Eric C. Parent

Lumbar disc degeneration: epidemiology and genetic influences.

Study Design. A literature review. Objective. To synthesize the scientific literature on the prevalence of lumbar disc degeneration and factors associated with its occurrence, including genetic influences. Methods. A literature review was conducted of the prevalence of disc degeneration. Studies of the etiology of disc degeneration were summarized, with particular attention given to studies of genetic influences. Results and Conclusions. There are extreme variations in the reported prevalence of specific degenerative findings of the lumbar spine among studies, which cannot be explained entirely by age or other identifiable risk factors (e.g., prevalence figures for disc narrowing varied from 3% to 56%). It is likely that these variations are due, in great part, to inconsistencies in case definitions and measurements, which are impeding epidemiologic research on disc degeneration. Research conducted over the past decade has led to a dramatic shift in the understanding of disc degeneration and its etiology. Previously, heavy physical loading was the main suspected risk factor for disc degeneration. However, results of exposure-discordant monozygotic and classic twin studies suggest that physical loading specific to occupation and sport has a relatively minor role in disc degeneration, beyond that of upright postures and routine activities of daily living. Recent research indicates that heredity has a dominant role in disc degeneration, explaining 74% of the variance in adult populations studied to date. Since 1998, genetic influences have been confirmed by the identification of several gene forms associated with disc degeneration.

Reliability of Rehabilitative Ultrasound Imaging of the Transversus Abdominis and Lumbar Multifidus Muscles

OBJECTIVES To evaluate the intraexaminer and interexaminer reliability of rehabilitative ultrasound imaging (RUSI) in obtaining thickness measurements of the transversus abdominis (TrA) and lumbar multifidus muscles at rest and during contractions. DESIGN Single-group repeated-measures reliability study. SETTING University and orthopedic physical therapy clinic. PARTICIPANTS A volunteer sample of adults (N=30) with current nonspecific low back pain (LBP) was examined by 2 clinicians with minimal RUSI experience. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Thickness measurements of the TrA and lumbar multifidus muscles at rest and during contractions were obtained by using RUSI during 2 sessions 1 to 3 days apart. Percent thickness change was calculated as thickness(contracted)-thickness(rest)/thickness(rest). Intraclass correlation coefficients (ICC) were used to estimate reliability. RESULTS By using the mean of 2 measures, intraexaminer reliability point estimates (ICC(3,2)) ranged from 0.96 to 0.99 for same-day comparisons and from 0.87 to 0.98 for between-day comparisons. Interexaminer reliability estimates (ICC(2,2)) ranged from 0.88 to 0.94 for within-day comparisons and from 0.80 to 0.92 for between-day comparisons. Reliability estimates comparing measurements by the 2 examiners of the same image (ICC(2,2)) ranged from 0.96 to 0.98. Reliability estimates were lower for percent thickness change measures than the corresponding single thickness measures for all conditions. CONCLUSIONS RUSI thickness measurements of the TrA and lumbar multifidus muscles in patients with LBP, when based on the mean of 2 measures, are highly reliable when taken by a single examiner and adequately reliable when taken by different examiners.

A systematic review of the reliability of rehabilitative ultrasound imaging for the quantitative assessment of the abdominal and lumbar trunk muscles

Study Design. Systematic review. Objective. To systematically review the literature on the rater reliability of Rehabilitative Ultrasound Imaging (RUSI) measurements to assess the morphology of the abdominal and lumbar trunk musculature. Summary of Background Data. RUSI is an increasingly popular method of evaluating the morphology and function of muscles with real-time ultrasound. Conclusions regarding the reliability of measurements obtained by RUSI, need to be established before recommending its wider use. Methods. A systematic approach to searching and identifying original research articles reporting quantitative RUSI measurements was undertaken. Reliability data were extracted and methodologic quality was evaluated by 2 independent reviewers. Results. Of the 24 studies included, 6 were deemed to be of high methodologic quality. Among high quality studies, some reported the measurement error associated with performing repeated measurements of the same image (intraimage analysis), whereas others reported the reliability of obtaining and measuring unique RUSI images (interimage analysis). Intraimage measurements demonstrated good intrarater and interrater reliability (ICC: >0.93). Interimage measurements demonstrated good reliability between raters (ICC: >0.90). Interimage, intrarater correlation coefficients were more variable with ICC values ranging from 0.62 to 0.97. Conclusion. The methodologic quality of research investigating the reliability of RUSI to measure the abdominal and lumbar trunk muscles needs to be improved. The majority of results of high quality studies indicate that RUSI has good levels of rater reliability. Improved reliability was observed among studies examining muscle thickness, and when using mean measurement values obtained by more experienced examiners.

