December 2017

12/18/2017 | BY Megan Young, MD, Children’s National Medical Center, Washington, DC

Pediatric Lower Extremity Disorders

Pediatric Lower Extremity Disorders

Topics covered in this section:

  • Genu varum
    • Physiologic
    • Infantile tibia vara
    • Adolescent tibia vara
  • Genu valgum
  • Tibia torsion
  • Tibia bowing
    • Anterolateral bow and congenital tibia dysplasia
    • Congenital posteromedial bow


Genu Varum

1. Physiologic genu varum
 
Genu varum, or lower extremity bowing, defined by a tibiofemoral angle of at least 10 degrees of varus, is normal during infancy and is more pronounced after standing age.  The natural history of normal lower extremity alignment progression shows maximum varus between 6-12 months, neutral alignment by 18-24 months, maximum valgus at 4 years, and a mean of 6 degrees of valgus by age 11.  It is important to note that variations may be observed.
 
 
Clinical examination shows symmetric generalized bowing of the distal femur and proximal tibia.  Radiographs are not necessary to diagnose physiologic genu varum but when obtained may show apparent delayed ossification of the medial distal femur and proximal tibia epiphysis, a flare of the distal femur metaphysis, and normal physes.  Persistent or asymmetric deformity after the age of 2 are the main indications for radiographic evaluation with a standing lower extremity alignment film from hips to ankles with the patella facing forward.
 
Parents can be reassured that physiologic genu varum spontaneously improves by the age of 2, although some children may exhibit slower resolution to neutral alignment.  Formal observation for expected self-correction is appropriate treatment.
 
Physiologic genu varum does not generally cause pain or functional difficulties.  Differentiating physiologic from true pathologic genu varum is important as the latter may lead to progressive varus deformity if untreated.  Diagnoses to consider if the genu varum fails to resolve include infantile tibia vara, traumatic or infectious physeal disturbance, metabolic bone diseases (rickets), skeletal dysplasias, and rarely focal fibrocartilaginous dysplasia.
  
Recommended Readings:
  • Heath, C. and Staheli, L.Normal limits of knee angle in white children-genu varum and genu valgum.J Ped Ortho.1993;13(2):259-262.
  • Salenius, P. and Vankka, E.The development of the tibiofemoral angle in children.J Bone Joint Surg Am.1975;57(2):259-261.
     

2. Infantile tibia vara
 
When present before age 3, a growth disturbance of the medial proximal tibia epiphysis and physis leading to persistent or progressive varus deformity defines infantile tibia vara or “Blount” disease.  No definitive genetic link has been identified.  The etiology is likely multifactorial.  The relationship between obesity and risk of Blount disease has been studied with a higher BMI (>22) observed in toddlers who develop pathologic tibia vara.  The physiologic basis of the disease supports a developmental as opposed to a congenital condition.  Supported by the Hueter-Volkmann principle, compressive forces across the medial tibial plateau in an overweight toddler with varus deformity can sufficiently retard normal physeal growth.
 
Clinically the child with infantile tibia vara appears similar to a child with physiologic genu varum with lower leg bowing and frequently a component of internal tibia torsion.  Not uncommonly the child with tibia vara exceeds the 95th percentile for weight.  A “varus thrust” or sudden lateral knee movement secondary to varus instability observed during the stance phase of gait should raise suspicion of nonphysiologic tibia vara.  An AP radiograph of bilateral lower extremities standing with the patella facing forward aids in establishing the diagnosis.  Assuming presence of internal tibia torsion, if the image is obtained with the feet pointing forward an externally rotated view of the knee impairs ability to accurately evaluate the classic radiographic changes consistent with Blount disease.  The abnormalities of the proximal tibia typically appear between 18-24 months of age and include 1) abrupt varus angulation of the medial proximal tibia metaphysis, 2) beaking of the metaphysis, irregularity and widening of the medial physis, 3) downward sloping epiphysis, and 4) lateral subluxation of the proximal tibia.  The tibial metaphyseal-diaphyseal angle (MDA) measures the intersection of a line connecting the prominent medial portion of the proximal metaphysis with the prominent point on the lateral proximal tibia metaphysis and the perpendicular line to the tibia diaphysis.  An MDA greater than 11 degrees has been shown in some studies to identify patients at risk for developing radiographic Blount lesion, although the accuracy of the measurement is largely affected by any limb malrotation during the radiographic exam.  LangenskiÖld described six radiographic stages of the disease with progressive severity of metaphyseal and epiphyseal changes with advancing age.  Significant physeal damage behaving as a medial physeal arrest occurs by stage IV followed by progressive epiphyseal deformity by stage V and ultimately complete bony bridge or physeal bar formation with variable joint surface abnormality by stage VI.  MRI is not necessary to establish the diagnosis but can be a useful tool in more advanced stages of the disease to fully assess the extent of the ossified and cartilaginous epiphysis, presence of any “true” intraarticular deformity, and location of the physeal bridge.  
 
