Vikas Patel - Academia.edu (original) (raw)

Papers by Vikas Patel

Muscle & Nerve, 2009

Neuromuscular control of lumbar stability following exposure to prolonged static work, under low ... more Neuromuscular control of lumbar stability following exposure to prolonged static work, under low and high loads, was assessed in the in vivo feline model. Six sessions of 10 min work at 20N with 10 min between rest was compared to a group subjected to the same protocol but carrying high loads of 60N. Displacement and tension developed in the spine at the instant the multifidus muscles applied stabilizing contractions, and their amplitudes were obtained from their electromyogram (EMG). Significant (P Ͻ 0.001) laxity developed in the various viscoelastic tissues of the lumbar spine that did not recover during and up to 7 h of rest postwork. Simultaneously, there was a significant (P Ͻ 0.001) decrease in muscular activity in the 3-4 h immediately postwork under low load but only during the first hour in the high load group. After that period the musculature compensated for the laxity of the viscoelastic tissues by a significant (P Ͻ 0.001) increase in activity in the high-load group and a nonsignificant increase in the low group. It was concluded that during 1-3 h immediately poststatic work a significant decrease in the stabilizing function of viscoelastic tissues together with a significant decrease in muscular activity is present, and they render the spine unstable and exposed to high risk of injury. Performance of prolonged static work under low loads, while not harmful during the work, cannot be designated as a "no-risk" condition, as it may result in injury postwork.

Journal of Occupational & Environmental Medicine, 2007

Learning Objectives • Summarize what previous studies have shown about the effects of static load... more Learning Objectives • Summarize what previous studies have shown about the effects of static loading of the lumbar spine on regional viscoelastic tissues such as ligaments and intervertebral discs and on muscle tissue. • Explain how, in electromyographic studies of the lumbar spine in cats, the degree of cyclical (repetitive) loading influenced the magnitude and duration of delayed muscular hyperactivity. • Estimate the respective contributions of cyclical loading of the lumbar spine to acute and chronic inflammatory changes, and compare the effects of cyclical loading to those of static loading.

European Spine Journal, 2009

The motor control system may compensate for lumbar instability following cyclic work with differe... more The motor control system may compensate for lumbar instability following cyclic work with differential response to load magnitude. In vivo felines were exposed to a cumulative 1 h of cyclic work at 0.25 Hz. One group exposed to light whereas the second to heavy load while recording lumbar displacement and multifidus EMG during work and in single test cycles over 7 h rest post-work. Significant laxity and reduced reflexive EMG activity were evident immediately post-work in both groups. EMG and laxity recovered over 7 h rest in the group exposed to light load whereas in the group exposed to heavy load, motor control compensation was triggered within 1-2 h postwork. The compensation was expressed by earlier and stronger muscular activation than in baseline. It is concluded that cyclic work is deleterious to spine stability immediately after work. Work with heavy loads elicits delayed motor control compensation whereas work with light loads leaves the spine unstable and exposed to injury for several hours. Overall, prolonged cyclic or repetitive work elicits a transient instability disorder, regardless of the load handled, exposing the individual to potential injury.

Clinical Biomechanics, 2008

Background. The impact of six sequential static loading and rest of the lumbar spine on the chang... more Background. The impact of six sequential static loading and rest of the lumbar spine on the changes in the neuromuscular neutral zones and thereby on spine stability was assessed. Methods. Six 10 min sessions of static load of a moderate level each spaced by 10 min rest were applied to the in vivo feline model. Test cycles of 0.25 Hz and at the same moderate peak load were applied before and every hour after the static loading sequence up to 7 h. Load, displacement and electromyographic activity of the lumbar multifidi muscles were recorded throughout. Findings. Displacement and tension neuromuscular neutral zones were defined as the displacement or tension, in the increase and decrease phases of each cycle, when the electromyogram initiated and ceased activity, respectively. Displacement neuromuscular neutral zones demonstrated significant (P < 0.001) increase immediately post-static loading, followed by an exponential decrease to pre-loading baseline by the 7th hour. Tension neuromuscular neutral zones, however, demonstrated significant (P < 0.001) increase in the 2 h immediately after the static loading and a significant decrease (P < 0.001) thereafter. Peak electromyogram decreased in the first 3 h post-loading, but significantly (P < 0.001) increased thereafter to the 7th hour. Interpretation. It was concluded that the first 2-3 h post-static loading finds the spine with significant laxity in the viscoelastic tissues concurrently with deficient muscular activation and therefore exposed to the risk of instability. It is also evident that a neural control compensation mechanism exists where it enhances the activation of the musculature to earlier and at higher activation magnitude, 2-3 h post-loading, increasing lumbar stability while the viscoelastic tissues are still lax.

