Surgery with locking plate or hemiarthroplasty versus nonoperative treatment of 3-4-part proximal humerus fractures in older patients (NITEP): An open-label randomized trial

BACKGROUND

Proximal humerus fractures (PHFs) are common fractures, especially in older female patients. These fractures are commonly treated surgically, but the consensus on the best treatment is still lacking.

METHODS AND FINDINGS

The primary aim of this multicenter, randomized 3-arm superiority, open-label trial was to assess the results of nonoperative treatment and operative treatment either with locking plate (LP) or hemiarthroplasty (HA) of 3- and 4-part PHF with the primary outcome of Disabilities of the Arm, Shoulder, and Hand (DASH) at 2-year follow-up. Between February 2011 and December 2019, 160 patients 60 years and older with 3- and 4-part PHFs were randomly assigned in 1:1:1 fashion in block size of 10 to undergo nonoperative treatment (control) or operative intervention with LP or HA. In total, 54 patients were assigned to the nonoperative group, 52 to the LP group, and 54 to the HA group. Five patients assigned to the LP group were reassigned to the HA group perioperatively due to high comminution, and all of these patients had 4-part fractures. In the intention-to-treat analysis, there were 42 patients in the nonoperative group, 44 in the LP group, and 37 in the HA group. The outcome assessors were blinded to the study group. The mean DASH score at 2-year follow-up was 30.4 (standard error (SE) 3.25), 31.4 (SE 3.11), and 26.6 (SE 3.23) points for the nonoperative, LP, and HA groups, respectively. At 2 years, the between-group differences were 1.07 points (95% CI [-9.5,11.7]; p = 0.97) between nonoperative and LP, 3.78 points (95% CI [-7.0,14.6]; p = 0.69) between nonoperative and HA, and 4.84 points (95% CI [-5.7,15.4]; p = 0.53) between LP and HA. No significant differences in primary or secondary outcomes were seen in stratified age groups (60 to 70 years and 71 years and over). At 2 years, we found 30 complications (3/52, 5.8% in nonoperative; 22/49, 45% in LP; and 5/49, 10% in HA group, p = 0.0004) and 16 severe pain-related adverse events. There was a revision rate of 22% in the LP group. The limitation of the trial was that the recruitment period was longer than expected due to a high number of exclusions after the assessment of eligibility and a larger exclusion rate than anticipated toward the end of the trial. Therefore, the trial was ended prematurely.

CONCLUSIONS

In this study, no benefit was observed between operative treatment with LP or HA and nonoperative treatment in displaced 3- and 4-part PHFs in patients aged 60 years and older. Further, we observed a high rate of complications related to operative treatments.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01246167.

Musculoskeletal injuries in trauma patients: a Swedish nationwide register study including 37,266 patients

BACKGROUND AND PURPOSE

Trauma causes over 4 million annual deaths globally and accounts for over 10% of the global burden of disease. Trauma patients often sustain multiple injuries in multiple organ systems. We aimed to investigate the proportion and distribution of musculoskeletal injuries in adult trauma patients.

PATIENTS AND METHODS

This is a register-based study using data from the national Swedish trauma register (SweTrau) collected in 2015-2019. By categorizing Abbreviated Injury Scale (AIS) codes into different injury types, we provide a detailed description of the types of musculoskeletal injuries that occurred in trauma patients.

RESULTS

51,335 cases were identified in the register. After exclusion of 7,696 cases that did not have any trauma diagnosis (AIS codes) registered from the trauma and 6,373 patients aged < 18, a total of 37,266 patients were included in the study. 15,246 (41%) had sustained musculoskeletal injury. Of the patients with musculoskeletal injuries, 7,733 (51%) had more than 1 such injury. Spine injuries were the most common injury location (n = 7,083 patients, 19%) followed by lower extremity injuries (n = 5,943 patients, 16%) and upper extremity injuries (n = 6,273 patients, 17%). Fractures were the dominating injury type with 30,755 (87%) of injuries being a fracture.

CONCLUSION

41% of the trauma patients had at least 1 musculoskeletal injury. A spine injury was the most common injury location. Fractures was the dominating injury type constituting 87% of all injuries. We also found that half the patients (51%) with spine or extremity injuries had ≥ 2 such injuries.

Mortality following proximal humerus fracture-a nationwide register study of 147,692 fracture patients in Sweden

Little is known about survival after proximal humerus fracture. In this manuscript, we found the mortality to be high (almost four times higher than in age- and sex-matched controls). While frailty hip fracture has gained attention, we hope our manuscript will shed light on frailty proximal humerus fracture patients.

INTRODUCTION

Proximal humerus fractures (PHF) are common and occur mostly after the 6th decade of life. While mortality following PHF has been reported previously, mortality data after longer follow-up on a national level is lacking.

METHODS

We obtained data from the Swedish Hospital Discharge Register (SHDR), on all adult patients (≥ 18 years) with a diagnosis of PHF (S42.2, S42.20, or S42.21) for the period between 2001 and 2016. We used the Swedish Cause of Death Register (SCDR) to investigate mortality in the fracture cohort. We compared the mortality of fracture patients with age- and sex-matched population-based mortality data obtained from Statistics Sweden.

RESULTS

A total of 147 692 PHF patients were identified, with a male to female ratio of 1:3. The mean age was 69 years (range, 18 to 111). Most patients were treated non-surgically (n = 126,487, 86%). The crude mortality rate was 2.2% at 1 month, 4.1% at 3 months, 8.5% at 12 months, and 24% at 48 months after sustaining a PHF. Mortality increased with age; however, the standardized mortality rate (SMR) was highest among young patients. SMR was 5.4 in the 18- to 39-year age group, 3.9 in the 40- to 64-year age group, 1.8 in the 65-79-year age group, and 1.2 in the ≥ 80-year-old population. The age-adjusted SMR was 3.9 in the whole adult PHF population.

CONCLUSION

The mortality rate and SMR suggest that PHF patients are heterogeneous. Some older PHF patients may benefit from specialized care (e.g., orthogeriatric), and this should be evaluated in future studies.

Lumbar Loads and Muscle Activity During Flywheel and Barbell Leg Exercises

ABSTRACT

Sjöberg, M, Eiken, O, Norrbrand, L, Berg, HE, and Gutierrez-Farewik, EM. Lumbar loads and muscle activity during flywheel and barbell leg exercises. J Strength Cond Res 37(1): 27-34, 2023-It is anticipated that flywheel-based leg resistance exercise will be implemented in future long-duration space missions, to counter deconditioning of weight-bearing bones and postural muscles. The aim was to examine low back loads and muscle engagements during flywheel leg press (FWLP) and flywheel squat (FWS) and, for comparisons, free-weight barbell back squat (BBS). Eight resistance-trained subjects performed 8 repetition maximums of FWLP, FWS, and BBS. Motion analysis and inverse dynamics-based musculoskeletal modeling were used to compute joint loads and muscle forces. Muscle activities were measured with electromyography (EMG). At the L4-L5 level, peak vertebral compression force was similarly high in all exercise modes, whereas peak vertebral posteroanterior shear force was greater ( p < 0.05) in FWLP and BBS than in FWS. Among the back-extensor muscles, the erector spinae longissimus exerted the greatest peak force, with no difference between exercises. Peak force in the lumbar multifidus was lower ( p < 0.05) during FWLP than during FWS and BBS. Peak EMG activity in the lumbar extensor muscles ranged between 31 and 122% of maximal voluntary isometric contraction across muscles and exercise modes, with the greatest levels in the lumbar multifidus. The vertebral compression forces and muscle activations during the flywheel exercises were sufficiently high to presume that when implementing such exercise in space countermeasure regimens, they may be capable of preventing muscle atrophy and vertebral demineralization in the lumbar region.

Secular trends in incidence and seasonal variation of distal radius fracture among children: A nationwide study based on the Swedish National Patient Register 2002-2016

BACKGROUND AND PURPOSE

Although distal radius fracture (DRF) is the most common fracture type in children, research on its seasonality across different age groups is limited. We investigated secular trends in incidence and seasonal variation of pediatric DRF based on Swedish nationwide population database.

PATIENTS AND METHODS

In this observational study, data for all children aged <18 years in Sweden with DRF defined by ICD-codes were analyzed for each month and each year during 2002-2016 using the Swedish National Patient Register. The general population counts for each age and sex-category were acquired to evaluate population at risk for each period. We calculated the age standardized and sex specific annual incidence rates, seasonal incidence rates, and monthly incidence rates and analyzed the seasonal variation in the mechanisms of injury.

