Limbs Dysplasia Deformity

Genu varum and genu valgum

Physiological and pathological varus and valgus deformity with clinical and standing radiographic assessment.

33 questions 5 source pages 1 fact-check flags

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Q1What are the assessment goals in genu varum/valgum?▸

Severity - clinical: intercondylar/intermalleolar distance
X-ray: zoning and tibiofemoral angle
Delineate the cause
Rule out complications: patella maltracking, collateral laxity

Q2What is the indication for surgery and how is the mature patient managed?▸

Symptomatic zone 2 or zone 3 malalignment
Mature patient: osteotomy

Q3How is knee malalignment managed in the immature patient?▸

Hemiepiphysiodesis (hemipiphysiodesis)
Timing according to the Bowen chart

Q4What is the difference between irreversible and reversible growth modulation?▸

Irreversible: hemiepiphysiodesis, Phemister - advantage is predictable growth
Reversible: staple, physis bridging plate (guided growth), screw - disadvantage is unpredictable growth and time lag
Aim to overcorrect because of the rebound phenomenon
Remove the implant at 2 years, otherwise it will break

Q5How would you assess a child with knee malalignment?▸

Delineate the cause: ricket features (caput quadratum, rachitic rosary, Harrison sulcus), mass, dysmorphic features, CP, scars
Screen: height, body, proportion, symmetry
Special test: cover and uncover test
Severity: gait (varus thrusting), TFA and intermalleolar distance, ROM, collaterals, rotational profile
Complications: LLD, patellar tracking, collateral laxity
Systems examination: hip, spine and feet
X-ray: severity (zoning, tibiofemoral angle), features of primary causes

Q6What are the causes of genu valgum?▸

Bilateral genu valgum: physiological (2-7 y), metabolic (rickets/renal osteodystrophy), neuromuscular (polio, Morquio), neoplastic (HME), dysplasia (MED, SED, MHE, OI), inflammatory
Unilateral genu valgum is usually not physiological
Unilateral causes: trauma (physeal bar/Cozen), infection, tumour (exostosis, FD, Ollier's disease), neuromuscular (polio), developmental/congenital (fibular hemimelia)

Q7What investigations are indicated in genu valgum?▸

X-ray: severity (zoning, tibiofemoral angle) and features of the primary causes
Blood test for metabolic disease

Q8What is the aim of treatment in genu valgum?▸

Restore the mechanical axis
Prevent patellar maltracking and early OA changes

Q9When can you reassure the parents?▸

Age <7 years
TFA <15 degrees
Intermalleolar distance <8cm
Non-progressive

Q10When would you follow up?▸

Age <10 years and:
Progress after 4 years
Intermalleolar distance >8cm
TFA >15 degrees

Q11When would you operate?▸

Age >10 years
Severe valgus: >15 degrees, intermalleolar distance >8cm, MA zone +3

Q12What are the surgical options?▸

Immature + bilateral: temporary hemiepiphysiodesis at MFC and MTP
Mature: varus-producing distal femoral osteotomy

Q13What is the Salenius curve?▸

0-2 years: varus
2 years: neutral
3 years: most valgus
7 years: normal valgus

Q14Why is treatment needed for pathological genu varum?▸

Restore the mechanical axis
Prevent progression of the deformity
Prevent patellar maltracking and early OA

Q15What is the differential diagnosis of bilateral genu varum?▸

Physiological (0-2 years)
Metabolic: early-onset rickets
Neuromuscular (polio)
Neoplastic; Dysplastic (MED, OI)
Developmental: Blount

Q16What is the differential diagnosis of unilateral genu varum?▸

Not physiological
Physeal bar (trauma/infection)
Tumour (fibrous dysplasia)
Developmental (Blount)
Focal fibrocartilaginous dysplasia

Q17What history and examination findings suggest a pathological cause?▸

PMHx/FMHx of rickets, age of starting to walk, obesity
PE for possible cause: facies, scars, CP
Screening: body proportions, arm span
Measure TFA, IC distance, ROM, collateral laxity, rotational profile, LLD, gait
Systems: hip and feet, spine; special test: cover and uncover

Q18What is the workup for genu varum?▸

X-ray: zoning to determine severity, tibiofemoral angle
Rickets features: paint-brush irregular physis, metaphyseal cupping, Looser zone
Blount disease: Langenskiold classification
Achondroplasia: pelvic, physeal and spinal features
Blood test: CaPO4, PTH, ALP, Vit D

Q19Describe the clinical findings in this patient with bilateral genu varum.▸

Bilateral genu varum, asymmetrical on both sides
No scars; some internal rotation/ intoeing of the left lower limb - pathognomonic for Blount's
Likely pathological
Can be physiological depending on age (Salenius curve: varus under 2 years can be physiological)

Q20What are the causes of pathological genu varum?▸

Bilateral: metabolic, neoplastic, neuromuscular, dysplasia/developmental (DDNNM)
Unilateral: infection, tumour (HME, focal fibrocartilaginous dysplasia), trauma, Blount's, iatrogenic, tibial hemimelia
Physiological depends on age (Salenius curve: varus under 2 years can be physiological)

