SUMMARY

• Genu Valgum is a normal physiologic process in children which may also be pathologic if associated with skeletal dysplasia, physeal injury, tumors or rickets. 

• Diagnosis is made clinically with presence of progressive genu valgum after the age of 7. 

• Treatment is observation for genu valgum <15 degrees in a child <7 years of age. Surgical management is indicated for severe and progressive genu valum in a child > 7 years of age. 

EPIDEMIOLOGY

• Incidence

  • common but true incidence unknown 

• Demographics

  • most common age of presentation 3-5 years

    • range 2-8 yrs

• Anatomic location

  • distal femur is the more common location of pathological deformity 

• Risk factors

  • prior infection or trauma 

  • vitamin D deficiency/rickets

  • obesity 

  • skeletal dysplasia

  • lysosomal storage diseases 

ETIOLOGY

• Osteology 

  • knee 

    • normal lateral distal femoral angle (LDFA) = 85-90 degrees 

    • normal medial proximal tibia angle (MPTA) = 85-90 degrees

    • hypoplastic lateral femoral condyle with shallow lateral femoral sulcus 

• Ligament

  • medial collateral ligament 

    • 2 components 

      • superficial 

        • femoral attachment medial epicondyle 

        • tibial attachment proximal tibia deep and posterior to pes anserinus

      • deep MCL 

        • composed of meniscofemoral and meniscotibial ligaments

    • may be attenuated in genu valgum

• Tendon 

  • increased combined lateral vector of quadricep and patellar tendon (increased q-angle)

    • predispose to patellar instability 

• Nerves 

  • common peroneal nerve

    • branch off sciatic nerve that winds laterally around fibular neck 

    • bifurcates into two branches

      • superficial peroneal nerve

        •  innervates lateral compartment of leg which controls eversion of foot

      • deep peroneal 

        • innervates anterior compartment of leg which controls dorsiflexion 

• Biomechanics

  • mechanical axis  

    • center of femoral head to center of ankle should pass through center of knee

    • lateral deviation of mechanical axis in genu valgum

      • lateral femoral condyle and lateral tibia plateau subjected to increased loads

  • mechanical loading on physis modulates growth 

    • Hueter–Volkmann law

      • compression inhibits growth 

      • distraction stimulates growth

    • greater proportion of change in growth rate from hypertrophic zone (75%) than proliferative (25%)

      • greater effect on growth seen from change in size of chondrocytes than number 

CLASSIFICATION

• No uniform classification

  • unilateral vs bilateral

  • based on underlying etiology 

DIFFERENTIAL DIAGNOSIS

• Physiologic genu valgum must be differentiated from pathologic causes

  • physiologic 

  • apparent 

    • obesity resulting in large thighs

    • excessive femoral anteversion 

    • excessive external tibial torsion  

  • idiopathic

  • post-traumatic 

    • Cozen phenomenon

    • malunion 

    • physeal arrest 

  • metabolic

    • renal osteodystrophy 

    • hypophosphatemic rickets 

  • infection 

    • osteomyelitis 

  • neuromuscular

    •  poliomyelitis 

  • neoplastic

    • multiple hereditary exostoses

    • fibrous dysplasia 

    • osteochondromas

  • lysosomal storage disease

    • mucopolysaccharidosis type IV (Morquio)

  • skeletal dysplasia

    • Chondroectodermal dysplasia (Ellis-van Creveld)

    • Spondyloepiphyseal dysplasia tarda

    • Pseudoachondroplasia 

    • Focal Fibrocartilaginous dysplasia 

PRESENTATION

• History 

  • medical and family history can help differentiate between physiological and pathological etiology

• Symptoms 

  • cosmetic deformity most common complaint

  • often asymptomatic 

  • medial sided knee pain

• Physical exam

  • abnormal circumduction gait

  • inspection

    • hip adduction

    • medial aspect of knees touching

    • wide intermalleolar distance (>8 cm)  

    • leg lengths 

  • range of motion

    • assess patellar tracking 

  • rotational profile

    • apparent genu valgum with excessive femoral anteversion or external tibial torsion  

  • general exam to assess stigmata of associated conditions 

    • rickets 

    • syndromic features

    • skeletal dysplasias 

    • Maffucci syndrome 

IMAGING

• Radiographs 

  • indication

    • asymmetrical findings

    • excessive genu valgum clinically age group beyond which is expected of physiologic changes

    • short stature

    • history of trauma or infection

    • limb length discrepancy 

  • views

    • AP standing long-length film 

      • patella should be facing forward to ensure proper positioning 

  • findings

    • lateral deviation of mechanical axis through knee

    • physeal narrowing or premature closing

    • Park-Harris lines

• CT or MRI

  • rarely indicated

    • evaluate underlying malignancy

    • evaluate for physeal bar  

STUDIES 

• lab studies 

  • depends on suspected underlying medical conditions

    • rickets

      • serum calcium and phosphate

      • 25-OH Vit D3 levels

      • PTH 

    • mucopolysaccharidoses

      • urinalysis for excess muscopolysaccharides (ie keratan sulfate - Morquio)

