James E. Smeathers

The Pathomechanics of Plantar Fasciitis

Plantar fasciitis is a musculoskeletal disorder primarily affecting the fascial enthesis. Although poorly understood, the development of plantar fasciitis is thought to have a mechanical origin. In particular, pes planus foot types and lower-limb biomechanics that result in a lowered medial longitudinal arch are thought to create excessive tensile strain within the fascia, producing microscopic tears and chronic inflammation. However, contrary to clinical doctrine, histological evidence does not support this concept, with inflammation rarely observed in chronic plantar fasciitis. Similarly, scientific support for the role of arch mechanics in the development of plantar fasciitis is equivocal, despite an abundance of anecdotal evidence indicating a causal link between arch function and heel pain. This may, in part, reflect the difficulty in measuring arch mechanics in vivo. However, it may also indicate that tensile failure is not a predominant feature in the pathomechanics of plantar fasciitis. Alternative mechanisms including ‘stress-shielding’, vascular and metabolic disturbances, the formation of free radicals, hyperthermia and genetic factors have also been linked to degenerative change in connective tissues. Further research is needed to ascertain the importance of such factors in the development of plantar fasciitis.

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.

Plantar Fasciitis: Are Pain and Fascial Thickness Associated With Arch Shape and Loading?

Background and Purpose: Although plantar fascial thickening is a sonographic criterion for the diagnosis of plantar fasciitis, the effect of local loading and structural factors on fascial morphology are unknown. The purposes of this study were to compare sonographic measures of fascial thickness and radiographic measures of arch shape and regional loading of the foot during gait in individuals with and without unilateral plantar fasciitis and to investigate potential relationships between these loading and structural factors and the morphology of the plantar fascia in individuals with and without heel pain. Subjects: The participants were 10 subjects with unilateral plantar fasciitis and 10 matched asymptomatic controls. Methods: Heel pain on weight bearing was measured by a visual analog scale. Fascial thickness and static arch angle were determined from bilateral sagittal sonograms and weight-bearing lateral foot roentgenograms. Regional plantar loading was estimated from a pressure plate. Results: On average, the plantar fascia of the symptomatic limb was thicker than the plantar fascia of the asymptomatic limb (6.1±1.4 mm versus 4.2±0.5 mm), which, in turn, was thicker than the fascia of the matched control limbs (3.4±0.5 mm and 3.5±0.6 mm). Pain was correlated with fascial thickness, arch angle, and midfoot loading in the symptomatic foot. Fascial thickness, in turn, was positively correlated with arch angle in symptomatic and asymptomatic feet and with peak regional loading of the midfoot in the symptomatic limb. Discussion and Conclusion: The findings indicate that fascial thickness and pain in plantar fasciitis are associated with the regional loading and static shape of the arch.

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.

Sagittal movement of the medial longitudinal arch is unchanged in plantar fasciitis.

BACKGROUND Although a lowered medial longitudinal arch has been cited as a causal factor in plantar fasciitis, there is little experimental evidence linking arch motion to the pathogenesis of the condition. This study investigated the sagittal movement of the arch in subjects with and without plantar fasciitis during gait. METHODS Digital fluoroscopy was used to acquire dynamic lateral radiographs from 10 subjects with unilateral plantar fasciitis and 10 matched control subjects. The arch angle and the first metatarsophalangeal joint angle were digitized and their respective maxima recorded. Sagittal movement of the arch was defined as the angular change between heel strike and the maximum arch angle observed during the stance phase of gait. The thickness of the proximal plantar fascia was determined from sagittal sonograms of both feet. ANOVA models were used to identify differences between limbs with respect to each dependent variable. Relationships between arch movement and fascial thickness were investigated using correlations. RESULTS There was no significant difference in either the movement or maximum arch angle between limbs. However, subjects with plantar fasciitis were found to have a larger metatarsophalangeal joint angle than controls (P < 0.05). Whereas the symptomatic and asymptomatic plantar fascia were thicker than those of control feet (P < 0.05), significant correlations were noted between fascial thickness and peak arch and metatarsophalangeal joint angles (P < 0.05) in the symptomatic limb only. CONCLUSIONS Neither abnormal shape nor movement of the arch are associated with chronic plantar fasciitis. However, arch mechanics may influence the severity of plantar fasciitis, once the condition is present. Digital flexion, in contrast, has a protective role in what might be a bilateral disease process.

Monitoring of the load regime applied on the osseointegrated fixation of a trans-femoral amputee: A tool for evidence-based practice

This study aimed to provide a description of the continuous recording of the true load regime experienced during daily living by the abutment of a trans-femoral amputee fitted with an osseointegrated fixation. The specific objectives: (i) To present an apparatus and a procedure allowing recording of the load regime, and (ii) an example of the raw data and six performance indicators of the usage of the prosthesis obtained with this method. A subject was monitored for a period of 5 hours as he went about his daily activities. The load regime was directly measured and recorded using a commercial transducer and data logger. The overall load profile presented alternative periods of variable length of inactivity (64%) and activity (36%), respectively. The maximum load applied on the mediolateral, anteroposterior and the long axes represented 21%, 21% and 120% of the body weight, respectively. The anteroposterior, mediolateral and long components of the impulse were 395 kN.s, 359 kN.s and 2,323 kN.s, respectively. The amputee generated a total of 2312 gait cycles of the prosthetic leg, giving an approximate overall cadence of 8 stride/min. Preliminary outcomes indicated that the proposed method was an improvement on the current techniques as it provided the true loading and actual usage of the prosthesis during daily living. This study is a stepping stone in the development of future affordable, on-board and user-friendly load recording systems that can be used in evidence-based practice.

