Medial Longitudinal Arch Angle Presents Significant Differences Between Foot Types: A Biplane Fluoroscopy Study.

The structure of the medial longitudinal arch (MLA) affects the foot's overall function and its ability to dissipate plantar pressure forces. Previous research on the MLA includes measuring the calcaneal-first metatarsal angle using a static sagittal plane radiograph, a dynamic height-to-length ratio using marker clusters with a multisegment foot model, and a contained angle using single point markers with a multisegment foot model. The objective of this study was to use biplane fluoroscopy to measure a contained MLA angle between foot types: pes planus (low arch), pes cavus (high arch), and normal arch. Fifteen participants completed the study, five from each foot type. Markerless fluoroscopic radiostereometric analysis (fRSA) was used with a three-dimensional model of the foot bones and manually matching those bones to a pair of two-dimensional radiographic images during midstance of gait. Statistically significant differences were found between barefoot arch angles of the normal and pes cavus foot types (p = 0.036), as well as between the pes cavus and pes planus foot types (p = 0.004). Dynamic walking also resulted in a statistically significant finding compared to the static standing trials (p = 0.014). These results support the classification of individuals following a physical assessment by a foot specialist for those with pes cavus and planus foot types. The differences between static and dynamic kinematic measurements were also supported using this novel method.

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.

Video analysis of the biomechanics of a bicycle accident resulting in significant facial fractures.

INTRODUCTION: This study aimed to use video analysis techniques to determine the velocity, impact force, angle of impact, and impulse to fracture involved in a video-recorded bicycle accident resulting in facial fractures. Computed tomographic images of the resulting facial injury are presented for correlation with data and calculations. To our knowledge, such an analysis of an actual recorded trauma has not been reported in the literature. MATERIALS AND METHODS: A video recording of the accident was split into frames and analyzed using an image editing program. Measurements of velocity and angle of impact were obtained from this analysis, and the force of impact and impulse were calculated using the inverse dynamic method with connected rigid body segments. These results were then correlated with the actual fracture pattern found on computed tomographic imaging of the subject's face. RESULTS: There was an impact velocity of 6.25 m/s, impact angles of 14 and 6.3 degrees of neck extension and axial rotation, respectively, an impact force of 1910.4 N, and an impulse to fracture of 47.8 Ns. These physical parameters resulted in clinically significant bilateral mid-facial Le Fort II and III pattern fractures. DISCUSSION: These data confer further understanding of the biomechanics of bicycle-related accidents by correlating an actual clinical outcome with the kinematic and dynamic parameters involved in the accident itself and yielding a concrete evidence of the velocity, force, and impulse necessary to cause clinically significant facial trauma. These findings can aid in the design of protective equipment for bicycle riders to help avoid this type of injury.

Image intensifier distortion correction for fluoroscopic RSA: the need for independent accuracy assessment.

Fluoroscopic images suffer from multiple modes of image distortion. Therefore, the purpose of this study was to compare the effects of correction using a range of two-dimensional polynomials and a global approach. The primary measure of interest was the average error in the distances between four beads of an accuracy phantom, as measured using RSA. Secondary measures of interest were the root mean squared errors of the fit of the chosen polynomial to the grid of beads used for correction, and the errors in the corrected distances between the points of the grid in a second position. Based upon the two-dimensional measures, a polynomial of order three in the axis of correction and two in the perpendicular axis was preferred. However, based upon the RSA reconstruction, a polynomial of order three in the axis of correction and one in the perpendicular axis was preferred. The use of a calibration frame for these three-dimensional applications most likely tempers the effects of distortion. This study suggests that distortion correction should be validated for each of its applications with an independent "gold standard" phantom.

RSA calibration accuracy of a fluoroscopy-based system using nonorthogonal images for measuring functional kinematics.

When performing radiostereometric analysis (RSA) in a clinical setting it may be desirable to orient the two imaging devices nonorthogonally to obtain the best views of an anatomical structure. In this study, a calibration frame was constructed that allowed the relative angles of fiducial and control planes to be adjusted. Precision and accuracy were quantified across multiple trials and orientations. The 90 degrees frame was always of equivalent or greater accuracy than a calibration frame with the fiducial and control planes aligned parallel to the image intensifiers. This study also showed that RSA may be performed with imaging devices at relative angles other than 90 degrees without compromising accuracy. This allows researchers greater freedom in positioning equipment.