Rehabilitative ultrasound imaging is a valid measure of trunk muscle size and activation during most isometric sub-maximal contractions: a systematic review.

QUESTIONS Is rehabilitative ultrasound imaging a valid measure of trunk muscle size and activation? Are rehabilitative ultrasound imaging measures sensitive to change? DESIGN Systematic review of studies of criterion-related validity, construct validity, and sensitivity to change. PARTICIPANTS People with low back pain and asymptomatic controls. OUTCOME MEASURE Trunk muscle size and activation measured by rehabilitative ultrasound imaging, MRI and/or EMG. RESULTS 37 studies were included. 10 studies investigated criterion-related validity and provided evidence that while ultrasound may be a valid measure of trunk muscle size, the validity of ultrasound to quantify muscle activation is context-dependent, depending on the muscle involved, the contraction strategy utilised, and the intensity of muscle contraction. 23 studies provided evidence of construct validity by demonstrating the ability of ultrasound measurement to differentiate individuals in terms of back pain, anthropometry, and postures. Six studies contained a limited amount of information about sensitivity to change. CONCLUSIONS. It is valid to use rehabilitative ultrasound imaging to measure trunk muscle size and activation during most isometric sub-maximal contractions. Ultrasound measures appear sensitive to both positive and negative change.

Evaluation of a Treatment-Based Classification Algorithm for Low Back Pain: A Cross-Sectional Study

Background Several studies have investigated criteria for classifying patients with low back pain (LBP) into treatment-based subgroups. A comprehensive algorithm was created to translate these criteria into a clinical decision-making guide. Objective This study investigated the translation of the individual subgroup criteria into a comprehensive algorithm by studying the prevalence of patients meeting the criteria for each treatment subgroup and the reliability of the classification. Design This was a cross-sectional, observational study. Methods Two hundred fifty patients with acute or subacute LBP were recruited from the United States and Australia to participate in the study. Trained physical therapists performed standardized assessments on all participants. The researchers used these findings to classify participants into subgroups. Thirty-one participants were reassessed to determine interrater reliability of the algorithm decision. Results Based on individual subgroup criteria, 25.2% (95% confidence interval [CI]=19.8%–30.6%) of the participants did not meet the criteria for any subgroup, 49.6% (95% CI=43.4%–55.8%) of the participants met the criteria for only one subgroup, and 25.2% (95% CI=19.8%–30.6%) of the participants met the criteria for more than one subgroup. The most common combination of subgroups was manipulation + specific exercise (68.4% of the participants who met the criteria for 2 subgroups). Reliability of the algorithm decision was moderate (kappa=0.52, 95% CI=0.27–0.77, percentage of agreement=67%). Limitations Due to a relatively small patient sample, reliability estimates are somewhat imprecise. Conclusions These findings provide important clinical data to guide future research and revisions to the algorithm. The finding that 25% of the participants met the criteria for more than one subgroup has important implications for the sequencing of treatments in the algorithm. Likewise, the finding that 25% of the participants did not meet the criteria for any subgroup provides important information regarding potential revisions to the algorithms bottom table (which guides unclear classifications). Reliability of the algorithm is sufficient for clinical use.

