Comparison of the Radiologic, Morphometric, and Clinical

Comparison of the Radiologic, Morphometric, andClinical Outcomes between Kinematically andMechanically Aligned Total Knee Arthroplasty:A Propensity Matching StudyTaeWoo Kim, MD, PhD1 Jae Ik Lee, MD2 Han Gyeol Choi, MD2 Hyun Jin Yoo, MD2 Kyu Tae Kim, MD2

Yong Seuk Lee, MD, PhD2

1Department of Orthopedic Surgery, Seoul National UniversityCollege of Medicine, Seoul National University Boramae MedicalCenter, Seoul, The Republic of Korea

2Department of Orthopedic Surgery, Seoul National UniversityCollege of Medicine, Seoul National University Bundang Hospital,Seongnam, The Republic of Korea

J Knee Surg

Address for correspondence Yong Seuk Lee, MD, Department ofOrthopaedic Surgery, Seoul National University College of Medicine,Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si,Gyeonggi-do 463-707, The Republic of Korea(e-mail: [email protected]).

Keywords

► total kneearthroplasty

► kinematic alignment► mechanical

alignment► coronal alignment► rotational alignment► morphometry

Abstract The purpose of this studywas to compare radiologic,morphometric, and clinical outcomesbetween kinematically aligned (KA) andmechanically aligned (MA) total knee arthroplasty(TKA) in Korean patients. Overall, 168 patients who underwent primary TKA wereretrospectively reviewed, and propensity matching (age, sex, and body mass index) wasperformed as 1:3 ration (KATKAs [n¼ 42]: MATKAs [n¼126]). Joint-line orientation angle(JLOA), coronal and axial alignments of implants, hip–knee–ankle (HKA) angle, and patellartilt angle were assessed using full-length standing radiograph, axial computed tomography(CT) scan, and plain radiographs. Morphometric assessment was performed by analyzingthe intraoperativemeasurementof the femoral cut surfaceand femoral componentsfittingin five zones. Clinical outcomes more than 2 years of follow-up were evaluated with theKnee Society (KS) knee and functional scores, Western Ontario and McMaster UniversitiesOsteoarthritis Index (WOMAC) scores, and the Short-Form Health Survey (SF-36). Inradiologic results, JLOA was more parallel to the floor in KA TKAs (KA: medial tilt0.9�1.5 degrees; MA: lateral tilt 1.7�1.5 degrees, p<0.05), and patellar tilt anglewas closer to preoperative status after KA TKA (KA: 2.0�1.6 degrees;MA;0.3� 1.2 degrees, p< 0.05). HKA angle and rotationalmismatchwere similar betweentwo groups. In morphometric analysis, entire overhang of anterior femoral cutting surfacewas reduced in KA TKA compared with MA TKA (KA: 11.7� 6.2mm; MA: 14.4�5.9mm,p<0.05). However, both ofMAandKATKAs showedunderhang inmediolateral dimensionwithout difference. There were no significant differences in clinical scores between twogroups. KA TKA showed more parallel JLOA to floor, closer patellar tilt to preoperativestatus, and better anterior flange fitting that can reproduce more natural knee kinematicscompared with MA TKA. Although clinical outcomes assessed by conventional evaluatingtools were similar between two groups, further evaluation focusing on the patellofemoralsymptoms or unawareness of TKA is necessary to clarify the clinical benefit of KA TKA.

receivedJuly 29, 2020accepted after revisionJanuary 12, 2021

© 2021. Thieme. All rights reserved.Thieme Medical Publishers, Inc.,333 Seventh Avenue, 18th Floor,New York, NY 10001, USA

DOI https://doi.org/10.1055/s-0041-1725006.ISSN 1538-8506.

Original Article

Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

Published online: 2021-03-03

mailto:[email protected]

Mechanical alignment is regarded as the current standard forthe restoration of coronal alignment in total knee arthroplasty(TKA) and transepicondylar axis is generally accepted as areliable landmark for the femoral component rotation.1,2

Regarding tibial component rotation, it is determined byseveral landmarks or axes including tibial anterior curvedcortex and tibial tuberosity because there is lacking inconsensus.3 The concept of anatomic restoration has gainedinterest in the form of kinematically aligned (KA) TKA. KATKA corrects the arthritic deformity to correspond to theconstitutional alignment of the patient, restoring the naturalarticular surface, and the laxities of the knee.4,5 Comparativestudies between KA andmechanically aligned (MA) TKAs haveshown that clinical outcomes of KA TKAwere similar or betterthan those of MA TKA at early- to mid-term follow-up.6 Limband knee alignments were similar to those of MA TKA, andcomponent alignment of KA TKA showed slightly more varusin the tibial component and slightlymorevalgus in the femoralcomponent.7 However, studies on the difference in axialrotation, and patellofemoral relation between MA and KATKAs are limited.

