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Safe transportation for wheelchair users who do not transfer to the vehicle seat when traveling in motor vehicles requires after-market wheelchair tiedown and occupant restraint systems (WTORS) to secure the wheelchair and provide crashworthy restraint for the wheelchair-seated occupant. In the absence of adequate government safety standards, voluntary standards for the design and performance of WTORS, and for wheelchairs used as seats in motor vehicles, have been developed. The initial versions of these standards qualify equipment for use in all types and sizes of motor vehicles using a 30-mph (48-kph), 20-g frontal sled-impact test. The wheelchair standard requires four accessible, crash-tested securement points on wheelchairs so they can be more easily and effectively secured using a four-point strap-type tie-down system. Future voluntary standards are aimed at reducing injury risk for wheelchair-seated occupants in rear impacts and at providing a method for evaluating the crashworthiness of wheelchair seating systems independent of wheelchair baseframes. They also address improved usability and independence for wheelchair-seated travelers using public transportation by specifying universal docking interface geometry for wheelchairs and design and performance requirements for rear-facing wheelchair passenger stations for use in the very low-g environments of large fixed-route transit buses. [ABSTRACT FROM AUTHOR]

We compared differences in isometric strength between older adults who have undergone elective unilateral total hip arthroplasty (THA) and completed rehabilitation with a population of community-dwelling older adults who have not had THA. The study was a cross-sectional design, and 22 unilateral THA subjects and 38 community-dwelling older adults participated. THA subjects received on average 13 outpatient or home-based physical therapy sessions before evaluation. THA subjects were evaluated 4 to 5 months postsurgery. We assessed isometric muscle strength by measuring peak hip torque per body weight with a robotic dynamometer during abduction, flexion, and extension. No significant performance differences were observed between operated and nonoperated hips of THA subjects. THA subject operated and nonoperated hips generated significantly less peak torque per body weight during flexion (p = 0.03) compared with community-dwelling older adult hips (THA subject operated hips = 6.96 ft-lb/lb, THA subject nonoperated hips = 8.26 ft-lb/lb, community-dwelling older adult hips = 11.56 ft-lb/lb). No significant differences were observed between THA subjects and community- dwelling older adults during hip extension (p = 0.55) or abduction (p = 0.17). At 4 to 5 months postsurgery, THA subjects were not at the same level of biomechanical performance as community-dwelling older adults. Significant strength deficits were found in THA subject operated versus nonoperated hips during isometric flexion. Additional or modified physical therapy that targets the hip flexors is recommended after THA. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate differences in isokinetic hip flexion, extension, and abduction muscle performance of operated vs. nonoperated hips in older adults who have undergone elective, unilateral, total hip replacement (THR) surgery and completed rehabilitation. DESIGN: Quasi-experimental study using a nonequivalent posttest-only control group design, comprising 20 unilateral THR patients and a convenience sample of 22 healthy older adults. THR patients participated between 4 and 5 mos after surgery. THR subjects received an average of 13 outpatient or home-based physical therapy sessions. Isokinetic muscle strength and fatigue was assessed through measurement of hip peak torque per body weight, total work, and average power using a robotic dynamometer. RESULTS: Comparisons of THR subjects' operated vs. nonoperated hips showed no significant differences in isokinetic performance for any of the examined variables. THR subjects' operated hips generated significantly less peak torque per body weight, total work, and average power across all exercises as compared with a population of healthy subjects. CONCLUSIONS: THR subjects' operated and nonoperated hips showed similar biomechanical performance. THR patients are not being restored to the same level of strength and muscular endurance as compared with a population of healthy adults. These findings may be useful in providing a preliminary rationale for revising current approaches in THR rehabilitation protocols. [ABSTRACT FROM AUTHOR]

Individuals using wheeled mobility devices (WMDs) often use them as motor vehicle seats during transportation. Wheelchair occupant restraint systems (WORSs), consisting of upper torso and pelvic restraints, are usually mounted to the structure of transit vehicles to secure individuals within their wheelchair seats. This preliminary study attempts to evaluate the use and satisfaction of currently installed vehicle-mounted WORSs for individuals using WMD as seats in motor vehicles. A survey was conducted among 33 adults who use their WMD to travel in motor vehicles. Results from the survey showed that upper torso and pelvic restraints installed in private vehicles are quick, comfortable, and easy to use. However, WORS installed in mass transit and paratransit are often uncomfortable to wear, difficult to reach, and time-consuming to use. This preliminary study documents the growing need for developing alternative WORS that are safe, comfortable, and that allow independent usage for wheelchair occupants while traveling in a motor vehicle. [ABSTRACT FROM AUTHOR]

Obtaining proper occupant restraint fit when using a wheelchair as a motor vehicle seat is often difficult to attain with vehicle-mounted restraint systems. The comprehensive evaluation conducted in this study illustrates the occupant crash protection benefits of wheelchair-integrated restraint systems, as compared to vehicle-mounted restraint systems. Using computer crash simulation, occupant kinematic and biomechanical measures associated with a 20g/30mph frontal impact were evaluated and compared to injury criteria and SAE J2249 WTORS kinematic limits. These measures were also used to compile a Motion Criteria (MC) index and Combined Injury Criteria (CIC) index for each evaluated restraint scenario. These indices provide a composite method for comparing various crash scenarios. With the exception of an unsafe 36-inch height off-shoulder shoulder belt anchor scenario, the MC index was minimized for the integrated restraint scenario. Similarly, the CIC index was also minimized for the wheelchair-integrated restraint scenario. This preliminary study emphasizes the need for transfer of integrated restraint technology to the wheelchair transportation industry. [ABSTRACT FROM AUTHOR]

