A Population of Patient-Specific Adult Acquired Flatfoot Deformity Models Before and After Surgery

Following IRB approval, a cohort of 3-D rigid-body computational models was created from submillimeter MRIs of clinically diagnosed Adult Acquired Flatfoot Deformity patients and employed to investigate postoperative foot/ankle function and surgical effect during single-leg stance. Models were constrained through physiologic joint contact, passive soft-tissue tension, active muscle force, full body weight, and without idealized joints. Models were validated against patient-matched controls using clinically utilized radiographic angle and distance measures and plantar force distributions in the medial forefoot, lateral forefoot, and hindfoot. Each model further predicted changes in strain for the spring ligament, deltoid ligament, and plantar fascia, as well as joint contact loads for three midfoot joints, the talonavicular, navicular-1st cuneiform, and calcaneocuboid. Radiographic agreement ranged across measures, with average absolute deviations of <5° and <4 mm indicating generally good agreement. Postoperative plantar force loading in patients and models was reduced for the medial forefoot and hindfoot concomitant with increases in the lateral forefoot. Model predicted reductions in medial soft-tissue strain and increases in lateral joint contact load were consistent with in vitro observations and elucidate the biomechanical mechanisms of repair. Thus, validated rigid-body models offer promise for the investigation of foot/ankle kinematics and biomechanical behaviors that are difficult to measure in vivo.     

内侧柱稳定手术治疗Ⅱ期成人胫后肌腱功能不全性平足的三维有限元生物力学分析

文题释义：平足内侧柱稳定手术：是指通过实施融合固定手术即融合舟楔关节或者跖楔关节,或者两者均融合来稳定足的第一跖列,恢复内侧纵弓的高度,纠正前足的旋前。 背景：平足症是足踝外科的常见病,其中Ⅱ期成人获得性平足在临床上最多见,此期的治疗最为关键。然而Ⅱ期平足内侧柱存在着不稳定,这也是造成足弓塌陷的重要原因。内侧柱稳定手术可以相当程度地纠正畸形,但是目前尚缺乏详细的生物力学实验来全面判断内侧柱稳定后对于全足带来的影响。 目的：探讨单纯内侧柱稳定手术对Ⅱ期成人获得性平足足部生物力学的影响。 方法：首先建立Ⅱa期及Ⅱb期成人获得性平足三维有限元模型,通过Geomagic软件、Solidwork软件及Abaqus软件模拟内侧柱稳定手术(舟楔关节融合､跖楔关节融合､两者均融合),将术前和术后模型模拟单倍体质量负重,比较其足底、内外侧柱骨块、内侧韧带的最大应力值,并通过测量相关参数来进行综合对比。 结果与结论：①单纯内侧柱稳定术后模拟负重时足底应力最大值均出现在第一跖骨头下方,其中Ⅱa期模型行内侧柱稳定后足底应力最大值明显增加,Ⅱb期模型内侧柱稳定后足底应力变化不明显;②内侧柱融合后相应关节的应力有所减轻,但对于第一跖列的其他关节应力反而增加了;③内侧柱融合后对于内侧韧带及足底筋膜的应力均没有减轻作用;④结果表明,单纯内侧柱稳定手术并不能降低Ⅱ期成人获得性平足内侧柱的压力,它仅可以作为联合使用的手术来稳定过度活动的关节以及纠正前足旋后畸形。 ORCID: 0000-0002-8230-1151(刘付胜华) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

Patello-femoral contact area and compressive force after anteromedial displacement of tibial tuberosity in amputated knees

