Defining the segmental tension generated in a vertebral body tethering system for scoliosis.

Vertebral body tethering (VBT) uses a flexible tether affixed across the curve convexity with tension applied at each segment to treat scoliosis. Intraoperative tether tension may be achieved directly with a counter-tensioner or with an extension spring tube. The purpose of this study was to quantify the force generated with and without the extension spring tube using current FDA-approved VBT instrumentation, to understand the variation between surgeons using the same instrumentation, and to define the force range that is generated intra-operatively.

Commercial infant products influence body position and muscle use.

The musculoskeletal and motor development of infants is affected by their environment, which varies from being held, lying on a firm flat surface, to seated in various nursery products. Nursery products can alter the body position of infants, particularly the position of the head/neck and trunk, which may inhibit an infant's ability to breathe. With U.

Microstructure of the radial head: Insights into anatomical variations and implications for advanced interventions.

Appropriate management of radial head fractures is integral to prevent long-term consequences like chronic pain and loss of motion. Advanced imaging systems, like micro-computed tomography (μCT), are valuable for understanding radial head fracture patterns as they utilize micrometer scale resolution to define important parameters of bone health like cortical density and trabecular thickness. The purpose of this study was to identify and describe the structural morphology of the radial head utilizing μCT.

Porcine computational modeling to investigate developmental dysplasia of the hip.

While it is well-established that early detection and initiation of treatment of developmental dysplasia of the hip (DDH) is crucial to successful clinical outcomes, research on the mechanics of the hip joint during healthy and pathological hip development in infants is limited. Quantification of mechanical behavior in both the healthy and dysplastic developing joints may provide insight into the causes of DDH and facilitate innovation in treatment options. In this study, subject-specific three-dimensional finite element models of two pigs were developed: one healthy pig and one pig with induced dysplasia in the right hindlimb.

Mechanical environment influences muscle activity during infant rolling.

An infant's musculoskeletal and motor development is largely affected by their environment. Understanding how different mechanical environments affect an infant's 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.

How do babies roll? Identifying the coordinated movements of infant rolling through video compared to laboratory techniques.

Background: Rolling is an important developmental milestone for infants where identifying the coordinated movement patterns could facilitate the early identification of motor development delays. Current methods for identifying coordinated movements of rolling are limited to a laboratory setting and not feasible for clinicians.

Objective: To develop video-based methods in which six coordinated movements, previously defined through motion capture, can be identified through video alone.

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.

Kinematic Performance of Medial Pivot Total Knee Arthroplasty.

Background: Total knee arthroplasty (TKA) implants have continued to evolve to accommodate new understandings of knee mechanics. The medial-pivot implant is a newer design, which is intended to limit anterior-posterior translation in the medial compartment while allowing lateral compartment translation. However, evidence for a generalized medial-pivot characteristic across all activities is limited.

The Combined Influence of Infant Carrying Method and Motherhood on Gait Mechanics.

Postpartum mothers are susceptible to lumbopelvic pain which may be exacerbated by loading, like carrying their infant in arms and with baby carriers. Nulliparous women carrying infant mannequins may biomechanically mimic mother-infant dyad, but this has not been studied. The purpose of our study was to investigate biomechanical differences of 10 mothers carrying their infants and 10 nulliparous women carrying infant mannequins under 3 gait conditions: carrying nothing, carrying in arms, and carrying in a baby carrier (babywearing).

Ultrasonographic evaluation of infant hips in the Pavlik harness compared to body-worn commercial baby carriers.

While many factors contribute to development and subsequent correction of developmental hip dysplasia (DDH) in infants, hip positioning and muscle activity play a significant role. Lower-limb restrictive extension positions, such as with swaddling, are detrimental for hip development, and some baby gear leads to reduced lower limb muscle activity. Yet how baby gear impacts hip position during wear remains unclear.

Mmp13 deletion in mesenchymal cells increases bone mass and may attenuate the cortical bone loss caused by estrogen deficiency.

The protective effect of estrogens against cortical bone loss is mediated via direct actions on mesenchymal cells, but functional evidence for the mediators of these effects has only recently begun to emerge. We report that the matrix metalloproteinase 13 (MMP13) is the highest up-regulated gene in mesenchymal cells from mice lacking the estrogen receptor alpha (ERα). In sham-operated female mice with conditional Mmp13 deletion in Prrx1 expressing cells (Mmp13), the femur and tibia length was lower as compared to control littermates (Mmp13f.

The Influence of Knee Osteoarthritis on Spinopelvic Alignment and Global Sagittal Balance.

Osteoarthritis (OA) of the knee is thought to lead to a loss of lumbar lordosis (LL) as a compensation for knee flexion contracture. Changes in sagittal alignment are not limited to the lumbar spine and involve a complex interplay of alignment of the hip, pelvis, and spine. While spine-hip interactions have been previously explored, the influence of knee OA sagittal alignment parameters on spinopelvic alignment and global sagittal balance remains unexplored.

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

Unlabelled: 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.

