The Effect of Knee Height Asymmetry on Gait Biomechanics.

BACKGROUND: Though the primary goal for limb length discrepancy (LLD) management is to equalize the leg lengths, symmetry between corresponding long bones is usually not achieved, leading to knee height asymmetry (KHA). To date, there is minimal information on what effect KHA has on gait biomechanics and joint loading. Thus, the purpose of this study is to determine the impact of KHA on gait biomechanics. METHODS: Seventeen subjects with KHA after limb equalizing surgery and 10 healthy controls were enrolled. Subjects participated in 3D gait analysis collected using self-selected speed. Lower extremity kinematics, kinetics, work generated/absorbed, and total work were calculated. Standing lower limb x-rays and scanograms were used to measure LLD and calculate the tibia-to-femur (TF) ratio for each limb. Two sample t tests were used to compare differences in standing LLD, TF ratio, and work between groups. Bivariate correlation using Pearson correlation coefficients was conducted between TF ratio and total mechanical work, as well as between knee height asymmetry indices and total work asymmetry (α=0.05). RESULTS: Among participants, there were no differences between LLD; however, there were differences between TF ratio and knee height asymmetry. We found a nonsignificant relationship between TF ratio and total mechanical work for individual lower extremities. Therefore, the length of individual bones (TF ratio) relative to each other within the individual lower extremity was not associated with the amount of work produced. However, when a difference exists between sides (asymmetry, ie, TF ratio asymmetry), there were associated differences in work (work asymmetry) produced between sides (r=0.54, P=0.003). In other words, greater knee height asymmetry between limbs resulted in more asymmetrical mechanical work during walking. CONCLUSIONS: These findings may have implications for the management of LLD. Asymmetrical total mechanical work could lead to atypical joint loading during gait. Surgeons may want to consider prioritizing achieving knee height symmetry as a postoperative goal when correcting limb length discrepancy. LEVEL OF EVIDENCE: Level III, Case Control Study.

The incidence of avascular necrosis in children with cerebral palsy after hip containment surgery.

Purpose: To establish the rate of avascular necrosis after hip reconstruction surgery in children with cerebral palsy and to identify risk factors that influence the development of avascular necrosis in this population. Methods: An institutional review board-approved retrospective review was conducted on children with cerebral palsy who underwent hip containment surgery at a single institution. Radiographs were evaluated at three time points. The Reimer's migration percentage, neck shaft angle, epiphyseal shaft angle, acetabular index, center edge angle, and acetabular angle were measured. The presence of avascular necrosis was evaluated and graded by the Bucholz/Ogden and the Kalamchi/MacEwen classification systems. Multivariate logistic regression was performed to identify risk factors associated with the development of avascular necrosis. Results: A total of 154 children with cerebral palsy underwent hip containment surgery on 223 hips. Twenty-nine children (18.8%) underwent both pelvic and femoral procedures; 36 children (23.4%) had only femoral procedures; 47 children (30.5%) had femoral and soft tissue; and 42 children (27.3%) had pelvic, femoral, and soft tissue procedures. Using the Bucholz and Ogden or the Kalamchi classifications, the rate of avascular necrosis was 24.7% (38/154). Of the variables evaluated, preoperative Reimers was found to be significant predictors of avascular necrosis. The rate of avascular necrosis was 26.7% for Gross Motor Functional Classification System level III, 24.1% for Gross Motor Functional Classification System level IV, and 27.3% for Gross Motor Functional Classification System level V. Conclusion: The overall rate of avascular necrosis in children undergoing hip containment surgery was 26.7%. Together, age at surgery, open reduction, previous surgery, preoperative Reimers, and estimated blood loss contributed to the development of postoperative avascular necrosis; however, only preoperative Reimers significantly contributed to the development of avascular necrosis in children with cerebral palsy undergoing hip containment procedures.

Idiopathic Toe Walking: An Update on Natural History, Diagnosis, and Treatment.

