Tendinopathy alters ultrasound transmission in the patellar tendon during squatting.

Measurement of loading patterns of the patellar tendon during activity is important in understanding tendon injury. We used transmission-mode ultrasonography to investigate patellar tendon loading during squatting in adults with and without tendinopathy. It was hypothesized that axial ultrasonic velocity, a surrogate measure of the elastic modulus of tendon, would be lower in tendinopathy. Ultrasound velocity was measured in both patellar tendons of adults with unilateral patellar tendinopathy (n = 9) and in healthy controls (n = 16) during a bilateral squat maneuver. Sagittal knee movement was measured simultaneously with an electrogoniometer. Statistical comparisons between healthy and injured tendons were made using two-way mixed-design ANOVAs. Axial ultrasound velocity in both symptomatic and asymptomatic patellar tendons in tendinopathy was approximately 15% higher than in healthy tendons at the commencement (F1,23  = 5.2, P < 0.05) and completion (F1,23  = 4.5, P < 0.05) of the squat. While peak velocity was ≈5% higher during both flexion (F1,23  = 5.4, P < 0.05) and extension (F1,23  = 5.3, P < 0.05) phases, there was no significant between-group difference at the midpoint of the movement. There were no significant differences in the rate and magnitude of knee movement between groups. Although further research is required, these findings suggest enhanced baseline muscle activity in patellar tendinopathy and highlight fresh avenues for its clinical management.

Achilles tendon loading patterns during barefoot walking and slow running on a treadmill: An ultrasonic propagation study.

Measurement of tendon loading patterns during gait is important for understanding the pathogenesis of tendon "overuse" injury. Given that the speed of propagation of ultrasound in tendon is proportional to the applied load, this study used a noninvasive ultrasonic transmission technique to measure axial ultrasonic velocity in the right Achilles tendon of 27 healthy adults (11 females and 16 males; age, 26 ± 9 years; height, 1.73 ± 0.07 m; weight, 70.6 ± 21.2 kg), walking at self-selected speed (1.1 ± 0.1 m/s), and running at fixed slow speed (2 m/s) on a treadmill. Synchronous measures of ankle kinematics, spatiotemporal gait parameters, and vertical ground reaction forces were simultaneously measured. Slow running was associated with significantly higher cadence, shorter step length, but greater range of ankle movement, higher magnitude and rate of vertical ground reaction force, and higher ultrasonic velocity in the tendon than walking (P < 0.05). Ultrasonic velocity in the Achilles tendon was highly reproducible during walking and slow running (mean within-subject coefficient of variation < 2%). Ultrasonic maxima (P1, P2) and minima (M1, M2) were significantly higher and occurred earlier in the gait cycle (P1, M1, and M2) during running than walking (P < 0.05). Slow running was associated with higher and earlier peaks in loading of the Achilles tendon than walking.

Eccentric calf muscle exercise produces a greater acute reduction in Achilles tendon thickness than concentric exercise.

OBJECTIVE: To investigate the acute effects of isolated eccentric and concentric calf muscle exercise on Achilles tendon sagittal thickness. DESIGN: Within-subject, counterbalanced, mixed design. SETTING: Institutional. PARTICIPANTS: 11 healthy, recreationally active male adults. INTERVENTIONS: Participants performed an exercise protocol, which involved isolated eccentric loading of the Achilles tendon of a single limb and isolated concentric loading of the contralateral, both with the addition of 20% bodyweight. MAIN OUTCOME MEASUREMENTS: Sagittal sonograms were acquired prior to, immediately following and 3, 6, 12 and 24 h after exercise. Tendon thickness was measured 2 cm proximal to the superior aspect of the calcaneus. RESULTS: Both loading conditions resulted in an immediate decrease in normalised Achilles tendon thickness. Eccentric loading induced a significantly greater decrease than concentric loading despite a similar impulse (-0.21 vs -0.05, p<0.05). Post-exercise, eccentrically loaded tendons recovered exponentially, with a recovery time constant of 2.5 h. The same exponential function did not adequately model changes in tendon thickness resulting from concentric loading. Even so, recovery pathways subsequent to the 3 h time point were comparable. Regardless of the exercise protocol, full tendon thickness recovery was not observed until 24 h. CONCLUSIONS: Eccentric loading invokes a greater reduction in Achilles tendon thickness immediately after exercise but appears to recover fully in a similar time frame to concentric loading.

Ground reaction forces at discrete sites of the foot derived from pressure plate measurements.

