied over the fibular and tibial corticotomy sites. Place the dressing material between the frame and the surgical wound.

images The foot is placed in a plantigrade position and a foot-plate is attached. When planning a large lengthening, the foot may be included in the frame to prevent progressive equinus deformity of the ankle.

images Similar consideration is given to including the knee in the frame for large lengthening or in the setting of cruciate ligament laxity.

Taylor Spatial Frame

images The Taylor Spatial Frame (TSF; Smith & Nephew, Andover, MA) has Web-based spatial software, which helps to calculate correction of deformity or lengthening of the bone.

images Deformities can be corrected using chronic deformity correction, the rings-first method, or the residual deformity method.

images In the TSF, the proximal and distal blocks may or may not be connected preoperatively.

images The number and site of wire/half-pin fixation, the number of rings, and the basic construct of the frame are similar to those described earlier.

images The details of fibular osteotomy and anterior compartment fasciotomy are the same.

images Mount the frame and secure with wires and half-pins.

images The proximal and distal blocks are connected with six connecting struts. The details of the strut lengths are recorded, after which the struts are disconnected and corticotomy is completed as discussed earlier.

images The corticotomy is reduced, and the struts are reconnected the way they were before the corticotomy (TECH FIG 4).

images The deformity, frame, and mounting parameters are entered in the software program, which prescribes a lengthening/corrective program.

images The rate of distraction is determined based on local bone and soft tissue status. Typically, it is 1 mm per day in healthy bone and soft tissue.

images

TECH FIG 4  A two-level osteotomy was performed on the patient shown in Figure 1A with the goal of distal deformity correction and proximal tibia lengthening with application of a Taylor spatial frame.

Femoral Lengthening

images The usual frame construct for simple femoral lengthening (without deformity) is composed of two rings and one arch.

images Initially, a transverse wire is placed in the distal femur, parallel to the knee joint line and proximal to the growth plate in children (TECH FIG 5A, wire 1). The direction of the wire is from lateral to medial.

images The previously constructed frame is mounted, and the distal ring is attached to this wire. The wire is then tensioned. All the rings, including the arch, should have at least one or two fingerbreadths clearance from the anterior and posterior surface of the thigh.

images The mechanical and anatomic axes of the femur are not identical as in the tibia. The mechanical axis is drawn from the center of the femoral head to the center of the knee joint, whereas the anatomic axis is the central axis of the femoral shaft. The anatomic axis forms a 7-degree angle with the mechanical axis.

images A transverse half-pin is introduced in the lateral proximal femur perpendicular to the mechanical axis, using the ring guide technique (TECH FIG 5A, pin 2). The pin is placed centrally in the lateral cortex and is fixed to the proximal arch.

images The frame rods are placed parallel to the mechanical axis. Radiographically, the rods are parallel to the posterior cortex on the lateral view and parallel to the mechanical axis (marker from center of femoral head to the center of knee joint) on the AP view.

images Next, two half-pins are placed in the distal femur proximal to the growth plate. The direction of these half-pins is from posterolateral to anteromedial and from posteromedial to anterolateral (TECH FIG 5A, pin 3).

images While introducing half-pins, it is necessary to flex the knee to avoid placement across the tendon and muscle (ie, biceps femoris, semitendinosus, semimembranosus). Care is necessary to prevent any damage to the common peroneal nerve, which is in close relationship with the biceps femoris.

images One or two half-pins are introduced in the proximal femur (TECH FIG 5A, pin 4). The half-pins are fixed to the proximal arch using different-size Rancho cubes to avoid pin placement at the same level.

images Next, one or two half-pins are placed adjacent to the middle ring (TECH FIG 5A, pin 5).

images The rods between the middle and distal rings are disconnected for corticotomy of the distal femoral metaphysis.

images A skin incision is made over the anterolateral distal femur close to the distal metaphysis. The deep tissue is incised, and the vastus lateralis is elevated by blunt dissection to expose the lateral femoral cortex without disturbing the underlying periosteum. The osteotomy is performed approximately 1 cm proximal to the most proximal wire or half-pin attached to the distal ring.