Toe walking is a common presenting report to an orthopaedic practice. Evaluation of a child with toe walking includes a thorough history and physical examination to elucidate the diagnosis. When no other diagnosis is suspected, a diagnosis of idiopathic toe walking is often given. Despite the high prevalence of the condition, there is notable controversy of the nomenclature of the disease. Recent research has shed more light on both the natural history and the genetic basis. The use of motion analysis, including EMG and multisegment foot model, may help both differentiate children with mild forms of cerebral palsy and evaluate outcomes after treatment. Early treatment for young children with adequate range of motion (ROM) is generally reassurance because most young children with idiopathic toe walking are expected to resolve spontaneously. When the toe walking persists, treatment options include both surgical and nonsurgical management. Nonsurgical management centers on obtaining ROM through stretching and serial casting, followed by gait retraining and bracing treatment. Surgical lengthening at either the Achilles or gastrocnemius level improves the ROM of the ankle and then similarly requires therapy and bracing treatment to obtain a more normalized gait.

3D Gait Analysis and Patient-reported Outcomes of Femoral Osteotomies for Torsional Deformity.

BACKGROUND: Idiopathic torsional deformities causing pain and/or functional difficulty is an indication for a femoral derotational osteotomy (FDRO). Past studies have focused entirely on children with internal femoral torsional deformity (IFTD). This study aims to compare gait and outcomes between children with IFTD and those with external femoral torsional deformity (EFTD) after a FDRO. METHODS: A retrospective review of all patients who underwent an FDRO between 1997 and 2020 at our institution. Data on typically developing (TD) children with no torsional deformity was used as a control group. We analyzed preoperative and postoperative standardized physical examination, 3-dimensional gait analysis, and Pediatric Outcomes Data Collection Instrument questionnaires. RESULTS: There were 54 patients in total (IFTD=37, EFTD=17) and 20 patients in the control group. The EFTD cohort was older (IFTD=11.7, EFTD=14.7, P <0.05) and had a higher body mass index both preoperatively (IFTD=21.1 kg/m 2 , EFTD=32.1 kg/m 2 , P <0.05) and postoperatively (IFTD=20.2 kg/m 2 , EFTD=34.1 kg/m 2 , P <0.05). Preoperatively, 3-dimensional gait analysis elicited mean hip rotation in stance was more internal for IFTD cohort (10.8 degrees) and external for the EFTD cohort (-17.8 degrees) in comparison to the TD (2.4 degrees, P <0.001). Postoperatively, dynamic mean hip rotation during stance was -1.4 degrees for IFTD, whereas for EFTD, it was -5.4 degrees, which was different to the TD ( P <0.05). The IFTD group's Pediatric Outcomes Data Collection Instrument improved for transfer/basic mobility, sports/physical function, global functioning, and satisfaction with symptoms ( P <0.05). The EFTD group that only reported an improvement with the satisfaction with symptoms after surgery ( P <0.05). CONCLUSIONS: Adolescents with surgically corrected IFTD show more improvement in gait and in patient-reported outcomes than those with surgically corrected EFTD. Children with EFTD persist in external rotation and have less satisfactory patient-reported outcomes after a FDRO in comparison those with IFTD. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

The Effects of Lower Extremity Rotational Malalignment on Pediatric Patient-reported Outcomes Measurement and Information System (PROMIS) Scores.

