Effects of Weight-Bearing on Tibiofemoral, Patellofemoral, and Patellar Tendon Kinematics in Older Adults

Quantification of natural knee kinematics is essential for the assessment of joint function in the diagnosis of pathologies. Combined measurements of tibiofemoral and patellofemoral joint kinematics are necessary because knee pathologies, such as progression of osteoarthritis and patellar instability, are a frequent concern in both articulations. Combined measurement of tibiofemoral and patellofemoral kinematics also enables calculation of important quantities, specifically patellar tendon angle, which partly determines the loading vector at the tibiofemoral joint and patellar tendon moment arm. The goals of this research were to measure the differences in tibiofemoral and patellofemoral kinematics, patellar tendon angle (PTA), and patellar tendon moment arm (PTMA) that occur during non-weight-bearing and weight-bearing activities in older adults. Methods: High-speed stereo radiography was used to measure the kinematics of the tibiofemoral and patellofemoral joints in subjects as they performed seated, non-weight-bearing knee extension and two weight-bearing activities: lunge and chair rise. PTA and PTMA were extracted from the subject’s patellofemoral and tibiofemoral kinematics. Kinematics and the root mean square difference (RMSD) between non-weight-bearing and weight-bearing activities were compared across subjects and activities. Results: Internal rotation increased with weight-bearing (mean RMSD from knee extension was 4.2 ± 2.4° for lunge and 3.6 ± 1.8° for chair rise), and anterior translation was also greater (mean RMSD from knee extension was 2.2 ± 1.2 mm for lunge and 2.3 ± 1.4 mm for chair rise). Patellar tilt and medial–lateral translation changed from non-weight-bearing to weight-bearing. Changes of the patellar tendon from non-weight-bearing to weight-bearing were significant only for PTMA. Conclusions: While weight-bearing elicited changes in knee kinematics, in most degrees of freedoms, these differences were exceeded by intersubject differences. These results provide comparative kinematics for the evaluation of knee pathology and treatment in older adults

DOES HAND SPEED RELATE TO CLUB HEAD SPEED OR BALL SPEED DURING A GOLF SWING?

Many golf swing analyses use club or ball speed to indicate performance, although these are difficult to obtain using motion capture. This study examined the relationship between hand speed and club head and ball speeds to examine if hand can indicate performance and if different capturing frequencies affect these relationships. A 10-camera Vicon system recorded golfers performing eight golf swings (500 Hz n=11, 100 Hz n=15). A TrackMan system recorded club head and ball speed. The resultant hand speed was calculated at peak velocity, the lowest position of the hands, and at ball impact. Hand speed at ball impact and club head speed had the strongest relationship (r=0.501, p\u3c0.001), though most correlations were r\u3c0.400. Higher capturing frequency had better relationships with the performance outcomes, and the ball impact was the best time point for analysis

Effect of follower load on motion and stiffness of the human thoracic spine with intact rib cage

Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive follower preload. However, dynamic mechanical testing using both the rib cage and follower load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive follower preloads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and follower preload. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a follower load, and (ii) neutral and elastic zone stiffness will be increased with a follower load. Eight human cadaveric thoracic spine specimen (T1–T12) with intact rib cage were subjected to 5 Nm pure moments in lateral bending, flexion/extension, and axial rotation under follower loads of 0–400 N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with follower load for every mode. Application of a follower load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing

Effects of follower load and rib cage on intervertebral disc pressure and sagittal plane curvature in static tests of cadaveric thoracic spines

The clinical relevance of mechanical testing studies of cadaveric human thoracic spines could be enhanced by using follower preload techniques, by including the intact rib cage, and by measuring thoracic intervertebral disc pressures, but studies to date have not incorporated all of these components simultaneously. Thus, this study aimed to implement a follower preload in the thoracic spine with intact rib cage, and examine the effects of follower load, rib cage stiffening and rib cage removal on intervertebral disc pressures and sagittal plane curvatures in unconstrained static conditions. Intervertebral disc pressures increased linearly with follower load magnitude. The effect of the rib cage on disc pressures in static conditions remains unclear because testing order likely confounded the results. Disc pressures compared well with previous reports in vitro, and comparison with in vivo values suggests the use of a follower load of about 400 N to approximate loading in upright standing. Follower load had no effect on sagittal plane spine curvature overall, suggesting successful application of the technique, although increased flexion in the upper spine and reduced flexion in the lower spine suggest that the follower load path was not optimized. Rib cage stiffening and removal both increased overall spine flexion slightly, although with differing effects at specific spinal locations. Overall, the approaches demonstrated here will support the use of follower preloads, intact rib cage, and disc pressure measurements to enhance the clinical relevance of future studies of the thoracic spine

