A Laser-Guided Spinal Cord Displacement Injury in Adult Mice

Mouse models are unique for studying molecular mechanisms of neurotrauma because of the availability of various genetic modified mouse lines. For spinal cord injury (SCI) research, producing an accurate injury is essential, but it is challenging because of the small size of the mouse cord and the inconsistency of injury production. The Louisville Injury System Apparatus (LISA) impactor has been shown to produce precise contusive SCI in adult rats. Here, we examined whether the LISA impactor could be used to create accurate and graded contusive SCIs in mice. Adult C57BL/6 mice received a T10 laminectomy followed by 0.2, 0.5, and 0.8 mm displacement injuries, guided by a laser, from the dorsal surface of the spinal cord using the LISA impactor. Basso Mouse Scale (BMS), grid-walking, TreadScan, and Hargreaves analyses were performed for up to 6 weeks post-injury. All mice were euthanized at the 7th week, and the spinal cords were collected for histological analysis. Our results showed that the LISA impactor produced accurate and consistent contusive SCIs corresponding to mild, moderate, and severe injuries to the cord. The degree of injury severities could be readily determined by the BMS locomotor, grid-walking, and TreadScan gait assessments. The cutaneous hyperalgesia threshold was also significantly increased as the injury severity increased. The terminal lesion area and the spared white matter of the injury epicenter were strongly correlated with the injury severities. We conclude that the LISA device, guided by a laser, can produce reliable graded contusive SCIs in mice, resulting in severity-dependent behavioral and histopathological deficits

An Innovative Testing Protocol to Study Foot and Ankle Kinetics during Early Stance Phase of Gait

The objective of this study was to improve upon existing testing platform limitations with respect to foot and ankle mechanics in the sagittal plane during dorsiflexion and plantar flexion. The intent was to develop a multi-loading protocol that simulated aspects of early stance phase of walking gait. This data were used to evaluate the influence an Achilles load has on the kinematic profile of the ankle complex. Also, resulting kinematic profile data can be used to evaluate ligament/tendon effects, ankle arthroplasty, and various surgical techniques. A pair of cadaveric human feet, from the same donor, 50 years of age were dissected and potted for testing. A pure moment protocol was developed to determine the path of least resistance or lowest energy state to rotate the tibia about the ankle complex. This protocol utilized a 4-degree of freedom robot coupled with a two 6-axis load cells. Positional data was used to calculate the instantaneous axis of rotation (IAR) of the ankle complex. The data was then normalized with respect to the widest distance across the tibia. Results from this work include a repeatability study of the robotic testing platform (RTP), validation of protocol, calculation of the IAR, and a study of the effect an Achilles load has on ankle kinematics. The repeatability study used a modified version of the protocol to reduce setup effects. A repeatability analysis was conducted comparing repeated test runs for dorsiflexion and plantar flexion (one way repeated measures ANOVA with a Bonferroni test) and found no significant difference between the data sets for (P\u3c0.05). The IAR results with and without a passive Achilles load were significantly different (P\u3e0.05), using same statistical approach. Future work is to actively drive the Achilles load and add a push-off condition were the rotation is about the distal end of the first and second metatarsals. Along with that, the upper limit of the vGRF is to be increased to simulate the later part of the stance phase of gait where the Achilles load is larger

Body mass index and its effect on plantar pressure in overweight and obese adults