RESULTS

A total of 155,891 DRF cases were identified. The age standardized and sex specific incidence rate was 531 (95%CI 528-533) per 100,000 patient years at risk. Fracture risk was highest during summer and lowest in the winter. The highest seasonal variation was observed among boys 2- < 5 years. The crude incidence rate and the age-standardized incidence rates in winter significantly decreased between 2002 and 2016 (annual percentage change, -2 %).

INTERPRETATION

We found significant seasonal variation in DRF among all age groups in Swedish children. The findings can help in developing strategies to prevent fractures as well as in allocating medical and social resources.

Incidence of femoral fractures in children and adolescents in Finland and Sweden between 1998 and 2016: A binational population-based study

BACKGROUND AND OBJECTIVE

Femoral fractures in children have significant impact for patients, family, and trauma resources as they usually require hospitalization and surgical treatment. The aim of this study was to determine the incidence and trends of femoral fractures among children and adolescents hospitalized between 1998 and 2016 in Finland and Sweden.

METHODS

All patients younger than 17 years of age in Finland and Sweden with a femoral fracture treated surgically between 1998 and 2016 were included in the study. Data were collected from National Hospital Discharge Registries. Patients were classified by gender and age into four groups. The annual incidences per 100,000 were calculated using annual mid-year population census data obtained from the Official Statistics of Finland and Sweden.

RESULTS

In total, 6410 patients younger than 17 years of age diagnosed with femoral fracture were included in this study. The total incidence per 100,000 femoral fractures was 13.3 in Finland and 11.0 in Sweden. The incidence of femoral fractures decreased during the study period in all age groups, except for teenage Finnish girls. Most of the fractures were located in femoral shaft. Fractures of the upper and distal femur were rare. Male predominance was detected in all age groups older than 1 year.

CONCLUSIONS

The incidence of femoral fractures decreased in all age groups except in teenage Finnish girls. Majority of femoral fractures were located in femoral shaft with male predominance. In children younger than 1 year of age, female predominance was found.

Functional improvements to 6 months of physical activity are not related to changes in size or density of multiple lower-extremity muscles in mobility-limited older individuals

Older adults are encouraged to engage in multicomponent physical activity, which includes aerobic and muscle-strengthening activities. The current work is an extension of the Vitality, Independence, and Vigor in the Elderly 2 (VIVE2) study - a 6-month multicenter, randomized, placebo-controlled trial of physical activity and nutritional supplementation in community dwelling 70-year-old seniors. Here, we examined whether the magnitude of changes in muscle size and quality differed between major lower-extremity muscle groups and related these changes to functional outcomes. We also examined whether daily vitamin-D-enriched protein supplementation could augment the response to structured physical activity. Forty-nine men and women (77 ± 5 yrs) performed brisk walking, muscle-strengthening exercises for the lower limbs, and balance training 3 times weekly for 6 months. Participants were randomized to daily intake of a nutritional supplement (20 g whey protein + 800 IU vitamin D), or a placebo. Muscle cross-sectional area (CSA) and radiological attenuation (RA) were assessed in 8 different muscle groups using single-slice CT scans of the hip, thigh, and calf at baseline and after the intervention. Walking speed and performance in the Short Physical Performance Battery (SPPB) were also measured. For both CSA and RA, there were muscle group × time interactions (P < 0.01). Significant increases in CSA were observed in 2 of the 8 muscles studied, namely the knee extensors (1.9%) and the hip adductors (2.8%). For RA, increases were observed in 4 of 8 muscle groups, namely the hip flexors (1.1 HU), hip adductors (0.9 HU), knee extensors (1.2 HU), and ankle dorsiflexors (0.8 HU). No additive effect of nutritional supplementation was observed. While walking speed (13%) and SPPB performance (38%) improved markedly, multivariate analysis showed that these changes were not associated with the changes in muscle CSA and RA after the intervention. We conclude that this type of multicomponent physical activity program results in significant improvements in physical function despite relatively small changes in muscle size and quality of some, but not all, of the measured lower extremity muscles involved in locomotion.

Comparison of Joint and Muscle Biomechanics in Maximal Flywheel Squat and Leg Press

The aim was to compare the musculoskeletal load distribution and muscle activity in two types of maximal flywheel leg-extension resistance exercises: horizontal leg press, during which the entire load is external, and squat, during which part of the load comprises the body weight. Nine healthy adult habitually strength-training individuals were investigated. Motion analysis and inverse dynamics-based musculoskeletal modelling were used to compute joint loads, muscle forces, and muscle activities. Total exercise load (resultant ground reaction force; rGRF) and the knee-extension net joint moment (NJM) were slightly and considerably greater, respectively, in squat than in leg press (p ≤ 0.04), whereas the hip-extension NJM was moderately greater in leg press than in squat (p = 0.03). Leg press was performed at 11° deeper knee-flexion angle than squat (p = 0.01). Quadriceps muscle activity was similar in squat and leg press. Both exercise modalities showed slightly to moderately greater force in the vastii muscles during the eccentric than concentric phase of a repetition (p ≤ 0.05), indicating eccentric overload. That the quadriceps muscle activity was similar in squat and leg press, while rGRF and NJM about the knee were greater in squat than leg press, may, together with the finding of a propensity to perform leg press at deeper knee angle than squat, suggest that leg press is the preferable leg-extension resistance exercise, both from a training efficacy and injury risk perspective.

Secular trends in hip fracture incidence and subsequent mortality in dialysis patients and the general population in Sweden

BACKGROUND

Declining trends of hip fracture incidence in dialysis patients were reported from USA and Japan while studies from Europe are lacking. We investigated trends in hip fracture incidence and subsequent mortality in Swedish dialysis patients, comparing with the Swedish general population.

METHODS

We used the population-based Swedish national database of fractures and the Swedish National Renal Registry to retrieve data on hip fractures incidence and subsequent mortality for years 2007-2016. Trends for age-standardized hip fracture incidence rate (ASR_{hip fracture}) and age-standardized 30-day (ASMR_30day) and 180-day (ASMR_180day) post-hip fracture mortality rate in Swedish general population were evaluated by joinpoint regression analysis. Standardized incidence ratios of hip fracture (SIR) and standardized mortality ratios (SMR) were calculated for Swedish dialysis patients.

RESULTS

In the general population, ASR_{hip fracture} declined significantly: in women from 2007 and in men from 2009. In dialysis patients, SIR was 3-5 times higher compared to the general population and declined over time in women but not in men. In general population, mortality (ASMR_30day and ASMR_180day) declined significantly in women and men. In dialysis patients, post-fracture mortality (SMR, mainly for 180-day mortality) remained two-fold higher than in general population with no consistent trend towards improvement.

CONCLUSIONS

Hip fracture incidence and subsequent mortality fell among women and men in the Swedish general population. In dialysis patients, hip fracture incidence declined in women but not in men while post-fracture mortality did not improve, and the incidence and subsequent mortality remained 3 to 5-fold and 2-fold higher than in the general population.

Epidemiology and mortality of pelvic and femur fractures-a nationwide register study of 417,840 fractures in Sweden across 16 years: diverging trends for potentially lethal fractures

Background and purpose - Fractures of the pelvis and femur are serious and potentially lethal injuries affecting primarily older, but also younger individuals. Long-term trends on incidence rates and mortality might diverge for these fractures, and few studies compare trends within a complete adult population. We investigated and compared incidence and mortality rates of pelvic, hip, femur shaft, and distal femur fractures in the Swedish adult population.Patients and methods - We analyzed data on all adult patients ≥ 18 years in Sweden with a pelvic, hip, femur shaft, or distal femur fracture, through the Swedish National Patient Register. The studied variables were fracture type, age, sex, and 1-year mortality.Results - While incidence rates for hip fracture decreased by 18% (from 280 to 229 per 105 person-years) from 2001 to 2016, incidence rates for pelvic fracture increased by 25% (from 64 to 80 per 105 person-years). Incidence rates for femur shaft and distal femur fracture remained stable at rates of 15 and 13 per 105 person-years respectively. 1-year mortality after hip fracture was 25%, i.e., higher than for pelvic, femur shaft, and distal femur fracture where mortality rates were 20-21%. Females had an almost 30% lower risk of death within 1 year after hip fracture compared with males.Interpretation - Trends on fracture incidence for pelvic and femur fractures diverged considerably in Sweden between 2001 and 2016. While incidence rates for femur fractures (hip, femur shaft, and distal femur) decreased or remained constant during the studied years, pelvic fracture incidence increased. Mortality rates were different between the fractures, with the highest mortality among patients with hip fracture.