Total kinetic energy production of body segments is different between racing and training paces in elite Olympic rowers.

Total kinetic energy (TKE) was calculated for 28 Canadian national team Olympic rowers during training on water, comparing low-stroke rates (18-22 stroke/min) and high-stroke rates (32-40 stroke/min), using video analysis. Stroke duration was normalized to 100%, beginning and ending at the "catches", with the drive phase occurring first and recovery second. Two discrete points were identified during the stroke, both occurring when the fingers had the same horizontal position as the ankles (i.e., mid-drive and mid-recovery). The ratios of recovery-to-drive TKE at these points for the entire body at low and high-stroke rates were 0.36 +/- 0.34 and 1.26 +/- 0.54 respectively. Significant differences were found for the lower leg, upper arm and forearm segments, and within the female groups. Low-stroke rate is a typical training pace and high-stroke rate is analogous to a race pace. This study demonstrates that TKE production during recovery in a race was not replicated during training. While training at low-stroke rates is vital for technique refinement, this study stresses the importance of training appropriately for the energy expenditure during high-stroke rate recovery. This is commonly overlooked by coaches and athletes.

Hard, soft and off-the-shelf foot orthoses and their effect on the angle of the medial longitudinal arch: A biplane fluoroscopy study.

BACKGROUND: Foot orthoses have proven to be effective for conservative management of various pathologies. Pathologies of the lower limb can be caused by abnormal biomechanics such as irregular foot structure and alignment, leading to inadequate support. OBJECTIVES: To compare biomechanical effects of different foot orthoses on the medial longitudinal arch during dynamic gait using skeletal kinematics. STUDY DESIGN: This study follows a prospective, cross-sectional study design. METHODS: The medial longitudinal arch angle was measured for 12 participants among three groups: pes planus, pes cavus and normal arch. Five conditions were compared: three orthotic devices (hard custom foot orthosis, soft custom foot orthosis and off-the-shelf Barefoot Science©), barefoot and shod. An innovative method, markerless fluoroscopic radiostereometric analysis, was used to measure the medial longitudinal arch angle. RESULTS: Mean medial longitudinal arch angles for both custom foot orthosis conditions were significantly different from the barefoot and shod conditions ( p < 0.05). There was no significant difference between the off-the-shelf device and the barefoot or shod conditions ( p > 0.05). In addition, the differences between hard and soft custom foot orthoses were not statistically significant. All foot types showed a medial longitudinal arch angle decrease with both the hard and soft custom foot orthoses. CONCLUSION: These results suggest that custom foot orthoses can reduce motion of the medial longitudinal arch for a range of foot types during dynamic gait. LEVEL OF EVIDENCE: Therapeutic study, Level 2. CLINICAL RELEVANCE: Custom foot orthoses support and alter the position of the foot during weightbearing. The goal is to eliminate compensation of the foot for a structural deformity or malalignment and redistribute abnormal plantar pressures. By optimizing the position of the foot, the medial longitudinal arch (MLA) will also change and quantifying this change is of interest to clinicians.

Toe-out gait in patients with knee osteoarthritis partially transforms external knee adduction moment into flexion moment during early stance phase of gait: a tri-planar kinetic mechanism.