When designing wheelchairs for use as motor vehicle seats, special design criteria must be followed to assure the crash safety of the wheelchair user. Failure of seating system components under crash loading conditions could lead to serious injury or fatality. In this study, seat and seat-back loading in a frontal crash are explored using computer simulation techniques. A previously validated simulation model consisting of a powerbase wheelchair and a seated 50th-percentile male test dummy subjected to a 20g/30mph frontal impact were used for the study. Since such a wide range of seating systems are available, parametric analyses were conducted to evaluate the influence of surface stiffness and seat-back angle on wheelchair seat and back loading. Seat loading varied with stiffness, ranging from 819-3,273 lb., while seat-back loading was found to be between 1,427-2,691 lb., depending upon back stiffness and recline angle. [ABSTRACT FROM AUTHOR]

Wheelchair designs based upon loads applied quasi-statically during normal mobility use are likely inadequate to handle the increased level of dynamic crash forces that may be encountered when using the wheelchair as a motor vehicle seat. The purpose of this study was to characterize the integrity of wheelchair caster assemblies under simulated crash conditions. This study utilized dynamic drop (DD) testing, with loading levels and rates adjusted to match those found previously in sled impact testing and computer crash simulations. The results verify that current caster assembly designs may not be able to withstand forces associated with a crash. Five of seven evaluated caster assemblies failed when loaded to 8,007 N, or less, at loading rates seen in sled testing. DD testing used in this study is a valuable tool that can be used in the design of transport wheelchair components. [ABSTRACT FROM AUTHOR]

Background: Kinematic and kinetic analysis have been used to gain an understanding of canine movement and joint loading during gait. By non-invasively predicting muscle activation patterns and forces during gait, musculoskeletal models can further our understanding of normal variability and muscle activation patterns and force profiles characteristic of gait., Methods: Pelvic limb kinematics and kinetics were measured for a 2 year old healthy female Dachshund (5.4 kg) during gait using 3-D motion capture and force platforms. A computed tomography scan was conducted to acquire pelvis and pelvic limb morphology. Using the OpenSim modeling platform, a bilateral pelvic limb subject-specific rigid body musculoskeletal computer model was developed. This model predicted muscle activation patterns, muscle forces, and angular kinematics and joint moments during walking., Results: Gait kinematics determined from motion capture matched those predicted by the model, verifying model accuracy. Primary muscles involved in generating joint moments during stance and swing were predicted by the model: at mid-stance the adductor magnus et brevis (peak activation 53.2%, peak force 64.7 N) extended the hip, and stifle flexor muscles (biceps femoris tibial and calcaneal portions) flexed the stifle. Countering vertical ground reaction forces, the iliopsoas (peak activation 37.9%, peak force 68.7 N) stabilized the hip in mid-stance, while the biceps femoris patellar portion stabilized the stifle in mid-stance and the plantar flexors (gastrocnemius and flexor digitorum muscles) stabilized the tarsal joint during early stance. Transitioning to swing, the iliopsoas, rectus femoris and tensor fascia lata flexed the hip, while in late swing the adductor magnus et brevis impeded further flexion as biceps femoris tibial and calcaneal portions stabilized the stifle for ground contact., Conclusion: The musculoskeletal computer model accurately replicated experimental canine angular kinematics associated with gait and was used to predict muscle activation patterns and forces. Thus, musculoskeletal modeling allows for quantification of measures such as muscle forces that are difficult or impossible to measure in vivo ., (Copyright © 2020 Brown, Bertocci, States, Levine, Levine and Howland.)

Background: Kinematic gait analysis is an important noninvasive technique used for quantitative evaluation and description of locomotion and other movements in healthy and injured populations. Three dimensional (3D) kinematic analysis offers additional outcome measures including internal-external rotation not characterized using sagittal plane (2D) analysis techniques., Methods: The objectives of this study were to 1) develop and evaluate a 3D hind limb multiplane kinematic model for gait analysis in cats using joint coordinate systems, 2) implement and compare two 3D stifle (knee) prediction techniques, and 3) compare flexion-extension determined using the multiplane model to a sagittal plane model. Walking gait was recorded in 3 female adult cats (age = 2.9 years, weight = 3.5 ± 0.2 kg). Kinematic outcomes included flexion-extension, internal-external rotation, and abduction-adduction of the hip, stifle, and tarsal (ankle) joints., Results: Each multiplane stifle prediction technique yielded similar findings. Joint angles determined using markers placed on skin above bony landmarks in vivo were similar to joint angles determined using a feline hind limb skeleton in which markers were placed directly on landmarks ex vivo. Differences in hip, stifle, and tarsal joint flexion-extension were demonstrated when comparing the multiplane model to the sagittal plane model., Conclusions: This multiplane cat kinematic model can predict joint rotational kinematics as a tool that can quantify frontal, transverse, and sagittal plane motion. This model has multiple advantages given its ability to characterize joint internal-external rotation and abduction-adduction. A further, important benefit is greater accuracy in representing joint flexion-extension movements., Competing Interests: The authors have declared that no competing interests exist.

