Surgical Management of Blount Disease

 

 

 

 

DEFINITION

Blount disease, also known as idiopathic tibia vara and osteochondritis deformans tibiae, is characterized by abnormal growth of the proximal tibia physis with progressive varus deformity.

Blount disease is classified into three types based on age of clinical onset: infantile (0 to 3 years), juvenile (4 to 10 years), and adolescent (11 years and older).9

Infantile tibia vara is most prevalent in African American females and is associated with obesity, internal tibial torsion, and leg length discrepancy. Radiographs reveal a prominent medial metaphyseal beak, and the origin of the varus deformity is in the proximal tibia only. About 80% of cases are bilateral, and the potential for deformity is the greatest in this group.

Adolescent tibia vara is most prevalent in African American males with marked obesity, minimal internal tibial torsion, mild medial collateral ligament laxity, and mild leg length discrepancy. The site of the deformity is in the proximal tibia and sometimes in the distal femur as well. About 50% of cases are bilateral, and pain rather than deformity is more commonly the presenting complaint.

 

 

ANATOMY7

 

When evaluating patients with Blount disease, the normal development of the tibiofemoral angle in children must be considered.

 

The normal tibiofemoral angle in newborns is approximately 15 degrees varus. It decreases with growth, so that the tibiofemoral angle approaches 0 degrees around 18 months of age.

 

The tibiofemoral angle progresses to maximum valgus around 3 years of age and then decreases until adult physiologic valgus is achieved between 7 years of age and skeletal maturity.

 

One standard deviation of the anatomic tibiofemoral angle throughout growth is approximately 8 degrees.

 

PATHOGENESIS7

 

Blount disease is likely due to a combination of genetic factors and a cycle of increased stress across the medial physis, which leads to decreased medial endochondral ossification, further varus deformity, and, subsequently, further medial physeal stress. The medial physeal stress is aggravated by obesity and progressive genu varum.

 

Histopathologic studies of infantile and late-onset tibia vara are similar to those of patients with slipped capital femoral epiphysis. Findings include fissuring and clefts in the physis, fibrovascular and cartilaginous repair at the physeal-metaphyseal junction, foci of necrotic cartilage, and marked disorganization of the medial degenerative physeal zone.

 

These findings are consistent with an arrest of the normal endochondral growth mechanism.

 

NATURAL HISTORY

 

A varus alignment of the lower extremity places excess stress on the medial compartment of the knee. This stress places the knee at increased risk for arthritis.

 

The goal of intervention is to restore the normal anatomic orientation of the knee and ankle joints and to restore the normal mechanical axis of the leg.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The chief complaint in infantile tibia vara is usually deformity. In late-onset tibia vara, in contrast, knee pain is the primary complaint. The characteristics of the pain should be elicited.

 

Patients may exhibit a limp, with or without a leg length discrepancy. Observe the patient's gaiting, noting a limp or lateral thrust.

 

The mechanical axis of the lower leg is in varus. Genu recurvatum and internal tibial torsion may be present as well.

 

 

Inspect the sagittal profile for the presence of genu recurvatum; if present, it may be necessary to address it at the time of surgery.

 

 

The Q angle provides a clinical estimate of the anatomic tibiofemoral angle. Range of motion and collateral ligament laxity also should be assessed.

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Anteroposterior (AP) long-leg radiographs (which include the hips, knees, and ankles) should be obtained (FIG 1). The patella (not the foot) must be pointing forward.

 

 

 

 

FIG 1 • Orthoradiograph of patient with adolescent Blount disease.

 

 

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Infantile Blount disease has several characteristic radiographic findings.

 

 

To help differentiate infantile Blount disease from physiologic varus, the metaphyseal-diaphyseal angle is drawn. A metaphyseal-diaphyseal angle less than 10 degrees is consistent with physiologic varus, whereas an angle of more than 16 degrees is consistent with infantile Blount disease.

 

Acute angulation of the medial proximal tibia, medial beaking, fragmentation of the medial metaphysis, progressive varus, and unilateral involvement are consistent with infantile Blount disease.

 

 

Care must be taken that the radiographs are taken with the patella forward.

 

If tibial torsion is present, the feet must cross medially so that the patella is forward. The medial and lateral flares of the distal femurs will be equal if the patella is forward.

 

The proximal tibia is examined to determine the Langenskiöld stage.

