Kinematics of the stiff total knee arthroplasty

Total Knee Arthroplasty Kinematics Predict Patient-Reported Outcome Measures: Implications for Clinical Kinematic Examinations

BACKGROUND

A core tenet of total knee arthroplasty (TKA) is that achieving more natural kinematics will lead to superior patient outcomes. Yet this relationship has not been proven for large representative cohorts of TKA patients because accurately measuring 3-dimensional TKA kinematics is time-consuming and expensive. But advanced imaging systems and machine learning-enhanced analysis software will soon make it practical to measure knee kinematics preoperatively and postoperatively in the clinic using radiographic methods. The purpose of this study was to assess the reported relationships between TKA kinematics and outcomes and distill those findings into a proposal for a clinically practical protocol for a clinical kinematic exam.

METHODS

This study reviewed the recent literature relating TKA kinematics to patient outcomes. There were 10 studies that reported statistical associations between TKA kinematics and patient outcome scores utilizing a range of functional activities. We stratified these activities by the complexity of the radiographic examination to create a proposed examination protocol, and we generated a list of requirements and characteristics for a practical TKA clinical kinematic examination.

RESULTS

Given considerations for a clinically practical kinematic exam, including equipment, time and other resources, we propose 3 exam levels. With basic radiographs, we suggest studying single-leg stance in extension, lunge or squat, and kneeling. For fluoroscopic systems with X-ray pulses up to 20 ms, we propose chair-rise or stair ascent to provide additional dynamic information. For fluoroscopic systems with X-ray pulses of less than 10 ms, we propose rapid open-chain knee flexion-extension to simulate the highly dynamic swing phase of gait.

CONCLUSIONS

It is our hope that this proposed examination protocol spurs discussion and debate so that there can be a consensus approach to clinical examination of knee and TKA kinematics when the rapidly advancing hardware and software capabilities are in place to do so.

Can tibio-femoral kinematic and kinetic parameters reveal poor functionality and underlying deficits after total knee replacement? A systematic review

BACKGROUND

Extensive efforts have been made to understand joint kinematics and kinetics in total knee arthroplasty (TKA) in subjects with satisfactory outcomes during daily functional activities and clinical tests, but it remains unclear whether such movement characteristics hold the potential to indicate the underlying aetiology of unsatisfactory or bad TKA outcomes.

PURPOSE

To investigate which kinematic and kinetic parameters assessed during passive clinical tests and functional activities of daily living are associated with poor functionality and underlying deficits after total knee replacement.

METHODS

We focused on studies characterizing the kinematic or kinetic parameters of the knee joint that are associated with poor clinical outcome after TKA. Seventeen articles were included for the review, and kinematic and kinetic data from 719 patients with minimal follow up of 6 months were extracted and analyzed.

RESULTS

Passive posterior translation at 90°flexionexhibited good potential for differentiating stable and unstable TKAs. Anterior-posterior (A-P) translation of the medial condyle at 0-30° and 30-60° flexion, A-P translation of the lateral condyle at 60-90°during closed chain exercises, as well asknee extension moment during stair ascent and descent, knee abduction moment during stair descent, knee internal rotation moment and plantar flexion moment during walking, 2ndpeak ground reaction force during stair ascent and walkingshowed the greatest promise as functional biomarkers for a dissatisfied/poor outcome knee after TKA.

CONCLUSION

In this study, we systematically reviewed the state-of-the-art knowledge of kinematics and kinetics associated with functional deficits, and found 11 biomechanical parameters that showed promise for supportingdecision making in TKA.

What is the role of mental health in primary total knee arthroplasty?

BACKGROUND

Psychological distress has been associated with inferior scores for pain after total knee arthroplasty (TKA). However, its relationships with scores and arthrofibrosis after TKA remain unclear.

QUESTION/PURPOSES

The objectives of this study were (1) to assess patient-reported outcomes (PROs), including Knee Society (KS) scores, of those patients who developed arthrofibrosis and underwent manipulation and compare them with a control group; and (2) in patients with arthrofibrosis who underwent manipulation, to determine PROs and KS scores of those with psychological distress and those without it.