Altered gait kinematics and kinetics are observed in patients with medial compartment knee osteoarthritis. Although various kinematic adaptations are proposed to be compensatory mechanisms that unload the knee, the nature of these mechanisms is presently unclear. We hypothesized that an increased toe-out angle during early stance phase of gait shifts load away from the knee medial compartment, quantified as the external adduction moment about the knee. Specifically, we hypothesized that by externally rotating the lower limb anatomy, primarily about the hip joint, toe-out gait alters the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes and transforms a portion of knee adduction moment into flexion moment. To test this hypothesis, gait data from 180 subjects diagnosed with medial compartment knee osteoarthritis were examined using two frames of reference. The first frame was attached to the tibia (reporting actual toe-out) and the second frame was attached to the laboratory (simulating no-toe-out). Four measures were compared within subjects in both frames of reference: the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes, and the adduction and flexion components of the external knee moment. The mean toe-out angle was 11.4 degrees (S.D. 7.8 degrees , range -2.2 degrees to 28.4 degrees ). Toe-out resulted in significant reductions in the frontal plane lever arm (-6.7%) and the adduction moment (-11.7%) in early stance phase when compared to the simulated no-toe-out values. These reductions were coincident with significant increases in the sagittal plane lever arm (+33.7%) and flexion moment (+25.0%). Peak adduction lever arm and moment were also reduced significantly in late stance phase (by -22.9% and -34.4%, respectively) without a corresponding increase in sagittal plane lever arm or flexion moment. These results indicate that toe-out gait in patients with medial compartment knee osteoarthritis transforms a portion of the adduction moment into flexion moment in early stance phase, suggesting that load is partially shifted away from the medial compartment to other structures.

Measures of frontal plane lower limb alignment obtained from static radiographs and dynamic gait analysis.

Currently, lower limb alignment is measured statically from radiographs that may not accurately represent the condition of the limb when moving and weight-bearing. Thus, the purpose of the present study was to introduce and examine a novel measure of dynamic lower limb alignment obtained during walking in patients with knee OA. In this cross-sectional study, standing, full-length lower limb radiographs were acquired from 80 individuals with confirmed knee OA, who also underwent three-dimensional gait analyses with reflective markers placed on the segments of the lower limb. Frontal plane lower limb alignment was measured using the static radiographs (mechanical axis) and gait analyses (marker-based alignment) by identifying the centres of the hip, knee, and ankle from both methods. Simple linear regression indicated these measures were highly correlated (r=0.84), however, 30% of the variance in the marker-based measure of lower limb alignment was not explained by the mechanical axis despite using the same anatomical landmarks. Results from this study suggest that a valid measure of dynamic lower limb alignment can be obtained from a standard quantitative gait analysis and highlight the differences in measures of lower limb alignment obtained in static and dynamic situations. Future research into the clinical utility of measures of dynamic alignment in the treatment of OA may aid in the development of interventions specifically tailored to one's dynamic lower limb biomechanics during gait.

Direct comparison of kinematic data collected using an electromagnetic tracking system versus a digital optical system.

The purpose of this study was to quantify the dynamic accuracy of kinematics measured by a digital optical motion analysis system in a gait analysis laboratory (capture volume approximately 20m(3)) compared to a standard range direct-current electromagnetic (EM) tracking device (capture volume approximately 1m(3)). This is a subset of a larger effort to establish an appropriate marker set for the optical system to quantify upperlimb kinematics simultaneously with gait, in comparison to previous studies of isolated upperlimb movements that have employed EM tracking devices. Rigid clusters of spherical reflective markers and EM sensors were attached to a mechanical articulator that mimicked three-dimensional joint rotations, similar to the elbow. As the articulator was moved through known ranges of motion (i.e. gold standard), kinematic data were collected simultaneously using both tracking systems. Both systems were tended to underestimate the range of motion; however, the application of post hoc smoothing and least-squares correction algorithms reduced these effects. When smoothing and correction algorithms were used, the magnitude of the mean difference between the gold standard and either the EM or optical system did not exceed 2 degrees for any of the compound motions performed. This level of agreement suggests that the measurements obtained from either system are clinically comparable, provided appropriate smoothing and correction algorithms are employed.

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 degrees +/- 4.0 degrees) was significantly greater than on double-limb standing radiographs (-7.1 degrees +/- 3.8 degrees), which was significantly greater than on supine radiographs (-5.5 degrees +/- 2.8 degrees). The peak knee adduction moment (2.8 +/- 0.8 percentage body weight x 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.

Associations among knee adduction moment, frontal plane ground reaction force, and lever arm during walking in patients with knee osteoarthritis.

