Prognostic model development for risk of curve progression in adolescent idiopathic scoliosis: a prospective cohort study of 127 patients.

BACKGROUND AND PURPOSE:  The study's purpose was to develop and internally validate a prognostic survival model exploring baseline variables for adolescent idiopathic scoliosis curve progression. METHODS:  A longitudinal prognostic cohort analysis was performed on trial data (n = 135) including girls and boys, Cobb angle 25-40°, aged 9-17 years, remaining growth > 1 year, and previously untreated. Prognostic outcome was defined as curve progression of Cobb angle of > 6° prior to skeletal maturity. 34 candidate prognostic variables were tested. Time-to-event was measured with 6-month intervals. Cox proportional hazards regression survival model (CoxPH) was used for model development and validation in comparison with machine learning models (66.6/33.3 train/test data set). The models were adjusted for treatment exposure. RESULTS:  The final primary prognostic model included 127 patients, predicting progress with acceptable discriminative ability (concordance = 0.79, 95% confidence interval [CI] 0.72-0.86). Significant prognostic risk factors were Risser stage of 0 (HR 4.6, CI 2.1-10.1, P < 0.001), larger major curve Cobb angle (HRstandardized 1.5, CI 1.1-2.0, P = 0.005), and higher score on patient-reported pictorial Spinal Appearance Questionnaire (pSAQ) (HRstandardized 1.4, CI 1.0-1.9, P = 0.04). Treatment exposure, entered as a covariate adjustment, contributed significantly to the final model (HR 3.1, CI 1.5-6.0, P = 0.001). Sensitivity analysis displayed that CoxPH maintained acceptable discriminative ability (AUC 0.79, CI 0.65-0.93) in comparison with machine learning algorithms. CONCLUSION:  The prognostic model (Risser stage, Cobb angle, pSAQ, and menarche) predicted curve progression of > 6° Cobb angle with acceptable discriminative ability. Adding patient report of the pSAQ may be of clinical importance for the prognosis of curve progression.

Prevalence and intensity of pain in male and female amateur football players: A prospective cohort study.

OBJECTIVES: To determine the prevalence and intensity of pain due to a football-related injury during activities of daily living and during training and/or match play in both male and female and youth and adult amateur players. DESIGN: A prospective cohort study involving amateur football players. METHODS: Players (n = 502, median age 18 years, range 14-46) responded to weekly questionnaires during one season, including the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. Weekly pain prevalence and pain intensity (measured on the numeric rating scale [range 0-10]) during activities of daily living and while playing football were determined. RESULTS: A total of 6601 weekly questionnaires were collected (response rate 63.7 %). Average weekly pain prevalence during activities of daily living was 17.2 % for all players, and 15.7 % among players who participated in training and/or match play. Pain prevalence during training and/or match play was 18.3 % with an average pain intensity of 4.0. In 21.3 % of cases the recorded pain intensity was >5. Sex, age, and mode of injury onset (sudden or gradual) were not significant predictors of pain intensity. CONCLUSION: At a given week, one in six football players experiences pain during activities of daily living from a football-related injury. Almost one in five players reports pain while playing football, of whom >20% report a pain intensity above 5. Oftentimes, injury-related pain present while playing football transcends to activities of daily living. This warrants further monitoring and adequate management of pain within amateur football.

Cardiorespiratory fitness and physical strain during prosthetic rehabilitation after lower limb amputation.

BACKGROUND: Sufficient cardiorespiratory fitness has been regarded a prerequisite for prosthetic walking. In order to improve cardiorespiratory fitness, adequate strain ought to be placed on the system during training. OBJECTIVES: To determine cardiorespiratory fitness at the start and end of inpatient rehabilitation after lower limb amputation and determine the physical strain experienced during conventional prosthetic rehabilitation. STUDY DESIGN: Multicenter prospective cohort study. METHODS: Cardiorespiratory fitness was assessed using a peak one-legged cycle exercise test. Physical strain was assessed during a minimum of three full rehabilitation days using heart rate recordings. Physical strain was expressed in the time per day that heart rate exceeded 40% of heart rate reserve. RESULTS: At the start of rehabilitation, peak aerobic capacity was on average 16.9 (SD, 6.5) mL/kg/min (n = 33). Overall, peak aerobic capacity did not improve over the course of rehabilitation (n = 23, p = 0.464). Fifty percent of the patients experienced a physical strain level that satisfies minimum criteria for maintaining cardiorespiratory fitness (>40% heart rate reserve for 30 min/day). CONCLUSION: Cardiorespiratory fitness was low and did not increase during conventional prosthetic rehabilitation. On average, the physical strain during rehabilitation was insufficient to elicit potential improvements in aerobic capacity. Results stress the need for dedicated physical training modules at the individual level. CLINICAL RELEVANCE: This study shows that clinicians ought to be aware of the relatively low cardiorespiratory fitness of people who have undergone lower limb amputation and that improvements during rehabilitation are not always obtained. Results stress the need for physical training modules in which intensity is imposed at the individual level.