Scoliosis, 2015

Background: Osteotomies including pedicle subtraction (PSO) and/or Smith-Peterson (SPO) are used ... more Background: Osteotomies including pedicle subtraction (PSO) and/or Smith-Peterson (SPO) are used to facilitate surgical correction of adult spinal deformity (ASD), but are associated with complications including instrumentation failure and rod fracture (RF). The purpose of this study was to determine incidence and risk factors for RF, including a clinically significant subset (CSRF), after osteotomy for ASD. Methods: A retrospective review of clinical records was conducted on consecutive ASD patients treated with posterolateral instrumented fusion and osteotomy. Seventy-five patients (50 female; average age, 59) met strict inclusion/exclusion criteria and follow-up of ≥1 year. Data was extracted pertaining to the following variables: patient demographics; details of surgical intervention; instrumentation; and postoperative outcomes. Patients were divided into two subgroups: 1) rod fracture (RF) and 2) non-RF. The RF subgroup was further divided into CSRF and non-CSRF. Odds ratios (OR) were calculated to evaluate the association between risk factors and RF. The χ 2-test was used to define P-values for categorical variables, and T-test was applied for continuous variables, P-values ≤0.05 were considered significant.

Muscle & Nerve, 2008

Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulat... more Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulative trauma disorder (CTD), and the frequency or velocity of the movement is one of the risk factors. Experimental neurophysiological evidence to confirm the epidemiology is not available. The response of the multifidus muscles to cyclic loading in anterior lumbar flexion-extension was assessed to test the hypothesis that high-frequency loading may induce an acute neuromuscular disorder leading to CTD. Two groups of feline preparations were subjected to cyclic loading with a peak of 20 N: one at 0.25 HZ and the second at 0.5 HZ, with an equal number of cycles. Electromyogram (EMG), lumbar displacement and load were recorded throughout the loading periods and during single-cycle tests over a 7-hour rest period following the load-rest sessions. A model was developed to quantify the creep and neuromuscular responses, and analysis of variance (ANOVA) was applied to assess significance of the results. The group exposed to 0.5 HZ exhibited spontaneous spasms followed by sustained spasms during the loading periods. During the 7-hour recovery period, a significant (P Ͻ 0.001) delayed hyperexcitability as well as sustained spasms of the multifidi were present in the last 5 hours, confirming a significant (P Ͻ 0.024 to P Ͻ 0.042) acute neuromuscular disorder. Highfrequency cyclic loading of the lumbar spine may trigger a severe acute neuromuscular disorder, as evidenced by the sustained spasms and delayed hyperexcitability, and should be considered as a risk factor. We suggest that workers avoid high-frequency exposure to cyclic activity in order to prevent the development of cumulative trauma disorder.

Muscle & Nerve, 2009

Neuromuscular control of lumbar stability following exposure to prolonged static work, under low ... more Neuromuscular control of lumbar stability following exposure to prolonged static work, under low and high loads, was assessed in the in vivo feline model. Six sessions of 10 min work at 20N with 10 min between rest was compared to a group subjected to the same protocol but carrying high loads of 60N. Displacement and tension developed in the spine at the instant the multifidus muscles applied stabilizing contractions, and their amplitudes were obtained from their electromyogram (EMG). Significant (P Ͻ 0.001) laxity developed in the various viscoelastic tissues of the lumbar spine that did not recover during and up to 7 h of rest postwork. Simultaneously, there was a significant (P Ͻ 0.001) decrease in muscular activity in the 3-4 h immediately postwork under low load but only during the first hour in the high load group. After that period the musculature compensated for the laxity of the viscoelastic tissues by a significant (P Ͻ 0.001) increase in activity in the high-load group and a nonsignificant increase in the low group. It was concluded that during 1-3 h immediately poststatic work a significant decrease in the stabilizing function of viscoelastic tissues together with a significant decrease in muscular activity is present, and they render the spine unstable and exposed to high risk of injury. Performance of prolonged static work under low loads, while not harmful during the work, cannot be designated as a "no-risk" condition, as it may result in injury postwork.

Journal of Occupational & Environmental Medicine, 2007

Learning Objectives • Summarize what previous studies have shown about the effects of static load... more Learning Objectives • Summarize what previous studies have shown about the effects of static loading of the lumbar spine on regional viscoelastic tissues such as ligaments and intervertebral discs and on muscle tissue. • Explain how, in electromyographic studies of the lumbar spine in cats, the degree of cyclical (repetitive) loading influenced the magnitude and duration of delayed muscular hyperactivity. • Estimate the respective contributions of cyclical loading of the lumbar spine to acute and chronic inflammatory changes, and compare the effects of cyclical loading to those of static loading.