Treatment of infantile tibia vara is recommended to avoid progressive deformity and potentially irreversible injury to the medial proximal tibia physis.  The type of treatment depends on the patient age and more importantly the radiographic stage of the disease at presentation.  Bracing  with an anti-varus or medial offloader may be successful in resolving deformity in infantile tibia vara when prescribed for patients younger than age 3 with Langenskiold stage I or II disease, especially in unilateral cases.  The type of brace, recommended wear per 24-hour period, and duration of use is variable in the literature.  Growth modulation with a tension band plate that spans the lateral proximal tibia physis with the purpose of temporarily tethering growth in that area is a surgical option for younger patients with Langenskiold stage I or II disease, with an 89% success rate reported.  It is noteworthy to point out that “guided growth” surgery will not correct the associated internal tibia torsion.  Questions of optimal patient age to apply this technique, timing of implant removal (neutral vs overcorrected valgus alignment), and likelihood of rebound deformity remain unanswered.   Proximal tibia (below the tubercle) and fibula osteotomies to overcorrect the varus deformity and laterally translate and externally rotate the distal segment represent the “gold standard” surgical treatment for Langenskiold stages I-III disease.  Early intervention before the age of 4 may reduce the risk of permanent physeal damage and need for repeat osteotomy due to recurrence.  Treatment options become more individualized beyond Langenskiold stage IV and greater lesions.  Medial epiphysiolysis or physeal bar resection combined with osteotomy is recommended to restore medial proximal tibia growth and reduce the risk of relapse, most effectively performed with >80% successful prevention of recurrence in patients less than 7.  Realignment procedures and simultaneous completion epiphyseodesis prevents recurrent deformity but produces a limb length inequality that will need to be subsequently addressed if more than 2 years of growth remaining.  In children greater than age 10 years with advanced Langenskiold stage VI disease and joint incongruity, intraarticular medial plateau elevation osteotomy with a separate proximal tibia osteotomy to correct the mechanical axis may be indicated.  
 

The natural history of untreated infantile tibia vara is progressive deformity, although spontaneous resolution has been observed in milder forms.  The longterm consequence is premature degenerative joint changes.  Corrective surgery by the age of 4 is more likely to produce a good outcome and reduce the risk of recurrence, but proximal tibia osteotomy is not without complication in a growing child.  Growth arrest of the tibia tubercle leading to recurvatum deformity can be prevented by choosing an osteotomy level of the tibia distal to the tubercle.  The optimal osteotomy location places the popliteal artery (posteriorly) and the anterior tibia artery (passing through the interosseous membrane) at risk.  Compartment syndrome may develop postoperatively warranting careful observation and consideration of prophylactic anterior fasciotomy at the time of the index procedure.  Direct or indirect peroneal nerve injury from manipulation, entrapment within the fascia planes or traction may occur.   Recurrence may be a result of incomplete initial correction or failure to recognize and treat the partial medial physeal arrest.  While growth modulation techniques present an attractive “less invasive” alternative to correct the varus in early stage disease, the surgery is not entirely benign with potential for implant breakage, iatrogenic injury to the lateral physis or perichondrial ring, failure to correct the deformity and recurrence.

Recommended Readings:
  • Birch, J.Blount Disease.J Am Acad Ortho Surg 2013;21:408-414.
  • Andrade, N and Johnston, C.Epiphysiolysis in Severe Infantile Tibia Vara.Journal of Ped Ortho 2006;26:652-658.
  • Scott, A.Treatment of infantile Blount disease with lateral tension band plating.J Ped Ortho 2012;32:29-34.
     