The adduction moment about the knee during walking gait has been proposed as an indirect measure of dynamic knee joint load. However, the relative contributions of the variables primarily used to calculate the knee adduction moment have not been investigated. The objectives of this paper were to: (1) describe and compare the magnitude and temporal characteristics of the knee adduction moment, frontal plane lever arm, and frontal plane ground reaction force (GRF) during gait in patients with knee osteoarthritis (OA) and, (2) examine the associations among these variables. Results indicated that both the knee adduction moment and the frontal plane GRF varied considerably throughout stance and exhibited the characteristic "double-hump" pattern, while the frontal plane lever arm magnitude varied only slightly during stance. Knees with OA had significantly greater peak knee adduction moments and frontal plane lever arms, but significantly less peak frontal plane GRF than knees without OA. Pearson product moment correlations indicated a higher association between peak knee adduction moment and peak frontal plane lever arm than between peak knee adduction moment and peak frontal plane GRF, particularly in knees with OA. These results suggest that the frontal plane lever arm assessed during walking is an important variable in the examination of knee OA, and warrants further investigation.

Five-year changes in gait biomechanics after concomitant high tibial osteotomy and ACL reconstruction in patients with medial knee osteoarthritis.

BACKGROUND: Concomitant high tibial osteotomy (HTO) and anterior cruciate ligament (ACL) reconstruction is a combined surgical procedure intended to improve kinematics and kinetics in the unstable ACL-deficient knee with varus malalignment and medial compartment knee osteoarthritis (OA). PURPOSE: To investigate 5-year changes in gait biomechanics as well as radiographic and patient-reported outcomes bilaterally after unilateral, concomitant medial opening wedge HTO and ACL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 33 patients (mean ± SD age, 40 ± 9 years) with varus malalignment (mean mechanical axis angle, -5.9° ± 2.9°), medial compartment knee OA, and ACL deficiency completed 3-dimensional gait analysis preoperatively and 2 and 5 years postoperatively. Primary outcomes were the peak external knee adduction (first peak) and flexion moments. Secondary outcomes were the peak external knee extension and transverse plane moments, peak knee angles in all 3 planes, radiographic static knee alignment measures (mechanical axis angle and posterior tibial slope), and the Knee injury and Osteoarthritis Outcome Score (KOOS). RESULTS: There was a substantial decrease in the knee adduction moment in the surgical limb (%BW × H, -1.49; 95% CI, -1.75 to -1.22) and a slight increase in the nonsurgical limb (%BW × H, 0.16; 95% CI, 0.03 to 0.30) from preoperatively to 5 years postoperatively. There was also a decrease in the knee flexion moment for both the surgical (%BW × H, -0.67; 95% CI, -1.19 to -0.15) and nonsurgical limbs (%BW × H, -1.06; 95% CI, -1.49 to -0.64). Secondary outcomes suggested that substantial improvements were maintained at 5 years, although smaller declines were observed in several measures and in both limbs from 2 to 5 years. CONCLUSION: Changes in the peak external moments about the knee in all 3 planes during walking were observed 5 years after concomitant medial opening wedge HTO and ACL reconstruction. These findings are consistent with an intended, sustained shift in the mediolateral distribution of knee loads. CLINICAL RELEVANCE: These findings suggest that concomitant HTO and ACL reconstruction results in substantial changes in gait biomechanics. Future clinical research comparing treatment strategies is both warranted and required for this relatively uncommon but seemingly biomechanically efficacious procedure.

Finite element model of intramuscular pressure during isometric contraction of skeletal muscle.

The measurement of in vivo intramuscular pressure (IMP) has recently become practical and IMP appears well correlated with muscle tension. A numerical model of skeletal muscle was developed to examine the mechanisms producing IMP. Unipennate muscle is modelled as a two-dimensional material continuum that is incompressible and nonlinearly anisotropic. The finite element technique is used to calculate IMP and muscle stress during passive stretch and during isometric contraction. A novel element models the contractile portion of muscle, incorporating sarcomere length-force and velocity-force relations. A range of unipennate muscle geometries can be modelled. The model was configured to simulate the rabbit tibialis anterior muscle over a range of lengths. Simulated IMP and stress results were validated against animal experimentation data. The simulation agreed well with the experimental data over the range of 0.8-1.1 of the optimal length. Severe pressure gradients were produced near the musculo-tendinous junctions while IMP was more uniform in the central muscle belly. IMP and muscle stress in relaxed (unstimulated) muscle increased nonlinearly with muscle length. IMP and stress in isometrically contracting muscle showed a local maximum at optimal length and were reduced at shorter lengths. At muscle lengths longer than optimal, stress and IMP increased predominately due to tension in the passive elastic structures.

