Thomas R. Jenkyn

Lateral trunk lean explains variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis

OBJECTIVE To test the hypothesis that selected gait kinematics, particularly lateral trunk lean, observed in patients with medial compartment knee osteoarthritis explain variation in dynamic knee joint load. METHOD In this cross-sectional observational study, 120 patients with radiographically confirmed varus gonarthrosis underwent three-dimensional gait analysis at their typical walking speed. We used sequential (hierarchical) linear regression to examine the amount of variance in dynamic knee joint load (external knee adduction moment) explained by static lower limb alignment (mechanical axis angle) and gait kinematics determined a priori based on their proposed effect on knee load (walking speed, toe-out angle, and lateral trunk lean angle). RESULTS Approximately 50% of the variation in the first peak external knee adduction moment was explained by mechanical axis angle (25%), Western Ontario and McMaster Universities Osteoarthritis Index pain score (1%), gait speed (1%), toe-out angle (12%), and lateral trunk lean angle (13%). There was no confounding or interaction with Kellgren and Lawrence grade of severity. CONCLUSIONS Gait kinematics, particularly lateral trunk lean, explain substantial variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis. While largely ignored in previous gait studies, the effect of lateral trunk lean should be considered in future research evaluating risk factors and interventions for progression of knee osteoarthritis.

Radiographic Measures of Knee Alignment in Patients With Varus Gonarthrosis Effect of Weightbearing Status and Associations With Dynamic Joint Load

Background Radiographic measures of lower limb malalignment are used to indicate abnormal loading of the knee and to plan corrective procedures. Hypotheses Weightbearing status during hip-to-ankle radiographs will significantly affect malalignment measures; malalignment in single-limb standing will be most highly correlated to the external knee adduction moment during gait, a proposed dynamic measure of functional knee joint load. Study Design Controlled laboratory study. Methods Mechanical axis angle was measured in 40 patients with varus gonarthrosis from hip-to-ankle radiographs taken with patients in single-limb standing, double-limb standing, and supine positions. Kinematic and kinetic data were collected during walking and used to calculate the peak adduction moment about the knee. Results Repeated-measures analysis of variance and Scheffé post hoc tests indicated that mechanical axis angle measured on single-limb standing radiographs (-8.7°± 4.0°) was significantly greater than on double-limb standing radiographs (-7.1°± 3.8°), which was significantly greater than on supine radiographs (-5.5°± 2.8°). The peak knee adduction moment (2.8 ± 0.8 percentage body weight × height) was only moderately correlated with mechanical axis angle on single-limb standing (r = -0.46), double-limb standing (r = -0.45), and supine (r = -0.43) radiographs. Conclusion Patient position significantly affects frontal plane knee alignment. However, the peak knee adduction moment is only moderately correlated to mechanical axis angle, regardless of weightbearing status. Clinical Relevance These findings are inconsistent with the hypothesis that mechanical axis angle measured in single-limb standing is more representative of dynamic joint load and further highlight the differences between static and dynamic measures. Results also underscore the importance of reporting patient position during radiographs and keeping positions consistent when evaluating patients over time.

Medial opening wedge high tibial osteotomy: A prospective cohort study of gait, radiographic, and patient-reported outcomes

OBJECTIVE To evaluate the effect of medial opening wedge high tibial osteotomy on gait, radiographic, and patient-reported outcomes over a 2-year postoperative period in patients with varus alignment and medial compartment knee osteoarthritis, and to identify significant predictors of outcome. METHODS We used an observational cohort study design and prospectively administered 3-dimensional quantitative gait analysis, hip to ankle weight-bearing radiographs, and patient-reported outcomes preoperatively and 6, 12, 18, and 24 months postoperatively. Observed changes with 95% confidence intervals (95% CIs) were calculated. Multivariate linear regression and cluster analysis were used to evaluate associations between patient characteristics and 2-year outcomes in dynamic knee joint load (external knee adduction moment during gait) and Knee Injury and Osteoarthritis Outcome Scores (KOOS). RESULTS A total of 126 patients (mean age 47.48 years) were included in the study. Mean changes suggested clinically important improvements in malalignment (change in mechanical axis angle 8.04 degrees [95% CI 7.16 degrees , 8.93 degrees ]), medial compartment load during gait (change in knee adduction moment -1.38 [95% CI -1.53, -1.22] percentage body weight x height), and all KOOS domain scores (change in pain 23.19 [95% CI 19.49, 26.89] KOOS points). A small (13%) increase in knee adduction moment was observed from 6 to 24 months postoperatively. Few preoperative clinical and/or gait characteristics assessed at baseline were significantly associated with 2-year outcomes. CONCLUSION A medial opening wedge high tibial osteotomy with correction to approximately neutral alignment produces substantial and clinically important changes in dynamic knee joint load and patient-reported measures of pain, function, and quality of life 2 years postoperatively. Changes in knee adduction moment observed in the first 2 years postoperatively should be explored as potential predictors of longer-term success and subgroups of patients with poor outcomes.

Evidence of a pelvis-driven flexion pattern: Are the joints of the lower lumbar spine fully flexed in seated postures?