3. Adolescent tibia vara
 
Adolescent tibia vara is a distinctly different disorder that onsets later after age 8, typically coinciding with the growth spurt.  Progressive deformity develops as a result of chronic growth suppression from compressive forces on the medial physis.  Obesity is linked to adolescent tibia vara.  It remains unclear if other factors (familial predisposition, persistent mild physiologic varus, or vitamin D deficiency) have an additive effect on a physis susceptible to injury from mechanical loads in an obese patient.  The predominance of male patients is not fully explained in the literature.
 
The classic patient is obese, largely exceeding the 95th percentile of weight, with varus deformity of the tibia, varying amounts of associated internal tibia torsion with or without overload symptoms of medial or anteromedial joint pain.  No radiographic classification exists for adolescent Blount disease.  A standing radiograph of bilateral lower extremities from hip to ankle shows medial mechanical axis deviation with proximal tibia varus and widening of the medial physis.  Joint depression/epiphyseal distortion and metaphyseal beaking characteristic of the infantile form are not present in adolescent Blount’s disease.  Measurable varus deformity of the distal femur is frequently present with “traction” widening of the lateral distal femur physis. 
 
Surgical treatment with restoration of a neutral mechanical axis (and avoidance of “overcorrection”) is recommended.  Lateral proximal tibia hemiepiphyseodesis is a minimally invasive technique to correct alignment in patients with at least 2 years of growth remaining, but success rates are less predictable.  Higher failure has been observed in patients older than 14, with a BMI >45, and more severe varus deformity.   Addition of a proximal fibula epiphyseodesis should be considered if 2cm of overgrowth is expected to avoid symptoms.  Tension band plates are an alternative method to complete hemiepiphyseal ablation to guide the growth of the extremity.  The technique should incorporate a single 4-hole plate, noncannulated screws and stainless steel implants to reduce mechanical failures in obese patients.  Proximal tibia osteotomy with rigid fixation is the mainstay of treatment to acutely achieve a neutral mechanical alignment in this patient population.  If concurrent distal femur varus exceeds 5 degrees beyond normal, combined distal femur osteotomy is recommended.  Gradual deformity correction after osteotomy with external fixation affords the advantage of adjustability to fine tune the mechanical alignment and add length if associated shortening of the limb is present.
 
The goals of treatment are to correct the mechanical axis, restore physeal growth (if growth remains) and reduce the risk of medial compartment degenerative arthritis, although longterm studies correlating radiographic deformity parameters with clinical outcome scores and pain are lacking.  Lateral proximal tibia hemiepiphyseodesis or tension band plating offer the least morbid approaches to correct alignment in skeletally immature patients.  While successful restoration of the mechanical axis is less predictable with this method, it does not preclude corrective osteotomy in the future.  Complications known to occur following acute proximal tibia osteotomy include nerve palsies, compartment syndrome, delayed/nonunion, loss of fixation, inaccurate intraoperative deformity correction.  Gradual deformity correction with external fixation devices may allow for more accurate postoperative deformity correction at the expense of other possible disadvantages such as pin tract infections, generalized discomfort associated with external fixators, nerve injury, muscle weakness, and prolonged treatment course.
 
Recommended Readings:
  • Birch, J.Blount Disease.J Am Acad Ortho Surg 2013;21:408-414.
  • McIntosh, A., Hanson, C., and Rathjen, K.Treatment of Adolescent Tibia Vara with Hemiepiphyseodesis: Risk Factors for Failure.J Bone Joint Surg Am 2009;91:2873-2879.
  • Gordon, E. et al.Comprehensive Treatment of Late Onset Tibia Vara.J Bone Joint Surg Am 2005;87A(7):1561-1570.
     