 

 

Stage I: age younger than 3 years; medial and distal beaking of metaphysis with irregularity of entire metaphysis

 

Stage II: age 2.5 to 4 years; sharp anteromedial depression in ossification line of wedge-shaped medial metaphysis

 

 

Stage III: age 4 to 6 years; deepening of metaphyseal beak Stage IV: age 5 to 10 years; enlargement of epiphysis

 

 

Stage V: age 9 to 11 years; cleft in epiphysis, appearance of double epiphysis Stage VI: age 10 to 13 years; closure of medial proximal tibial physis

 

Late-onset Blount disease is characterized by less obvious changes in the proximal tibia.

 

 

These changes include wedging of the medial portion of the epiphysis, a mild posteromedial articular depression, a serpiginous curved physis of variable width, and mild or no fragmentation of the proximal medial metaphysis.

 

 

Radiographic analysis for deformity has been well described by Paley et al.4

 

 

The magnitude of the overall lower extremity malalignment can be determined by the anatomic tibiofemoral angle or the mechanical axis deviation. The anatomic tibiofemoral angle is the angle between the midshaft lines of the femur and the tibia. The mechanical axis deviation is the distance from the center of the knee to the mechanical axis line of the leg.

 

Analysis of the frontal plane deformity begins with the malalignment test.

 

 

The mechanical axis line is drawn from the center of the hip to the midpoint of the ankle plafond.

 

To identify whether the source of the deformity is the femur, the tibia, or both, joint orientation angles are measured.

 

The mechanical lateral distal femoral angle (mLDFA, normal value is 85 to 90 degrees) and medial proximal tibial angles (MPTA, normal value is 85 to 90 degrees) are measured to determine which is/are abnormal.

 

The joint line convergence angle is measured to determine whether the joint line is an additional source of deformity.

 

If the midpoints of the femur and tibia are over 3 mm apart, then frontal plane subluxation is a source of

deformity as well.

 

Finally, the joint lines are inspected for intra-articular sources of deformity.

 

 

The malorientation test is applied to the ankle and hip to determine whether these joints are oriented normally to the mechanical axis line.

 

 

Abnormal joint orientation angles indicate which joints are contributing to the deformity.

 

 

Sagittal plane radiographs are obtained and analyzed as appropriate. Leg lengths are measured in order to identify a leg length discrepancy.

 

The location of the deformity point, or center of rotation of angulation (CORA), is identified during preoperative planning.

 

DIFFERENTIAL DIAGNOSIS

Physiologic varus Pathologic causes

Rickets

Skeletal dysplasias

Focal fibrocartilaginous dysplasia Renal osteodystrophy Osteogenesis imperfecta

 

 

NONOPERATIVE MANAGEMENT

 

Nonoperative treatment with bracing may be indicated in patients with infantile Blount disease.

 

Bracing should be considered for varus deformity greater than 15 degrees in children older than 2 years of age with Langenskiöld stage I or II Blount disease.2

 

 

Bracing usually is not helpful in obese African American girls older than the age of 3 years. Nonoperative treatment with bracing is not successful in adolescent Blount disease.

SURGICAL MANAGEMENT

 

The surgical treatment of infantile Blount disease is distinct from that for adolescent Blount disease.

 

 

In patients with infantile Blount disease, the proximal tibial physis has several years of growth remaining. A proximal tibial osteotomy should be performed with the goal of correcting the anatomic tibiofemoral angle to within 5 degrees of neutral. In addition to the osteotomy, medial proximal tibial physeal bar resection, lateral proximal tibial hemiepiphysiodesis (guided growth plates), or tibial plateau elevation can be performed to improve the alignment of the physis and to allow for proper future growth.

 

 

Definitive surgery for infantile Blount disease should be done before 5 years of age because recurrence may develop if surgery is performed after this age.

 

In patients with adolescent Blount disease, treatment options are hemiepiphysiodesis and osteotomy. However, if insufficient growth remains for hemiepiphysiodesis to be effective, osteotomy is the best option

for correction of the deformity. Hemiepiphysiodesis of an already short limb may leave the patient with a significant limb length inequality. If such limb length inequality will require

 

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osteotomy for lengthening, the tibia vara should be corrected by osteotomy for angular and linear correction with external fixation.

 

The objective of the osteotomy is to obtain a neutral mechanical axis with a horizontal knee joint. Many different types of osteotomies have been described for the treatment of adolescent Blount disease, including opening and closing wedge osteotomies, dome osteotomies, and oblique osteotomies.