METHODS

During a 17-year period (August 1992 to October 2009), a total of 1952 TKAs were performed and included in our prospectively collected joint registry database; 1248 procedures had a postoperative followup of at least 2 years (mean, 5 years; range, 2-16 years). Among them, 57 knees (53 patients) developed arthrofibrosis and underwent manipulation under anesthesia after the index procedure. This group was compared with a matched group (by age, sex, race, and ethnicity) of 63 knees (58 patients) without arthrofibrosis. Demographics, preoperative and postoperative Quality of Well-Being scale (QWB-7), SF-36, WOMAC, and The KS knee and function scores were prospectively collected and retrospectively analyzed. Patients with <52 points on the SF-36 Mental Component Summary subscale were considered in psychological distress for all comparisons. Active knee flexion and KS range of motion (ROM) were used as objective motion measures. Minimum followup was 2 years (mean, 5 years; range, 2-16 years).

RESULTS

Patients who developed arthrofibrosis had worse KS function scores before TKA than did patients in the nonarthrofibrosis control group (mean 27, SD 20.5 versus 37, SD 19.3; p=0.006). Patients with arthrofibrosis and psychological distress, before TKA and when compared with patients with arthrofibrosis but without distress, had worse QWB-7 (0.490 versus 0.547; p<0.001) and worse WOMAC stiffness (4.92, versus 3.22; p=0.005), respectively. Postoperatively, patients with arthrofibrosis and distress also had worse QWB-7 (0.537 versus 0.627; p=0.002).

CONCLUSIONS

Patients with arthrofibrosis and psychological distress perceived themselves preoperatively as having worse knee and overall health status than those with arthrofibrosis but without distress. In view of this, expectations after TKA should be particularly addressed in those patients with poor function and psychological distress. Further investigations, making use of tools specifically designed to ascertain depression, are warranted.

LEVEL OF EVIDENCE

Level III, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.

Geometric variable designs of cam/post mechanisms influence the kinematics of knee implants

PURPOSE

Reproducing the femoral rollback through specially designed mechanism in knee implants is required to achieve full knee function in total knee arthroplasty. Most contemporary implants use cam/post mechanism to replace the function of Posterior Cruciate Ligament. This study was aimed to determine the most appropriate cam and post designs to produce normal femoral rollback of the knee.

METHODS

Three different cams (triangle, ellipse, and circle) and three different posts (straight, convex, concave) geometries were considered in this study and were analysed using kinematic analyses. Femoral rollback did not occur until reaching 50° of knee flexion. Beyond this angle, two of the nine combinations demonstrate poor knee flexion and were eliminated from the study.

RESULTS

The combination of circle cam with concave post, straight post and convex post showed 15.6, 15.9 and 16.1 mm posterior translation of the femur, respectively. The use of ellipse cam with convex post and straight post demonstrated a 15.3 and 14.9 mm femoral rollback, whilst the combination of triangle cam with convex post and straight post showed 16.1 and 15.8 mm femoral rollback, respectively.

CONCLUSION

The present study demonstrates that the use of circle cam and convex post created the best femoral rollback effect which in turn produces the highest amount of knee flexion. The findings of the study suggest that if the design is applied for knee implants, superior knee flexion may be possible for future patients.

LEVEL OF EVIDENCE

IV.

In vivo knee kinematics in patients with bilateral total knee arthroplasty of 2 designs

Many younger and highly active patients desire to achieve high flexion after total knee arthroplasty. This study's purpose was to determine if a contemporary total knee arthroplasty design improved functional knee flexion compared with a traditional total knee arthroplasty in patients living a Western lifestyle. Ten patients with bilateral total knee arthroplasty of 2 types were studied during weight-bearing lunge, kneeling, and stair activities using fluoroscopic imaging. There were no differences in maximum knee flexion during lunging or kneeling. Statistically significant differences in tibial rotation and condylar translation were observed during the 3 activities. Although several joint kinematic differences were observed, no important functional differences were observed in clinically excellent, high performing subjects with bilateral total knee arthroplasty of 2 types.