James N. Weinstein

Outcome measures for studying patients with low back pain

There is growing recognition in the treatment of back pain that patient perapectives are essential in judging the results of treatment. Improving the patients “quality of life” is often the main goal of therapy. Thus, although clinical research in the past has focused on physiologic outcomes, such as range of motion, muscle strength, or neurologic deficits, increasing attention is being given to the rigorous measurement of symptoms, functional status, role function, satisfaction with treatment, and health care costs. In many cases, these so called “soft” outcomes can be measured with a level of reproducibility similar to more conventional clinical data such as imaging test results. Because symptoms and functional outcomes are sometimes only loosely associated with physiologic phenomena, the former outcomes should be measured directly. Modern questionnaires for measuring patient quality of life combine the expertise of social scientists and clinicians and have demonstrated validity. Furthermore, they have some important advantages over simple ratings of “excellent, good fair, and poor” outcomes, or work status alone, Several modern instruments for measuring health-related-quality of life in patients with low back pain are reviewed briefly, describing their content and length. Wlder use of these instruments would help to increase clinician familiarity with their meaning and avoid duplication of effort in questionnaire development.

Chordoma of the spine above the sacrum. Treatment and outcome in 21 cases.

Study Design Twenty‐one cases of chordoma arising in the mobile spine were retrospectively reviewed. Objectives All the cases were submitted to oncologic and surgical staging to correlate treatment and outcome. Summary of Background Data Excluding plasmacytomas, chordoma is the most frequent primary malignant tumor of the spine, occurring mainly in elderly men. The course of the disease is slow, metastases occur late, and death can result from complications related to local extension of the disease. Complete excision of the tumor according to oncologic criteria can be hampered by extension of the tumor and by anatomic constraints in the mobile spine. Methods All charts, radiographs, and images were reviewed. The composite information provided by this review allowed for oncologic and surgical of these cases. Treatment was defined according to Ennekings criteria. All the patients were followed for determination of their status clinically and radiographically. Results Ten patients died (1 to 137 months after treatment, mean 65 months); four patients are alive with the disease; only seven patients (33%) are symptom free at the final follow‐up (39 to 112 months after treatment, mean 65 months). Conventional radiation therapy was not effective in eradicating the tumor, even if associated with palliative or debulking surgery: of 15 cases, 12 were associated with recurrence or progression. Intralesional surgery also was not effective (two recurrences in two cases, 18 to 41 months later). En bloc excision of the lesion, sometimes combined with radiation therapy as an adjuvant, obtained the best results (four patients disease free at 39 to 112 months, mean 77 months). Conclusions En bloc excision‐even if marginal‐is the treatment of choice of chordomas of the spine. Early diagnosis and careful surgical staging and planning are necessary. Megavoltage radiation can be administered as an adjuvant.

European Spine Society--the AcroMed Prize for Spinal Research 1995. Unexpected load and asymmetric posture as etiologic factors in low back pain.

Unexpected loads, which often occur in the working environment, can lead to high forces in the spine and, thus, may be a cause of low back injury. This paper discusses the effect of “sudden load” on the erector spine reaction and amplitude. Muscle responses were mediated by several factors, including fatigue, posture, expectation and rehabilitation, in chronic low back pain patients. The subjects were fatigued by holding a 20% maximum voluntary contraction for 1 min. A functional restoration program was tested for its efficacy in reducing reaction time and EMG amplitude in chronic low back pain patients. Reaction time was longer and EMG amplitude lower in patients than in their matched controls. EMG reaction time and magnitude decreased in patients after a 2-week rehabilitation program, including specific training of coordination and posture control. The results of the modelling showed higher spinal compressive load and lower shear forces when the load was expected than when the load was unexpected. The effect of sudden loads can be exacerbated if a worker is not standing on a flat surface or is fatigued. Chronic low back pain patients have less ability to protect themselves from sudden loads, but they can be trained to improve their response by means of an appropriate rehabilitation program.

Intraspinal synovial cysts. Magnetic resonance evaluation.

Five intraspinal synovial cysts in four patients were evaluated with noncontrast magnetic resonance imaging and magnetic resonance imaging with the contrast agent gadolinium diethylenetriaminepentaacetic acid. Useful findings included demonstration of both solid and cystic components, early enhancement of the solid component and cyst periphery, delayed enhancement of the cyst, persistent enhancement of the solid component and cyst capsule, enhancement of the apophyseal joint, and recognition of a possible connection between the cyst and apophyseal joint. Although computed tomographic findings of synovial cysts are quite characteristic for the diagnosis in most cases, contrast magnetic resonance imaging may provide additional information for a more definitive diagnosis.

A BRIEF INTRODUCTION TO THE CRITICAL READING OF THE CLINICAL LITERATURE

Clinicians are bombarded by reports of new diagnostic tests or treatments for patients with spine problems. To provide the best possible patient care, clinicians need to be able to critically appraise the results of such studies for validity and relevance to patient care. Important questions to be asked of any description of diagnostic or treatment studies are the following questions: 1) Are the patients described in detail so that you can decide whether they are comparable to those that you see in your practice? 2) Are the treatments or assessments described well enough so that you could provide the same for your patients? 3) Was a clinically relevant endpoint measured? 4) Is there an appropriate comaparison group? 5) Are potential sources of bias appropriately attended to? 6) Are the results clinically significant?