The objective of this study was to describe the patient population of dogs with cranial cruciate ligament (CrCL) deficiency that were prescribed a stifle orthosis. A total of 215 client-owned dogs with previously diagnosed CrCL deficiency were prescribed a stifle orthosis at a veterinary pain management and mobility clinic. Patient intake data collected included dog signalment, chief medical complaint, home environment and activity description, medical and surgical history, and diagnosing veterinarian. An orthopedic examination was conducted to assess pelvic limb function and determine pelvic limb morphologic measures. Spayed females (57.2%) were most common in our sample. Median age, body weight, and body condition score were 9.00 ± 3.23 years, 32.98 ± 13.37kg, and 6.00 ± 1.04, respectively. Most common breeds prescribed stifle orthoses included Labrador Retriever, Golden Retriever, and German Shepherd. Right and left limbs were equally affected, and 19.5% of dogs previously had stifle stabilization surgery. Primary reasons for seeking a stifle orthosis consultation were surgical concerns, advanced age, and surgery cost. Most common chief complaints included altered gait, decreased weight bearing, and pain following activity. Reduced stifle extension, increased cranial drawer score, and decreased 3-leg stance time characterized the CrCL-deficient stifle. Stifle orthosis represents an alternative approach to surgical stabilization and management of CrCL deficiency. CrCL-deficient dogs prescribed stifle orthoses were generally large breeds of advanced age with above ideal body condition score. Owners commonly sought a stifle orthosis for CrCL deficiency due to reservations regarding surgical management., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Objective: To evaluate lateral fabellotibial suture (LFTS) and TightRope CCL (TR) extra-articular stabilization biomechanics in the cranial cruciate ligament (CrCL)-deficient canine stifle joint during the stance phase of gait., Study Design: Computer simulations., Animals: Healthy 33-kg Golden Retriever., Methods: LFTS and TR were implemented in a previously developed 3-D quasi-static rigid body CrCL-deficient canine pelvic limb computer model simulating the stance phase of gait. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared across the CrCL-intact, CrCL-deficient, and extra-articular stabilized stifle joints., Results: Compared to the CrCL-intact stifle, peak caudal cruciate and lateral collateral ligament (LCL) loads were increased in the LFTS-managed stifle, peak caudal cruciate and LCL loads were decreased in the TR-managed stifle, and peak medial collateral and patellar ligament (PL) loads were similar for both techniques. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral, and medial collateral ligament loads decreased, and peak PL load was similar in the LFTS- and TR-managed stifle joints. Peak relative tibial translation decreased, and peak relative tibial rotation changed from internal rotation to external rotation in the LFTS- and TR-managed stifle joints compared to the CrCL-deficient stifle., Conclusion: Our computer model predicted controlled tibial translation, decreased cruciate and collateral ligament loads, and a change in femorotibial rotation from internal to external with LFTS and TR stifle management as compared to the CrCL-deficient stifle. This study demonstrates how computer modeling can be used to evaluate biomechanics of stifle stabilization surgical techniques., (© 2017 The American College of Veterinary Surgeons.)

OBJECTIVE To evaluate effects of an orthosis on biomechanics of a cranial cruciate ligament (CrCL)-deficient canine stifle joint by use of a 3-D quasistatic rigid-body pelvic limb computer model simulating the stance phase of gait and to investigate influences of orthosis hinge stiffness (durometer). SAMPLE A previously developed computer simulation model for a healthy 33-kg 5-year-old neutered Golden Retriever. PROCEDURES A custom stifle joint orthosis was implemented in the CrCL-deficient pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation in the orthosis-stabilized stifle joint (baseline scenario; high-durometer hinge]) were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints. Sensitivity analysis was conducted to evaluate the influence of orthosis hinge stiffness on model outcome measures. RESULTS The orthosis decreased loads placed on the caudal cruciate and lateral collateral ligaments and increased load placed on the medial collateral ligament, compared with loads for the CrCL-intact stifle joint. Ligament loads were decreased in the orthosis-managed CrCL-deficient stifle joint, compared with loads for the CrCL-deficient stifle joint. Relative tibial translation and rotation decreased but were not eliminated after orthosis management. Increased orthosis hinge stiffness reduced tibial translation and rotation, whereas decreased hinge stiffness increased internal tibial rotation, compared with values for the baseline scenario. CONCLUSIONS AND CLINICAL RELEVANCE Stifle joint biomechanics were improved following orthosis implementation, compared with biomechanics of the CrCL-deficient stifle joint. Orthosis hinge stiffness influenced stifle joint biomechanics. An orthosis may be a viable option to stabilize a CrCL-deficient canine stifle joint.

