Alison H. McGregor

Geometrical dimensions of the lower lumbar vertebrae – analysis of data from digitised CT images

Abstract The precise dimensions of the lumbar vertebrae and discs are critical for the production of appropriate spinal implants. Unfortunately, existing databases of vertebral and intervertebral dimensions are limited either in accuracy, study population or parameters recorded. The objective of this study is to provide a large and accurate database of lumbar spinal characteristics from 126 digitised computed tomographic (CT) images, reviewed using the Picture Archiving Communication System (PACS) coupled with its internal measuring instrumentation. These CT images were obtained from patients with low back pain attending the spinal clinic at the Hammersmith Hospitals NHS Trust. Measurements of various aspects of vertebral dimensions and geometry were recorded, including vertebral and intervertebral disc height. The results from this study indicated that the depth and width of the vertebral endplate increased from the third to the fifth lumbar vertebra. Anterior vertebral height remained the same from the third to the fifth vertebra, but the posterior vertebral height decreased. Mean disc height in the lower lumbar segments was 11.6 ± 1.8 mm for the L3/4 disc, 11.3 ± 2.1 mm for the L4/5, and 10.7 ± 2.1 mm for the L5/S1 level. The average circumference of the lower endplate of the fourth lumbar vertebra was 141 mm and the average surface area was 1492 mm2. An increasing pedicle width from a mean of 9.6 ± 2.2 mm at L3 through to 16.2 ± 2.8 mm at L5 was noted. A comprehensive database of vertebral and intervertebral dimensions was generated from 378 lumbar vertebrae from 126 patients measured with a precise digital technique. These results are invaluable in establishing an anthropometric model of the human lumbar spine, and provide useful data for anatomical research. In addition this is important information for the scientific planning of spinal surgery and for the design of spinal implants.

Motion characteristics of the lumbar spine in the normal population.

Study Design The present study investigated the dynamic motion characteristics of the lumbar spine in the normal population using a potentiometric analysis system. Objectives To assess the ability of a triaxial potentiometric analysis system to measure dynamic motion in the lumbar spine, and to use this system to form a database of dynamic motion characteristics from which normal parameters of motion and the factors affecting this motion could be defined. Summary of Background Data Spinal motion has been studied using a variety of different methods, the majority of which have been limited either in terms of reliability, accuracy, or invasiveness and many have been only of a static nature. There has been no previous study into the normal dynamic motion characteristics of the lumbar spine. Methods The accuracy of the system was determined by a series of tests against a callbrated engineering mill, and the reliability of the system was assessed on 10 subjects with repeated measurements over a 3-day period. Values of range of motion and angular velocity were obtained from 203 normal subjects during flexion and extension, lateral flexion, and rotation. Results The results of the calibration testing revealed excellent accuracy, and it was shown that the system was repeatable. Initial analysis of the results indicated that sex differences did exist with men having 58.4° of flexion and women having 53.4°. Age appeared to have an influence on motion, and a gradual reduction was seen with each decade (P < 0.0001), with the 20–29-year age range having 59.5° mean flexion, the 30–39-year group having 58.1°, the 40–49-year group having 53.7°, the 50–60-year group having 57.5°, and the 60–70-year group having 45.9°. Multiple regression techniques revealed that only a few factors are important with respect to motion and that these varied according to the characteristic being defined. Conclusions Range of motion tended to be affected by age and sex, whereas velocity was only affected by distance moved, with occupation and body mass index having little or no influence on the motion. The factors identified could only account for a small proportion of the variation seen, suggesting that it is difficult to predict the motion characteristics with any degree of sensitivity.

Corticospinal excitability in patients with chronic low back pain.

Objective: This study was designed to investigate corticospinal excitability of lumbar muscles using transcranial magnetic stimulation (TMS) in patients with chronic low back pain and correlate this with self-rated measures of disability and pain. Methods: Twenty-four patients with chronic low back pain and 11 healthy control subjects were used in this study. TMS was delivered through an angled double-cone coil, with its cross-over on the vertex and a posterior-to-anterior current flow in the brain. Electromyographic (EMG) recordings were made from erector spinae (ES) muscles at the fourth lumbar level. Motor cortical excitability was assessed using motor threshold (MTh) for motor evoked potentials (MEPs) and threshold for silent period (SP) during facilitation of the back muscles. Latency, duration, and area of MEPs and SPs were also measured. Results: The latency, duration, and size of MEPs and SPs did not differ between the left and right ES muscles in either the patients or the control subjects and also did not differ between the patients and the control subjects. However, there was a significantly higher MTh and threshold for the SP in the patients as compared with the control subjects; the full significance of this requires further investigation. Interestingly, there was a positive correlation between the self-rated measure of disability (the Oswestry Disability Index score) and both the MTh and the threshold for the SP in the patients. There was also a positive correlation between the self-rated index of back pain and the threshold for the SP in the patients. This finding of an association between clinical and neurophysiologic measures reinforces the need for further research to establish the clinical relevance of these rises in MTh and SP threshold. Conclusions: In summary, this study has revealed that corticospinal excitability, driving ES muscles close to the site of pain, is lowered in patients with chronic low back pain.