BACKGROUND: There is sparse literature demonstrating the relationship between lower limb pediatric idiopathic rotational malalignment (IRM) and patient-reported outcomes measurement information system (PROMIS) scores. Our goal is to determine and quantify the amount that IRM deformities, as measured with the 3D gait analysis, affect childrens' pain interference, mobility, and peer relationship PROMIS domains. Secondary outcomes include investigating the potential relationships between IRM and various subgroups (Pediatric Outcomes Data Collection Instrument (PODCI), gender, Body Mass Index (BMI), femur Versus tibia). We also examine whether the PROMIS domains correlate with PODCI in this population. METHODS: This study was a retrospective cohort, single institution, and consecutively recruited cases series. We identified 47 children over a 3-year period who were evaluated at the motion analysis center at our tertiary care hospital, with increased torsion of the femur or tibia. After exclusions, 25 children with IRM, documented PROMIS data and gait analysis were considered. RESULTS: Femoral malrotation had a significant relationship with female gender ( P =0.001) and increased BMI ( P <0.001). Femoral malrotation had a correlation with PROMIS pain interference ( P =0.016), whereas tibial rotation did not achieve significance ( P =0.084). In the ANOVA regression analysis, there was a strong prediction of the PROMIS mobility domain when both malrotation and pain interference were present ( P =0.007). There were Pearson Correlations of PROMIS and PODCI domains for Mobility Versus Sports ( P =0.007) and Pain Interference Versus Comfort/Pain ( P =0.004), respectively. CONCLUSION: The evident relationship between lower limb rotational malalignment and PROMIS scores signifies the likelihood for gait and pain disturbance. This in turn could show us that children are likely to be more debilitated and thus may benefit from timely correction. We aim to conduct this as a multicentre trial to confirm our findings. LEVEL OF EVIDENCE: Level IV.

Patient-Reported Outcome Measurement Information System (PROMIS) Scores in Pediatric Idiopathic Toe Walkers.

BACKGROUND: Idiopathic toe walking (ITW) can result in early contact with the health care system and be distressing for patients and their families. The natural history of ITW is poorly characterized. Deciding how and when to intervene can be difficult.Patient-reported outcomes are utilized in the clinical setting to assess patient factors and indications that may better inform treatment plans. Patient-Reported Outcomes Measurement Information System (PROMIS) is an instrument designed to collect patient-reported outcomes. Minimum clinically important differences in PROMIS metrics have been established to facilitate clinical relevance and utility of these metrics. The purpose of this study was to characterize the patient perspective of ITW by utilizing the PROMIS scores. METHODS: Retrospective chart review was performed to identify children aged 5 to 17 with a diagnosis of ITW treated at a single tertiary care center between 2017 and 2020. Inclusion criteria were a diagnosis of ITW and completion of a PROMIS questionnaire. Exclusion criteria were neurologic disease, autism, and previous surgical treatment. Demographic, physical exam, treatment, and available motion analysis data were collected. PROMIS scores for the following domains were available: Mobility, Peer Relationships, and Pain Interference. RESULTS: Forty-five children were enrolled. Seventy-three percent of PROMIS scores were patient reported while the remainder were parent reported. PROMIS score means for the cohort by domain were Mobility: 45.2±8.2 ( P <0.000); Peer Relationships: 46.4±11.6 ( P =0.047); and Pain Interference: 47.4±9.5 ( P =0.67). Motion analysis data, available for 11 children, noted age-matched gait velocity negatively correlated ( rs =-0.652, P =0.03) with Peer Relationships. No correlations were found between other aspects of gait, body mass index, or limitations in dorsiflexion and PROMIS domains. Parents reported lower Mobility scores than children did. There were no other significant differences between patient-reported and parent-reported PROMIS scores. PROMIS scores did not differ significantly between those <10 years and those ≥10 years. CONCLUSION: In this cohort of 45 otherwise healthy children without other neurologic diagnoses, there are both clinically and statistically significant differences in PROMIS means between our cohort and the healthy age-matched population. These differences manifested in worse peer relationships and mobility scores. LEVEL OF EVIDENCE: Level IV.

Calf lengthening may improve knee recurvatum in specific children with spastic diplegic cerebral palsy.