STOP leg clots-Swedish multicentre trial of outpatient prevention of leg clots: study protocol for a randomised controlled trial on the efficacy of intermittent pneumatic compression on venous thromboembolism in lower leg immobilised patients

INTRODUCTION

Leg immobilisation in a cast or an orthosis after lower limb injuries is associated with a high risk of complications of venous thromboembolism (VTE) and hampered healing. Current pharmacoprophylaxes of VTE are inefficient and associated with adverse events. Intermittent pneumatic compression (IPC) could represent a novel, efficient and safe VTE-prophylactic alternative that may enhance injury healing. The aim of STOP leg clots is to assess the efficacy of adjuvant IPC-therapy on reduction of VTE incidence and improvement of healing in lower leg immobilised outpatients.

METHODS AND ANALYSIS

STOP leg clots is a multicentre randomised controlled superiority trial. Eligible patients (700 patients/arm) with either an acute ankle fracture or Achilles tendon rupture will be randomised to either addition of IPC during lower-leg immobilisation or to treatment-as-usual. The primary outcome will be the total VTE incidence, that is, symptomatic and asymptomatic deep venous thrombosis (DVT) or symptomatic pulmonary embolism (PE), during the leg immobilisation period, approximately 6-8 weeks. DVT incidence will be assessed by screening whole leg compression duplex ultrasound at removal of leg immobilisation and/or clinically diagnosed within the time of immobilisation. Symptomatic PE will be verified by CT.Secondary outcomes will include patient-reported outcome using validated questionnaires, healing evaluated by measurements of tendon callus production and changes in VTE-prophylactic mechanisms assessed by blood flow and fibrinolysis. Data analyses will be blinded and based on the intention-to-treat.

ETHICS AND DISSEMINATION

Ethical approval was obtained by the ethical review board in Stockholm, Sweden, Dnr 2016/1573-31. The study will be conducted in accordance with the Helsinki declaration. The results of the study will be disseminated in peer-reviewed international journals.

TRIAL REGISTRATION

NCT03259204.

TIME SCHEDULE

1 September 2018 to 31 December 2022.

Incidence of Fractures Before and After Dialysis Initiation

Fractures are common in dialysis patients, but little is known about the trajectory of incidence rates of different types of fractures before and after dialysis initiation. To address this, we investigated the incidence of major fractures before and after dialysis initiation. We performed a retrospective statistical analysis using the Swedish Renal Registry of 9041 incident dialysis patients (median age 67 years, 67% men) starting dialysis 2005 through 2015 to identify major fractures (hip, spine, humerus, and forearm) occurring during the dialysis transition period from 1 year before until 1 year after dialysis initiation. Using flexible parametric hazard models and the Fine-Gray model, we estimated adjusted fracture incidence rates and predictors of major fractures. We identified 361 cases with primary diagnosis of major fracture, of which 196 (54%) were hip fractures. The crude incidence rate of major fractures before dialysis initiation was 17 per 1000 patient-years (n = 157) and after dialysis initiation it was 24 per 1000 patient-years (n = 204). The adjusted incidence rate of major fractures began to increase 6 months before dialysis initiation, and then stabilized at a higher rate after 1 year. The adjusted incidence rate of hip fractures started to increase sharply 3 months before dialysis initiation, peaked at initiation, and declined thereafter. In contrast, the adjusted incidence rate of non-hip fractures was stable during the transition period and gradually increased over time. Higher age, female sex, and history of previous major fractures were associated with increased fracture incidence both before and after dialysis initiation. We conclude that the incidence of major fractures, especially hip fractures, start to rise 6 months before initiation of dialysis therapy, indicating that heightened surveillance with implementation of preventive measures to avoid fractures is warranted during the transition period to dialysis. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Fractures after kidney transplantation: Incidence, predictors, and association with mortality

BACKGROUND

Major fractures (MF) are associated with increased mortality in the general population and represent an even higher risk in patients with chronic kidney disease. We investigated incidence, predictors and clinical outcomes associated with first MF (MF_first) following kidney transplantation (KT).

METHODS

We used the Swedish National Renal Registry of 3992 first KT recipients (2005-2016) (median age 53 years, 65% men) and identified all MF_first in hip, spine, humerus and forearm following KT. We estimated incidence rates and predictors of MF_first using flexible parametric hazard models and Fine-Gray analysis accounting for competing risk of death, and risk of all-cause mortality following MF_first using Cox proportional hazards models with fracture as time-varying exposure.

RESULTS

During median follow-up of 4.8 years (IQR 2.2-7.9 years), there were 279 fractures of which 139 were forearm fractures. The crude incidence rate of MF_first (n = 279) was 13.5/1000 patient-years and that of hip fractures (n = 69) 3.4/1000 patient-years. The multivariate-adjusted fracture incidence rates were highest during the first 6 months following KT, and 86% higher in women than in men. High age, female sex, previous history of MF, diabetes nephropathy, pretransplant dialysis therapy and acute rejection were associated with increased risk for MF_first, whereas pre-emptive KT was associated with lower risk of MF_first. Spline curves showed markedly higher impact of higher age on risk of MF_first in women than in men. MF_first (n = 279) independently predicted increased all-cause mortality risk (hazard ratio, HR, 1.78(95%CI 1.35-2.36)). Among MF_first, with humerus fracture as reference, hip fracture (HR, 4.68(95%CI 1.56-14.06)) and spine fracture (HR, 4.02(95%CI 1.19-13.54)), but not forearm fracture (HR, 1.17 (95%CI 0.38-3.53)), were associated with increased all-cause mortality risk.

CONCLUSIONS

The initial 6 months following kidney transplantation is a high-risk period for MF. Among MF, hip fracture and spine fracture associate with substantially increased all-cause mortality risk.

Distal Biceps Tendon Rupture Surgery: Changing Incidence in Finnish and Swedish Men Between 1997 and 2016

PURPOSE

Distal biceps tendon rupture is a relatively rare injury usually occurring with excess external extension force applied to a flexed elbow. The aim of this study was to examine the incidence of distal biceps tendon rupture surgery in the Finnish and Swedish adult population between the years 1997 and 2016. A secondary aim was to investigate the distal biceps rupture incidence in the Swedish population in 2001 to 2016.

METHODS

We assessed the number and rate of distal biceps tendon rupture surgery using the Finnish and Swedish Hospital Discharge Register as databases. The study included the entire Finnish and Swedish adult population aged 18 years and older between January 1, 1997 and of December 31, 2016.

RESULTS

During the study period, 2,029 patients had a distal biceps tendon rupture in Finland, and the corresponding figure was 2,000 in Sweden. The rate of distal biceps tendon rupture surgery increased steeply, but equally, in both countries, in Finnish men from 1.3 per 100,000 person-years in 1997 to 9.6 in 2016, and in Swedish men from 0.2 in 1997 to 5.6 in 2016. The incidence of distal biceps tendon rupture in Sweden increased in men from 1.6 to 10.0 per 100,000 person-years from 2001 to 2016.

CONCLUSIONS

There was a 7-fold and a 28-fold increase in the incidence of distal biceps tendon rupture surgery in Finnish and Swedish men during 1997 to 2016. The incidence of distal biceps tendon rupture rose 6-fold in Swedish men in 2001 to 2016.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Anaerobes Direct from Blood Culture Bottles Can Be Identified by Early Matrix-Assisted Laser Desorption Ionization/ Time-of-Flight Mass Spectrometry (MALDI-TOF MS) at 24 Hours or Less

Introduction/Objective

Matrix-assisted laser desorption ionization/ time-of-flight mass spectrometry (MALDI-TOF MS) direct from positive blood culture bottles has facilitated drastic drops in turn-around times for microorganism identification but has been poorly studied for anaerobes. We investigated the ability of MALDI-TOF to provide early anaerobe identification at 4 hours and 18-24 hours of growth on agar from anaerobic blood culture bottles.

Additionally, we reviewed medical records of such patients to ascertain impact of early identification on antimicrobial treatment.

Methods

Over 9 months, we ran MALDI-TOF on early growth from blood cultures positive for growth in BACTEC™ Lytic/ 10 Anaerobic/F bottles. Broth from each bottle was subbed to sheep blood agar (4 hours, 5% CO2) and 2 CDC (BD-BBL™) anaerobic blood agar plates (examined 18-24 hours and 48 hours). Bruker Biotyper® RUO v7854 and Mayo Clinic Custom MALDI-TOF MS libraries were used for identification.