Matching the patient’s anatomywith TKA component wasthe goal of arthroplasty to achieve optimal results.8,9 Theanthropometricmeasurement of distal femur cutting surfacemay be changed according to the alignment profile charac-teristics of KA and MA TKA. Especially, anterior cuttingsurface could be definitely different because they havedifferent concepts in rotational alignment. While MA TKAencourage external rotation of the femoral component basedon the transepicondylar axis, KA TKA insists neutral rotationof the femoral component. However, anthropometrical com-parison betweenMAandKATKAs are also rarely investigatedyet. Therefore, it is necessary to evaluate whole alignmentchanges including coronal, sagittal, and axial planes on bothMA and KA TKAs, and it is also sure to know how theyproduce different morphometries on the cutting surface.

The purpose of this study was to compare radiologic,morphometric, and clinical results between KA and MATKAs in Asian patients. The hypotheses of this study werealignment profiles and morphometry of the femoral cuttingsurface between KA andMA TKAs would be different and thiswill produce different radiologic, morphometric, and clinicalresults.

Materials and Methods

PatientsWe retrospectively reviewed 396 patients who underwentprimary TKA at our institution between March 2017 andFebruary 2018. The inclusion criteriawere limited to patientswith varus osteoarthritis (OA) of the knee with mild flexioncontracture and varus deformity. The exclusion criteria wereas follows: (1) OA with valgus deformity, (2) severe varusdeformity (hip–knee–ankle [HKA] angle >15 degrees) orflexion contracture (>20 degrees), (3) bone defects morethan 5mm, (4) conversion TKA following osteotomy orunicompartmental knee arthroplasty, and (5) revisionalTKAs. Forteen knees were excluded based on the exclusioncriteria. Then, considering the KA andMA TKAs’ incidence inour clinic, 1:3 propensity matching was performed based onthe age, sex, and bodymass index (BMI). Finally, a total of 168patients (42 KATKAs and 126MATKAs)were enrolled in thisstudy, and evaluated using radiologic, morphometric, andclinical results with a minimum 2-year follow-up (►Fig. 1).This study was approved by the institutional review board ofour institution.

Radiological EvaluationRadiological evaluations were performed preoperatively andpostoperative 1 year. Coronal alignment parameters includingHKA angle, varus/valgus angle of the femoral and tibialcomponents, and joint-line orientation angle (JLOA) in relation

Fig. 1 Patient diagram of this study. OA, osteoarthritis; KA, kinematically aligned; MA, mechanically aligned; TKA, total knee arthroplasty.

The Journal of Knee Surgery © 2021. Thieme. All rights reserved.

Comparison between Kinematically and Mechanically Aligned TKA Kim et al.

Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

to the floor were analyzed with standing long-leg anterior–posterior (AP) radiographs obtained at the patellar facingforward position10 (►Fig. 2). To evaluate patellofemoralrelationship, patellar tilt angle was measured on axial plainradiograph.11

Rotational alignment of the femoral and tibial componentsand mismatch angle between the long axes of the twocomponentsweremeasured on postoperative axial computedtomography (CT) scans. Femoral component rotation wasdefined as the angle between the transverse axis of femoralcomponent and the surgical transepicondylar axis.12 Therotation of the tibial component was defined as the anglebetween the line that connects the geometric center ofthe tibial plate and the medial margin of the tibial tuberosityand AP axis (►Fig. 3).13 Rotational mismatch was measuredas the angle between AP axes of the femoral and tibialcomponents. Tibial component rotation and rotational

mismatch was measured by overlapping of the two axialtransparent CT images (►Fig. 4). To evaluate intra- andinterobserver reliabilities of the radiological assessment, twoorthopaedic surgeons measured all radiological parameterstwice with intervals of 6 weeks.

Morphometric AnalysisMorphometric assessment was performed by analyzing theintraoperative measurement of the femoral cut surface, andfemoral components fitting in five zones.14 Measurementsfor zones A and B were defined as length of anterior medial(LAM) and length of anterior lateral (LAL) condyles. Themeasured distance was the perpendicular distance fromthe anterior cut surface to the most proximal point ofthe resected surfaces. Zones A and B were related with themorphometry of the anterior cut surface. Anterior flangewidth (AFW, zone C) was measured to evaluate anterior

Fig. 2 Measurement of tibial component rotation: (A–C) tibial component rotation was defined as the angle between the line that connectgeometric center of tibial plate and medial margin of tibial tuberosity (tAP) and anterior–posterior axis of tibial component (tcAP). Internalrotation (�), external rotation (þ). Dotted line in (C) represents orientation of ground (G). GC, geometric center; maF, mechanical axis of femur;maT, mechanical axis of tibia; mTT, medial margin of tibial tuberosity; tAP, AP axis of tibia; tcAP, AP axis of tibial component.