PURPOSE: Knee hyperextension in stance is a difficult condition to treat in children with spastic diplegic cerebral palsy (CP). In children with passive knee hyperextension, the presence of contracture or spasticity of the calf leads to knee hyperextension in stance phase. We hypothesize surgical treatment of the contracture of the calf will lead to less knee hyperextension. METHODS: We performed a retrospective review of children who were evaluated in our movement laboratory over 23 years with a diagnosis of CP Gross Motor Function Classification System I, II or III. We selected children who had passive knee hyperextension on exam and who underwent calf lengthening surgery. Children were divided into two groups: early recurvatum (ER) (n = 20) and late recurvatum (LR) (n = 14). RESULTS: There was no difference in the preoperative passive knee extension among the groups or the surgeries performed. For children who had passive knee hyperextension, calf lengthening improved static dorsiflexion with knee flexion on clinical exam by 9.3° in the ER group, 9.6° in the LR group as well as dorsiflexion with knee extension on clinical exam by 9.5° in the ER group and 6.4° in the LR group. The kinematic data showed that the ER group improved their knee hyperextension by 11° (p < 0.001), whereas the LR group did not significantly change their stance phase knee position. CONCLUSION: Children with passive knee hyperextension who have a calf contracture and walk in knee hyperextension in the first half of stance phase may improve after calf lengthening.Level of Evidence: III.

Knee Recurvatum in Children With Spastic Diplegic Cerebral Palsy.

BACKGROUND: The purpose of this study is to determine which factors drive patients with diplegic cerebral palsy to walk without knee recurvatum despite hyperextension of the knee on physical examination. METHODS: A retrospective review was conducted of all data collected in the Gait Analysis Laboratory between 1999 and 2014. Patients with spastic diplegic cerebral palsy and at least 5 degrees of knee extension on clinical examination were identified for the study. After IRB approval, a total of 60 children ranging in age from 4 to 17 were included in the study. There were 27 female patients. Gross Motor Function Classification System level was distributed in the population as follows: 34 patients at Gross Motor Function Classification System level I, 18 at level II, and 8 at level III. Patients were excluded from this study if they had extrapyramidal involvement, history of selective dorsal rhizotomy or lower extremity surgery. Patient who received botulinum toxin A injections within 1 year of the study were excluded as well. Patients were divided into 2 groups: children that walked with knee hyperextension (KH) and children that walked without knee hyperextension (KF, "knee flexion"). There were 15 subjects in the KH group and 45 subjects in the KF group. Motion Laboratory evaluation included a comprehensive examination, kinematics, and kinetic analysis with a VICOM system. All data were analyzed with unpaired t test to detect differences between the 2 groups. All statistical analysis was done only for the right legs (unless the right leg did not meet the exclusion then the left leg was analyzed) to meet the statistical requirement for independence. The Pearson correlation was applied to correlate the maximum knee extension in stance with maximum ankle dorsiflexion in stance. RESULTS: The static measurement of dorsiflexion with knee flexed showed statistically significant difference (P=0.004) with KH group having 2.3±11.6 degrees and KF group having 13.1±12.2 degrees. There was also a statistically significant difference in the static measurement of dorsiflexion with knee extended (P=0.0014) with KH group having -3.3±9.0 degrees and KF group having 5.8±9.1 degrees. Maximum dorsiflexion in stance phase also showed significant difference (P=0.0022) with the KH group having 0.1±14.0 degrees and KF group having 11.5±11.2 degrees. Maximum dorsiflexion in stance phase also showed significant difference (P<0.001) with the DH group having 0.1 (SD) 14.0 degrees and KF group having 11.5 (SD) 11.2 degrees. There were no significant differences in popliteal angle measurements or any strength measurement. CONCLUSIONS: Our study shows that the plantar flexion knee extension couple is the major contributing factor to cause patients with passive knee hyperextension to walk in a recurvatum pattern. This would have implications of further treatment of the knee hyperextension in stance. LEVEL OF EVIDENCE: Level III-case-control study.

Do temporal scores of motivational constructs correspond with physical activity levels?

