Jon R. Davids

A Biomechanical Analysis of Gait During Pregnancy

Background: There are many anatomical changes during pregnancy that could potentially lead to substantial alterations in gait. Gait deviations may contribute to a variety of musculoskeletal overuse conditions associated with pregnancy, such as low-back, hip, and calf pain. Because we are aware of little research on this topic, the purpose of this study was to objectively analyze gait during pregnancy. Methods: Three-dimensional gait analysis was performed on fifteen women during the second half of the last trimester of pregnancy and again one year post partum. Selected kinematic and kinetic parameters for the pregnancy and one-year postpartum conditions were compared with use of paired t tests (95 percent significance level). Results: Overall, gait kinematics were remarkably unchanged during pregnancy. No evidence of a so-called waddling gait during pregnancy was found. Maximum anterior pelvic tilt during gait increased a mean of 4 degrees during pregnancy, although individual subject-to-subject variation (range, an increase of 13 degrees to a decrease of 10 degrees) was observed. Significant increases in hip and ankle kinetic gait parameters, however, were observed during pregnancy (p < 0.05). Conclusions: Significant increases in kinetic gait parameters during pregnancy (p < 0.05) explain how gait motion remained relatively unchanged despite increases in body mass and width as well as changes in mass distribution about the trunk. This finding indicates that during pregnancy there may be an increased demand placed on hip abductor, hip extensor, and ankle plantar flexor muscles during walking. Clinical Relevance: Many of the common musculoskeletal problems associated with pregnancy may be due, in part, to musculoskeletal overuse injuries incurred as a consequence of secondary gait deviations that compensate for changes in body mass and distribution. Physicians caring for pregnant women with musculoskeletal problems should emphasize the value of exercise and conditioning during pregnancy for both preventative and rehabilitative management.

Quantitative segmental analysis of weight-bearing radiographs of the foot and ankle for children : Normal alignment

Clinical decision-making for the management of foot deformities in children is primarily based upon the analysis of weight-bearing radiographs of the foot and ankle. However, a comprehensive quantitative technique for the analysis of such radiographs has not been described. Ten radiographic measurements were developed and applied to the foot and ankle radiographs of a normal foot and ankle in 60 children (mean age 10 years, range 5-17 years). Intraobserver variability and interobserver variability were determined for 10 cases. Mean values for the 10 measurements were calculated from the entire study group. Intraobserver variability was excellent, with correlation coefficients for the 10 measurements ranging from 0.89 to 0.99. The absolute value of the mean differences in angular measurements ranged from 0.8 to 2.5 degrees. Interobserver variability was also excellent, with correlation coefficients ranging from 0.86 to 0.99. The absolute value of the mean differences in angular measurements ranged from 0.5 to 3.2 degrees. The mean values, standard deviations, and ranges for the 10 radiographic parameters from the 60 normal feet have been determined. Clinically acceptable variability of 10 selected radiographic measurements of the foot and ankle was achieved, and normal values and ranges for these measurements were determined. Quantitative segmental analysis of foot and ankle alignment, using these 10 radiographic measurements, can be used to describe common malalignment patterns, and this may assist in clinical decision-making and assessment of outcome.

Validation of the Shriners Hospital for Children Upper Extremity Evaluation (SHUEE) for Children with Hemiplegic Cerebral Palsy