Loads in the spinal structures during lifting: development of a three-dimensional comprehensive biomechanical model

SummaryEpidemiological studies have shown that loads imposed on the human spine during daily living play a significant role in the onset of low back pain. The loads applied to the lumbar spine are shared by a number of structures: muscles; posterior elements, including facets and ligaments; and the disc of a ligamentous motion segment. In vivo, it is not practical to determine forces in these structures using experimental techniques. Biomechanical models, based on an optimization technique or electromyographic activities of the trunk muscles, have been proposed to predict forces in the load transmitting structures. The mathematical models reported in the literature are based on information collected from a wide variety of sources, of which the subject that takes part in the experiment is only one. The present study describes techniques developed in our laboratory to collect from the subjects themselves all the data needed for the formulation of a biomechanical model. The results demonstrated that back lifting with 0 N (no load), 90 N, and 180 N in the hands created maximum external flexion moments respectively of 109.6 Nm, 137.9 Nm, and 161,7 Nm, at the L3–4 disc level. The corresponding external axial compression forces on the disc were 469.5 N, 511.8 N, and 601.5 N. The predicted disc compression varied from 3.4 to 5.0 times the body weight. In comparison to the static lifting mode, the dynamic lifting task caused an increase in the disc compression force ranging from 15.8% to 39.4% depending on the load being lifted (e.g., 3256 N for the dynamic mode vs. 2516 N for the static mode when the subject lifted 90 N). The salient features of the entire protocol developed by the authors and the need for further improvements are also presented.

Stress analysis of a canine spinal motion segment using the finite element technique

Canine models have been frequently employed to investigate the in vivo effects of a surgical procedure. Various studies indicate that canine models can provide a successful in vivo biological model for these studies. Use of canine models for the biomechanical studies of the spine, however, have been questioned because of different loading conditions on the canine and human spines originated from posture differences between canine and human. Similarities between the stress distributions within the canine and human motion segments under physiological loads will strengthen the use of canine models for the studies of spine biomechanics. In the present study, finite element models of the canine intact and stabilized motion segments were developed to investigate these aspects. Comparison of model predicted flexion angle, axial stiffness, and facet contact force for the canine intact L6-L7 motion segment revealed good agreement with the corresponding parameters experimentally measured under the similar loading conditions. Similar stress distributions within the intact canine and human models were found from the predicted results in response to the physiological load. Stabilizing and stress-shielding effects of a pedicle screw-plate-type fixation device [variable spinal plating (VSP)] on the stabilized motion segment were also similar for the canine and human stabilized models. Furthermore, maximum stresses in the pedicle screws were found at the junction between the bone screw and the integrated nut of the inferior screw in both the canine and human stabilized models. This corresponds to the location of pedicle screw breakage reported in the literature. These findings suggest that a canine is a suitable model for the biomechanical studies of the lumbar spine.

In vitro testing of a new transpedicular stabilization technique.

The rigidity of a pedicle screw implant is a critical biomechanical variable in lumbar spinal fusions. Sufficient rigidity is required for integration of bone grafts and to promote healing. Osteopenia, stress shielding, and compensatory hypermobility have been described as consequences of excessive rigidity. Little is known about the biomechanical characteristics of “semirigid” compared to “rigid” implants. A new implant, whose rigidity can be varied by selection of different implant components, was tested in vitro under well-defined loading conditions. The three-dimensional load-displacement behavior of all lumbar vertebrae involved in or adjacent to the two-level fusion was evaluated for two fusion modifications: bilateral rigid and bilateral semirigid. Cyclic fatigue loading was subsequently carried out under realistic conditions and motion testing repeated. The rigid device reduced the motion of the L3–4 transfixed segment in the primary movement planes by 87.3% with respect to the intact spine value in flexion/extension (FE), 86.3% in lateral bending (LB), and 76.8% in axial rotation (AR). The semirigid device achieved a reduction in motion of 79.6% (FE), 82.7% (LB), and 51.7% (AR). The semirigid implant was particularly easy to insert, because no bending of rods or plates was necessary. The implants showed no loosening or breakage after the fatigue testing. The results are compared to other available systems and the underlying biomechanics discussed.

The virtual hospital. Providing multimedia decision support tools via the Internet.

Physicians in the clinical setting remain isolated from important sources of medical information. The authors have created a multimedia database known as The Virtual Hospital that improves access to current medical data, which is used to improve patient care decisions. The Virtual Hospital is a digital health sciences library stored on a server (computer) at The University of Iowa and delivered via the Internet to inexpensive personal computers in the workplace. The emerging standard of the World Wide Web is used to provide cross-platform distribution.

Strategies for outcome research in spinal disorders. An introduction.

The evaluation of the clinical utility of the clinical diagnostic tests and procedures, what works in spinal disorders, and for whom and how treatment affects a patients symptoms and function are key questions of outcomes research. This paper describes the advantages and limitations of the main study approaches used. Examples from the spine literature on spinal stenosis are used for illustration.