A Protocol to Systematic Radiographic Assessment of Primary Total Knee Arthroplasty

Figures & data

Figure 1 Assessment in the coronal plane (AP radiograph).

Notes: (A) defining the axes; c, coronal; FMA, femoral mechanical axis; FAA, femoral anatomical axis; DFL, distal femoral line; PTL, proximal tibial line; TMA, tibial mechanical axis; TAA, tibial anatomical axis; (B) lower limb mechanical axis (MA); MAD, mechanical axis deviation; KY, Kennedy and White; (C) HKA, hip, knee to ankle angle; (D) aTFA, anatomical tibiofemoral angle; (E) VCA, valgus correction angle.

Figure 2 Assessment in coronal plane continued.

Notes: (A), mLDFA, mechanical lateral distal femoral angle; (B) aLDFA, anatomical lateral distal femoral angle; (C) MPTA, medial proximal tibial angle; (D) cJLH, coronal joint line height; (E) LLD, leg length discrepancy.

Figure 3 Assessment in the sagittal plane (Lateral radiograph).

Notes: (A) defining the axes; s, sagittal; FMA, femoral mechanical axis; FAA, femoral anatomical axis; DFL, distal femoral line; PTL, proximal tibial line; TMA, tibial mechanical axis; TAA, tibial anatomical axis; (B) DFFA, distal femoral flexion angle; TS, tibial slope; (C) ACO, anterior condylar offset; PCO, posterior condylar offset; JLH, joint line height; Insall Salvati index = length of line B/ length of line A, Caton-Deschamps Index = length of line C/length of line D.

Figure 4 Assessment in the axial plane (special views).

Notes: (A) Merchant view; PA, patellar axis; AFCL, anterior femoral condylar line; PPBA, patellar prosthesis-bone angle; (B) kneeling view; CTA, condylar twist angle; aTEA, anatomical transepicondylar axis; sTEA, surgical transepicondylar axis; PCL, posterior condylar line.

Table 1 Radiographic Parameters for Knee Assessment Pre, Post, and for Follow-Up of TKA

Parameters	Pre-OP	Post-OP	Follow Up		Normal Values
					Native Knee	TKA
A-CORONAL PLANE (AP radiograph)
HKA					1.3 ± 1.3°^Citation19	0 ± 3° (180 ± 3°)^Citation28
VCA					3: 11^Citation29
aTFA					Valgus 7° ± 1.4^Citation19	Valgus 2.4°:7.2°^Citation1
mLDFA					87.8° ± 1.6^Citation19,Citation20	90° ± 3^Citation29,Citation30
aLDFA					79° to 83°^Citation19	85° ± 2^Citation30
MPTA					87.2° ± 1.5^Citation20	90°: 87°^Citation31
JLH					25: 28 mm from the medial femoral epicondyle-10: 14 mm from the fibular head^Citation32,Citation33	Should reproduce the preoperative normal values
LLD
B-SAGITTAL PLANE (Lateral radiograph)
TS					81° ± 3^Citation20	0°: 7° (may differ according to various implants designs)^Citation38,Citation39
DFFA					83° ± 4^Citation20	90°: 87°^Citation24
PCO
ACO
ISI					1.2^Citation44	>1.2 patella Alta, <0.8 patella Baja^Citation44
JLH
C-AXIAL PLANE (merchant, kneeling radiographs)
Sulcus angle					135 ± 10°^Citation55
Patellar tilt
Patellar thickness
Patellar shift
PPBA
CTA					Varies according to deformity, arthritis, ethnicity.	0° if measured in reference to the aTEA - 3° to 4° of external rotation if measured in reference to the sTEA.^Citation11,Citation61

Abbreviations: AP, anteroposterior; HKA, hip, knee to ankle angle; VCA, valgus correction angle; aTFA, anatomical tibiofemoral angle; mLDFA, mechanical lateral distal femoral angle; aLDFA, anatomical lateral distal femoral angle; MPTA, medial proximal tibial angle; JLH, joint line height; LLD, leg length difference; TS, tibial slope; DFFA, distal femoral flexion angle; PCO, posterior condylar offset; ACO, anterior condylar offset; ISI, Insall Salvati index; PPBA, patellar prosthesis-bone angle; CTA, condylar twist angle.

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