Archive of Medical Research

Income, relative income, and self-reported health in Britain 1979-2000.

We test the relative income hypothesis that an individual\’s health depends on the distribution of income in a reference group, as well as on the income of the individual. We use data on 231 208 individuals in Great Britain from 19 rounds of the General Household Survey between 1979 and 2000. Results are insensitive to the measure of self-assessed health used but the sign and significance of the effect of relative income depend on the reference group (national or regional) and the measure of relative income (Gini coefficient, absolute or proportional difference from the reference group mean, Yitzhaki absolute and proportional relative deprivation and affluence). Only one model (relative deprivation measured as income proportional to regional mean income) performs better than the model without relative income and has a positive estimated effect of absolute income on health. In this model the increase in the probability of good health from a ceteris paribus reduction in relative deprivation from the upper quartile to zero is 0.010, whereas an increase in income from the lower to the upper quartile increases the probability by 0.056. While our results provide only very weak support for the relative deprivation hypothesis, the inevitable correlation of measures of individual income and relative deprivation measured by comparing income and incomes in a reference group makes identification of the separate effects of income and relative deprivation problematic. Copyright (c) 2008 John Wiley & Sons, Ltd.

Gravelle H, Sutton M.

National Primary Care Research and Development Centre, Centre for Health Economics, University of York, York, UK.

Impact of the recall period on measuring health utilities for acute events.

The impact of healthcare interventions on health utility values is most frequently measured using a preference-based instrument. Each of the available instruments instructs the respondent to report their health status over different recall periods ranging from the current day to the past month. In an ongoing randomised controlled trial in patients with advanced HIV disease, the impact of using a preference-based instrument with a 1-week recall period vs a 1-day recall period (e.g. today) for capturing recently resolved serious adverse events was measured. The results suggest that the instrument with a 1-week recall period gave lower utility values for recently resolved events in comparison with the instrument with a 1-day recall period. A plausible interpretation of these results is that the recall period was adhered to; for example, patients ignored the impact of recently resolved events in their response if the questionnaire asked them only about their health today. While there are limitations to our study, we believe further consideration should be given to the recall period used for preference-based instruments, and future research should examine other patient groups using a single instrument with multiple recall periods. Copyright (c) 2008 John Wiley & Sons, Ltd.

Bansback N, Sun H, Guh DP, Li X, Nosyk B, Griffin S, Barnett PG, Anis AH; ON BEHALF OF THE OPTIMA TEAM.

Centre for Health Evaluation and Outcome Sciences, St. Paul\’s Hospital, Vancouver, BC, Canada.

Estimating differences between male and female physician service provision using panel data.

Using panel data, we estimate the impact of an increasing share of female physicians on the total output of Canadian physicians. A micro-econometric model is developed specifically for the Canadian context and estimated using administrative data on all Canadian physicians paid on a fee-for-service basis from 1989 to 1998. Our results suggest that female physicians systematically provide fewer services than their male counterparts for almost all specialities and provinces studied. Given that females account for an increasing share of the physician population and that female physicians provide, on average, fewer services, potentially important future reductions in total health-care service provision are likely. Copyright (c) 2008 John Wiley & Sons, Ltd.

Constant A, Léger PT.

Economist Health Policy Research Division, Health Canada, Ottawa, Ont., Canada.

Patient-specific finite element analysis of chronic contact stress exposure after intraarticular fracture of the tibial plafond.

The role of altered contact mechanics in the pathogenesis of posttraumatic osteoarthritis (PTOA) following intraarticular fracture remains poorly understood. One proposed etiology is that residual incongruities lead to altered joint contact stresses that, over time, predispose to PTOA. Prevailing joint contact stresses following surgical fracture reduction were quantified in this study using patient-specific contact finite element (FE) analysis. FE models were created for 11 ankle pairs from tibial plafond fracture patients. Both (reduced) fractured ankles and their intact contralaterals were modeled. A sequence of 13 loading instances was used to simulate the stance phase of gait. Contact stresses were summed across loadings in the simulation, weighted by resident time in the gait cycle. This chronic exposure measure, a metric of degeneration propensity, was then compared between intact and fractured ankle pairs. Intact ankles had lower peak contact stress exposures that were more uniform and centrally located. The series-average peak contact stress elevation for fractured ankles was 38% (p = 0.0015; peak elevation was 82%). Fractured ankles had less area with low contact stress exposure than intact ankles and a greater area with high exposure. Chronic contact stress overexposures (stresses exceeding a damage threshold) ranged from near zero to a high of 18 times the matched intact value. The patient-specific FE models represent substantial progress toward elucidating the relationship between altered contact stresses and the outcome of patients treated for intraarticular fractures. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Li W, Anderson DD, Goldsworthy JK, Marsh JL, Brown TD.