Rolling from Home: Developing a Methodology for Classifying Infant Rolling Movements from At-Home Videos

Rolling from a supine to a prone position marks an important developmental milestone for babies. A previous study identified that babies use six distinct movement patterns to achieve this key motor skill. While previous studies have observed baby rolling patterns in lab settings, such conditions have limitations. First, labs are unnatural rolling environments that may not simulate how a baby rolls at home. Second, lab studies make it harder for researchers to track babies’ rolling patterns over time, limiting data collection to scheduled lab sessions. Using at-home video recorded by an infant’s caretaker could be a promising way to study baby rolling movements as an infant develops. Accurately classifying rolling patterns seen on video according to the six preestablished roll types is crucial to assessing how movement patterns change over time. In this study, we aim to present a methodology that will allow researchers to accurately and consistently categorize baby rolling patterns via at-home video analysis. The methodology developed consisted of three steps: 1) identifying the direction of the roll, 2) identifying stationary and moving limbs, and 3) determining the synchronicity of moving limbs. Detailed descriptions of each roll type as well as illustrations of how each roll type is executed were presented to aid the viewer in categorizing videos into the six roll types. Preliminary tests suggest this methodology has the potential to produce consistent results, although further work will address what improvements can be made to increase accuracy and consistency among those analyzing videos. Obtaining consistent results from at-home video analysis will enable researchers to expand their understanding of rolling patterns as they occur under natural conditions and to study how these movements progress over time

Postural Control Differences Between Patients with Posterior Tibial Tendon Dysfunction and Healthy People During Gait

Background: Patients with posterior tibial tendon dysfunction (PTTD) may exhibit postural instability during walking likely due to a loss of medial longitudinal arch, abnormal foot alignment, and pain. While many studies have investigated gait alterations in PTTD, there is no understanding of dynamic postural control mechanisms in this population during gait, which will help guide rehabilitation and gait training programs for patients with PTTD. The purpose of the study was to assess dynamic postural control mechanisms in patients with stage II PTTD as compared to age and gender matched healthy controls. Methods: Eleven patients with stage II PTTD (4 males and 7 females; age 59 ± 1 years; height 1.66 ± 0.12 m; mass 84.2 ± 16.0 kg) and ten gender and age matched controls were recruited in this study. Participants were asked to walk along a 10 m walkway. Ten Vicon cameras and four AMTI force platforms were used to collect kinematic and center of pressure (COP) data while participants performed gait. To test differences between PTTD vs. control groups, independent t-tests (set at α \u3c 0.05) were performed. Results: Patients with PTTD had significantly higher double stance ratio (+23%) and anterior-posterior (AP) time to contact (TTC) percentage (+16%) as compared to healthy control. However, PTTD had lower AP COP excursion (−19%), AP COP velocity (−30%), and medial-lateral (ML) COP velocity (−40%) as compared to healthy controls. Mean ML COP trace values for PTTD were significantly decreased (−23%) as compared to controls, indicating COP trace for PTTD tends to be closer to the medial boundary than controls during single-support phase of walking. Conclusion: PTTD patients showed more conservative and cautious postural strategies which may help maintain balance and reduce the need for postural adjustment during PTTD gait. They also showed more medially shifted COP patterns than healthy controls during single-support phase of walking. Dynamic postural control outcomes could be used to develop effective gait training programs aimed at alleviating a medial shift of COP (everted foot) for individuals with PTTD in order to improve their functionality and gait efficiency

Patellofemoral Kinematics in Healthy Older Adults During Gait Activities

The patellofemoral (PF) joint is susceptible to many pathologies resulting from acute injury, chronic disease and complications following surgical treatment of the knee. The objectives of this study were to describe case series measurements of patellar motion in healthy older adults as they performed three gait activities, determine patellar tendon angle and moment arm, and show if these quantities were activity dependent. A stereo radiography system was utilized to obtain the 3D PF kinematics of seventeen healthy people over 55 years of age (8F/9M, 66 ± 7.9 years old, 75.7 ± 20.5 kg) as they performed level walking, a step down, and a pivot turn. For a similar portion of the gait cycle, patellar flexion (6.2° ± 5.8) and average range of motion (ROM) (11.0° ± 5.9°) for walking with a step down was greater compared to the other gait activities (gait ROM 6.9° ± 4.3°, pivot ROM 5.7° ± 3.3°), while the average range of motion for patella tilt was greater during walking with a pivot turn (8.6° ± 3.9°). However, each subject displayed distinct PF kinematic trends during all activities with a few notable exceptions. Importantly, the knee extensor mechanism characteristics of patellar tendon angle and moment arm showed considerable variation across subjects but were largely unaltered by changing activities. The variation between subjects and the different behavior of the patella during the step down and pivot emphasized the need for analysis of a range of activities to reveal individual response to pathology and treatment in patellar maltracking and osteoarthritis