    • syndromic

      • genetic testing

TREATMENT

• Nonoperative

  • indications

    • first line treatment 

    • tibiofemoral angle <15 degrees

    • children <7 years of age

  • modalities

    • observation and medical management 

    • bracing

      • rarely used

  • outcomes

    • vast majority of physiological genu valgum will resolve spontaneously 

    • medical management of underlying etiology may slow progression 

    • bracing may provide temporary relief but is an ineffective long-term solution

• Operative

  • indications

    • tibiofemoral angle > 15 degrees

    • intramalleolar distance of 10 cm after age 10 years 

    • rapidly progressive deformity after age of 7  

  • modalities

    • medial hemiepiphysiodesis

      • temporary (more common) 

      • permanent

    • osteotomy 

      • distal femoral osteotomy 

      • high tibial osteotomy 

  • outcomes

    • eight-plate hemiepiphysiodesis 

      • >95% complete correction for idiopathic 

      • 80% complete correction for pathological 

    • rate of correction with hemiepiphysiodesis is variable

      • angular correction of 7 degrees per year at the distal femur

      • angular correction of 5 degrees per year at the proximal tibia

TECHNIQUE

• Observation

  • techniques

    • observation and reassurance 

• Medial hemiepiphysiodesis   

   

  • indications

    • > 15-20° of valgus in a patient between ages 7-10

    • if line drawn from center of femoral head to center of ankle falls in lateral quadrant of tibial plateau in patient > 10 yrs of age 

  • options

    • temporary hemiepiphysiodesis

      • rigid stapling

      • percutaneous screw (Metaizeau)

      • tension band plate and screws

    • permanent hemiepiphysiodesis

      • modified Phemister technique

  • technique

    • location of hemiepiphysiodesis dependent on 3 factors

      • amount of remaining growth

      • location of deformity

      • severity of deformity 

    • place extraperiosteally to avoid physeal injury 

    • implant placed midsagittal to avoid sagittal plane deformity 

    • one eight-plate or two staples per physis is generally sufficient

    • postop

      • follow patients often to avoid varus overcorrection 

      • implant removal

        • remove once mechanical axis passes through center or knee or slightly medial 

        • account for rebound medial overgrowth resulting in loss of correction

          • more likely in younger patients

      • growth begins within 24 months after removal of the tether

  • complications (~5-10%)

    • screw loosening or failure

    • rebound deformity after removal

    • infection

    • premature physeal closure

• Osteotomy 

    

  • indications

    • insufficient remaining growth to correct deformity with hemiepiphysiodesis

    • skeletally mature patients

    • non-functional growth plate (ie presence of bar, infection etc) 

  • options

    • lateral distal femur opening wedge osteotomy

      • pros

        • angular correction can be adjusted to desired correction

      • cons

        • requires grafting

        • less stable construct 

        • prolonged immobilization to allow graft to heal

    • medial distal femur closing wedge osteotomy

      • pros

        • stable osteotomy 

        • shorter period of immobilization

        • avoid distracting lateral common peroneal nerve

      • cons

        • technically demanding to remove precise angular wedge

    • high tibial osteotomy

  •  technique

    • determining site of osteotomy

      •  dependent on site of deformity 

        • assess mLDFA and mPMTA 

        • femur most common site of deformity

  •   complications

    • nonunion

    • neurovascular complication

    • compartment syndrome

    • hardware failure

COMPLICATIONS

• Peroneal nerve injury

  • risk factors

    • opening wedge technique

  • prevention

    • perform a peroneal nerve decompression at the time of surgery prior to distraction

      • two potential areas of entrapment

        • fascia of the lateral compartment

        • intermuscular septum separating the anterior and lateral compartments

    • gradual correction of severe deformities can be done with circular external fixator

• Nonunion

  • risk factors

    • opening wedge osteotomy

    • >20 deg deformity 

• Limb length discrepancy

  • closing wedge osteotomy shortens limb

  • opening wedge osteotomy lengthens limb

• Undercorrection

  • insufficient physeal growth or encroaching maturity

• Overcorrection

  • lost to follow-up (12%) 

• Rebound phenomenon 

  • incidence

    • 56%

  • defined as a loss of 5 degrees of correction once the plate is removed

  • risk factors

    • femoral deformity

    • younger age at plate application and removal

    • faster correction rate 

    • intentional overcorrection increased risk

  • treatment 

    • consider slight overcorrection prior to implant removal 

      • may not prevent rebound growth but may limit recurrence of deformity

    • consider performing growth modulation closer to skeletal maturity for milder deformities

• Physeal closure

  • very rare (<1%)

  • prevention

    • place implant extraperiosteally 

    • remove implant with 2-3 years after insertion

PROGNOSIS

• Idiopathic genu valgum has a better prognosis than pathological etiology with hemiepiphysiodesis

  • higher rate of complete correction 

  • faster correction rate

  • fewer complications

• Physiologic genu valgum resolves spontaneous in vast majority by age of 7

• Deformity after a proximal metaphyseal tibia fracture (Cozen) should be observed as most remodel

  • maximum magnitude of deformity reached approximately 12-18 mo after injury

  • resolve spontaneously within 2-4 years 

• Threshold of deformity that leads to future degenerative changes is unknown