BACKGROUND: Adults with physical disabilities typically engage in low levels of physical activity (PA), thus a better understanding of how motivational factors and behavior vary over time and in relation to disability type and severity is needed. OBJECTIVE/HYPOTHESIS: To examine temporal changes in theory of planned behavior (TPB) constructs and PA by disability type (multiple sclerosis vs. spinal cord injury) and severity (mild, moderate, and severe). METHODS: Participants were 77 adults with physical disabilities who completed a web-based survey that assessed the TPB constructs and PA participation. The survey was completed once every four months for a total of three time points. Two-way repeated measures ANOVAs were used to examine if the TPB constructs and PA changed over time and in relation to disability type and severity. RESULTS: There was only one significant between-subjects effect for PA by disability severity, F (2, 68) = 5.94, p = .004, η2 = 15%. People with mild disabilities exhibited higher mean PA participation over the three time periods (M = 21.06 ±â€¯11.49 MET-hrs/day) than those with moderate disabilities (M = 11.27 ±â€¯9.3 MET-hrs/day) and severe disabilities (M = 13.43 ±â€¯14.74 MET-hrs/day). CONCLUSIONS: Although participants possessed positive PA motivational factors that remained stable over time, their PA participation was low and differed as a function of disability severity. Therefore, PA interventions should be tailored such that individuals with severe disabilities receive the greatest amount of exercise prescription consultations and supervision compared to those with more moderate and mild disabilities.

Multicentric reticulohistiocytosis: a case report of an atypical presentation in a 2-year-old.

Multicentric reticulohistiocytosis (MRH) is a rare systemic inflammatory granulomatous disease marked by severe and often rapidly progressive polyarticular arthritis and cutaneous papulonodules. Initial clinical diagnosis may be difficult. We describe a 2-year-old girl presenting with pink dermal papules on the forehead, thighs, elbows, knees, and palms of the hands. Based on clinical findings and skin biopsy results, she was initially diagnosed with granuloma annulare. At 5 years of age, she developed arthritis, fatigue, and more widespread skin papules leading to the diagnosis of MRH. To our knowledge, this is the youngest individual with MRH yet described. We outline the timeline and unique features of her case and review the literature pertaining to MRH in children. Although rare, MRH can be permanently debilitating, making prompt diagnosis critical. A standardized approach to investigation and management needs to be developed.

Physiological mechanisms that underlie the effects of interactional unfairness on deviant behavior: the role of cortisol activity.

Although experiencing unfairness is a primary source of stress, there are surprisingly few studies that have examined the physiological underpinnings of unfairness. Drawing from social self-preservation theory, we derive predictions regarding the effects of interactional unfairness on activity in the hypothalamic-pituitary-adrenocortical (HPA) axis, which is one of the body's primary hormonal systems for responding to stress. Using an experimental design with objective physiological measures, we found support for our hypothesis that interactional unfairness triggers the release of cortisol by the HPA axis. This cortisol activity in turn mediated the effects of interactional unfairness on deviant behavior. This indirect effect remained significant after controlling for established attitudinal and self-construal mediators of the justice-deviance relationship. We discuss the theoretical and practical implications of these findings for the occupational stress and organizational justice literatures.

Acetabular retroversion in post slipped capital femoral epiphysis deformity.

PURPOSE: While the femoral deformity in post slipped capital femoral epiphysis (SCFE) hips has been implicated in the development of femoral acetabular impingement, little has been studied about the acetabular side. The purpose of our study was to determine the frequency of morphologic changes suggestive of acetabular retroversion in patients who have sustained a SCFE. METHODS: IRB approval was obtained and the records of patients from 1975 to 2010 were searched for ICD-9 codes for SCFE. A total of 188 patients were identified for the study. Two observers evaluated AP radiographs for evidence of acetabular retroversion as characterized by the presence of either an ischial spine sign or a crossover sign. Demographic data, date of onset, and treatment were recorded. For analysis, the right hip was used in patients with bilateral involvement. RESULTS: Of the 188 patients identified, 5 patients had an incorrect diagnosis and 41 patients had missing or inadequate films, leaving 142 patients (284 hips) for review. 57 patients (114 hips) had bilateral SCFE and 85 patients had unilateral SCFE. 79 % (n = 45) of the right hips with bilateral SCFE and 82 % (n = 70) of the unilateral involved hips had at least one sign of retroversion. Uninvolved hips had at least one sign of retroversion 76 % (n = 65) of the time. CONCLUSIONS: When compared to previously published values for normal patients, patients with SCFE appear to have an increased incidence of acetabular retroversion.