Results

144/184 (78%) bottles resulted in growth of aerobic bacteria. Of the remaining bottles with growth of anaerobes, 38 were assessed by early MALDI-TOF. Early MALDI-TOF at 4 hours identified 3 Clostridium perfringens (8%) and an additional 26/38 (68%) isolates at 18-24 hours (both Gram-positive and –negative). Routine 48 hour identification was required for 9 (24%) isolates. In 7 cases, early MALDI-TOF resulted in a change to more appropriate antimicrobial therapy, most often for Bacteroides.

Conclusion

29/38 (76%) of anaerobes from blood culture bottles were identified by early MALDI-TOF and reported to the clinician at least 24 hours before routine review of anaerobic sub plates for growth. All C. perfringens and Bacteroides were identified by 4 and 24 hours, respectively. Although early MALDI-TOF resulted in antimicrobial therapy adjustments in a minority of cases, it may allow for more targeted and earlier antimicrobial therapy. Early MALDI-TOF from anaerobic blood culture bottles should be considered for improved patient care and antimicrobial stewardship.

Influence of gravity on biomechanics in flywheel squat and leg press

Resistance exercise on Earth commonly involves both body weight and external load. When developing exercise routines and devices for use in space, the absence of body weight is not always adequately considered. This study compared musculoskeletal load distribution during two flywheel resistance knee-extension exercises, performed in the direction of (vertical squat; S) or perpendicular to (horizontal leg press; LP) the gravity vector. Eleven participants performed these two exercises at a given submaximal load. Motion analysis and musculoskeletal modelling were used to compute joint loads and to simulate a weightless situation. The flywheel load was more than twice as high in LP as in S (p < 0.001). Joint moments and forces were greater during LP than during S in the ankle, hip and lower back (p < 0.01) but were similar in the knee. In the simulated weightless situation, hip and lower-back loadings in S were higher than corresponding values at Earth gravity (p ≤ 0.01), whereas LP joint loads did not increase. The results suggest that LP is a better terrestrial analogue than S for knee-extension exercise in weightlessness and that the magnitude and direction of gravity during resistance exercise should be considered when designing and evaluating countermeasure exercise routines and devices for space.

A 1-year perspective on goal-directed therapy in elderly with hip fracture: Secondary outcomes

BACKGROUND

We have previously reported inconclusive results from a randomized controlled trial in elderly with hip-fracture comparing intra-operative goal-directed therapy with routine fluid treatment. Now we aimed to describe and compare secondary outcomes at 4 months and 1 year follow-up and to analyze the cost-effectiveness.

METHODS

Patients with hip fracture (age ≥70) were randomized for GDT or routine fluid treatment (RFT). The secondary outcomes were long-term survival, complications, number of hospital readmissions, and quality of life (EQ-5D) changes. Additionally, cost effectiveness was analyzed by an analytic tool which combines the clinical effectiveness, quality of life changes and costs.

RESULTS

Patient data (GDT n = 74; RFT n = 75) were analyzed on an intention to treat basis. Statistically significant differences (GDT vs RFT) were not found considering survival (RR 0.76, 95%CI 0.45-1.28) and complications (RR 0.68, 95% CI 0.4-1.10) at 12 months. No statistically significant difference was found between hospital readmissions and quality of life changes.

CONCLUSION

The statistical uncertainty of risk reduction of negative outcomes and the large variability of the collected data indicate the need of further research in large sample sizes. To enable future health economic evaluation for decision support surrounding implementation of GDT, we suggest adding patient-oriented outcomes in future trials.

Foot centre of pressure and ground reaction force during quadriceps resistance exercises; a comparison between force plates and a pressure insole system

The study compared the centre of pressure measurements (COP) and vertical ground reaction forces (vGRF) from a pressure insole system to that from force plates (FP) during two flywheel quadriceps resistance exercises: leg press and squat. The comparison was performed using a motion capture system and simultaneous measurements of COP and vGRF from FP and insoles. At lower insole-vGRF (<250 N/insole) COP accuracy deteriorated and those data were excluded from further analysis. The insoles systematically displaced the COP slightly posteriorly and medially compared to the FP measurements. Pearson's coefficient of correlation (r) between insole- and FP-COP showed good agreement in both the anteroposterior (squat: r = 0.96, leg press: r = 0.97) and mediolateral direction (squat: r = 0.84, leg press: r = 0.90), whereas the root-mean-square errors (RMSE) were lower in the mediolateral (squat: 3.9 mm, leg press: 4.5 mm) than the anteroposterior (squat and leg press: 11.8 mm) direction. Vertical GRF was slightly overestimated by the insoles in leg press and RMSE were greater in leg press (8% of peak force) than in squat (6%). Overall, results were within the range of previous studies performed on gait. The strong agreement between insole and FP measurements indicates that insoles may replace FPs in field applications and biomechanical computations during resistance exercise, provided that the applied force is sufficient.

Cartilage Health in Knees Treated with Metal Resurfacing Implants or Untreated Focal Cartilage Lesions: A Preclinical Study in Sheep

BACKGROUND

Full-depth cartilage lesions do not heal and the long-term clinical outcome is uncertain. In the symptomatic middle-aged (35-60 years) patient, treatment with metal implants has been proposed. However, the cartilage health surrounding these implants has not been thoroughly studied. Our objective was to evaluate the health of cartilage opposing and adjacent to metal resurfacing implants.

METHODS

The medial femoral condyle was operated in 9 sheep bilaterally. A metallic resurfacing metallic implant was immediately inserted into an artificially created 7.5 mm defect while on the contralateral knee the defect was left untreated. Euthanasia was performed at 6 months. Six animals, of similar age and study duration, from a previous study were used for comparison in the evaluation of cartilage health adjacent to the implant. Cartilage damage to joint surfaces within the knee, cartilage repair of the defect, and cartilage adjacent to the implant was evaluated macroscopically and microscopically.

RESULTS

Six animals available for evaluation of cartilage health within the knee showed a varying degree of cartilage damage with no statistical difference between defects treated with implants or left untreated ( P = 0.51; 95% CI -3.7 to 6.5). The cartilage adjacent to the implant (score 0-14; where 14 indicates no damage) remained healthy in these 6 animals showing promising results (averaged 10.5; range 9-11.5, SD 0.95). Cartilage defects did not heal in any case.

CONCLUSION

Treatment of a critical size focal lesion with a metal implant is a viable alternative treatment.

Proximal humeral fractures in Sweden-a registry-based study

Proximal humeral fracture is the third most common osteoporotic fracture. To our knowledge, this is the first nationwide population-based registry study in adults that includes both inpatient and outpatient visits. Thus, we were able to report the true incidence rates and trends in the treatment of proximal humeral fractures.

INTRODUCTION

Proximal humeral fractures are among the most common osteoporotic fractures. Valid epidemiologic population-based data, including both inpatient and outpatient visits, however, are lacking.

METHODS

To investigate the Swedish national incidence rates and treatment trends of proximal humeral fractures, we obtained data from the Swedish Hospital Discharge Register between 2001 and 2012. All adult patients (≥18 years of age) in the Swedish Hospital Discharge Register were included. Outpatient visits have been included in the register since 2001.

RESULTS

We identified 98,770 patients (women n = 72,063; 73 %) with proximal humeral fractures between 2001 and 2012. In 2001, the sex-specific incidence of proximal humeral fractures was 134.5 per 100,000 person-years for women and 49.2 for men. In 2012, the corresponding values were 174.6 for women and 68.1 for men, increasing 30 % in women and 39 % in men. A total of 17,013 surgical procedures were conducted between 2001 and 2012. Open reduction and internal fixation with a plate was the most common procedure (n = 5050, 30 %), followed by endoprosthetic implantation (n = 3962, 23 %) and intramedullary nailing (n = 3376, 20 %). The proportion of surgically treated patients increased from 12.1 % in 2001 to 16.8 % in 2012 for women and from 15.1 % in 2001 to 17.1 % in 2012 for men.

CONCLUSION

The Swedish national incidence of proximal humeral fractures has been increasing, although it seems to have peaked in the elderly population during 2008-2010. The rate of surgical treatment has increased substantially, particularly open reduction and internal fixation with a plate. To our knowledge, this is the first nationwide epidemiologic study for Sweden reporting the incidence of proximal humeral fractures and including all inpatient and outpatient visits.

