Roger F. Widmann, Purushottam A. Gholve, and Arkady Blyakher
DEFINITION
Limb lengthening is a surgical procedure performed to lengthen a bone.
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
When a monoplanar fixator is used, lengthening is accomplished by distraction of the atraumatic corticotomy of the bone.9,18
ANATOMY
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.
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.
Consideration is given to lengthening of the surrounding soft tissues, which include the muscle tendon unit, neurovascular bundle, and skin.11
During bone lengthening, the tension in the surrounding soft tissue may predispose the lengthened segment to deformity12,19:
Femur: varus and procurvatum
Tibia: valgus and procurvatum
Humerus: varus and procurvatum
Radius and ulna: has a tendency to collapse in the interosseous space, which may cause synostosis
Metatarsal and metacarpal: apex dorsal angulation
During large lengthening, care is necessary to prevent subluxation or dislocation of the adjacent joint.19
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.
Tibial lengthening may cause knee or ankle subluxation and progressive equinus deformity of the foot.
Metatarsal and metacarpal lengthening can cause metatarsoor metacarpophalangeal subluxation.
All of these issues are considered during any lengthening procedure.
PATHOGENESIS
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
The new bone is formed mostly by intramembranous ossification and, to a lesser extent, through endochondral ossification.9,11
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.
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.
Gradually removing distraction and applying mild compression increases the rate of remodeling. Therefore, the regenerate becomes more rigid against bending loads.
To prevent any shortening of the segment from compression, preliminary over-distraction of up to 0.5 to 1 cm may be performed.
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
The natural history of the limb-length discrepancy (LLD) depends on the condition causing the LLD.16,22 A partial list of causes follows:
Congenital shortening: Proximal focal femoral deficiency, coxa vara, congenital short femur, fibula and tibia hemimelia, hemiatrophy
Congenital lengthening: Overgrowth syndromes such as hemihypertrophy, Beckwith-Weidemann syndrome, KlippelTrenaunay-Weber syndrome, and Parke-Weber syndrome
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.
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.
Paralysis: Poliomyelitis and cerebral palsy as well as other nervous system afflictions in children typically result in shortening on the more affected side.
Trauma: Direct injury to growth plate, posttraumatic bone loss or shortening, and overgrowth following femoral fracture
Miscellaneous: Slipped capital femoral epiphysis, LeggCalvé-Perthes disease
Upper extremity discrepancy or shortening usually does not cause major functional problems, but may result in significant cosmetic deformities.
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
In children, the LLD at maturity can be predicted in a variety of ways:
The arithmetic method13
The growth remaining method1
The Moseley straight line method15
The Paley multiplier technique20
Untreated LLD of more than 3 cm may result in pelvic obliquity, visual gait disturbance, short-legged gait, or structural/nonstructural scoliosis.22
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
The common symptoms at presentation are limp, compensatory gait mechanics, pelvic obliquity, and nonstructural scoliosis.
Physical findings depend on the etiologic factors.22
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.
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.
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.
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.
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
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
Plain radiographs are helpful to document the objective measurement of LLD (FIG 1).
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.
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.
Other radiographic techniques described in the literature include teleoroentgenogram, orthoroentgenogram, and the criterion standard: the slit scanogram and the CT scanogram.10,14
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
True shortening (eg, femoral or tibial)
Apparent shortening due to dislocated hip
Apparent shortening from contractures
Angular deformity causing apparent shortening
Overgrowth syndrome with both increased length and limb girth: hemihypertrophy
Congenital limb deficiency (beware knee joint instability)
NONOPERATIVE MANAGEMENT
Nonoperative management is based on the amount of discrepancy16 :
0 to 2 cm: no treatment
2 to 6 cm: shoe lift (option for epiphysiodesis or lengthening in this range)
More than 20 cm: extension prosthesis
SURGICAL MANAGEMENT
Preoperative Planning
Ilizarov Method
Accurate radiographic measurement of current discrepancy and calculation of projected LLD at maturity
Determination of which bony segment is affected
Assessment of compensatory mechanics used for walking: equinus gait, circumduction, vaulting, or combination21
Assessment of contractures: eg, extra- or intra-articular, bony
Assessment of associated deformities: eg, angulation, translation, and rotation
Long-leg standing radiographs in both planes help determine malalignment.