 

Genu valgum

Physiologic genu valgum is normal in a child between 2 and 8 years of age, generally reaching maximum deformity between the ages of 2 and 4.  The normal adult mechanical alignment averages 6 degrees of valgus achieved by age 11.  Symmetric residual valgus deformity detected after age 8 is deemed idiopathic in the absence of known history of trauma, infection, metabolic disturbance, or short stature.  Post-traumatic valgus deformity of the tibia following a nondisplaced metaphyseal fracture, known commonly as the “Cozen” phenomenon, presumably develops secondary to soft tissue interposition at the fracture site, growth stimulation of the medial physis or tether of the lateral physis by the intact fibula.  Differential diagnosis of nonidiopathic genu valgum includes traumatic or infectious partial physeal arrest, metabolic disorders (rickets), skeletal dysplasias, and tumorlike conditions (Ollier disease, multiple hereditary exostosis). 
 
Clinical examination shows symmetric valgus alignment at the knees.  Assessment of the lower extremities with the patella facing forward is important as femoral anteversion and retroversion may accentuate the apparent valgus malalignment.  Patients with excessive valgus may complain of difficulty walking or running, generalized anterior knee pain, or patellar instability.  Radiographs are not indicated in the young child with suspected physiologic genu valgum.  An AP radiograph of bilateral lower extremities hip to ankle standing is appropriate if the history portends to a pathologic etiology, significant asymmetry is detected, or the child is older than age 8.  Dedicated knee films or 3-dimensional imaging may be useful if partial physeal arrest is the cause.   
 
Young patients with suspected physiologic valgus deformity can be observed for expected resolution.  Similarly, treatment of posttraumatic tibia valga following metaphyseal fractures is observation for spontaneous improvement over a period of several years.  In cases of extreme deformity or symptoms, transient hemiepiphyseodesis is the treatment of choice performed within the first few years after fracture.  For patients older than age 8 with persistent valgus, corrective surgery may be indicated for significant malalignment, difficulty ambulating, knee pain, or patella instability.  The least invasive approach in a skeletally immature patient is timed hemiepiphyseodesis of the medial physis or transient hemiepiphyseodesis with a reversible method (percutaneous screws or tension band plates).  For patients nearing skeletal maturity, osteotomy with acute or gradual correction is appropriate.  Osteotomy remains a viable option in young patients with metabolic disorders or skeletal dysplasias where the physis lacks normal function and may not respond to guided growth techniques like tension band plates. 
Valgus deformity may contribute to gait abnormality, anterior knee pain, patella maltracking or instability, and future lateral compartment arthritis.  Hemiepiphyseodesis procedures risk “undercorrection” if near skeletal maturity or “overcorrection” if growth remains.  Once the mechanical axis is restored following medial hemiepiphyseodesis, the lateral hemiepiphyseodesis should be completed to avoid overcorrection.  Following a transient hemiepiphyseodesis technique, the implant should be removed.  A few degrees of rebound deformity may be expected after removal of tension band plates.  The peroneal nerve is tensioned with varus-producing osteotomies and susceptible to injury with acute correction.  Compartment syndrome is a known complication after proximal tibia osteotomies.
 
Recommended Readings:
  • Tuten, H. et al.Posttraumtic tibia valga in children. A long-term follow-up note. J Bone Joint Surg Am 1999;81:799-810.
  • Park, H. et al.Hemiepiphyseodesis for idiopathic genu valgum percutaneous transphyseal screw versus tension band plate.J Ped Ortho 2016.



Tibia Torsion

Deviations from normal rotational variations of the tibia may be internal (medially deviated) or external (laterally deviated).  The foot is medially rotated in normal fetal development, and the medial malleolus lies posterior with respect to the lateral malleolus.  The lateral rotation increases with age such that the medial malleolus is parallel to the lateral malleolus at birth and anterior to the lateral malleolus after walking age.  The average bimalleolar axis is 15 degrees of external rotation at maturity.  Intrauterine positioning may affect the amount of torsion present at birth in one direction or the other.  A wide degree of variability exists in the lower extremity rotational profile of toddlers and young children, most considered normal physiologic variants. 
 
Tibia torsion is a common source of “intoeing” and “outtoeing” detected in toddlers less that 4 years of age, but a complete evaluation of the rotational profile of a child requires assessment of the foot, tibia, and femur.  The foot progression angle during gait refers to the angle between the axis of the foot and line of direction of gait. 
 