The proportion of overweight or obese adults is creating a growing problem throughout the world. Overweight and obesity have a significant influence on gait, and often cause difficulty. There is evidence to suggest that being overweight or obese places adults at a greater risk of developing foot complications such as osteoarthritis, tendonitis, plantar fasciitis, and foot ulcers. Increasingly, pressure ulcers have become a serious health problem. The purpose of this research is to investigate the effect of body weight on the feet, and to investigate the use of simulated body mass to study the effect of variable body mass on the foot plantar in adults aged 24 to 50 years of age while walking at a self-selected pace. A series of studies were undertaken to achieve the above purpose. The research involved: 1) assessing dynamic foot plantar pressure characteristics in adults who are normal weight, overweight or obese; 2) studying the gait impact of increased simulated body weight (SBW); and 3) evaluating the spatial relationship between the trace of the centroid of the area of contact with heel strike, midstance, and toe-off phases for the SBW groups. F-Scan in-shoe systems were utilised to gather the foot pressure data. The first study sought to investigate the effect of different body mass index (BMI) levels on plantar pressure distribution during walking, collection in fifteen voluntary participants were recruited. The BMI participants were divided into three groups (healthy, overweight and obese). The foot was divided into ten regions: heel (H), midfoot (MF), first metatarsal head (1MH), second metatarsal head (2MH), third metatarsal head (3MH), fourth metatarsal head (4MH), fifth metatarsal head (5MH), hallux (1stT), second toe (2ndT), and third to fifth toes (3rd-5thT). For each region, the following parameters were calculated: force (F), contact area (CA), contact pressure (CP), pressure time integral (PTI) and peak pressure (PP). The mean of the three repetitions of each subject was computed, and statistical procedures were performed with these mean ± standard deviation (SD) values. This study showed that the obese group had higher plantar pressure parameter values compared to the other two groups (overweight and healthy) for the ten different foot regions. The study observed significant changes in the parameters in the H and MHs (e.g. 2MH and 3MH) foot regions. The forefoot appears to be more sensitive to weight-related pressure under the foot than the rearfoot. Findings from this study indicate that being overweight or obese increases foot pressure measures, even for individuals with similar body features. Higher BMI values correlate with a higher load on the foot during walking in males. These findings have implications for pain and discomfort in the lower extremity in the obese while participating in activities of daily living such as walking. The second study investigated the effect of the research methodology involving the simulation of body weight (SBW) with additional weight, adding 10, 20, 30 kg to each participant’s body weight on plantar pressures. The sample comprised 31 adult males; each subject walked four times. The first walk was without any external weight (NBW, 0 kg), the second walk was with a weight of 10 kg, the third walk was with a weight of 20 kg and the last walk with a weight of 30 kg in the vest. The foot was divided into ten regions and for each region, the parameters were calculated the same way as the first study. At the end of this study it should be noted that SBW groups subjected to load have shown changes in foot plantar measure values compared to the NBW group. Most of the differences were found under H, MHs, 1stT and MF regions in the most clinically relevant parameters in SBW groups compared to the control group; the SBW groups showed higher values of plantar pressure. The results of the ICC showed a generally good to an excellent level of reliability, the quality of which was dependent on the regions of the foot and the variables investigated with SBW loads. This experiment pointed out that an insole pressure system is a reliable tool for evaluating foot plantar forces and pressures throughout the walk. The plantar pressure measures can be used in relative assessments, as the measures of repeatability are favourable for the measures and foot zones generally utilised in the study of people with clinical problems like neuropathic diabetics. In the final study, associations were investigated of the centroid (coordinates x-axis and y-axis) of the area of contact captured between normal (NBW) and simulated body weight (SBW) changes. The same 31 adult males who enrolled with the SBW tests were used to collect the centroid of the area of contact with the surface. This was located by calculating the geometric centre of a set of cloud points having the lowest z coordinate value. In this part, a foot pressure sensing insole was used to calculate the moment of heel strike, midstance and toe-off phases. Data were analysed descriptively (mean ± SD only). The outcome of this study, relating to specific individual characteristics of the centroid trace of the plantar contact area was compared with the heel strike, midstance, and toe-off phases for the SBW group with the NSBW group. X-axis and y-axis coordinates in the heel strike, midstance and toe-off phases under SBW with 30, 20, 10 kg had higher mean values compared to NSW. The x-axis and y-axis coordinates had mean values of 11.76, 9.68, and 7.76 mm; while the y-axis coordinates had mean values of 11.96, 9.89, and 8.18 mm. Moreover, x-axis and y-axis coordinates were assessed in the midstance phase under SBW with 30, 20, 10 kg with means of 6.59, 5.48, and 4.50 mm; while the y-axis coordinates had mean values of 6.38, 5.41, and 4.41 mm. In addition, x-axis and y-axis coordinates were assessed in the toe-off phase under SBW (30, 20, 10 kg) with mean values of 11.56, 9.67, and 7.97 mm; while the y-axis coordinates had mean values of 11.51, 9.39, 8.02 mm, respectively. X-axis and y-axis coordinates had mean values in relation to NBW in three phases: heel strike of 5.47 and 6.15; midstance of 2.99 and 3.05; and toe-off of 6.04 and 5.82, respectively. The x-locate and y-locate change can be calculate the change in rotation of the ankle joint. As the data was normalised according to the total time taken for the loading phase of the gait, the y-locational change was due partly to the extra weight, which could increase the time of lifting the foot. Therefore, the results showed that the x-locate and y-locate change can help to calculate the change in the rotation of the ankle joint. The project has shown that it is possible to demonstrate that obese people will, throughout their lives, adopt ways to effectively execute a particular activity. This finding provides a foundation for future clinical trials which could assist in preventing foot complications and could assist in the design of appropriate interventions to promote healthy outcomes for these adults. The simulated body weight resulted in a variation in plantar pressure distribution. Because the human foot adapts itself to any simulated condition, knowledge of the variation of pressure distributions of both feet can provide input for suitable guidelines for biomedical engineers. To promote the prevention of likely injury to the feet of overweight and obese people, the results of this study demonstrate the need to develop strategies which could include the building of an insole (orthosis) that absorbs foot plantar pressure