Energy storing and return prosthetic feet improve step length symmetry while preserving margins of stability in persons with transtibial amputation.

BACKGROUND: Energy storing and return (ESAR) feet are generally preferred over solid ankle cushioned heel (SACH) feet by people with a lower limb amputation. While ESAR feet have been shown to have only limited effect on gait economy, other functional benefits should account for this preference. A simple biomechanical model suggests that enhanced gait stability and gait symmetry could prove to explain part of the difference in the subjective preference between both feet. AIM: To investigate whether increased push-off power with ESAR feet increases center of mass velocity at push off and enhance intact step length and step length symmetry while preserving the margin of stability during walking in people with a transtibial prosthesis. METHODS: Fifteen people with a unilateral transtibial amputation walked with their prescribed ESAR foot and a SACH foot at a fixed walking speed (1.2 m/s) over a level walkway while kinematic and kinetic data were collected. Push-off work generated by the foot, center of mass velocity, step length, step length symmetry and backward margin of stability were assessed and compared between feet. RESULTS: Push-off work was significantly higher when using the ESAR foot compared to the SACH foot. Simultaneously, center of mass velocity at toe-off was higher with ESAR compared to SACH, and intact step length and step length symmetry increased without reducing the backward margin of stability. CONCLUSION: Compared to the SACH foot, the ESAR foot allowed an improvement of step length symmetry while preserving the backward margin of stability at community ambulation speed. These benefits may possibly contribute to the subjective preference for ESAR feet in people with a lower limb amputation.

Shotgun approaches to gait analysis: insights & limitations.

BACKGROUND: Identifying features for gait classification is a formidable problem. The number of candidate measures is legion. This calls for proper, objective criteria when ranking their relevance. METHODS: Following a shotgun approach we determined a plenitude of kinematic and physiological gait measures and ranked their relevance using conventional analysis of variance (ANOVA) supplemented by logistic and partial least squares (PLS) regressions. We illustrated this approach using data from two studies involving stroke patients, amputees, and healthy controls. RESULTS: Only a handful of measures turned out significant in the ANOVAs. The logistic regressions, by contrast, revealed various measures that clearly discriminated between experimental groups and conditions. The PLS regression also identified several discriminating measures, but they did not always agree with those of the logistic regression. DISCUSSION & CONCLUSION: Extracting a measure's classification capacity cannot solely rely on its statistical validity but typically requires proper post-hoc analysis. However, choosing the latter inevitably introduces some arbitrariness, which may affect outcome in general. We hence advocate the use of generic expert systems, possibly based on machine-learning.

Differentiation between solid-ankle cushioned heel and energy storage and return prosthetic foot based on step-to-step transition cost.

Decreased push-off power by the prosthetic foot and inadequate roll-over shape of the foot have been shown to increase the energy dissipated during the step-to-step transition in human walking. The aim of this study was to determine whether energy storage and return (ESAR) feet are able to reduce the mechanical energy dissipated during the step-to-step transition. Fifteen males with a unilateral lower-limb amputation walked with their prescribed ESAR foot (Vari-Flex, Ossur; Reykjavik, Iceland) and with a solid-ankle cushioned heel foot (SACH) (1D10, Ottobock; Duderstadt, Germany), while ground reaction forces and kinematics were recorded. The positive mechanical work on the center of mass performed by the trailing prosthetic limb was larger (33%, p = 0.01) and the negative work performed by the leading intact limb was lower (13%, p = 0.04) when walking with the ESAR foot compared with the SACH foot. The reduced step-to-step transition cost coincided with a higher mechanical push-off power generated by the ESAR foot and an extended forward progression of the center of pressure under the prosthetic ESAR foot. Results can explain the proposed improvement in walking economy with this kind of energy storing and return prosthetic foot.

Relation between aerobic capacity and walking ability in older adults with a lower-limb amputation.

OBJECTIVES: To determine the relative aerobic load, walking speed, and walking economy of older adults with a lower-limb prosthesis, and to predict the effect of an increased aerobic capacity on their walking ability. DESIGN: Cross-sectional. SETTING: Human motion laboratory at a rehabilitation center. PARTICIPANTS: Convenience sample of older adults (n=36) who underwent lower-limb amputation because of vascular deficiency or trauma and able-bodied controls (n=21). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak aerobic capacity and oxygen consumption while walking were determined. The relative aerobic load and walking economy were assessed as a function of walking speed, and a data-based model was constructed to predict the effect of an increased aerobic capacity on walking ability. RESULTS: People with a vascular amputation walked at a substantially higher (45.2%) relative aerobic load than people with an amputation because of trauma. The preferred walking speed in both groups of amputees was slower than that of able-bodied controls and below their most economical walking speed. We predicted that a 10% increase in peak aerobic capacity could potentially result in a reduction in the relative aerobic load of 9.1%, an increase in walking speed of 17.3% and 13.9%, and an improvement in the walking economy of 6.8% and 2.9%, for people after a vascular or traumatic amputation, respectively. CONCLUSIONS: Current findings corroborate the notion that, especially in people with a vascular amputation, the peak aerobic capacity is an important determinant for walking ability. The data provide quantitative predictions on the effect of aerobic training; however, future research is needed to experimentally confirm these predictions.

