• Deformity is a common referral to paediatric orthopaedic clinics
• Deformity could be present in a single plane:
  1. Coronal (e.g. varus or valgus)
  2. Sagittal (e.g. Procurvatum/recurvatum.
  3. Axial (e.g. Shorter or longer leg)
  4. Rotational ( e.g out-toeing or in-toeing)
• Or could be multi-planer ( combinations of the above)
• Patients usually present for cosmetic reasons, loss of function or symptoms such as pain and clicking.

 Deformity originates from the Latin word “deformis” which means ‘misshapen’.

• Deformity: Loss of normal form - alignment and joint orientation.
• Mal-alignment: Loss of co-linearity of the hip, knee and ankle joints.
• Mal-orientation: Loss of normal joint orientations

These can present in several combinations:

• Deformity with no mal-alignment or mal-orientation.
• Deformity with mal-alignment but no mal-orientation.
• Deformity with mal-orientation but no mal-alignment.

• AP (Coronal)

Angulations- Varus/Valgus

Translations- Medial/Lateral

• Lateral (Sagittal)

Angulations- Apex anterior/posterior

Translations- Anterior/ Posterior

• Axial

Angulations- Internal/External rotation

Translations- Long/Short

• Functional problems: e.g. Gait abnormalities, lever arm problems
• Pain- Degenerative joint disease- increased shear stresses on articular surfaces
• Cosmesis- low self esteem

Congenital

1. Longitudinal: Limb Deficiencies
    Proximal: Femoral Deficiency
    Distal: Fibular/Tibia Hemimelia

2. Posteromedial tibial bowing
3. Blount’s Disease
4. Skeletal dysplasias e.g. Multiple Hereditary Exostosis, Ollier’s disease

Acquired

1. Trauma
2. Infection
3. Metabolic bone disease
4. Physeal arrest
5. Neurological condition (CP and polio)
6. Joints diseases and contractures (DDH, LCPD)

1. Assessment of limb: Assessment of coronal, sagittal and transverse plane alignment, Assessment of girth asymmetry
2. Spine Assessment: Assessment of alignment
3. Assessment of gait: Look for short leg gait, Trendelenburg’s gait, lateral thrust for genu varum, foot progression angle for torsional deformities
4. Leg Length Discrepancy (LLD): assessing using more than one method- standing blocks method, Galleazi test, Tape measurements from bony landmarks                                 Clinical assessment, LLD
5. Clinical measurement of deformity: measure intercondylar distance for genu varum deformities and inter-malleolar distance for genu valgum deformities                      Bilateral symmetrical genu-varum, measuring the intercondylar distance
6. Rotational profile assessment: Foot progression angle, thigh foot angle, maximum internal and external rotation of hip joint to assess version, foot deformities using heel bisector line method
7. Assess joint range of movements and abnormal laxity above and below the deformity
8. Assess for fixed joint compensations in joints above and below the deformity
9. Assess neurovascular status and general health
10. Scars from previous surgeries and skin markings

Assessment of Deformity

1.      Where is the deformity?

• Which segment of the limb?
• Which plane(s)?

2.      Is the deformity pathological?
3.      Does the deformity need treatment?

Radiological

1. Standing long leg films: Pelvis levelled with blocks under short leg if required, patella facing forwards and a metric ruler and calibration ball
2. CT and MR scans to assess joint and rotational profile.
3. EUA + Arthrogram

1. Ensure adequate x-rays

2. Mechanical axis deviation test: a line drawn from the centre of femoral head to centre of ankle joint in coronal plane should pass within 8 mm from the centre of the knee joint.

3. Joint orientation angles: Lateral distal femoral angle (m LDFA) and Medial proximal tibial angle (MPTA) both should be around 87°. Lateral proximal femoral angle (m LPFA) and lateral distal tibial angle (m LDTA) should be around 90°. Joint line convergence angle (JL CA) more than 2° would be considered as abnormal laxity of the joint that would contribute to mechanical axis deviation.

4. Rule out knee subluxation in coronal plane: the mid-points of femoral and tibial joint line at the knee should be within 3 mm of each other.

5. Rule out condylar deficiency at the knee: Any deficiency of either of the femoral condylar or tibial hemiplateau should be noted as this can be the source of mechanical axis deviation.

Lower limb alignment in the frontal and sagittal planes. Image is courtesy of Postgraduate Paediatric Orthopaedic, Cambridge University Press.

Pitfalls

• It is possible to have a normal mechanical axis with deformities in the hip or close to ankle joint.
• It is possible to have a normal mechanical axis with mal-orientation of the joint lines around the knee.
  

1. Acute correction

Mild to moderate deformities can be corrected acutely and then stabilised either internally or using an external fixator. Generally, deformities more than 30° carry a risk of neurovascular injury and compartment syndrome and acute correction should be avoided.

Acute correction can be stabilised either by using plates and screws or IM nail.

Acute deformity correction using an intramedullary road.

Acute deformity correction using a plate.

Plates and screws:

Advantages

Ideally suited for peri-articular deformities where external fixation carries a risk of spreading infection into the joint and is also likely to cause stiffness.

Disadvantages

Generally more invasive.

Intramedullary nail:

Advantages

Minimally invasive techniques, percutaneous osteotomy. Ideally suited for diaphyseal and rotational deformities.

Disadvantages

Osteotomy rule 1 applicable- as very limited scope for correction with translation.

2. Gradual correction

This is a technique to inhibit growth in one side of the physis to correct the deformity. Inhibition of growth can be temporary or permanent. Older techniques using Phemister bone block and drill epiphysiodesis can only be used towards the end of growth. Temporary epiphysiodesis can be done using staples and 8 plates and are particularly useful in younger patients.

• Temporary: 8 plates, Staples
• Permanent: Drill hemiepiphysiodesis, Phemister bone block technique.

Gradual deformity correction using monolateral external fixator.

2. Circular fixator

These are versatile deformity correction tools and all aspects of deformity can be corrected gradually with this fixator. Broadly classified into 2 types - the traditional Ilizarov type fixator and hexapod fixator. Figure 1.9.10

Advantages

All aspects of deformity can be corrected gradually. It is by mechanically more stable.

Disadvantages

Fine wire fixation around the joints can cause patient discomfort, joint stiffness and are prone for infection. Newer techniques of using half pins can give these fixators advantages of a mono lateral fixator with the versatility of the circular fixator.

Gradual deformity correction using circular frame.

Osteotomy rules

In order to correct a deformity, bone is divided (osteotomy). Careful planning of the osteotomy and the hinge where the bone will be rotated around is vital for good correction. The followings are useful rules:

Rule 1: Osteotomy should pass through the transverse bisector line. If the hinge is placed on the convex side, opening wedge osteotomy occurs. If on the concave side, closing wedge osteotomy. If at center, half closing and half opening osteotomies (neutral wedge).

Rule 2: If the osteotomy is done at a different level than the Center Of Rotational of Angulation (CORA), then translation occurs.

Rule 3: If osteotomy is done at a different level than CORA but hinge placed at osteotomy site, mechanical axis becomes parallel but anatomical axis becomes zigzag.