A system to measure the forces and moments at the knee and hip during level walking

The forces and moments in the sagittal plane at the knee and hip were calculated using gait data collected during level walking. Accelerations were measured by accelerometers attached to the legs, and the force reactions at the foot were measured by a force plate. The recorded accelerations and the foot forces were used to determine the joint reactions through a Newtonian formulation modeling the leg as articulated, rigid links. Twelve normal subjects were included in this study along with nine lower limb amputees. Obvious differences were observed when comparing amputee data to normal data both at the knee and hip. Gait data obtained by this system can be readily used to form criteria for objective gait analysis and improved prosthesis design.     

Tibio-femoral loading during human gait and stair climbing.

Surgical intervention of the knee joint routinely endeavors to recreate a physiologically normal joint loading environment. The loading conditions resulting from osteotomies, fracture treatment, ligament replacements, and arthroplasties of the knee are considered to have an impact on the long term clinical outcome; however, knowledge regarding in vivo loading conditions is limited. Using a previously validated musculoskeletal lower limb model, we predicted the tibio-femoral joint contact forces that occur in the human knee during the common daily activities of walking and stair climbing. The average resultant peak force during walking was 3.1 times body weight (BW) across four total hip arthroplasty patients. Inter-individual variations proved larger than the variation of forces for each patient repeating the same task. Forces through the knee were considerably larger during stair climbing than during walking: the average resultant peak force during stair climbing was 5.4 BW although peaks of up to 6.2 BW were calculated for one particular patient. Average anteroposterior peak shear components of 0.6 BW were determined during walking and 1.3 BW during stair climbing. These results confirm both the joint contact forces reported in the literature and the importance of muscular activity in creating high forces across the joint. The magnitudes of these forces, specifically in shear, have implications for all forms of surgical intervention in the knee. The data demonstrate that high contact and shear forces are generated during weight bearing combined with knee flexion angles greater than approximately 15 degrees. Clinically, the conditions that produce these larger contact forces should be avoided during post-operative rehabilitation.     

Effect of frontal plane tibiofemoral angle on the stress and strain at the knee cartilage during the stance phase of gait

Subject‐specific three‐dimensional finite element models of the knee joint were created and used to study the effect of the frontal plane tibiofemoral angle on the stress and strain distribution in the knee cartilage during the stance phase of the gait cycle. Knee models of three subjects with different tibiofemoral angle and body weight were created based on magnetic resonance imaging of the knee. Loading and boundary conditions were determined from motion analysis and force platform data, in conjunction with the muscle‐force reduction method. During the stance phase of walking, all subjects exhibited a valgus–varus–valgus knee moment pattern with the maximum compressive load and varus knee moment occurring at approximately 25% of the stance phase of the gait cycle. Our results demonstrated that the subject with varus alignment had the largest stresses at the medial compartment of the knee compared to the subjects with normal alignment and valgus alignment, suggesting that this subject might be most susceptible to developing medial compartment osteoarthritis (OA). In addition, the magnitude of stress and strain on the lateral cartilage of the subject with valgus alignment were found to be larger compared to subjects with normal alignment and varus alignment, suggesting that this subject might be most susceptible to developing lateral compartment knee OA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1539–1547, 2010     

Mathematical estimation of stress distribution in normal and dysplastic human hips.

By using a mathematical model of the adult human hip in the static one-legged stance position of the body, the forces acting on the hip, peak stress in the hip joint and other relevant radiographic and biomechanical parameters were assessed. The aims were to examine if the peak stress in dysplastic hips is higher than in normal hips and to find out which biomechanical parameters contribute significantly to higher peak stress. The average normalized peak stress in dysplastic hips (7.1 kPa/N) was markedly higher (to approximately 100%) than the average normalized peak stress in normal hips (3.5 kPa/N). The characteristic parameters that contributed to higher peak stress in dysplastic hips included the smaller lateral coverage of the femoral head, the larger interhip distance, the wider pelvis, and the medial position of the greater trochanter. These results are consistent with the hypothesis that stress distribution over weight-bearing surface of the hip joint is the relevant parameter for assessment of the risk for developing coxarthrosis.     