Internal tibia torsion
Intoeing denotes an internal foot progression angle (FPA).  When the patellae face forward, an internal FPA may be secondary to a medially deviated forefoot (metatarsus adductus) or internal tibia torsion.  Tibia torsion is estimated with the child in the prone position with the hips extended and knees and ankles flexed to 90 degrees.  The angle created by the intersection of the thigh and foot axis is measured. Alternatively, the bimalleolar axis can be measured with the patient in the same position.  The angle formed between the axis extending from the medial to the lateral malleolus and the perpendicular to the thigh is normally 0-20 degrees external.   A medially rotated foot suggests internal tibia torsion.  Pain and dysfunction are generally absent, but a common parental complaint is the frequent tripping and falling of the child.  When the patellae face inward, an internal FPA is at least partly related to femoral anteversion (or internal rotation of the femur).  Femoral anteversion is confirmed on exam when internal rotation exceeds external rotation of the hips in the prone position.  Because internal tibia torsion may be a manifestation of neurologic disorders, metabolic bone diseases or skeletal dysplasias a detailed inspection and history is important.  Radiographs are not indicated to diagnose internal tibia torsion, but a standing lower extremity alignment film from hips to ankles with the patella facing forward is useful to rule out infantile Blount disease in the setting of internal tibia torsion and genu varum.
 
External tibia torsion
Outtoeing denotes an external FPA.  When the patellae face forward, the external foot progression angle may be secondary to a pes planovalgus foot or external tibia torsion.  External tibia torsion is present if the thigh foot angle or bimalleolar axis is greater than the average 20 degrees of external rotation.  When the patellae face outward, femoral retroversion (or external rotation of the femur) contributes to the external FPA.  Patients may present with complaints of anterior knee pain or instability associated with patella maltracking, particularly in the setting of miserable malalignment syndrome (femoral anteversion with external tibia torsion).  Radiographs are not necessary to detect tibia torsion.   
 
Observation for spontaneous resolution of tibia torsion is the mainstay of treatment.  Orthotics are ineffective at altering the torsional profile of a long bone and may cause unnecessary force across joints.  Surgical treatment with derotational osteotomies is reserved for children greater than age 8 with persistent torsional deformity exceeding 15 degrees internal FPA or 30 degrees external FPA accompanied by functional or gait disturbance.  Osteotomies to correct internal or external tibia torsion are best performed in the supramalleolar region.  In the setting of miserable malalignment syndrome, a combination of femur and tibia osteotomies is necessary to correct the problem. 
 
The natural history of tibia torsion is frequently benign, and no standard for what deviations constitute “pathologic” tibia torsion exists.  Gait analysis confirms abnormal knee moments in patients with residual internal and external tibia torsion and decreased ankle power (lever arm dysfunction) with internal torsion normalized with derotational osteotomies averaging 20 degrees.   The potential longterm consequences of abnormal knee loading during gait include osteoarthritic changes more associated with internal torsion and patellofemoral pain and instability with external torsion.  Supramalleolar osteotomy of the tibia reduces risk of compartment syndrome.  Proximal tibia derotation osteotomy is not recommended in skeletally immature patients to avoid potential growth arrest or valgus deformity.
 
Recommended Reading:
  • Staheli, L, et al.Lower extremity rotational problems in children. Normal values to guide management. J Bone Joint Surg Am 1985;67:39-47.
  • Staheli, L.Rotational problems in children. J Bone Joint Surg Am 1993;75:939-949.
  • MacWilliams, B et al.Distal tibial rotation osteotomies normalize frontal plane knee moments.J Bone Joint Surg Am 2010;92:2835-42.
 


Tibia Bowing

1. Anterolateral bowing and congenital pseudarthrosis of the tibia (CPT)
 
Anterolateral bowing can be considered the mildest form of “congenital tibia dysplasia” leading to the more severe form of frank pseudarthrosis on the spectrum.  The disorder is rare, with an estimated incidence of 1 in 150,000-250,000 births.  Pathologic examination of the pseudarthrosis site reveals thickened fibrous tissue and scant vascular ingrowth.  The surrounding periosteum is also abnormal leading some investigators to believe the primary lesion is within the periosteal structures.  The fibrous hamartoma cells are more osteoclastogenic and lack the normal osteoblastic differentiation in response to BMP interfering with bone production and callus formation.  Up to 55-75% of anterolateral bowing and pseudarthrosis cases are associated with neurofibromatosis type 1 (NF-1).  Tibia pseudarthrosis has also been seen in patients with fibrous dysplasia.
 
