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.     

生物谐振规律对步行效率影响的前驱研究

目的:通过下肢软瘫模型研究生物谐振对步行效率的影响。方法:下肢软瘫并导致步行障碍的男性小儿麻痹后遗症患者12名(17±1岁,身高1.68±4.6m,体重52.5±5.4kg)与同龄健康青年12名匹配对照。采用三维步态分析系统获取步态参数,采用便携式气体分析系统测定氧价,作为能量效率的指标。评测状态为自然步行、80%自然步频以及120%自然步频,即100%、80%、120%自然步频。结果:儿麻患者在100%、80%、120%自然步频的条件下步速分别为(65.45±8.71、53.04±5.92、74.47±9.49)m/s,步速和步频密切相关(r=0.96,P<0.01);耗氧量分别为(15.17±3.56、20.76±4.31、21.48±6.16)ml/min/kg,慢速与快速步频的耗氧量均显著高于自然步频(P<0.01);氧价分别为(0.231±0.043、0.294±0.061、0.288±0.072)ml/m/kg,和同龄正常人比较自然、慢速与快速步频下的氧价均明显增加(P<0.01)。慢速与快速步频的氧价亦显著高于自然步频(P<0.05)。结论:儿麻患者自然步频的能量效率最高,步频加速或者减慢均降低此效率,提示肌肉固有谐振规律的作用。     

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.     

Evaluation of knee joint muscle forces and tissue stresses‐strains during gait in severe OA versus normal subjects

Osteoarthritis (OA) is the leading cause of pain and disability in the elderly with the knee being the most affected weight bearing joint. We used a musculoskeletal biomechanical model of the lower extremity including a detailed validated knee joint finite element model to compute lower extremity muscle forces and knee joint stresses‐strains during the stance phase of gait. The model was driven by gait data on OA patients, and results were compared with those of the same model driven by data on normal controls. Additional analyses were performed with altered cartilage‐menisci properties to evaluate the effects of deterioration during OA. In OA patients compared to normal subjects, muscle forces dropped at nearly all stance periods except mid‐stance. Force in the anterior cruciate ligament remained overall the same. Total contact forces‐stresses deceased by about 25%. Alterations in properties due to OA had negligible effects on muscle forces, but increased contact areas and cartilage strains and reduced contact pressures. Reductions in contact stresses and increases in tissue strains and transfer of load via menisci are partly due to the altered kinetics‐kinematics of gait and partly due to deterioration in cartilage‐menisci properties in OA patients. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:69–78, 2014.     

Total ankle replacement in patients with end-stage ankle osteoarthritis: Clinical results and kinetic gait analysis

BackgroundTotal ankle arthroplasty is being used more frequently as an alternative for arthrodesis in final stages of ankle osteoarthritis. However, there are few studies which describe the biomechanics of gait of these patients.MethodsBetween March 2006 and May 2011, 17 patients (n = 18 ankles) suffering end-stage osteoarthritis of the ankle who underwent an ankle replacement (HINTEGRA) were evaluated retrospectively. We evaluated clinical, radiological and biomechanical gait parameters using the NedAMH/IBV dynamometric platform.ResultsAt last follow-up (average: 37 months), the AOFAS score improved from 31 to 83 with a high rate of satisfaction (83.3%). Kinetic gait parameters were more similar to a healthy ankle. We detected a radiolucent line in 8 patients (44%) without any subsidence case.ConclusionsOur study showed a high rate of satisfaction and biomechanics of the gait similar to a healthy ankle. The complication rate was analogous to those previously published in the literature.     

The importance of submalleolar deformity in determining leg length discrepancy

Background and purposeThe association of leg length discrepancy (LLD) with a number of clinical disorders has made its determination a significant part of the physical examination. We believe that submalleolar causes of LLD may be under-acknowledged. The most common clinical method used to measure LLD is by tape from the anterior superior iliac spine (ASIS) to medial malleolus which disregards the potential for LLD arising from asymmetry in the foot distal to the tibiotalar joint.MethodsThe present pilot study involves a group of 5 volunteers (experimental group) and a group of 3 patients with flexible flat feet (clinical study). The differences in tibial tubercle height from the ground between full pronation and full supination were measured using the CODA MPX 30^® system (Charnwood Dynamics Limited, Leicestershire, England). Correlations of the patterns within each group were produced.ResultsA significant relationship with leg lengths was found in the experimental group when they induced maximum pronation (R-squared = 0.62, p = 0.007) while an inverse relationship occurred with supination, although marginally significant (R-squared = 0.37, p = 0.064).ConclusionsWe have demonstrated that significant leg length discrepancy can occur in patients who do not have obvious deformity when non weight bearing. We recommend using the blocks method routinely. Appropriately measuring LLD is of vital importance to properly diagnosing and treating patients with unequal leg lengths or related symptoms.