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

flange mediolateral dimension. Middle mediolateral width(MML, zone D) and posterior medial–lateral width (PML,zone E) were related to the distal cutting surface (►Fig. 5).The dimensions from each zone were compared with thecorresponding dimension of the prosthesis supplied by themanufacturer. The difference between the prosthesis dimen-sion and the actual femoral dimension was deemed positivewhen there is oversizing, and negative when undersized.

Sum of cut surface–prosthesis difference in zones A and Bwas also measured to evaluated entire fitting of anteriorflange between two groups. All measurements wereperformed by a single senior surgeon with the consensusof fellows during the operation.

Clinical EvaluationPreoperatively and minimum 2 years postoperatively, clini-cal results were rated using the Knee Society (KS) knee andfunctional scores, Western Ontario and McMaster Universi-ties Osteoarthritis Index (WOMAC) scores, and the Short-Form Health Survey (SF-36). Range of motion (ROM; flexioncontracture and maximum active flexion angle) was evalu-ated preoperatively and postoperatively at 6 months, 1 year,and 1-year interval thereafter. All clinical evaluations wereperformed by physical assistant who was blinded to theoperation.

Surgical TechniqueAll TKAs were performed by a single surgeon who had morethan 10 years’ experience of TKA. In all patients, Personaknee implants (Zimmer Biomet, Warsaw, IN) were used withthe cement fixation technique. The patella was resurfacedselectively depending on the arthritic status and thickness ofthe patella.

For KA TKA, there wasminimal release of the deepmedialcollateral ligament (MCL). All procedures regarding boneresection was performed based on the Howell’s KA TKAtechnique using conventional instrument.15 To make equal9-mm cuts of the medial and lateral distal femur includingthe cartilage thickness, cartilage wear on the medial distalfemoral condyle was judged and full-thickness wear wasregarded as 2mm and partial thickness as 1mm with a sawthickness of 1mm. After additional 1- or 2-mm sim wasattached to the medial surface of distal cutting guide, distalfemur was resected locating the cutting guide parallel to the

Fig. 3 Measurement of rotational mismatch between femoral andtibial components: rotational mismatch angle was measured as theangle between anterior-posterior axes of femoral (fcAP) and tibialcomponents (tcAP). mTT, medial margin of tibial tuberosity.

Fig. 4 Measurement of distal femoral cutting surfaces of right knee.fcAP, anterior–posterior axis of femoral component; tcAP, anterior–posterior axis of tibial component.

Fig. 5 (A) zone 1: length of anteromedial condyle (LAM); (B) zone 2:length of anterolateral condyle (LAL); (C) zone 3: anterior flange width(AFW); (D) zone 4: middle medial–lateral width (MML); (E) zone 5:posterior medial–lateral width (PML).



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

joint line. Adjustment of intramedullary guide angle basedon the preoperative measurements on long-leg radiographand wide proximal reaming enabled distal cutting guide tocontact both sides of distal femur simultaneously. To verifythe cutting accuracy, thickness of resected bone was mea-sured using digital caliper (►Table 1). The rotational axis oftibia was determined as the AP axis of the lateral tibialplateau and tibial cutting was performed to make equal 9-mm cutting of medial and lateral tibial plateau consideringcartilage wear and 7 degrees of posterior slope. The femoralcomponent rotation and size were determined using poste-rior referencing guidewith 0 degrees of external rotation andall cases showed relatively intact posterior cartilage thick-ness. Thus, distal and AP femoral and tibial cuttings wereperformed to reproduce native joint orientation.

For the MA TKA, distal femur was resected perpendicularto mechanical axis and femoral component was rotated 3-degree externally in all cases. Tibial bone was also resectedperpendicular tomechanical axis, aimingwithin 5 degrees ofposterior slope. Femoral AP cutting was performed withanterior referencing system. Tibial rotation was determinedbyfirst adjusting to the posterolateral corner and secondarilyadjusting to the anterior cortical rim. Compared with the KATKA, extension and flexion gaps were all targeted to therectangular gap. Ligament balancing was performed byselective piecrusting in all cases.