Objective: To evaluate the influence of the Simitri Stable in Stride™ extracapsular articulating implant (EAI) on canine stifle biomechanics in the cranial cruciate ligament (CrCL)-deficient stifle using a 3-dimensional (3D) quasi-static rigid body canine pelvic limb computer model simulating the stance phase of gait., Study Design: Computer simulations., Animals: Five-year-old neutered male golden retriever (33 kg)., Methods: The EAI was implemented in a previously developed 3D CrCL-deficient canine pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared to the CrCL-intact and CrCL-deficient stifle., Results: The EAI significantly increased peak caudal cruciate and medial collateral ligament loads, significantly changed when peak lateral collateral ligament load occurred, and did not significantly affect peak patellar ligament load compared to the CrCL-intact stifle. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral, and medial collateral ligament loads significantly decreased in the EAI-managed stifle. Despite decreased peak caudal cruciate ligament loading, the EAI-managed stifle generated local maxima that exceeded those of the CrCL-deficient stifle at various intervals of stance. Peak relative tibial translation and rotation significantly decreased in the EAI-managed stifle compared to the CrCL-deficient stifle., Conclusion: Model-predicted stifle biomechanics differed after EAI system application in the CrCL-deficient stifle, but were not restored to that of the CrCL-intact stifle., (© Copyright 2016 by The American College of Veterinary Surgeons.)

OBJECTIVE To investigate the influence of 4 biomechanical parameters on canine cranial cruciate ligament (CrCL)-intact and -deficient stifle joints. SAMPLE Data for computer simulations of a healthy 5-year-old 33-kg neutered male Golden Retriever in a previously developed 3-D rigid body pelvic limb computer model simulating the stance phase during walking. PROCEDURES Canine stifle joint biomechanics were assessed when biomechanical parameters (CrCL stiffness, CrCL prestrain, body weight, and stifle joint friction coefficient) were altered in the pelvic limb computer simulation model. Parameters were incrementally altered from baseline values to determine the influence on stifle joint outcome measures (ligament loads, relative tibial translation, and relative tibial rotation). Stifle joint outcome measures were compared between CrCL-intact and -deficient stifle joints for the range of parameters evaluated. RESULTS In the CrCL-intact stifle joint, ligament loads were most sensitive to CrCL prestrain. In the CrCL-deficient stifle joint, ligament loads were most sensitive to body weight. Relative tibial translation was most sensitive to body weight, whereas relative tibial rotation was most sensitive to CrCL prestrain. CONCLUSIONS AND CLINICAL RELEVANCE In this study, computer model sensitivity analyses predicted that CrCL prestrain and body weight influenced stifle joint biomechanics. Cranial cruciate ligament laxity may influence the likelihood of CrCL deficiency. Body weight could play an important role in management of dogs with a CrCL-deficient stifle joint.

Objective: To evaluate the effects of tibial tuberosity advancement (TTA) on canine biomechanics in the cranial cruciate ligament (CrCL)-deficient stifle using a 3-dimensional quasi-static rigid body pelvic limb computer model simulating the stance phase of gait., Study Design: Computer simulations., Animals: A 5-year-old neutered male Golden Retriever weighing 33 kg., Methods: A TTA was implemented in a previously developed canine pelvic limb computer model using the tibial plateau slope and common tangent planning techniques. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared to CrCL-intact and CrCL-deficient stifles., Results: The TTA significantly decreased peak caudal cruciate ligament load, significantly increased peak lateral collateral ligament load, and significantly changed peak medial collateral ligament load occurrence, while there was no significant difference in peak patellar ligament load compared to the CrCL-intact stifle. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral and medial collateral ligament loads significantly decreased, while peak patellar ligament load was similar, peak relative tibial translation significantly decreased and peak relative tibial rotation was converted to external rotation in the TTA-treated stifle. Each TTA planning technique generated similar caudal cruciate, medial collateral, and patellar ligament loading as well as relative tibial translation, but lateral collateral ligament loading and occurrence of relative tibial rotation differed significantly across the techniques., Conclusions: Model-predicted stifle ligament loads improved following TTA compared to the CrCL-deficient stifle, but TTA did not restore CrCL-intact stifle biomechanics. The TTA effectively reduced tibial translation, but tibial rotation was not stabilized., (© Copyright 2015 by The American College of Veterinary Surgeons.)

Objective: To evaluate effects of tibial plateau leveling osteotomy (TPLO) on canine stifle joint biomechanics in a cranial cruciate ligament (CrCL)-deficient stifle joint by use of a 3-D computer model simulating the stance phase of gait and to compare biomechanics in TPLO-managed, CrCL-intact, and CrCL-deficient stifle joints., Sample: Computer simulations of the pelvic limb of a Golden Retriever., Procedures: A previously developed computer model of the canine pelvic limb was used to simulate TPLO stabilization to achieve a tibial plateau angle (TPA) of 5° (baseline value) in a CrCL-deficient stifle joint. Sensitivity analysis was conducted for tibial fragment rotation of 13° to -3°. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints., Results: TPLO with a 5° TPA converted cranial tibial translation to caudal tibial translation and increased loads placed on the remaining stifle joint ligaments, compared with results for a CrCL-intact stifle joint. Lateral collateral ligament load was similar, medial collateral ligament load increased, and caudal cruciate ligament load decreased after TPLO, compared with loads for a CrCL-deficient stifle joint. Relative tibial rotation after TPLO was similar to that of a CrCL-deficient stifle joint. Stifle joint biomechanics were affected by TPLO fragment rotation., Conclusions and Clinical Relevance: In the model, stifle joint biomechanics were partially improved after TPLO, compared with CrCL-deficient stifle joint biomechanics, but TPLO did not fully restore CrCL-intact stifle joint biomechanics. Overrotation of the tibial fragment negatively influenced stifle joint biomechanics by increasing caudal tibial translation.

