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Biomedical subjects

Karim M Khan

Publications and source records attributed to Karim M Khan.

At least 19 recordsLinked to original sources
PubMed2007

Is a school-based physical activity intervention effective for increasing tibial bone strength in boys and girls?

UNLABELLED: This 16-month randomized, controlled school-based study compared change in tibial bone strength between 281 boys and girls participating in a daily program of physical activity (Action Schools! BC) and 129 same-sex controls. The simple, pragmatic intervention increased distal tibia bone strength in prepubertal boys; it had no effect in early pubertal boys or pre or early pubertal girls. INTRODUCTION: Numerous school-based exercise interventions have proven effective for enhancing BMC, but none have used pQCT to evaluate the effects of increased loading on bone strength during growth. Thus, our aim was to determine whether a daily program of physical activity, Action Schools! BC (AS! BC) would improve tibial bone strength in boys and girls who were pre- (Tanner stage 1) or early pubertal (Tanner stage 2 or 3) at baseline. MATERIALS AND METHODS: Ten schools were randomized to intervention (INT, 7 schools) or control (CON, 3 schools). The bone-loading component of AS! BC included a daily jumping program (Bounce at the Bell) plus 15 minutes/day of classroom physical activity in addition to regular physical education. We used pQCT to compare 16-month change in bone strength index (BSI, mg2/mm4) at the distal tibia (8% site) and polar strength strain index (SSIp, mm3) at the tibial midshaft (50% site) in 281 boys and girls participating in AS! BC and 129 same-sex controls. We used a linear mixed effects model to analyze our data. RESULTS: Children were 10.2+/-0.6 years at baseline. Intervention boys tended to have a greater increase in BSI (+774.6 mg2/mm4; 95% CI: 672.7, 876.4) than CON boys (+650.9 mg2/mm4; 95% CI: 496.4, 805.4), but the difference was only significant in prepubertal boys (p=0.03 for group x maturity interaction). Intervention boys also tended to have a greater increase in SSIp (+198.6 mm3; 95% CI: 182.9, 214.3) than CON boys (+177.1 mm3; 95% CI: 153.5, 200.7). Change in BSI and SSIp was similar between CON and INT girls. CONCLUSIONS: Our findings suggest that a simple, pragmatic program of daily activity enhances bone strength at the distal tibia in prepubertal boys. The precise exercise prescription needed to elicit a similar response in more mature boys or in girls might be best addressed in a dose-response trial.

Bone Density↗
PubMed2006

Regional trabecular morphology assessed by micro-CT is correlated with failure of aged thoracic vertebrae under a posteroanterior load and may determine the site of fracture.

INTRODUCTION: Spinal mobilization is commonly used in the treatment of patients with back pain, including individuals with osteoporosis. Previous data indicated that traditional predictors of skeletal failure-lateral or anteroposterior bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) or geometry of the spinous process or vertebral body-do not predict failure load during posteroanterior spinal mobilization. Morphological differences and inhomogeneities in BMD may have important effects on vertebral strength but integral BMD values by DXA cannot reflect these potentially important differences. We investigated the determinants of spinal fracture using muCT. MATERIALS AND METHODS: We measured failure load and failure site in 11 T5-8 cadaveric specimens (mean age 78 years) when a posteroanterior load was applied at the spinous process of T6 using a servohydraulic material testing machine. Radiography and CT scan were used to verify failure site. We observed no damage to the adjacent T7 vertebrae following the T6 posteroanterior failure test. The T7 vertebrae were sectioned to produce regional samples of the spinous process, the lamina and a vertebral body core. Each sample was scanned with muCT to measure bone microarchitectural parameters. We segmented and analysed four trabecular regions (spinous process base and middle, central lamina and central vertebral body). We used one-way repeated measures ANOVA to compare regions and computed Pearson correlations to assess the relation between PA failure load of T6 and the morphological parameters of T7. RESULTS: The BV/TV at the base or middle of the T7 spinous process (fracture sites), Tb.N and Tb.Th at the base were significantly correlated with posteroanterior failure load of T6 (BV/TV base: r=0.74, p=0.01; BV/TV middle: r=0.73, p=0.01; Tb.N base: r=0.64, p=0.03; Tb.Th base: r=0.65, p=0.03). The Tb.Th of the lamina was significantly greater than Tb.Th of the spinous process base (p=0.002). CONCLUSIONS: Whereas previous data indicated that BMD by DXA was not a good predictor of posteroanterior failure load, regional BV/TV of the spinous process base and middle regions, the sites of fracture, are correlated with posteroanterior failure load. Trabecular thickness differed significantly between the base of the spinous process and the lamina, and may have influenced the site of fracture.