Noninvasive muscle tension measurement using the novel technique of magnetic resonance elastography (MRE).

A novel method for direct measurement of the state of skeletal muscle contraction is introduced called magnetic resonance elastography (MRE). Such a technique is useful for avoiding the indeterminancy inherent in most inverse dynamic models of the musculoskeletal system. Within a standard MRI scanner, mechanical vibration is applied to muscle via the skin, creating shear waves that penetrate the tissue and propagate along muscle fibers. A gradient echo sequence is used with cyclic motion-encoding to image the propagating shear waves using phase contrast. Individual muscles of interest are identified and the shear wavelength in each is measured. Shear wavelength increases with increasing tissue stiffness and increasing tissue tension. Several ankle muscles were tested simultaneously in normal subjects. Applied ankle moment was isometrically resisted at several different foot positions. Shear wavelengths in relaxed muscle in neutral foot position was 2.34 +/- 0.47 cm for tibialis anterior (TA) and 3.13 +/- 0.24 cm for lateral gastrocnemius (LG). Wavelength increased in relaxed muscle when stretched (to 3.80 +/- 0.28 cm for TA in 45 degrees plantar-flexion and to 3.95 +/- 0.43 cm for LG in 20 degrees dorsi-flexion). Wavelength increased more significantly with contraction (to 7.71 +/- 0.97 cm in TA for 16 N m dorsi-flexion effort and to 7.90 +/- 0.34 cm in LG for 48 N m plantar-flexion effort). MRE has been shown to be sensitive to both passive and active tension within skeletal muscle making it a promising, noninvasive tool for biomechanical analysis. Since it is based on MRI technology, any muscle, however deep, can be interrogated using equipment commonly available in most health care facilities.

Reliability of lower limb frontal plane alignment measurements using plain radiographs and digitized images.

This study evaluated the reliability of lower limb frontal plane alignment measures obtained from plain radiographs measured manually and digitized images measured using a custom computer software package (TheHTO Pro; Fowler Kennedy Sport Medicine Clinic, London, Ontario, Canada). Radiographic measurements used in the planning of high tibial osteotomy, including the mechanical axis angle and mechanical axis deviation, were measured on 42 hip-to-ankle radiographs on two separate occasions by two different raters (A.V.S., J.J.D.). Intraclass correlation coefficients (0.96-0.99) indicated excellent agreement between the manual and computer measurements, suggesting both methods can be used interchangeably. Although test-retest and inter-rater reliability tended to be slightly better when using TheHTO Pro, intraclass correlation coefficients were excellent for both methods (0.97-0.99). The standard errors of measurement were <1 degree for mechanical axis angle and <2 mm for mechanical axis deviation, regardless of method or rater. Based on the observed standard errors of measurement, conservative estimates for the error associated with an individual's mechanical axis angle at one point is approximately 1.5 degrees, and the minimal detectable change on reassessment is approximately 2 degrees. The error associated with an individual's mechanical axis deviation at one point is approximately 4 mm, and the minimal detectable change on reassessment is approximately 6 mm. These results suggest that manual and computer measurements of lower limb frontal plane alignment can be calculated with minimal measurement error. However, the small errors associated with both methods should be considered when making clinical decisions.

An analysis of functional shoulder movements during task performance using Dartfish movement analysis software.

