Session 8: Kinematics


  • Patients with knee osteoarthritis can be divided in subgroups based on tibiofemoral joint kinematic clustering of gait – An exploratory and dynamic radiostereometric study.

Emil Toft Petersen1,2,3, Søren Rytter3,4, Daan Koppens1,4, Jesper Dalsgaard1, Torben Bæk Hansen1,2, Nis Elbrønd Larsen5, Michael Skipper Andersen6, Maiken Stilling2,3,4

1 University Clinic for Hand, Hip and Knee Surgery, Holstebro Central Hospital.2 Department of Clinical Medicine, Aarhus University. 3 AutoRSA Research Group, Orthopeadic Research Unit

Aarhus University Hospital. 4 Department of Orthopaedic Surgery, Aarhus University Hospital. 5 Department of Radiology, Holstebro Central Hospital. 6 Department of Materials and Production, Aalborg University,

Introduction:  In an attempt to alleviate symptoms of the disease, patients with knee osteoarthrosis frequently alter their gait patterns. Understanding the underlying pathomechanics and identifying knee osteoarthrosis phenotypes is essential for improving treatments. We aimed to investigate altered kinematics in patients with knee osteoarthritis to identify subgroups.

Material and methods: Sixty-six patients with symptomatic knee osteoarthritis scheduled for total knee arthroplasty and 12 age-matched healthy volunteers with asymptomatic knees were included. We used k-means to separate the patients based on dynamic radiostereometric assessed knee kinematics. Ligament lesions, osteoarthritis score, and clinical outcome were assessed by magnetic resonance imaging, radiographs, and patient reported outcome measures, respectively.

Result: We identified four clusters that were supported by clinical characteristics. Compared with the healthy group; The flexion group (n=20): revealed increased flexion, greater adduction, and joint narrowing and consisted primarily of patients with medial osteoarthritis. The abduction group (n=17): revealed greater abduction, joint narrowing and included primarily patients with lateral osteoarthritis. The anterior draw group (n=10): revealed greater anterior draw, external tibial rotation, lateral tibial shift, adduction, and joint narrowing. This group was composed of patients with medial osteoarthritis, some degree of anterior cruciate ligament lesion and the greatest osteoarthritis score. The external rotation group (n=19): revealed greater external tibial rotation, lateral tibial shift, adduction, and joint narrowing while no anterior draw was observed. This group included primarily patients with medial collateral and posterior cruciate ligament lesions.

Interpretation and conclusion: Patients with knee osteoarthritis can, based on their gait patterns, be classified into four subgroups, which relate to their clinical characteristics. The findings add to our understanding of associations between disease pathology characteristics in the knee and the pathomechanics in patients with knee osteoarthritis. A next step is to investigate if patients in the pathomechanic clusters have different outcomes following total knee arthroplasty.

Keywords: Knee osteoarthritis, dynamic radiostereometry, kinematics, gait analysis, cluster, statistical parametric mapping.


  • Kinematical comparison between ultra-congruent and posterior-stabilized total knee arthroplasty: dynamic RSA study
  • Zinno Raffaele1, Bragonzoni Laura1, Di Paolo Stefano1, Bontempi Marco2, Alesi Domenico2, Pizza Nicola2, Zaffagnini Stefano1,2  1. University of Bologna, Bologna, Italy. 2. 2nd Orthopaedic and Traumatologic Clinic, IRCCS Istituto Ortopedico Rizzoli, Italy

Introduction: In primary total knee arthroplasty (TKA), the ultra-congruent (UC) design has been proposed as a possible alternative to posterior-stabilized (PS) design. Although the claimed advantages were the achievement of the same stability while sparing femoral bone stock for further revision and the reduction of the intraoperative complications, kinematical analyses showed conflicting results. The aim was to compare the in-vivo kinematics of PS and UC TKA.

Material and methods: A cohort of 16 randomly selected patients (8 PS Persona Zimmer, 8 UC Persona Zimmer; mean age 70.0 ± 7.3 years old) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9 months after TKA, during the execution of a sit-to-stand motor task. The anteroposterior (AP) translation of the femoral component and the AP translation of the Low Point (tibio-femoral contact point) of medial and lateral femoral compartments were compared through Student’s t test (p < 0.05).

Results: A significantly greater anterior translation of the femoral component was found for the PS group compared to the UC group, mainly to almost complete extension (p=0.017). Both groups showed a significantly greater anterior translation of the Low Point of the lateral compartment with respect to the medial one (PS: p=0.012, UC: p= 0.018). This was consistent with a medial-pivot pattern. Furthermore, a comparison of the anterior translation of the medial compartment between the PS group and the UC group was statistically significant and showed a greater excursion in the PS group (p= 0.001). The same pattern was observed for the lateral compartment (p=0.006).

Interpretation and Conclusions: The TKA designs evaluated showed comparable in-vivo kinematics in terms of medial pivot pattern, but differences in terms of absolute AP translation.