images The cortex is drilled at the same level, with multiple drill holes at varying angles. A 5-mm osteotome is advanced through the anterior, lateral, medial, and posterior cortices.

images Each time the osteotome is fully seated through the far cortex it is twisted with a wrench to cause an atraumatic fracture in the cortex. The corticotomy is confirmed by externally rotating the distal ring.

images The fragments are rotated back to the normal reduced position. This will decrease bleeding from the cut bony surfaces.

images The rods are reconnected as before the corticotomy. Square nuts or clickers are used with these connecting rods to allow for controlled distraction.

images The corticotomy site is closed. A check is done to tighten all nuts and bolts (TECH FIG 5B).

images

TECH FIG 5  A. The sequence and placement of K-wires or half-pins in femur lengthening. 1, Transverse wire in the distal femur, which is parallel to the knee joint line and proximal to the growth plate in children. 2, A transverse half-pin in the lateral proximal femur perpendicular to the mechanical axis. 3, Two half-pins in the distal femur directed from posterolateral to anteromedial and from posteromedial to anterolateral cortex. 4, One or two additional half-pins in the proximal femur. 5, One or two half-pins adjacent to the middle ring. B. A completed femoral frame with rings, connecting rods, wire/halfpins, and distal metaphyseal corticotomy.

images During large lengthening and in presence of knee ligament laxity, one should consider extending the frame across the knee joint.

Taylor Spatial Frame

images When using the TSF for femoral lengthening, the proximal and distal blocks may or may not be connected preoperatively.

images The number and site of wire/half-pin fixation, number of rings, and basic construct of the frame are similar to those described with the Ilizarov technique.

images Mount the frame and secure with wires and half-pins.

images The proximal and distal blocks are connected with six connecting struts. The details of the strut lengths are noted. Then the struts are disconnected and corticotomy is completed as discussed earlier.

images The corticotomy is reduced, and the struts are reconnected at the same lengths as before corticotomy (TECH FIG 6). This results in anatomic reduction at the osteotomy site.

images The deformity, frame, and mounting parameters are entered in the software program, which prescribes a lengthening/deformity correction program. Lengthening proceeds at 1 mm/day under normal circumstances.

images

TECH FIG 6  A distal femur osteotomy was performed on the patient shown in Figure 1B after application of a femur frame with extension across the knee to include the tibia. The femur and tibia frames were connected with hinges to prevent knee subluxation during lengthening.

MONOPLANAR FIXATOR ASSEMBLY

Technical Considerations

images Monolateral fixators stabilize bone fragments using percutaneous half-pins to transfix the bone with external fixation of the half-pin to the clamp, rail, rod, or arch.

images Some monoplanar systems use arches or rings to achieve multiplanar fixation.

images Advantages of monoplanar fixators22.

images Greater patient comfort during femur and humerus lengthening

images Less bulky frame

images Simple construct

images Disadvantages of monoplanar fixators 11,22:

images Less rigid

images Less flexible: eg, the MAC frame (EBI, Parsippany, NJ) has a universal hinge that allows correction of angular deformity and a translation device that allows correction of translation in two directions.

images Not recommended for large lengthening (more than 5 cm)

images The monolateral frame is constructed before the surgery is done. The design of the frame, including the number of clamps and arches, depends on the planned lengthening.

images Rail size depends on the planned lengthening.

images Techniques to increase frame stability include:

images Increase number of half-pins

images Increase diameter of the half-pins (pin diameter should not exceed a third of the bone diameter)

images Greatest possible angle between half-pins (maximum, 90-degree angle)

images Reduce distance between the bone and the external frame.

images Increase the distance between half-pins.

images Fixation as close to the corticotomy as possible.