While the literature is replete with studies investigating the pressure beneath the human foot during walking, ground reaction forces experienced at discrete sites may provide a more valuable insight into its mechanical behavior during gait. Despite the fact that changes in the distribution of force have been reported to occur with both foot deformity and fatigue, site-specific force data for nonpathological gait is not well documented. The current study provides an indirect estimate of force and accompanying temporal parameters, for discrete sites of the foot in young, healthy adults walking at their preferred speed.

Evaluating the cutaneous involvement in scleroderma: torsional stiffness revisited.

OBJECTIVE: The pace, progression and extent of the skin lesions in scleroderma may parallel the risk of new internal organ involvement and the progression of existing internal lesions. Accurate assessment of cutaneous change permits an evaluation of patient prognosis and the response to therapy. The aim of this study was to assess a simple device for measuring skin stiffness for its ability to measure sclerodermatous skin in a quantitative and reproducible manner. Materials and methods. Torsional skin stiffness was measured in 56 normal subjects and 42 scleroderma patients (31 of whom had the limited form and nine the diffuse form, and two had mixed connective tissue disease). Data for the scleroderma patients were compared with data obtained by the use of the modified Rodnan clinical skin scoring technique. Intraclass correlation coefficients (ICCs) were calculated as a measure of intraobserver and interobserver variability. RESULTS: For the left and right hands respectively, the ICCs for intraobserver variability were 0.908 and 0.906 and those for interobserver variability were 0.871 and 0.628. There was a significant difference in mean angular rotation obtained by normal subjects compared with scleroderma patients (15.1 vs 11.3 degrees, P<0.001). There was a significant difference in the angular rotation with increasing severity of skin involvement (skin score 0, median rotation 16.3 degrees; score 1, 10.5 degrees; score 2, 8.5 degrees; score 3, 8.0 degrees; P<0.00001). CONCLUSIONS: The measurements obtained with the skin stiffness device are highly reproducible and are consistent with the current clinical method of assessment of skin involvement. The significant difference in angular rotation obtained by normal subjects and scleroderma patients indicates that the device can distinguish normal from sclerodermatous skin. The torsional stiffness measurements derived from the device may also be useful in longitudinal studies.

The effect of visual targeting on ground reaction force and temporospatial parameters of gait.

BACKGROUND: Visual targeting has been cited as a confounding factor for gait analysis in which measures of ground reaction force and plantar pressure are obtained. OBJECTIVE: To investigate the effect of visual targeting on temporospatial and kinetic aspects of gait when small targets, such as pressure platforms, have to be used. DESIGN: A within subjects repeated measure design was used to measure step parameters and ground reaction forces of 11 healthy volunteers. METHODS: Subjects were required to walk over a 10 m walkway at a self-selected pace. A 30x24 cm(2) target area was superimposed over a hidden Kistler force plate (60x90 cm(2)) mounted at the midpoint of the walkway. Step parameters and ground reaction forces were measured with and without the presence of the target. Ground reaction forces were analysed within the time-domain. RESULTS: Subjects used visual control strategies when approaching targets of similar dimensions to a pressure platform. These strategies were manifested by an increase in the variability of the step length onto the target (P<0.05). However, targeting was observed to have no affect on the magnitude, timing and variability of ground reaction forces when measured within the time-domain and averaged over five trials (P>0.05). CONCLUSIONS: Visual control strategies employed while walking toward a target area have no affect on ground reaction force parameters when measured within the time-domain. RELEVANCE: These findings demonstrate that targeting a 30x24 cm(2) target does not affect ground reaction force parameters, when a gait protocol that fine-tunes the start position is employed. The findings are relevant to gait research in which small force or pressure platforms are used to assess gait kinetics.

A comparison of gait initiation and termination methods for obtaining plantar foot pressures.

The midgait protocol is the most commonly used method to collect pressure platform data. Spatial limitations, however, frequently render this technique unsuitable. Alternative gait protocols have focused on gait initiation procedures in obtaining data. The current study investigated whether a commonly cited two-step gait initiation protocol, or a two-step gait termination protocol produced pressure data more representative of the criterion, midgait method. A pressure platform was used to collect data for 25 asymptomatic subjects using the midgait, two-step gait initiation and two-step gait termination walking protocols. The contact duration, percentage contact duration, peak pressure, peak force, pressure-time integral and force-time integral were calculated for seven sites within the foot. Multivariate analysis of variance with repeated measures identified significant protocol by site interactions for all variables except the force-time integral. The gait initiation protocol, although having minimal effect on peak pressures beneath the forefoot, markedly altered the relative timing parameters of the foot. In contrast, the gait termination protocol had minimal effect on temporal parameters, but resulted in a reduction in pressures beneath the forefoot. Abbreviated gait protocols are often employed in plantar pressure studies. This study suggests that the choice between a gait initiation and termination protocol is largely dependent on the gait parameter of interest.