BACKGROUND Seated postures are achieved with a moderate amount of lumbo-sacral flexion and sustained lumbo-sacral spine flexion has been associated with detrimental effects to the tissues surrounding a spinal joint. The purpose of this study was to determine if the lower intervertebral joints of the lumbo-sacral spine approach their end ranges of motion in seated postures. METHODS Static sagittal digital X-ray images of the lumbo-sacral region from L3 to the top of the sacrum were obtained in five standing and seated postures from 27 participants. Vertebral body bony landmarks were manually digitized and intervertebral joint angles were calculated for the three lower lumbo-sacral joints. FINDINGS In upright sitting, the L5/S1 intervertebral joint was flexed to more than 60% of its total range of motion. Each of the lower three intervertebral joints approached their total flexion angles in the slouched sitting posture. These observations were the same regardless of gender. The results support the idea that lumbo-sacral flexion is driven by rotation of the pelvis and lower intervertebral joints in seated postures. INTERPRETATION This is the first study to quantitatively show that the lower lumbo-sacral joints approach their total range of motion in seated postures. While not directly measured, the findings suggest that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting.

Quantifying skin motion artifact error of the hindfoot and forefoot marker clusters with the optical tracking of a multi-segment foot model using single-plane fluoroscopy

The trajectories of skin-mounted markers tracked with optical motion capture are assumed to be an adequate representation of the underlying bone motions. However, it is well known that soft tissue artifact (STA) exists between marker and bone. This study quantifies the STA associated with the hindfoot and midfoot marker clusters of a multi-segment foot model. To quantify STA of the hindfoot and midfoot marker clusters with respect to the calcaneus and navicular respectively, fluoroscopic images were collected on 27 subjects during four quasi-static positions, (1) quiet standing (non-weight bearing), (2) at heel strike (weight-bearing), (3) at midstance (weight-bearing) and (4) at toe-off (weight-bearing). The translation and rotation components of STA were calculated in the sagittal plane. Translational STA at the calcaneus varied from 5.9±7.3mm at heel-strike to 12.1±0.3mm at toe-off. For the navicular the translational STA ranged from 7.6±7.6mm at heel strike to 16.4±16.7mm at toe-off. Rotational STA was relatively smaller for both bones at all foot positions. For the calcaneus they varied between 0.1±2.2° at heel-strike to 0.2±0.6° at toe-off. For the navicular, the rotational STA ranged from 0.6±0.9° at heel-strike to 0.7±0.7° at toe-off. The largest translational STA found in this study (16mm for the navicular) was smaller than those reported in the literature for the thigh and the lower leg, but was larger than the STA of individual spherical markers affixed to the foot. The largest errors occurred at toe-off position for all subjects for both the hindfoot and midfoot clusters. Future studies are recommended to quantify true three-dimensional STA of the entire foot during gait.

An analysis of the mechanisms for reducing the knee adduction moment during walking using a variable stiffness shoe in subjects with knee osteoarthritis

Variable stiffness shoes that have a stiffer lateral than medial sole may reduce the external knee adduction moment (EKAM) and pain during walking in patients with medial compartment knee osteoarthritis (OA). However, the mechanism by which EKAM may be reduced in the OA knee with this intervention remains unclear. Three hypotheses were tested in this study: (1) The reduction in EKAM during walking with the variable stiffness shoe is associated with a reduction in GRF magnitude and/or (2) frontal plane lever arm. (3) A reduction in frontal plane lever arm occurs either by moving the center of pressure laterally under the shoe and/or by dynamically reducing the medial component of GRF. Thirty-two subjects (20 male, 12 female; age: 58.7 ± 9.3 years; height: 1.62 ± 0.08 m; mass: 81.3 ± 14.6 kg) with medial compartment knee osteoarthritis were studied walking in a gait laboratory. The frontal plane lever arm was significantly reduced (1.62%, 0.07%ht, p=0.02) on the affected side while the magnitude of the GRF was not significantly changed. The reduction in the lever arm was weakly correlated with a medial shift in the COP. However, the combined medial shift in the COP and reduction in the medial GRF explained 50% of the change of the frontal plane lever arm. These results suggest that the medial shift in the COP at the foot produced by the intervention shoe stimulates an adaptive dynamic response during gait that reduces the frontal plane lever arm.

Combined Effects of a Valgus Knee Brace and Lateral Wedge Foot Orthotic on the External Knee Adduction Moment in Patients With Varus Gonarthrosis