Department of Biomedical Engineering, The University of Iowa, 2181 Westlawn Building, Iowa City, Iowa 52242.

Changes of selenium, copper, and zinc content in hair and serum of patients with idiopathic scoliosis.

Our work aimed at extending the search for abnormalities of trace elements in patients with idiopathic scoliosis to the content of zinc (Zn), copper (Cu), and selenium (Se) in these subject\’s hair and serum. A total of 59 patients (54 girls and 4 boys) with idiopathic scoliosis, aged 13 on the average (range, 10-18 years), were examined. The degree of spine curvature deformity ranged between 12 degrees and 82 degrees . The hair of scoliotic patients under examination showed significantly increased content of zinc 263 +/- 108 microg/g (p < 0.01) and copper 46.2 +/- 37.1 microg/g (p < 0.01), and decreased content of selenium 0.194 +/- 0.114 microg/g (p < 0.01) in comparison with the control group. In scoliotic patients, the Cu/Zn ratio in hair (0.186 +/- 0.139) did not differ significantly from the values found in the probands of the control group (0.115 +/- 0.09). The Cu/Se ratio in this group of patients (254.9 +/- 215.9) was significantly higher (p < 0.001) due to a higher Cu value and a lower Se value in comparison with the controls (47.9 +/- 23.7). In comparison with controls, the serum selenium concentration in the group of scoliotic patients was significantly decreased p < 0.05 (0.74 +/- 0.13 micromol/L and 0.98 +/- 0.12 micromol/L). Various changes in the content of trace elements in biological samples taken from patients with idiopathic scoliosis are not accidental. What might bring about a shift in our knowledge is speciation of various forms of trace elements in the organism in relation to idiopathic scoliosis. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Dastych M, Cienciala J, Krbec M.

Departments of Clinical Biochemistry and Laboratory Methods, Masaryk University Medical School and Teaching Hospital Brno, Czech Republic.

Proprioception assessment in subjects with idiopathic loss of shoulder range of motion: Joint position sense and a novel proprioceptive feedback index.

We examined the effects of elevation range and plane on shoulder joint proprioception in subjects with idiopathic loss of shoulder range of motion (ROM). Joint position sense (JPS) and a novel proprioceptive feedback index (PFI), including difference magnitude and the similarity index, were used to assess proprioception. Twelve subjects (eight male, four female) with involved stiff shoulders and normal opposite shoulders were recruited from a university hospital. Subjects attempted to repeat six target positions. Target positions consisted of arm elevation in three planes (frontal, scapular, and sagittal planes) and two ranges (end/mid range). Six trials of each target position were used to determine acceptable trials for stabilization of the data, less than 5% of the cumulative mean values for at least three successive trials. The data stabilized at the sixth repetition. Compared to control shoulders, involved shoulders had enhanced proprioception during end range movements (p < 0.05). The magnitude of the repositioning error and difference magnitude decreased (1.6 degrees -3.5 degrees for repositioning error and 22.2 degrees -62.1 degrees for difference magnitude), whereas similarity index improved at end range movements compared to mid range movements (p < 0.05) in involved stiff shoulders. Results of JPS and PFI suggest that both capsuloligamentous and musculotendinous mechanoreceptors play an important role in proprioception feedback during active movements in subjects with idiopathic loss of shoulder ROM. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Yang JL, Chen S, Jan MH, Lin YF, Lin JJ.

Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan.

Manipulating the anabolic and catabolic response in bone graft remodeling: Synergism by a combination of local BMP-7 and a single systemic dosis of zoledronate.

Remodeling of a bone graft can be influenced both by anabolic substances, such as a bone morphogenic protein (BMP) and by anticatabolic substances, such as the bisphosphonates. BMPs are potent bone anabolic substances, but also boost catabolism and cause resorption. Bisphosphonates inhibit osteoclast function and can be used to postpone resorption. In the present study a combination of both drugs was explored in a rat bone chamber model. Cancellous bone grafts were treated with either BMP-7 or saline and placed in a bone chamber implanted in the proximal tibia. After 2 weeks, an injection of either zoledronate 0.1 mg/kg or saline was given subcutaneously. The rats were killed after 6 weeks, and bone ingrowth distance into the graft and graft resorption were measured by histomorphometry. BMP-7 significantly (p = 0.007) increased new bone ingrowth distance into the graft from 2.0 mm (SD = 0.98 mm) in the controls to 3.1 mm (SD = 0.93 mm). If bisphosphonate was not given, most of the newly formed and old graft bone was resorbed. A single injection of zoledronate significantly (p < 0.001) increased the trabecular volume/total volume to 40% (SD = 9%) compared to 14% (SD = 10%) in the nonbisphosphonate treated. In total, the net amount of bone increased by 400% when BMP-7 and zoledronate combined was compared to saline. A bone graft can be treated with BMP-7 to increase new bone formation and at the same time be protected against premature catabolism by a single dose of a bisphosphonate. This combination might be useful in various conditions in orthopedic reconstruction. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Harding AK, Aspenberg P, Kataoka M, Bylski D, Tägil M.