Objective: To investigate the influence of varying morphological parameters on canine stifle joint biomechanics by use of a 3-D rigid-body canine pelvic limb computer model that simulated an intact and cranial cruciate ligament (CrCL)-deficient stifle joint across the stance phase of gait at a walk., Sample: Data from computer simulations., Procedures: Computer model morphological parameters, including patellar ligament insertion location, tibial plateau angle (TPA), and femoral condyle diameter (FCD), were incrementally altered to determine their influence on outcome measures (ligament loads, relative tibial translation, and relative tibial rotation) during simulation of the stance phase of gait at a walk. Outcome measures were assessed for each scenario and compared between an intact and CrCL-deficient stifle joint with the sensitivity index (the percentage change in outcome measure divided by the percentage change in input parameter)., Results: In a CrCL-intact stifle joint, ligament loads were most sensitive to TPA. In a CrCL-deficient stifle joint, outcome measures were most sensitive to TPA with the exception of caudal cruciate ligament and lateral collateral ligament loads, which were sensitive to FCD and TPA. Relative tibial translation was sensitive to TPA and patellar ligament insertion location, whereas relative tibial rotation was most sensitive to TPA., Conclusions and Clinical Relevance: The computer model sensitivity analyses predicted that individual parameters, particularly TPA and FCD, influence stifle joint biomechanics. Therefore, tibial and femoral morphological parameters may affect the likelihood, prevention, and management of CrCL deficiency.

Falls from beds and other household furniture are common scenarios stated to conceal child abuse. Knowledge of the biomechanics associated with short-distance falls may aid clinicians in distinguishing between abusive and accidental injuries. Computer simulation is a useful tool to investigate injury-producing events and to study the effect of altering event parameters on injury risk. In this study, a paediatric bed fall computer simulation model was developed and validated. The simulation was created using Mathematical Dynamic Modeling(®) software with a child restraint air bag interaction (CRABI) 12-month-old anthropomorphic test device (ATD) representing the fall victim. The model was validated using data from physical fall experiments of the same scenario with an instrumented CRABI ATD. Validation was conducted using both observational and statistical comparisons. Future parametric sensitivity studies using this model will lead to an improved understanding of relationships between child (fall victim) parameters, fall environment parameters and injury potential.

Safe transportation for wheelchair users who do not transfer to the vehicle seat when traveling in motor vehicles requires after-market wheelchair tiedown and occupant restraint systems (WTORS) to secure the wheelchair and provide crashworthy restraint for the wheelchair-seated occupant. In the absence of adequate government safety standards, voluntary standards for the design and performance of WTORS, and for wheelchairs used as seats in motor vehicles, have been developed. The initial versions of these standards qualify equipment for use in all types and sizes of motor vehicles using a 30-mph (48-kph), 20-g frontal sled-impact test. The wheelchair standard requires four accessible, crash-tested securement points on wheelchairs so they can be more easily and effectively secured using a four-point strap-type tie-down system. Future voluntary standards are aimed at reducing injury risk for wheelchair-seated occupants in rear impacts and at providing a method for evaluating the crashworthiness of wheelchair seating systems independent of wheelchair base-frames. They also address improved usability and independence for wheelchair-seated travelers using public transportation by specifying universal docking interface geometry for wheelchairs and design and performance requirements for rear-facing wheelchair passenger stations for use in the very low-g environments of large fixed-route transit buses.

Comparative risks or benefits to wheelchair-seated pediatric occupants in motor vehicles associated with wheelchair headrest use during rear impact were evaluated using pediatric head and neck injury outcome measures. A Hybrid III 6-year-old anthropomorphic test device (ATD), seated in identical WC19-compliant pediatric manual wheelchairs, was used to measure head and neck response during a 25 km/h (16 mph), 11 g rear impact. ATD responses were evaluated across two test scenarios: three sled tests conducted without headrests, and three with slightly modified commercial headrests. Head and neck injury outcomes measures included: linear head acceleration, head injury criteria (HIC) values, neck injury criteria (N(ij)) values, and combined rotational head velocity and acceleration. Neck and head injury outcome measures improved by 34-70% in sled tests conducted with headrests compared to tests without headrests. Headrest use reduced N(ij) values and the likelihood of concussion from values above established injury thresholds to values below injury thresholds. Injury measure outcome reductions suggest lower head and neck injury risks for wheelchair-seated children using wheelchair-mounted headrests as compared to non-headrest users in rear impact. Use of relative comparisons across two test scenarios served to minimize effects of ATD biofidelity limitations.