Aged↗
PubMed2006

Falls-related self-efficacy is independently associated with balance and mobility in older women with low bone mass.

BACKGROUND: It is currently unknown whether falling is independently associated with measures of balance and mobility in older adults after accounting for relevant physiological functions. This cross-sectional study assessed the independent association of falls-related self-efficacy to balance and mobility after accounting for age, current physical activity, and performances in relevant physiological domains in 98 older women, aged 75-86 years, with low bone mass. METHODS: Falls-related self-efficacy was assessed by the Activities-Specific Balance Confidence Scale (ABC Scale). Measures of balance and mobility included the 13-item Community Balance and Mobility Scale (CB & M Scale) and gait speed under two conditions: normal-paced and fast-paced. Physiological assessment included postural sway, foot reaction time, dominant quadriceps and dorsiflexor strength, proprioception, tactile sensitivity, edge contrast sensitivity, and visual acuity. RESULTS: Falls-related self-efficacy was independently associated with both balance and mobility after accounting for age, current physical activity level, and performances in relevant physiological domains. Based on the standardized beta coefficients, the ABC Scale score was more associated with measures of balance and mobility than measures of physiological function. CONCLUSION: These results highlight the independent association of falls-related self-efficacy with physical performance in older women with low bone mass. Thus, clinicians may need to consider falls-related self-efficacy when assessing and treating balance and mobility in this population, and falls-related self-efficacy may be useful as a screening tool to identify those persons with impaired balance and mobility.

Accidental Falls↗
PubMed2005

Tarsal navicular stress injury: long-term outcome and clinicoradiological correlation using both computed tomography and magnetic resonance imaging.

BACKGROUND: Tarsal navicular stress fracture is a condition that has curtailed many athletic careers. Management protocols remain varied and somewhat controversial. HYPOTHESES: (1) Clinical practice does not mirror the recommendations reported from previous case series. (2) Clinical outcome is poor when navicular stress fracture is managed in a variety of ways. (3) Imaging does not correlate strongly with clinical status at long-term follow-up after navicular stress fracture. STUDY DESIGN: Case series (prognosis); Level of evidence, 4. METHODS: From a computer registry, we identified patients who had attended a university sports medicine center between 1996 and 2002 and whose final diagnosis was navicular stress fracture (n = 11) or navicular stress reaction (n = 9). All patients had provided demographic and clinical data at their original evaluation, and all had undergone bone scans and computed tomographic imaging. These data were extracted by chart review. Follow-up clinical and imaging assessments took place a median of 3.7 years later (range, 1-15.7 years). At these assessments, we administered a questionnaire, performed a structured physician examination (blinded to other data), scanned both feet with computed tomography, and obtained magnetic resonance images of the affected foot. RESULTS: Only 2 of 11 patients (18%) with navicular stress fractures received the literature-recommended treatment of at least 6 weeks' nonweightbearing cast immobilization. Of these 11 patients, only 6 (55%) returned to sports at their previous level. Only 3 patients with navicular stress fractures regained normal imaging appearance at follow-up. Pain score, stiffness, sporting success, current sporting involvement, and recurrence/time to recurrence were not statistically associated with computed tomographic or magnetic resonance imaging parameters. Of 9 patients with navicular stress reactions, 7 developed clinical and radiological features of navicular stress fracture, but 6 of 9 patients (67%) returned successfully to sports. CONCLUSIONS: Contemporary management of navicular stress fracture differs from that recommended in the literature. This stress fracture prevented almost half of the participants in this study from returning to sports at their previous level. Imaging parameters do not correlate with the clinical assessment of a patient at long-term follow-up of navicular stress fracture.

Adolescent↗
PubMed2005

Emergency department fall-related presentations do not trigger fall risk assessment: a gap in care of high-risk outpatient fallers.

We wanted to determine whether women aged 70 years and older, who presented to the emergency department (ED) with a fall and injury, received guideline care within 18 months of presentation. Women aged 70 years and older who presented to the ED with a fall were recorded prospectively from August 1, 2001 to May 1, 2002 (n=226). Structured telephone interviews were performed 18 months after the ED fall to obtain details of patient management (n=63). The most frequently reported referral was to the family physician (32%) and to physiotherapy (24%). We concluded that most older women who presented to the ED with a fall did not appear to be receiving current guideline care. We propose that future research use a prospective study design to assess whether or not guideline care is being delivered by a variety of health care providers after the patients leave the ED.