 

Following the osteotomy, fixation may be achieved with external or internal fixation. The use of cast immobilization alone has been associated with a loss of correction.

 

 

Internal fixation after osteotomy for Blount disease has been associated with problems. Loder et al3 reported poor results in patients treated with internal fixation and noted many were internally fixed in malposition, likely due to difficulty in assessing intraoperative alignment. Crossed K-wires have been associated with a loss of fixation. The use of plates has been associated with stress shielding, delayed and nonunion, and hardware breakage, and requires a second surgical procedure to remove the implant.

 

External fixation allows for acute or gradual correction and for later adjustments as clinically and radiographically indicated. In addition, external fixation allows for correction of the coexistent leg length

discrepancy. Price et al5 reported the successful use of dynamic external fixation to stabilize osteotomies for tibia vara without supplemental casting. Monolateral, hybrid, or circular external fixators may be used.

 

In this chapter, we describe the technique for correction of adolescent Blount's disease via osteotomy and external fixation. The external fixator used in this technique is the EBI Multi-Axial Correction System (EBI, Parsippany, NJ). This fixator allows gradual or acute correction of deformity in two planes of angulation, two planes of translation, rotation, and lengthening without the disadvantages of a ring fixator.

 

Preoperative Planning1, 6

 

Standing lower extremity alignment radiographs are obtained (see FIG 1). The location of the CORA in the tibia in Blount disease cannot be determined by simply drawing two shaft lines because the deformity is metaphyseal or juxta-articular.

 

 

If the mechanical axis method of preoperative planning is used, the mechanical axis of the proximal tibia may be estimated by extending the femoral mechanical axis (if mLDFA is normal) or by drawing the MPTA of the contralateral MPTA (if normal) or the population normal value (87 degrees).

 

The distal tibia mechanical axis of the tibia is represented by a line that begins at the center of the ankle and extends parallel to the shaft. If the distal tibia has insufficient shaft length on which to base the line, the line is drawn using the contralateral lateral distal tibia angle (LDTA) or the population normal value (90 degrees).

 

The intersection of these lines is the CORA.

 

If the femur also was found to be a source of deformity during the alignment test, then CORA in the femur is identified as described by Paley et al.4

 

The technique described in this chapter is for adolescent Blount disease with deformity located solely in the proximal tibia metaphysis not amenable to guided growth because of age or Langenskiöld classification.

 

The external fixator used in this technique can be applied in three different locations with respect to the

CORA: CORA-centric, CORA-perpendicular, and CORA-proximal.

 

 

The CORA-centric method places the fixator hinge directly over the CORA and minimizes unintended translation.

 

The CORA-perpendicular application places the fixator hinge on the bisector of the deformity, which, when placed on the convex side of the deformity, produces simultaneous lengthening during angular correction. CORA-perpendicular application is advisable only when lengthening is required.

 

The CORA-proximal application places the hinge near the CORA. This application is used when the hinge cannot be placed on the CORA or the bisector and relies on the flexibility of the hinges and translation screws to correct secondary translation.

 

Positioning

 

The patient is placed supine on a radiolucent table. The use of an OSI table with Jackson imaging top (Mizuho Osi, Orthopaedic Systems, Inc., Union City, CA) permits fluoroscopic images to be taken with minimal difficulty. A bump may be placed under the ipsilateral buttock.

 

A tourniquet typically is not used because the thigh circumference of patients with Blount disease often is too large for a tourniquet to be used effectively and can possibly cause increased bleeding from venous tourniquet.

 

The entire lower extremity is prepared and draped. The toes are left uncovered so that muscle contraction caused by inadvertent nerve irritation during pin placement is visible.

 

Approach

 

The procedure is divided into fibular osteotomy, external fixator application, proximal tibial osteotomy, and completion of the surgery. Prophylactic fasciotomies are performed during exposure for the fibular and tibial osteotomies.

 

The lateral approach to the fibula is used for the fibular osteotomy and lateral compartment fasciotomy. Small medial and lateral incisions are made for the tibial osteotomy, and the anterior compartment is released from the lateral incision.

 

The surgeon must have thorough knowledge of the cross-sectional anatomy of the lower leg and the half-pin positions for safety.

 

 

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TECHNIQUES

• Surgical Management of Blount Disease

Fibula Osteotomy

A longitudinal incision is made just lateral to the fibula at the intersection of the middle and distal thirds of the lower leg. Dissection is carried down to the deep fascia.