PURPOSE: Video-based movement analysis software (Dartfish) has potential for clinical applications for understanding shoulder motion if functional measures can be reliably obtained. The primary purpose of this study was to describe the functional range of motion (ROM) of the shoulder used to perform a subset of functional tasks. A second purpose was to assess the reliability of functional ROM measurements obtained by different raters using Dartfish software. MATERIALS AND METHODS: Ten healthy participants, mean age 29 ± 5 years, were videotaped while performing five tasks selected from the Disabilities of the Arm, Shoulder and Hand (DASH). Video cameras and markers were used to obtain video images suitable for analysis in Dartfish software. Three repetitions of each task were performed. Shoulder movements from all three repetitions were analyzed using Dartfish software. The tracking tool of the Dartfish software was used to obtain shoulder joint angles and arcs of motion. Test-retest and inter-rater reliability of the measurements were evaluated using intraclass correlation coefficients (ICC). RESULTS: Maximum (coronal plane) abduction (118° ± 16°) and (sagittal plane) flexion (111° ± 15°) was observed during 'washing one's hair;' maximum extension (-68° ± 9°) was identified during 'washing one's own back.' Minimum shoulder ROM was observed during 'opening a tight jar' (33° ± 13° abduction and 13° ± 19° flexion). Test-retest reliability (ICC = 0.45 to 0.94) suggests high inter-individual task variability, and inter-rater reliability (ICC = 0.68 to 1.00) showed moderate to excellent agreement. CONCLUSION: KEY FINDINGS INCLUDE: 1) functional shoulder ROM identified in this study compared to similar studies; 2) healthy individuals require less than full ROM when performing five common ADL tasks 3) high participant variability was observed during performance of the five ADL tasks; and 4) Dartfish software provides a clinically relevant tool to analyze shoulder function.

Development and evaluation of a semi-automatic technique for determining the bilateral symmetry plane of the facial skeleton.

During reconstructive surgery of the face, one side may be used as a template for the other, exploiting assumed bilateral facial symmetry. The best method to calculate this plane, however, is debated. A new semi-automatic technique for calculating the symmetry plane of the facial skeleton is presented here that uses surface models reconstructed from computed tomography image data in conjunction with principal component analysis and an iterative closest point alignment method. This new technique was found to provide more accurate symmetry planes than traditional methods when applied to a set of 7 human craniofacial skeleton specimens, and showed little vulnerability to missing model data, usually deviating less than 1.5° and 2 mm from the intact model symmetry plane when 30 mm radius voids were present. This new technique will be used for subsequent studies measuring symmetry of the facial skeleton for different patient populations.

Toe-out, lateral trunk lean, and pelvic obliquity during prolonged walking in patients with medial compartment knee osteoarthritis and healthy controls.

OBJECTIVE: To compare the time-varying behavior of maximum toe-out angle, lateral trunk lean (over the stance leg), and pelvic obliquity (rise and drop on the swing leg) during prolonged walking in participants with and without medial compartment knee osteoarthritis (OA), and to explore correlations between these gait characteristics and pain. METHODS: Twenty patients with knee OA and 20 healthy controls completed 30 minutes of treadmill walking. Toe-out, trunk lean, pelvic obliquity, and pain were measured at 5-minute intervals. RESULTS: The mean ± SD toe-out angle was significantly smaller (P = 0.04) in patients with knee OA (6.7 ± 2.5 degrees) than in controls (10.3 ± 2.2 degrees). Toe-out changed significantly over time (P = 0.002), but not in a systematic way, and there was no interaction between group and time. The mean ± SD trunk lean was higher (P = 0.03) in patients with knee OA (2.0 ± 1.0 degrees) than in controls (0.7 ± 0.5 degrees). Trunk lean did not change over time and there was no interaction between group and time. There were no differences for pelvic drop. The mean ± SD pelvic rise was higher (P = 0.01) in patients with knee OA (2.8 ± 0.9 degrees) than in controls (1.2 ± 0.8 degrees), but did not change over time and there was no interaction. Patients experienced a small increase in pain (P < 0.001). Trunk lean and pelvic drop were correlated with pain (r = 0.49, P = 0.03 and r = 0.47, P = 0.04, respectively). CONCLUSION: Toe-out and trunk lean are consistently different between individuals with and without medial compartment knee OA during prolonged walking, and patients with greater pain have greater trunk lean. However, over 30 minutes of walking, these gait characteristics remain quite stable, suggesting they are not acute compensatory mechanisms in response to repetitive loading with subtle increases in pain.

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.