Dataset Information

Tibio-Femoral Contact Force Distribution is Not the Only Factor Governing Pivot Location after Total Knee Arthroplasty.

ABSTRACT: Total knee arthroplasty aims to mimic the natural knee kinematics by optimizing implant geometry, but it is not clear how loading relates to tibio-femoral anterior-posterior translation or internal-external pivoting. We hypothesised that the point of pivot in the transverse plane is governed by the location of the highest axial force. Tibio-femoral loading was measured using an instrumented tibial component in six total knee arthroplasty patients (aged 65-80y, 5-7y post-op) during 5-6 squat repetitions, while knee kinematics were captured using a mobile video-fluoroscope. In the range of congruent tibio-femoral contact the medial femoral condyle remained approximately static while the lateral condyle translated posteriorly by 4.1?mm (median). Beyond the congruent range, the medial and lateral condyle motions both abruptly changed to anterior sliding by 4.6?mm, and 2.6?mm respectively. On average, both the axial loading and pivot position were more medial near extension, and transferred to the lateral side in flexion. However, no consistent relationship between pivoting and load distribution was found across all patients throughout flexion, with R2 values ranging from 0.00 to 0.65. Tibio-femoral kinematics is not related to the load distribution alone: medial loading of the knee does not necessarily imply a medial pivot location.

SUBMITTER: Trepczynski A

PROVIDER: S-EPMC6336768 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Tibio-Femoral Contact Force Distribution is Not the Only Factor Governing Pivot Location after Total Knee Arthroplasty.

Trepczynski A A Kutzner I I Schütz P P Dymke J J List R R von Roth P P Moewis P P Bergmann G G Taylor W R WR Duda G N GN

Scientific reports 20190117 1

Total knee arthroplasty aims to mimic the natural knee kinematics by optimizing implant geometry, but it is not clear how loading relates to tibio-femoral anterior-posterior translation or internal-external pivoting. We hypothesised that the point of pivot in the transverse plane is governed by the location of the highest axial force. Tibio-femoral loading was measured using an instrumented tibial component in six total knee arthroplasty patients (aged 65-80y, 5-7y post-op) during 5-6 squat repe ...[more]

PMID: 30655583

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Project description:PurposeStability in the sagittal plane, particularly regarding anterior cruciate ligament compensation, and postoperative functionality and satisfaction remain issues in total knee arthroplasty. Therefore, this prospective study compared the clinical outcomes between medial-pivot-based and posterior-stabilised total knee arthroplasty based on anterior translation and clinical scores.MethodsTo assess outcomes of total knee arthroplasty for varus osteoarthritis, the anterior translation distance of the tibia relative to the femur was measured at 30 and 60° of flexion using a KS measure Arthrometer at 6 months postoperatively. The 2011 Knee Society Score, Forgotten Joint Score, visual analogue scale for pain, and range of motion were assessed at 6 months and 1 year postoperatively. The correlations among each score, anterior translation distance, range of motion, and visual analogue scale score for pain were investigated.ResultsThe medial-pivot and posterior-stabilised groups comprised 70 and 51 patients, respectively. The medial-pivot group exhibited a significantly shorter anterior translation distance at 60° flexion than the posterior-stabilised group. Furthermore, the medial-pivot group achieved significantly better outcomes regarding the visual analogue scale for pain, 2011 Knee Society Score, and Forgotten Joint Score than the posterior-stabilised group. A significant negative correlation was observed between the anterior translation distance and the function score of the 2011 Knee Society Score, whereas a significant positive correlation was found between the anterior translation distance and flexion angle, and between the extension angle and score of the Forgotten Joint Score or 2011 Knee Society Score. Significant negative correlations were also found between the pain visual analogue scale and both the 2011 Knee Society Score and Forgotten Joint Score.ConclusionIn total knee arthroplasty for osteoarthritis, the medial-pivot group displayed a shorter anterior translation distance than the posterior-stabilised group at 6 months postoperatively. The visual analogue scale score for pain was also significantly lower in the medial-pivot group than that in the posterior-stabilised group at both 6 months and 1 year postoperatively. Because a correlation was observed between the anterior translation distance and the function score, medial-pivot-based total knee arthroplasty was considered to significantly improve postoperative function compared to posterior-stabilised total knee arthroplasty.

