The conventional gait model,an open-source implementation that reproduces the past but prepares for the future

BackgroundThe Conventional Gait Model (CGM), known by a variety of different names, is widely used in clinical gait analysis. We present pyCGM2, an open-source implementation of the CGM with two versions. The first, CGM1.0, is a clone of Vicon Plug In Gait (PiG) with all its variants. CGM1.0 provides a platform to test the effect of modifications to the CGM on data collected and processed retrospectively or to provide backward compatibility.The second version, CGM1.1, offers some practical modifications and includes three well documented improvements.Research questionHow do improvements of the conventional gait model affect joint kinematics and kinetics?MethodThe practical modifications include the possibility to use a medial knee epicondyle marker, during static calibration only, to define the medio-lateral axis of the femur in place of the knee alignment device. The three improvements correspond to the change of pelvis angle decomposition sequence, the adoption of a single tibia coordinate system, and the default decomposition of the joint moments in the joint coordinate system. We validated the outputs of version CGM1.0 against Vicon-PiG, and estimated the effect of the modifications included in version CGM1.1 using gait data collected in 16 healthy participants.ResultsKinematics and kinetics of CGM1.0 were superimposed with that of Vicon-PiG, with root mean square differences less than 0.04° for kinematics and less than 0.05 N.m.kg-1 for kinetics.SignificanceThe differences between the CGM1.1 and CGM1.0 were minimal in the healthy participant cohort but we discussed the expected difference in participants with different gait pathologies.We hope that the pyCGM2 will facilitate the systematic testing and the use of improved processing methods for the conventional gait model.     

社区老年人双重任务行走步态特征与跌倒的关系研究

目的探索社区老年人双重任务行走步态参数与过去一年跌倒史的关系。方法方便抽取135名社区老年人,根据过去一年有无跌倒史分为跌倒组(23名)与未跌倒组(112名)。运用问卷和便携式步态分析仪分别采集老年人一般信息、健康资料与10m双重任务行走步态参数。结果两组居住方式、家庭人均月收入及TUGT比较,差异有统计学意义(均P0.05);两组单脚支撑时间、单脚支撑时间/双脚支撑时间、步幅持续时间、周期时间、地面冲击、落脚强度、离地时脚的角度、速度与步频比较,差异有统计学意义(P0.05,P0.01)。结论双重任务行走时步态性能较差的社区老年人易发生跌倒。政府应加强公共活动场所的安全基础建设,鼓励老年人加强腿部肌肉锻炼和双重任务训练;医务人员应重视对老年患者步态的评估和功能锻炼,提高老年人行走能力,以预防跌倒发生。     

Dynamics of quadrupedal locomotion of monkeys: implications for central control

We characterized the three-dimensional kinematics and dynamics of quadrupedal gait of young adult rhesus and cynomolgus monkeys while they walked with diagonal and lateral gaits at 0.4–1.0 m/s on a treadmill. Rigid bodies on the wrist, ankle, and back were monitored by an optical motion detection system (Optotrak). Kinematic data could be normalized using characteristic stride length, reducing variance due to different gait styles, to emphasize common characteristics of swing and stance parameters among animals. Mean swing phase durations fell as walking speed increased, but the swing phase durations increased at each walking velocity as a linear function of increases in amplitude, thereby following a main sequence relationship. The phase plane trajectories of the swing phases, i.e., plots of the relation of the rising and falling limb velocity to limb position in the sagittal (X–Z) plane, had unique dynamic characteristics. Trajectories were separable at each walking velocity and increases in swing amplitude were linearly related to peak swing velocities, thus comprising main sequences. We infer that the swing phase dynamics are set by central neural mechanisms at the onset of the swing phases according to the intended amplitude, which in turn is based on the walking velocity in the stance phases. From the many dynamic similarities between swing phases and rapid eye movements, we further suggest that the swing phases may be generated by neural mechanisms similar to those that produce saccades and quick phases of nystagmus from a signal related to sensed or desired walking velocity. Grants: This work was supported by National Institute of Health Grants EY11812, EY04148, DC05204, and EY01867.     

计算机辅助步态分析系统在偏瘫患者行走功能康复中的作用

目的观察计算机辅助步态分析系统对偏瘫患者步行能力的影响。方法将i00例伴有行走障碍的脑卒中患者随机分为观察组和对照组各50例。两组康复治疗前后（3个月）均采用计算机辅助步态分析系统评价患者步态并进行常规药物治疗，观察组在计算机辅助步态分析系统的评价指导下进行步行能力训练，对照组则不依据步态分析检查结果进行训练。结果康复治疗3个月后，观察组异常步态具有明显改善，两组比较具有显著性差异（P〈0．05）。结论计算机步态分析系统指导步行训练可有效地矫正或改善偏瘫步态。     

