Carlos Barrios

Significant ventilatory functional restriction in adolescents with mild or moderate scoliosis during maximal exercise tolerance test.

Study Design. A prospective evaluation of cardiopulmonary tolerance to maximal exercise in adolescent idiopathic scoliosis. Objectives. To evaluate ventilatory functional restrictions during a maximal exercise tolerance test in idiopathic scoliosis patients with mild and moderate curves and to compare them with the results obtained in healthy adolescents matched in age undergoing similar test. Summary of Background Data. Adolescents with idiopathic scoliosis with mild curves do not exhibit significant restrictions in ventilatory parameters measured by conventional static spirometry. Few reports have dealt with cardiorespiratory response to maximal exercise in adolescent idiopathic scoliosis with mild to moderate curves. Although results seem to show a reduced exercise tolerance in these patients, the frequency and signification of the restricted work capacity is uncertain because of important design limitations in previous studies. Methods. Thirty-seven girls diagnosed with adolescent idiopathic scoliosis with a mean age of 13 years (range, 11–16) and an average scoliotic curve of 32.8° Cobb (range, 20–45°) were studied by basal spirometry and dynamic ventilatory parameters during a maximal exercise tolerance test. Similar studies were performed in a control group of 10 healthy girls matched in age. Exercise test consisted of a ramp protocol on treadmill starting at a speed of 0.75 m/second (2.7 km/hour) with increments of 0.2 m/second (0.72 km/hour) per minute. All subjects completed the test to exhaustion to determine maximal oxygen uptake (VO2 max) and ventilatory efficiency parameters. Results. There were no differences between scoliotic and healthy girls in basal ventilatory parameters (FVC, FEV1). However, adolescents with idiopathic scoliosis showed worse tolerance to exercise test with lower maximal speed average (9.4 km/hour versus 11.5 km/hour, P < 0.005), lower ventilatory efficiency at maximal exercise (VE: 68.9 L/minute versus 82.3 L/minute, P < 0.01), early anaerobic threshold, and a lower aerobic power expressed by 23% decreased body weight normalized VO2 max (38.6 mL/kg/minute versus 49.0 mL/kg/minute, P < 0.001). VEmax values were correlated to the severity of the scoliotic curve. Patients with more severe curves had greater limitation of ventilatory capacity (r = −0.374, P < 0.05). Maximal breath frequency was higher in scoliotic girls (54 versus 47, P < 0.05) suggesting a compensatory mechanism adopted in response to the lower ventilatory capacity during demanding exercise. When ventilatory efficiency was considered by the VE/VO2 ratio, scoliotic girls disclosed higher values than control (average 35.2 versus 29.6, P < 0.001) indicating an inefficiency in their ventilation. Patients wearing a brace at the time of ventilatory functional assessment did not exhibit any difference in the parameters investigated both at basal spirometry and during exercise tolerance test. Conclusion. Although patients with mild or moderate scoliosis do not exhibit cardiopulmonary restrictions in basal static conditions, they do show a significant lower tolerance to maximal exercise. Respiratory inefficiency together with lower ventilation capacity and lower VO2 max may be responsible for reduced exercise tolerance in adolescents with idiopathic scoliosis. Exercise deconditioning in scoliotic patients cannot be attributed to brace treatment.

9:37 Ventilatory functional restriction in adolescents with mild or moderate scoliosis during maximal exercise tolerance test