BACKGROUND The Shriners Hospital for Children Upper Extremity Evaluation (SHUEE) is a video-based tool for the assessment of upper extremity function in children with hemiplegic cerebral palsy. This tool includes spontaneous functional analysis and dynamic positional analysis and assesses the ability to perform grasp and release. The purpose of the present study was to assess the reliability, concurrent validity, and construct validity of this instrument. METHODS The Shriners Hospital for Children Upper Extremity Evaluation studies for eleven subjects with hemiplegic cerebral palsy were selected for the evaluation of intraobserver and interobserver reliability. Concurrent validity was determined through analysis of the Shriners Hospital for Children Upper Extremity Evaluation, Pediatric Evaluation of Disability Inventory, and Jebson-Taylor Test of Hand Function scores for twenty children. Construct validity was determined through analysis of Shriners Hospital for Children Upper Extremity Evaluation scores for eighteen children before and after flexor carpi ulnaris to extensor carpi radialis brevis tendon transfer. RESULTS The absolute mean differences between the two scoring sessions for three raters were 1.2 and 1.0 for the spontaneous functional analysis and the dynamic positional analysis, respectively. Although the mean differences were significantly different from 0 (p < 0.001 and p = 0.003), the differences were small and not clinically important with regard to the total possible score. There was excellent intraobserver reliability between the two sessions with regard to both spontaneous functional analysis (r = 0.99) and dynamic positional analysis (r = 0.98). Assessment of interobserver reliability revealed absolute mean differences between four raters of 3.8 and 3.7 for the spontaneous functional analysis and the dynamic positional analysis, respectively. These differences were significantly different from 0 (p < 0.001); however, the magnitudes of these differences were not important with regard to total score or clinical interpretation. There was excellent interobserver reliability for both the spontaneous functional analysis (r = 0.90) and the dynamic positional analysis (r = 0.89). There was 100% agreement within and between examiners for the grasp-and-release section. The Shriners Hospital for Children Upper Extremity Evaluation showed fair correlation with the self-care scaled score from the Pediatric Evaluation of Disability Inventory (r = 0.47) and good inverse correlation with the non-dominant total time section of the Jebson-Taylor test (r = -0.76). The Shriners Hospital for Children Upper Extremity Evaluation wrist score improved for all eighteen subjects after the flexor tendon transfer, and the mean improvement was significant (p < 0.001). CONCLUSIONS The present study establishes the clinical reliability, concurrent validity, and construct validity of the Shriners Hospital for Children Upper Extremity Evaluation for the assessment of upper extremity function in children with hemiplegic cerebral palsy.

Lateral condylar fracture of the humerus following posttraumatic cubitus varus.

Posttraumatic cubitus varus is widely regarded as just a cosmetic deformity. Six cases of lateral condylar fracture of the humerus in children with preexisting cubitus varus due to prior elbow fracture are presented. Five occurred following malunited extension-type supracondylar fractures of the humerus; the other occurred following a lateral condylar fracture complicated by lateral overgrowth. All cases were treated by anatomic reduction (two closed, four open) and percutaneous pinning of the lateral condylar fracture. Three of the six cases subsequently underwent supracondylar osteotomy of the distal humerus to correct the underlying varus malalignment. Biomechanical analysis suggests that both the torsional moment and the shear force generated across the capitellar physis by a routine fall are increased by varus malalignment. Posttraumatic cubitus varus may predispose a child to subsequent lateral condylar fracture and should be viewed as more than just a cosmetic deformity.

Optimization of walking ability of children with cerebral palsy.

A new paradigm based on an appreciation of the biomechanics of normal and pathologic gait and a better understanding of muscle-tendon unit anatomy and physiology has emerged for orthopaedic clinical decision making to optimize the ambulatory abilities of children with cerebral palsy. This quantitative, biomechanically based approach has been accepted as a research and teaching tool and as an instrument of outcome assessment; however, controversy remains concerning the expense of using this approach and about its accuracy and repeatability. This paradigm is used within a diagnostic matrix consisting of five data sources. Members of the clinical and technical teams from the motion analysis laboratory interpret data from the clinical history, physical examination, diagnostic imaging, quantitative gait analysis, and examination under anesthesia. The certainty of intervention selection is proportional to the consistency of the data within the diagnostic matrix. When inconsistencies in the data exist, input from both the clinical and technical teams is needed to resolve discrepancies. Working within the framework of the diagnostic matrix, it is possible to identify the indications used in the selection and recommendation of musculoskeletal surgical interventions to optimize gait in children with cerebral palsy. It is important to examine indications and controversies for surgical intervention related to iliopsoas recession, femoral rotational osteotomy, medial hamstring lengthening, rectus femoris transfer, and gastrocnemius recession.

