Staircases are a frequently encountered obstacle in daily life, requiring individuals to navigate ascending and descending movements that place additional demands on the trunk and lower limbs compared to walking on level surfaces. Therefore, it is crucial to examine the biomechanical characteristics of the trunk and lower limbs in individuals with scoliosis during stair activity. The aim of this study was to investigate the biomechanical differences in trunk and lower limbs during daily stair activities between patients with scoliosis and a healthy population. Additionally, the study aimed to explore the relationship between trunk abnormalities and lower limb biomechanics, providing a clinical and objective assessment basis for scoliosis. The Qualisys system, based in Gothenburg, Sweden, was employed for data collection in this study, with a sampling frequency of 150 Hz. It captured the kinematics of the trunk and lower limbs, as well as the kinetics of the lower limbs during stair ascent and descent for both the 28 individuals with scoliosis and the 28 control participants. The results indicate that scoliosis patients demonstrated significantly higher asymmetry compared to the control group in various measures during ascent and decent. These include different parts of kinematics and kinetics. Scoliosis patients demonstrate noticeable variations in their movement patterns compared to the healthy population when engaging in stair activities. Specifically, during stair ascent, scoliosis patients exhibit a seemingly more rigid movement pattern, whereas descent is characterized by an unstable pattern.

Hip dislocation is one of the leading causes of failure and revision surgery for total hip arthroplasty. To reduce dislocation rates, lipped liners have been designed with an elevated portion of the rim, to increase jump distance and maintain greater contact area. While it has been documented that lipped liners help reduce dislocation, the objective of this study is to investigate whether lipped liners also help reduce smaller instances of hip micromotion, separation, and edge loading. This study uses an advanced three-dimensional preoperative planning tool to analyze 10 patients, each implanted with both a neutral and lipped liner. Patients within the simulation performed stance phase of gait, and each cup was implanted with the rotation center aligned with the preoperative acetabulum center as well as shifted medially by 2, 4, 6, 8, and 10 mm, yielding 120 total simulations. Specific postoperative outcomes-of-interest included specified component offset, resultant in vivo hip forces, hip separation, and contact area to evaluate edge loading. The planner predicted a reduction in hip separation and an increase in articulating contact area for when using a lipped liner compared to a neutral liner. Additionally, regardless of liner type, increases in hip separation corresponded to decreases in contact area, therefore resulting in edge loading of the liner. Together, this indicates that improper component alignment and offsets may lead to an increase in hip separation and edge loading, but the use of a lipped liner may provide improved stability and resistance to this micromotion.

Advancements in three-dimensional (3D) preoperative planning tools can offer surgeons and design engineers detailed feedback and additional opportunities for clinical advancements. The objective of this study is to use a 3D total hip arthroplasty preoperative planning tool to compare femoral component alignment for three different stem systems. The planning tool in this study used morphology data of femoral bones gathered from a CT database, seven from postoperative patients and 63 from statistical shape models (SSMs), to suggest specific implant sizes and optimal placements in 3D to match each specific bone model. Retrospective validations of predicted stem size and femoral version were first performed by comparing planner-chosen and surgeon-implanted stem sizes and version angles for the seven postoperative patients. Next, the alignment of three different stem systems was evaluated using bone models generated from SSMs, with a quantitative focus on component head positioning. In the validation study, the planner accurately selected stem size and orientation compared to the surgeon for all assessed subjects. In the stem evaluation, the three stem systems yielded different accuracies in component placement, with the newest stem system demonstrating the closest restoration of anatomical head center location. It is evident that new stem designs may have the potential for increased accuracy over their predecessors, demonstrating that new stem designs can offer improved intraoperative and postoperative alignment potential. The 3D preoperative planning tools can provide novel and reliable data to both surgeons and design engineers, which can ultimately improve clinical outcomes and future implant designs.