Project description:Statistical shape models (SSMs) are a well established computational technique to represent the morphological variability spread in a set of matching surfaces by means of compact descriptive quantities, traditionally called "modes of variation" (MoVs). SSMs of bony surfaces have been proposed in biomechanics and orthopedic clinics to investigate the relation between bone shape and joint biomechanics. In this work, an SSM of the tibio-femoral joint has been developed to elucidate the relation between MoVs and bone angular deformities causing knee instability. The SSM was built using 99 bony shapes (distal femur and proximal tibia surfaces obtained from segmented CT scans) of osteoarthritic patients. Hip-knee-ankle (HKA) angle, femoral varus-valgus (FVV) angle, internal-external femoral rotation (IER), tibial varus-valgus (TVV) angles, and tibial slope (TS) were available across the patient set. Discriminant analysis (DA) and logistic regression (LR) classifiers were adopted to underline specific MoVs accounting for knee instability. First, it was found that thirty-four MoVs were enough to describe 95% of the shape variability in the dataset. The most relevant MoVs were the one encoding the height of the femoral and tibial shafts (MoV #2) and the one representing variations of the axial section of the femoral shaft and its bending in the frontal plane (MoV #5). Second, using quadratic DA, the sensitivity results of the classification were very accurate, being all >0.85 (HKA: 0.96, FVV: 0.99, IER: 0.88, TVV: 1, TS: 0.87). The results of the LR classifier were mostly in agreement with DA, confirming statistical significance for MoV #2 (p = 0.02) in correspondence to IER and MoV #5 in correspondence to HKA (p = 0.0001), FVV (p = 0.001), and TS (p = 0.02). We can argue that the SSM successfully identified specific MoVs encoding ranges of alignment variability between distal femur and proximal tibia. This discloses the opportunity to use the SSM to predict potential misalignment in the knee for a new patient by processing the bone shapes, removing the need for measuring clinical landmarks as the rotation centers and mechanical axes.

Project description:The ideal local anesthetic regime for femoral nerve block that balances analgesia with mobility after total knee arthroplasty (TKA) remains undefined.We compared two volumes and concentrations of a fixed dose of ropivacaine for continuous femoral nerve block after TKA to a single injection femoral nerve block with ropivacaine to determine (1) time to discharge readiness; (2) early pain scores and analgesic consumption; and (3) functional outcomes, including range of motion and WOMAC scores at the time of recovery.Ninety-nine patients were allocated to one of three continuous femoral nerve block groups for this randomized, placebo-controlled, double-blind trial: a high concentration group (ropivacaine 0.2% infusion), a low concentration group (ropivacaine 0.1% infusion), or a placebo infusion group (saline 0.9% infusion). Infusions were discontinued on postoperative Day (POD) 2. The primary outcome was time to discharge readiness. Secondary outcomes included opioid consumption, pain, and functional outcomes. Ninety-three patients completed the study protocol; the study was halted early because of unanticipated changes to pain protocols at the host institution, by which time only 61% of the required number of patients had been enrolled.With the numbers available, the mean time to discharge readiness was not different between groups (high concentration group, 62 hours [95% confidence interval [CI], 51-72 hours]; low concentration group, 73 hours [95% CI, 63-83 hours]; placebo infusion group 65 hours [95% CI, 56-75 hours]; p = 0.27). Patients in the low concentration group consumed significantly less morphine during the period of infusion (POD 1, high concentration group, 56 mg [95% CI, 42-70 mg]; low concentration group, 35 mg [95% CI, 27-43 mg]; placebo infusion group, 48 mg [95% CI, 38-59 mg], p = 0.02; POD 2, high concentration group, 50 mg [95% CI, 41-60 mg]; low concentration group, 33 mg [95% CI, 24-42 mg]; placebo infusion group, 39 mg [95% CI, 30-48 mg], p = 0.04); however, there were no important differences in pain scores or opioid-related side effects with the numbers available. Likewise, there were no important differences in functional outcomes between groups.Based on this study, which was terminated prematurely before the desired sample size could be achieved, we were unable to demonstrate that varying the concentration and volume of a fixed-dose ropivacaine infusion for continuous femoral nerve block influences time to discharge readiness when compared with a conventional single-injection femoral nerve block after TKA. A low concentration of ropivacaine infusion can reduce postoperative opioid consumption but without any important differences in pain scores, side effects, or functional outcomes. These pilot data may be used to inform the statistical power of future randomized trials.Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Dataset Information

Tibio-Femoral Contact Force Distribution is Not the Only Factor Governing Pivot Location after Total Knee Arthroplasty.

Publications

Tibio-Femoral Contact Force Distribution is Not the Only Factor Governing Pivot Location after Total Knee Arthroplasty.

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