Trends in the Incidence of Clavicle Fractures and Surgical Repair in Sweden: 2001-2012

BACKGROUND

Clavicle fractures are common injuries causing substantial morbidity. Recent literature suggests that the incidence of surgically treated clavicle fractures has increased. However, it is unknown whether the increase is caused by more surgeons choosing operative over nonoperative treatment for the injury or an increase in the actual incidence of clavicle fractures. The aim of this study was to assess both the national incidence of clavicle fractures and the rate of surgical treatment of those fractures in Sweden.

METHODS

We assessed the incidence and trends of clavicle fractures and rates of surgery in Sweden. The validated Swedish Hospital Discharge Register offers a unique opportunity to assess both outpatient and inpatient visits and was used to conduct a national register-based study including all adults (≥18 years of age) with a diagnosis of clavicle fracture in Sweden between 2001 and 2012.

RESULTS

A total of 44,609 clavicle fractures occurred in Sweden between 2001 and 2012. The incidence of clavicle fractures increased from 35.6 per 100,000 person-years in 2001 to 59.3 per 100,000 person-years in 2012. Interestingly, the highest incidence rates were observed in the oldest age groups. The increase in the rate of surgically treated clavicle fractures (705%) was greater than the increase in the actual fracture incidence (67%). Most (77%) of the surgically treated patients were men. Open reduction and plate fixation was the most common surgical procedure. Overall, the proportion of surgically treated clavicle fractures increased markedly.

CONCLUSIONS

Although the incidence of clavicle fractures increased in Sweden between 2001 and 2012, the rate of surgical treatment of clavicle fractures increased much more than could be expected solely based on the increase in the fracture incidence. The observed changes in the rates of surgery require additional studies since there is still controversy regarding the indications for surgical treatment.

Treatment of full thickness focal cartilage lesions with a metallic resurfacing implant in a sheep animal model, 1 year evaluation

BACKGROUND

Full depth focal cartilage lesions do not heal spontaneously and while some of these lesions are asymptomatic they might progress to osteoarthritis. Treatment for these lesions is warranted and the gold standard treatment at younger age remains biological healing by cell stimulation. In the middle-age patient the success rate of biologic treatment varies, hence the surge of non-biological alternatives. Our objective was to evaluate the efficacy and safety of a metallic implant for treatment of these lesions with respect to the long-term panarticular cartilage homeostasis.

METHODS

The medial femoral condyle of 16 sheep was operated unilaterally. A metallic implant was inserted in the weight-bearing surface at an aimed height of 0.5 mm recessed. Euthanasia was performed at 6 or 12 months. Implant height and tilt was analyzed using a laser-scanning device. Damage to cartilage surfaces was evaluated macroscopically and microscopically according to the Osteoarthritis Research Society International (OARSI) recommendations.

RESULTS

Thirteen sheep were available for evaluation and showed a varying degree of cartilage damage linearly increasing with age. Cartilage damage of the medial tibial plateau opposing the implant was increased compared to the non-operated knee by 1.77 units (p = 0.041; 95% CI: 0.08, 3.45) on a 0-27 unit scale. Remaining joint compartments were unaffected. Implant position averaged 0.54 recessed (95% CI: 0.41, 0.67).

CONCLUSIONS

Our results showed a consistent and accurate placement of these implants at a defined zone. At this position cartilage wear of opposing and surrounding joint cartilage is limited. Thus expanded animal and human studies are motivated.

Fixation of a double-coated titanium-hydroxyapatite focal knee resurfacing implant: a 12-month study in sheep

OBJECTIVE

Focal cartilage lesions according to International Cartilage Repair Society (ICRS) grade 3-4 in the medial femoral condyle may progress to osteoarthritis. When treating such focal lesions with metallic implants a sound fixation to the underlying bone is mandatory. We developed a monobloc unipolar cobalt-chrome (Co-Cr) implant with a double coating; first a layer of commercially pure titanium (c.p.Ti) on top of which a layer of hydroxyapatite (HA) was applied. We hypothesised that such a double coating would provide long-lasting and adequate osseointegration.

DESIGN (MATERIALS AND METHODS)

Unilateral medial femoral condyles of 10 sheep were operated. The implants were inserted in the weight-bearing surface and immediate weight-bearing was allowed. Euthanasia was performed at 6 (three animals) or 12 months (six animals). Osseointegration was analysed with micro-computer tomography (CT), light microscopy and histomorphometric analyses using backscatter scanning electron microscopy (B-SEM) technique.

RESULTS

At 6 months one specimen out of three showed small osteolytic areas at the hat and at 12 months two specimens out of six showed small osteolytic areas at the hat, no osteolytical areas were seen around the peg at any time point. At both time points, a high total bone-to-implant contact was measured with a mean (95% confidence interval - CI) of 90.6 (79-102) at 6 months and 92.3 (89-95) at 12 months, respectively.

CONCLUSIONS

A double coating (Ti + HA) of a focal knee resurfacing Co-Cr implant was presented in a sheep animal model. A firm and consistent bond to bone under weight-bearing conditions was shown up to 1 year.

Focal knee resurfacing and effects of surgical precision on opposing cartilage. A pilot study on 12 sheep

BACKGROUND

Full thickness cartilage lesions (ICRS grade 3-4) and focal lesions of degenerative origin may progress to osteoarthritis (OA). Such focal lesions can be treated by metallic implants. We hypothesized that such treatment results in opposing surface cartilage damage that correlates with implant position (height) relative to the adjacent cartilage surface. This relationship was investigated using a sheep animal model.

METHODS

Both medial femoral condyles of 12 sheep were operated. The implants, were inserted in the weight-bearing surface at different heights relative to the surrounding cartilage. Euthanasia was performed at 6 or 12 weeks. After retrieval, implant height was analyzed using laser scanning. Damage to the opposing tibial cartilage was evaluated macroscopically and microscopically according to the modified Mankin score.

RESULTS

Twenty-two knees were available for evaluation and showed cartilage lesions ranging from severe damage (Mankin stage 11) to almost pristine conditions (Mankin stage 1). There was a strong correlation between implant height and cartilage damage. Standard deviation from the aimed implant height was 0.47 mm.

CONCLUSIONS

Our results showed significant surgical imprecision and protruding implants imposed severe cartilage damage. We therefore suggest implants should be placed recessed (approx. 0.5 mm) below the surrounding cartilage in this animal model. These results encourage further studies of metallic implants yet the utmost precision regarding position is required.

Muscle strength, gait, and balance in 20 patients with hip osteoarthritis followed for 2 years after THA

BACKGROUND

Patients with hip osteoarthritis (OA) have muscular weakness, impaired balance, and limp. Deficits in the different limb muscles and their recovery courses are largely unknown, however. We hypothesized that there is persisting muscular weakness in lower limb muscles and an impaired balance and gait 2 years after THA.

PATIENTS AND METHODS

20 elderly patients with unilateral OA were assessed before, and 6 and 24 months after surgery for maximal voluntary isometric strength of hip and knee muscles and by gait analysis, postural stability, and clinical scores (HHS, SF-36, EuroQoL).

RESULTS

Hip muscles showed a remaining 6% weakness compared to the contralateral healthy limb 2 years after THA. Preoperatively and 6 months postoperatively, that deficit was 18% and 12%, respectively. Knee extensors fully recovered a preoperative 27% deficit after 2 years. Gait analysis demonstrated a shorter single stance phase for the OA limb compared to healthy limb preoperatively, that had already recovered at the 6-month follow-up. Balance of two-foot standing showed improvement in both sagittal and lateral sway after operation. All clinical scores improved.

INTERPRETATION

Muscle strength data demonstrated a slow but full recovery of muscles acting about the knee, but there was still a deficit in hip muscle strength 2 years after THA. Gait and balance recovered after the operation. To accelerate improvement in muscular strength after THA, postoperative training should probably be more intense and target hip abductors.

Persisting muscle atrophy two years after replacement of the hip

Muscle atrophy has been demonstrated in patients suffering from osteoarthritis of the hip, but little is known about muscular recovery after total hip replacement (THR). A total of 20 patients with unilateral osteoarthritis of the hip were assessed before, six months and two years after THR. The cross-sectional area and radiological density of the muscles of the hip, thigh, calf and back were measured using CT. We hypothesised that the muscles would not recover fully after operation. After two years comparison of the limb with the THR with the healthy limb showed that there was such a reduction in the cross-sectional area in iliopsoas (7.0%; p = 0.006) and the hip adductors (8.4%, p = 0.003) and in the radiological density in gluteus maximus (10.1 Hounsfield units; p < 0.001), gluteus medius/minimus (5.6 Hounsfield units; p = 0.011), iliopsoas (3.9 Hounsfield units; p < 0.001) and the adductors (2.4 Hounsfield units; p = 0.022). Thus, there was persistent muscle atrophy in muscles acting about the hip two years after THR. We suggest that an earlier operation or a more intensive rehabilitation may reverse these changes.