Statistical AnalysisAll parameters were presented as mean with standarddeviation (SD). Categorical variables were analyzed withPearson’s Chi-squared test or Fisher’s exact test and contin-uous variables were analyzed with Student’s t-test. Potentialconfounding and selection biases were accounted for bydeveloping a propensity score because patients were notrandomly assigned. The propensity for surgical techniquewas determined usingmultivariable logistic regression anal-ysis. After calculating the propensity scores for the threeindependent variables of age, sex, and BMI, a 1:3 match wasperformed. The statistical significance was set at p<0.05.Intraclass correlation coefficients were used to evaluateintra- and interobserver reliability. All statistical analyseswere performed with SPSS (version 22.0, Chicago, IL).

Results

The inter- (kappa¼0.831) and intraobserver (kappa¼0.859)reliabilitieswere good. Therewereno significantdifferences interms of demographics and preoperative clinical scores(►Table 2). Preoperative varus deformity and range of motionwere not different between two groups by propensity match-ing. The mean follow-up periods were 28�3.5 months at KATKA group and 28�4.2 months at MA TKA group.

Radiological ResultsIn coronal plane, femoral component of KA TKAs wereimplanted with more valgus position compared with MATKAs (KA: valgus 2.5�2.0degrees;MA:varus0.8�1.8degrees,p<0.05). On the contrary, tibial component of KA TKAs wereimplanted with more varus position compared with MA TKAs(KA: varus 2.5�1.5 degrees; MA: varus 0.1�1.6 degrees,p<0.05). However, there was no difference between twogroups in the HKA angle that presented the entire coronallimb alignment (KA: varus 0.5�2.4 degrees; MA: varus1.3�2.1 degrees, p¼0.163). JLOAwasmore parallel to thefloorin KA TKAs compared with MA TKAs (KA: medial tilt0.9�1.5 degrees; MA: lateral tilt 1.7�1.5 degrees, p<0.05;►Fig. 6).

In rotational alignment, both of the femoral and tibialcomponents were rotated more internally in KA TKA than inMA TKA (femur, KA: internal rotation [IR]¼1.1�1.4 degrees,MA; external rotation [ER]¼0.5�1.7 degrees, p<0.05/tibia,KA: 3.85�3.2 degrees, MA: 5.32�3.4 degrees, p<0.05).However, there was no significant difference in rotationalmismatch angle between the two components (KA:1.1�1.4 degrees, MA: 0.9�1.2 degrees, p¼0.35; ►Table 3).

Table 1 Thickness of tibial and femoral bone cuts duringkinematically aligned total knee arthroplasty

Thickness ofbone cut (mm)

Tibia Medial 5.4�1.8

Lateral 7.9�1.7

Distal femur Medial 6.8�0.8

Lateral 8.0�0.5

Posteriorfemur

Medial 7.9�0.6

Lateral 7.8�0.4

Table 2 Comparison of preoperative demographic databetween two groups using propensity matching

KA (n¼42) MA (n¼126) p-Value

Mean age (y) 70.30� 5.06 70.38� 5.76 0.937

Sex (M:F) 2:40 9:117 0.592

Laterality(right/left)

20/22 59/67 0.414

Body massindex (kg/m2)

25.11� 3.31 25.34� 3.10 0.481

HKA angle Varus 7.7� 4.5 Varus 8.4� 5.5 0.375

ROM(degrees)

118.5� 9.5 116.7� 12.4 0.340

KS score knee 26.6� 10.4 23.6� 9.3 0.165

function 38.6� 10.1 36.1� 6.3 0.156

WOMAC 49.0� 8.8 50.8� 8.5 0.354

SF-36 PCS 28.3� 6.7 25.3� 9.2 0.118

MCS 33.9� 10.3 30.7� 7.7 0.103

Abbreviations: F, female; HKA, hip–knee–ankle; KA, kinematicallyaligned; KS, Knee Society; M, male; MA, mechanically aligned; MCS,mental component summary; PCS, physical component summary;ROM, range of motion; SF, Short Form; WOMAC, Western Ontario andMcMaster Universities.Note: Values are presented asmean� standard deviation. The statisticalsignificance was set at p< 0.05.



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

Patellar-resurfacing ratio were comparable between KA andMA groups (KA: 40.5%, MA: 42.9%). On axial plain radiograph,the patellawas tiltedmore laterally in KATKA than inMATKA.However, patellar tilt angle was more close to preoperativestatus after KA TKA than after MA TKA (KA: 2.0�1.6 degreesMA: 0.3�1.2 degrees ►Fig. 7).