Serial measurement of calcaneal pitch during midstance.

Although emerging evidence suggests a causal relationship between arch structure and musculoskeletal injury, few investigations have adequately assessed arch function during gait. In this study, digitized videofluoroscopy was used to evaluate the sagittal plane motion of the calcaneus during gait. Nine female subjects requiring diagnostic foot radiographs underwent videofluoroscopy. The calcaneal inclination angle, arch height ratio, and tarsal index were digitally analyzed for all radiographic images. Calcaneal pitch was correlated to both the arch height ratio and the tarsal index. Repeated measures analysis of variance helped to identify a significant reduction in the mean calcaneal pitch during the midstance and early propulsive periods of gait. These findings suggest that although calcaneal pitch may be used as an indicator of rearfoot position, biomechanical classification of foot types based on radiographs may result in erroneous conclusions concerning foot function.

Morphometry of human lumbar apophyseal joints. A novel technique.

STUDY DESIGN: The anatomy of cadaveric lumbar apophyseal joints was examined as part of a study of possible correlations between lumbar apophyseal morphology, arthrosis, and cartilage thickness and stiffness. OBJECTIVES: To establish the morphometry of human upper lumbar apophyseal joints using an objective technique. SUMMARY OF BACKGROUND DATA: The apophyseal joints of 30 unfixed lumbar motion segments, all from different cadavers (24 male, five female, and one unknown, mean age 35 years, range 16-78 years) were exposed by dissection and disarticulation. Twenty-five motion segments were L1-L2, three were L2-L3, and two were L3-L4. The extent of fibrillation and linear dimensions of 29 of these specimens were examined, whereas the vertebrae and joints of 22 of them (18 being L1-L2) were cast in araldite resin. METHODS: The casts of the vertebrae were sectioned cephalocaudally at 1-mm intervals. Image processing of photographic slides of the sections established the orientations and dimensions of the lumbar apophyseal joints and their shapes using Fourier analysis. RESULTS: Apophyseal joint surface area was 158 +/- 43 mm2, cephalocaudal length 15.2 +/- 2.7 mm, and straight line length between anterior and posterior borders was 13.2 +/- 1.9 mm. The joints were orientated at 62.5 +/- 11.8 degrees to the coronal plane. Average maximum depth of concavity was 1.8 +/- 0.7 mm. The posterior edges of two joint pairs twisted inward toward the midsagittal plane in a cephalocaudal direction; thus, some apophyseal joints bear part of the axial spinal load. The right inferior surfaces were more elongated cephalocaudally (but not longer) than their contralateral partners. Inferior apophyses were significantly more elongated cephalocaudally (but not longer) than their ipsilateral articulating superior surfaces. CONCLUSIONS: In theory, Fourier analysis of joint surfaces was objective, but it dictated the criterion by which joints were grouped; care must be exercised so that measurement methods do not categorize joints artificially. "Symmetry" is too subjective to be applied to contralateral apophyseal joints; correlation coefficients should be quoted for areas and orientations. The morphology of contralateral lumbar apophyseal joint pairs was significantly correlated in all respects, as was the morphology of articulating lumbar apophyseal surfaces.

Human lumbar apophyseal joint damage and intervertebral disc degeneration.

OBJECTIVES: To record the extent and location of lumbar apophyseal cartilage damage, and to ascertain if the extent of damage is correlated with the grade of disc degeneration, age, or both. METHODS: The extent and location of fibrillated areas of the apophyseal cartilage of the joint surfaces of 29 lumbar motion segments were examined using computer aided image processing of Indian ink stained areas, and degeneration of the associated intervertebral discs graded using the method of Nachemson. RESULTS: It was found that these joints showed a greater extent and prevalence of cartilage fibrillation than the knee, hip or ankle, with significant damage in specimens younger than 30 years. Damage was predominantly located peripherally, superiorly, and posteriorly in the concave superior apophyseal surfaces, and was predominantly peripheral and posterior in the inferior surfaces, with a tendency to be located inferiorly. There was a weak correlation between apophyseal joint damage and the intervertebral disc degenerative grade, but this was inconclusive, as both increased with age. CONCLUSIONS: The pattern of damage exhibited by superior joint surfaces is most probably caused by tension on collagenous joint capsule fibres which insert into the surfaces posteriorly, so producing an area of fibrocartilage unsuited to loadbearing. Tension on such fibres would be greatest during spinal flexion. The pattern of damage of the inferior surfaces lends some support to the hypothesis that their apices impact the laminae of the lumbar vertebra inferior to them, consequent upon the degeneration and narrowing of the associated intervertebral disc. The predominantly peripheral location of fibrillation of both superior and inferior surfaces may be associated with inadequate mechanical conditioning of marginal joint areas. Disc degeneration cannot be the initial cause of apophyseal fibrillation in most specimens. The study indicates a need for regular spinal exercise, starting at a young age.

