Longitudinal Shapes of the Tibia and Femur are Unrelated and Variable

In general practice, short films of the knee are used to assess component position and define the entry point for intramedullary femoral alignment in TKAs; however, whether it is justified to use the short film commonly used in research settings and everyday practice as a substitute for the whole leg view is controversial and needs clarification. In 138 long leg CT scanograms we measured the angle formed by the anatomic axis of the proximal fourth of the tibia and the mechanical axis of the tibia, the angle formed by the anatomic axis of the distal fourth of the femur and the mechanical axis of the femur, the “bow” of the tibia (as reflected by the offset of the anatomic axis from the center of the talus), and the “bow” of the femur (as reflected by the offset of the anatomic axis from the center of the femoral head). Because the angle formed by these axes and the bow of the tibia and femur have wide variability in females and males, a short film of the knee should not be used in place of the whole leg view when accurate assessment of component position and limb alignment is essential. A previous study of normal limbs found that only 2% of subjects have a neutral hip-knee-ankle axis, which can be explained by the wide variability of the bow in the tibia and femur and the lack of correlation between the bow of the tibia and femur in a given limb as shown in the current study

Comparative assessment of bone pose estimation using point cluster technique and OpenSim

Estimating the position of the bones from optical motion capture data is a challenge associated with human movement analysis. Bone pose estimation techniques such as the Point Cluster Technique (PCT) and simulations of movement through software packages such as OpenSim are used to minimize soft tissue artifact and estimate skeletal position; however, using different methods for analysis may produce differing kinematic results which could lead to differences in clinical interpretation such as a misclassification of normal or pathological gait. This study evaluated the differences present in knee joint kinematics as a result of calculating joint angles using various techniques. We calculated knee joint kinematics from experimental gait data using the standard PCT, the least squares approach in OpenSim applied to experimental marker data, and the least squares approach in OpenSim applied to the results of the PCT algorithm. Maximum and resultant RMS differences in knee angles were calculated between all techniques. We observed differences in flexion/extension, varus/ valgus, and internal/external rotation angles between all approaches. The largest differences were between the PCT results and all results calculated using OpenSim. The RMS differences averaged nearly 5 for flexion/extension angles with maximum differences exceeding 15 . Average RMS differences were relatively small (< 1.08 ) between results calculated within OpenSim, suggesting that the choice of marker weighting is not critical to the results of the least squares inverse kinematics calculations. The largest difference between techniques appeared to be a constant offset between the PCT and all OpenSim results, which may be due to differences in the definition of anatomical reference frames, scaling of musculoskeletal models, and/or placement of virtual markers within OpenSim. Different methods for data analysis can produce largely different kinematic results, which could lead to the misclassification of normal or pathological gait. Improved techniques to allow non-uniform scaling of generic models to more accurately reflect subject-specific bone geometries and anatomical reference frames may reduce differences between bone pose estimation techniques and allow for comparison across gait analysis platforms

Discover your potential: The influence of kinematics on a muscle's ability to contribute to the sit-to-stand transfer.

Existing methods for estimating how individual muscles contribute to a movement require extensive time and experimental resources. In this study we developed an efficient method for determining how changes to lower extremity joint kinematics affect the potential of individual muscles to contribute to whole-body center-of-mass vertical (support) and anteroposterior (progression) accelerations. A 4-link 2-dimensional model was used to assess the effect of kinematic changes on muscle function. Joint kinematics were systematically varied throughout ranges observed during the momentum transfer phase of the sit-to-stand transfer. Each muscle's potential to contribute to support and progression was computed and compared to simulated potentials estimated by traditional dynamic simulation methods for young adults and individuals with knee osteoarthritis. The new method required 4-10s to compute muscle potentials per kinematic state and computed potentials were consistent with simulated potentials. The new method identified differences in muscle potentials between groups due to kinematic differences, particularly decreased anterior pelvic tilt in young adults, and revealed kinematic and muscle strengthening modifications to increase support. The methods presented provide an efficient, systematic approach to evaluate how joint kinematic adjustments alter a muscle's ability to contribute to movement and can identify potential sources of pathologic movement and rehabilitation strategies

Surgical Navigation Improves the Precision and Accuracy of Tibial Component Alignment in Canine Total Knee Replacement.