Abstract Purpose of study: To evaluate cardiopulmonary function during a maximal exercise tolerance test in patients with adolescent idiopathic scoliosis (AIS) with mild curves and compare to results obtained in healthy adolescents of the same age. Methods used: Twenty-three girls with AIS with an average age of 13.5 years (range, 10 to 16 years) and an average scolitic curve of 27 degrees Cobb (range, 20 to 45) were studied by basal spirometry and dynamic ventilatory parameters during a maximal exercise tolerance test. Similar studies were performed in a control group of five healthy girls matched in age. Exercise test consisted of a ramp protocol on treadmill starting at a speed of 0.75 m/sg (2.7 km/hour) with increments of 0.2 m/second (0.72 km/hour) per minute. The slope remained constant at 1.5%. During the test, girls move from walking to running on their own accord. All subjects completed the test to exhaustion to determine maximal oxygen uptake (VO 2 max). Electrocardiogram was continuously monitored during the tolerance exercise test. of findings: There were no differences between scoliotic and healthy girls in basal ventilatory parameters (FVC, FEV 1 ; Table 1 ) Table 1 . Exercise tolerance test FVC (l) Speedmax (km/h) HR max VEmax (l/min) VO 2 max (ml/ min/kg) AT (km/h) R (VCO 2 / VO 2 ) AIS patients 2.95 9.53 184 66.7 39.3 7.64 1.11 Controls 3.14 13.82 192 95.8 55.2 11.74 1.10 p value NS NS NS . Patients with AIS showed worse tolerance to exercise test with lower maximal speed average (31% lower than controls), lower ventilatory efficiency at maximal exercise (31% deficit), early anaerobic threshold and a lower aerobic power expressed by decreased body mass normalized VO 2 max (29% restriction). Heart rate and respiratory coefficient were similar in both groups, indicating that tolerance test was performed at similar maximal conditions.

Anthropometry and body composition profile of girls with nonsurgically treated adolescent idiopathic scoliosis.

Study Design. Cross-sectional study with level III of evidence. Objective. To describe different anthropometric and body composition parameters of adolescent girls with adolescent idiopathic scoliosis (AIS), comparing them with the standards of a healthy age-matched population. Summary of Background Data. Body growth and development of adolescent girls with AIS seems to differ from the healthy subjects, especially at perpubertal stages. Young scoliotic adults have been found to be taller, lighter, and thinner than age-matched healthy population. Body composition profile taken from measurements of skin-fold thickness, bony diameters at different levels, and arm and legs perimeters has not been previously reported in AIS patients. Methods. A nonconsecutive series of 52 AIS girls (mean age: 13.9 years) with an average scoliotic curve of 27° Cobb (range: 20–58) underwent an anthropometric study. None of the AIS girls had been treated previously with spinal surgery. The control group consisted of 92 girls without spine deformity, matched in age (mean: 13.8 years). Weight, height, and skin-fold thickness in millimeters at six levels were measured. Body mass index (BMI), Ponderal index, percentage of body fat, percentage of muscular tissue, fat mass, lean body mass, muscular weight, bony weight, and residual weight were calculated using standard rules to estimate body composition. The somatotype components (endomorphy, mesomorphy, and ectomorphy) were calculated according to the Carter equations. Results. Compared with the control population, scoliotic girls had a significantly lower mean weight (51.4 ± 10.2 kg vs. 54.7 ± 8.1 kg; P < 0,05), a lower BMI (20.1 ± 3.4 vs. 21.4 ± 2.4; P < 0.001), and a higher Ponderal index (43.2 ± 2.4 vs. 42.2 ± 1.6; P < 0.01). Girls with AIS showed a progressive decrease of the BMI as the age increased. The percentage of body fat was also lower in scoliotic girls, without significant statistical differences (14.1 ± 3.8 vs. 15 ± 3.6). Out of the 52 AIS girls, 11 (21.2%) showed a BMI below 17.5, which has been considered the limit for anorexia. In the control group, only 3 of 92 girls (3.3%) had BMI below that level. The somatotype differed also between scoliotics and controls: higher in the ectomorphic component (3.29 ± 1.68 vs. 2.40 ± 1.11; P < 0.001), and lower in the mesomorphic component (2.86 ± 0.82 vs. 3.70 ± 1.11; P < 0.01) in AIS patients. Conclusion. The differences in some anthropometric parameters (weight, IMC, IP) and in the somatotype suggest that the idiopathic scoliosis not only disturbs normal spine growth but also seems to have implications on the whole corporal development. Whether these changes could be related to abnormal spinal growth or subsequent to nutritional changes in AIS still remains uncertain. Presumably, some endocrine factors affecting body composition and growth might be involved in the etiology of idiopathic scoliosis.