Muscle Activation and Coordinated Movements of Infant Rolling

Rolling is a critical step of infant development, encouraging muscle coordination and enabling independent exploration. Understanding muscle activity during infant rolling movements on a flat surface is necessary to more fully characterize how the rolling milestone is achieved. The purpose of this study was to determine infants’ muscle activation throughout roll initiation for six previously established coordinated movements. Thirty-eight healthy infants (age: 6.5 ± 0.7 months; 23M/15F) were enrolled in this IRB-approved in-vivo biomechanics study. Surface electromyography sensors recorded muscle utilization from the erector spinae, abdominal muscles, quadriceps, and hamstrings while infants rolled. Each rolling movement was categorized as one of six roll types, and the mean muscle activity was analyzed. All roll types required initial activation of all measured muscle groups. Movements featuring axial rotation of the torso relative to the pelvis required highly active erector spinae muscles. Movements featuring trunk and hip flexion required highly active abdominal muscles. Infants used distinct coordinated muscle activations to achieve the six different roll types on a flat surface. A foundational understanding of the different muscle activation patterns required during infant rolling will provide crucial insight into motor development. This study quantified muscle coordination required of infants to achieve rolling on a firm flat surface. Previous research indicates that the mechanical environment in which an infant is placed impacts muscle activity and body position during normal lying. Therefore, future work should explore if mechanical environments that differ from a flat and firm surface also influence these coordinated movements and muscle activations

Mechanical Environment Influences Muscle Activity During Infant Rolling

An infant\u27s musculoskeletal and motor development is largely affected by their environment. Understanding how different mechanical environments affect an infant\u27s movements and muscle use is necessary to inform the juvenile products industry and reduce incidents involving inclined nursery products each year. The purpose of this study was to determine how the coordinated movements and corresponding muscle activation patterns are affected by different mechanical environments, specifically the back incline angle. Thirty-eight healthy infants (age: 6.5 ± 0.7 months; 23 M/15 F) were enrolled in this IRB-approved in-vivo biomechanics study. Surface electromyography sensors recorded muscle activity of the erector spinae, abdominal muscles, quadriceps, and hamstrings while infants rolled in five different mechanical environments: a flat surface and four device configurations representing a range of inclines infants are commonly exposed to. Coordinated movements were determined using video. In all configurations featuring an inclined seatback angle, infants experienced significantly higher erector spinae muscle activation and significantly lower abdominal muscle activation compared to the flat surface. Infants also exhibited a different coordinated movement featuring spinal extension and a pelvic thrust in the inclined device configurations that was not previously observed on the flat surface alone. Understanding how infants coordinate their movements and use their muscles during rolling in different inclined environments provides more insight into motor development and may inform the juvenile products industry. Many factors impact an infant\u27s movements, therefore future work should explore how other environmental interactions influence an infant\u27s movements and muscle activation, particularly for rolling

Kinematic and Kinetic Changes After Total Hip Arthroplasty During Sit-to-Stand Transfers: Systematic Review

Background: Total hip arthroplasty (THA) is a common and effective surgical procedure that allows patients with hip osteoarthritis to restore functional ability and relieve pain. Sit-to-stand transfers are common demanding tasks during activities of daily living and are performed more than 50 times per day. The purpose of this systematic review is to obtain a comprehensive understanding of biomechanical changes during sit-to-stand transfers after THA. Methods: Relevant articles were selected through MEDLINE, Scopus, Embase, and Web of Science. Articles were included if they met the following inclusion criteria: 1) participants underwent total hip arthroplasty without restriction on the arthroplasty design, 2) involved either kinematic or kinetic variables as the primary outcome measure, 3) evaluated sit-to-stand, and 4) were written in English. Results: A total of 11 articles were included in the current systematic review. The THA group exhibited altered movement patterns as compared to healthy controls. Improvement in loading asymmetry was found up to 1 year after THA, but other kinetic changes indicate intensified contralateral limb loading. Limb differences were apparent, but whether these differences persist over 10 months after THA is still unknown. Conclusion: Despite the inevitable changes in kinematics and kinetics in sit-to-stand transfers after THA, it appears to be important to resolve asymmetrical loading between the operative and nonoperative limbs to minimize risk for subsequent joint problems