Department of Orthopedics, Lund University Hospital, SE‐221 85 Lund, Sweden.

The effect of hyaluronidase, phospholipase, lipid solvent and trypsin on the lubrication of canine flexor digitorum profundus tendon.

Although the flexor digitorum profundus (FDP) tendon\’s gliding resistance is low, the lubrication mechanism that enables this is unclear. The principal lubricants in joints, such as hyaluronic acid, phospholipids, and lubricin, a lubricating glycoprotein, are known to be present in the canine tendon. In this study, we assessed the effect of these lubricants in the tendon by measuring gliding resistance before and after their removal. Canine FDP tendons were treated with hyaluronidase, phospholipase, lipid solvent, and/or trypsin. The gliding resistance of FDP tendons significantly increased after all treatments (p < 0.05). The largest effect on gliding resistance was observed after trypsin digestion. Scanning electron microscopy and immunostaining for hyaluronic acid and lubricin were used to qualitatively assess the tendon surface after treatments. The trypsin digestion produced the most irregular surface, with many exposed collagen fibers. The results of this study suggest that phospholipids, hyaluronic acid, and protein components are all involved in maintaining the low gliding resistance of the FDP tendon. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Sun Y, Chen MY, Zhao C, An KN, Amadio PC.

Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905.

Muscle stabilization strategies in people with medial knee osteoarthritis: The effect of instability.

The sensation of knee instability (shifting, buckling. and giving way) is common in people with medial knee osteoarthritis (OA). Its influence on knee stabilization strategies is unknown. This study investigated the influence of knee instability on muscle activation during walking when knee stability was challenged. Twenty people with medial knee OA participated and were grouped as OA Stable (OAS) (n = 10) and OA Unstable (OAU) (n = 10) based on self-reported knee instability during daily activities. Quadriceps strength, passive knee laxity, and varus alignment were assessed and related to knee instability and muscle cocontraction during walking when the support surface translated laterally. Few differences in knee joint kinematics between the groups were seen; however, there were pronounced differences in muscle activation. The OAU group used greater medial muscle cocontraction before, during, and following the lateral translation. Self-reported knee instability predicted medial muscle cocontraction, but medial laxity and limb alignment did not. The higher muscle cocontraction used by the OAU subjects appears to be an ineffective strategy to stabilize the knee. Instability and high cocontraction can be detrimental to joint integrity, and should be the focus of future research. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Schmitt LC, Rudolph KS.

University of Cincinnati College of Medicine, Sports Medicine Biodynamics Center, Occupational Therapy and Physical Therapy Department, Cincinnati Children\’s Hospital Medical Center, Cincinnati, Ohio 45229.

Pulsed electromagnetic fields enhance BMP-2 dependent osteoblastic differentiation of human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) express an osteoblastic phenotype when treated with BMP-2, and BMP-2 is used clinically to induce bone formation although high doses are required. Pulsed electromagnetic fields (PEMF) also promote osteogenesis in vivo, in part through direct action on osteoblasts. We tested the hypothesis that PEMF enhances osteogenesis of MSCs in the presence of an inductive stimulus like BMP-2. Confluent cultures of human MSCs were grown on calcium phosphate disks and were treated with osteogenic media (OM), OM containing 40 ng/mL rhBMP-2, OM + PEMF (8 h/day), or OM + BMP-2 + PEMF. MSCs demonstrated minor increases in alkaline phosphatase (ALP) during 24 days in culture and no change in osteocalcin. OM increased ALP and osteocalcin by day 6, but PEMF had no additional effect at any time. BMP-2 was stimulatory over OM, and PEMF + BMP-2 synergistically increased ALP and osteocalcin. PEMF also enhanced the effects of BMP-2 on PGE2, latent and active TGF-beta1, and osteoprotegerin. Effects of PEMF on BMP-2-treated cells were greatest at days 12 to 20. These results demonstrate that PEMF enhances osteogenic effects of BMP-2 on MSCs cultured on calcium phosphate substrates, suggesting that PEMF will improve MSC response to BMP-2 in vivo in a bone environment. (c) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Schwartz Z, Simon BJ, Duran MA, Barabino G, Chaudhri R, Boyan BD.

Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive NW, Atlanta, Georgia 30332.