Tishya A. L. Wren

Low‐Level, High‐Frequency Mechanical Signals Enhance Musculoskeletal Development of Young Women With Low BMD

The potential for brief periods of low‐magnitude, high‐frequency mechanical signals to enhance the musculoskeletal system was evaluated in young women with low BMD. Twelve months of this noninvasive signal, induced as whole body vibration for at least 2 minutes each day, increased bone and muscle mass in the axial skeleton and lower extremities compared with controls.

Mechanical properties of the human achilles tendon

OBJECTIVE To determine whether the human Achilles tendon has higher material properties than other tendons and to test for strain rate sensitivity of the tendon. DESIGN Mechanical testing of excised tendons. BACKGROUND While the human Achilles tendon appears to experience higher in vivo stresses than other tendons, it is not known how the Achilles tendons material properties compare with the properties of other tendons. METHODS Modulus, failure stress, and failure strain were measured for excised human Achilles tendons loaded at strain rates of 1% s(-1) and 10% s(-1). Paired t-tests were used to examine strain rate effects, and average properties from grouped data were used to compare the Achilles tendons properties with properties reported in the literature for other tendons. RESULTS Failure stress and failure strain were higher at the faster strain rate, but no significant difference in modulus was observed. At the 1% s(-1)rate, the mean modulus and failure stress were 816 MPa (SD, 218) and 71 MPa (SD, 17), respectively. The failure strain was 12.8% (SD, 1.7) for the bone-tendon complex and 7.5% (SD, 1.1) for the tendon substance. At the 10% s(-1) rate, the mean modulus and failure stress were 822 MPa (SD, 211) and 86 MPa (SD, 24), respectively. The mean failure strain was 16.1% (SD, 3.6) for the bone-tendon complex and 9.9% (SD, 1.9) for the tendon substance. These properties fall within the range of properties reported in the literature for other tendons. CONCLUSIONS The material properties of the human Achilles tendon measured in this study are similar to the properties of other tendons reported in the literature despite higher stresses imposed on the Achilles tendon in vivo.

Prevalence of specific gait abnormalities in children with cerebral palsy: influence of cerebral palsy subtype, age, and previous surgery.

The authors retrospectively reviewed a series of 492 consecutive cerebral palsy patients undergoing computerized motion analysis. The prevalence of 14 specific gait abnormalities was evaluated and compared based on involvement (hemiplegia, diplegia, or quadriplegia), age, and history of previous surgery (lower extremity orthopaedic surgery or rhizotomy). Stiff knee in swing, equinus, and intoeing were all seen in more than 50% of the subjects in each of the hemiplegic, diplegic, and quadriplegic groups. Increased hip flexion and crouch were also present in more than 50% of the subjects in the diplegic and quadriplegic groups, and hip adduction occurred in more than 50% of the quadriplegic subjects. The likelihood of having stiff knee in swing, out-toeing, calcaneus deformity, and crouch increased with prior surgery. The likelihood of having rotational malalignment of the leg (internal hip rotation with out-toeing), calcaneus, out-toeing, varus and valgus foot deformities, and hip internal rotation increased with age. These findings provide important information for counseling ambulatory children with cerebral palsy and their families.

Cerebral palsy: clinical care and neurological rehabilitation

Cerebral palsy (CP) is defined as motor impairment that limits activity, and is attributed to non-progressive disturbances during brain development in fetuses or infants. The motor disorders of CP are frequently accompanied by impaired cognition, communication, and sensory perception, behavioural abnormalities, seizure disorders, or a combination of these features. CP is thought to affect three to four individuals per 1000 of the general population. The incidence, prevalence, and most common causes of CP have varied over time because of changes in prenatal and paediatric care. Medical management of children and adults involves care from primary-care physicians with input from specialists in neurology, orthopaedics, and rehabilitation medicine. Physicians should also work in conjunction with rehabilitation therapists, educators, nurses, social care providers, and schoolteachers. The focus of rehabilitation treatment has recently shifted to neurological rehabilitation in response to increasing evidence for neuroplasticity. This approach aims to improve development and function by capitalising on the innate capacity of the brain to change and adapt throughout the patients life. As the life expectancy of individuals with CP approaches that of the general population, therapies must be developed that address the needs of adults ageing with disability.