Idiopathic scoliosis and balance organisation in seated position on a seesaw

The aim was to determine the biomechanical processes involved in postural regulation when self-imposed disturbances occur in the seated position in the antero-posterior direction. Twelve female adolescents with right thoracic scoliosis (SG) (Cobb = 30.4° ± 9.7) and 15 control adolescents (CG) were included in this study. The ground reaction forces (GRF) were studied whilst the subjects maintained their balance in the sitting position on a seesaw. Six conditions were tested: eyes open and closed; with an additional load placed on the subject’s right or left shoulder; and with an additional load on the subject’s right or left pelvis. The SG showed significantly higher force amplitudes and variability and fewer oscillations than the CG in all the conditions. In the SG, the time analysis showed that the duration of the GRF was significantly higher in forward and left directions. Whatever the condition tested, the intra-group differences were not significant. The scoliotic patients in seated position were characterised by larger changes of the GRF, especially with a postural control in the forward and left directions, corresponding to that on the concave side of their spinal curvature. No significant differences were found to exist between the various conditions (load and unload, eyes open and eyes closed). Clinical tests and rehabilitation methods should include assessments of seated patients’ spatio-temporal adaptation to GRF.     

Dynamic in vivo kinematics of the intact ovine stifle joint.

The ovine stifle joint is a promising model for the investigation of joint mechanobiology in both normal and pathological states. The objectives of this study were to characterize three-dimensional (3D) joint motion in the intact ovine stifle joint during walking, incline walking, and trotting; to determine the range of variability in normal joint motion (intrasubject and intersubject); and to characterize the 3D ground reaction forces in the ovine hind limb during walking. 3D in vivo kinematics were measured in the right hind limb of eight sheep during walking, incline walking, and trotting on a treadmill (accuracy: 0.4 +/- 0.4 mm, 0.4 +/- 0.4 degrees). 3D ground reaction forces were measured in the hind limbs of the same subjects during walking. Joint flexion ranged from 43.1 to 77.0 degrees, and was coupled with abduction (0.0-4.1 degrees ), internal rotation (5.9-17.6 degrees), and translations in the medial (5.1-7.3 mm), anterior (21.9-23.8 mm), and superior (6.0-11.4 mm) directions. Kinematics were similar during walking, incline walking, and trotting. Intrasubject variability was small, ranging from 0.4-2.0 degrees for rotations, and 0.4-0.5 mm for translations. The active range of joint motion was offset between subjects leading to intersubject variability of 4.1-7.4 degrees for rotations and 2.5-4.2 mm for translations. Peak vertical ground reaction forces in the hind limbs ranged from 34.5(+/-1.6) to 50.0(+/-5.6)% body weight. This study establishes the bounds of normal motion in the intact ovine stifle joint and provides baseline data for further studies of joint mechanobiology in this model.     

Expression of the CD44 variant isoform 5 in the human osteoarthritic knee joint: correlation with radiological, histomorphological, and biochemical parameters.

PURPOSE: The purpose of this study was to correlate expression of CD44v5 in osteoarthritic synovium, cartilage, and synovial fluid with radiographical, histomorphological, and biochemical data. METHODS: Cartilage and synovia specimens of 27 patients with osteoarthritis were histomorphologically assessed according to Mankin and Pelletier, respectively. Extended weight-bearing antero-posterior radiographs were evaluated according to Kellgren and Ahlback. Expression of membrane-bound CD44v5 was analyzed by immunohistochemistry and levels of soluble CD44v5 were determined by ELISA. RESULTS: Expression of CD44v5 in cartilage and synovia was detected in 67% and 59% of the patients, respectively. Immunohistochemical findings in cartilage correlated significantly with structural cartilage changes (p < 0.001), whereas no correlation was found between expression in synovia and inflammatory synovial changes. Additionally, no relationship was evident between CD44v5 expression and radiographical data, but expression in cartilage and synovium was significantly correlated with each other (p < 0.04). Surprisingly, expression of CD44v5 in both cartilage and synovia was negatively correlated with synovial fluid levels of TNFalpha (p < 0.03 and p < 0.02, respectively), and no association was evident with levels of IL-1beta. CONCLUSIONS: The data demonstrate expression of CD44v5 in osteoarthritic cartilage and synovia, probably independent of joint inflammation. But more importantly, expression of this receptor variant in cartilage seems to be strongly related to the degree of cartilage destruction.     