Accidental Falls↗
PubMed2005

IGF-I activates PKB and prevents anoxic apoptosis in Achilles tendon cells.

Anoxia and apoptosis are both implicated in chronic tendon pathology, however the influence of anoxia on the viability of tendon cells is not known. The objectives of the current study were to (i) investigate the effect of oxygen withdrawal on the viability of porcine Achilles tendon cells (ATCs), and (ii) examine the ability of IGF-I, a factor with known regenerative properties in tendon, to prevent ATC death. Cultured ATCs were enclosed in an anaerobic chamber. The mechanism of cell death was examined by flow cytometry of ATCs double labeled with Annexin-V and propidium iodide (PI). Caspase activity was determined by a fluorometric assay, and nuclear morphology was examined by Hoechst staining. The cell death induced by anoxia was time-dependent, and was characterized by phosphatidylserine exposure on the outer membrane, caspase activation and DNA fragmentation. Death was inhibited by the addition of IGF-I in a dose-dependent manner. The ability of IGF-I to activate the pro-survival PKB pathway in ATCs was inhibited by LY294002, indicating the importance of PI3K in the response of ATCs to IGF-I. These data suggest that cell death induced by lack of oxygen is predominantly apoptotic and can be prevented by pro-survival IGF-I signaling. This mechanism may contribute to the beneficial effect of IGF-I on tendon.

Achilles Tendon↗
PubMed2005

Maturity- and sex-related changes in tibial bone geometry, strength and bone-muscle strength indices during growth: a 20-month pQCT study.

During growth, bone strength is conferred through subtle adaptations in bone mass and geometry in response to muscle forces. Few studies have examined the changes in bone geometry, strength and the bone-muscle strength relationship across maturity in boys and girls. Our aims were to describe (i) 20-month changes in bone geometry and strength at the tibial midshaft across three maturity groups of boys and girls, (ii) differences in these adaptations between sexes at the same approximate level of maturity and (iii) the bone-muscle strength relationship across maturity groups of boys and girls and between sexes. We used peripheral quantitative computed tomography (pQCT, Stratec XCT-2000) to measure change in total bone cross-sectional area (ToA, mm(2)), cortical area (CoA, mm(2)), average cortical thickness (C.Th., mm), section modulus (mm(3)) and muscle cross-sectional area (mm(2)) at the tibial midshaft (50% site) in 128 EARLY-, PERI- and POST-pubertal girls (n = 69, 11.9 +/- 0.6 years) and boys (n = 59, 12.0 +/- 0.6 years) across 20 months. We also calculated two bone-muscle strength indices (BMSI) for compression (CoA/MCSA) and bending [strength index/MCSA; where strength index = Z / (tibial length / 2)]. EARLY boys and girls had smaller ToA at baseline than same sex PERI or POST participants. There were no sex differences in ToA or CoA at baseline; however, boys increased both parameters significantly more than girls in every maturity group (8.5-11.1%, P < 0.01). These changes in bone geometry conferred greater gains in bone strength for boys compared with girls in each maturity group (13.8-15.6%, P < 0.01). Baseline BMSIs did not differ between sexes for EARLY and PERI groups, whereas BMSIs were significantly higher for POST boys compared with POST girls (P < 0.05). BMSIs decreased for EARLY and PERI girls (-7.4-(-1.1%)) whereas the ratios remained stable for EARLY and PERI boys (-0.6-2.5%). This sex difference in BMSI change was due to a relatively greater increase in CoA among EARLY and PERI boys compared with same-maturity girls. BMSIs remained stable in POST girls and decreased in POST boys due to relatively greater gains in MCSA. This study provides novel longitudinal descriptions of the maturity- and sex-specific changes in bone geometry, strength and bone-muscle strength indices.

Adolescent↗
PubMed2005

Examining bone surfaces across puberty: a 20-month pQCT trial.

