Salenius Curve for the FRCSOrth

Courtesy: Quen Tang, FRCSOrth

Topic / Overview

Evaluation of pediatric coronal plane lower-limb angular deformities (genu varum and genu valgum) utilizing the Salenius curve, alongside clinical criteria to differentiate physiological growth variations from pathological deformities requiring treatment, based strictly on the provided lecture transcript.

Background / Problems

• Clinical Presentation: Pediatric patients frequently present with coronal plane angular deformities of the knee (genu varum or genu valgum).

• Primary Diagnostic Imperative: The foundational clinical step is determining whether the angular deformity represents a benign physiological variation of normal growth or a pathological condition necessitating intervention.

• Historical Basis: In 1975 (published in JBJS), Salenius evaluated approximately 1,500 children from birth onward to establish the normal progression of the tibiofemoral angle in the coronal plane relative to chronological age.

Classification or Concept

1. Clinical Differentiation: The “Five S’s”

To distinguish physiological from pathological angular alignment, evaluate five clinical parameters:

• Symptoms: Presence or absence of pain.

• Symmetry: Whether the lower-limb deformity is symmetrical or asymmetrical.

• Stiffness: Restriction in joint range of motion versus full, unrestricted mobility.

• Systemic Disorders: Association with underlying systemic conditions.

• Syndromes: Presence of associated syndromic features.

2. Physiological vs. Pathological Profiles

• Physiological Deformity:

  • Pain-free, symmetrical genu varum or genu valgum.

  • Complete, full range of motion (no stiffness).

  • Absence of associated systemic disorders or syndromes.

  • Represents a benign variation of the normal growth pattern.

• Pathological Deformity:

  • Painful, asymmetrical, and/or stiff angular deformity.

  • Associated with systemic disorders or syndromes.

  • Requires active medical or surgical treatment.

Technique / Principles: Plotting and Interpreting the Salenius Curve

1. Graph Axes and Scaling

• X-Axis (Horizontal): Patient age in years (plotted from birth to at least 7 years of age: 1, 2, 3, 4, 5, 6, 7).

• Y-Axis (Vertical): Coronal plane tibiofemoral angle plotted in 5-degree increments:

  • Upper half: Varus alignment (extending up to 20 degrees of varus).

  • Zero line: Neutral alignment (0 degrees).

  • Lower half: Valgus alignment (extending down to 15 degrees of valgus).

2. Chronological Milestones on the Curve

• At Birth: Normal physiological varus of 15 degrees.

• 18 Months of Age: Alignment progresses to neutral (0 degrees).

• 3 to 4 Years of Age: Reaches a maximal physiological valgus angle of approximately 10 degrees.

• 7 Years of Age to Adulthood: Gradually settles to a normal physiological valgus of 5 to 7 degrees, plateauing at this angle into adulthood.

3. Accounting for Normal Population Variation

• Draw two parallel boundary lines above and below the main Salenius curve to represent two standard deviations (2 SD).

• Alignment values falling anywhere within this 2 SD envelope remain within the spectrum of normal physiological variation.

Practical Clinical Implications

• Avoid Unnecessary Intervention: Recognising the normal age-dependent shift from 15 degrees of varus at birth to 10 degrees of valgus at age 3–4 prevents overtreatment of benign physiological bowing or knock-knees.

• Screen with the Five S’s First: Regardless of age, any child presenting with pain, asymmetry, joint stiffness, or systemic/syndromic features falls outside physiological parameters and warrants investigation for pathological etiology.

• Use Standard Deviation Boundaries: A child’s coronal tibiofemoral angle does not need to sit strictly on the mean line; values falling within two standard deviations of the Salenius curve represent normal growth.

Key Take-Home Points

• Five S’s Screening: Evaluate Symptoms (pain), Symmetry, Stiffness, Systemic disorders, and Syndromes to separate benign physiological alignment from pathological deformity.

• Salenius Study Foundation: Derived from 1,500 children (published in JBJS, 1975) tracking normal coronal tibiofemoral angle against age.

• Key Age-Angle Landmarks:

  • Birth: 15 degrees varus.

  • 18 months: Neutral (0 degrees).

  • 3–4 years: Peak valgus of 10 degrees.

  • 7 years to adulthood: Plateaus at 5 to 7 degrees valgus.

• Normal Range Envelope: Two parallel lines representing two standard deviations above and below the mean curve define the complete range of normal physiological growth.