Incidence and risk for traumatic and overuse injuries in top-level road cyclists

Abstract All traumatic and overuse injuries occurring during an average period of 4 years (2002/09) in a group of 51 currently active road top-level cyclists were retrospectively registered through clinical interviews. Average age was 25.8 years. Average training and competition period was 28.3 ± 2.4 h a week. Only 8 cyclists (15.6%) were completely free from lesions during the period of study. The remaining 43 cyclists suffered a total of 112 lesions; however, 9 out of these were unrelated to their cycling practice. These 103 cycling-related injuries include 50 (48.5%) traumatic and 53 (51.5%) overuse injuries. Twenty-eight fractures were reported, the clavicle being the most frequently affected bone (11 cases). The 68.5% of overuse injuries were located in the lower limbs. Most overuse injuries (89.6%) occurred during the training period. According to the Injury Abbreviated Scale (AIS), severe lesions were only found in 4 cases (8% of traumatic injuries). Overall injury rates were 0.50 per racer/year, 2.02 per studied racer, and 0.007 per 1,000 km of training and competition. Active professional top-level cyclists are exposed to a high injury risk. According to the scarce previously published data the current study provides relevant information on the injury occurrence of still active top-level road cycling.

Recording Diffusion Responses From Contralateral Intercostal Muscles After Stimulus-triggered Electromyography: Refining a Tool for the Assessment of Thoracic Pedicle Screw Placement in an Experimental Porcine Model

Study Design. A new stimulus-triggered electromyography (EMG) test for detecting stimulus diffusion to contralateral intercostal muscles during thoracic pedicle screw placement was assessed in a porcine model. Objective. To determine if electromyographic thresholds in the intercostal muscles of both sides of the thorax could discriminate thoracic pedicle screw malpositions with and without neural contact at different aspects of the spinal cord and nerve roots. Summary of Background Data. There is controversy about the value of triggered EMG stimulation for aiding precise insertion of thoracic pedicle screws. A universally validated threshold that confirms screw malposition has not been established. Diffusion of EMG responses to the contralateral intercostal muscles has not previously been investigated. Methods. Nine domestic pigs weighing 60 to 75 kg had 108 pedicle screws placed bilaterally in the thoracic spine from T8–T13. Before spine instrumentation, neural structures were stimulated in 4 animals under direct vision at different anatomic locations from T9–T12. Recording electrodes were placed over the right and left intercostal muscles. Increasing stimulus intensity was applied until muscle response was detected at the contralateral side (EMG diffusion phenomenon). After this first experiment, the thoracic spine was instrumented in all 9 animals. Screws were placed in the pedicle in different positions, the anatomic intrapedicular location and within the spinal canal, with and without contact with the neural elements. Results. Response thresholds to direct nerve root stimulation were significantly lower than those obtained by stimulation of the dorsal aspect of the spinal cord (0.44 ± 0.22 mA vs. 1.38 ± 0.71 mA, P < 0.01). However, a 14-fold stimulation intensity (6.50 ± 0.29 mA) was necessary to obtain diffusion of the EMG response to the opposite (left) side if the right nerve root was stimulated. A 2-fold increment (3.17 ± 0.93 mA) elicited diffusion of the EMG responses to the contralateral side when stimulation was applied to the dorsal aspect of the spinal cord. EMG recordings of the 108 stimulated screws showed a significant decrease in the EMG response when the screw was in contact with the spinal cord (2.72 ± 1.48 mA; P < 0.01) compared with that found when the pedicle track was intact (mean: 5.01 ± 1.89 mA). Screws violating the medial wall of the pedicle, but not touching neural tissues, responded to slightly lower intensities than well-positioned screws, but this was not statistically significant (3.91 ± 1.39 mA vs. 4.89 ± 1.30 mA, P > 0.05). Conclusion. Stimulus-triggered EMG can identify screws that violate the medial pedicle wall if they are in contact with neural tissues. EMG thresholds could not discriminate screws that violated the medial pedicle wall without neural contact from screws with accurate intraosseous placement. However, recording EMG potentials at the contralateral intercostal muscles (stimulus diffusion phenomenon) proved to be a reliable method for identifying the neural structures at risk.

Changes in sports injuries incidence over time in world-class road cyclists.