BACK PAIN AND DISABILITY AFTER LUMBAR LAMINECTOMY: IS THERE A RELATIONSHIP TO MUSCLE RETRACTION?

OBJECTIVE:Preliminary studies have suggested that prolonged retraction of the paraspinal muscle during spinal surgery may produce ischemic damage. We report the continuous measurement of intramuscular pressure (IMP) during decompressive lumbar laminectomy and its relationship to subsequent back pain and disability. METHODS:Twenty patients undergoing two-level decompressive lumbar laminectomy for lumbar canal stenosis were recruited. Back pain and disability were assessed by use of the Visual Analog Score (VAS), Oswestry Disability Index (ODI), and Short-Form 36 (SF-36) Health Survey. During surgery, IMP was recorded continuously from the multifidus muscle by use of a pressure transducer. The intramuscular perfusion pressure (IPP) was estimated as the difference between the patients mean arterial pressure and IMP. RESULTS:Two muscle retractors were used: the Norfolk and Norwich (n = 10) and the McCulloch (n = 10). The mean duration of deep muscle retraction was 62.7 ± 8 minutes (range, 19–133 min). On application of deep muscle retraction, there was a rapid and sustained increase in IMP (P < 0.001), and overall, the calculated mean IPP approached 0 mm Hg or less during this period (P < 0.001). On release of deep muscle retraction, there was a rapid decrease in IMP to preoperative levels. The IPP was greater with the Norfolk and Norwich than the McCulloch retractor (P < 0.001). Compared with preoperative values, there was a decrease in ODI (P < 0.001) and VAS for back pain (P < 0.001) at discharge and 4 to 6 weeks and 6 months after surgery. In addition, there was a decrease in SF-36 scores at 6 months compared with preoperative values (P < 0.001). Total duration of muscle retraction greater than 60 minutes was associated with worse VAS scores for back pain and ODI and SF-36 scores for disability at 6 months after surgery (P < 0.05). There was no relationship between the VAS, ODI, and SF-36 scores and other parameters measured, including the mean IPP, retractor type, operating surgeon, and wound length. CONCLUSION:The McCulloch retractor generates a higher IMP than the Norfolk and Norwich retractor. However, postoperative improvement in VAS, ODI, and SF-36 scores in these patients was associated with a shorter duration of muscle retraction and not the degree of IMP or IPP generated. In this respect, periodic relaxation of the paraspinal muscle retractors during surgery to allow muscle perfusion may help to reduce postoperative back pain and disability.

The pathogenesis of degeneration of the intervertebral disc and emerging therapies in the management of back pain

This article reviews the current knowledge of the intervertebral disc (IVD) and its association with low back pain (LBP). The normal IVD is a largely avascular and aneural structure with a high water content, its nutrients mainly diffusing through the end plates. IVD degeneration occurs when its cells die or become dysfunctional, notably in an acidic environment. In the process of degeneration, the IVD becomes dehydrated and vascularised, and there is an ingrowth of nerves. Although not universally the case, the altered physiology of the IVD is believed to precede or be associated with many clinical symptoms or conditions including low back and/or lower limb pain, paraesthesia, spinal stenosis and disc herniation. New treatment options have been developed in recent years. These include biological therapies and novel surgical techniques (such as total disc replacement), although many of these are still in their experimental phase. Central to developing further methods of treatment is the need for effective ways in which to assess patients and measure their outcomes. However, significant difficulties remain and it is therefore an appropriate time to be further investigating the scientific basis of and treatment of LBP.

The evaluation of the surgical management of nerve root compression in patients with low back pain: Part 1: the assessment of outcome.