Further studies on larger samples are needed to understand the correlation between in-vivo implant kinematics and functional outcomes at long-term follow-up.

Keywords: Dynamic RSA, ultra-congruent TKA, posterior-stabilized TKA, knee kinematics


  • A positive correlation exists between intra- and post-operative kinematics of a Posterior Stabilized total knee arthroplasty: preliminary analysis

Alesi Domenico1, Zinno Raffaele2,Di Paolo Stefano2, Barone Giuseppe2, Pizza Nicola1, Bragonzoni Laura2

1. 2nd Orthopaedic and Traumatologic Clinic, IRCCS Istituto Ortopedico Rizzoli, Italy

2. University of Bologna, Bologna, Italy

Introduction: Since aberrant kinematics has been claimed as possible reason for dissatisfaction after Total Knee Arthroplasty (TKA), to detect specific kinematical patterns in unsatisfied patients it is crucial to improve their outcomes. Recently some kinematical patterns have been detected however the further step should be detect intra-operatively the “abnormal” patterns and to prevent it. To reach this goal it is necessary to merge different technologies in order to couple the intra-operative kinematics with the post-operative one.

The aim of this study is to compare the passive flexion-extension kinematics acquired intra-operatively during a TKA surgery and to compare it with the post-operative flexion-extension one acquired during a sit-to-stand motor task.

Material and method: A cohort of 25 patients has been prospectively recruited and underwent intraoperative kinematic assessment with a commercial navigation system before and after Posterior-Stabilized TKA implantation. So far 5 patients underwent the post-operative evaluation at minimum 9 months follow-up with model based Dynamic RSA during the execution of the sit-to-stand. A correlation analysis has been conducted between the varus-valgus rotations (deg) at 0° and 30° of flexion, the antero-posterior translations at 90° of flexion acquired intra operatively and varus-valgus and AP acquired post-operatively.

Results: Statistically significant correlation (p<0.05) was found for VV a 30° of flexion (r=0.78, strong), AP a 90° of flexion (r=0.83, strong), and VV at 0° of flexion (r=0.37, poor).

Interpretation and conclusion: The findings of the present study confirm that intra-operative and post-operative kinematical parameter are comparable, and that positive strong correlation exists between VV rotations at 30° and AP translations at 90°. As a consequence of this finding, the intra-operative kinematic data could be used to detect kinematic pattern that are typical of unsatisfied patients in the post-operative period and therefore correct it during the operation.

Keywords: RSA; Navigation; Kinematics;


  • Three month migration and inducible movement predict two year migration and interface radiolucency in a cemented glenoid primary total shoulder arthroplasty study

Martin Downing1,3, David Skipsey2, Tristan McMillan2, David Cairns2, GP Ashcroft1, and Kapil Kumar2. 1University of Aberdeen, Aberdeen, United Kingdom. 2NHS Grampian, Aberdeen, United Kingdom. 3Downing Imaging Limited, Aberdeen, United Kingdom.

Introduction: A theoretical cause of glenoid implant loosening in Total Shoulder Arthroplasty (TSA) is repetitive induced movement caused by eccentric loading. This study looks at the association of induced movements with two year clinical and radiostereometric results.

Materials and method: 15 patients underwent TSA for primary osteoarthritis with a press fit Affinis Short Stem humeral component, Bionit ceramic head and a Vitamys glenoid (Mathys, Switzerland) with peg cementation only. Tantalum markers were inserted into the scapula at surgery and glenoid implant during manufacture. Patients were imaged supine, arm relaxed at postop and six weeks, then additionally under 12N abduction load at 13, 26, 52 and 104 weeks. Movement of the glenoid implant was determined relative to the scapula and summarised to the MTPM of the markers in the pegs yielding a metric of cement interface stability. One and two year routine radiographs were assessed using Lazarus grading for radiolucency. Kendal Tau-b was used to assess correlations between inducible movement, migration and Lazarus scoring.

Results: Baseline MTPM was mean(SD) 0.58(0.37)mm at three months and 1.04(0.6)mm at one year. The rate of MTPM movement was 3.2(2.7)mm/year at three months reducing to 0.32(0.32)mm/year by two years. Inducible MTPM was 0.35(0.27)mm at 3 months, reducing to 0.17(0.19)mm by two years. Lazarus grade was mean 1.1 (range 0 to 3) at two years.

Baseline, rate and inducible MTPM at three and six months were highly correlated (P<0.01) with radiolucency, total migration and migration rate at one and two years. For later inducible MTPM these correlations were present but weaker.

Interpretation and Conclusion: These observations show the value of migration and inducible measurements in the first 3 to 6 months in predicting migration and clinical results at 2 years. This suggests early RSA assessment could be used as a clinical screening tool for TSA.


