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 Pathophysiology physiologic progression of coronal alignment genu varum <2 years of age neutral alignment around 2 years genu valgum will peak at 3-4 years to a tibiofemoral angle of 15-20 degrees genu valgum rarely worsens after age 7 after age 7 valgus should not be worse than 12 degrees of genu valgum after age 7 the intermalleolar distance should be <8 cm lateral deviation of mechanical axis decreased growth from lateral physis relative to medial physis patellar instability increased Q-angle shallow lateral femoral sulcus lateral femoral condyle growth suppressed predisposing to lateral subluxation Associated conditions bilateral genu valgum physiologic renal osteodystrophy (renal rickets) skeletal dysplasia Morquio syndrome spondyloepiphyseal dysplasia chondroctodermal dysplasia unilateral genu valgum physeal injury from trauma, infection, or vascular insult proximal metaphyseal tibia fracture Cozen Phenomenon benign tumors fibrous dysplasia osteochondromas enchondromas fibular hemimelia Anatomy 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