OBJECTIVE To test the hypothesis that a custom-fit valgus knee brace and custom-made lateral wedge foot orthotic will have greatest effects on decreasing the external knee adduction moment during gait when used concurrently. DESIGN Proof-of-concept, single test session, crossover trial. SETTING Biomechanics laboratory within a tertiary care center. PARTICIPANTS Patients (n=16) with varus alignment and knee osteoarthritis (OA) primarily affecting the medial compartment of the tibiofemoral joint (varus gonarthrosis). INTERVENTIONS Custom-fit valgus knee brace and custom-made full-length lateral wedge foot orthotic. Amounts of valgus angulation and wedge height were tailored to each patient to ensure comfort. MAIN OUTCOME MEASURES The external knee adduction moment (% body weight [BW]*height [Ht]), frontal plane lever arm (cm), and ground reaction force (N/kg), determined from 3-dimensional gait analysis completed under 4 randomized conditions: (1) control (no knee brace, no foot orthotic), (2) knee brace, (3) foot orthotic, and (4) knee brace and foot orthotic. RESULTS The reduction in knee adduction moment was greatest when concurrently using the knee brace and foot orthotic (effect sizes ranged from 0.3 to 0.4). The mean decrease in first peak knee adduction moment compared with control was .36% BW*Ht (95% confidence interval [CI], -.66 to -.07). This was accompanied by a mean decrease in frontal plane lever arm of .59cm (95% CI, -.94 to -.25). CONCLUSIONS These findings suggest that using a custom-fit knee brace and custom-made foot orthotic concurrently can produce a greater overall reduction in the knee adduction moment, through combined effects in decreasing the frontal plane lever arm.

Electromyography and Kinematics of the Trunk during Rowing in Elite Female Rowers

PURPOSE The purpose of this study was to characterize the EMG of trunk muscles together with kinematics of the pelvis and the spine of elite female rowers during the rowing stroke. METHODS Nine Rowing Canada national team candidates performed a 2000-m race simulation. EMG activity of spinal and pelvic extensor and flexor muscles and kinematic data of the pelvis and the spine were collected and analyzed during the period of peak force production. RESULTS During this period, pelvic and spinal extensor muscles demonstrated similarities in the timing of muscle activity with minimal coactivation of flexors and extensors. Minimal excursion of spinal segments occurred during the stroke with most of the extension occurring at the pelvis. Flexor activity occurred toward late drive, suggesting that trunk extension is slowed by increasing activity of the flexor muscles. CONCLUSIONS This study provides data of trunk kinematics and muscle recruitment patterns in elite female rowers. During the period of peak force production, there is minimal coactivation of trunk flexor and extensor muscles and, of the spinal segments, L3-S1 shows the most movement, which may make it more susceptible to soft tissue injury.

Foot segment kinematics during normal walking using a multisegment model of the foot and ankle complex

Gait analysis using optical tracking equipment has been demonstrated to be a clinically useful tool for measuring three-dimensional kinematics and kinetics of the human body. However, in current practice, the foot is treated as a single rigid segment that articulates with the lower leg, meaning the motions of the joints of the foot cannot be measured. A multisegment kinematic model of the foot was developed for use in a gait analysis laboratory. The foot was divided into hindfoot, talus, midfoot, and medial and lateral forefoot segments. Six functional joints were defined: Ankle and subtalar joints, frontal and transverse plane motions of the hindfoot relative to midfoot, supination-pronation twist of the forefoot relative to midfoot, and medial longitudinal arch height-to-length ratio. Twelve asymptomatic subjects were tested during barefoot walking with a six-camera optical stereometric system and passive markers organized in triads. Repeatability of reported motions was tested using coefficients of multiple correlation. Ankle and subtalar joint motions and twisting of the forefoot were most repeatable. Hindfoot motions were least repeatable both within subjects and between subjects. Hindfoot and forefoot pronations in the frontal place were found to coincide with dropping of the medial longitudinal arch between early to midstance, followed by supination and rising of the arch in late stance and swing phase. This multisegment foot model overcomes a major shortcoming in current gait analysis practice-the inability to measure motion within the foot. Such measurements are crucial if gait analysis is to remain relevant in orthopaedic and rehabilitative treatment of the foot and ankle.

Comparative accuracy of radiostereometric and optical tracking systems

This study aims to quantify and compare the accuracy of traditional radiostereometric analysis (RSA), fluoroscopic RSA (fRSA), and optical tracking systems. Three phantoms were constructed, each having three stainless steel spheres and three reflective markers. One phantom was mounted to the base of a precision cross-slide table, one to the base of a precision rotation table, and the third was mounted to each moveable tabletop. Two dial-gauges, rigidly mounted to the cross-slide table and rotation table, quantified translations and rotations. Two fluoroscopy units placed orthogonally tracked the steel spheres while a four-camera optical motion capture system tracked the reflective markers in three-dimensional space. RSA was performed with both digital radiography and fluoroscopy. Three axes of translation were tested: parallel to one fluoroscopy image, parallel to the other fluoroscopy image, and at approximately 45 degrees to each image. One axis of rotation was tested. Intraclass correlation coefficients indicated excellent agreement between the actual (dial-gauge) and measured translations for all modalities (ICCs>0.99) and excellent agreement between actual and measured rotations for RSA and fRSA (ICCs>0.99). Standard errors of measurement ranged from 0.032 mm and 0.121 degrees for RSA, to 0.040 mm and 0.229 degrees for fRSA, and to 0.109 mm and 0.613 degrees for optical tracking. Differences between actual and measured translations along the 45 degrees axis were significantly smaller than the two parallel axes. These findings suggest that under ideal conditions, accuracy of fRSA is comparable to traditional RSA, and superior to optical tracking. Accuracy is highest when measured at 45 degrees to the fluoroscopy units.