Reduced muscle radiological density, cross-sectional area, and strength of major hip and knee muscles in 22 patients with hip osteoarthritis

BACKGROUND

Patients with hip osteoarthritis (OA) typically suffer joint pain, and often experience muscular weakness. We hypothesized that substantial atrophy would manifest in multiple muscle groups along the affected limb, resulting in severe muscle dysfunction.

PATIENTS AND METHODS

We assessed 22 elderly patients with unilateral OA for maximal voluntary isometric strength of hip and knee muscles using a dynamometer that was developed for the purpose. Cross-sectional area (CSA) and radiological density (RD; in Hounsfield units: HU) of hip and knee muscles were assessed using CT. We determined SF-36, HHS, and EQ-5D.

RESULTS

Hip extension, flexion, adduction, abduction, and knee extension strength were reduced (11- 29%; p < 0.01) in the OA limb relative to the healthy limb. Muscle CSA of hip extensors, flexors, adductors, knee extensors and flexors, but not hip abductors, was reduced (11-19%; p < 0.01) in the OA limb, where RD of all muscle groups except hip flexors was reduced (5-15 HU; p < 0.01). The clinical scores confirmed impairment.

INTERPRETATION

Major muscles functioning around the hip and knee showed substantial loss of strength and mass, which contributes to the reduced ambulatory capacity of OA patients. Reduced muscle CSA could not fully explain the loss in strength. Infiltration with fat or other non-contractile components, as indicated by a reduced RD, in OA limb muscles was substantial.

Hip, thigh and calf muscle atrophy and bone loss after 5-week bedrest inactivity

Unloaded inactivity induces atrophy and functional deconditioning of skeletal muscle, especially in the lower extremities. Information is scarce, however, regarding the effect of unloaded inactivity on muscle size and function about the hip. Regional bone loss has been demonstrated in hips and knees of elderly orthopaedic patients, as quantified by computerized tomography (CT). This method remains to be validated in healthy individuals rendered inactive, including real or simulated weightlessness. In this study, ten healthy males were subjected to 5 weeks of experimental bedrest and five matched individuals served as ambulatory controls. Maximum voluntary isometric hip and knee extension force were measured using the strain gauge technique. Cross-sectional area (CSA) of hip, thigh and calf muscles, and radiological density (RD) of the proximal tibial bone were measured using CT. Bedrest decreased (P < 0.05) average (SD) muscle strength by 20 (8)% in knee extension, and by 22 (12)% in hip extension. Bedrest induced atrophy (P < 0.05) of extensor muscles in the gluteal region, thigh and calf, ranging from 2 to 12%. Atrophy was more pronounced in the knee extensors [9 (4)%] and ankle plantar flexors [12 (3)%] than in the gluteal extensor muscles [2 (2)%]. Bone density of the proximal tibia decreased (P < 0.05) by 3 (2)% during bedrest. Control subjects did not show any temporal changes in muscle or bone indices (P > 0.05), when examined at similar time intervals. The present findings of a substantial loss in hip extensor strength and a smaller, yet significant atrophy of these muscles, demonstrate that hip muscle deconditioning accompanies losses in thigh and calf muscle mass after bedrest. This suggests that comprehensive quantitative studies on impaired locomotor function after inactivity should include all joints of the lower extremity. Our results also demonstrate that a decreased RD, indicating bone mineral loss, can be shown already after 5 weeks of unloaded bedrest, using a standard CT technique.

Test methods to detect hip and knee muscle weakness and gait disturbance in patients with hip osteoarthritis

OBJECTIVE

To evaluate test methods for hip and knee muscle weakness and gait disturbance.

DESIGN

Test-retest.

SETTING

Orthopedic university clinic.

PARTICIPANTS

Ten young (age, 36+/-6 y) and 13 elderly (age, 69+/-8 y) healthy volunteers and 11 patients (age, 69+/-8 y) with unilateral hip osteoarthritis (OA) were tested for muscular strength. Twenty-five volunteers (age, 42+/-14 y) underwent gait analysis.

INTERVENTIONS

A dynamometer assessing maximal voluntary isometric force of hip and knee muscles and an optosensor walkway detecting limp were developed. Tests evaluated reproducibility and tolerance in patients with OA and elderly subjects.

MAIN OUTCOME MEASURES

Relative coefficient of variation (CV%) and force (in newtons).

RESULTS

CV% for unilateral strength measurements ranged from 7% to 12% for specific muscle groups. CV% for gait parameters ranged from 4% to 8%, except for the double-support phase. Tests were well tolerated, and no patient had to discontinue because of fatigue. Differences related to sex, age, and disease were detected.

CONCLUSIONS

Our dynamometer system provides reliable measurements of hip and knee muscle strength in young and old people, and variation is comparable to previous data. Our photocell technique for gait analysis is reliable in people with normal gait. Both methods are attractive because they are affordable, nonstationary, and easy to use.

Signal intensity of MR-images of thigh muscles following acute open- and closed chain kinetic knee extensor exercise – index of muscle use

Exercise-induced shifts in signal intensity (SI) of magnetic resonance (MR) images were examined to assess indirectly muscle use in closed- and open-chain knee extensor exercises. Eight men performed five sets of 8-12 repetitions in the leg press (LP) and the seated knee extension (KE) exercises at 50, 75 and 100%, respectively of the 5 x 10 repetition maximum (RM) load. Prior to exercise and after each load setting, images of the thigh were obtained. The increase in SI (Delta SI) of the quadriceps at 100% load was greater (P < 0.05) after KE (32.1 +/- 9.0%) than after LP (21.9 +/- 9.2%). Regardless of load, the four individual muscles of the quadriceps showed similar changes in SI after LP. The three vastii muscles showed comparable increases in SI after KE. M. rectus femoris showed greater (P < 0.05) Delta SI than the vastii muscles at 100%. Neither exercise produced increase in SI of mm. semimembranosus, semitendinosus, gracilis or biceps femoris. Mm. adductor magnus and longus showed increased (13.3 +/- 6.5%; P < 0.05) SI after LP, but not after KE, at 100% load. The present data also infer greater involvement of the quadriceps muscle in the open-chain knee extension than in the closed-chain leg press exercise. The results of the current investigation also indicate similar over-all use among the three vastii muscles in LP and KE, but differential m. rectus femoris use between the two exercises. This report extends the merits of the MR imaging technique as an aid to study individual muscle involvement in a particular exercise task.

Effects of 17-day spaceflight on knee extensor muscle function and size

It is generally held that space travelers experience muscle dysfunction and atrophy during exposure to microgravity. However, observations are scarce and reports somewhat inconsistent with regard to the time course, specificity and magnitude of such changes. Hence, we examined four male astronauts (group mean approximately 43 years, 86 kg and 183 cm) before and after a 17-day spaceflight (Space Transport System-78). Knee extensor muscle function was measured during maximal bilateral voluntary isometric and iso-inertial concentric, and eccentric actions. Cross-sectional area (CSA) of the knee extensor and flexor, and gluteal muscle groups was assessed by means of magnetic resonance imaging. The decrease in strength (P<0.05) across different muscle actions after spaceflight amounted to 10%. Eight ambulatory men, examined on two occasions 20 days apart, showed unchanged (P>0.05) muscle strength. CSA of the knee extensor and gluteal muscles, each decreased (P<0.05) by 8%. Knee flexor muscle CSA showed no significant (P>0.05) change. The magnitude of these changes concord with earlier results from ground-based studies of similar duration. The results of this study, however, do contrast with the findings of no decrease in maximal voluntary ankle plantar flexor force previously reported in the same crew.

Effects of strength training, using a gravity-independent exercise system, performed during 110 days of simulated space station confinement

The efficacy of a resistance exercise paradigm, using a gravity-independent flywheel principle, was examined in four men subjected to 110 days of confinement (simulation of flight of international crew on space station; SFINCSS-99). Subjects performed six upper- and lower-body exercises (calf raise, squat, back extension, seated row, lateral shoulder raise, biceps curl) 2-3 times weekly during the confinement. The exercise regimen consisted of four sets of ten repetitions of each exercise at estimated 80-100% of maximal effort. Work was measured and recorded in each exercise session. Maximal voluntary isometric force in the calf press, squat and back extension, was assessed at three different joint angles before and after confinement. Overall, the training load (work) increased in all subjects (range 16-108%) over the course of the intervention. Maximal voluntary isometric force was unchanged following confinement. Although the perceived level of strain and comfort varied between exercises and among individuals, the results of the present study suggest this resistance exercise regimen is effective in maintaining or even increasing performance and maximal force output during long-term confinement. These findings should be considered in the design of resistance exercise hardware and prescriptions to be employed on the International Space Station.