Longitudinal Model of Periprosthetic Joint Infection in the Rat

The majority of periprosthetic joint infections occur shortly after primary joint replacement (<3 months) and require the removal of all implant components for the treatment period (~4 months). A clinically relevant animal model of periprosthetic infection should, therefore, establish an infection with implant components in place. Here, we describe a joint replacement model in the rat with ultrahigh molecular weight polyethylene (UHMWPE) and titanium components inoculated at the time of surgery by methicillin-sensitive Staphylococcus aureus (S. aureus), which is one of the main causative microorganisms of periprosthetic joint infections. We monitored the animals for 4 weeks by measuring gait, weight-bearing symmetry, von Frey testing, and micro-CT as our primary endpoint analyses. We also assessed the infection ex vivo using colony counts on the implant surfaces and histology of the surrounding tissues. The results confirmed the presence of a local infection for 4 weeks with osteolysis, loosening of the implants, and clinical infection indicators such as redness, swelling, and increased temperature. The utility of specific gait analysis parameters, especially temporal symmetry, hindlimb duty factor imbalance, and phase dispersion was identified in this model for assessing the longitudinal progression of the infection, and these metrics correlated with weight-bearing asymmetry. We propose to use this model to study the efficacy of using different local delivery regimens of antimicrobials on addressing periprosthetic joint infections. Statement of clinical significance: We have established a preclinical joint surgery model, in which postoperative recovery can be monitored over a multi-week course by assessing gait, weight-bearing, and allodynia. This model can be used to study the efficacy of different combinations of implant materials and medication regimens. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1101-1112, 2020     

Influence of Hamstrings on Knee Moments During Loading Response of Gait in Individuals Following ACL Reconstruction

Biomechanical studies consistently report smaller knee extensor moments in the surgical limb during loading response (LR) of gait following ACL reconstruction (ACLr). However, this reduction in knee loading is quantified by net joint moments (NJM). As a result, in the presence of greater hamstring activity, the true contribution from the knee extensors may not be reduced. The purpose of this study is to compare hamstring activity and strength and knee joint moments between individuals post-ACLr and controls. Eighteen individuals 3 months post-ACLr and matched controls walked and net knee extensor moment peak and impulse and hamstring activity were identified during LR, as well as maximal hamstring strength. A hybrid musculoskeletal model estimated knee flexor moments from joint kinematics and hamstring electromyography. Flexor moments (SIMM) were scaled based on strength. Knee extensor moments were estimated from the sum of the net knee moment and estimated knee flexor moment; estimated extensor moment peaks and impulse were calculated during LR. Repeated measures analysis of variance compared groups and limbs. Smaller net knee extensor moment and greater hamstring activity, as well as deficits in maximal hamstring strength, were observed in the surgical limb (all p < 0.05). When accounting for the torque-producing capabilities of the knee flexors, estimated knee extensor moment peak and impulse were smaller in the surgical limb. These findings suggest that net knee moments accurately reflect smaller knee extensor loading post-ACLr. Statement of Clinical Significance: Rehabilitation programs should target increasing knee extensor loading to restore gait mechanics during early rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:378-386, 2020     

Inter-segmental foot kinematics during gait in elderly females according to the severity of hallux valgus

The objective of this study was to find the effect of hallux valgus (HV) deformity on the inter-segmental motion of the foot using an MFM with a 15-marker set (DuPont Foot Model, DuFM) in comparison with age and sex controlled healthy adults. Fifty-eight female symptomatic HV patients and 50 female asymptomatic older female volunteers were included in this study. According to the radiographic hallux valgus angle (HVA), the study population was divided into severe HV (SHV, HVA ≥ 40°, n = 25), moderate HV (MHV, 20° ≤ HVA < 40°, n = 47), and control (CON, n = 36). MHV group was divided into symptomatic MHV group (S-MHV, n = 33) and asymptomatic MHV group (A-MHV, n = 14) according to the symptoms associated with HV. For temporal parameters, gait speed and stride length were diminished according to the severity of HV deformity. Sagittal range of motion of hallux and hindfoot decreased significantly in SHV group. Loss of push-off during the preswing phase was observed and forefoot adduction motion during terminal stance was decreased in SHV group. In a subgroup analysis of MHV, asymptomatic HV minimally affects gait and inter-segmental motion during gait. HV deformity affects gait parameters and inter-segmental motion of the foot during gait in proportion to the severity of the deformity. However, the effect of MHV itself on foot kinematics might be limited while pain or arthritic change of the joint might cause changes in gait in patients with symptomatic HV.     

Decreased posterior cruciate and altered collateral ligament loading following ACL transection: A longitudinal study in the ovine model

Although ACL deficiency is shown to lead to joint degeneration, few quantitative data are reported on its effect on soft tissue structures surrounding the knee joint, specifically, the posterior cruciate and collateral ligaments. The kinematics of the stifle joint of sheep (N = 5) were measured during “normal” gait, as well as 4 and 20 weeks after ACL transection. These motions were reproduced using a unique robotic manipulator and the loads borne by PCL, MCL, and LCL during gait were determined. Our results demonstrated a significant decrease in mean PCL loads 20 weeks post‐ACL injury, at hoof‐strike (0% of gait, p = 0.034), hoof‐off (66% of gait, p = 0.006), peak‐swing (85% of gait, p = 0.026), and extension‐before‐hoof‐strike (95% of gait, p = 0.028). Mean MCL loads did not significantly increase following ACL transection, maybe due to large between‐animal variation. Finally, mean LCL loads indicated a significant decrease (p < 0.047) at 20 weeks across the entire gait cycle. From a clinical perspective, the load redistributions observed in cruciate and collateral ligaments following ACL injury indicate that these tissues can carry/adapt to the altered mechanical environment of the joint. The considerable variability in the magnitudes of change following ACL injury among animals also simulates clinical variability in humans after trauma. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:431–438, 2014.