J Korean Fract Soc.  2017 Jul;30(3):156-166. 10.12671/jkfs.2017.30.3.156.

Clinical and Radiological Analysis of Angular Deformity of Lower Extremities

• Jeong C
• Noh JH

• KMID: 2424126
• DOI: http://doi.org/10.12671/jkfs.2017.30.3.156

Abstract

The alignment of lower extremities is an important consideration in many clinical situations, including fracture reduction, high tibia osteotomy, total knee arthroplasty, and deformity correction. Mal-alignment of lower extremities is not only a simple cosmetic problem, but it can also produce pain, limp, and early degenerative arthritis. An assessment of lower extremity alignment, including its location and magnitude of deformity, can be achieved via mal-alignment test and mal-orientation test, using a lower extremity standing full-length radiography. Proper evaluation allows the surgeon to determine an effective treatment plan for deformity correction.

Keyword

Deformity; Lower extremity

MeSH Terms

Arthroplasty, Replacement, Knee
Congenital Abnormalities*
Lower Extremity*
Osteoarthritis
Osteotomy
Radiography
Tibia

Figure

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  Fig. 1. Nomenclature of the frontal plane joint orientation angle relative to the mechanical axis (A) and anatomic axis (B). (C) Nomenclature of the sagittal plane joint orientation angle relative to the anatomic axis. LPFA: lateral proximal femoral angle, mLDFA: mechanical lateral distal femoral angle, MPTA: medial proximal tibial angle, LDTA: lateral distal tibial angle, MPFA: medial proximal femoral angle, MNSA: medical neck shaft angle, LDFA: lateral distal femoral angle, JLCA: joint line convergence angle, PPFA: posterior proximal femoral angle, ANSA: anatomic neck shaft angle, PDFA: posterior distal femoral angle, PPTA: posterior proximal tibial angle, ADTA: anterior distal tibial angle.

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  Fig. 2. Anatomic axis to joint center distance (aJCD) of the hip joint of the hip (A) and tibia (B). Bold line: anatomic axis, Dot line: joint center point. d: distance.

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  Fig. 3. Anatomic axis to joint edge ratio (aJER) of the distal femur and proximal tibia.

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  Fig. 4. Mechanical axis deviation (MAD).

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  Fig. 5. (A) If center of rotation of angulation (CORA) lies at the point of obvious deformity apex in the bone and the joint orientations are normal, the deformity is uniapical. (B) If CORA lies outside the point of obvious deformity apex or either joint orientation is abnormal, a second CORA exists in that plane and the deformity is multiapical or a translational deformity exists in that plane. (C) When the CORA lies outside the boundaries of the involved bone, a multiapical deformity is likely to be present.

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  Fig. 6. The Malalignment test is to identify the sources of mechanical axis deviation. Step 0 is to draw the mechanical axis; Step 1 is to measure the mLDFA; Step 2 is to measure the MPTA; Step 3 is to measure the JLCA; Step 4 is to measure the joint center distance; and Step 5 is to identify the joint surface Malalignment. mLDFA: mechanical lateral distal femoral angle, MPTA: medial proximal tibial angle, JLCA: joint line convergence angle, JCP: joint center point.

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  Fig. 7. The standing lateral full length radiography of lower extremity shows 15° of hyperextension (HE) of the knee joint and 120° of PDFA, which is 36° recurvatum of the distal femur. Therefore, there is also 21° of knee joint flexion contracture and genu recurvatum. PDFA: posterior distal femoral angle, PPTA: posterior proximal tibial angle.

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  Fig. 8. Analysis of uniapical deformity of the tibia using the mechanical axis: Draw the mechanical axis and measure MAD (A). Draw the mechanical axis of the femur and tibia. Measure mLDFA and MPTA (B). If MPTA is outside the normal range, the mechanical axis of the femur is extended distally as a mechanical axis line when mLDFA is within normal range. Draw the mechanical axis of distal tibia from the center of the ankle parallel to the diaphysis of the tibia and measure LDTA. If LDTA is within normal range, mark the CORA and measure the magnitude of angulation (C). MAD: mechanical axis deviation, mLDFA: mechanical lateral distal femoral angle, MPTA: medial proximal tibial angle, LDTA: lateral distal tibial angle, CORA: center of rotation of angulation, Mag: magnitude of deformity.

Reference

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