The Americans with Disabilities Act requires that transit providers accommodate passengers who use "common wheelchairs" when traveling in a motor vehicle. Wheelchair tiedown and occupant restraint systems are commonly used to secure wheelchairs and restrain occupants in fixed-route and demand route transit vehicles. Throughout the 17 years since the Americans with Disabilities Act has been in effect, transit providers have complained about the usability of wheelchair tiedown and occupant restraint systems, and improper securement has been linked to injuries among wheelchair users during "nonimpact incidents." This research study explored the use of wheelchair tiedown and occupant restraint systems in actual practice and the potential risks of misuse to wheelchair-seated individuals. The qualitative research conducted in this study revealed that improper wheelchair securement (i.e. using less than four tiedown straps) can be fairly common practice in fixed-route transit. In addition, preliminary computer simulations show that improper wheelchair securement in emergency driving conditions may place wheelchair occupants at a greater risk of injury. It should be noted, however, that this is a pilot study and has its limitations. For example, qualitative data were gathered from one metropolitan area transit provider across a limited range of vehicle and wheelchair types. Additionally, the computer simulation model used in this study was originally validated for impact situations.

A total of 283 wheelchair-seated bus riders responded to a 35-item Web-based survey investigating their experiences on public, fixed-route buses. The survey addressed the use of wheelchair tiedowns and occupant restraint systems (WTORS), the attitudes and behaviors of wheelchair users toward the use of this equipment, and the transit experience. Results indicate that consistent use of four-point tiedown and occupant restraint systems is fairly low. Only 33.2% of the participants reported always securing their wheelchair, and 62.2% reported using occupant restraints consistently. A preference for fixed-route over para-transit was related to larger city size. Implementation of transit agency policy regarding WTORS was found to be inconsistent. Easier-to-use WTORS and improved operator training in larger transit agencies would likely increase the correct use of safety equipment and improve wheelchair users' bus-riding experiences.

Background: Stair falls are common among young children and are also common false histories in cases of child abuse. When a child presents with a femur fracture and a stair-fall history, a judgment of plausibility must be made. A lack of objective injury and biomechanical data makes plausibility determination more difficult. Our objective was to characterize key features associated with femur fractures from reported stair falls, to develop a model for assessing injury plausibility (IP)., Methods: Children 2 to 36 months of age who presented with a femur fracture from a reported stair fall were studied prospectively. Detailed history recording, examinations, fracture characterization, and injury scene analyses were conducted, and biomechanical measures associated with injury prediction were calculated. With our proposed IP model, all cases were then scored for the detail of history, biomechanical compatibility of fracture morphologic features, time to seeking care, and presence of other injuries., Results: Twenty-nine children were diagnosed with a femur fracture resulting from a reported stair fall. The IP model made a clear distinction between 2 groups, designated plausible and suspicious. Significant differences were observed for the detail of history, biomechanical compatibility of fracture, time to seeking care, presence of other injuries, and total IP scores. In the plausible group, the minimal linear momentum associated with a transverse fracture was almost 10-fold greater than that for spiral or buckle fracture types., Conclusions: This study adds new information to the current body of knowledge regarding injury biomechanics and fractures among children. The IP model provides an objective means of assessing plausibility of reported stair-fall-related femur fractures and identifies key characteristics to facilitate decision-making.

This study investigates the usability of wheelchair occupant restraint systems (WORS) that are used for crash protection of individuals seated in wheelchairs during motor vehicle transit. Ten independent adults with significant functional limitations who use wheelchairs for primary mobility were observed and interviewed while performing reach and manipulation tasks associated with WORS usage. Participants' opinions on ease of use and comfort-related factors were obtained for four occupant restraint scenarios. The study results show evidence of user problems with common WORS designs for use by wheelchair-seated individuals with significant functional limitations. Results from this pilot study suggest redesign of latch plates and buckles used in WORS to enable wheelchair-seated individuals with functional limitations to don and buckle belt restraints more easily and independently. Additionally, this study provides guidance to occupant-restraint manufacturers and wheelchair designers regarding belt-restraint usability. Improved WORS usability will complement other efforts to increase frequency of safety belt usage and lead to improved occupant safety.

Objective: The objectives of our study were to assess biomechanics associated with feet-first free falls in 3-year-old children and to investigate the influence of impact surface type and fall height on key biomechanical measures associated with injury risk., Methods: Repeatable feet-first free fall experiments were conducted in a laboratory mock-up environment using an instrumented Hybrid II 3-year-old test dummy. Impact surface type and fall height were varied to examine their influence on biomechanical measures., Results: Feet-first falls from short distances (27 in.) (0.69 m) were found to have a low risk of contact-type head injury, regardless of impact surface type. When comparing different types of impact surfaces in a 27 in. (0.69 m) fall, head acceleration associated with falls onto playground foam was significantly less than that associated with falls onto wood, linoleum or padded carpet. For falls onto playground foam, femoral compressive loads and bending moments were found to significantly increase as fall height increased., Conclusions: Impact surface type and fall height were found to influence biomechanics associated with injury risk in feet-first free falls as assessed through experimental mock-ups using an instrumented child test dummy. Feet-first falls from short distances (27 in.) (0.69 m) were associated with a low risk of contact-type head injury as assessed using HIC, irrespective of impact surface type.