Maximal instantaneous muscular power after prolonged bed rest in humans

A reduction in lower limb cross-sectional area (CSA) occurs after bed rest (BR). This should lead to an equivalent reduction in maximal instantaneous muscular power (W(p)) if the body segments' lengths remain unchanged. W(p) was determined during maximal jumps off both feet on a force platform before and on days 2, 6, 10, 32, and 48 after a 42-day duration BR. CSA of thigh muscles was measured by magnetic resonance imaging before and on day 5 after BR. Before BR, W(p) was 3.63 +/- 0.43 kW or 48.6 +/- 3.3 W/kg. On days 2 and 6 after BR, W(p) was reduced by 23.7 +/- 6.9 and 22.7 +/- 5.4% (P < 0.01), respectively. Thigh extensors CSA (CSAEXT) was 16.7 +/- 4.7% (P < 0.01) lower than before. When normalized per CSAEXT, W(p) was reduced by only 4.8 +/- 4.5% (P < 0.05). By day 48 of recovery, W(p) had returned to baseline values. Therefore, if W(p) is appropriately normalized for CSA of the extensor muscles, the reduction in CSAEXT explains most of the decrease in W(p) decrease after BR. Other factors such as a deficit in neural activation or a decrease in fiber-specific tension may account for only 5% of the W(p) loss after BR.

Quadriceps EMG/force relationship in knee extension and leg press

PURPOSE

This study compared the relationship between surface electromyographic (EMG) activity and isometric force of m. quadriceps femoris (QF) in the single-joint knee extension (KE) and the multi-joint leg press (LP) exercises.

METHODS

Nine healthy men performed unilateral actions at a knee angle of 90 degrees at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC). EMG was measured from m. vastus lateralis (VL), m. vastus medialis (VM), m. rectus femoris (RF), and m. biceps femoris (BF).

RESULTS

There were no differences in maximum EMG activity of individual muscles between KE and LP. The QF EMG/force relationship was nonlinear in each exercise modality. VL showed no deviation from linearity in neither exercise, whereas VM and RF did. BF activity increased linearly with increased loads.

CONCLUSIONS

The EMG/force relationship of all quadricep muscles studied appears to be similar in isometric multi-joint LP and single-joint KE actions at a knee angle of 90 degrees. This would indicate the strategy of reciprocal force increment among muscles involved is comparable in the two models. Furthermore, these data suggest a nonuniform recruitment pattern among the three superficial QF muscles and surface EMG recordings from VL to be most reliable in predicting force output.

Muscle control in elite alpine skiing

PURPOSE

The purpose of this study was to determine whether muscle control may be influenced by accelerative forces brought about by the downhill displacement of body mass in combination with the sharp turns during alpine skiing.

METHODS

Sixteen elite skiers performed either super G (SG), giant slalom (GS), slalom (SL), or freestyle mogul (FM) skiing. Knee and hip joint angles and electromyographic (EMG) activity of the knee extensors were recorded.

RESULTS

During the course of a turn, the minimum (deepest stance position) knee angle of the outside (main load-bearing) leg ranged from 60 degrees to 100 degrees, where the smallest angle was obtained in the FM event. Among the traditional alpine disciplines, smaller knee angles were obtained in the high-speed events (i.e., knee angle: SG<GS<SL). Knee angular velocity of the outside leg ranged from 15 degrees to 300 degrees x s(-1), with the slower movements in the high-speed disciplines (i.e., knee angular velocity: SG<GS<SL<FM). In all disciplines, EMG activity reached near-maximal levels during the course of a turn. In SG, GS, and SL, but not in FM skiing, a marked predominance of eccentric over concentric muscle actions was observed. The dominance of slow eccentric muscle actions has not been observed in other athletic activities.

CONCLUSIONS

We believe these results have important implications for the design of specific training models.

The effect of unloading on protein synthesis in human skeletal muscle

Atrophy of skeletal muscle is observed in response to immobilization and lack of weight-bearing. The aim of this study was to investigate the effect of immobilization on muscle protein synthesis and associated biochemical parameters in skeletal muscle of healthy volunteers employing a standardized model of lower limb unloading. One leg was unloaded for 10 days, and percutaneous muscle biopsies were taken before and at the end of the unloading period. The capacity for protein synthesis, as reflected by the concentration of RNA, decreased by 16% (P < 0.05) although the fractional synthesis rate (FSR) of protein was not significantly changed after 10 days of unloading. Furthermore there was an increase in the concentration of the free branched chain amino acids in muscle by 48% (P < 0.05).

Force and power characteristics of a resistive exercise device for use in space

We have developed a non-gravity dependent mechanical device, which provides resistance during coupled concentric and eccentric muscle actions, through the inertia of a spinning fly-wheel (Fly-Wheel Ergometry; FWE). Our research shows that lower-limb FWE exercise can produce forces and thus muscular stress comparable to what is typical of advanced resistance training using free weights. FWE also offers greater training stimuli during eccentric relative to concentric muscle actions, as evidenced by force and electromyographic (EMG) measurements. Muscle use of specific muscle groups, as assessed by the exercise-induced contrast shift of magnetic resonance images, is similar during lower-limb FWE and the barbell squat. Unlike free-weight exercise, FWE allows for maximal voluntary effort in each repetition of an exercise bout. Likewise, FWE exercise, not unassisted free-weight exercise, produces eccentric "overload". Collectively, the inherent features of this resistive exercise device and the results of the physiological evaluations we have performed, suggest that resistance exercise using FWE could be used as an effective exercise counter-measure in space. The flywheel principle can be employed to any exercise configuration and designed into a compact device allowing for exercises stressing those muscles and bone structures, which are thought to be most affected by long-duration spaceflight.

Lower limb skeletal muscle function after 6 wk of bed rest

Force, electromyographic (EMG) activity, muscle mass, and fiber characteristics were studied in seven healthy men before and after 6 wk of bed rest. Maximum voluntary isometric and concentric knee extensor torque decreased (P < 0.05) uniformly across angular velocities by 25-30% after bed rest. Maximum quadricep rectified EMG decreased by 19 +/- 23%, whereas submaximum (100-Nm isometric action) EMG increased by 44 +/- 28%. Knee extensor muscle cross-sectional area (CSA), assessed by using magnetic resonance imaging, decreased by 14 +/- 4%. Maximum torque per knee extensor CSA decreased by 13 +/- 9%. Vastus lateralis fiber CSA decreased 18 +/- 14%. Neither type I, IIA, and IIB fiber percentages nor their relative proportions of myosin heavy chain (MHC) isoforms were altered after bed rest. Because the decline in strength could not be entirely accounted for by using decreased muscle CSA, it is suggested that the strength loss is also due to factors resulting in decreased neural input to muscle and/or reduced specific tension of muscle, as evidenced by decreased torque/EMG ratio. Additionally, it is concluded that muscle unloading in humans does not induce important changes in fiber type or MHC composition or in vivo muscle contractile properties.

Lower limb skeletal muscle function after 6 wk of bed rest

Force, electromyographic (EMG) activity, muscle mass, and fiber characteristics were studied in seven healthy men before and after 6 wk of bed rest. Maximum voluntary isometric and concentric knee extensor torque decreased (P < 0.05) uniformly across angular velocities by 25-30% after bed rest. Maximum quadricep rectified EMG decreased by 19 +/- 23%, whereas submaximum (100-Nm isometric action) EMG increased by 44 +/- 28%. Knee extensor muscle cross-sectional area (CSA), assessed by using magnetic resonance imaging, decreased by 14 +/- 4%. Maximum torque per knee extensor CSA decreased by 13 +/- 9%. Vastus lateralis fiber CSA decreased 18 +/- 14%. Neither type I, IIA, and IIB fiber percentages nor their relative proportions of myosin heavy chain (MHC) isoforms were altered after bed rest. Because the decline in strength could not be entirely accounted for by using decreased muscle CSA, it is suggested that the strength loss is also due to factors resulting in decreased neural input to muscle and/or reduced specific tension of muscle, as evidenced by decreased torque/EMG ratio. Additionally, it is concluded that muscle unloading in humans does not induce important changes in fiber type or MHC composition or in vivo muscle contractile properties.