BACKGROUND: Little is known about knee mechanics and muscle control after augmented ACL repair. Our aim was to compare knee biomechanics and leg muscle activity during walking between the legs of patients 2 years after InternalBraceTM-augmented anterior cruciate ligament repair (ACL-IB) and between patients after ACL-IB and ACL reconstruction (ACL-R), and controls.
METHODS: Twenty-nine ACL-IB, 27 sex- and age-matched ACL-R (hamstring tendon autograft) and 29 matched controls completed an instrumented gait analysis. Knee joint angles, moments, power, and leg muscle activity were compared between the involved and uninvolved leg in ACL-IB (paired t-tests), and between the involved legs in ACL patients and the non-dominant leg in controls (analysis of variance and posthoc Bonferroni tests) using statistical parametric mapping (SPM, P < 0.05). Means and 95% confidence intervals (CI) of differences in discrete parameters (DP; i.e., maximum/minimum) were calculated.
RESULTS: Significant differences were observed in ACL-IB only in minimum knee flexion angle (DP: 2.4°, CI [-4.4;-0.5]; involved > uninvolved) and maximum knee flexion moment during stance (-0.07Nm/kg, CI [-0.13;-0.00]; involved < uninvolved), and differences between ACL-IB and ACL-R only in maximum knee flexion during swing (DP: 3.6°, CI [0.5;7.0]; ACL-IB > ACL-R). Compared to controls, ACL-IB (SPM: 0-3%GC, P = 0.015; 98-100%, P = 0.016; DP: -6.3 mm, CI [-11.7;-0.8]) and ACL-R (DP: -6.0 mm, CI [-11.4;-0.2]) had lower (maximum) anterior tibia position around heel strike. ACL-R also had lower maximum knee extension moment (DP: -0.13Nm/kg, CI [-0.23;-0.02]) and internal knee rotation moment (SPM: 34-41%GC, P < 0.001; DP: -0.03Nm/kg, CI [-0.06;-0.00]) during stance, and greater maximum semitendinosus activity before heel strike (DP: 11.2%maximum voluntary contraction, CI [0.1;21.3]) than controls.
CONCLUSIONS: Our results suggest comparable ambulatory knee function 2 years after ACL-IB and ACL-R, with ACL-IB showing only small differences between legs. However, the differences between both ACL groups and controls suggest that function in the involved leg is not fully recovered and that ACL tear is not only a mechanical disruption but also affects the sensorimotor integrity, which may not be restored after surgery. The trend toward fewer abnormalities in knee moments and semitendinosus muscle function during walking after ACL-IB warrants further investigation and may underscore the importance of preserving the hamstring muscles as ACL agonists.
METHODS: Level III, case-control study.
BACKGROUND: clinicaltrials.gov, NCT04429165 (12/06/2020).

It remains unclear to what extent the interosseous membrane (IOM) is affected through the whole range of motion (ROM) in posttraumatic deformities of the forearm. The purpose of this study is to describe the ligament- and bone-related factors involved in rotational deficit of the forearm. Through three-dimensional (3D) kinematic simulations on one cadaveric forearm, angular deformities of 5° in four directions (flexion, extension, valgus, varus) were produced at two locations of the radius and the ulna (proximal and distal third). The occurrence of bone collision in pronation and the linear length variation of six parts of the IOM through the whole ROM were compared between the 32 types of forearm deformities. Similar patterns could be observed among four groups: 12 types of deformity presented increased bone collision in pronation, 8 presented an improvement of bone collision with an increase of the mean linear lengthening of the IOM in neutral rotation, 6 had an increased linear lengthening of the IOM in supination with nearly unchanged bone collision in pronation and 6 types presented nearly unchanged bone collision in pronation with a shortening of the mean linear length of IOM in supination or neutral rotation. This kinematic analysis provides a better understanding of the ligament- and bone-related factors expected to cause rotational deficit in forearm deformity and may help to refine the surgical indications of patient-specific corrective osteotomy.

Proximal femur fractures in the elderly are associated with significant loss of independence, mobility, and quality of life. This prospective study aimed to: (1) investigate gait biomechanics in intertrochanteric fracture (ITF) patients (A1 and A2 AO/OTA) managed via femoral nailing at 6 weeks and 6 months postoperative and how these compared with similarly aged elderly controls; and (2) investigate whether femoral offset shortening (FOS) and lateral lag screw protrusion (LSP) were associated with changes in gait biomechanics at postoperative time points. Hip radiographs and gait data were collected for 34 patients at 6 weeks and 6 months postoperatively. Gait data were also collected from similarly aged controls. FOS and LSP were measured from radiographs. Joint angles, external moments, and powers were calculated for the hip, knee, and ankle and compared between time points in ITF patients and healthy controls using statistical parametric mapping. The relationship between radiographic measures with gait speed, step length, peak hip abduction, and maximum hip abduction moment was assessed using a Pearson correlation. External hip adduction moments and hip power generation improved in the first 6 months postoperative, but differed significantly from healthy controls during single limb stance. LSP showed a moderate correlation with maximum hip abduction moment at 6 weeks postoperative (r = -0.469, p = 0.048). These results provide new detail on functional outcomes after ITF and potential mechanisms that functional deficiencies may stem from. Lag screw prominence may be an important factor in maintaining functional independence and minimizing the risk of secondary falls after ITF in the elderly.