Mechanical Analysis of 3 Posterior Fusion Assemblies Intended to Cross the Cervicothoracic Junction.

Study Design: This was a biomechanical comparison study.

Objective: The objective of this study is to evaluate the mechanical properties of 3 posterior spinal fusion assemblies commonly used to cross the cervicothoracic junction.

Summary Of Background: When posterior cervical fusions are extended into the thoracic spine, an instrumentation transition is often utilized.

Inter-Rater Reliability of Clinical Testing for Laxity After Knee Arthroplasty.

Background: The clinical examination for laxity has been considered a mainstay in evaluation of the painful knee arthroplasty, especially for the diagnosis of instability. More than 10 mm of anterior-posterior (AP) translation in flexion has been described as important in the diagnosis of flexion instability. The inter-observer reliability of varus/valgus and AP laxity testing has not been tested.

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.

Biomechanics of axial load transmission across the native human elbow.

Background: Elbow and forearm motion are thought to affect elbow load transmission, yet little empirical evidence exists to quantify the biomechanics.

Methods: Eight fresh-frozen human cadaver upper extremities were utilized. A 100 N axial force was applied across the elbow joint at elbow flexion angles of (0°, 30°, 60°, and 90°) and forearm rotation angles (0°, 45° supination, and 45° pronation).

Infant inclined sleep product safety: A model for using biomechanics to explore safe infant product design.

Over 450 adverse incidents have been reported in infant inclined sleep products over the past 17 years, with many infants found dead in both the supine and prone positions. The unique design of inclined sleep products may present unexplored suffocation risks related to how these products impact an infant's ability to move. The purpose of this study was to assess body movement and muscle activity of healthy infants when they lie supine and prone on different inclined sleep products.

Exploring infant hip position and muscle activity in common baby gear and orthopedic devices.

Infant positioning in daily life may affect hip development. While neonatal animal studies indicate detrimental relationships between inactive lower extremities and hip development and dysplasia, no research has explored infant hip biomechanics experimentally. This study evaluated hip joint position and lower extremity muscle activity of healthy infants in common body positions, baby gear, and orthopedic devices used to treat hip dysplasia (the Pavlik harness and the Rhino cruiserabduction brace).

Radiographic Findings in Flexion Instability after Total Knee Arthroplasty.

Flexion instability (FI) is one of the leading causes of knee pain and revision surgery. Generally, the biomechanical etiology is considered to be a larger flexion than extension gap. This may be due to mismatch of components sizes to the bone or malalignment.

Changes in kinematics, kinetics, and muscle activity in patients with lumbar spinal stenosis during gait: systematic review.

Background Context: Lumbar spinal stenosis (LSS) is one of the most common orthopaedic conditions and affects more than half a million people over the age of 65 in the US. Patients with LSS have gait dysfunction and movement deficits due to pain and symptoms caused by compression of the nerve roots within a narrowed spinal canal.

Purpose: The purpose of the current systematic review was to summarize existing literature reporting biomechanical changes in gait function that occur with LSS, and identify knowledge gaps that merit future investigation in this important patient population.

Changes in Mediolateral Postural Control Mechanisms During Gait After Total Knee Arthroplasty.

Background: Patients who have total knee arthroplasty (TKA) likely suffer from decreased postural stability because of postoperative changes in musculoskeletal structure and loss of proprioception. The purpose of this experimental biomechanical study was to determine if patients who have TKA improve their dynamic postural control during walking after TKA as compared with before TKA. The secondary purpose was to assess changes in postural control between post-TKA patients and healthy controls.

Supine lying center of pressure movement characteristics as a predictor of normal developmental stages in early infancy.

Background: Absent or abnormal fidgety movements in young infants are associated with subsequent diagnoses of developmental disorders such as cerebral palsy. The General Movement Assessment (GMA) is a qualitative clinical tool to visually identify infants with absent or abnormal fidgety movements associated with developmental stage, yet no quantitative measures exist to detect fidgety activity.

Objective: To determine whether a correlation exists between quantitative Center of Pressure (CoP) measurements during supine lying and age.

Effect of movement speed on lower and upper body biomechanics during sit-to-stand-to-sit transfers: Self-selected speed vs. fast imposed speed.

Preferred and fast speed sit-to-stand and stand-to-sit (STS) tests are prevalent in literature, but biomechanical changes between the different speeds of STS have never been studied. Understanding differences between these STS techniques will better inform experimental design for research assessing functional ability in clinical populations. The purpose of this study was to investigate the effect of different speeds of STS transfers on lower body and trunk kinematics and kinetics in healthy adults.

Management of Periprosthetic Joint Infection and Extensor Mechanism Disruption With Modular Knee Fusion: Clinical and Biomechanical Outcomes.

Background: Extensor mechanism disruption (EMD) combined with periprosthetic joint infection (PJI) after total knee arthroplasty are life-changing complications. The literature suggests many eventually receive above-knee amputation and lose ambulatory function. An alternative is modular knee fusion (KF), but little is known about its outcomes and biomechanical function.