Morphometric ResultsThe average length of distal femoral cutting surface increasedin transitioning from zone A to zone E. Our results show thatthemaximal length of zone B (LAL) was longer than the lengthof zone A (LAM) in both of MA and KA groups. However, KATKA showed longer zone A dimension (KA: 14.8�4.1mm;MA: 10.1�4.1mm, p<0.05) and shorter zone B dimension(KA: 21.9�5.1mm; MA: 23.4�5.0mm, p<0.05) comparedwith MA TKA. There were no statistically significant differ-ences betweenMA andKATKA groups in the zones C, D, and E.When analyzing mean difference between implant and distalfemoral cutting surfaceof the168knees, zonesAandBshowedoverhangbothofMAandKAgroups.However,KATKA showedshorter mean difference of zone A and implant (KA:3.1�4.3mm; MA: 7.2�4.3mm, p<0.05) and longer meandifference of zone B and implant (KA: 8.6�4.1mm; MA:7.2�4.0mm, p<0.05) compared with MA TKA. Consideringentire anterior cut surface overhang, KA showed better ante-rior flange fitting than MA TKA (KA: 11.7�6.2mm; MA:14.4�5.9mm, p<0.05).

Zones C, D, and E showed underhang both of MA and KAgroups. There were no statistically significant differencesbetween MA and KA TKA groups in the zones C, D, and E(►Table 4).

Clinical ResultsAt thefinal follow-up, therewas no significant difference in KSknee score and KS function score between KA andMATKA (KS

knee, KA TKA: 82.1�6.4, MA TKA: 80.2�6.7, p¼0.529/KSfunction, KA TKA: 85.0�7.5, MA TKA: 82.7�6.4, p¼0.471).TheWOMAC score and SF-36 score were also similar betweentwo groups (WOMAC, KA TKA: 20�7.9, MA TKA: 16�7.6,p¼0.428/SF-36, KA TKA: 83.1�6.3, MA TKA: 83.5�8.2p¼0.921). For ROM, KA TKA showed increased flexion angleonly at postoperative 3 months compared with MA TKA (KA:134.2�10.3 degrees; MA: 129.1�10.5 degrees, p¼0.038).However, there was no difference in ROM between the twogroups at postoperative 1 year. In all groups, there were nocomplications including implant loosening or infection andproblematic instability that required revision surgery duringthe follow-up (►Table 5).

Discussion

The principal finding of this study was that KA TKA showed(1) more parallel joint line to the floor with femoral compo-nent valgus and tibial component varus, (2) closer patellartilt to the preoperative status, and (3) more proper fitting ofthe anterior flange, compared with MA TKA.

Fig. 6 Comparison of Joint-line orientation angle (JLOA) betweenmechanical aligned (MA) and kinematic aligned (KA) total kneearthroplasty (TKA). (A) Lateral tilt (negative value) JLOA in MA TKA;(B) Medial tilt (positive value) JLOA in KA TKA.

Table 3 Comparison of radiologic analysis between two groups

Alignment profiles KA(n¼42)

MA(n¼126)

p-Value

Coronal alignment

FC Alignment (degree) 2.5�2.0 �0.8�1.8 <0.05

TC Alignment (degree) 2.5�1.5 0.1�1.6 <0.05

JLOA (degree) �0.9�1.5 1.7�1.5 <0.05

HKA angle (degree) 0.5�2.4 1.3�2.1 0.163

Rotational alignment

FCR (s TEA; degree) 1.1�1.4 0.5�1.7 <0.05

TCR (degree) 3.85�3.2 5.32�3.4 <0.05

Mismatch (degree) 1.1�1.4 0.9�1.2 0.355

Patellar tilt angle(degree)

Preoperative 1.5�1.5 1.3�1.7 0.254

Postoperative 2.0�1.6 0.3�1.2 <0.05

ΔPre-op–post op(degree)

0.5�1.7 1.1�2.0 <0.05

Abbreviations: FC, femoral component ; FCR, femoral componentrotation ; HKA, hip-knee-ankle; IR,; JLOA, joint-line orientation angle; KA,kinematically aligned; MA, mechanically aligned; Pre-op, preoperative;post-op, postoperative; TC, tibial component ; TCR, tibial componentrotation; TEA, surgical transepicondylar axis.Notes: Values are presented as mean� standard deviation. The statis-tical significance was set at p< 0.05.FC alignment (degree) was defines as 90� lateral distal femoral angle(degree). Positive and negative values of FC alignment means valgusand varus, respectively. TC alignment (degree) was defines as 90�medial proximal tibial angle (degree). Positive and negative values of TCalignment means varus and valus, respectively. Positive and negativevalues of JLOA means lateral and medial tilt, respectively. Positive andnegative values of HKA angle means varus and valgus, respectively.Positive and negative values of FCRmeans external rotation and internalrotation, respectively.