Longitudinal changes in psychosocial constructs and physical activity among adults with physical disabilities.

BACKGROUND: Given the importance of physical activity (PA) and the low activity levels among adults with physical disabilities, it is important to understand how temporal changes in psychosocial constructs affect PA changes over time. OBJECTIVE/HYPOTHESIS: Examine if changes in the transtheoretical model (TTM) constructs affected changes in PA levels over time. METHODS: One hundred thirty-two adults with physical disabilities, such as multiple sclerosis and spinal cord injuries, completed a web-based survey once every 4 months, for a total of 3 time points, to assess the TTM constructs and PA. Six latent growth curve analyses were conducted using Mplus(5) to examine if longitudinal changes in the TTM constructs affected temporal changes in PA levels. RESULTS: All six hypothesized models fit the sample data well (e.g., χ(2) = NS; RMSEA = <.001-.06). In a descending order of significance, the best predictors of the initial levels of PA were the stages of change, the behavioral processes of change, the cognitive processes of change, self-efficacy, and perceived pros. The meaningful predictors of PA changes over time were the initial levels and the slopes of the cognitive processes of change, perceived pros, and the behavioral processes of change. Although the slopes of the stages of change and perceived cons did not have a statistically significant effect on PA changes, their effects approached a medium size (.33 and .38, respectively). CONCLUSIONS: In order to reassure the maintenance of an exercise program, interventionists need to first emphasize cognitive, motivational strategies (cognitive processes of change), such as the importance of PA and positive thoughts about exercise participation as well as exercise benefits (pros) before they implement behavioral strategies (behavioral processes of change), such as social support, goal setting, and self-rewarding.

Measurement artifacts in the assessment of counterproductive work behavior and organizational citizenship behavior: do we know what we think we know?

An experiment investigated whether measurement features affected observed relationships between counterproductive work behavior (CWB) and organizational citizenship behavior (OCB) and their relationships with other variables. As expected, correlations between CWB and OCB were significantly higher with ratings of agreement rather than frequency of behavior, when OCB scale content overlapped with CWB than when it did not, and with supervisor rather than self-ratings. Relationships with job satisfaction and job stressors were inconsistent across conditions. We concluded that CWB and OCB are likely unrelated and not necessarily oppositely related to other variables. Researchers should avoid overlapping content in CWB and OCB scales and should use frequency formats to assess how often individuals engage in each form of behavior.

Psychosocial predictors of physical activity and health-related quality of life among adults with physical disabilities: an integrative framework.

BACKGROUND: People with disabilities report lower physical activity (PA) and health-related quality of life (HRQOL) levels than people without disabilities. Therefore, it is important to identify factors that motivate individuals with disabilities to be physically active and thus increase their HRQOL. OBJECTIVES: The purpose of the study was to prospectively explore the effects of past theory of planned behavior (TPB) constructs on future (6-month) HRQOL (physical and mental health) through past stages of change (SOC) and future (6-month) PA among adults with physical disabilities. Two models were tested whereby the SOC and PA served as the mediators between the TPB constructs, physical health (PH-Model), and mental health (MH-Model). It was hypothesized that both models would fit the sample data. METHODS: Participants were 141 adults with physical disabilities (mean age = 46.04, females = 70.9%). The online survey was completed at two different time periods. First, the TPB constructs and SOC were assessed using self-report standardized questionnaires. Six months later, participants completed standardized self-report scales about their PA and HRQOL levels. Using LISREL 8, two path analyses were conducted to examine the two study models (PH-Model and MH-Model). RESULTS: Based on the two path analyses, attitude had the highest effect on SOC followed by perceived behavioral control within both well-fit models. The PH-Model explained more variance in PA (26%) and physical health (55%) than the MH-Model. CONCLUSIONS: Health promoters should reinforce both positive intentions and behavioral experiences to increase PA and HRQOL among adults with physical disabilities.