The Effect of Averaging Multiple Trials on Measurement Error During Ultrasound Imaging of Transversus Abdominis and Lumbar Multifidus Muscles in Individuals With Low Back Pain

STUDY DESIGN Clinical measurement, reliability study. OBJECTIVES To investigate the improvements in precision when averaging multiple measurements of percent change in muscle thickness of the transversus abdominis (TrA) and lumbar multifidus (LM) muscles. BACKGROUND Although the reliability of TrA and LM muscle thickness measurements using rehabilitative ultrasound imaging (RUSI) is good, measurement error is often large relative to mean muscle thickness. Additionally, percent thickness change measures incorporate measurement error from both resting and contracted conditions. METHODS Thirty volunteers with nonspecific low back pain participated. Thickness measurements of the TrA and LM muscles were obtained using RUSI at rest and during standardized tasks. Percent thickness change was calculated with the formula thickness(contracted) - thickness(rest)/thickness(rest). Standard error of measurement (SEM) quantified precision when using 1 or a mean of 2 to 6 consecutive measurements. RESULTS Compared to when using a single measurement, SEM of both the TrA and LM decreased by nearly 25% when using a mean of 2 measures, and by 50% when using the mean of 3 measures. Little precision was gained by averaging more than 3 measurements. CONCLUSION When using RUSI to determine percent change in TrA and LM muscle thickness, intra examiner measurement precision appears to be optimized by using an average of 3 consecutive measurements.

Beyond minimally important change: Defining a successful outcome of physical therapy for patients with low back pain

Study Design. Prospective, longitudinal cohort study Objective. To examine the validity of a threshold that has been used to define a successful outcome for patients with low back pain (LBP), undergoing nonsurgical rehabilitation based on a 50% improvement on the Modified Oswestry disability index (ODI). Summary of Background Data. Making research findings interpretable is a goal of evidence-based practice. One attempt to improve interpretability is reporting treatment results as the percentage of patients achieving a threshold level of improvement within treatment groups along with mean between-group differences. The most recommended threshold is the minimum clinically important difference of the outcome tool. For clinical conditions with favorable natural histories such as LBP, thresholds requiring more than minimal improvement may be preferable for defining success. Methods. Patients with LBP receiving 4 weeks of physical therapy were examined. The ODI and measures of pain, fear-avoidance beliefs, and demographic characteristics were recorded at baseline and after treatment. A 15-point global rating of change was also completed after treatment. The percent ODI change with treatment was computed and compared between groups known to have different prognoses. The percent ODI change was compared to the global rating of change to determine the accuracy of various thresholds of success based on the percent ODI change. Results. A total of 243 subjects (mean age 37.2 ± 11.4 years, 44.9% female) were included. Mean percent ODI change was 43.1% (±40.5), and 109 subjects (44.9%) had a successful outcome (≥50% ODI improvement). As hypothesized, baseline factors with known prognostic importance were less likely to be present in subjects with a successful outcome. The 50% ODI improvement threshold for success had high sensitivity (0.84; 95% CI: 0.79, 0.88) and specificity (0.89; 95% CI: 0.85, 0.93) when compared with success based on the global rating of change. No other percent improvement threshold for the ODI had a higher accuracy than the 50% threshold when compared to the global rating of change. Conclusion. A threshold of 50% improvement on the ODI may be a valid measure for defining a successful outcome for patients with LBP.

Progression and Determinants of Quantitative Magnetic Resonance Imaging Measures of Lumbar Disc Degeneration : A Five-Year Follow-up of Adult Male Monozygotic Twins

Study Design. A longitudinal study. Objective. Our goal was to explore the role of digital magnetic resonance imaging (MRI) data, by extending our earlier 5-year follow-up study of progression of lumbar spine degeneration with quantitative measures of disc degeneration. Summary of Background Data. A longitudinal study is optimal for investigating disc degeneration but only a few studies (with small sample sizes) or short follow-up studies include repeated MRI data. Methods. Subjects consisted of 134 male monozygotic twins (age 35–69 years). Quantitative MRI measures included changes in disc bulging and height. Inter-rater reliability coefficients were between 0.77 and 0.96. At baseline and follow-up, an extensive interview about exposures to suspected determinants was conducted. Results. Reduction in disc height and increases in bulges (worsening) were seen in 2/3 of subjects. The mean reduction in disc height was 2.2% to 3.6%. A mean increase in bulging of 7% to 10% was found in the L1–L4 discs and 4% in L4–S1 discs. Although the mean changes were small, few reverse changes were observed. Familial aggregation, a proxy for genetic influences, explained 17% of changes in disc height, and 11% and 0% of changes in the sizes of anterior and posterior bulges in the regression models. Higher maximal occupational lifting (AR2 = 4.9%) and smoking (AR2 = 3.5%) during follow-up predicted more disc height reduction. Greater increases in bulging (AR2 = 7.4%–10.2%) were predicted by smaller bulges at baseline. Conclusion. The mean annual changes in disc heights (<1%) and bulges (<2%) were small, and included both decreases and increases, with only a few subjects showing more major changes in either direction. The role of genetics was largest except in posterior bulges, but lifting and smoking were also associated with disc height reduction but none of the other studied risk factors were associated with anterior or posterior disc bulging. Different degenerative findings have different determinants of progression.