Effects of removal of weight-bearing function on contractility and myosin isoform composition in single human skeletal muscle cells

The purpose of this study was to investigate the effects of a 6-week period without weight bearing, achieved by bed rest, on the contractile behaviour, myosin isoform expression and myofibrillar protein content of single human muscle fibres. Percutaneous biopsied specimens of the quadriceps muscle were taken from three healthy male volunteers before and at the end of the experimental period. Maximum force normalised to cross-sectional area (specific tension), maximum velocity of unloaded shortening (V0), and myosin heavy chain (MyHC) and light chain (MyLC) isoform composition were measured in single membrane-permeabilised muscle cells obtained from these specimens. At the end of the experimental period, specific tension was reduced (P < 0.001) by 40% and there was a parallel decline in myofibrillar protein content per muscle cell volume. V0 did not change significantly in response to bed rest when data from all muscle cells were pooled. In two of the subjects, however, V0 decreased (P < 0.01-0.001) in muscle cells expressing the beta/slow (type I) MyHC isoform, but there was no change in fibres expressing type IIA or a combination of type IIA and IIB MyHCs. The slowing in type I MyHC fibres was associated with a change in the isoform composition of the regulatory MyLC.

Changes in muscle function in response to 10 days of lower limb unloading in humans

Force-generating capacity and electromyographic (EMG) activity of the knee extensor muscles were studied before and after short-term (10 d) unilateral lower limb unloading and during 4 days of recovery. Ten healthy males used crutches to prevent one of their lower limbs from weight-bearing while maintaining joint mobility as well as daily ambulatory activities. Knee extensor torque and quadriceps rectified EMG during maximal voluntary isometric contraction (MVC) was measured repeatedly before and after the intervention. Also, EMG at a fixed submaximal level (100 Nm; 30-45% MVC) and maximal angular velocity (AVmax), during unresisted knee extension, were assessed. Maximum torque decreased (P < 0.05) by 13 +/- 8% in response to unloading while maximum EMG activity did not change after unloading or during recovery (P = 0.35). Submaximum EMG increased (P < 0.05) by 25 +/- 16% after unloading. Maximum and submaximum torque/EMG ratio decreased (P < 0.05) after unloading. AVmax decreased (P < 0.05) by 9 +/- 8% after unloading. The post value, however, was not different from that of the weight-bearing limb. Torque, EMG and AVmax were recovered (P > 0.05) after 4 days of resumed weight-bearing. The pronounced decrease and the rapid recovery in maximum torque appears not to be attributed to a change in muscle mass alone. Because the findings of unchanged maximum EMG and increased EMG at a submaximal force level suggest no change in neural drive, we propose that unspecific tissue factors in part impair muscle function in response to short-term loss of weight-bearing activity. Results also indicate that recovery in muscle function after short-term unloading seems to be completed in a time span shorter than the period of preceding inactivity.

Involvement of eccentric muscle actions in giant slalom racing

Joint angular movements and muscle activation (EMG), were determined in male elite racers while performing the giant slalom. Movement cycles averaged 3.5 +/- 0.6 s (left plus right turn), and knee angle ranged 66-114 degrees (180 degrees = straight leg). Knee extensor muscle use was dominated (rectified EMG; P < 0.05) by the leg controlling the outside (downhill) ski during the turn. Time spent while decreasing knee angle (eccentric muscle action) of outside leg averaged 1.0 +/- 0.2 s. This phase was longer (P < 0.05) than the average push-off (concentric muscle action) phase of 0.5 +/- 0.1 s. Moreover, EMG activity of the outside leg during eccentric muscle actions exceeded (P < 0.05) that of concentric actions and was similar to that attained during maximum isometric knee extension in laboratory tests. Knee and hip angular movement ranged 20-50 degrees. Average joint velocities equalled 20-40 degrees.s(-1) during the turning phase. Thus, competitive giant slalom skiing is dominated by slow eccentric muscle actions performed at near maximum voluntary force. Because of their greater ability to generate force, eccentric muscle actions may be warranted or even required to resist the G-forces induced during the turn phase.

A gravity-independent ergometer to be used for resistance training in space

An ergometer, to be used for resistance training in space, has been developed and validated. It is designed to activate the extensor muscles of the knee and ankle joints while performing the leg press exercise. Resistance is provided independent of gravity by using the inertial focus of a flywheel. Eleven men performed two series of consecutive maximal voluntary concentric and eccentric muscle actions. Force, power, work and electromyographic (EMG) activity, measured during exercise on this ergometer and a traditional leg press resistive apparatus were similar. This mechanical ergometer seems to meet the operational and technical requirements of equipment that can be flown and used in space. Also, the physiological responses to acute exercise suggest that adaptations similar to those achieved by traditional weight training can be produced. Exercise using the inertia ergometer would, therefore, probably also be effective in combating the muscle atrophy and loss of strength that occur in microgravity.

Dynamic neck strength training effect on pain and function

This study examined whether neck resistance training could increase strength and reduce pain in workers with a high prevalence of neck disorders. Middle-aged women workers (n = 17) exercised twice weekly for 8 weeks. Each session (12min) consisted of three sets of 12 repetitions of resisted rotation, flexion, and extension muscles using hydraulic dampers. Resistance was set individually and progressively increased every second week. Angle-specific maximal isometric rotator, extensor, and flexor torque was measured before and after training. Torque during rotation, flexion and extension increased (p < .05) on average 35%, 27%, and 19%, respectively, after training. Perceived pain, assessed using a four-graded scale, was reduced (p < .05) after training. It is suggested that 12 minutes of specific neck strength training twice weekly for 8 weeks increases strength of rotator, extensor, and flexor muscles of the neck. Also all individuals who had pain reported reduced perceived neck pain after training.

Changes in lower limb muscle cross-sectional area and tissue fluid volume after transition from standing to supine

Lower limbs show acute fluid shift in response to transition from upright to supine body position. It is hypothesized that this would affect tomographic estimations of muscle mass and composition. Seven healthy subjects were investigated during the initial 120 min of bed rest, using repeated computerized tomography (CT) and continuous bioelectrical impedance analysis (BIA). Thigh and calf muscle cross-sectional area (CSA) decreased (P < 0.05) by 1.9 and 5.5% whereas fat CSA decreased (P < 0.05) by 4.1 and 4.4%, respectively. Radiological density (RD) of muscle showed a simultaneous increase (P < 0.05) by 4.8% in calf but not (P > 0.05) in thigh. No changes occurred (P > 0.05) in muscle or fat CSA or muscle RD in either thigh or calf between the first and second hour of bed rest. Fluid shift, as estimated by BIA, showed an exponential decay in thigh (tau th = 30 min) and calf (tau c2 = 37 min) by 2.5 and 8.7%, respectively, from first to 120 min of bed rest. Moreover, the calf showed an initial rapid (tau c1 = 8 s) 2.2% decrease. The demonstrated short-term changes in leg CSA were more pronounced in the calf than in the thigh. They were similar in muscle and subcutaneous fat. These fluid shifts merit consideration when tomographic imaging techniques are used to estimate muscle mass and composition.

Work capacity and metabolic and morphologic characteristics of the human quadriceps muscle in response to unloading

The response of skeletal muscle to unweighting was studied in six healthy males who were subjected to four weeks of lowerlimb suspension. They performed three bouts of 30 consecutive maximal concentric knee extensions, before unloading and the day after (POST 1), 4 days after (POST 2) and 7 weeks after (REC) resumed weight-bearing. Peak torque of each contraction was recorded and work was calculated as the mean of the average peak torque for the three bouts and fatigability was measured as the decline in average peak torque over bouts. Needle biopsies were obtained from m. vastus lateralis of each limb before and at POST 1. Muscle fibre type composition and area, capillarity and the enzyme activities of citrate synthase (CS) and phosphofructokinase (PFK) were subsequently analysed. Mean average peak torque for the three bouts at POST1, POST2 and REC was reduced (P < 0.05) by 17, 13 and 7%, respectively. Fatigability was greater (P < 0.05) at POST2 than before unloading. Type I, IIA and IIB percentage, Type I and II area and capillaries per fibre of Type I and II did not change (P > 0.05) in response to unloading. The activity of CS, but not PFK, decreased (P < 0.05) after unloading. The weight-bearing limb showed no changes in the variables measured. The results of this study suggest that this human lowerlimb suspension model produces substantial impairments of work and oxidative capacity of skeletal muscle. The performance decrements are most likely induced by lack of weight-bearing.