A prophylactic subcutaneous lateral compartment fasciotomy is then performed. Care is taken to avoid injury to the superficial peroneal nerve and its branches.

The peroneus longus and peroneus brevis muscles are visualized. These muscles are then retracted either anteriorly or posteriorly (depending on exposure), and the fibula is visualized. Subperiosteal exposure of the fibula is then developed using a Cobb elevator or right angle, and retractors are placed around the fibula to protect the soft tissues.

 

 

The tibia is corrected in the direction of valgus. Because the fibula is lateral to the tibia, correction will push the fibula proximally.

 

To prevent damage to the peroneal nerve at the proximal fibula, a 1-cm segment of bone is removed from the fibula. Oblique cuts in the fibula are made with the most proximal end aspect of the cut in the posterior edge of the fibula (TECH FIG 1). The cut is made carefully so that the saw is not inadvertently pushed past the posteromedial edge of the fibula with resultant injury to the peroneal artery.

 

Wound closure is performed at this point because this is easier to do before the external fixator is applied.

External Fixator Application

 

The external fixator can be assembled before the procedure begins or just before application.

 

A rotating arc is selected that will allow for correction of coexisting rotational deformity or rotation inadvertently caused by misplacement of the fixator.

 

The ring size (130, 150, 180, or 220 mm) is based on the leg circumference at the level of the proximal tibia.

 

The arc should match the curvature of the anterior proximal tibia with two fingerbreadths between the ring and the leg.

 

The adult multiaxial correction (MAC) central component is then attached to the center of the rotating ring such that the primary arc on the MAC central component is facing anteriorly.

 

The MAC female adapter is placed at the other end of the MAC central component, and the telescoping arm is attached to the female adapter.

 

The primary hinge of the MAC central component is adjusted so that the fixator matches the angular deformity of the tibia.

 

 

 

TECH FIG 1 • An oblique 1-cm wedge is removed from the fibula.

 

 

In the example illustrated in this section, the MAC is applied in the CORA-centric location.

 

The CORA, as identified during preoperative planning, is localized under fluoroscopy, and an appropriately sized guide pin (supplied with the MAC) is placed from anterior to posterior into the CORA (TECH FIG 2A).

 

The guidewire should be perpendicular to the tibial diaphysis (in the true deformity axis). Although placement of the guidewire exactly into the CORA can be difficult, the multiangular or translation and rotation ability of the MAC device can correct any secondary deformity due to misplacement of the MAC

off the CORA.

 

Sterile Webril padding (Kendall Co., Mansfield, MA) is then placed around the K-wire to serve as a two-fingerbreadth spacer (TECH FIG 2B).

 

The centering hole of the primary hinge of the MAC fixator is placed over the K-wire so that the fixator rests on top of the spacer (TECH FIG 2C).

 

Universal screw carriages are locked onto the rotation arc and used as guides for placement of two or three proximal screws.

 

Three proximal half-pins are then placed in the safe zones of the proximal tibia.

 

At least one pin is placed from anteromedial to posterolateral and one is placed from anterolateral to posteromedial.

 

The pins are placed distal to the physis (which may be open).

 

 

Care should be taken not to place the screws so close to the MAC device as to block rotation. Holes are predrilled bicortically with the 4.8-mm drill bit and 6.0-mm pins are placed.

 

We prefer to use hydroxyapatite-coated pins to reduce the risk of loosening and, therefore, infection. Pin size typically is around 60-mm thread length and 160 to 180 mm overall length (TECH FIG 2D).

 

The size of the bone screw depends on the size of the patient, the tibia at the level of screw insertion, and the size of the arc chosen.

 

The carriages are tightened after the pins are placed. The MAC is then adjusted to the tibial deformity, ensuring that the distal bone screw block is parallel to the distal tibial diaphysis at the medial subcutaneous face of the tibia (TECH FIG 2E).

 

Three distal half-pins are placed through the telescoping arm in the midshaft of the tibia (TECH FIG 2F). Pin size typically is 120 mm overall and 40 mm of thread length.

 

If the MAC is aligned such that the pins placed through the telescoping arm will not go through the tibia, the CORA pin should be removed and the device rotated, angulated, or translated so that the pins are aligned. (If this is done, rotation must be corrected first before the remainder of the deformity is corrected to realign the primary hinge to the bone deformity.)

 

At this point, all the pins (bone screws) have been inserted.

Tibial Osteotomy

 

Using the MAC external fixator, placing the guide pin at the CORA allows deformity correction to occur at the CORA. The osteotomy does not have to be made at the CORA. It should be performed just below the insertion of the tibial tubercle, decreasing the risk of damage to the nearby physis and joint line.

