Impact of knee marker misplacement on gait kinematics of children with cerebral palsy using the Conventional Gait Model — a sensitivity study

Clinical gait analysis is widely used in clinical routine to assess the function of patients with motor disorders. The proper assessment of the patient’s function relies greatly on the repeatability between the measurements. Marker misplacement has been reported as the largest source of variability between measurements and its impact on kinematics is not fully understood. Thus, the purpose of this study was: 1) to evaluate the impact of the misplacement of the lateral femoral epicondyle marker on lower limb kinematics, and 2) evaluate if such impact can be predicted. The kinematic data of 10 children with cerebral palsy and 10 aged-match typical developing children were included. The lateral femoral epicondyle marker was virtually misplaced around its measured position at different magnitudes and directions. The outcome to represent the impact of each marker misplacement on the lower limb was the root mean square deviations between the resultant kinematics from each simulated misplacement and the originally calculated kinematics. Correlation and regression equations were estimated between the root mean square deviation and the magnitude of the misplacement expressed in percentage of leg length. Results indicated that the lower-limb kinematics is highly sensitive to the lateral femoral epicondyle marker misplacement in the anterior-posterior direction. The joint angles most impacted by the anterior-posterior misplacement were the hip internal-external rotation (5.3° per 10 mm), the ankle internal-external rotation (4.4° per 10 mm) and the knee flexion-extension (4.2° per 10 mm). Finally, it was observed that the lower the leg length, the higher the impact of misplacement on kinematics. This impact was predicted by regression equations using the magnitude of misplacement expressed in percentage of leg length. An error below 5° on all joints requires a marker placement repeatability under 1.2% of the leg length. In conclusion, the placement of the lateral femoral epicondyle marker in the antero-posterior direction plays a crucial role on the reliability of gait measurements with the Conventional Gait Model

Structures of (5′S)-8,5′-Cyclo-2′-deoxyguanosine Mismatched with dA or dT

pubs.acs.org/cr

Unexpected Role for Helicobacter pylori DNA Polymerase I As a Source of Genetic Variability

Helicobacter pylori, a human pathogen infecting about half of the world population, is characterised by its large intraspecies variability. Its genome plasticity has been invoked as the basis for its high adaptation capacity. Consistent with its small genome, H. pylori possesses only two bona fide DNA polymerases, Pol I and the replicative Pol III, lacking homologues of translesion synthesis DNA polymerases. Bacterial DNA polymerases I are implicated both in normal DNA replication and in DNA repair. We report that H. pylori DNA Pol I 5′- 3′ exonuclease domain is essential for viability, probably through its involvement in DNA replication. We show here that, despite the fact that it also plays crucial roles in DNA repair, Pol I contributes to genomic instability. Indeed, strains defective in the DNA polymerase activity of the protein, although sensitive to genotoxic agents, display reduced mutation frequencies. Conversely, overexpression of Pol I leads to a hypermutator phenotype. Although the purified protein displays an intrinsic fidelity during replication of undamaged DNA, it lacks a proofreading activity, allowing it to efficiently elongate mismatched primers and perform mutagenic translesion synthesis. In agreement with this finding, we show that the spontaneous mutator phenotype of a strain deficient in the removal of oxidised pyrimidines from the genome is in part dependent on the presence of an active DNA Pol I. This study provides evidence for an unexpected role of DNA polymerase I in generating genomic plasticity

Validation of a multi-body optimization with a knee model including deformable ligaments

Soft tissue artefact introduces large errors in the joint kinematics estimated from skin markers. Multi-body optimization (MBO) methods have been proposed to reduce these errors. However, the validation of MBO methods using spherical or hinge knee kinematic models showed their inefficiency to estimate accurately the in vivo kinematics [1, 2]. A knee kinematic model with deformable ligaments has been developed on the basis of a previously proposed parallel mechanism [3, 4]. The objective of the study is to validate the model-based kinematics obtained with a MBO method using this knee kinematic model, against the kinematics measured in-vivo by bone pins