The aim of this study was to compare the kinematic and kinetic differences of the racket arm when balls were hit cross-court (CC) and down the line (DL) by topspin backhand. Eight elite female players participated and were instructed to hit the ball down the line and cross-court using a topspin backhand. Kinematic and kinetic data were collected. The results show that at the impact, participants had a greater wrist flexion angle in DL than CC (p = 0.017). The angular velocity of shoulder flexion (p = 0.038), shoulder abduction (p = 0.006) and thorax-pelvis internal rotation (p = 0.017) was faster when participants impacted the ball DL than CC. As for the joint kinetics, the shoulder external rotation moment was greater in CC than DL (p = 0.043). For a high-quality DL technique, it is important to exhibit a greater wrist flexion and have faster adduction and flexion in the shoulder, as well as faster internal rotation in thorax-pelvis, while having a smaller wrist flexion and more external rotation power in the shoulder are important to perform a CC at the impact. If these key and different factors of hitting CC and DL are ignored, it may lead to failure to complete a high-quality shot.

Obesity increases the risk of knee osteoarthritis (OA). Knee joint contact characteristics have been thought to provide insights into the pathogenesis of knee OA; however, the cartilage contact characteristics in individuals with obesity have not been fully described. We conducted cartilage-to-cartilage contact analyses through high-precision fluoroscopy imaging with subject-specific magnetic resonance cartilage models. Twenty-five individuals with obesity were recruited for this study, and previously published data consisted of eight nonobese individuals who were used as the comparator group. In both groups, knees were imaged by a dual fluoroscopic imaging system during treadmill walking, and the tibiofemoral cartilage contact locations were analyzed and described on the tibial plateau in the medial-lateral (ML) and anterior-posterior (AP) directions and on femoral condyle surfaces using contact angles in the sagittal plane and deviation angles in a plane perpendicular to the sagittal plane. On the medial tibial plateau, the ML contact locations in the individuals with obesity were located more medially than in the nonobese group throughout the stance phase. The medial plateau AP contact locations in individuals with obesity showed a different pattern compared with the nonobese group. The ML contact excursions on the medial plateau in the individuals with obesity were larger than in the nonobese group. These findings suggest that obesity affects the contact location mainly in the medial compartment, which explains, in part, the high prevalence of medial knee OA in the obese population.

Gait alterations after anterior cruciate ligament reconstruction (ACLR) are commonly reported and have been linked to posttraumatic osteoarthritis development. While knee gait alterations have been studied at several time points after ACLR, little is known about how these biomechanical variables change earlier than 6 months after surgery, nor is much known about how they differ over the entire stance phase of gait. The purpose of this study was to examine knee gait biomechanical variables over their entire movement pattern through stance at both 3 and 6 months after ACLR and to study the progression of interlimb asymmetry between the two postoperative time points. Thirty-five individuals underwent motion analysis during overground walking 3 (3.2 ± 0.5) and 6 (6.4 ± 0.7) months after ACLR. Knee biomechanical variables were compared between limbs and across time points through 100% of stance using statistical parametric mapping; this included a 2 × 2 (Limb × Time) repeated measures analysis of variance and two-tailed t-tests. Smaller knee joint angles, moments, extensor forces, and medial compartment forces were present in the involved versus uninvolved limb. Interlimb asymmetries were present at both time points but were less prevalent at 6 months. The uninvolved limb\'s biomechanical variables stayed relatively consistent over time, while the involved limb\'s trended toward that of the uninvolved limb. Statement of Clinical Significance: Interventions to correct asymmetrical gait patterns after ACLR may need to occur early after surgery and may need to focus on multiple parts of stance phase.

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). Surface electromyography(EMG) and marker-based motion capture recorded lower extremity muscle activity and kinematics of 22 healthy full-term infants (4.2±1.6 months, 13M/9F) during five conditions: Pavlik harness, Rhino brace, inward-facing soft-structured baby carrier, held in arms facing inwards, and a standard car seat. Mean filtered EMG signal, time when muscles were active, and hip position (angles) were calculated. Compared to the Pavlik harness, infants exhibited similar adductor activity (but lower hamstring and gluteus maximus activity) in the Rhino abduction brace, similar adductor and gluteus maximus activity (but lower quadriceps and hamstring activity) in the baby carrier, similar but highly variable muscle activity in-arms, and significantly lower muscle activity in the car seat. Hip position was similar between the baby carrier and the Pavlik harness. This novel infant biomechanics study illustrates the potential benefits of using inward-facing soft-structured baby carriers for healthy hip development and highlights the potential negative impact of using supine-lying container-type devices such as car seats for prolonged periods of time. Further study is needed to understand the full picture of how body position impacts infant musculoskeletal development.