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

However, regardless of these differences, there was nosignificant difference in clinical outcomes between the twogroups. Therefore, our hypotheses were partially adoptedand partially declined.

Similar to recent meta-analyses that compared KA andMATKAs, our study showed more valgus femoral component andmore varus tibial component with comparable HKA angle in

KA TKA.6,7 These results could be explained by the nativeorientation of the distal femur and the proximal tibia. Normalvalue of mechanical lateral distal femoral angle and medialproximal tibial angle were known to be 88 and 87 degrees,respectively.16 Therefore, a femoral component valgus of2.5 degrees and tibial component varus of 2.5 degrees in ourKATKAcould closely reproduce native orientationof thedistalfemur and proximal tibia. In this study, femoral valgus andtibial varus orientation in KA TKA resulted in more paralleljoint line to the floor compared with MA TKA. Similar resultswere observed in studies by Ji et al17 and Matsumoto et al18

that compared postoperative JLOA between KA and MA TKA.Considering that JLOA of healthy patient is 0.3�2.0 degrees inthe study byVictor et al19 and0.2�1.1 degrees in the study byJi et al,17 KA TKA seems to reproduce joint-line orientationmore closely to prearthritic status compared with MA TKA.

Another important finding in this study was that KA TKAshowed more internally rotated femoral and tibial compo-nents with similar rotational mismatch compared with MATKA. Nedopil et al20 have also reported that incidence ofrotational mismatch between femoral and tibial componentsinKATKA is less frequent than inMATKA.Thisfindingcouldberelated with the results of the intraoperative kinematic studyby Maderbacher et al21 that reported more natural rotationalmovement of KA TKA compared with MA TKA. Besidesrotational alignments of the tibial and femoral components,various factors could affect rotational movement of tibia afterTKA. Therefore, further studies were necessary to clarify therelationships between rotational alignments of componentsand rotational movement of tibia.

Fig. 7 Comparison of patellar tilt angle between mechanicallyaligned (MA) and kinematically aligned (KA) total knee arthroplasty(TKA). (A) Decreased patellar tilt in MA TKA compared with preop-erative status; (B) Similar patellar tilt in KA TKA compared withpreoperative status.

Table 4 Comparison of intraoperative morphometric analysisbetween two groups

Anthropometricmeasurement

KA(n¼42)

MA(n¼126)

p-Value

Distal femurcutting surface (mm)

Zone A 14.8� 4.1 10.1�4.1 <0.05

Zone B 21.9� 5.1 23.4�5.0 <0.05

Zone C 48.2� 4.2 47.8�3.9 0.510

Zone D 60.1� 2.2 59.5�3.4 0.246

Zone E 68.8� 2.9 68.3�3.3 0.703

Mean difference between implant and distalfemoral cutting surface (mm)

Zone A 3.1� 4.3 7.2� 4.3 <0.05

Zone B 8.6� 4.1 7.2� 4.0 <0.05

Zone Aþ B 11.7� 6.2 14.4�5.9 <0.05

Zone C �3.2�2.3 �3.0�3.6 0.671

Zone D �4.3�3.7 �3.8�3.1 0.719

Zone E �5.2�3.9 �4.9�3.1 0.485

Abbreviations: KA, kinematically aligned; MA, mechanically aligned.Note: Values are presented asmean� standard deviation. The statisticalsignificance was set at p< 0.05.

Table 5 Comparison of clinical results of 2-year follow-upbetween two groups

KA(n¼42)

MA(n¼126)

p-Value

KS score knee 82.1� 6.4 80.2�6.7 0.529

Function 85�7.5 82.7�6.4 0.471

WOMAC scores

Total 20�7.9 16�7.6 0.428

Pain 2.8� 2.3 2� 1.3 0.424

Stiffness 0.8� 0.9 0.5� 0.8 0.370

Function 16.2� 5 15.1�4.5 0.586

SF-36 83.1� 6.3 83.5�8.2 0.921

ROM (degree)

6-monthextension

0 0.3� 1.3 0.083

Flexion 134.1�7.9 132.4�8.3 0.411

Final extension 0 0

Flexion 138.5�4.4 136.0�4.8 0.249

Abbreviations: HKA, hip-knee-ankle; KA, kinematically aligned; KS, KneeSociety; MA, mechanically aligned; MCS, mental component summary;PCS, physical component summary; ROM, range of motion; SF, ShortForm; WOMAC, Western Ontario and McMaster Universities.Note: Values are presented asmean� standard deviation. The statisticalsignificance was set at p< 0.05.