Contact force and contact area in the patello-femoral joint was biomechanically analyzed using seven amputated legs. The knees were fixed firmly to the experimental apparatus and 300 N of tension was applied to the quadriceps tendon. Total contact force was measured using pressure-sensitive film, and the ratio of the contact area to the patellar joint surface (%) was measured using hydrophilic vinyl polysiloxane impression material. At a Q-angle of 0° with no advancement, 10 mm and 20 mm advancement of the tibial tuberosity, the total contact force on the patello-femoral joint at a knee flexion of 45° was 266±55 N, 191±58 N and 146±58 N, respectively. The total contact force became smaller as the advancement of the tibial tuberosity changed to 5, 10, 15 and 20 mm. Especially, the total contact force with Q-angle of 0° and anterior advancement of 15 and 20 mm was significantly smaller than that with no advancement. With a Q-angle of 0°, the contact area of the patello-femoral joint at 10 mm advancement was the greatest, occupying 30.1±9.9% of the whole patellar joint surface. The mean contact pressure with Q-angle of 0° and anterior advancement of 10 mm was smaller than that with all other positions, but there was no significant difference. In this experiment, combined anterior and medial displacement of the tibial tuberosity reduced the contact force in the patello-femoral joint of the amputated legs, and an advancement of 10 mm achieved optimal reduction of force and the greatest contact area.     

成人获得性可复性平足的生物力学研究进展

成人获得性扁平足主要由胫后肌腱功能不全引起,是足踝外科的常见病,其中以可复性平足最为多见。如何解释其发病机制并选择恰当的手术方式治疗是目前研究的热点。随着平足体外建模技术的日臻完善,生物力学试验的准确性和可重复性逐渐得到认可,其研究成果也成为临床平足治疗的重要理论依据。本文回顾了胫后肌腱功能不全导致平足的生物力学机制,及以此为基础在尸体标本和有限元模型上建立平足模型的各种不同方法,并对平足矫形相关基础研究中不同重建方法的生物力学特性进行分析比较。作者认为,在牵拉外在肌腱模拟其动力性稳定结构的前提下,采取破坏韧带等静力性稳定装置的方式建立起的可复性平足体外模型更为可靠;针对平足模型采用的各种重建方式的生物力学特性不尽相同,软组织重建应与骨性手术联合使用,而骨性手术需根据畸形程度和特点进行个性化的选择。     

The influence of loading intensity on muscle–tendon unit behavior during maximal knee extensor stretch shortening cycle exercise

Tendon stiffness increases as the magnitude and rate of loading increases, according to its viscoelastic properties. Thus, under some loading conditions tendons should become exceptionally stiff and act almost as rigid force transducers. Nonetheless, observations of tendon behavior during multi-joint sprinting and jumping tasks have shown that tendon strain increases whilst muscle strain decreases as the loading intensity increases. The purpose of the current study was to examine the influence of external loading intensity on muscle–tendon unit (MTU) behavior during a high-speed single-joint, stretch-shortening cycle (SSC) knee extension task. Eighteen men (n = 9) and women (n = 9) performed single-leg, maximum intensity SSC knee extensions at loads of 20, 60 and 90?% of their one repetition maximum. Vastus lateralis fascicle length (L _f) and velocity (v _f) as well as MTU (L _MTU) and tendinous tissue (L _t) length were measured using high-speed ultrasonography (96 Hz). Patellar tendon force (F _t) and rate of force development (RFD_t) were estimated using inverse dynamics. Results showed that as loading intensity increased, concentric joint velocity and shortening v _f decreased whilst F _t and RFD_t increased, but no significant differences were observed in eccentric joint velocity or peak L _MTU or L _f. In addition, the tendon lengthened significantly less at the end of the eccentric phase at heavier loads. This is the first observation that tendon strain decreases significantly during a SSC movement as loading intensity increases in vivo, resulting in a shift in the tendon acting as a power amplifier at light loads to a more rigid force transducer at heavy loads.     