  • Kinematical patterns through Dynamic RSA reflected clinical outcomes improvement during at two years follow-up

    Bragonzoni Laura1
    , Zinno Raffaele1, Di Paolo Stefano1, Bontempi Marco2, Alesi Domenico2, Pizza Nicola2, Zaffagnini Stefano 1,2 1. University of Bologna, Bologna, Italy2. 2nd Orthopaedic and Traumatologic Clinic, IRCCS Istituto Ortopedico Rizzoli, Italy

Introduction: A new concept of total knee arthroplasty (TKA), the medial-stabilized (MS) knee prosthesis, has been developed trying to mimic distal femur and tibial plateau geometry, thus reproducing the natural knee motion. However, the relationship between knee motion and patients’ satisfaction is still unclear. The use dynamic radiostereometric analysis (RSA) could be useful in predicting the clinical outcomes through kinematical patterns.

The aim of the study was to evaluate the clinical outcomes and the kinematical pattern of the MS TKA during a two-follow-up period. We hypothesized that (1) an improvement in clinical outcomes and (2) coherent changes in kinematical patterns.

Material and methods: 10 patients were evaluated through clinical and functional scores evaluation (Knee Society Score -KSS, Womac, Oxford), and kinematically through dynamic RSA at minimum 9 months (FU1) and at 2 years (FU2) after MS-TKA, during the execution of a sit-to-stand. The clinical and kinematical differences were evaluated through Student’s t test (p < 0.05) and a correlation analysis between score improvement and kinematics was performed through the Pearson’s correlation coefficient r.

Results: A significantly greater (p < 0.001) anterior translation of the lateral compartment with respect to the medial one was found in both FU1 (medial 2.6 mm ± 0.8 mm, lateral 8.3 mm ± 2.8 mm) and FU2 (medial 1.4 mm ± 0.5 mm, lateral 7.3 mm ± 3.0 mm), thus resulting in a medial pivot pattern. Significant improvement of KSS clinical was found (delta 20.3, p=0.018), while the other scores remained stable. Significant correlations were found between KSS clinical improvement and laxity reduction, particularly with peak external rotation (r=0.47), peak anterior translation (r=0.62), varus-valgus rotation (r=0.75).

Interpretation and Conclusions: Clinical outcomes either improved or remained stable between FU1 and FU2 and a medial pivot pattern was confirmed. Laxity reduction evaluated through Dynamic RSA concretely reflected the patients’ clinical improvement.

Keywords: Dynamic RSA, medial-stabilized TKA, knee kinematics, clinical outcomes


  • Is there a difference in kinematics between a symmetrical and an asymmetrical TKA? Fluoroscopic analysis of movements in patients included in an RCT RSA trial

Lennard A. Koster1 MSc., Joris E. Meinardi1 MD, Bart L. Kaptein1 PhD, Enrike M.J. van der Linden-van der Zwaag1 PhD MD, Rob G.H.H. Nelissen1 PhD MD

1 Biomechanics and Imaging Group, Department of Orthopaedic Surgery, Leiden University Medical Center, Albinusdreef 2, P.O. Box 9600, 2300 RC, Leiden, the Netherlands.

Introduction: Total knee arthroplasty (TKA) aims to reduce pain and to restore normal knee kinematics: femoral roll-back during flexion and screw-home during final extension. An asymmetric tibia was designed to allow more femoral external rotation during flexion. The objective of this study is to compare the new TKA design on kinematics with those of a well-proven symmetric TKA.

Material and method: Subjects from a larger radiostereometry (RSA) randomized controlled trial performed step-up and lunge motions under fluoroscopic recording (16 asymmetric TKA (Persona PS) and 16 symmetric TKA (NexGen LPS, both ZimmerBiomet)). Model-based RSA software and custommade software were used to determine contact points (CP) and flexion angle (FA) between components to assess knee kinematics.

Results: During lunge, range of motions (ROM) of femoral rotation was 11.5 degrees (CI 10.3 – 12.8) and 7.7 degrees (CI 6.4 – 9.1) for the symmetric and asymmetric TKA respectively. FA ROM and medial and lateral CP translations were not different between TKA designs. CPs translated in AP-direction in the smaller flexion angles (rollback during flexion). The femur rotated during the entire movement either internally (step-up) or externally (lunge). In both movements, the positions of the CPs of the asymmetric TKR were generally more centered on the tibia. In addition, CP movements in relation to FA were smaller in the asymmetric TKR.

Interpretation and conclusion: The asymmetric TKR ought to allow more femoral external rotation. However, this study does not show different femoral internal/external rotations in relation to FA. Rather, femoral rotation ROM of the symmetric TKR is larger. Rollback, screw-home kinematics, associated with normal knee function, are present in both designs. CP locations of the asymmetric TKR are more centered on the tibia baseplate, possibly preventing unfavorable force transductions onto the tibia, that might cause component migration.

Keywords: Kinematics, Fluoroscopic analysis, TKA, Asymmetric design