Femoral Lengthening

images For simple lengthening (without deformity), three-point fixation is required in each segment.

images Use guidewire technique to place the first half-pin in the distal femur. A guidewire is introduced parallel to the knee joint line and proximal to the growth plate in children.

images Because the femur has a natural anterior bow, the guidewire is placed slightly anterior (not central) in the lateral femoral cortex (TECH FIG 7A, #1).

images The bone is drilled over the guidewire with a 4.8-mm or 3.2-mm cannulated drill bit (depending on the size of half-pin to be used). Then a self-tapping, hydroxyapatitecoated half-pin is introduced in the drilled track (TECH FIG 7B, #1).

images Attach this half-pin to the clamp, which is connected to the rail (monolateral fixator).

images At least one fingerbreadth of distance is maintained between the external frame and the lateral surface of the proximal thigh.

images A second half-pin is introduced in the proximal femur perpendicular to the biomechanical axis and fixed to the proximal clamp (TECH FIG 7B, #2).

images This half-pin is also placed slightly anterior (not central) in the lateral femoral cortex (TECH FIG 7A, #2).

images With intraoperative fluoroscopy, check the AP and lateral relationships of the frame with the femur. The frame should be located parallel to the biomechanical axis on the AP view (TECH FIG 7B, #3). On the lateral view, all the holes of the proximal and distal clamp should overlie the bone.

images Introduce two or more half-pins through the empty holes of the proximal clamp (TECH FIG 7B, #4).

images

TECH FIG 7  A. Lateral view of the femur. The guidewire and half-pin are placed just slightly anterior (not central) in the lateral femoral cortex. B. The sequence and placement of half-pins in femur lengthening. 1, A half-pin is placed in the distal femur parallel to the knee joint line and proximal to the growth plate in children. 2, The second half-pin is introduced in the proximal femur perpendicular to the biomechanical axis. 3, The frame/rail is placed parallel to the biomechanical axis in AP view. 4, One or two half-pins are introduced through the empty holes of the proximal clamp. C. The proximal part of the distal clamp is approximately angulated by 10 to 15 degrees anteriorly.

images During femoral lengthening, soft tissue tension predisposes the femur to develop procurvatum deformity.

images Procurvatum deformity can be prevented by making simple adjustments during frame application. After the proximal half-pins have been placed, the rail is disengaged from the proximal clamp. The distal clamp is then angulated by 10 degrees anteriorly (TECH FIG 7C).

images The additional two half-pins are then placed in the distal clamp. This pin placement creates a mild recurvatum deformity (10 degrees), which compensates for the predicted procurvatum deformity.

images At this point the frame is removed in preparation for corticotomy. The distance between the clamp and the skin is marked on the half-pins.

images Gloves are changed, and the skin at the level of the corticotomy is prepped again.

images The femoral corticotomy is completed following the same principles discussed earlier.

images After completion of the corticotomy, the frame is reapplied, maintaining the same distance between the clamps and the skin.

images Fluoroscopy is used to confirm the slight recurvatum deformity. This recurvatum deformity compensates for the procurvatum tendency during lengthening of femur.

images The skin is closed after repair of the tensor fascia.

images The distraction device is connected to the clamps, and final tightening is performed.

images Half-pins are dressed with Xeroform gauze and sponges.

Tibial Lengthening

images For simple lengthenings (without deformity), two- or three-point fixation is required in each bony segment.

images The tibial frame usually includes a proximal clamp or arch with two or three half-pins and a distal fixation clamp with two or three half-pins.

images Fibular osteotomy is performed first (as discussed previously).

images A distal tibia-fibula transfixation screw is required to prevent distal tibia-fibula subluxation.

images The skin is incised over the tibial corticotomy site, which usually is the proximal metaphysis.

images Prophylactic fasciotomy of the anterior compartment is performed under direct vision before frame application.

images Now a temporary suture is placed at the corticotomy skin incision, and corticotomy is performed after pin fixation is complete.

images Two half-pins are introduced in the proximal tibial metaphysis perpendicular to the shaft and distal to the growth plate (TECH FIG 8, #1). The half-pins are placed in the anteromedial and anterolateral cortex, with care to avoid the tibial tuberosity.