FIG 2 • Either a template (A) or an actual ring (B) may be used to measure the ring size.
Stability or laxity of joints (hip, knee, ankle) is determined clinically and radiographically.
Skin condition: eg, open defect, scar tissue
Planning for corticotomy level, for lengthening as well as for correction of associated deformity with appropriate room for wire or half-pin fixation.
Determine optimum frame configuration, with or without inclusion of the adjacent joint.
Details on ring size, half-pin, or K-wire placement
Single-stage lengthening of 10% to 15% of bone length is associated with fewer complications.2
Technical consideration.
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.
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.
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.
A template or an actual ring can be used to select the appropriate ring size (FIG 2).
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
True measures of current discrepancy and calculation of projected LLD
Compensation mechanisms used during walking: equinus gait, circumduction, vaulting
Assessment of contractures: extra- or intra-articular
Associated deformity: angulation, translation, and rotation
Stability or laxity of joints: eg, hip, knee, ankle
Skin condition: eg, open defect, scar tissue
Long-leg films showing hip, knee, and ankle for lower extremity; and similar long films for the upper extremity
Planning for corticotomy level; osteotomy level if needed for correction of associated deformity; and planning for points of fixation
Choose appropriate size arch, rods, rail, half-pin and/or K-wires.
Choose the appropriate size of the fixator (pediatric or adult)
Positioning
Lower extremity: Supine position on any radiolucent table (eg, Jackson table)
Upper extremity: Supine position with arm over a radiolucent table
Intraoperative fluoroscopy (for both the AP and lateral images)
For the Ilizarov method.
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).
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.
For monoplanar fixator use, place rolled sheet (as bumps) beneath the femur and tibia to create working space for application of the frame.
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
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.
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.
The wire is introduced from the side nearest the neurovascular bundle. This helps prevent inadvertent injury to the neurovascular structures.
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.
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).
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.
The wire is fixed to the ring without bending the wire. Bent wires will move the bony fragments on tensioning.
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
Hydroxyapatite-coated half-pins are recommended, because they achieve better fixation and are associated with lower rates of infection and loosening.3
The size of the half-pin should not exceed one-third the diameter of the bone segment being fixed.
Freehand techniqu.
Identify the optimal site for pin insertion.
Incise the skin over the insertion site, and then dissect down to the bone using a hemostat.
Now drill the bone (both cortices) through a protective drill sleeve.
The half-pin is introduced in the drilled track. The pin traverses only 1 to 2 mm through the far cortex, confirmed with fluoroscope.
The half-pin is attached to the ring or arch, which is positioned perpendicular to the bone segment.
If the half-pin insertion is not perpendicular to the bone, a post and half-pin fixation bolt are utilized.
Ring guide techniqu.
First the ring or arch is fixed perpendicular to the bone with a wire.
Depending on the optimal site for pin insertion, the half-pin fixation bolt or Rancho cube is attached to the ring.
Now the sleeve is introduced through the half-pin fixation bolt or cube, and the skin site is marked.
The skin is incised and dissected to the bone using a hemostat.
The sleeve is advanced further to contact the bone.
The drill is introduced through the sleeve, and the bone is drilled (both cortices).
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.
The half-pin fixation bolt or the cube is tightened over the pin.
Fibular Osteotomy and Anterior Compartment Fasciotomy
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.
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.
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).
A Hohmann or Bennett retractor then is placed around the exposed fibula to protect the surrounding soft tissue.
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.
An oblique osteotomy is used to have larger contact area between the two fragments.
The skin and subcutaneous tissues are closed without closing the underlying fascia.
Now the skin is incised over the tibial corticotomy site. The corticotomy site usually is the proximal metaphysis.
Prophylactic fasciotomy of the anterior compartment may be performed by releasing the anterior compartment fascia distally and proximally with a Metzenbaum scissor.
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.
Now a temporary suture is placed over the proximal tibial incision, deferring the corticotomy until later in the procedure.