Influence of Drop-Landing Exercises on Bone Geometry and Biomechanical Properties in Prepubertal Girls: A Randomized Controlled Study

We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 girls (Tanner stage 1, 6–10 years old) randomly assigned to control (C), low-drop (LD), or high-drop (HD) exercise groups. The LD and HD groups performed single-leg drop-landings (three sessions/week and 50 landings/session) from 14 and 28 cm, respectively, using the nondominant leg. Single-leg peak ground-reaction impact forces in a subsample ranged between 2.5 and 4.4 times body weight. Dependent variables were bone geometry and biomechanical properties using magnetic resonance imaging. No differences (P > 0.05) were found among groups at baseline for age, stature, lean tissue mass (DXA - Lunar 3.6-DPX), leisure-time physical activity, average daily calcium intake, or measures of knee extensor or flexor torque. A series of ANOVA and ANCOVA tests showed no within- or between-group differences from baseline to posttraining. Group comparisons assessing magnitude of change in side-to-side differences in geometry (area cm²) and cross-sectional moment of inertia (cm⁴) at proximal, mid, and distal sites revealed negligible effect sizes. Our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low to moderate peak ground-reaction impact forces do not influence geometrical or biomechanical measures in the developing prepubertal female skeleton.     

Contact pressures in the patellofemoral joint during impact loading on the human flexed knee

Currently, a bone fracture criterion is used by the automotive industry to assess the potential for a lower extremity injury from impact directed on the flexed knee. However, recent studies with animal models indicate irreversible damage to articular cartilage due to overpressures generated within the patellofemoral (P-F) joint without bone fracture, and suggest this injury may lead to a progressive, degenerative disease of the joint. The purpose of this investigation was to measure contact pressure in the human P-F joint during impact loading on the isolated, flexed knee. Loads were delivered on the patella with a free-flight inertial mass that had a rigid or foam padded interface. The experiments were conducted by serially increasing the impactor velocity in repeated tests until bone fracture was observed. The distribution of maximum pressures generated within the joint was recorded with a pressure-sensitive film. Fracture of the patella or the femur occurred at impact loads of approximately 8.5 kN. The average P-F pressure was approximately 25 MPa for 8 kN of impact load on the 90 degrees flexed joint. The P-F contact area varied with the level of contact load and degree of joint flexion. The distribution of P-F pressures was nonuniform. At approximately 70% of the fracture load for the 90 degrees flexed knee, nearly 35% of the contact area was exposed to pressures greater than 25 MPa. In an earlier study by others using subchondral bone-cartilage preparations, this level of pressure resulted in fissures and lacerations of the cartilage.     

Ligament tension pattern in the flexed knee in combined passive anterior translation and axial rotation.

Twenty-two fresh-frozen specimens were used to measure tensions generated in selected bands of the major ligaments of the flexed knee (40-90 degrees) when an axially prerotated tibia is subjected to passive anterior shear and when an anteriorly pretranslated tibia is subjected to passive axial torque. The tensions were measured using the buckle transducer attached to the anteromedial band of the anterior cruciate ligament [ACL (am)], the posterior fibers of the posterior cruciate ligament [PCL (pf)], the long fibers of the medial collateral ligament [MCL (lf)], and in the total lateral collateral ligament [LCL]. The knee specimens were subjected to the combined motions in a 6-df passive loading apparatus. The results indicated that the joint resistance to anterior translation increased markedly with internal prerotation and only marginally with external prerotation. This increase in joint resistance, however, was associated with a decrease in ACL function. It has been inferred that the posterior structures, capsular and meniscal, contribute significantly to joint resistance when the tibia is prerotated in either sense. For internal prerotation, the interference between the medial femoral condyle and the central tibial eminence was found to be an additional mechanism of resistance to anterior translation. Also, it has been found that although the ACL (am) tension increased with internal rotation in the normal case, it decreased with internal rotation in the presence of an anterior pretranslation. It is concluded that ACL response to combined joint motion cannot be ascertained by a simple summation of its responses to individual motions.     