Validity and Reliability of Active Shape Models for the Estimation of Cobb Angle in Patients with Adolescent Idiopathic Scoliosis

Choosing the most suitable treatment for scoliosis relies heavily on accurate and reproducible Cobb angle measurement from successive radiographs. The objective is to reduce variability of Cobb angle measurement by reducing user intervention and bias. Custom software to increase automation of the Cobb angle measurement from posteroanterior radiographs was developed using active shape models. Validity and reliability of the automated system against a manual and semiautomated measurement method was conducted by two examiners each performing measurements on three occasions from a test set (N = 22). A training set (N = 47) of radiographs representative of curves seen in a scoliosis clinic was used to train the software to recognize vertebrae from T4 to L4. Images with a maximum Cobb angle between 20° and 50°, excluding surgical cases, were selected for training and test sets. Automated Cobb angles were calculated using best-fit slopes of the detected vertebrae endplates. Intraclass correlation coefficient (ICC) and standard error of measurement (SEM) showed high intraexaminer (ICC > 0.90, SEM 2°–3°) and interexaminer (ICC > 0.82, SEM 2°–4°), but poor intermethod reliability (ICC = 0.30, SEM 8°–9°). The automated method underestimated large curves. The reliability improved (ICC = 0.70, SEM 4°–5°) with exclusion of the four largest curves (>40°) in the test set. The automated method was reliable for moderate-sized curves, and did detect vertebrae in larger curves with a modified training set of larger curves.

Do various baseline characteristics of transversus abdominis and lumbar multifidus predict clinical outcomes in nonspecific low back pain? A systematic review.

Summary There is conflicting evidence regarding the ability of baseline morphometry of transversus abdominis and lumbar multifidus to predict clinical outcomes of conservatively treated patients with nonspecific low back pain. Abstract Although individual reports suggest that baseline morphometry or activity of transversus abdominis or lumbar multifidus predict clinical outcome of low back pain (LBP), a related systematic review is unavailable. Therefore, this review summarized evidence regarding the predictive value of these muscular characteristics. Candidate publications were identified from 6 electronic medical databases. After review, 5 cohort studies were included. Although this review intended to encompass studies using different muscle assessment methods, all included studies coincidentally used ultrasound imaging. No research investigated the relation between static morphometry and clinical outcomes. Evidence synthesis showed limited evidence supporting poor baseline transversus abdominis contraction thickness ratio as a treatment effect modifier favoring motor control exercise. Limited evidence supported that high baseline transversus abdominis lateral slide was associated with higher pain intensity after various exercise interventions at 1‐year follow‐up. However, there was limited evidence for the absence of relation between the contraction thickness ratio of transversus abdominis or anticipatory onset of lateral abdominal muscles at baseline and the short‐ or long‐term LBP intensity after exercise interventions. There was conflicting evidence for a relation between baseline percent thickness change of lumbar multifidus during contraction and the clinical outcomes of patients after various conservative treatments. Given study heterogeneity, the small number of included studies and the inability of conventional greyscale B‐mode ultrasound imaging to measure muscle activity, our findings should be interpreted with caution. Further large‐scale prospective studies that use appropriate technology (ie, electromyography to assess muscle activity) should be conducted to investigate the predictive value of morphometry or activity of these muscles with respect to LBP‐related outcomes measures.