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

In the evaluation of patellofemoral kinematics, patella tiltangle was increased in KA TKA compared with MA TKA.However, patellar tilting angle in KA TKA was closer topreoperative status rather than that of MA TKA. Althoughmore internal rotation of femoral component in KA TKA couldincrease the risk of patellofemoral maltracking theoretically,recent studies on patellofemoral kinematics between KA andMA TKAs have reported the results against this assumption.Keshmiri et al22 reportedmorephysiologic patellar kinematicsin KA TKA compared with MA TKA similar with our results inpatellar tilting pattern. In a study by Koh et al,23 KA TKArestored patellar kinematics closer to normal knee comparedwith MA TKA. Different tibiofemoral kinematics or morelaterally positioned distal trochlear groove in KA TKA couldbe the reason of this phenomenon, and further study isnecessary to clarify this assumption.

The anthropometric measurement of distal femoralcutting surface might be changed according to character-istics of KA and MA. These results may be due to the relativeinternal rotation of femoral components in KATKA anduse ofthe posterior referencing system. MA TKA showed a cleargrand piano sign, whereas KA TKAwas closer to the butterflysign. Therewas no statistically significant difference in zonesC, D, and E; however, the length of distal femoral cuttingsurface tended to be longer than MA TKA in KA TKA. Theseresults were due to the valgus cutting of the distal femoralcondyle in KA TKA. In terms of mean difference betweenimplant and distal femoral cutting surface, zone A showedKA TKA that was less overhang than MA TKA and zone Bshowed KATKA that wasmore overhang thanMATKA. Theseresults are also due to the relative internal rotation of femoralcomponents in KA TKA. There was no statistically significantdifference in zones C, D, and E; however, themean differencebetween implant and distal femoral cutting surface tended tomore underhang thanMATKA in KA TKA. These results werealso due to the valgus cutting of the distal femoral condyle inKA TKA.

Limitations

This study has some limitations. First, in this study, KA andMATKAswere performedusingposterior and anterior referencingsystem, and referencing system can affect anterior femoral cutconfiguration. However, there was no definite notching oroverstuffing case in MA TKA. Therefore, we believe that theeffect of different referencing system may be minimal in thisstudy. Second, all MA TKAs were performed with posteriorstabilizing design. Therefore, the result of this study can bedifferent from the comparison between KA andMATKAswithcruciate retaining prostheses. However, considering that bonecuttingwasperformedwith identical surgical techniquewith-out influence of posterior cruciate ligament status in allgroups, comparison of coronal and rotational alignment canbe interpreted as difference between KA and MA TKAs. Third,our analysis was restricted to the alignment andmorphologicanalysis and other aspects, such as biomechanics and longevi-ty, were not considered. Our follow-up period is short todiscuss long-term survival and longevity.

Conclusion

KATKA showedmore parallel JLOA tofloor, closer patellar tiltto preoperative status, and better anterior flange fitting thatcan reproducemore natural knee kinematics comparedwithMA TKA. Although clinical outcomes assessed by conven-tional evaluating tools were similar between two groups,further evaluation focusing on the patellofemoral symptomsor unawareness of TKA is necessary to clarify the clinicalbenefit of KA TKA.

FundingNone.

Conflict of InterestNone declared.

References1 Poilvache PL, Insall JN, Scuderi GR, Font-Rodriguez DE. Rotational

landmarks and sizing of the distal femur in total knee arthro-plasty. Clin Orthop Relat Res 1996;(331):35–46

2 Miller MC, Berger RA, Petrella AJ, Karmas A, Rubash HE. Optimiz-ing femoral component rotation in total knee arthroplasty. ClinOrthop Relat Res 2001;(392):38–45

3 Kim JI, Jang J, Lee KW, Han HS, Lee S, LeeMC. Anterior tibial curvedcortex is a reliable landmark for tibial rotational alignment in totalknee arthroplasty. BMC Musculoskelet Disord 2017;18(01):252

4 Howell SM, Papadopoulos S, Kuznik K, Ghaly LR, Hull ML. Doesvarus alignment adversely affect implant survival and functionsix years after kinematically aligned total knee arthroplasty? IntOrthop 2015;39(11):2117–2124