Peak oxygen consumption in older adults with a lower limb amputation.

OBJECTIVE: To investigate whether the aerobic capacity of older adults who underwent a lower limb amputation is associated with the presence, cause (traumatic or vascular), and level of amputation (transtibial or transfemoral). DESIGN: Cross-sectional descriptive. SETTING: Human motion laboratory at a rehabilitation center. PARTICIPANTS: Older subjects (n=36) who underwent lower limb amputation and age-matched, able-bodied controls (n=21). All subjects were able to walk for a minimum of 4 minutes. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Peak oxygen consumption (Vo(2)(peak)) was measured using open-circuit respirometry while performing a discontinuous, graded, 1-legged, peak cycle exercise test. RESULTS: After correcting for age, body mass index, and sex, the multiple linear regression analysis revealed that subjects who underwent amputation had a 13.1% lower aerobic capacity compared with able-bodied controls (P=.021). Differentiation among etiologies revealed that subjects with a vascular amputation had a lower Vo(2)(peak) of 29.1% compared with able-bodied controls (P<.001), whereas traumatic amputees did not differ from able-bodied controls (P=.127). After correcting for etiology, no association between level of amputation and Vo(2)(peak) was found (P=.534). CONCLUSIONS: Older adults who underwent an amputation because of vascular deficiency had a lower aerobic capacity compared with able-bodied controls and people with a traumatic amputation. The level of amputation was not associated with Vo(2)(peak).

Feasibility and validity of a graded one-legged cycle exercise test to determine peak aerobic capacity in older people with a lower-limb amputation.

BACKGROUND: Information concerning exercise tolerance and aerobic capacity is imperative for generating effective and safe exercise programs. However, for older people with a lower-limb amputation, a standard exercise test is not available. OBJECTIVE: The primary aim of the present study was to determine whether a graded 1-legged peak exercise test is feasible and provides a valid assessment of peak aerobic capacity in older people walking with a lower-limb prosthesis. DESIGN: This was a quasi-experimental case-control study. METHODS: A total of 36 older people with a lower-limb prosthesis and 21 people who were able-bodied (controls) (overall mean age=61.7 years, SD=6.1) performed a discontinuous graded 1-legged exercise test. The peak respiratory exchange ratio was used as an indicator of maximal effort. The controls performed an additional 2-legged exercise test to provide insight into differences between the testing modes. RESULTS: All participants were able to perform the exercise test. Electrocardiographic tracings and blood pressure were adequately monitored. The controls and the people with a lower-limb amputation were able to stress the cardiovascular system to a similar extent. Analyses of construct validity revealed that the peak aerobic capacity measured with the 1-legged exercise test was able to distinguish between participants on the basis of age, body mass index, and sex to a similar extent as the conventional 2-legged exercise test. LIMITATIONS: The results can be generalized only to people who are able to ambulate with their prosthesis. CONCLUSIONS: The graded 1-legged exercise test was feasible and provided a valid assessment of peak aerobic capacity and exercise tolerance in older people walking with a lower-limb prosthesis.

Armed against falls: the contribution of arm movements to balance recovery after tripping.

Arm movements after perturbations like tripping over an obstacle have been suggested to be aspecific startle responses, serve a protective function or contribute to balance recovery. This study aimed at determining if and how arm movements play a functional role in balance recovery after a perturbation. We tripped young subjects using an obstacle that suddenly appeared from the floor at exactly mid-swing. We measured arm muscle EMG, quantified body rotations after tripping, and established the effects of arm movements by calculating how the body would have rotated without arms. Strong asymmetric shoulder muscle responses were observed within 100 ms after trip initiation. Significantly faster and larger responses were found in the contralateral arm abductors on the non-tripped (right) side. Mean amplitudes were larger in the ipsilateral retroflexors and contralateral anteflexors. The resulting asymmetric arm movements had a small effect on body rotation in the sagittal and frontal planes, but substantially affected the body orientation in the transverse plane. With the enlargement of the ongoing arm swing, the arms contributed to balance recovery by postponing the transfer of arm angular momentum to the trunk. This resulted in an axial rotation of the lower segments of the body towards the non-tripped side, which increases the length of the recovery step in the sagittal plane, and therefore facilitates braking the impending fall.