Walking and running inter-limb asymmetry for Paralympic trans-femoral amputees, a biomechanical analysis:

The aim of this project was to further the research and understanding of the trans-femoral amputees ability to walk and run by comparing the changes in walking and running inter-limb asymmetry. An objective biomechanical analysis was conducted on four male trans-femoral amputees, all members of the Australian Paralympic training squad for the 1996 Atlanta Paralympic Games. The data was collected in the biomechanics laboratories at Queensland University of Technology and the Australian Institute of Sport. The main outcomes measure a synchronised 3D kinematic (200Hz), kinetic (600Hz) and temporal analysis of walking at self-selected (1.1-1.3m/s), and at maximal running speed (2.5-4.3m/s). The walking and running biomechanical data was summarised into 27 indices of symmetry. The results showed that for all subjects the inter-limb asymmetry was significantly different at running speed, when compared to the walking speed. Using indices of symmetry 79% of the kinematic, 67% of the kinetic, and 67% of the temporal measurements identified better inter-limb asymmetry when the subjects walked, compared to running. This study objectively identified that when Paralympic level amputees ran on their standard running prosthesis, the inter-limb asymmetry was exacerbated.

Bulk compressive properties of the heel fat pad during walking: A pilot investigation in plantar heel pain

BACKGROUND Altered mechanical properties of the heel pad have been implicated in the development of plantar heel pain. However, the in vivo properties of the heel pad during gait remain largely unexplored in this cohort. The aim of the current study was to characterise the bulk compressive properties of the heel pad in individuals with and without plantar heel pain while walking. METHODS The sagittal thickness and axial compressive strain of the heel pad were estimated in vivo from dynamic lateral foot radiographs acquired from nine subjects with unilateral plantar heel pain and an equivalent number of matched controls, while walking at their preferred speed. Compressive stress was derived from simultaneously acquired plantar pressure data. Principal viscoelastic parameters of the heel pad, including peak strain, secant modulus and energy dissipation (hysteresis), were estimated from subsequent stress-strain curves. FINDINGS There was no significant difference in loaded and unloaded heel pad thickness, peak stress, peak strain, or secant and tangent modulus in subjects with and without heel pain. However, the fat pad of symptomatic feet had a significantly lower energy dissipation ratio (0.55+/-0.17 vs. 0.69+/-0.08) when compared to asymptomatic feet (P<.05). INTERPRETATION Plantar heel pain is characterised by reduced energy dissipation ratio of the heel pad when measured in vivo and under physiologically relevant strain rates.

Achilles Tendinopathy Has an Aberrant Strain Response to Eccentric Exercise

PURPOSE Eccentric exercise has become the treatment of choice for Achilles tendinopathy. However, little is known about the acute response of tendons to eccentric exercise or the mechanisms underlying its clinical benefit. This research evaluated the sonographic characteristics and acute anteroposterior (AP) strain response of control (healthy), asymptomatic, and symptomatic Achilles tendons to eccentric exercise. METHODS Eleven male adults with unilateral midportion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Sagittal sonograms of the Achilles tendon were acquired immediately before and after completion of a common eccentric rehabilitation exercise protocol and again 24 h later. Tendon thickness, echogenicity, and AP strain were determined 40 mm proximal to the calcaneal insertion. RESULTS Compared with the control tendon, both the asymptomatic and symptomatic tendons were thicker (P < 0.05) and hypoechoic (P < 0.05) at baseline. All tendons decreased in thickness immediately after eccentric exercise (P < 0.05). The symptomatic tendon was characterized by a significantly lower AP strain response to eccentric exercise compared with both the asymptomatic and control tendons (P < 0.05). AP strains did not differ in the control and asymptomatic tendons. For all tendons, preexercise thickness was restored 24 h after exercise completion. CONCLUSIONS These observations support the concept that Achilles tendinopathy is a bilateral or systemic process and structural changes associated with symptomatic tendinopathy alter fluid movement within the tendon matrix. Altered fluid movement may disrupt remodeling and homeostatic processes and represents a plausible mechanism underlying the progression of tendinopathy.

Sagittal Plane Motion of the Human Arch During Gait: A Videofluoroscopic Analysis

Despite an abundance of literature investigating arch structure and musculoskeletal injury, there seems to be little consensus regarding the most appropriate technique of measuring dynamic arch motion. In this study, digitized videofluoroscopy was used to determine the sagittal plane motion of the medial longitudinal arch during dynamic gait. Nine female subjects requiring diagnostic foot radiographs underwent videofluoroscopy during a normal gait cycle. The calcaneal inclination angle, calcaneal-first metatarsal angle (CI-MT1) and height-to-length ratio of the arch, all reputed to measure arch alignment, were digitally analyzed from static radiographic images. Both the calcaneal inclination angle (0.96) and CI-MT1 (−0.98) angles were highly correlated with the criterion measure of height-to-length ratio. Repeated measures analysis of variance (ANOVA) identified a significant increase in the mean CI-MT1 angle during stance, suggesting a continual lowering and elongation of the arch. This study questions the validity of characterizing foot motion based on static measures of arch shape and recommends that further research be conducted to establish whether the observed trends reflect normal or pathological foot function.