5 Howell SM, Howell SJ, Kuznik KT, Cohen J, Hull ML. Does akinematically aligned total knee arthroplasty restore functionwithout failure regardless of alignment category? Clin OrthopRelat Res 2013;471(03):1000–1007

6 Yoon JR, Han SB, Jee MK, Shin YS. Comparison of kinematic andmechanical alignment techniques in primary total knee arthro-plasty: ameta-analysis.Medicine (Baltimore) 2017;96(39):e8157

7 Lee YS, Howell SM, Won YY, et al. Kinematic alignment is apossible alternative tomechanical alignment in total knee arthro-plasty. Knee Surg Sports Traumatol Arthrosc 2017;25(11):3467–3479

8 Guy SP, Farndon MA, Sidhom S, Al-Lami M, Bennett C, London NJ.Gender differences in distal femoral morphology and the role ofgender specific implants in total knee replacement: a prospectiveclinical study. Knee 2012;19(01):28–31

9 Kim YH, Choi Y, Kim JS. Comparison of standard and gender-specific posterior-cruciate-retaining high-flexion total kneereplacements: a prospective, randomised study. J Bone JointSurg Br 2010;92(05):639–645

10 Hutt J, Massé V, Lavigne M, Vendittoli PA. Functional joint lineobliquity after kinematic total knee arthroplasty. Int Orthop2016;40(01):29–34

11 Kim JH, Yoo BW, Kim CW. Influence of the rotational alignment ofthe femoral and patellar components on patellar tilt in total kneearthroplasty. Knee Surg Relat Res 2015;27(03):163–167

12 Castelli CC, Falvo DA, Iapicca ML, Gotti V. Rotational alignment ofthe femoral component in total knee arthroplasty. AnnTranslMed2016;4(01):4

13 Saffi M, Spangehl MJ, Clarke HD, Young SW. Measuring tibialcomponent rotation following total knee arthroplasty: what isthe best method? J Arthroplasty 2019;34(7S):S355–S360

14 Fong TS, Kim SC, Kim JE, Lee ES, Kim TW, Lee YS. Morphometricassessment of resected femoral cut surface in korean knees and its



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

fitting with western-designed femoral components. J Arthro-plasty 2019;34(09):1929–1937

15 Howell SM, Papadopoulos S, Kuznik KT, et al. Accurate alignmentand high function after kinematically aligned TKA performedwith generic instruments. Knee Surg Sports Traumatol Arthrosc2013;21(10):2271–2280

16 Paley D, Pfeil J. [Principles of deformity correction around theknee]. Orthopade 2000;29(01):18–38

17 Ji HM, Han J, Jin DS, Seo H,Won YY. Kinematically aligned TKA canalign knee joint line to horizontal. Knee Surg Sports TraumatolArthrosc 2016;24(08):2436–2441

18 MatsumotoT, Takayama K, Ishida K, et al. Radiological and clinicalcomparison of kinematically versus mechanically aligned totalknee arthroplasty. Bone Joint J 2017;99-B(05):640–646

19 Victor JM, Bassens D, Bellemans J, Gürsu S, Dhollander AA,Verdonk PC. Constitutional varus does not affect joint line orien-tation in the coronal plane. Clin Orthop Relat Res 2014;472(01):98–104

20 Nedopil AJ, Singh AK, Howell SM, Hull ML. Does calipered kine-matically aligned tka restore native left to right symmetry of thelower limb and improve function? J Arthroplasty 2018;33(02):398–406

21 Maderbacher G, Keshmiri A, Krieg B, Greimel F, Grifka J, Baier C.Kinematic component alignment in total knee arthroplasty leadsto better restoration of natural tibiofemoral kinematics comparedto mechanic alignment. Knee Surg Sports Traumatol Arthrosc2019;27(05):1427–1433

22 Keshmiri A, Maderbacher G, Baier C, Benditz A, Grifka J, Greimel F.Kinematic alignment in total knee arthroplasty leads to a betterrestoration of patellar kinematics compared to mechanic align-ment. Knee Surg Sports Traumatol Arthrosc 2019;27(05):1529–1534

23 Koh IJ, Park IJ, Lin CC, et al. Kinematically aligned total kneearthroplasty reproduces native patellofemoral biomechanics dur-ing deep kneeflexion. Knee Surg Sports Traumatol Arthrosc 2019;27(05):1520–1528



Thi

s do

cum

ent w

as d

ownl

oade

d fo

r pe

rson

al u

se o

nly.

Una

utho

rized

dis

trib

utio

n is

str

ictly

pro

hibi

ted.

Documents

Comparison of the Radiologic, Morphometric, and Clinical