Placement of the osteotomy below the tibial tubercle will also avoid pulling the patella distally during distraction.

 

The tibial osteotomy may be performed using one of several different techniques. Our preference is to perform the osteotomy

 

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through small transverse anteromedial and anterolateral incisions with a Gigli saw passed subperiosteally.

 

 

 

TECH FIG 2 • A. Fluoroscopy is used to localize the CORA (which was identified during preoperative planning). B. Sterile web roll padding is placed over the guidewire to serve as a spacer. C. The MAC external fixator is placed on top of the spacer. D. Two or three bone screws are placed in the proximal tibia. E. The length and angulation of the MAC external fixator are adjusted to match the deformity. F. Three bone screws are placed in the tibial shaft.

 

 

 

Fluoroscopy is used to identify the metaphyseal-diaphyseal junction where the osteotomy will be made. The guide pin is removed.

 

Two 2-cm transverse incisions are made, one on the medial and one on the lateral aspects of the anterior tibia at the level for the osteotomy. The incision is made transversely to avoid skin injury from the Gigli saw.

 

From the lateral incision, dissection is carried down to the fascia of the anterior compartment.

 

A prophylactic subcutaneous release of the anterior compartment is then performed through this incision.

 

 

 

TECH FIG 3 • A. Subperiosteal exposure of the tibia is developed at the level of the osteotomy. B.

Umbilical tape is held taut by a right angle clamp. C. The umbilical tape is pulled posterior to the tibia.

 

 

A hemostat is used to expose the tibia subperiosteally at the level of the osteotomy (TECH FIG 3A).

 

A no. 5 suture is then held taut by a right angle clamp and passed, subperiosteally, around the back of the tibia (TECH FIG 3B). A hemostat is placed posterior to the tibia from the opposite side, and the suture is grasped and pulled out the opposite side of the leg (TECH FIG 3C).

 

To verify that the saw has not been placed around the anterior or posterior tibial arteries, the ends of the suture are pulled taut while palpating the pedal pulses for occlusion.

 

 

The Gigli saw is then tied to the suture to pass the saw around the back of the tibia. The osteotomy is then performed with the Gigli saw.

 

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Care is taken to avoid injury to the skin.

 

Fluoroscopy is used to verify the completion of the osteotomy and alignment of the proximal and distal fragments with the external fixator.

Completion of Surgery

 

The lengthening device is then inserted onto the telescoping arm and turned such that it slides into the telescoping arm (TECH FIG 4A). Both screws of the lengthening device are then tightened.

 

All screws of the external fixator are then given their final tightening.

 

All wounds are closed, and a sterile dressing is applied (TECH FIG 4B).

 

Acute correction typically is not performed if there is risk of stretching neurovascular tissues.

 

During the first postoperative week, the patient learns to walk with crutches, 10 pounds partial weight bearing.

 

On the eighth day, the patient is taught to lengthen through the compression distraction mechanism at a rate of one 90-degree turn of the Allen wrench four times a day. This will cause lengthening of 1 mm per day.

 

 

 

TECH FIG 4 • A. The lengthening device is applied. B. A sterile dressing is applied. C,D. Radiographs are taken to verify that there is distraction at the osteotomy site prior to correcting angulation. E,F. Correction is performed until the angulation has been rectified.

 

 

On the 14th day, a radiograph should show that the ends of the osteotomized tibia are separated by a distance of about 7 mm (TECH FIG 4C,D).

 

Angular correction can now begin. The patient is taught to place the Allen wrench into the primary angulation screw and turn 90 degrees in the direction for angular correction. This 90-degree turn will correct 1 degree of angular deformity and can comfortably be performed four times a day for a correction of about 4 degrees per day until the deformity is corrected (TECH FIG 4E,F).

 

Long radiographs are then taken to assess the correction.

 

Secondary deformity (flexion or extension) can be corrected through the secondary hinges, translation screws (one 360-degree turn translates 1 mm), lengthening screws, and the rotation arc (one 90-degree turn corrects 1 degree of rotation).

 

Once the deformity is corrected, all screws and locks on the MAC device are secured. The device can be

safely removed after passage of at least 1 month per centimeter of lengthening and a minimum of about 3

months.

Radiographs should also demonstrate healing of at least three cortices on each of the AP and lateral views before removal of the fixator.