This is a descriptive epidemiologic survey on all traumatic and overuse injuries which occurred in 2 groups of male elite road cyclists based on retrospective clinical interviews and physical examinations. The historical group consisted of 65 professional road cyclists surveyed from 1983 to 1995. The contemporary group included 65 elite racers still active and reporting injuries from 2003 to 2009. Injury/cyclist ratio was 1.32 in the historical group and 2.13 in those still active. Traumatic injuries increased from 39.5% (historical) to 53.9% (contemporary) (p<0.05). Severe traumatic lesions decreased from 49.9% in the historical group to 10.5% in the contemporary group (p<0.01). Patellofemoral pain decreased from 28.8% (historical) to 6.1% (contemporary) (p<0.01). Muscle injuries substantially increased from 13.4% to 44.9% (p<0.01). In the historical racers, the rates of risk for traumatic injury were 0.104 per year per cyclist, and 0.003 per 1 000 km of training and competition. These figures increased to 0.287 and 0.009 respectively in the contemporary group. In summary, contemporary professional road cyclists are exposed to double the risk of traumatic injuries than those competing in the 80s and early 90s. However, these lesions have less severity. Overuse injuries had a completely different clinical pattern, with the currently active cyclist exhibiting more muscle injuries and less tendinous lesions.

Electromyographic thresholds after thoracic screw stimulation depend on the distance of the screw from the spinal cord and not on pedicle cortex integrity

BACKGROUND CONTEXT Present studies concerning the safety and reliability of neurophysiological monitoring during thoracic pedicle screw placement remain inconclusive, and therefore, universally validated threshold levels that confirm osseous breakage of the instrumented pedicles have not been properly established. PURPOSE The objective of this work was to analyze whether electromyographic (EMG) thresholds, after stimulation of the thoracic pedicle screw, depend on the distance between the neural structures and the screws. The modifier effect of different interposed tissues between a breached pedicle and neural structures was also investigated. STUDY DESIGN This experimental study uses a domestic pig model. METHODS Electromyographic thresholds were recorded after the stimulation of 18 thoracic pedicle screws that had been inserted into five experimental animals using varying distances between each screw and the spinal cord (8 and 2 mm). Electromyographic thresholds were also registered after the medial pedicle cortex was broken and after different biological tissues were interposed (blood, muscle, fat, and bone) between the screw and the spinal cord. RESULTS Mean EMG thresholds increased to 14.1±5.5 mA for screws with pedicle cortex integrity that were placed 8 mm away from the dural sac. After the medial pedicle cortex was broken and without varying the distance of the screw to the dural sac, the mean EMG thresholds were not appreciably changed (13.6±6.3 mA). After repositioning the screw at a distance of 2 mm from the spinal cord and after medial cortical breach of the pedicle, the mean threshold significantly slowed to 7.4±3.4 mA (p<.001). When the screw was placed in contact with the spinal dural sac, even lower EMG thresholds were registered (4.9±1.9, p<.001). Medial pedicle cortex rupture and the interposition of different biological tissues in experimental animals did not alter the stimulation thresholds of the thoracic pedicle screws. CONCLUSIONS In the experimental animals, the observed electrical impedance depended on the distance of screws from the neural structures and not on the integrity of the pedicle cortex. The screw-triggered EMG technique did not reliably discriminate the presence or absence of bone integrity after pedicle screw placement. The response intensity was not related to the type of interposed tissue.

Somatosensory cortectomy induces motor cortical hyperexcitability and scoliosis: an experimental study in developing rats

BACKGROUND CONTEXT Dysfunctions in sensorimotor integration, reminiscent to those described in idiopathic dystonia, have been found in idiopathic scoliosis (IS) and might be involved in its pathogenesis. Studying the effects of experimental disruption of sensory cortex may shed further insight into the etiopathology of IS. PURPOSE To evaluate whether disruption of central sensorimotor integration through partial ablation of the somatosensory cortex leads to scoliosis in developing rats and to describe the effects of such an intervention on motor cortico-cortical inhibition and facilitation. METHODS Fifty Wistar rats aged 3 weeks were used in the study. Twenty-four rats underwent craniotomy and electrocoagulation of the sensory cortex (PAR1) in the right hemisphere. A second group of 16 rats underwent a sham operation with craniotomy but no electrocoagulation. A third group of 10 rats was used as intact controls. Four weeks after surgery, motor cortical excitability was assessed with paired-pulse electrical cortical stimulation. Neurologic and behavioral examinations were completed serially, and 10 weeks after surgery, X-ray examinations were performed in anesthetized rats to assess spinal curvature. Electromyographic recordings of paravertebral muscle activity were performed in waking rats. At the end of the study, rats were sacrificed, and histologic examinations of brain tissue were performed to confirm the extent of the lesion. A grant from a Government Health Research Fund without salaries assignment financed the study. RESULTS Almost half of the animals with somatosensory cortectomy (46%) developed scoliosis, with an average Cobb angle of 23 ± 8°. None of the animals in the sham or control groups developed scoliosis. Despite cortical lesions, no motor or behavioral deficits were apparent in the experimental group, and cortectomized rats were neurologically indistinguishable from sham or control animals, except for the presence of scoliosis. Cortico-cortical inhibition was significantly reduced in the hemisphere of scoliotic concavity in the cortectomized group but was normal in the other groups. CONCLUSIONS These findings indicate that altered sensorimotor integration may cause scoliosis without noticeable motor impairment. Reduced cortico-cortical inhibition was observed in cortectomized rats. This finding is consistent with results in adolescents with IS and suggests that alteration of cortical hemispheric balance of sensorimotor integration may play an important role in the pathogenesis of IS.