Effects of Creep and Cyclic Loading on the Mechanical Properties and Failure of Human Achilles Tendons

AbstractThe Achilles tendon is one of the most frequently injured tendons in humans, and yet the mechanisms underlying its injury are not well understood. This study examines the ex vivo mechanical behavior of excised human Achilles tendons to elucidate the relationships between mechanical loading and Achilles tendon injury. Eighteen tendons underwent creep testing at constant stresses from 35 to 75 MPa. Another 25 tendons underwent sinusoidal cyclic loading at 1 Hz between a minimum stress of 10 MPa and maximum stresses of 30–80 MPa. For the creep specimens, there was no significant relationship between applied stress and time to failure, but time to failure decreased exponentially with increasing initial strain (strain when target stress is first reached) and decreasing failure strain. For the cyclically loaded specimens, secant modulus decreased and cyclic energy dissipation increased over time. Time and cycles to failure decreased exponentially with increasing applied stress, increasing initial strain (peak strain from first loading cycle), and decreasing failure strain. For both creep and cyclic loading, initial strain was the best predictor of time or cycles to failure, supporting the hypothesis that strain is the primary mechanical parameter governing tendon damage accumulation and injury. The cyclically loaded specimens failed faster than would be expected if only time-dependent damage occurred, suggesting that repetitive loading also contributes to Achilles tendon injuries.

Three-Point Technique of Fat Quantification of Muscle Tissue as a Marker of Disease Progression in Duchenne Muscular Dystrophy: Preliminary Study

OBJECTIVE Clinical trials involving patients with Duchenne muscular dystrophy are hindered by the lack of suitable objective end points. The purpose of this study was to examine whether muscle lipid infiltration measured with the three-point Dixon MRI technique has value as a marker of disease severity. SUBJECTS AND METHODS Disease severity in nine boys (mean age, 8.6 +/- 2.7 years) with Duchenne muscular dystrophy was determined with the functional ability scale of Brooke and associates. Functional scores were compared with strength measurements obtained by manual testing of muscles of the lower extremities, knee extensor strength measured with an isokinetic dynamometer, and muscle fat percentage in the quadriceps and hamstrings determined with the three-point Dixon MRI technique. RESULTS MRI measurements of fat infiltration had stronger correlation (p < 0.05) with functional grade than did measurements obtained with manual muscle testing (p = 0.07) or quantitative strength measured with the isokinetic dynamometer (p = 0.54). Muscle fat percentage did not correlate with strength measurements from manual or dynamometer muscle testing but increased with age in subjects with Duchenne muscular dystrophy. CONCLUSION Muscle adiposity values obtained with three-point Dixon MRI are accurate in assessment of disease severity in patients with Duchenne muscular dystrophy. Because they are not influenced by patient effort or examiner variability, these measurements are more objective and reproducible than measurements of muscle strength.

Efficacy of clinical gait analysis: A systematic review

The aim of this systematic review was to evaluate and summarize the current evidence base related to the clinical efficacy of gait analysis. A literature review was conducted to identify references related to human gait analysis published between January 2000 and September 2009 plus relevant older references. The references were assessed independently by four reviewers using a hierarchical model of efficacy adapted for gait analysis, and final scores were agreed upon by at least three of the four reviewers. 1528 references were identified relating to human instrumented gait analysis. Of these, 116 original articles addressed technical accuracy efficacy, 89 addressed diagnostic accuracy efficacy, 11 addressed diagnostic thinking and treatment efficacy, seven addressed patient outcomes efficacy, and one addressed societal efficacy, with some of the articles addressing multiple levels of efficacy. This body of literature provides strong evidence for the technical, diagnostic accuracy, diagnostic thinking and treatment efficacy of gait analysis. The existing evidence also indicates efficacy at the higher levels of patient outcomes and societal cost-effectiveness, but this evidence is more sparse and does not include any randomized controlled trials. Thus, the current evidence supports the clinical efficacy of gait analysis, particularly at the lower levels of efficacy, but additional research is needed to strengthen the evidence base at the higher levels of efficacy.