Physical activity beliefs and behaviour of adults with physical disabilities.

PURPOSE: The purpose of this study was to elicit the physical activity (PA) beliefs from adults with physical disabilities; and second, to examine their self-reported PA participation. METHOD: Participants were 223 adults (M age = 45.4 years, SD = 10.8), with self-reported physical disabilities who completed a web-based survey. Six open-ended questions were used to assess PA beliefs and the PA Scale for Individuals with Physical Disabilities measured self-reported PA. RESULTS: A qualitative analysis showed that the most accessible behavioural advantages are that PA improves emotional functioning and assists with weight management. The most accessible behavioural disadvantages are that PA causes pain or soreness and consumes time. The most accessible normative influences that approve of PA are family, friends, and healthcare professionals. The most accessible control beliefs obstructing PA are disability and associated symptoms, and a lack of access to adequate facilities, equipment, or programs. The most accessible control beliefs that facilitate PA are access to adequate facilities, equipment, or programs, and support or assistance. Finally, the average total PA score was 20.5 metabolic equivalent (METS)-hours/day (SD = 16.8). CONCLUSIONS: Adults with physical disabilities possess unique PA beliefs that can be used to design health promotion interventions to increase PA participation.

The mediating role of intention and stages of change in physical activity among adults with physical disabilities: an integrative framework.

The study's purpose was to identify the mediating role of intention and the stages of change (SOC) in physical activity (PA) over a 6-month period using two models (theory of planned behavior [TPB] and TPB/SOC). Participants were 143 adults with physical disabilities (70.68% response rate; M age = 46.03). The TPB constructs, SOC (time 1), and PA (time 2) were assessed using standardized self-report questionnaires. Based on path analyses, attitude had the highest effect on intention and SOC followed by perceived behavioral control within both well-fit models. The variance in PA explained by the first (TPB) and second (TPB/SOC) models was 16% and 28% respectively. In the just identified model of TPB/SOC, the direct effect of SOC on physical activity remained strong (gamma(soc.pa) = .45) and SOC approached full mediation through attitude. Health promotion interventions need to include both intention and behavior elements (SOC) reinforcing increased PA value and barrier elimination.

MRI-derived body segment parameters of children differ from age-based estimates derived using photogrammetry.

Body segment parameters are required when researching joint kinetics using inverse dynamics models. However, the only regression equations for estimating pediatric body segment parameters across a wide age range were developed, using photogrammetry, based on 12 boys and have not been validated to date (Jensen, R.K., 1986. Body segment mass, radius and radius of gyration proportions of children. Journal of Biomechanics 19, 359-368). To assess whether these equations could validly be applied to girls, we asked whether body segment parameters estimated by the equations differ from parameters measured using a validated magnetic resonance imaging (MRI) method. If so, do the differences cause significant differences in joint kinetics during normal gait? Body segment parameters were estimated from axial MRIs of the left thigh and shank of 10 healthy girls (9.6 +/- 0.9 years) and compared to those from Jensen's equations. Kinematics and kinetics were collected for 10 walking trials. Extrema in hip and knee moments and powers were compared between the two sets of body segment parameters. With the exception of the shank mass center and radius of gyration, body segment parameters measured using MRI were significantly different from those estimated using regression equations. These systematic differences in body segment parameters resulted in significant differences in sagittal-plane joint moments and powers during gait. Nevertheless, it is doubtful that even the greatest differences in kinetics are practically meaningful (0.3% BW x HT and 0.7% BW x HT/s for moments and power at the hip, respectively). Therefore, body segment parameters estimated using Jensen's regression equations are a suitable substitute for more detailed anatomical imaging of 8-10-year-old girls when quantifying joint kinetics during gait.