Shoulder joint velocity during fastball pitching in baseball

The purpose of this study was to assess the rotation and translation velocity of the shoulder complex during fastball pitching in baseball. 8 pitchers from the Dutch AAA team performed each 3 fastball pitches. Their motion was recorded by an opto-electronic device. Kinematic computation was performed using the quaternion algebra. The results showed that the endo-rotation, depression and backward rotation velocity of the humerus at ball release are initiated by a translation of the scapular girdle in the forward and upward direction before ball release.Biomechatronics & Human-Machine ControlBiomechanical Engineerin

Elite athlete motor and loading actions on the upper limb in baseball pitching

In baseball, pitchers are the players that are most prone to injury. Most injuries occur at the elbow and shoulder of the throwing upper limb. It is widely accepted that understanding the loading in the joints during pitching is a key factor to prevent injuries. To deepen the understanding of the joint actions this study proposes to split the net joint actions into two part: the motor actions and the stability actions representing respectively the actions generating the joint motion and the actions maintaining the joint integrity. The actions represent the actions applied on the distal segment of the joint. Eight youth elite pitchers participated the study and performed 5 fastball pitches while equipped with skin markers. Three pitches per pitchers were used to compute the joint actions with an inverse dynamics method. The results indicate at the elbow a maximal elbow stability moment in adduction (52±5Nm) on the lower arm at maximal external rotation and a motor action in flexion (38±10Nm) during the acceleration phase. At maximal internal rotation the maximal stability shoulder loading occurred, with a pulling force of 520±80N, a downward force of -290±95N and a depression moment of 65±17Nm. The motor actions at the shoulder were mainly a forward force (93±46N) and an exorotation moment (24±12Nm) during the arm acceleration phase. This study suggest that the main action of the shoulder is to stabilise the joint, with a maximal load at maximal internal rotation, and that the main action at the elbow is avoiding hyperextension, with a critical phase at maximal external rotation. Further study is needed to link the stability actions to injury risk.Biomechatronics & Human-Machine ControlBiomechanical Engineerin

Influence of biomechanical models on joint kinematics and kinetics in baseball pitching

In baseball pitching, biomechanical parameters have been linked to ball velocity and potential injury risk. However, although the features of a biomechanical model have a significant influence on the kinematics and kinetics of a motion, this influence have not been assessed for pitching. The aim of this study was to evaluate the choice of the trunk and shoulder features, by comparing two models using the same input. The models differed in thoraco-humeral joint definition (moving or fixed with the thorax), joint centre estimation, values of the inertial parameters and computational framework. One professional pitcher participated in the study. We found that the different features of the biomechanical models have a substantial influence on the kinematics and kinetics of the pitchers. With a fixed thoraco-humeral joint the peak average thorax angular velocity was delayed and underestimated by 17% and the shoulder internal rotation velocity was overestimated by 7%. The use of a thoraco-humeral joint fixed to the thorax will lead to an overestimation of the rotational power at the shoulder and will neglect the power produced by the forward and upward translation of the shoulder girdle. These findings have direct implications for the interpretation of shoulder muscle contributions to the pitch.Biomechatronics & Human-Machine ControlBiomechanical Engineerin

Ball velocity and elbow loading in fastball pitching

Among baseball players, the pitchers are the most prone to injuries. These injuries occur mainly at the medial part of the elbow and at the shoulder. It is widely accepted that high joint loading are linked to overuse injury for repetitive motion. At maximal exo-rotation (MER), the elbow maximal abduction moment is predominantly counteracted by the ulnar collateral ligament and causes great stress on this structure. The aim of this study is to investigate the relationship between the elbow maximal abduction moment, ball velocity and technique. Thirteen elite pitchers participated in this study. Elbow maximal abduction moment was computed by an inverse dynamics method. Results indicate that the mean maximal abduction moment of the forearm on the upper arm was 41+-9Nm and can be reduced without hampering ball velocity by lowering the elbow flexion angle at MER.Biomechatronics & Human-Machine ControlBiomechanical Engineerin

Project FASTBALL Snel en blessurevrij leren werpen

Met een goede pitcher die snel kan werpen kun je honkbalwedstrijden winnen. Maar hoe wordt een pitcher goed? Hiervoor is inzicht nodig in de ontwikkeling en het aanleren van de werptechniek van talentvolle pitchers. Met dit inzicht kunnen we, met behulp van technische hulpmiddelen, onze pitchers naar een hoger niveau brengen