Ilizarov Frame Application
For simple lengthening (without deformity), three rings (or two rings and one arch) are used.
Introduce a transverse proximal tibial wire perpendicular to the shaft and below the growth plate in children (TECH FIG 2, #1).
To avoid penetrating the joint capsule, the transverse wire should be no closer than 14 mm to the subchondral bone of the proximal tibia.
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.
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).
The biomechanical and anatomic axis of the tibia is the same in the absence of deformity.
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.
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.
Care is necessary to prevent damage to the peroneal nerve, which is in close proximity to the fibular neck.
The wire is then fixed and tensioned to the proximal ring.
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).
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.
It is important not to damage the tibial tubercle and proximal tibial physis while placing the half-pins or wires.
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.
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.
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).
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).
The connecting rods between the proximal and middle rings are then disconnected, and attention is directed to the corticotomy site.
Extra-periosteal dissection is performed at the proximal tibial metaphyseal osteotomy site.
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.
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.
The periosteum is not elevated circumferentially, in order to preserve the blood supply.
Corticotomy
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).
A 5-mm osteotome is advanced through the bone at the level of the drill holes (TECH FIG 3B).
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.
Finally, a wider osteotome is seated in the posterior cortex and twisted with a 14-mm wrench to break the posterior cortex.
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.
The rods between the proximal and distal blocks are reconnected as they were before the corticotomy, and the osteotomy is reduced.
The use of square nuts or clickers on the connecting rods allows future distraction.
Wound Closure
The skin is closed without closing the underlying fascia.
Check that all the nuts and bolts are tight.
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.
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.
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
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.
Deformities can be corrected using chronic deformity correction, the rings-first method, or the residual deformity method.
In the TSF, the proximal and distal blocks may or may not be connected preoperatively.
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.
The details of fibular osteotomy and anterior compartment fasciotomy are the same.
Mount the frame and secure with wires and half-pins.
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.
The corticotomy is reduced, and the struts are reconnected the way they were before the corticotomy (TECH FIG 4).
The deformity, frame, and mounting parameters are entered in the software program, which prescribes a lengthening/corrective program.
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.
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
The usual frame construct for simple femoral lengthening (without deformity) is composed of two rings and one arch.
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.
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.
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.
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.
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.
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).
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.
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.
Next, one or two half-pins are placed adjacent to the middle ring (TECH FIG 5A, pin 5).
The rods between the middle and distal rings are disconnected for corticotomy of the distal femoral metaphysis.
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.
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.
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.
The fragments are rotated back to the normal reduced position. This will decrease bleeding from the cut bony surfaces.
The rods are reconnected as before the corticotomy. Square nuts or clickers are used with these connecting rods to allow for controlled distraction.
The corticotomy site is closed. A check is done to tighten all nuts and bolts (TECH FIG 5B).
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.
During large lengthening and in presence of knee ligament laxity, one should consider extending the frame across the knee joint.
Taylor Spatial Frame
When using the TSF for femoral lengthening, the proximal and distal blocks may or may not be connected preoperatively.
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.
Mount the frame and secure with wires and half-pins.
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.
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.
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.
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
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.
Some monoplanar systems use arches or rings to achieve multiplanar fixation.
Advantages of monoplanar fixators22.
Greater patient comfort during femur and humerus lengthening
Less bulky frame
Simple construct
Disadvantages of monoplanar fixators 11,22:
Less rigid
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.
Not recommended for large lengthening (more than 5 cm)
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.
Rail size depends on the planned lengthening.
Techniques to increase frame stability include:
Increase number of half-pins
Increase diameter of the half-pins (pin diameter should not exceed a third of the bone diameter)
Greatest possible angle between half-pins (maximum, 90-degree angle)
Reduce distance between the bone and the external frame.
Increase the distance between half-pins.
Fixation as close to the corticotomy as possible.
Femoral Lengthening
For simple lengthening (without deformity), three-point fixation is required in each segment.
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.
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).
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).
Attach this half-pin to the clamp, which is connected to the rail (monolateral fixator).