Many wheelchair users are required or choose to use their wheelchairs as a motor vehicle seat during transport. It is therefore key that the wheelchair components be designed to tolerate crash-level loading conditions. Casters are particularly prone to failure under crash loading conditions. Our study evaluated wheelchair caster loading during 20g/48 kph frontal sled impact testing using an 85-kg surrogate wheelchair base (SWCB) with casters positioned on a load-measuring platform. A Hybrid III 50th percentile male test dummy was seated in the SWCB, which simulated a power wheelchair and was secured using four-point tiedowns. Various rear securement point heights and wheelchair seating systems were used to study their effect on caster loading. Caster normal loading was found to vary from 769 to 7,209 N depending on rear securement location and integrity of the seating system. Dynamic sled impact test results showed that normal loading of the front wheelchair casters was influenced by wheelchair seating system integrity and rear wheelchair securement height. Shear loading varied from 781 to 1,589 N and did not appear to be dependent on seat integrity or rear securement height. The load/time histories measured during dynamic impact testing can be used to guide the development of transit-safe caster design.

Background: Short-distance falls, such as from a bed, are often falsely reported scenarios in child abuse. In attempting to differentiate between abusive and nonabusive injury, knowledge of factors that affect injury risk in falls could prove useful., Objectives: To assess the biomechanics associated with simulated short-distance falls in children (one fall scenario, without attempting to maximize injury potential) and to investigate the effect of impact surface type on injury risk., Methods: Repeatable fall experiments from bed height (0.68 m) onto different surfaces were conducted using an instrumented side-lying Hybrid II 3-year-old test dummy. Biomechanical measures assessed in falls included head acceleration, pelvis acceleration, femur loading, and head injury criteria., Results: Fall dynamics resulted in the pelvis or legs making first contact. Biomechanical measures assessed in simulated bed falls were below known head injury criteria and lower extremity injury thresholds. The impact surface type had a significant effect on head injury risk and lower extremity loading. Playground foam proved to have the lowest associated injury risk of all the tested surfaces., Conclusions: The biomechanics of a child falling from a short distance, such as from a bed, were investigated using an experimental laboratory mock-up and an instrumented test dummy. Despite the impact surface having an effect on injury risk, rolling from a 0.68-m (27-in) horizontal surface from a side-lying posture presented low risk of contact-type head injury and leg injury on all tested impact surfaces.

Much of what is understood as potential for injury is based in what has been observed clinically. This knowledge base is critical for decision making but has inherent and important limitations. Experimental studies investigating the influence of environmental factors, such as height of fall and surface type on injury potential, add important information, but also have inherent limitations. Important trends and predictions of probable injury can be studied but inference to a specific child's injuries is difficult because of unaccounted for contributing factors of injury risk. Such factors include muscle contraction, protective reflexes, and specific tissue response to trauma forces. Additional biomechanical research is needed to bridge the gap between clinical observations and experimental predictions. The specific and unique perspective of the neurosurgeon is a critical piece in differentiating accidental and nonaccidental head injury with experience and reason as the basis of the conclusion. Do the physics of the injury match the mechanistic principals of the described injury event? Could all of the injuries result from the event? Is it plausible that these set of injuries occurred from the described event based on the [table: see text] physician's experience and the current scientific understanding of injury biomechanics? Do the mechanical forces of the reported mechanism and injuries match? To determine that an explanation is plausible requires consideration of all the facts and injuries, consideration of the described behavior, and consistency with the neurologic status. These facts of the case are compared with medical knowledge and the learned experience of the neurosurgeon. The answer to the question "is it possible?" is based on clinical experience and objective reasoning. Rather than a black box question and answer based in unrealistic probability, the answer is based on the facts of the case and physical principles that govern biomechanics and resultant injuries.

Individuals often use their wheelchair as a motor vehicle seat when traveling in motor vehicles. The current use of fixed vehicle-mounted wheelchair occupant restraint systems (FWORSs) often results in poor belt fit and discomfort. Additionally, satisfaction, usability and usage rate of FWORSs during transit use are often low. The automotive industry has shown improved occupant restraint usage, belt fit and injury protection when integrating the upper torso and pelvic restraint in a motor vehicle seat. This study compared occupant injury measures of a FWORS to a concept wheelchair integrated restraint system (WIRS) using a 20g frontal sled impact test with a 30 mph change in velocity. Neck loads, neck moments, head, pelvis and chest acceleration, sternum compression and knee and head excursion data were recorded from the wheelchair seated 50th percentile male hybrid III anthropomorphic test dummy (ATD). The WIRS resulted in a lower head injury criteria (HIC) value, lower sternum compression and a lower upper-torso restraint load than the FWORS. Compared with the FWORS, increased head, knee and wheelchair excursions and higher neck loads and moments were measured in the WIRS test. Both restraint scenario injury parameters were complied with occupant injury criteria based on General Motors Injury Assessment Reference Values (GM-IARVs) and occupant kinematic requirements defined by the Society of Automotive Engineers (SAE) voluntary standard, J2249. A higher motion criteria index was calculated for the WIRS scenario and a comparable combined injury criteria index was calculated for both restraint scenarios. The sled impact test showed WIRS concept feasibility, facilitating further development by industrial manufacturers who might further want to pursue this restraint principle to increase wheelchair occupant safety and comfort during transport in motor vehicles.