后交叉韧带断裂和重建对兔膝关节软骨退变的影响

目的 探讨后交叉韧带（PCL）断裂和重建对膝关节软骨退变的影响。方法将33只新西兰大白兔共分3组,实验Ⅰ组：21只兔右膝关节PCL切断,左膝行单纯关节切开术作为对照组;实验Ⅱ组：12只兔右膝关节PCL切断后即刻重建。对照组、实验Ⅰ组术后6、12、26周处死动物,实验组Ⅱ术后12、26周处死动物。通过墨汁染色、HE染色、甲苯胺蓝染色、免疫组化染色（Ⅰ型胶原,Ⅱ型胶原和Ⅲ型胶原单克隆抗体）及扫描电镜方法对各组膝关节软骨退变的情况进行观察分析。结果实验Ⅰ组：PCL切断后26周标本有明显膝关节退行性改变;PCL切断后26周标本关节软骨继发损伤明显重于对照组术后同期标本;内髁软骨可见范围较大的软骨纤维化现象,达深层,细胞数量减少,Mankin评分平均7．7;纤维化的软骨层Ⅰ、Ⅲ型胶原染色阳性,Ⅱ型胶原染色较浅。扫描电镜上股骨内髁各时间段内都可见软骨损伤,而对照组只表现有垄沟样结构的紊乱。实验Ⅱ组：仅部分标本有轻度软骨损伤,术后26周时滑车及内髁处软骨继发损伤较实验Ⅰ组明显减轻。结论PCL断裂可以继发关节软骨的退行性改变,且以内侧间室和髌股关节为主,并随时间的延长逐渐加重。PCL断裂后即刻重建可以有效阻止关节软骨继发损伤的发生。     

膝骨性关节炎的中医辨证分型与膝关节镜下病理改变对比性研究

目的对比性地研究膝骨性关节炎中西医诊断相关性.方法对60例膝骨性关节炎患者进行中医辨证,分三型:Ⅰ型,肝肾不足,筋脉瘀滞型(21例);Ⅱ型,脾肾两虚,湿注骨节型(18例);Ⅲ型,肝肾亏虚,痰瘀交阻型(21例).然后进行关节镜下病理改变观察,同时进行组织学病理改变观察.结果 60例病人均有不同程度的关节软骨面退行磨损或剥脱.18例Ⅱ型的滑膜增生或炎性变与Ⅰ、Ⅲ型比较差异有显著性意义,P＜0.01.21例Ⅲ型的骨赘增生与Ⅰ、Ⅱ型比较差异有显著性意义,P＜0.01.结论脾肾两虚、湿注骨节型与镜下滑膜增生及炎性变有较密切临床诊断意义;肝肾亏虚、痰瘀交阻型与镜下骨赘增生有较密切临床诊断价值.     

前交叉韧带断裂和重建对膝关节软骨退变影响的实验研究

目的：研究前交叉韧带（ACL）断裂和不同时期重建对膝关节软骨继发损伤的影响。方法：以新西兰大白兔为实验对象,共14只。共分4组,每组7个膝关节,实验组Ⅰ：右膝前交叉韧带切断后随即重建,左膝的前交叉韧带切断后不予重建作为对照组Ⅰ;组Ⅱ：右膝前交叉韧带切断后3周重建,左膝行单纯关节切开术作为对照组Ⅱ。术后8周通过墨汁染色,常规组织学及扫描电镜方法观察各组膝关节软骨退变的情况。结果：（1）实验组Ⅰ关节软骨退变程度明显轻于对照组Ⅰ（Hc=5.9889,P=0.0144);(2)实验组Ⅱ关节软骨退变程度和对照组Ⅰ相比差异无显著性意义（Hc=0.7143,P=0.785)。结论：（1）ACL断裂后即刻重建可以有效阻止关节软骨继发损伤的发生;（2）ACL断裂后已继发关节软骨退变时再行重建,其对关节软骨退行性变的缓解作用不明显。ACL 裂后应进行早期重建,恢复膝关节稳定性,减少或延缓远期骨性关节炎的发性。     

Forces and torques during fracture reduction: Intraoperative measurements in the femur.

Reduction is a crucial step in fracture treatment. We determined intraoperative peak forces and torques during fracture reduction in seven patients with eight fractures of the femoral shaft. All fractures were temporarily stabilized by external fixation. Force and torque measurements were performed during the subsequent intramedullary nailing procedure. A three-dimensional load cell was attached to the distal femur fragment using two Schanz screws. All forces and torques were registered on-line during the reduction process. The maximum resulting force was 411 N, the maximum resulting torque 74 N x m. The highest force was observed along the shaft axis with 396 N for distraction. The maximum torque value was measured around the frontal axis, being 74 N x m for antecurvature. These results may assist the development of new reduction techniques and devices.