Prevalence of obesity in ambulatory children with cerebral palsy.

BACKGROUND According to the most recent data, an estimated 17.1% of children in the United States are obese. We found no published studies documenting the prevalence of obesity in ambulatory children with cerebral palsy. The purpose of this study was to document the prevalence of obesity in ambulatory children with cerebral palsy and examine the trend in this measure over the last decade. METHODS A retrospective review was performed to analyze the age, gender, height, weight, physical classification of the cerebral palsy, and functional level as determined with the Gross Motor Function Classification System (GMFCS) of all children with cerebral palsy who had a gait analysis performed in the Motion Analysis Laboratory of our institution between January 1994 and December 2004. This information was used to determine the prevalence of obesity (a body mass index in or above the 95th percentile of the sex-specific body mass index-for-age growth chart) in this population and its relationship to age, gender, the physical classification of the cerebral palsy, and the GMFCS level. RESULTS When the data were grouped into three time periods (1994 to 1997, 1998 to 2002, and 2003 to 2004), a significant increase in obesity over time was noted (p = 0.017). The prevalences increased from 7.7% to 14% to 16.5% in the respective time periods. The prevalence increased over time in both males and females, those with hemiplegia and those with diplegia, and those with level-I function and those with level-II function according to the GMFCS. The association between obesity and time was significant in the female (p = 0.015), hemiplegic (p = 0.049), less than eight-year-old (p = 0.020), and GMFCS level-II (p = 0.003) groups. We found that the time period was independently associated with obesity when we controlled for age, type of cerebral palsy, and GMFCS level (p = 0.014). Children with a lesser degree of involvement (GMFCS level II) had twice the odds of becoming obese than did children with greater involvement (GMFCS level III). CONCLUSIONS The prevalence of obesity in ambulatory children with cerebral palsy has risen over the last decade from 7.7% to 16.5%, an increase that is similar to that seen in the general pediatric population in the United States. This finding may have a major impact on the general health and functional abilities of these children as they reach adult life.

Indications for magnetic resonance imaging in presumed adolescent idiopathic scoliosis

BACKGROUND The use of magnetic resonance imaging has led to the diagnosis of abnormalities of the central nervous system associated with apparent idiopathic scoliosis. The indications for magnetic resonance imaging for presumed adolescent idiopathic scoliosis have not been established. METHODS One thousand, two hundred and eighty children with presumed adolescent idiopathic scoliosis were evaluated over a ten-year period. Magnetic resonance imaging of the central nervous system (brainstem and spinal cord) was performed for specific patients, on the basis of the presence of selected indicators determined from the clinical history, physical examination, and plain radiographic examination of the spine. The medical records were reviewed to determine the specific indicators, the results of the imaging studies, and the subsequent treatment. RESULTS Magnetic resonance imaging was ordered for 274 (21%) of the 1280 children who were evaluated. Abnormal findings were seen in twenty-seven (10%) of the 274 patients who underwent imaging, or 2% of the entire cohort. The most valuable single indicator of an abnormal finding on magnetic resonance imaging was absence of thoracic apical segment lordosis: eight of thirty-nine patients with that indicator had an abnormal finding on magnetic resonance imaging. The optimal diagnostic yield for a single category of indicators occurred when an atypical curve pattern was the only indicator: six of fifty-eight patients in whom this was the case had an abnormal finding on magnetic resonance imaging. None of the twenty children in whom pain was the only indicator category had an abnormal imaging study. The optimal diagnostic yield occurred when both an atypical curve pattern and neurological indicators were present: thirteen (25%) of fifty-three patients in whom this was the case had an abnormal finding on magnetic resonance imaging. Thirteen of the twenty-seven patients received surgical treatment for the abnormality of the central nervous system revealed by the imaging. CONCLUSIONS The correct use of diagnostic tests is an important component of effective medical practice. An abnormality of the central nervous system is present in approximately 10% of patients with presumed adolescent idiopathic scoliosis in whom only subtle abnormalities are identified on the basis of the clinical history, physical examination, or radiographic examination. Knowledge of the diagnostic value of the specific clinical indicators, considered individually and in combination, can help the clinician to determine more effectively when advanced imaging of the central nervous system should be performed.