Work related upper limb disorder: the relationship between pain, cumulative load, disability, and psychological factors.

Repetitive strain injury, or work related upper limb disorder, provides an interesting paradigm for the study of the relative contribution of physical and psychological factors to the resulting pain and disability. Sixty three subjects were studied, comprising the work-force of a subsection of a large local industrial company, in whom pain in the arm related to work was known to be common. Ergonomic data were obtained by estimating the cumulative daily load on the wrist joint for each of four identified tasks. Data on the occurrence of pain, treatment sought, and disability were obtained by a structured self administered questionnaire. Psychological data were obtained by administering the Hospital Anxiety and Depression (HAD) scale, a self reported measure of anxiety and depression, and the Bradford Somatic Inventory (BSI), an inventory of somatic symptoms associated with anxiety and depression. The employment specific period prevalence of work related upper limb disorder was 81%, with 30% of the subjects having pain at the time of the study. Domestic disability was minimal in all but two subjects, though the use of devices such as jar openers at home was common (12 of 51 subjects). Medical advice was seldom sought. Twenty per cent of subjects had received anti-inflammatory drugs, 10% had received physiotherapy, and 47% had wrist splints. Pain was related to the tasks with the highest estimated daily loads, but a history of pain and current pain were associated with higher scores on the HAD and BSI scales, suggesting an interaction between physical and psychological factors.

Transient vibrations caused by heel strike.

Transient vibrations caused by heel strike and travelling vertically through the body have been monitored using accelerometers taped to the skin. A correction for skin movement based on the transmissibility function is described. The average velocity between the foot and the head for the heel-strike transient is 220 m/s. This velocity is greatest in the legs, 610 m/s, and least in the spine, 90 m/s. Shock absorption occurs mainly in the legs and to a lesser degree in the spine.

Shock absorption by the spinal column in normals and in ankylosing spondylitis.

The transmission of heel-strike vibration using skin-mounted accelerometers was measured in normal subjects and subjects with ankylosing spondylitis. In normal subjects transmissibility was enhanced between 5 and 13 Hz and attenuated at frequencies above 15 Hz. In ankylosing spondylitis transmissibility was enhanced at 4 Hz but less so between 5 and 13 Hz and little attenuation was observed at the higher frequencies. This difference is expected in view of the pathological changes occurring in the spinal column in ankylosing spondylitis. The results support the hypothesis that the normal spinal column has to bend in order to absorb vibrations with a frequency greater than 15 Hz.

Measurement of transmissibility for the human spine during walking and running.

A method for measuring the transmissibility of the human spinal column to vertical vibrations using light-weight, skin-mounted accelerometers is described. The accelerometers were conveniently attached to the skin at the S2 and T2 levels of the spine using adhesive tape. The acceleration time records were analysed using a discrete Fourier transform to calculate the amplitude for each frequency component up to 40 Hz. Transmissibility was estimated as the ratio of the output over the input for each frequency component. The analysis included a compensation for both skin movement and differences in the inclination of the spine from the vertical at the accelerometer mounting sites. The healthy spine was observed to attenuate frequency components above 20 Hz, whereas in ankylosing spondylitis the spine behaved as a rigid strut.

Dynamic compressive properties of human lumbar intervertebral joints: a comparison between fresh and thawed specimens.

A comparison between the dynamic compressive properties of human lumbar intervertebral joints when fresh and after a period of deep frozen storage was made. Physiologically relevant loads of -750 +/- 250 N were applied in axial compression with the joint constrained against bending, over a frequency range of 0.01-10 Hz. Frozen storage was found not to affect the compressive stiffness or hysteresis of the seven joints. The magnitude of the observed changes in mean values were small, less than 1% decrease in the compressive stiffness and less than 1% increase in hysteresis after deep frozen storage.