Study Design. This was a prospective study investigating the outcome of decompression surgery using validated measures of outcome. Objectives. To investigate the outcome of lumbar decompressive surgery in the initial postoperative year period in terms of function, disability, general health, and psychological well-being. Summary of Background Data. The majority of studies investigating the outcome of lumbar decompression surgery have been retrospective and have not used validated measures of outcome. This limits their interpretation and usefulness. Methods. Eighty-four patients undergoing lumbar spinal stenosis surgery were recruited into this study. Patients were assessed by use of validated measures of outcome including the Oswestry Disability Index and the Short Form SF-36 General Health Questionnaire before surgery and 6 weeks, 6 months, and 1 year after surgery. Results. A significant reduction in pain (P < 0.001) was observed at the 6-week postoperative stage; this did not change at the subsequent assessment stages. Only some of the SF-36 categories were sensitive to change. The subcategories that were sensitive to change were physical function (P < 0.05), bodily pain (P < 0.001), and social function (P < 0.05). Improvements were observed in these categories at the 6-week and 6-month reviews. A gradual reduction in the Oswestry Disability Index was observed with time, with changes principally being observed between the 6-week and 6-month review and the 6-week and 1-year review stages (P < 0.05). Minimal changes were observed in the psychological assessments with time. The outcome of surgery could not be predicted reliably from psychological, functional, or pain measures. Conclusions. The visual analogue pain scales, the Oswestry Disability Index, and certain categories of the SF-36 Questionnaire, namely bodily pain and physical and social function, appeared to be the most sensitive outcome measures, with significant improvements occurring at the 6-week and 6-month reviews.

The use of interventional open MRI to assess the kinematics of the lumbar spine in patients with spondylolisthesis.

Study Design. Open interventional MRI techniques were used to investigate the intervertebral mobility of the lumbar spine in subjects with isthmic and degenerative spondylolisthesis. The findings were compared with those in a published database of subjects with no history of low back pain. Objective. To investigate patterns of intervertebral mobility in subjects with spondylolisthesis to determine the level of spinal instability in this population. Summary of Background Data. Subjects with spondylolisthesis have been considered to present with a special form of spinal instability. Consequently, this condition is frequently managed by spinal fusion. However, confusion exists regarding whether there is excessive motion at the level of the defect. Methods. For this study, 29 subjects presenting to spinal clinics with spondylolisthesis (15 isthmic and 14 degenerative) were recruited and compared with an existing database of control subjects. The motion characteristics of these subjects in flexed and extended positions were investigated using interventional open MRI of known precision. In all the subjects, the level of resting pain, the grade of slip, and the level of the defect were noted. Results. No mobility differences, in terms of both angular and translational motion, were found between the subjects with spondylolisthesis and those with no history of low back pain, suggesting that subjects with spondylolisthesis do not present with either instability or hypermobility. Conclusion. A spondylolytic defect does not lead to detectable instability or hypermobility in the lumbar spine.

Do oarsmen have asymmetries in the strength of their back and leg muscles

The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring :quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring:quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side ( P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.

Balance and gait adaptations in patients with early knee osteoarthritis

Highlights • High knee adduction moments do not occur in early osteoarthritis.• People with early knee-joint osteoarthritis show impairments in balance.• Altered muscle activation is associated with early osteoarthritis during balance tasks.

The assessment of intersegmental motion and pelvic tilt in elite oarsmen.

UNLABELLED Low back pain (LBP) is a common problem in elite oarsmen. The relevance of spinal and pelvic flexibility to good rowing technique and the incidence of LBP is unclear. PURPOSE The aim of this study was to investigate patterns of spinal and pelvic mobility in a group of elite oarsmen with and without a history of LBP. METHODS Twenty elite oarsmen were recruited into this study, including nine with no history of spinal problems, four with a current spinal problem, and the remainder with a history of LBP. Subjects were scanned using an interventional magnetic resonance imaging (MRI) scanner. Four key stages of the rowing stroke were simulated within the scanner, and sagittal images of the lumbar spine and sacrum were obtained. From these images intersegmental motion was determined along with the angle of lordosis and position of the lumbar spine and sacrum. RESULTS Different mobility trends were seen; oarsmen with no history of LBP demonstrated the greatest mobility in their lower lumbar regions (at the L5/S1 level in the catch position 7.5 degrees +/-1.3 in normals; 4.8 degrees +/-1.2 in previous LBP groups; and 2.8 degrees +/-5.5 in current LBP group) and the lowest rotation of their pelvis (level in the catch position 13.9 degrees +/-11.2 in normals; 16.1 degrees +/-6.8 in previous back pain groups; and 15.2 degrees +/-11.2 in current back pain group). In contrast, those with either current or previous LBP presented with a hypomobility of their spine which appeared to be compensated for by increased pelvic rotation. CONCLUSIONS Marked differences were observed in the motion characteristics of these 3 groups of oarsmen. At present it is not known if these changes are causative or effect.