Voluntary (normal) versus obligatory (cerebral palsy) toe-walking in children: a kinematic, kinetic, and electromyographic analysis.

Surgical management of toe-walking gait in children with cerebral palsy currently favors simultaneous, multilevel soft-tissue and bony interventions. Formulation of such a surgical plan is based on our ability to determine which of the gait deviations present are primary and which are secondary or compensatory. To evaluate this issue further, 32 normal children, walking normally and voluntarily toe-walking, were compared to 15 children with cerebral palsy walking in an obligatory toe-walking gait pattern. Computer-based analysis of gait was performed for each child, including time-distance, kinematic, kinetic, and electromyographic analyses. Significant deviations common to both normal and cerebral palsy toe-walking groups were determined to be due, at least in part, to the biomechanical constraints associated with a toe-walking gait pattern. Deviations unique to the cerebral palsy group were thought to represent primary gait deviations related to the underlying injury to the central nervous system. This study identifies the need to develop more sophisticated techniques of data collection and analysis and supports the inclusion of more varied and demanding functional activities for distinguishing between primary and secondary gait deviations in children with cerebral palsy.

Assessment of femoral anteversion in children with cerebral palsy: Accuracy of the trochanteric prominence angle test

Clinical assessment of femoral anteversion (FA) in children with cerebral palsy (CP) is frequently determined by the trochanteric prominence angle test (TPAT). Limited three-dimensional volumetric imaging by axial tomography of the femur was performed before surgery for 35 hips in 20 children with CP. The TPAT was performed before the imaging study for 31 hips in 18 children. The TPAT angle was within 10° of the FA as determined from the computed tomography scans (Murphy technique) for 17 femurs (55%). The most prominent portion of the greater trochanter was located anterior to the femoral neck axis (mean 27°, range 0°–52°) on the three-dimensional images in 34 of 35 hips. A simulated TPAT, measured from the imaging studies, consistently underestimated the FA as determined by the Murphy technique (mean 10°, range 0°–18°). Accurate clinical assessment of FA by the TPAT in children with CP presumes that the prominence of the greater trochanter lies perpendicular to the axis of the femoral neck. Three-dimensional imaging showed the prominence to be anterior, to a variable degree, to the femoral neck axis, which in addition to clinical factors such as obesity compromises the accuracy of this clinical maneuver.

A dynamic biomechanical analysis of the etiology of adolescent tibia vara.

Biomechanical overload of the proximal tibial physis due to static varus alignment and excessive body weight has been implicated in the etiology of infantile tibia vara. Whether a similar pathophysiologic process applies to adolescent tibia vara is controversial, with poor consensus concerning the nature and significance of static knee alignment early in the course of the disease. This study examines the hypothesis that dynamic gait deviations to compensate for increased thigh girth associated with obesity (fat-thigh gait) could result in increased loading of the medial compartment of the knee during the gait cycle. Three-dimensional motion analysis was used to identify the kinematic/kinetic profile associated with fat-thigh gait. Gait deviations identified were dynamic stance-limb knee varus, increased stance-limb knee rotation, and swing-limb circumduction. Pathologic compressive forces were generated in an anthropometric model by using recorded fat-thigh gait deviations and clinically appropriate excessive body weight. This analysis supports the clinical observation that underlying static varus malalignment of the knee is not a prerequisite for the development of adolescent tibia vara and illustrates the significance of dynamic gait deviations when considering knee-joint loading.