images

TECH FIG 8  The sequence and placement of half-pins in tibial lengthening: AP (A) and lateral views (B). 1, Two half-pins in the proximal tibia; 2, the frame is parallel to the biomechanical axis; 3, the half-pin is inserted in the distal tibia through the distal clamp; 4, two half-pins are placed distally through the distal clamp; 5, corticotomy site.

images The half-pin configuration should aim for pin spread of 90 degrees. The half-pins are introduced at different levels. The first half-pin is placed freehand. The arch is placed parallel to the proximal tibial joint line, and the second half-pin is placed through the clamp.

images The anterior aspect of the arch should be at least a fingerbreadth from the anterior cortex.

images In the absence of deformity, the mechanical and anatomic axis of the tibia are the same. The mounted frame should be parallel to the biomechanical axis in both the AP and lateral views (TECH FIG 8, #2).

images A half-pin is then introduced in the distal tibia through the clamp (TECH FIG 8, #3). Once again, parallel alignment of the frame with the mechanical axis is confirmed.

images Two additional half-pins are placed distally through the distal clamp (TECH FIG 8, #4).

images The distance of the clamps from the skin is marked on the half-pins. The frame is then removed in preparation for the corticotomy.

images Gloves are changed, and the skin at the level of the proximal tibial metaphysis is prepared again.

images The tibial corticotomy is completed following the same principle discussed earlier (TECH FIG 8, #5).

images The frame is reapplied, maintaining the same distance between the clamps and the skin as measured before the corticotomy.

images A properly executed procedure will not have any residual displacement at the corticotomy site.

images The skin is closed, leaving the underlying fascia open.

images The distraction device is connected to the clamps, and final tightening is performed.

images Half-pins are dressed with Xeroform and sponges. A pressure dressing is applied over the corticotomy site.

images The foot is placed in a plantigrade position.

images

POSTOPERATIVE CARE

images Distraction is started after a latency period of 7 to 10 days (depending on the age of the patient, the level of the corticotomy, and the local blood supply).6,11,18

images The rate of distraction is 1 mm per day, distributed as 0.25 mm four times a day.6,11,18

images Pin care is done with half-strength hydrogen peroxide and normal saline.

images Showering is allowed 1 week after the surgery, with antibacterial soap.

images Full weight bearing is encouraged as tolerated.

images Physical therapy to maintain range of motion and prevent contractures:

images Minimum: three times a week, and a home program is performed four times a day

images During active lengthening, the patient is seen once per week.

images Routine perioperative intravenous antibiotic prophylaxis is used.

OUTCOMES

Ilizarov Technique

images In 1995, Stanitski et al23 reported the results of 36 femoral lengthenings in 30 consecutive patients using the Ilizarov technique. The etiology of femoral shortening was congenital in 21 femurs and acquired in 15. The average lengthening was 8.3 cm (range, 3.5 to 12 cm), with a treatment time of 6.4 months (range, 2.5 to 12 months). Complications included premature consolidation in four patients, malunion of more than 10 degrees in two patients, and residual limb length inequality (less than 2 cm) in two patients. Two patients developed knee subluxation. There were no reports of osteomyelitis, ring sequestra, neurologic or vascular compromise, compartment syndrome, hypertension, or hip or knee dislocations in their series. Psychological problems necessitated cessation of lengthening in two patients.

images These results show a significant improvement over previous reports of earlier techniques of femoral lengthening in terms of greater lengthening, simultaneous deformity correction, and fewer major complications.

images Stanitski et al24 reported tibial lengthening for 62 tibiae in 52 patients using the Ilizarov technique. The average lengthening was 7.5 cm (range, 3.5 to 12 cm). Twenty-eight (22%) patients required unplanned procedures, which included osteotomy for malunion or deformation of the regenerate and Achilles tendon for persistent equinus contracture. The complication rate decreased after the initial learning curve.