Q21How would you assess a child with genu varum?▸

History: onset, progression, other deformities; trauma/infection/tumour; rickets risk (diet); Blount's risk (early walking, obesity)
Look for rickets: caput quadratum, rachitic rosary, Harrison sulcus, catback kyphosis, short stature
Screen height, body, proportion, symmetry; gait varus thrusting; LLD; ROM and collaterals; TFA and intermalleolar distance
Rotational profile; systems exam (hip, spine, feet); cover and uncover test
XR + scannogram: TFA, LDFA, MPTA, mechanical axis zoning, medial slope angle, Drennan angle
Bloods CaPO, Vita D, PTH ALP; MRI for physeal bar; +/- CT for rotation

Q22Which radiographic parameters should be measured on the scannogram in Blount's disease?▸

TFA, LDFA, MPTA
Mechanical axis deviation (zoning)
Medial slope angle, Drennan angle
LLD, compensatory distal femoral valgus, Tibial-femoral subluxation
Look for features of rickets, other causes, and classify with Langenskiold

Q23What is Blount's disease and what is its pathophysiology?▸

Dyschondrosis of the medial proximal tibial physis causing progressive pathological genu varum centred at the tibia
Related to mechanical overload in genetically susceptible individuals
Excessive medial pressure causes osteochondrosis +/- physeal bar (Heuter-Volkmann law: increased stress = less growth)
Vs physiological varus: progressive, more abrupt (Drennan angle >11 need close monitoring, >16 = Blount's), physeal abnormality, asymmetrical flaring
Langenskiold stages: beak, wedge, step, enlarge/fill, double, fused

Q24What is the problem list in Blount's disease?▸

1. Varus angular deformity
2. Medial physeal bar/osteochondrosis
3. Depressed joint surface
4. Tibial internal torsional deformity
5. Femoral anteversion
6. Procuvartum

Q25What is the aim of treatment in Blount's disease?▸

Aim of treatment: restore mechanical axis to unload medial physis and prevent further progression (Heuter Vollkman law)

Q26How is infantile Blount's disease treated?▸

Age cut-off 4 years; severity by Langenskiold stage (III-VI) or Drennan angle
Stage I-II: brace (KAFO with genu varus strap, droplocks to increase corrective force during weight bearing), follow up XR for medial physis reconstitution - operate if progression within 1 year
Stage III or above: brace likely fails; gold standard RAB (oblique biplanar) osteotomy with overcorrection
Adjuvant: physeal bar excision, hemiepiphysiodesis, hemiplateau elevation, correct internal rotation
Other: growth modulation with tension band plate and screws

Q27How does adolescent Blount's disease differ?▸

Onset >10 years; treatment depends solely on the varus angle >10 degrees
CT/MRI to see whether the physis is closed
Physis open: lateral tibial epiphysiodesis (permanent or temporary)
Physis closed: osteotomy without overcorrection - HTO or EF/Ilizarov/TSF +/- prophylactic fasciotomy

Q28What are the risk factors for recurrence and the drawbacks of Langenskiold staging?▸

Recurrence: age >5, body weight >95th percentile, medial physeal slope >60 degrees, Langenskiold stage IV or above
All stages can occur earlier than the described age
Stages II and III can progress to VI despite osteotomy (OT does not change the natural history)
Single osteotomy gives good results only <4 years but not <8 years; original series Only include white population instead of more severe Afro-American population

Q29Describe the findings on this standing radiograph.▸

Skeletally immature; bilateral genu varum (increased femorotibial angle)
Asymmetrical; mechanical axis zone 3
Varus centred at the tibial epiphyseal-metaphyseal area
Widening of the physis, irregularity +/- fragment
Medial physeal sloping +/- beak, wedge, step; +/- lateral subluxation of the tibia; +/- triangular epiphysis

Q30Which angles would you measure?▸

Tibiofemoral angle
LDFA (normal 85), MPTA (normal 87)
Mechanical axis deviation (zoning)
Drennan angle
Medial physeal sloping angle

Q31What is the Drennan angle and what does it mean?▸

Used to distinguish physiological bowing from Blount's disease
<9 degrees: likely physiological
>11 degrees: suspected Blount's / needs close monitoring
>16 degrees: consider osteotomy

Q32What is the medial physeal sloping angle and its significance?▸

Angle between tangential lines to the lateral and medial physis
>60 degrees: high chance of recurrence even after osteotomy

Q33What other features must you look for on the radiograph?▸

Features of trauma, infection, tumour or a systemic cause
LLD if present

Fact check

A Drennan (metaphyseal-diaphyseal) angle >11 degrees indicates Blount's disease, and >16 degrees requires osteotomy — imprecise/contested threshold — Levine and Drennan found >11 degrees is associated with Blount's, but Feldman and Schoenecker found 9-16 degrees indeterminate (37% of physiological bowing exceeded 11 degrees); >16 degrees is the more specific threshold used to presume Blount's — (medium confidence) — source

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Genu varum and genu valgum

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