UNLABELLED: This follow-up study assessed sex differences in cortical bone growth at the tibial midshaft across puberty. In both sexes, periosteal apposition dominated over endosteal resorption. Boys had a greater magnitude of change at both surfaces, and thus, a greater increase in bone size across puberty. Relative increase in cortical bone area was similar between sexes. INTRODUCTION: Generally, sex differences in bone size become most evident as puberty progresses. This was thought to be caused, in part, by greater periosteal apposition in boys, whereas endosteal apposition prevailed in girls. However, this premise is based on evidence from cross-sectional studies and planar measurement techniques. Thus, our aim was to prospectively evaluate sex-specific changes in cortical bone area across puberty. MATERIALS AND METHODS: We used pQCT to assess the tibial midshaft (50% site) at baseline and final (20 months) in girls (N = 68) and boys (N = 60) across early-, peri-, and postpuberty. We report total bone cross-sectional area (ToA, mm2), cortical area (CoA, mm2), marrow cavity area (CavA, mm2), and CoA/ToA ratio. RESULTS: Children were a mean age of 11.9 +/- 0.6 (SD) years at baseline. At the tibia, CoA ranged from 230 +/- 44, 261 +/- 50, and 258 +/- 46 in early-, peri-, and postpubertal girls. In boys, comparable values were 223 +/- 36 (early), 264 +/- 38 (peri), and 281 +/- 77 (postpubertal). There was no sex difference for ToA or CoA at baseline. Increase in ToA and CoA was, on average, 10% greater for boys than girls across maturity groups. The area of the marrow cavity increased in all groups, but with considerable variability. The increase in CavA was significantly less for girls than boys in the early- and postpubertal groups. Change in CoA/ToA was similar between sexes across puberty. CONCLUSION: Both sexes showed a similar pattern of change in CoA at the tibial midshaft, where periosteal apposition dominated over endosteal resorption. Boys showed a greater magnitude of change at both surfaces, and thus, showed a greater increase in bone size across puberty. The relative increase in cortical area was similar between sexes. These pQCT findings provide no evidence for endosteal apposition in postmenarchal girls.

Adolescent↗
PubMed2005

Both resistance and agility training reduce back pain and improve health-related quality of life in older women with low bone mass.

The purpose of the study was to compare the effects of three different types of group-based exercise programs (resistance training, agility training and general stretching) on back pain and health-related quality of life in older (aged 75-85 years) community-dwelling women with low bone mass (i.e., osteopenia or osteoporosis). The design was a 25-week randomized controlled trial. Participating were 98 community-dwelling women with low bone mass between the ages of 75 to 85 years old. We assessed back pain and its related disability and health-related quality of life. All three types of group-based exercise programs significantly reduced back pain and its related disabilities, but only resistance and agility training significantly improved health-related quality of life in community-dwelling older women with low bone mass. Baseline physical activity level and class attendance were significant predictors of change in health-related quality of life. Change in back pain and its related disabilities after 25 weeks of exercise intervention was significantly correlated with change in health-related quality of life and changes in the domains of pain and physical function. Resistance and agility training significantly enhanced health-related quality of life and may have done so by increasing social interactions and support, enhancing self-efficacy of physical abilities and modifying the experience of back pain. These data provide valuable insight into the specifics of exercise prescription for older women with low bone mass. Future studies may wish to use individualized quality of life measures to further delineate the effects of different types of exercise on quality of life in older adults with low bone mass.

Aged↗
PubMed2005

Posteroanterior stiffness predicts sagittal plane midthoracic range of motion and three-dimensional flexibility in cadaveric spine segments.

BACKGROUND: Spinal joint mobilization is a mainstay of clinical assessment of individuals with back pain. The clinician manually assesses stiffness and joint motion relative to segments above and below. Although clinical theory suggests that manually performed techniques can predict or detect intervertebral motion, this hypothesis remains untested. METHODS: Using a precision opto-electronic camera system and a custom spine testing machine, we measured intervertebral range of motion, neutral zone motion and three-dimensional flexibility in eight T5-T8 cadaveric specimens (mean age=81 years). We then measured stiffness when a cyclic posteroanterior load was applied at the spinous process of T6 using a servohydraulic material testing machine (Instron 8874), simulating the posteroanterior spinal mobilization technique. FINDINGs. There was a strong significant inverse relationship between stiffness during cyclic posteroanterior loading of T6 and flexion or extension range of motion of T6 relative to T7 (r=-0.88, P<0.01, extension; r=-0.81, P=0.01, flexion), and T6-T7 flexibility in all six directions. INTERPRETATION: Stiffness during simulated central cyclic posteroanterior mobilization in the cadaveric midthoracic spine is inversely correlated with flexion and extension range of motion and three-dimensional flexibility at the level at which the technique is applied. These findings provide biomechanical support for the inclusion of specific joint mobilization in the assessment of older adults with back pain.