UKA 关节线安装误差对膝关节接触力学和运动学影响

目的 针对单髁膝关节置换(unicompartmental knee arthroplasty, UKA)内侧假体松动和外侧关节软骨退化问题,通过骨肌多体动力学方法研究不同生理活动中UKA关节线安装误差对膝关节接触力学和运动学的影响。方法 以内侧自然关节线为0 mm误差,分别考虑±2 mm、±4 mm、±6 mm共6种关节线安装误差情况,建立7个内侧UKA置换的骨肌多体动力学模型,对比研究步行和下蹲运动中膝关节接触力学和运动学的变化。结果 在步行步态周期70%时,相比于0 mm误差UKA假体关节线升高2 mm时内侧假体接触力增大127.3%,外侧软骨接触力减少12.0%;在UKA假体关节线降低4 mm时内侧假体接触力接近0 N,外侧软骨接触力增大10.1%;胫股关节总接触力在关节线升高和降低2 mm时分别增大19.7%和减小14.2%。在下蹲屈膝100°时,相比于0 mm误差膝关节内侧假体接触力和胫股骨关节总接触力在UKA假体关节线升高2 mm时分别增大31.6%和11.1%,在UKA假体关节线降低2 mm时分别减小24.5%和8.5%,而膝关节外侧软骨接触力变化不大。同时,在步行步态...     

Effects of measurement methods for tibial rotation axis on the morphometry in Korean populations by gender

Background

There have been arguments for methodology in tibial rotation axis measurement, which accordingly determines the morphometry of the proximal tibia in total knee arthroplasty. The morphometry of the proximal tibia for the Korean population is determined by gender, based on the anatomical tibial axis and reliable rotational orientation in knee replacements, to evaluate the size suitability of the currently available prostheses in Korea.

Navigation-based analysis of associations between intraoperative joint gap and mediolateral laxity in total knee arthroplasty

BackgroundNo data have demonstrated how joint gap measured under a distraction force is actually associated with mediolateral laxity evaluated under a varus–valgus force during total knee arthroplasty (TKA). This study aimed to investigate the correlations between them using a navigation system.MethodsA total of 113 primary navigated TKAs were included. After bone resection and soft-tissue balancing, the component gap was measured with a distraction force of 60 N and 80 N for both the medial and lateral compartment (i.e. a total of 120 N and 160 N) at 0°, 10°, 30°, 60°, 90°, and 120° knee flexion. After the final prosthetic implantation and capsule closure, mediolateral laxity under a maximum varus–valgus stress was recorded with image-free navigation at each knee flexion angle. The correlation between joint gap laxity (total differences between component gap and insert thickness in the medial and lateral compartment) and mediolateral laxity was analyzed using Spearman’s rank correlation coefficient.ResultsThe joint gap laxity under both distraction forces showed significant positive correlations with mediolateral laxity at 10°, 30°, 60°, and 90° flexion, whereas no correlation was observed at extension and 120° flexion. The correlations were stronger in gap measurement under 80 N than 60 N at all examined ranges. In patients with body mass indexes (BMIs) ≥ 30 kg/m², the correlation became non-significant.ConclusionIntraoperative joint gap laxity was associated with mediolateral laxity after TKA, especially at mid-flexion angles. The factors weakening the correlations were a lower applied distraction force for gap measurement and a larger BMI.     

The effects of massed versus distributed contractions on the variability of maximal isometric force

This study evaluated the effect of a massed versus distributed repetition schedule on the variability of force and surface electromyographic (sEMG) activity during maximal voluntary isometric elbow flexion contractions. The massed group (N = 13) performed 15 contractions on 1 day, while the distributed group (N = 13) performed 15 contractions across three consecutive days (five per day). Two retention tests (five contractions each) occurred 2 weeks and 3 months after the final trial of the initial test sessions. Force and sEMG of the biceps and triceps brachii muscles were recorded concurrently. Both groups had comparable increases in force and biceps brachii sEMG that continued over short- and longer-term retention tests (p < 0.05). Triceps brachii sEMG exhibited a more complicated pattern of successive decreases and increases (p < 0.05). The massed repetition schedule resulted in significantly (p < 0.05) less variability in maintaining a constant force [root mean square (RMS) error]. There was a significant decrease in the variability of the force–time and sEMG–time curves as assessed by the variance ratio (VR) (p < 0.05). Only biceps sEMG and VR correlated highly with force VR for the distributed group. Total (biceps + triceps) sEMG magnitude and variability correlated highly with both RMS error and force VR for the massed group. It was concluded that the massed contraction pattern allowed participants to learn how to regulate joint stiffness in addition to the variability of muscle activity. This allowed for greater decreases in RMS error than could be obtained by regulating the variability of muscle activity alone.     