Antioxidants and gabapentin prevent heat hypersensitivity in a neuropathic pain model.

ABSTRACT Background: The involvement of voltage-dependent calcium channels and reactive oxygen species in the pathophysiology of neuropathic pain might justify the preventative administration of antioxidant enzymes, at low doses, in combination with gabapentin (GaP) to maximize its analgesic effect in an experimental model of neuropathic pain in rats. Methods: This work investigated the analgesic effects of these drugs, alone or in combination, by intraperitoneal administration for three consecutive days before (Series I) or after (Series II) a peripheral neuropathy induced by left sciatic nerve ligation. A prospective randomized study was conducted using 96 Wistar rats (50 males and 46 females). Mechanical hypersensitivity was measured with a dynamic plantar anesthesiometer. A hot plate analgesia meter calculated the thermal sensitivity. Side effect profiles for drug combinations were evaluated with a conventional scale to assess levels of sedation interfering with postural control and righting reflexes. Results: Preinjury administration (Series I) of GaP alone prevented the development of mechanical hypersensitivity at the nerve-damage hind paw. When GaP was administered concurrently with superoxide dismutase and catalase, its preventive analgesic effect did not increase. Antioxidants administered alone were completely ineffective at modulating the mechanical or thermal hypersensitivity. When treatments were only delivered following surgery (Series II), only the group receiving combined GaP and antioxidants treatment prior to nerve injury showed higher thermal thresholds from postsurgery days 7–30. Conclusions: These results suggest that preventive antioxidants in combination with GaP provided a synergistic suppression of thermal hypersensitivity that GaP alone cannot produce.

Intraoperative Neurophysiological Changes Induced by Thoracic Pedicle Screws Intentionally Placed Within the Spinal Canal: An Experimental Study in Pigs

STUDY DESIGN Experimental study, OBJECTIVES: To document and analyze the neurophysiological changes during spinal cord monitoring when thoracic pedicle screws are intentionally placed within the spinal canal. SUMMARY OF BACKGROUND DATA Although the rate of misplaced screws is relatively high, few patients have neurological impairment. This suggests that a significant degree of medullary displacement and/or compression is necessary to produce neurophysiological changes. METHODS The spinal cord of 3 experimental pigs was surgically exposed at 3 different levels (T11, T9, and T6). Two pedicle screws were placed within the spinal canal at each vertebral level under direct vision. One was placed on the lateral edge of the dural sac, causing only a slight cord displacement; a second screw was placed in the middle of the spinal canal, producing marked displacement of the neural structures. During the procedure, neurophysiological monitoring of the spinal cord was performed. RESULTS No neurophysiological changes were observed in any screws placed at the lateral edge of the dural sac for 20 minutes after screw placement. When the screws were placed in the center of the spinal canal, neurophysiological changes occurred with a mean latency of 10.1 ± 2.1 minutes, and at 11.6 ± 1.9 minutes there was complete loss of the spinal cord evoked potentials in all cases. After these centered screws were removed, evoked potentials began to recover, with a latency of 9.7 ± 3.0 minutes in 7 of 9 cases. CONCLUSIONS Neurophysiological monitoring of the spinal cord does not detect moderate compression even 20 minutes after neural compression. Only thoracic pedicle screws provoking marked displacement of the spinal cord were able to cause delayed neurophysiological changes leading to loss of spinal cord evoked potentials, which in 22% of cases did not recover after the pedicle screw was removed.