Monoplanar Fixator

images Coleman and Noonan4 reported results of distraction osteogenesis in 114 femurs and 147 tibias treated with monoplanar external fixator for a variety of different conditions. Mean femoral lengthening was 11 cm, or 48% of the original femur length. The femora that gained more length (expressed as percentage of original length) had poor healing indices.

images Interestingly, LLD was more difficult to correct with distraction osteogenesis than short stature. In tibia the mean tibial lengthening was 9 cm or 41% of the original tibial length. The mean healing index was 32 days per centimeter of lengthening. The complication rate was 1.33 per tibia. Seemingly, obstacles or problems were also considered as complications in their study.

images Overall, good results were obtained. They concluded that larger lengthenings are possible, but the cost is increased time and complications.

COMPLICATIONS

Intraoperative

images Ilizarov method: Compartment syndrome is rare, but may occur early following the surgery. Pain with passive stretch and paresthesias are important clinical signs of compartment syndrome. Measure compartment pressures and decompress the affected compartment as needed. Prophylactic anterior compartment release may be performed at the time of corticotomy.18,19

images Monoplanar fixator

images Incomplete corticotomy: Confirm complete corticotomy by externally rotating the distal fragment under fluoroscopic imaging.

images Avoid neurovascular injury by placing half-pins through safe zones.5 Use a cross-sectional atlas.

images Avoid paralyzing anesthetic agents during surgery, because they may mask nerve injury.5,19

Distraction Period

images Pin tract infection initially is treated with a short course of oral antibiotics (7 to 10 days) and appropriate pin tract care. If infection persists, consider intravenous antibiotics or removal of the wire or half-pin with curettage of the infected site.

images Premature consolidation may be due to incomplete osteotomy, slow distraction rate, or incorrect direction of distraction.

images Neurologic symptoms may arise in the form of altered sensation or weakness of the muscle. The wire or half-pin is removed if direct contact or irritation of the nerve is suspected. Stretching of the nerve with rapid distraction may result in nerve injury, and it may be necessary to decrease the rate of distraction or even stop distraction temporarily.5,19,25

images Surgical nerve decompression occasionally is required to release the nerve from compressing structures.

images Unplanned deformity may develop during bone lengthening. Appropriate frame modifications may be required to correct the deformity.12,19

images Joint contractures may occur during lengthening. Treatment includes increasing the number of physical therapy sessions and use of dynamic splinting, especially to prevent equinus contracture.

images Iatrogenic deformity may develop during lengthening. Frame modifications may be required to correct the deformity and maintain a neutral mechanical axis.7,8

images Compartment syndrome is rare (the anterior compartment is always released intraoperatively) but may occur following surgery. Paresthesia, pain with passive stretch, and pain out of proportion to the surgical procedure are clinical indicators of compartment syndrome. Compartment pressures should be measured, and compartments should be released as needed.4

Consolidation Period

images Pin tract infection (as described earlier).

images Delayed consolidation of regenerate may respond to electrical or ultrasound bone stimulator. The frame can be dynamized or the regenerate can be compressed by 0.5 cm.

After Frame Removal

images The regenerate bone may deform after premature frame removal (eg, poor regenerate, fewer than three continuous cortices). This can be prevented by frame dynamization prior to frame removal and protected weight bearing.

images Assess the regenerate bone clinically and radiographically at the time of frame removal. Consider use of a cast or brace and protected weight bearing in the setting of questionable bone regenerate.

images Stress fracture can occur either at the site of half-pins, especially when the half-pin size exceeds one third the diameter of the cortex, or through the regenerate bone. Fracture is treated with reapplication of the frame, casting, intramedullary rod fixation, or plate application.5

REFERENCES

· Anderson M, Green WT, Messner MB. Growth and predictions of growth in the lower extremities. J Bone Joint Surg Am 1963; 45A:1–14.

· Bassett G, Morris J. The use of the Ilizarov technique in the correction of lower extremity deformities in children. Orthopaedics 1997; 20:623–627.

