rotational profile of the lower extremity in achondroplasia : computed tomographic examination of 25...
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Rotational Profile of the Lower Extremity in Achondroplasia : Computed Tomographi
c Examination of 25 patients
Hae-Ryong Song, M.D., Keny Swapnil.M M.S ,Jong-Won Chung, M.D.
Department of Orthopedic SurgeryKorea University Guro Hospital, Seoul, Korea
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Deformities of Lower Extremity in Achondroplasia
• Coxa vara
• Genu varum
• Heel varus
Evaluation of combined deformity necessary when
performing osteotomies for correction of the
deformities
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Computed Tomography
• More accurate method for measuring rotational deformity of lower extremity
• No report about rotational profile of lower extremity in achondroplasia by CT scans, as well as clinical methods and plain radiographs
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Materials
• 25 patients with achondroplasia
12 females, 13 males
Age 6~37 (mean 15.6)
13 children, 12 adults
• All patients diagnosed with gene mutation analysis between December, 2000 and January, 2004
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Methods
• Measure of bilateral torsion of the acetabulum, femur and tibia in 50 limbs
• Using 2 multi detector-row CT scanners (LightSpeed Plus; General Electric Medical Systems, Milwaukee, WI
SOMATOM Sensation 16, Siemens, Forchheim, Germany)
• 5.5mm slice thickness
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CT Scans
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Acetabular Anteversion
• Axial CT scans
At the level of the center of the hip joint
Line connecting the posterior ischia
Line connecting the posterior and anterior margins of the acetabulum
At the center of the hip joint
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Femoral Torsion
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Proximal reference line : the line joining the center of the head and the neck
Distal reference line : the line tangent to the most posterior points of the femoral condyle
The angle between proximal and distal reference lines
Proximal Femur Section showing the greater trochanter, femoral neck, femoral head, and acetabulum
Distal Femur Section showing the largest medial and lateral femoral condyles
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Tibial Torsion
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Ellipse tibial condyle
Proximal reference line : The estimiated long axis of the tibial condyle
Distal reference line : The axis through the centers of medial and lateral malleoli
Proximal tibia Section immediately below the joint line showing the entire anterior and posterior border of proximal tibial condyle
Distal tibia Section immediately above the joint line showing medial and lateral malleoli
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External rotation deformity
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Ext. Rotational deformity-retroversion of left hip
Left
Left
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Measurements
• By three examiners for interobserver variation
Two orthopaedic surgeons
One radiologist
• Intraobserver variation
Measurement repeated one month later
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Statistics
• SPSS 9.0 standard statistical version
• Calculation of percentage agreement and intra- and inter-observer difference
Intraclass correlation coefficient (ICC)
ICC > 0.75 excellent
ICC 0.40~0.75 fair
ICC < 0.40 poor agreement
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Results
• Mean angle of acetabular anteversion 21.5±6.4° in adults 13.6±7.5° in children Excellent ICC values
• Mean angle of femoral torsion 30.5±20.1° in adults 27.1±20.8° in children Excellent ICC values
• Mean angle of tibial torsion 22.5±10.8° in adults 21.6±10.6° in children Fair to good ICC values
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Results-Summary
• The femoral anteversion decreases during growth in normal children
• The femoral anteversion in achondroplasia was more than the normal values (age matched peers ) regardless of age
• No compensation of the increased femoral anteversion by the tibial torsion during growth in patients with achondroplasia
• No significant difference between children and adults
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Results- Summary
• No difference in Acetabular torsion compared to normal value (age matched peers ) regardless of age
• Acetabular torsion in achondroplasia had no change during growth
• No significant difference between children and adults
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Conclusion
• Increased femoral anteversion and decreased tibial external torsion in children and adults with achondroplasia
• No increase or decrease of femoral and tibial torsion during growth
• The increased femoral torsion was not compensated by the tibial torsion during growth
• The torsional deformity should be evaluated carefully before surgery and treated during correction of angular deformities
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Thank you for your attention