Reductions in finger blood flow induced by 125-Hz vibration: effect of area of contact with vibration

To investigate whether the Pacinian channel is involved in vibration-induced reductions of finger blood flow (FBF), vibrotactile thresholds and vasoconstriction have been studied with 125-Hz vibration and two contact areas: 3- or 6-mm-diameter vibrating probes with 2-mm gaps to fixed surrounds. Fifteen subjects provided thresholds for perceiving vibration at the thenar eminence of the right hand with both contact areas. With both contact areas, FBF was then measured in the middle fingers of both hands during five successive 5-min periods: (i) no force and no vibration, (ii) force and no vibration, (iii) force with vibration 15 dB above threshold, (iv) force and no vibration, and (v) no force and no vibration. Thresholds were in the ranges of 0.16–0.66 ms^?2 r.m.s. (6-mm probe) and 0.32–1.62 ms^?2 r.m.s. (3-mm probe). With the magnitude of vibration 15 dB above each individual’s threshold with the 3-mm probe, the median reduction in FBF with the 6-mm probe (to 70 and 77 % of pre-exposure FBF on the exposed right hand and the unexposed left hand, respectively) was greater than with the 3-mm probe (79 and 85 %). There were similar reductions in FBF when vibration was presented by the two contactors at the same sensation level (i.e. 15 dB above threshold with each probe). The findings are consistent with reductions in FBF arising from excitation of the Pacinian channel: increasing the area excited by vibration increases Pacinian activation and provokes stronger perception of vibration and greater vasoconstriction.     

Differential strain patterns of the human gastrocnemius aponeurosis and free tendon,in vivo

Aim: The mechanical characteristics of the human free tendon and aponeurosis, in vivo, remains largely unknown. The present study evaluated the longitudinal displacement of the separate free Achilles tendon and distal (deep) aponeurosis of the medial gastrocnemius muscle during voluntary isometric contraction. Methods: Ultrasonography‐obtained displacement of the free tendon and tendon–aponeurosis complex, electromyography of the gastrocnemius, soleus, and dorsiflexor muscles, and joint angular rotation were recorded during isometric plantarflexion (n = 5). Tendon cross‐sectional area, moment arm and segment lengths (L_o) were measured using magnetic resonance imaging. Tendon force was calculated from joint moments and tendon moment arm, and stress was obtained by dividing force by cross‐sectional area. The difference between the free tendon and tendon–aponeurosis complex deformation yielded separate distal aponeurosis deformation. Longitudinal aponeurosis and tendon strain were obtained from the deformations normalized to segment lengths. Results: At a common tendon force of 2641 ± 306 N, the respective deformation and L_o were 5.85 ± 0.85 and 74 ± 0.8 mm for the free tendon and 2.12 ± 0.64 and 145 ± 1.3 mm for the distal aponeurosis, P < 0.05. Longitudinal strain was 8.0 ± 1.2% for the tendon and 1.4 ± 0.4% for the aponeurosis, P < 0.01. Stiffness and stored energy was 759 ± 132 N mm^?1 and 6.14 ± 1.89 J, respectively, for the free tendon. Cross‐sectional area of the Achilles tendon was 73 ± 4 mm², yielding a stress of 36.5 ± 4.6 MPa and Young's modulus of 788 ± 181 MPa. Conclusion: The free Achilles tendon demonstrates greater strain compared with that of the distal (deep) aponeurosis during voluntary isometric contraction, which suggests that separate functional roles may exist during in vivo force transmission.     

Mallet finger: a simulation and analysis of hyperflexion versus hyperextension injuries