THE PEDIATRIC FLAT FOOT: PRE AND POST SURGICAL CORRECTION 3D KINEMATICS DATA

Introduction: aim of this study was to establish normality parameters and analyze 3D kinematic data before and after surgical correction of the pediatric flexible flat foot Materials and methods: study population was composed of 2 groups: 10 children (20 feet, 5M/5F)without any disorders of the foot were evaluated to obtain normal reference data; 20 children with bilateral flexible flatfoot candidate to bilateral surgical correction (40 feet, 13M/7F) The RFM -3D kinematics protocol was used. Clinical, radiographic and instrumental evaluation were performed preoperatively and at 12 months by the same surgeon An arthroereisis of the subtalar joint was performed by the same surgeon. Patients were divided in 3 groups:1:normality;2:before surgery;3: after surgery. For all the variables and for the three planes of the space comparison between groups were performed. Results: 3D rotational joint variables and planar angles were defined for normality, before and after sur-gery at the upright standing position. Differences were observed: hind foot , frontal plane; Chopart Joint ,transverse plane; Lisfanc Joint, frontal/transverse planes; ratio between 1rst and 2nd metatarsal, transverse plane; 2nd and 5th metatarsal versus ground respectively, sagittal plane; MLA, transverse plane Discussion/conclusions:: different variables, normalized after correction, suggest that surgery performed at the hind foot can also improves mid foot pronation, increases the medial longitudinal arch and im-proves ratio between metatarsal bones, allowing to quantify changes that clinical and radiological evaluation cannot provide. The pediatric foot is similar to the adults and pediatric flexible flat foot could be corrected surgically, even if painless

Comparison of lower body segment alignment of elite level hockey players to age-matched non-hockey players

Master's Project (M.A.) University of Alaska Fairbanks, 2015Lower body overuse and insidious onset injuries are thought to have an underlying biomechanical component which may be predisposing to injury. The purpose of this study was to compare lower body biomechanical characteristics for elite hockey players to matched controls. I hypothesize that elite hockey players have a greater degree of anterior pelvic tilt, greater varus knee angle, a higher foot arch and feet held in parallel more during gait than a matched non-skating population. Measures were taken of elite level, college aged, male hockey players and compared to cross country runners (ten subjects in each group) who served as controls for trunk angle, pelvic tilt angle, knee alignment, (varus/valgus angle), foot angle, arch index (arch height), hip, center of range of motion, hip external rotation, hip internal rotation, hip total range of motion (ROM), knee transverse plane ROM, and step width. The results obtained support the hypothesis for anterior pelvic tilt and foot angle during gait. Although knee angle was in the expected varus direction it was not significant and no differences were observed in the foot arch between the groups. All other measurements not directly related to the hypothesis were not significantly different with the exception of mean step width. The obtained results are important as recent literature describes a lower body posture of medial collapse into "dynamic valgus" as being predisposing to injury. Results show, on the spectrum from lower body varus to lower body valgus, hockey players are on the varus side of the spectrum in all attributes except arch height, which was similar in both populations. Since lower body alignment is thought to be coupled, this inconsistency appears contrary to the "medial collapse into dynamic valgus" model and may explain why foot orthotics and athletic shoes used as an injury intervention often fail

The Effects of a 12-Week Custom Foot Orthotic Intervention on the Intrinsic Muscles of the Foot, and Dynamic Stability During Unexpected Gait Termination in Healthy Young Adults

