Journal List > J Korean Fract Soc > v.30(3) > 1038101

Jeong and Noh: Clinical and Radiological Analysis of Angular Deformity of Lower Extremities

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. Malalignment 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 Malalignment 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.

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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.
jkfs-30-156f1.tif
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.
jkfs-30-156f2.tif
Fig. 3.
Anatomic axis to joint edge ratio (aJER) of the distal femur and proximal tibia.
jkfs-30-156f3.tif
Fig. 4.
Mechanical axis deviation (MAD).
jkfs-30-156f4.tif
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.
jkfs-30-156f5.tif
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.
jkfs-30-156f6.tif
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.
jkfs-30-156f7.tif
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.
jkfs-30-156f8.tif
Table 1.
Normal Values for Joint Orientation Angles in Lower Extremity
Bone-Plane   Component Mean value (°) Normal range (°)
Femur-Frontal
 Anatomic medial proximal femoral angle (aMPFA) Anatomic axis Trochanter-head line 84 80–89
 Mechanical lateral proximal femoral angle (mLPFA) Mechanical axis Trochanter-head line 90 85–95
 Neck shaft angle (NSA) Anatomic axis Femoral neck line 130 124–136
 Anatomic lateral distal femoral angle (aLDFA) Anatomic axis Distal femoral joint orientation line 81 79–83
 Mechanical lateral distal femoral angle (mLDFA) Mechanical axis Distal femoral joint orientation line 88 85–90
Femur-Sagittal
 Posterior distal femoral angle (PDFA) Mid-diaphyseal line Sagittal distal femoral joint orientation line 83 79–87
Tibial-Frontal
 Medial proximal tibial angle (MPTA) Mechanical axis Proximal tibial joint orientation line 87 85–90
 Lateral distal tibial angle (LDTA) Mechanical axis Distal tibial joint orientation line 89 88–92
Tibial-Sagittal
 Posterior proximal tibial angle (PPTA) Mid-diaphyseal line Sagittal proximal tibial joint orientation line 81 77–84
 Anterior distal tibial angle (ADTA) Mid-diaphyseal line Sagittal distal tibial joint orientation line 80 78–82
Table 2.
Clinical Signs and Symptoms Associated with Sagittal Plane Deformity of Lower Extremity21)
Sagittal plane deformity Clinical symptom & sign
Proximal femur flexion deformity Hyperlordosis of spine
Proximal femur extension deformity Loss of hip flexion
Distal femur procurvatum Flexion deformity and stretching of posterior knee joint capsule
Distal femur recurvatum Loss of flexion
Proximal tibia recurvatum Chondromalacia patella
Proximal tibia procurvatum Knee flexion deformiry, chondromalacia & pain
Distal tibia recurvatum Late degenerative joint disease
Distal tibia procurvatum Anterior impingement syndrome
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