Aged↗
PubMed2005

Achilles tendon disorders: etiology and epidemiology.

The Achilles tendon is the strongest tendon in the human body. Because most Achilles tendon injuries take place in sports and there has been a general increase in popularity of sporting activities, the number and incidence of the Achilles tendon overuse injuries and complete, spontaneous ruptures has increased in the industrialized countries during the last decades. The most common clinical diagnosis of Achilles overuse injuries is tendinopathy. The basic etiology of the Achilles tendinopathy is known to be multi-factorial. Although histopathologic studies have shown that ruptured Achilles tendons have clear degenerative changes before the rupture, many Achilles tendon ruptures take place suddenly without any preceding signs or symptoms.

Achilles Tendon↗
PubMed2005

Physiotherapy and osteoporosis: practice behaviors and clinicians' perceptions--a survey.

Physiotherapists typically use a variety of modes to treat their clients, including manual therapy. The literature cautions against the use of manual therapy in individuals with osteoporosis, (Musculoskeletal Manipulation: Evaluation of the Scientific Evidence, Charles C Thomas Publisher, Springfield, IL; Common Vertebral Joint Problems, 2nd Edition, Churchill Livingstone, New York; Maitland's Vertebral Manipulation, 6th Edition, Butterworth-Heinemann, Boston; Br. J. Sports Med. 37 (2003) 195-196) yet clinical experience (Br. J. Sports Med. 37 (2003) 195-196) and published cases (J. Manip. Physiol. Ther. 15(7) (1992) 450-454) suggest that these techniques are still being used by at least some clinicians. The purpose of this study was to measure the most common treatment modes used by a random sample of physiotherapists practicing in the province of British Columbia (BC) in the treatment of individuals with osteoporosis. To assess whether physiotherapists in BC have concerns about the use of manual therapy in individuals with osteoporosis, particularly whether physiotherapists have concerns about fracture as a complication of treatment. This cross-sectional study of 171 physiotherapists in BC used a questionnaire developed by the physiotherapist in the Osteoporosis Program at the BC Women's Health Centre (a part of the Children's & Women's Health Centre of BC). The response rate (67/171) was 39%. Ninety-seven per cent of respondents reported using strength exercises and postural reeducation, while 45% reported using manual therapy in this population. Ninety-one per cent of respondents reported having concerns about the use of manual therapy. Vertebral fracture and rib fracture were the most commonly reported concerns. These findings suggest that most physiotherapists practicing in BC, Canada use evidence-based methods (i.e. strength training) when treating individuals with osteoporosis, a large number use manual therapy, and most have concerns about its use. Physiotherapists are most concerned about fractures, in particular vertebral fracture, but injury to other musculoskeletal tissues is also of concern. Studies of safety and effectiveness of manual therapy in this population are needed to guide clinical practice.

Attitude of Health Personnel↗
PubMed2005

The beneficial effects of group-based exercises on fall risk profile and physical activity persist 1 year postintervention in older women with low bone mass: follow-up after withdrawal of exercise.

OBJECTIVES: To determine whether exercise-induced reductions in fall risk are maintained in older women 1 year after the cessation of three types of interventions--resistance training, agility training, and general stretching. DESIGN: One-year observational study. SETTING: Community. PARTICIPANTS: Ninety-eight women aged 75 to 85 with low bone mass. MEASUREMENTS: Primary outcome measure was fall risk, measured using the Physiological Profile Assessment tool. Secondary outcome measures were current physical activity level, assessed using the Physical Activity Scale for the Elderly, and formal exercise participation, assessed using an interview. RESULTS: At the end of the follow-up, the fall risk of former participants of all three exercise programs was maintained (i.e., still reduced) from trial completion. Mean fall risk value at the end of follow-up was 43.3% lower than mean baseline value in former participants of the resistance-training group, 40.1% lower in the agility-training group, and 37.4% lower in the general stretching group. Physical activity levels were also maintained from trial completion. Specifically, there was a 3.8% increase in physical activity from baseline for the resistance-training group, a 29.2% increase for the agility-training group, and a 37.7% increase for the general stretching group. CONCLUSION: After three types of group-based exercise programs, benefits are sustained for at least 12 months without further formal exercise intervention. Thus, these 6-month exercise interventions appeared to act as a catalyst for increasing physical activity with resultant reductions in fall risk profile that were maintained for at least 18 months in older women with low bone mass.

Accidental Falls↗