Approach to Angular Deformity in Children Under 8 Years

1. Normal Physiologic Sequence of Lower Limb Alignment

• Genu varum normally evolves to genu valgum by age 2.5 years with gradual transition to physiologic valgus by age 4 years
• Up to 15 degrees of valgus at the knee is common in children 2-6 years of age
• Cases within this physiologic range do not require treatment

2. Causes of Angular Deformity in Children <8 Years

Genu Varum (Bowed Legs)

• Physiologic - normal in children <2 years (most common cause)
• Blount disease (infantile type) - age 0-4 years (most common pathologic cause)
• Osteogenesis imperfecta
• Osteochondromas
• Trauma / physeal injury
• Various dysplasias (rickets, skeletal dysplasias)

Genu Valgum (Knock-Knees)

• Physiologic - common between 2-6 years
• Renal osteodystrophy (most common pathologic bilateral cause)
• Tumors (e.g., osteochondromas)
• Infections - may stimulate proximal asymmetric tibial growth
• Trauma

3. Key Diagnostic Tool: Differentiating Physiologic from Pathologic

• Deformity outside the expected age range
• Asymmetric bowing (unilateral)
• Progressive rather than improving
• Obesity + early walking + internal tibial torsion → suspect Blount disease
• Associated metabolic disease (rickets: cupping/fraying of metaphyses on X-ray)
• Severe deformity (>15° genu varum in a toddler, metaphyseal-diaphyseal angle >16°)

• AP standing X-ray of both lower extremities
• Drennan metaphyseal-diaphyseal angle: >16° is abnormal - formed between the metaphyseal beaks; differentiates Blount from physiologic bowing
• Physiologic bowing shows symmetric flaring of tibia and femur

4. Infantile Blount Disease (Age 0-4 Years)

• Stage I or II + patient <3 years: Bracing (KAFO - knee-ankle-foot orthosis)
• Stage II (age >3 years) and Stage III: Proximal tibial/fibular valgus osteotomy to overcorrect (because medial physeal growth abnormalities persist)
• Stages IV-VI: Complex, multiple procedures required; epiphysiolysis also needed for stages V and VI

5. Tibial Bowing - Classification and Approach

6. Genu Valgum (Knock-Knees) - When to Intervene

• Conservative treatment is ineffective in pathologic genu valgum
• Surgery is considered in children older than 10 years with:

  • 10 cm between the medial malleoli, OR

  • 15 degrees of valgus angulation

• In children under 8 years, hemiepiphysiodesis (temporary/timed) of the medial distal femoral physis is effective for severe deformities if performed before end of growth
• Mechanism: Guided growth relies on the Hueter-Volkmann law (growth is decreased by increased compression); physeal growth returns to normal when compression is removed

7. Remodeling Potential: Fracture-Related Angular Deformity

• Young children have extensive remodeling potential - many angular deformities from fractures correct spontaneously
• Older children do NOT remodel as well (e.g., 10° angulation in forearm bones at age >10 years may cause significant rotation limitation)
• Corrective osteotomy for post-fracture angular deformity should be delayed at least 1 year unless function is impaired
• Torsional deformities after femoral fractures: most are mild (<10°) and asymptomatic, rarely requiring treatment

Summary: Decision Framework for Angular Deformity <8 Years

Child with angular deformity
        ↓
Is it within physiologic age range?
    YES → Observe, reassure, follow up
    NO  ↓
Is it progressive, asymmetric, or severe?
    ↓
Investigate for pathologic cause:
  - Blount disease (Drennan angle, Langenskiold stage)
  - Metabolic bone disease (rickets, renal osteodystrophy)
  - Congenital: fibular hemimelia, pseudarthrosis
  - Trauma / physeal injury
        ↓
Pathologic confirmed?
  - Age <3 yrs + Stage I/II Blount → KAFO Bracing
  - Age >3 yrs / Stage II-III Blount → Proximal tibial osteotomy
  - Genu valgum: hemiepiphysiodesis if severe (before growth ends)
  - Posteromedial tibial bowing → Observe, monitor LLD
  - Anterolateral bowing (pseudarthrosis) → Total-contact brace, then surgery

• [Miller's Review of Orthopaedics, 9th Ed.](Miller's Review of Orthopaedics, pp. 276-279) - Physiologic patterns, Blount disease, tibial bowing
• [Schwartz's Principles of Surgery, 11th Ed.](Schwartz's, p. 1944) - Remodeling potential in pediatric fractures
• [Campbell's Operative Orthopaedics, 15th Ed. 2026](Campbell's, p. 1856) - Acceptable angulation and corrective osteotomy timing

