Calcaneotalar ratio: a new concept in the estimation of the length of the calcaneus.

Maintaining the calcaneal length after calcaneal fractures is vital to restoring the normal biomechanics of the foot, because it acts as an important lever arm to the plantarflexors of the foot. However, estimation of the length of the calcaneus to be reconstructed in comminuted calcaneal fractures can be difficult. We propose a new method to reliably estimate the calcaneal length radiographically by defining the calcaneotalar length ratio. A total of 100 ankle radiographs with no fracture in the calcaneus or talus taken in skeletally mature patients were reviewed by 6 observers. The anteroposterior lengths of the calcaneus and talus were measured, and the calcaneotalar length ratio was determined. The ratio was then used to estimate the length of the calcaneus. Interobserver reliability was determined using Cronbach's α coefficient and Pearson's correlation coefficient. The mean length of the calcaneus was 75 ± 0.6 mm, and the mean length of the talus was 59 ± 0.5 mm. The calcaneotalar ratio was 1.3. Using this ratio and multiplying it by the talar length, the mean average estimated length of the calcaneus was within 0.7 mm of the known calcaneal length. Cronbach's α coefficient and Pearson's correlation coefficient showed excellent interobserver reliability. The proposed calcaneotalar ratio is a new and reliable method to radiographically estimate the normal length of the calcaneus when reconstructing the calcaneus.

Surgical stabilisation in equivocal pelvic ring injuries - Into the grey zone.

Pelvic ring injuries comprise a spectrum of bony, ligamentous and muscular injuries, described by several common classification systems. However, the majority of injuries lie in areas of intermediate severity, where complexity and variable nature make it extremely hard to define in detail. This fact and associated injuries make it extremely difficult to conduct randomised control trials, with purpose to direct treatment guidelines. Thus, special interest and expertise are required by pelvic trauma surgeons, while surgical indications and fixation methods rely on their experience, at least in part. Namely, a significant grey zone of indication exists. As fixation methods evolve, specifically percutaneous fixation using osseous fixation pathways, some injuries in which morbidity bound with surgical fixation was considered too high relative to its benefits, may be considered eligible for surgical treatment nowadays. Moreover, due to significant progress in the treatment of the acute polytrauma casualties, the survival rate increased over the years, emphasizing the effect of long-term morbidity and functional outcome of pelvic ring injuries. The purpose of this manuscript is to describe the equivocal areas of controversies, hence "the grey zone", and to provide the readership with up-to-date published data. We aimed to collect and detail clinical and radiological clues in the diagnosis of intermediate unstable anterior-posterior compression and lateral compression injuries, and for the selection of treatment methods and sequence. Recent publications have provided some insights into specific injury features that are correlated with increased chance of instability, pain and delay in ambulation. Specific focus is given to the utility of examination under anaesthesia in selected cases. Other publications surveyed the shared experience of pelvic trauma surgeons as for the classification, indication and treatment sequence of pelvic ring injuries. Although the data hasn't matured yet to a comprehensive treatment algorithm, it may serve clinicians well when making treatment decisions in the grey zone of pelvic ring injuries, and serve as a basis for future prospective studies.

Effect of exercise intensity on skeletal muscle AMPK signaling in humans.

The effect of exercise intensity on skeletal muscle AMP-activated protein kinase (AMPK) signaling and substrate metabolism was examined in eight men cycling for 20 min at each of three sequential intensities: low (40 +/- 2% VO(2) peak), medium (59 +/- 1% VO(2) peak), and high (79 +/- 1% VO(2) peak). Muscle free AMP/ATP ratio only increased at the two higher exercise intensities (P < 0.05). AMPK alpha 1 (1.5-fold) and AMPK alpha 2 (5-fold) activities increased from low to medium intensity, with AMPK alpha 2 activity increasing further from medium to high intensity. The upstream AMPK kinase activity was substantial at rest and only increased 50% with exercise, indicating that, initially, signaling through AMPK did not require AMPK kinase posttranslational modification. Acetyl-CoA carboxylase (ACC)-beta phosphorylation was sensitive to exercise, increasing threefold from rest to low intensity, whereas neuronal NO synthase (nNOS) micro phosphorylation was only observed at the higher exercise intensities. Glucose disappearance (tracer) did not increase from rest to low intensity, but increased sequentially from low to medium to high intensity. Calculated fat oxidation increased from rest to low intensity in parallel with ACC beta phosphorylation, then declined during high intensity. These results indicate that ACC beta phosphorylation is especially sensitive to exercise and tightly coupled to AMPK signaling and that AMPK activation does not depend on AMPK kinase activation during exercise.

Creatine supplementation reduces muscle inosine monophosphate during endurance exercise in humans.