Introduction: Custom-made foot orthotics (CFO’s) are a commonly prescribed intervention to help individuals that are suffering from foot pain and foot disorders. However, the mechanisms of CFO’s are still poorly understood and are not well known. With the plantar intrinsic muscles of the foot being in direct contact with the CFO, it puts these structures at risk for disuse muscle atrophy as a result of being offloaded. Therefore, the purpose of the current study was to determine the effect of a 12-week custom-made foot orthotic intervention on the intrinsic muscles of the foot and dynamic stability during unexpected gait termination. Methods: Eighteen healthy young adults participated in the study. Participants were allocated by stratified sampling into either the: (a) orthotic group (n= 9) or (b) control group (n= 9). Beginning of each testing session, participants’ right foot was assessed by diagnostic ultrasound to measure the cross-sectional area (CSA) of the flexor digitorum brevis (FDB), abductor digiti minimi (Abd DM), and abductor hallucis (Abd H). Subsequently, participants completed an unexpected gait termination protocol and data was collected using force plates, motion capture, and electromyography (EMG) to assess dynamic stability. A total of 50 walking trials were completed at baseline, 6-weeks and 12-weeks, where 25% of the trials were unexpected gait termination. The variables used to measure dynamic stability were M/L COM-BOS and A/P COM-COP. Additionally, the amount of muscle activity was determined by average EMG magnitude and integrated EMG. The secondary outcome measures of interest were vertical force rate of loading (ROL), step width, step length and gait velocity. Results: At the end of the 12-week intervention, the participants in the OG had significantly smaller CSA of the FDB (9.6%) (p\u3c0.001), Abd DM (17.1%) (p\u3c0.001) and Abd H (17.4%) (p\u3c0.001) plantar intrinsic muscles. Despite muscle atrophy, individuals in the orthotic group showed an improvement of 1.1 cm in M/L COM-BOS (p\u3c0.001) at 12-weeks and were as stable as the CG during gait termination. Additionally, there were significant differences of ROL between the groups during first (p\u3c0.001) and second single stances (p\u3c0.001) at the end of 12-weeks. Lastly, there was no significant difference in average EMG magnitude of the intrinsic muscles between the groups. Discussion: The short-term use of CFO’s created a decrease in CSA of the FDB, Abd DM and Abd H plantar intrinsic muscles. These findings help understand the adaptations that are occurring when you offload specific structures such as the plantar intrinsic muscles. Although both groups were similar in creating stability when exposed to the mechanical perturbation, the participants in the OG adapted a compensatory strategy to recover their balance. Therefore, these findings along with future research can help develop guidelines to enhance the use of CFO’s by adding rehabilitative exercises to prevent disuse atrophy from occurring

Plantar Fasciitis: Biomechanics, Atrophy and Muscle Energetics

Purpose: The purpose of this dissertation was to determine the effects of chronic plantar fasciitis on intrinsic foot structures with respect to biomechanics, muscle atrophy and muscle energetics. This was accomplished in three parts. Methods: In Part I, a three-dimensional motion capture system with a synchronized force platform quantified multi-segment foot model kinematics and ground reaction forces associated with walking. Healthy individuals were compared to individuals with chronic plantar fasciitis feet. Typical kinematic variables, measures of coupling, phase and variability were examined in rearfoot, forefoot and hallux segments. In Part II, foot and leg magnetic resonance images were taken in subjects with unilateral plantar fasciitis so that within each subject, the healthy limb could be compared to the plantar fasciitis limb. Cross sectional areas (CSA) of the plantar intrinsic foot muscles (PIFM) and tibialis posterior muscle were computed from user-digitized images. In Part III, the metabolic demands of the PIFM were evaluated using phosphorous magnetic resonance spectroscopy at rest and after barefoot walking. Muscle pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) were compared in healthy and plantar fasciitis feet. Results: In comparison to healthy feet, plantar fasciitis feet exhibited significantly (p \u3c 0.05): 1) greater rearfoot motion, 2) greater sagittal plane forefoot motion, 3) fewer rearfoot-forefoot frontal anti-phase movements, 4) reduced rearfoot-forefoot transverse coordinative variability, 5) greater first metatarsophalangeal (FMPJ) joint dorsiflexion, 6) greater FMPJ-medial longitudinal arch (MLA) coupling variability, and 7) decreased vertical ground reaction forces at propulsion. Also, plantar fasciitis feet had 5.2% smaller PIFM CSA at the forefoot compared to contralateral healthy feet. No CSA differences were seen in the rearfoot PIFM or at the tibialis posterior muscle. The PIFM of healthy and PF feet were not significantly different in resting intracellular levels of pH or Pi/PCr, and there were no significant differences in the increase of Pi/PCr from rest to postwalking. Conclusions: In Part I, it was concluded that plantar fasciitis feet exhibit kinematics which are consistent with theoretical causation of the plantar fasciitis injury, that is, the plantar fasciitis foot exhibits excessive motion. Fewer number of anti-phase movements exhibited by plantar fasciitis feet may be an indication of pathology. The ground reaction force results suggested a compensatory pain response. In Part II, it was concluded that atrophy of the forefoot PIFM may destabilize the medial longitudinal arch and prolong the healing process. Lastly in Part III, it was concluded that resting energetics were consistent with muscle free of systemic disease or neuromuscular pathology. The presence of plantar fasciitis did not elicit systematic asymmetries in the metabolic response in comparison to healthy feet. Clinical Relevance: These kinematic results provided some evidence to support the clinical assertion that excessive motion is related to plantar fasciitis. These results also support treatment modalities which clinicians currently use to reduce rearfoot eversion, flattening of the medial longitudinal arch and dorsiflexion of the FMPJ (e.g. foot orthoses, insoles, taping, rocker soles). When treating plantar fasciitis patients, clinicians should assess for PIFM and tibialis posterior muscle atrophy and prescribe targeted exercises when appropriate