Plate-Induced Osteoporosis (Stress Protection Osteoporosis)

1. Definition

2. Basis: Wolff's Law

• Bone subjected to normal physiological loading - compressive and tensile forces - maintains or increases its density
• Bone deprived of mechanical stimulation undergoes resorption and becomes osteoporotic
• A rigid plate carries most of the applied load, so the underlying cortex receives far less strain than normal → net bone resorption dominates over formation

3. Mechanism / Pathophysiology

Rigid plate applied to bone
        ↓
Plate has high stiffness (especially steel > titanium)
        ↓
Plate carries majority of applied mechanical load
(stress bypasses the underlying bone cortex)
        ↓
Underlying cortex experiences reduced strain
(below the threshold required to stimulate osteoblastic activity)
        ↓
Osteoclastic resorption > Osteoblastic formation
        ↓
Cortical thinning + increased intracortical porosity
        ↓
Structurally weakened bone beneath and around the plate

• Periosteal stripping during plate application disrupts the periosteal blood supply, further impairing bone nutrition and remodeling
• Rigidity of fixation suppresses secondary (callus) bone healing and forces primary/direct bone healing, which is a slower process with no radiographic callus evidence of strength
• Atrophy of bone under screw holes from local pressure necrosis and vascular disruption

4. Factors That Determine the Severity

5. Radiographic / Clinical Features

• Radiographs: Cortical thinning and osteopenia visible beneath and adjacent to plate; screw holes appear lucent and widened; absence of periosteal callus (primary bone healing leaves no radiographic trace of consolidation)
• Clinically: Bone appears healed radiographically but is mechanically weak
• Key danger: Early or premature plate removal → refracture through the original fracture site (through osteoporotic, screw-holed bone)

6. Why Primary (Direct) Bone Healing Makes This Worse

• Rigid plates that achieve absolute stability promote primary/contact bone healing, which proceeds without intermediate callus
• This healing process is slower and does not produce the structural buttress that callus provides
• When loaded to failure, radiographically "healed" bones stabilized with compression plates failed through the original fracture site at 48 weeks in one-third of specimens (animal studies)
• Because the bone looks "healed" on X-ray but is structurally weak, the surgeon may be falsely reassured - plate removal therefore carries high refracture risk

7. Prevention Strategies

A. Implant Material Choice

• Titanium plates are less stiff than stainless steel → less stress shielding
• PEEK (polyetheretherketone) plates - even more flexible, approaching bone stiffness; decrease bending stiffness significantly
• Note: changing material mainly affects bending stiffness; axial motion adjacent to plate remains deficient unless implant design specifically addresses it

B. Plate Design

• Locking Compression Plates (LCP): Locked screws do not compress plate to bone → preserves periosteal blood supply; acts as internal-external fixator
• MIPO (Minimally Invasive Plate Osteosynthesis): Avoids periosteal stripping → better biologic environment
• Bridge plating: Longer working length + fewer screws per fragment → allows relative motion → stimulates callus formation

C. Dynamic / Active Implants

• Dynamic Locking Screws (DLS) / Far Cortical Locking (FCL) screws: Thinner screw shaft elastically flexes relative to near cortex → enables controlled axial dynamization at fracture site → stimulates callus without shear motion
• Active locking plates: Elastomeric elements within locking holes allow controlled axial motion
• Both screw dynamization and plate dynamization have shown faster, stronger, and more circumferential healing compared to rigid locking constructs in animal models

D. Timing of Plate Removal

• Plate removal should be delayed for up to 2 years after surgery to allow adequate time for the bone to regain structural integrity
• Early removal (before 2 years, especially in the first year) carries the highest risk of refracture through the original fracture site
• After removal, patient should be counselled to protect the limb (avoid contact sports, heavy loading) for 6-12 weeks while screw holes fill in with remodeled bone

8. Consequences of Plate-Induced Osteoporosis

9. Summary Table: Plate Stiffness vs. Fracture Healing

• Rockwood & Green's Fractures in Adults, 10th Ed. 2025 - Primary bone healing, stress shielding, strategies for improvement
• Bailey & Love's Short Practice of Surgery, 28th Ed. - Plates and screws: advantages/disadvantages