The anterolateral bow may be obvious at birth, typically located at the middle and distal third junction.  Gross motion is present at the apex of the bow if pseudoarthrosis is present.   The fibula is affected in approximately 1/3 of patients.  Because of the strong association between CPT and neurofibromatosis, a complete evaluation of the child for presence of clinical stigmata of the disease is important including café au lait spots and axillary freckling.   These classic skin findings may not be present at birth, so referral to genetics for appropriate screening for NF-1 is recommended.  A number of radiographic classification systems have attempted to describe prognostic characteristics of the untreated bone.  In clinical practice, the most relevant criterion to guide treatment is presence or absence of a fracture and perhaps age at which the fracture first occurs.  Crawford described a system based on radiographic appearance as follows 1) anteromedial bowing with medullary sclerosis, 2)  anteromedial bowing with constriction of the medullary canal, 3) bowing with cystic lesion 4) frank pseudarthrosis often with tapered bone ends.  Type 4 has the worst prognosis.  In contrast, a Crawford Type 1 nondysplastic tibia is clinically similar to a benign form of anteromedial bowing later described and characterized by subperiosteal bone formation in the concavity of the bowed tibia without fibula involvement.  This type does not progress to fracture, spontaneously resolves, and thus has a favorable prognosis.  AP and lateral radiographs of the affected tibia diagnose the condition.  An MRI may be useful to detail the structure of the pseudarthrosis and surrounding abnormal periosteum for surgical planning but is not an essential tool for diagnosis.
 
Anterolateral bowing remains a challenging problem to treat with fracture inevitably occurring and little propensity for spontaneous healing. The first step in management of anterolateral bowing in a child of weightbearing age is prophylactic bracing with either a knee-ankle-foot orthosis or clamshell functional brace to delay progression to fracture.  Surgical prophylaxis of anterolateral bowing with a posteromedially positioned allograft fibula to “bypass” the intact tibia deformity has shown promising results with no fracture or pseudarthrosis developing in a small series of patients.  Significant residual deformity may remain requiring secondary procedures.  The protocol includes postoperative bracing until maturity.  Once fracture occurs, the goals of surgical treatment are to achieve and maintain tibia union.  Multiple revision procedures may be expected to preserve a functional extremity, and some cases may ultimately be treated with amputation.  A number of different fixation strategies have been described with variable success rates.  Basic principles apply to each treatment method to optimize healing rates including circumferential resection of abnormal tissue and diseased periosteum at the pseudarthrosis site, enhancement of bone repair with autogenous grafting, and reduction of bone resorption.   Intramedullary fixation stabilizes the tibia but frequently traverses the ankle.  The rod may require secondary exchange or advancement across the ankle to maintain alignment as the child grows.  An associated fibula pseudarthrosis is treated simultaneously with resection and intramedullary wire fixation.  An intact fibula should be shortened to avoid potential nonunion of the tibia.   Ilizarov circular external fixator can be used to stabilize, realign and compress the pseudarthrosis site most commonly with a bone transport technique and proximal lengthening.  Ilizarov external fixation combined with intramedullary fixation has been proposed as initial treatment to reduce potential for recurrent deformity and refracture after frame removal.  Free vascularized fibula grafting presents an alternative to autogenous iliac crest grafting of the excised defect adding potential advantage of quicker healing rates and improved vascularity.  In addition to bone grafting, some authors advocate for free periosteal grafting at the site obtained from the ilium.  Medical adjuncts that target different parts of the bone healing process have been studied in the setting of CPT.  BMP-2, which stimulates differentiation of stem cells to preosteoblasts, has been used in conjunction with autograft.  Bisphosphonates, which inhibit osteoclast-mediated bone resorption characteristic of the pseudarthrosis site, may prove to be a useful therapy combined with an anabolic agent such as BMP-2 to enhance union rates.  The combination approach employing pharmacologic agents to supplement surgical treatment shows excellent results with high union rates but longer follow-up is needed to show maintenance of union.  Amputation is the ultimate salvage procedure in cases of resistant pseudarthrosis and dysfunctional extremity.  Ankle disarticulation (Syme or Boyd) is preferred over amputation through the pseudoarthrosis site. 
 