OBJECTIVE: The goal of this study was to determine whether computer-assisted surgical navigation improves the accuracy of tibial component alignment in canine total knee replacement (TKR). STUDY DESIGN: Retrospective radiographic review and prospective ex vivo study. SAMPLE POPULATION: Canine TKR radiographs (n = 17 sets) and canine cadaveric stifles (n = 12). METHODS: Radiographs from TKR surgical workshops were reviewed to determine the incidence and magnitude of tibial component malalignment. Tibial component alignment was compared after either standard ("surgeon-guided") component placement or computer-assisted ("navigation-guided") placement. Results were compared against the current recommendations of a neutral (0° varus-valgus) ostectomy in the frontal plane and 6° of caudal slope in the sagittal plane. A prospective cadaveric study was then undertaken by performing TKR in 12 canine stifle joints. RESULTS: Malalignment of >3° in the frontal and sagittal planes was identified in 12% and 24% of the radiographs from the retrospective review, respectively. Surgical navigation reduced both the mean error (P = .007) and the variability in frontal plane alignment (P < .001) as compared with surgeon-guided procedures. The mean error in sagittal plane alignment was not significantly different (P = .321), but variability in alignment was significantly lower when navigation was used (P = .008). CONCLUSION: Surgical navigation significantly improved accuracy and decreased variability in tibial component alignment in canine TKR. Clinical trials would be required to determine whether these improvements in surgical accuracy lead to better clinical outcomes in terms of joint function and a reduction in long-term implant wear.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/vsu.1242

Tibiofemoral Osteoarthritis and Varus–Valgus Laxity

The purpose of this study was to systematically review and synthesize the literature measuring varus–valgus laxity in individuals with tibiofemoral osteoarthritis (OA). Specifically, we aimed to identify varus–valgus laxity differences between persons with OA and controls, by radiographic disease severity, by frontal plane knee alignment, and by sex. We also aimed to identify if there was a relationship between varus–valgus laxity and clinical performance and self-reported function. We systematically searched for peer-reviewed original research articles in PubMed, Scopus, and CINAHL to identify all existing literature regarding knee OA and objective measurement of varus–valgus laxity in vivo. Forty articles were identified that met the inclusion criteria and data were extracted. Varus–valgus laxity was significantly greater in individuals with OA compared with controls in a majority of studies, while no study found laxity to be significantly greater in controls. Varus–valgus laxity of the knee was reported in persons with OA and varying degrees of frontal plane alignment, disease severity, clinical performance, and self-reported function but no consensus finding could be identified. Females with knee OA appear to have more varus–valgus laxity than males. Meta-analysis was not possible due to the heterogeneity of the subject populations and differences in laxity measurement devices, applied loading, and laxity definitions. Increased varus–valgus laxity is a characteristic of knee joints with OA. Large variances exist in reported varus–valgus laxity and may be due to differences in measurement devices. Prospective studies on joint laxity are needed to identify if increased varus–valgus laxity is a causative factor in OA incidence and progression

Quadriceps Femoris Strength and Sagittal-Plane Knee Biomechanics During Stair Ascent in Individuals With Articular Cartilage Defects in the Knee

Few objective data are available regarding strength and movement patterns in individuals with articular cartilage defects (ACDs) of the knee. To test the following hypotheses: (1) The involved limb of individuals with ACDs would demonstrate lower peak knee-flexion angle, peak internal knee-extension moment, and peak vertical ground-reaction force (vGRF) than the contralateral limb and healthy controls. (2) On the involved limb of individuals with ACDs, quadriceps femoris strength would positively correlate with peak knee-flexion angle, peak internal knee-extension moment, and peak vGRF. Cross-sectional. Biomechanics research laboratory. 11 individuals with ACDs in the knee who were eligible for surgical cartilage restoration and 10 healthy controls. Quadriceps femoris strength was quantified as peak isometric knee-extension torque via an isokinetic dynamometer. Sagittal-plane knee kinematics and kinetics were measured during the stance phase of stair ascent with 3-dimensional motion analysis. Quadriceps strength and knee biomechanics during stair ascent were compared between the involved and contralateral limbs of participants with ACD (paired t tests) and with a control group (independent-samples t tests). Pearson correlations evaluated relationships between strength and stair-ascent biomechanics. Lower quadriceps strength and peak internal knee-extension moments were observed in the involved limb than in the contralateral limb (P < .01) and the control group (P < .01). For the involved limb of the ACD group, quadriceps femoris strength was strongly correlated (r = .847) with involved-limb peak internal knee-extension moment and inversely correlated (r = -.635) with contralateral peak vGRF. Individuals with ACDs demonstrated deficits in quadriceps femoris strength with associated alterations in movement patterns during stair ascent. The results of this study are not comprehensive; further research is needed to understand the physiological characteristics, activity performance, and movement quality in this population