European Spine Journal, 2009

The motor control system may compensate for lumbar instability following cyclic work with differe... more The motor control system may compensate for lumbar instability following cyclic work with differential response to load magnitude. In vivo felines were exposed to a cumulative 1 h of cyclic work at 0.25 Hz. One group exposed to light whereas the second to heavy load while recording lumbar displacement and multifidus EMG during work and in single test cycles over 7 h rest post-work. Significant laxity and reduced reflexive EMG activity were evident immediately post-work in both groups. EMG and laxity recovered over 7 h rest in the group exposed to light load whereas in the group exposed to heavy load, motor control compensation was triggered within 1-2 h postwork. The compensation was expressed by earlier and stronger muscular activation than in baseline. It is concluded that cyclic work is deleterious to spine stability immediately after work. Work with heavy loads elicits delayed motor control compensation whereas work with light loads leaves the spine unstable and exposed to injury for several hours. Overall, prolonged cyclic or repetitive work elicits a transient instability disorder, regardless of the load handled, exposing the individual to potential injury.

Clinical Biomechanics, 2008

Background. The impact of six sequential static loading and rest of the lumbar spine on the chang... more Background. The impact of six sequential static loading and rest of the lumbar spine on the changes in the neuromuscular neutral zones and thereby on spine stability was assessed. Methods. Six 10 min sessions of static load of a moderate level each spaced by 10 min rest were applied to the in vivo feline model. Test cycles of 0.25 Hz and at the same moderate peak load were applied before and every hour after the static loading sequence up to 7 h. Load, displacement and electromyographic activity of the lumbar multifidi muscles were recorded throughout. Findings. Displacement and tension neuromuscular neutral zones were defined as the displacement or tension, in the increase and decrease phases of each cycle, when the electromyogram initiated and ceased activity, respectively. Displacement neuromuscular neutral zones demonstrated significant (P < 0.001) increase immediately post-static loading, followed by an exponential decrease to pre-loading baseline by the 7th hour. Tension neuromuscular neutral zones, however, demonstrated significant (P < 0.001) increase in the 2 h immediately after the static loading and a significant decrease (P < 0.001) thereafter. Peak electromyogram decreased in the first 3 h post-loading, but significantly (P < 0.001) increased thereafter to the 7th hour. Interpretation. It was concluded that the first 2-3 h post-static loading finds the spine with significant laxity in the viscoelastic tissues concurrently with deficient muscular activation and therefore exposed to the risk of instability. It is also evident that a neural control compensation mechanism exists where it enhances the activation of the musculature to earlier and at higher activation magnitude, 2-3 h post-loading, increasing lumbar stability while the viscoelastic tissues are still lax.

Scoliosis, 2015

Background: Osteotomies including pedicle subtraction (PSO) and/or Smith-Peterson (SPO) are used ... more Background: Osteotomies including pedicle subtraction (PSO) and/or Smith-Peterson (SPO) are used to facilitate surgical correction of adult spinal deformity (ASD), but are associated with complications including instrumentation failure and rod fracture (RF). The purpose of this study was to determine incidence and risk factors for RF, including a clinically significant subset (CSRF), after osteotomy for ASD. Methods: A retrospective review of clinical records was conducted on consecutive ASD patients treated with posterolateral instrumented fusion and osteotomy. Seventy-five patients (50 female; average age, 59) met strict inclusion/exclusion criteria and follow-up of ≥1 year. Data was extracted pertaining to the following variables: patient demographics; details of surgical intervention; instrumentation; and postoperative outcomes. Patients were divided into two subgroups: 1) rod fracture (RF) and 2) non-RF. The RF subgroup was further divided into CSRF and non-CSRF. Odds ratios (OR) were calculated to evaluate the association between risk factors and RF. The χ 2-test was used to define P-values for categorical variables, and T-test was applied for continuous variables, P-values ≤0.05 were considered significant.

Muscle & Nerve, 2008

Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulat... more Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulative trauma disorder (CTD), and the frequency or velocity of the movement is one of the risk factors. Experimental neurophysiological evidence to confirm the epidemiology is not available. The response of the multifidus muscles to cyclic loading in anterior lumbar flexion-extension was assessed to test the hypothesis that high-frequency loading may induce an acute neuromuscular disorder leading to CTD. Two groups of feline preparations were subjected to cyclic loading with a peak of 20 N: one at 0.25 HZ and the second at 0.5 HZ, with an equal number of cycles. Electromyogram (EMG), lumbar displacement and load were recorded throughout the loading periods and during single-cycle tests over a 7-hour rest period following the load-rest sessions. A model was developed to quantify the creep and neuromuscular responses, and analysis of variance (ANOVA) was applied to assess significance of the results. The group exposed to 0.5 HZ exhibited spontaneous spasms followed by sustained spasms during the loading periods. During the 7-hour recovery period, a significant (P Ͻ 0.001) delayed hyperexcitability as well as sustained spasms of the multifidi were present in the last 5 hours, confirming a significant (P Ͻ 0.024 to P Ͻ 0.042) acute neuromuscular disorder. Highfrequency cyclic loading of the lumbar spine may trigger a severe acute neuromuscular disorder, as evidenced by the sustained spasms and delayed hyperexcitability, and should be considered as a risk factor. We suggest that workers avoid high-frequency exposure to cyclic activity in order to prevent the development of cumulative trauma disorder.