Training and experience with external fixation and deformity correction is always advised.

 

 

Indications

• A correct diagnosis of Blount disease must be made before treatment is

initiated. Treatment alternatives, including hemiepiphysiodesis (if there is sufficient growth remaining), must be discussed with the patient and family.

Deformity

planning

• Radiographs must be evaluated carefully and systematically so that the

location of the CORA and coexistent deformities of the femur or sagittal plane are identified.

Neurovascular ▪ All half-pins must be placed into safe zones of the leg to avoid inadvertent

injury neurovascular injury.

• Careful neurovascular examinations must be performed postoperatively.

Postoperative

care

• Patients must be followed closely during correction so that malalignment does

not occur. Pin site infections must be recognized and treated appropriately.

 

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PEARLS AND PITFALLS

 

 

POSTOPERATIVE CARE

 

Patients are admitted to the hospital and monitored closely for signs and symptoms of neurovascular injury and compartment syndrome for 1 to 3 days.

 

Patients initially are allowed touchdown weight bearing only. Range-of-motion exercises are begun immediately.

 

Pin care is begun on postoperative day 2. Patients are instructed on the signs and symptoms of pin site infections.

 

No adjustments or corrections are made to the external fixator for the first 7 days. A 7-day latency allows fracture callus to develop at the site of the osteotomy. Then, the correction phase is begun.

 

The correction phase begins with lengthening the leg by 7 to 8 mm at a rate of 1 mm per day (0.25 mm four times per day) to separate the bone ends. Angulation is then corrected. The patient is evaluated clinically and radiographically to follow correction of the mechanical axis. Scanograms can then be obtained to determine leg length inequality, which can be corrected by lengthening with the fixator. The rotational deformity (internal tibial torsion) is corrected last. Placing white adhesive tape with arrows onto the device helps patients remember how to turn the screws appropriately for angular, linear, and rotational correction.

 

Weight bearing is increased during the consolidation period. The consolidation period is approximately twice

the correction period. Most patients treated with this technique for adolescent Blount disease will have the external fixator on for 3 to 4 months. They can walk with crutches initially and progress to full weight bearing as the osteotomy heals. They can shower within 3 days of application of the fixator.

 

When radiographs show that the osteotomy and distraction gap have healed, the external fixator is removed. Removal can be done in the office or in the operating room. Considerable torque is required to remove hydroxyapatite pins and this must be done in the operating room with adequate sedation and analgesia.

 

OUTCOMES

Because adolescent Blount disease is relatively uncommon, there are few outcome studies in the literature.

Price et al5 reported on the treatment of 31 tibiae in 23 patients with dynamic external fixation. All osteotomies healed. There was an average correction of 20 degrees, and no postoperative loss of correction occurred.

 

 

COMPLICATIONS

High complication rates have been reported for proximal tibial osteotomies.

 

Steel et al8 reported a 20% rate of neurologic complications in 46 tibial osteotomies. The neurologic complications are related to the location of the osteotomy, which must be done in the metaphysis to avoid damaging the proximal tibial epiphysis.

Deformity correction at this level can stretch or compress the anterior tibial artery because of its proximity to the tibia at that level. Although arterial stretch or compression is more common than laceration or edema in anterior compartment following correction, prophylactic fasciotomies of the anterior and lateral compartments are still indicated to decrease the risk of neurovascular complications.

Other complications include delayed union and nonunion.

 

 

ACKNOWLEDGMENT

 

With thanks to Dr. Eric D. Shirley,† the author of this chapter in the first edition.

 

REFERENCES

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5. Price CT, Scott DS, Greenberg DA. Dynamic axial external fixation in the surgical treatment of tibia vara. J Pediatr Orthop 1995;15:236-243.

    

    

6. Salenius P, Vankka E. The development of the tibiofemoral angle in children. J Bone Joint Surg Am 1975;57(2):259-261.

    

    

7. Schoenecker PL, Meade WC, Pierron RL, et al. Blount's disease: a retrospective review and recommendations for treatment. J Pediatr Orthop 1985;5:181-186.

    

    

8. Steel HH, Sandrow RE, Sullivan PD. Complications of tibial osteotomy in children for genu varum or valgum. Evidence that neurological changes are due to ischemia. J Bone Joint Surg Am 1971;53(8):1629-1635.

    

    

9. Thompson GH, Carter JR. Late-onset tibia vara (Blount's disease), Current concepts. Clin Orthop Relat Res 1990;(255):24-35.