With adherence to basic principles of treatment as outlined above (surgical excision of fibrous hamartoma, stable fixation, fibula resection, autogenous grafting of the defect with or without pharmacologic augmentation) high union rates of 75-85% can be achieved following the index operation.  BMP-2 is advantageous in reducing the time to fracture healing.  Refracture remains a problem occurring in up to 30-57% of cases.  Maintaining alignment of the tibia with intramedullary fixation and exchanging the rod as the child grows is desirable to prevent refracture.  Prior transfixation of the ankle joint with the intramedullary rod leads to a weak stiff ankle and best avoided.  The addition of an Ilizarov circular external fixator provides stability with wires even when the distal segment is short.  Development of ankle valgus is a common complication related to insufficient growth of the fibula or persistent pseudarthrosis.  Treatment is recommended to prevent progressive deformity with either hemiepiphyseodesis or attempted synostosis of the distal tibia and fibula.  Corrective supramalleolar distal tibia osteotomy risks recurrent pseudarthrosis.  Limb length inequality may result from the initial tibia resection and shortening or growth disturbance.  Timed epiphyseodesis of the contralateral limb is the least invasive method to equalize limbs as opposed to lengthening of the dysplastic tibia which may be complicated by iatrogenic pseudarthrosis at the distraction gap.  In addition to standard risks of nonunion and refracture (about 30%), complications innate to vascularized fibula grafting include donor site morbidity and weakness.  Secondary procedures may be necessary to achieve union or address refracture/late deformity, but patients with intact tibia report minimal to no pain and no functional limitations. 
 
Recommended Reading:
  • 1.Richards, B., and Anderson, T.  rhBMP-2 and intramedullary fixation in congenital pseudoarthrosis of the tibia. J Ped Ortho 2016.
  • 2. Vanderhave, K. et al.  Congenital pseudarthrosis of the tibia.  J Am Acad Ortho Surg 2008;16:228-236.
 
2. Posteromedial bowing
 
Congenital posteromedial bowing of the tibia occurs as a result of intrauterine malposition. The deformity is associated with a calcaneovalgus position of the foot and some degree of dorsiflexion contracture of the ankle present at birth.  No known genetic cause exists.  A posteromedial bow is typically an isolated deformity with no associated conditions or anomalies. 

The clinical appearance of the deformity may be striking at birth.  The bow typically involves the middle to distal portion of the tibia, and a skin dimple may be present at the apex of the deformity.  The foot follows the tibia deformity resulting in a calcaneovalgus position.  Orthogonal images of the tibia confirm the diagnosis with the apex of the bow located posterior and medial.  Residual limb length discrepancy exceeding 2.5cm is common.
Initial treatment during infancy is observation because even severe deformities are expected to spontaneously resolve.  Gentle stretching of the ankle dorsiflexors and lateral ankle structures can improve the contracture and the foot deformity, generally by 9 months of age.  Rarely serial casting or splinting may be necessary to correct and maintain the foot position.   The angular deformity of the tibia resolves over a period of 5-7 years.  Significant residual tibia bowing after an adequate period of observation can be treated with corrective osteotomy.  An associated limb length difference of 2.5-5cm can be managed with a timed contralateral epiphyseodesis of the proximal tibia.  A discrepancy projected to exceed 5cm may be treated with tibia lengthening. 
 
The natural history of congenital posteromedial bowing of the tibia is benign with spontaneous resolution expected.  If a corrective osteotomy is indicated to treat residual deformity, normal bone healing can be expected without the risk of pseudarthrosis.   Wedging of the distal tibia epiphysis and fibular hypoplasia with valgus inclination of the ankle may develop in some patients with posteromedial bowing.   Residual limb length discrepancy commonly develops, and the degree of shortening may be related to the severity of the initial deformity.  Patients should be monitored until skeletal maturity for residual tibia bowing, ankle deformity, and limb length discrepancy with appropriate surgical intervention to address abnormal findings as indicated. 
 
Recommended Reading:
  • Shah, H., Doddabasappa, S., and Joseph, B.Congenital posteromedial bowing of the tibia: a retrospective analysis of growth abnormalities in the leg.J Ped Ortho Br 2009;18:120-128.