The goal of this study was to simulate the mechanisms of hyperflexion and hyperextension injuries of the distal interphalangeal (DIP) joint of the hand and to analyze the resulting extensor tendon injury patterns. The hypotheses were raised that hyperflexion trauma leads to a plastic deformation of the extensor tendon aponeurosis, with or without a small bony avulsion fragment but without joint surface involvement, and that hyperextension injuries can create a shear fracture of the dorsal lip of the distal phalanx, without injury to the extensor tendon aponeurosis. Loading was applied with a swinging pendulum impacting the distal phalanx in 103 human specimens in either an extended or flexion position. After loading, injury patterns were analyzed radiologically and histologically. There was evidence that hyperflexion trauma leads to a plastic deformation or rupture of the extensor tendon. Bony tendon avulsion was evident in 12.2 % of cases. With hyperextension, the extensor tendon remained intact in all cases, but there were large fracture fragments involving the articular surface in 4.1 % of cases. The results of the study show that force on the flexed joint leads to overstretching of the extensor tendon, and to an associated dorsal bony avulsion with intact joint line. Force applied to the joint in extension can lead to a bony dorsal edge fracture with articular involvement and with it, a palmar DIP joint capsule rupture. The results illuminate a direct correlation between the mechanism of injury and the pattern of injury in the clinical picture of mallet finger.     

Evans手术对跟骰关节压力影响的生物力学研究

目的　研究Evans手术矫正平足畸形对跟骰关节压力的影响以及该术式的足外侧柱最佳撑开宽度,为临床提供借鉴与参考。 方法　6例正常成人新鲜足标本,根据不同工况分为正常对照组、平足模型组、Evans手术外侧柱延长的LCL*4 mm、LCL*6 mm、LCL*8 mm、LCL*10 mm及LCL*12 mm组。实验标本逐级加载至350 N,利用K-ScanTM骨关节接触面测量系统的K-Scan6900#压敏片分别测量7组跟骰关节压力变化。 结果　在350 N垂直载荷下跟骰关节的峰值压强分别为（kg/cm2）：对照组(9.21±　1.60)、平足组(24.90±2.45)、LCL*4 mm组(21.68±2.21)、LCL*6 mm组(15.95±2.59)、LCL*8 mm组(11.04±　1.15)、LCL*10 mm组(15.20±2.35)、LCL*12 mm组(21.55±2.03)。平足组跟骰关节峰值压强较对照组显著增高（P＜0.05）;Evans术后的所有组跟骰关节峰值压强较平足组有明显降低（P＜0.05）;LCL*8 mm组与正常对照组跟骰关节峰值压强接近（P=0.143）;LCL*8mm组跟骰关节峰值压强较其他外侧柱延长组小（P＜0.05）。 结论　 Evans手术治疗获得性平足,其术后对跟骰关节压力在一定范围内较平足术前有所减小,呈先减小后增大的趋势;而撑开长度在8 mm时跟骰关节压力最小,且最接近正常状态。     

Accelerometry Reveals Differences in Gait Variability Between Patients with Multiple Sclerosis and Healthy Controls

Variability of movement reflects important information for the maintenance of the health of the system. For pathological populations, changes in variability during gait signal the presence of abnormal motor control strategies. For persons with multiple sclerosis (PwMS), extensive gait problems have been reported including changes in gait variability. While previous studies have focused on footfall variability, the present study used accelerometers on the trunk to measure variability during walking. Thus, the purpose of this study was to examine the variability of the acceleration pattern of the upper and lower trunk in PwMS compared to healthy controls. We extracted linear and nonlinear measures of gait variability from 30 s of steady state walking for 15 PwMS and 15 age-matched healthy controls. PwMS had altered variability compared to controls with greater Lyapunov exponent in the ML (p < 0.001) and AP (p < 0.001) directions, and greater frequency dispersion in the ML direction (p = 0.034). PwMS also demonstrated greater mean velocity in the ML direction (p = 0.045) and lower root mean square of acceleration in the AP direction (p = 0.040). These findings indicate that PwMS have altered structure of variability of the trunk during gait compared to healthy controls and agree with previous findings related to changes in gait variability in PwMS.     