· Caja VL, Piza G, Navarro A. Hydroxyapatite coating of external fixation pins to decrease axial deformity during tibial lengthening for short stature. J Bone Joint Surg Am 2003;85A:1527–1531.

· Coleman S, Noonan T. Anderson's method of tibial-lengthening by percutaneous osteotomy and gradual distraction. J Bone Joint Surg Am 1967;49A:263–279.

· Dahl MT, Gulli B, Berg T. Complications of limb lengthening: a learning curve. Clin Orthop Relat Res 1994;301:10–18.

· De Bastiani G, Aldegheri R, Renzi-Brivio L, et al. Limb lengthening by callus distraction (callotasis). J Pediatr Orthop 1987;7:129–134.

· Glorion C, Pouliquen JC, Langlais J, et al. Femoral lengthening using the callotasis method: study of the complications in a series of 70 cases in children and adolescents. J Pediatr Orthop 1996;16:161–167.

· Guidera K, Hess W, Highhouse K, et al. Extremity lengthening: results and complications with the Orthofix system. J Pediatr Orthop 1991;11:90–94.

· Hamdy RC, Silvestri A, Rivard CH, et al. Histologic evaluation of bone regeneration in cases of limb lengthening by Ilizarov's technique: an experimental study in the dog. Ann Chir 1997;51:875–883.

· Huurman WW, Jacobsen FS, Anderson JC, et al. Limb-length discrepancy measured with computerized axial tomographic equipment. J Bone Joint Surg Am 1987;69:699–705.

· Ilizarov GA. Clinical application of the tension-stress effect for limb lengthening. Clin Orthop Relat Res 1990;250:8–26.

· Leyes M, Noonan K, Forriol F, et.al. Statistical analysis of axial deformity during distraction osteogenesis of the tibia. J Pediatr Orthop 1998;18:190–197.

· Menelaus MB. Correction of leg length discrepancy by epiphyseal arrest. J Bone Joint Surg Br 1966;48:336–339.

· Millwee RH. Slit scanography. Radiology 1937;28:483–486.

· Moseley CF. A straight line graph for leg length discrepancies. J Bone Joint Surg Am 1977;59A:174–179.

· Moseley CF. Leg-length discrepancy. In: Morrissey RT, Weinstein SL, eds. Lovell and Winter's Pediatric Orthopaedics, 6th ed. Philadelphia; Lippincott Williams & Wilkins, 2006:1231–1256.

· Noonan KJ, Leyes M, Forriol F, et al. Distraction osteogenesis of the lower extremity with use of monolateral external fixation. A study of two hundred and sixty-one femora and tibiae. J Bone Joint Surg Am 1998;80A:793–806.

· Paley D. Current techniques of limb lengthening. J Pediatr Orthop 1988;8:73–92.

· Paley D. Problems, obstacles and complications of limb lengthening by the Ilizarov technique. Clin Orthop Relat Res 1990;250:81–104.

· Paley D, Bhave A, Herzenberg J, et al. Multiplier method for predicting limb-length discrepancies. J Bone Joint Surg Am 2000;59A: 1432–1446.

· Song KM, Halliday SE, Little DG. The effect of limb-length discrepancy on gait. J Bone Joint Surg Am 1997;79:1690–1698.

· Stanitski DF. Limb-length inequality: assessment and treatment options. J Am Acad Orthop Surg 1999;7:143–153.

· Stanitski DF, Bullard M, Armstrong P, et al. Results of femoral lengthening using the Ilizarov technique. J Pediatr Orthop 1995;15:224–231.

· Stanitski DF, Shahcheraghi H, Nicker DA, et al. Results of tibial lengthening with the Ilizarov technique. J Pediatr Orthop 1996;16: 168–172.

· Young NL, Davis RJ, Bell DF, et al. Electromyographic and nerve conduction changes after tibial lengthening by the Ilizarov method. J Pediatr Orthop 1996;16:131.



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