INTRODUCTION: Creatine (Cr) supplementation has been shown to attenuate increases in plasma ammonia and hypoxanthine during intense endurance exercise lasting 1 h, suggesting that Cr supplementation may improve muscle energy balance (matching of ATP resynthesis to ATP demand) during such exercise. We hypothesized that Cr supplementation would improve muscle energy balance (as assessed by muscle inosine monophosphate (IMP) accumulation) during intense endurance exercise. METHODS: Seven well-trained men completed two experimental trials involving approximately 1 h of intense endurance exercise (cycling 45 min at 78+/-1% & OV0312;O2 peak followed by completion of 251+/-6 kJ as quickly as possible (performance ride)). Subjects ingested approximately 42 g.d dextrose for 5 d before the first experimental trial (CON), then approximately 21 g Cr monohydrate plus approximately 21 g.d dextrose for 5 d before the second experimental trial (CREAT). Trials were ordered because of the long washout time for Cr. Subjects were blinded to the order of the trials. RESULTS: Creatine supplementation significantly (P< 0.05) increased muscle total Cr (resting values: CREAT: 138.1+/-7.9; CON: 117.7+/- 6.5 mmol.kg dm). No difference was seen between treatments in any measured muscle or blood metabolite after the first 45 min of exercise. Despite the performance ride completion time being similar in the two treatments ( approximately 13.5 min, approximately 86% & OV0312;O2 peak), IMP at the end of the performance ride was significantly (P<0.05) lower in CREAT than in CON (CREAT: 1.2+/- 0.6; CON: 2.0+/- 0.7 mmol.kg dm). CONCLUSION: Raising muscle total Cr content before exercise appears to improve the ability of the muscle to maintain energy balance during intense aerobic exercise, but not during more moderate exercise intensities.

Effect of sodium bicarbonate on muscle metabolism during intense endurance cycling.

INTRODUCTION: Sodium bicarbonate (NaHCO3) ingestion has been shown to increase both muscle glycogenolysis and glycolysis during brief submaximal exercise. These changes may be detrimental to performance during more prolonged, exhaustive exercise. This study examined the effect of NaHCO3 ingestion on muscle metabolism and performance during intense endurance exercise of approximately 60 min in seven endurance-trained men. METHODS: Subjects ingested 0.3 g.kg-1 body mass of either NaHCO3 or CaCO3 (CON) 2 h before performing 30 min of cycling exercise at 77 +/- 1% .VO(2peak) followed by completion of 469 +/- 21 kJ as quickly as possible (approximately 30 min, approximately 80% .VO(2peak)). RESULTS: Immediately before, and throughout exercise, arterialized-venous plasma HCO3- concentrations were higher (P < 0.05) whereas plasma and muscle H+ concentrations were lower (P < 0.05) in NaHCO3 compared with CON. Blood lactate concentrations were higher (P < 0.05) during exercise in NaHCO3, but there was no difference between trials in muscle glycogen utilization or muscle lactate content during exercise. Reductions in PCr and ATP and increases in muscle Cr during exercise were also unaffected by NaHCO3 ingestion. Accordingly, exercise performance time was not different between treatments. CONCLUSION: NaHCO3 ingestion resulted in a small muscle alkalosis but had no effect on muscle metabolism or intense endurance exercise performance in well-trained men.

Skeletal muscle nNOS mu protein content is increased by exercise training in humans.

The major isoform of nitric oxide synthase (NOS) in skeletal muscle is the splice variant of neuronal NOS, termed nNOS mu. Exercise training increases nNOS mu protein levels in rat skeletal muscle, but data in humans are conflicting. We performed two studies to determine 1) whether resting nNOS mu protein expression is greater in skeletal muscle of 10 endurance-trained athletes compared with 11 sedentary individuals (study 1) and 2) whether intense short-term (10 days) exercise training increases resting nNOS mu protein (within whole muscle and also within types I, IIa, and IIx fibers) in eight sedentary individuals (study 2). In study 1, nNOS mu protein was approximately 60% higher (P < 0.05) in endurance-trained athletes compared with the sedentary participants. In study 2, nNOS mu protein expression was similar in types I, IIa, and IIx fibers before training. Ten days of intense exercise training significantly (P < 0.05) increased nNOS mu protein levels in types I, IIa, and IIx fibers, a finding that was validated by using whole muscle samples. Endothelial NOS and inducible NOS protein were barely detectable in the skeletal muscle samples. In conclusion, nNOS mu protein expression is greater in endurance-trained individuals when compared with sedentary individuals. Ten days of intense exercise is also sufficient to increase nNOS mu expression in untrained individuals, due to uniform increases of nNOS mu within types I, IIa, and IIx fibers.

Short-term exercise training in humans reduces AMPK signalling during prolonged exercise independent of muscle glycogen.

We examined the effect of short-term exercise training on skeletal muscle AMP-activated protein kinase (AMPK) signalling and muscle metabolism during prolonged exercise in humans. Eight sedentary males completed 120 min of cycling at 66 +/- 1% , then exercise trained for 10 days, before repeating the exercise bout at the same absolute workload. Participants rested for 72 h before each trial while ingesting a high carbohydrate diet (HCHO). Exercise training significantly (P < 0.05) attenuated exercise-induced increases in skeletal muscle free AMP: ATP ratio and glucose disposal and increased fat oxidation. Exercise training abolished the 9-fold increase in AMPK alpha2 activity observed during pretraining exercise. Since training increased muscle glycogen content by 93 +/- 12% (P < 0.01), we conducted a second experiment in seven sedentary male participants where muscle glycogen content was essentially matched pre- and post-training by exercise and a low CHO diet (LCHO; post-training muscle glycogen 52 +/- 7% less than in HCHO, P < 0.001). Despite the difference in muscle glycogen levels in the two studies we obtained very similar results. In both studies the increase in ACCbeta Ser(221) phosphorylation was reduced during exercise after training. In conclusion, there is little activation of AMPK signalling during prolonged exercise following short-term exercise training suggesting that other factors are important in the regulation of glucose disposal and fat oxidation under these circumstances. It appears that muscle glycogen is not an important regulator of AMPK activation during exercise in humans when exercise is begun with normal or high muscle glycogen levels.