Vitamin D Status and Its Relation to Muscle Mass and Muscle Fat in Young Women

CONTEXT Vitamin D insufficiency has now reached epidemic proportions and has been linked to increased body fat and decreased muscle strength. Whether vitamin D insufficiency is also related to adipose tissue infiltration in muscle is not known. OBJECTIVE The objective of the study was to examine the relationship between serum 25-hydroxyvitamin D (25OHD) and the degree of fat infiltration in muscle. DESIGN This was a cross-sectional study. OUTCOME MEASURES AND SUBJECTS: Measures were anthropometric measures, serum 25OHD radioimmunoassay values, and computed tomography (CT) values of fat, muscle mass, and percent muscle fat in 90 postpubertal females, aged 16-22 yr, residing in California. RESULTS Approximately 59% of subjects were 25OHD insufficient (< or = 29 ng/ml), of which 24% were deficient (< or = 20 ng/ml), whereas 41% were sufficient (> or = 30 ng/ml). A strong negative relationship was present between serum 25OHD and CT measures of percent muscle fat (r = -0.37; P < 0.001). In contrast, no relationship was observed between circulating 25OHD concentrations and CT measures of thigh muscle area (r = 0.16; P = 0.14). Multiple regression analysis indicated that the relation between 25OHD and muscle adiposity was independent of body mass or CT measures of sc and visceral fat. Percent muscle fat was significantly lower in women with normal serum 25OHD concentrations than in women with insufficient levels and deficient levels (3.15 +/- 1.4 vs. 3.90 +/- 1.9; P = 0.038). CONCLUSIONS We found that vitamin D insufficiency is associated with increased fat infiltration in muscle in healthy young women.

Botulinum Toxin as an Adjunct to Serial Casting Treatment in Children with Cerebral Palsy

BACKGROUND Although botulinum toxin A is frequently used to augment serial casting in the treatment of soft-tissue contractures in children with cerebral palsy, its effectiveness for this purpose has not been evaluated. The purpose of the present study was to determine whether botulinum toxin A injection increases the efficacy of serial casting. METHODS A prospective, randomized trial was undertaken to compare serial casting only with serial casting combined with botulinum toxin A (Botox) injection for the treatment of ankle equinus contractures in twenty-three children with cerebral palsy. Range-of-motion testing, spasticity assessment, and computerized gait analysis were performed as long as twelve months after treatment. RESULTS There was no difference between the groups with regard to the duration of casting required to correct the equinus contracture. Both groups maintained a significant improvement in passive ankle dorsiflexion throughout the follow-up period, although the group managed with casting and Botox had a significant loss of dorsiflexion when the values at six, nine, and twelve months were compared with the value at three months. Peak dorsiflexion during the stance and swing phases was significantly improved in both groups at three months but only in the group managed with casting alone at twelve months. Plantar flexor spasticity was significantly decreased at three months in both groups, but it was significantly decreased at six, nine, and twelve months only in the group managed with casting alone. Spasticity was significantly greater in the group managed with casting and Botox than it was in the group managed with casting only at six, nine, and twelve months. CONCLUSIONS The present study demonstrates the efficacy of serial casting in the treatment of equinus contractures in children with cerebral palsy who are able to walk. Contrary to our hypothesis, the addition of botulinum toxin A to a serial casting regimen led to earlier recurrence of spasticity, contracture, and equinus during gait. The results of the present study suggest that botulinum toxin combined with serial casting for the treatment of fixed contractures will lead to a recurrence of plantar flexor spasticity and equinus contracture by six months in this patient population. While previous research has indicated that the injection of botulinum toxin A is superior to casting for the treatment of dynamic equinus, the present study suggests that serial casting alone is preferable for the treatment of fixed equinus contractures in children with cerebral palsy.

Age at Onset of Puberty Predicts Bone Mass in Young Adulthood

OBJECTIVE To determine whether the commencement and length of puberty influences dual x-ray absorptiometry (DXA) values of bone mineral content (BMC) and bone mineral density (BMD) in the axial and appendicular skeleton at skeletal maturity. STUDY DESIGN From the Bone Mineral Density in Childhood Study, we identified children who began puberty and completed sexual and skeletal development and examined whether the timing and length of puberty influence DXA values of BMC and BMD at skeletal maturity. RESULTS A total of 78 girls and 85 boys began puberty and completed skeletal maturity; 4.4 ± 0.8 and 4.5 ± 0.8 years later, respectively. Multiple linear regression analyses indicated that the age of onset of puberty was a strong negative predictor of DXA bone measurements at skeletal maturity, independent of bone values at the beginning of puberty, and the length of puberty. This negative relation was observed for all BMC and BMD measurements at all skeletal sites, in both boys and girls (all P < .0001). In contrast, length of puberty had no relation to any measures of bone. CONCLUSIONS In healthy adolescent males and females, bone mass and bone density at skeletal maturity are inversely related to the timing of puberty.