Objectives: To demonstrate the usefulness of computer simulation techniques in the investigation of pediatric stair falls. Since stair falls are a common falsely reported injury scenario in child abuse, our specific aim was to investigate the influence of stair characteristics on injury biomechanics of pediatric stair falls by using a computer simulation model. Our long-term goal is to use knowledge of biomechanics to aid in distinguishing between accidents and abuse., Methods: A computer simulation model of a 3-year-old child falling down stairs was developed using commercially available simulation software. This model was used to investigate the influence that stair characteristics have on biomechanical measures associated with injury risk. Since femur fractures occur in unintentional and abuse scenarios, biomechanical measures were focused on the lower extremities., Results: The number and slope of steps and stair surface friction and elasticity were found to affect biomechanical measures associated with injury risk., Conclusions: Computer simulation techniques are useful for investigating the biomechanics of stair falls. Using our simulation model, we determined that stair characteristics have an effect on potential for lower extremity injuries. Although absolute values of biomechanical measures should not be relied on in an unvalidated model such as this, relationships between accident-environment factors and biomechanical measures can be studied through simulation. Future efforts will focus on model validation.

To promote proper wheelchair securement in transportation, the proposed ANSI/RESNA Standard on Wheelchairs Used as Seats in Motor Vehicles will require that all transit wheelchairs be equipped with four securement points compatible with strap-type tiedowns. Through computer simulations, the location of these securement points has been found to influence wheelchair user response to a frontal crash. This study develops and employs an injury risk assessment method to compare the crashworthiness of various securement point configurations. The comparative injury risk assessment method is designed to predict the risk associated with internalized crash forces, as well as risk associated with secondary occupant impact with the vehicle interior. Injury criteria established by Federal Motor Vehicle Safety Standards and General Motors, along with excursion limitations set by the Society of Automotive Engineers (SAE) J2249 Wheelchair Tiedowns and Occupant Restraint Systems (WTORS) Standard were used as benchmarks for the risk assessment method. The simulation model subjected a secured commercial powerbase wheelchair with a seated 50th percentile male Hybrid III test dummy to a 20 g/30 mph crash. The occupant was restrained using pelvic and shoulder belts, and the wheelchair was secured with four strap-type tiedowns. Results indicated that securement points located 1.5 in to 2.5 in above the evaluated wheelchair's center of gravity provide the most effective occupant protection.

The Americans with Disabilities Act (ADA) has led to an increased number of wheelchair users seeking transportation services. Many of these individuals are unable to transfer to a vehicle and are instead required to travel seated in their wheelchairs. Unfortunately, wheelchairs are not typically designed with the same occupant protection features as motor vehicle seats, and wheelchair seated occupants may be at higher risk for injury in a crash. To study the effects of crash level forces on wheelchairs and their occupants, it is useful to simulate crash conditions using computer modeling. This study has used a dynamic lumped mass crash simulator, in combination with sled impact testing, to develop a model of a secured commercial powerbase and restrained occupant subjected to a 20 g/30 mph frontal motor vehicle crash. Time histories profiles of simulation-generated wheelchair kinematics, occupant accelerations, tiedown forces and occupant restraint forces were compared to sled impact testing for model validation. Validation efforts for this model were compared to validation results found acceptable for the ISO/SAE surrogate wheelchair model. This wheelchair-occupant simulation model can be used to investigate wheelchair crash response or to evaluate the influence of various factors on occupant crash safety.

The Americans with Disabilities Act (ADA) has led to an increase in disabled travelers, many of whom are unable to transfer to a vehicle seat and are required to use their wheelchair to fulfill this function. ANSI/RESNA is currently developing a transportable wheelchair standard which will identify design requirements and testing methods for wheelchairs suitable for transport. Wheelchair manufacturers should begin to modify their existing design criteria established for a normal mobility function to design criteria appropriate for a transportation function which may subject the wheelchair to large dynamic crash forces. A thorough understanding of the crash environment and its effect on the wheelchair is necessary to insure the safety of the wheelchair user. To assist manufacturers in the design effort, this study uses mathematical crash simulations to evaluate loads imposed upon a wheelchair when subjected to a 48 kph/20 g frontal crash. Using a four-point belt tiedown system to secure the wheelchair, securement point, seat, lap belt anchor, and wheel loads are evaluated under three different securement configurations. Results show that positioning of rear securement points near the wheelchair center of gravity can serve as an effective strategy for managing crash response and loadings on the wheelchair. Force ranges for each of the evaluated parameters, derived for a 50th percentile male using a simulated power wheelchair, are provided for use as a preliminary guide when designing transportable wheelchairs.

The quality of life of patients relying on electrically powered artificial organs is currently restricted by the limited energy availability provided by portable batteries. As these patients become increasingly ambulatory, and are developing more active lifestyles, this limitation grows more apparent. Coincidentally, these patients may themselves be capable of generating electrical power as a consequence of their physical activity. Extraction of this latent autologous energy could, in turn, be used to augment charging of internal batteries--thus untethering the patient from external power for extended periods of time. In this study, the viability of deriving energy associated with natural human ambulation has been evaluated. The kinematic components of gait were evaluated to identify the largest useful forces and moments that may be harnessed as an energy source, while presenting minimal "perceived" work for the patient. It was found that the ground reaction forces associated with the heel strike and toe-off phases of the gait represent the greatest potential for usable energy. This study uses a piezoelectric array within the midsole of the shoe for the conversion of mechanical to electric energy. This power could then be easily coupled in tandem with existing transcutaneous transformers for augmenting or temporarily replacing external power sources.