At least one fingerbreadth of distance is maintained between the external frame and the lateral surface of the proximal thigh.
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).
This half-pin is also placed slightly anterior (not central) in the lateral femoral cortex (TECH FIG 7A, #2).
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.
Introduce two or more half-pins through the empty holes of the proximal clamp (TECH FIG 7B, #4).
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.
During femoral lengthening, soft tissue tension predisposes the femur to develop procurvatum deformity.
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).
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.
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.
Gloves are changed, and the skin at the level of the corticotomy is prepped again.
The femoral corticotomy is completed following the same principles discussed earlier.
After completion of the corticotomy, the frame is reapplied, maintaining the same distance between the clamps and the skin.
Fluoroscopy is used to confirm the slight recurvatum deformity. This recurvatum deformity compensates for the procurvatum tendency during lengthening of femur.
The skin is closed after repair of the tensor fascia.
The distraction device is connected to the clamps, and final tightening is performed.
Half-pins are dressed with Xeroform gauze and sponges.
Tibial Lengthening
For simple lengthenings (without deformity), two- or three-point fixation is required in each bony segment.
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.
Fibular osteotomy is performed first (as discussed previously).
A distal tibia-fibula transfixation screw is required to prevent distal tibia-fibula subluxation.
The skin is incised over the tibial corticotomy site, which usually is the proximal metaphysis.
Prophylactic fasciotomy of the anterior compartment is performed under direct vision before frame application.
Now a temporary suture is placed at the corticotomy skin incision, and corticotomy is performed after pin fixation is complete.
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.
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.
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.
The anterior aspect of the arch should be at least a fingerbreadth from the anterior cortex.
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).
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.
Two additional half-pins are placed distally through the distal clamp (TECH FIG 8, #4).
The distance of the clamps from the skin is marked on the half-pins. The frame is then removed in preparation for the corticotomy.
Gloves are changed, and the skin at the level of the proximal tibial metaphysis is prepared again.
The tibial corticotomy is completed following the same principle discussed earlier (TECH FIG 8, #5).
The frame is reapplied, maintaining the same distance between the clamps and the skin as measured before the corticotomy.
A properly executed procedure will not have any residual displacement at the corticotomy site.
The skin is closed, leaving the underlying fascia open.
The distraction device is connected to the clamps, and final tightening is performed.
Half-pins are dressed with Xeroform and sponges. A pressure dressing is applied over the corticotomy site.
The foot is placed in a plantigrade position.
POSTOPERATIVE CARE
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
The rate of distraction is 1 mm per day, distributed as 0.25 mm four times a day.6,11,18
Pin care is done with half-strength hydrogen peroxide and normal saline.
Showering is allowed 1 week after the surgery, with antibacterial soap.
Full weight bearing is encouraged as tolerated.
Physical therapy to maintain range of motion and prevent contractures:
Minimum: three times a week, and a home program is performed four times a day
During active lengthening, the patient is seen once per week.
Routine perioperative intravenous antibiotic prophylaxis is used.
OUTCOMES
Ilizarov Technique
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.
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.
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
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.
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.
Overall, good results were obtained. They concluded that larger lengthenings are possible, but the cost is increased time and complications.
COMPLICATIONS
Intraoperative
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
Monoplanar fixator
Incomplete corticotomy: Confirm complete corticotomy by externally rotating the distal fragment under fluoroscopic imaging.
Avoid neurovascular injury by placing half-pins through safe zones.5 Use a cross-sectional atlas.
Avoid paralyzing anesthetic agents during surgery, because they may mask nerve injury.5,19
Distraction Period
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.
Premature consolidation may be due to incomplete osteotomy, slow distraction rate, or incorrect direction of distraction.
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
Surgical nerve decompression occasionally is required to release the nerve from compressing structures.
Unplanned deformity may develop during bone lengthening. Appropriate frame modifications may be required to correct the deformity.12,19
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.
Iatrogenic deformity may develop during lengthening. Frame modifications may be required to correct the deformity and maintain a neutral mechanical axis.7,8
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
Pin tract infection (as described earlier).
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
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.
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.
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
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· 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.
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· 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.