Muscle–tendon interaction and EMG profiles of world class endurance runners during hopping

The present study examined the muscle–tendon interaction of ten international level Kenyan runners. Ultrasonography and kinematics were applied together with EMG recordings of lower limb muscles during repetitive hopping performed at maximal level. The ten Kenyans had longer gastro Achilles tendon at rest (p < 0.01) as compared with ten control subjects matched in height. Conversely, the stretching and shortening amplitudes of the tendinous tissues of the medial gastrocnemius (MG) muscle were significantly smaller in the Kenyans than in controls during the contact phase of hopping. This applied also to the fascicle length changes, which were smaller and more homogeneous among Kenyans. These limited musculo-tendinous changes resulted in higher maximal hopping height and in larger power despite their reduced body weight. The associated finding of a greater shortening to stretching ratio of the MG tendinous tissues during contact could imply that the Kenyan MG muscle–tendon unit is optimized to favor efficient storage and recoil of elastic energy, while operating at optimal muscle fascicle working range (plateau region).     

成人获得性平足症的相关研究及进展

目的 总结成人获得性平足症的研究进展,为临床成人获得性平足症的诊断、治疗、预防提供理论依据。方法 分别以“成人获得性平足症”为关键词在万方数据库和以“acquired adult flatfoot”为关键词在PubMed数据库检索1985年1月—2017年1月与成人获得性平足症的解剖因素、发病原因及手术治疗相关文献并对其分析总结。结果 成人获得性平足症主要表现为足部骨性结构和软组织因素共同导致的足纵弓的塌陷或消失,胫后肌腱功能不全为其最常见的发病原因。若经保守治疗病情未缓解,需外科手术阻止病情进一步发展。结论 成人获得性平足症的诊治需结合发病原因、疾病分期等相关因素,对不同的患者制定个体化治疗方案。     

膝关节矢状面机构模型

建立矢状面上膝关节二维机构模型，求解矢状面髌股关节求解屈膝过程中髌骨与股骨的接触点移动，髌骨倾角、髌韧带倾角变化，髌股关节功能角变化以及髌股接触力和髌韧带作用力的变化等髌股关节运动及动力学参数．依据膝关节主要组成部分的功能及相互间连接关系，以股胫关节交叉四连杆模型为基础，通过对髌股关节的几何描述及力平衡限定，并运用ADAMS软件进行分析计算，计算结果与文献实验结果吻合良好。     

Absence of the flexor digitorum longus tendon: An MRI study

Flexor digitorum longus (FDL) is the primary flexor of the lateral four toes. It is a reliable source of tendon for transfer surgery. We present a case whereby a patient who required a reconstruction for adult acquired flatfoot deformity using FDL as a dynamic structure for transfer was found to have an absent FDL tendon at the time of operation, necessitating the use of flexor hallucis longus (FHL) instead. This unusual finding prompted us to investigate the frequency of absence of the FDL tendon. We reviewed our hospital MRI database of foot and ankle images specifically looking for patients with absence of this tendon. After randomization, 756 images were reviewed independently by two surgeons and a consultant musculoskeletal radiologist. No instances of an absent FDL tendon were identified. In conclusion, the frequency of absence of the FDL tendon is less than 1 in 750. Surgeons who require FDL for tendon transfer surgery need not image the foot preoperatively to anticipate the need for the use of FHL as an alternative. Clin. Anat. 25:1062–1065, 2012. © 2012 Wiley Periodicals, Inc.     

Effect of centrifuging shell vials at 3,500 x g on detection of viruses in clinical specimens.

An increase in shell vial centrifugation force to 3,500 x g and a concomitant reduction in spin time to 15 min did not decrease the sensitivity of detecting viruses in clinical specimens compared with the accepted practice of using 700 x g for 40 min. No damage to the cell monolayer (ML) at the higher g force was observed. Toxicity to the ML is decreased with the shorter spin, probably because of reduced time of contact between the specimen and the ML.     

The relationship between anteroposterior stability and medial–lateral stability of the bi-cruciate stabilized total knee arthroplasty

Background

Acquisition of appropriate anteroposterior (AP) stability depends on the prosthetic design and intraoperative soft tissue handling. A bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) has a two cam-post mechanism, which substitutes for the anterior cruciate ligament and posterior cruciate ligament (PCL). Therefore, appropriate AP stability is expected. Because the PCL is sacrificed during BCS TKA, medial stability and lateral stability are thought to be important factors to determine AP stability. However, no previous study has reported AP stability after BCS TKA and the relationship between AP and medial–lateral stability.