Dieter Grob

Biomechanical evaluation of four different posterior atlantoaxial fixation techniques.

Four different techniques for posterior atlantoaxial fusion were tested in vitro: 1) wire fixation with one median graft (Gallie type); 2) wire fixation with two bilateral grafts (Brooks type); 3) transarticular screw fixation (Magerl); and, 4) two bilateral posterior clamps (Halifax). The experiment was designed to determine the immediate three-dimensional stability of the spinal construct. Ten fresh human cadaveric specimens were tested intact, injured, and instrumented with each of the fixation techniques. The injury consisted of a severe soft tissue injury model, in which the alar, transverse, and capsular ligaments were transected. The three-dimensional motions of C1 relative to C2 were measured as the specimens were subjected to loads of pure moments in flexion-extension, axial rotation, and lateral bending. Each fixation technique significantly decreased motion in all directions, as compared to the intact and injured spines. We found that the Gallie system generally allowed significantly more rotation in flexion, extension, axial rotation, and lateral bending than the other three fixation techniques. There was generally no significant difference between the amount of rotation with the other three fixation techniques. However, the Magerl technique tended to allow the least rotation. The anteroposterior translation of two points on C1 were about equal for all fixation techniques.

Functional radiographic diagnosis of the lumbar spine. Flexion-extension and lateral bending.

Several attempts have been made to measure the segmental range of motion in the lumbar spine during flexion–extension with the purpose of gathering additional data for the diagnosis of instability. The previous studies were performed in vitro or in vivo during active motion. The aim of this study was to obtain normal values of passively performed segmental motions. Forty-one healthy adults were examined by means of functional radiographs during flexion–extension and lateral bending. A graphic construction method and a computerassisted method were used to measure rotations. Comparing with recent in vivo studies, the values obtained for normal angles of rotation were predominately larger. This might be due to the passive examination used in the study. The graphic construction method and computerassisted method techniques are equally reliable, but the computer-assisted method method yields other important kinematic data, such as translations. It is proposed that passive motion be applied during functional examination of patients with suspected instabilities. However, the large variation of rotational values between individuals in the normal population may limit the clinical usefulness of functional lumbar analysis using this parameter. Future studies should explore the clinical relevance of determining altered segmental mobility in low-back pain patients.

Clinical validation of functional flexion-extension roentgenograms of the lumbar spine

The purpose of this study was to determine the clinical validity of functional flexion-extension roentgenograms of the lumbar spine in a defined patient population. One hundred and one adults with low-back pain or functional disorders underwent passive functional flexionextension examinations. Their roentgenograms were analyzed using a computer-assisted method to determine segmental motion parameters such as rotation and translation of the lumbar vertebrae. The patient population was broken down into five groups with similar pathologies or physical conditions, and their motion parameters compared to a normal population and to each other. It was found that all of the patient groups exhibited significantly hypomobile motion, spread equally among all levels, in comparison to the normal population, except for the group of high-performance athletes, who had significant hypermobility. The uniform spread of hypomobility limits the ability to distinguish with any confidence between the four pathologic groups by their motion. Thus, we believe that the analysis of the segmental motion of the lumbar spine using passive flexion-extension roentgenograms does not aid in differentiating the underlying pathologic condition of patients with low-back pain, and that no useful information can be derived form this procedure, especially in relation to the need for surgical intervention.

Clinical validation of functional flexion-extension radiographs of the cervical spine

The aim of this study was to determine the clinical validity of functional flexion/extension radiographs of the cervical spine in a defined patient population. Sixty-four adults with functional disorders of the cervical spine underwent passive flexion/extension radiographic examinations. The radiographs were analyzed using a computer assisted method to calculate segmental motion parameters, such as rotations, translations, and centers of rotation. The patients were separated into three groups based on their specific functional disorders, and their motion parameters were compared with those of a healthy population. The three groups consisted of patients with degenerative changes, those with radicular syndrome, and those with whiplash trauma. Most of the patients displayed trends toward hypomobile segmental motion. This trend is displayed more substantially in the groups with degeneration and radicular syndrome. Hypomobility in segmental rotation was significant at C6-C7 for the degenerative and radicular groups. The trauma group showed trends toward hypermobility in the upper and middle cervical levels, and the locations of the centers of rotation were shifted in the anterior direction when compared with those of the healthy population.

Degenerative lumbar spinal stenosis. Decompression with and without arthrodesis.

We prospectively evaluated the results of decompression of the spine, with and without arthrodesis, for the treatment of lumbar spinal stenosis without instability in forty-five patients (twenty-one men and twenty-four women) who had been managed between November 1989 and November 1990. The average age at the time of the operation was sixty-seven years (range, forty-eight to eighty-seven years). The patients were randomly assigned to one of three treatment groups (fifteen patients in each group) according to when they were admitted to the hospital. Group I was treated with decompression with laminotomy and medial facetectomy; Group II, with decompression and arthrodesis of the most stenotic segment; and Group III, with decompression and arthrodesis of all of the decompressed vertebral segments. All of the operations were performed by the same surgeon. The average duration of follow-up was twenty-eight months (range, twenty-four to thirty-two months). All three groups had a significant improvement in the distance that the patients were able to walk at the time of the latest follow-up examination compared with before the operation (p < 0.001 for Group I, p < 0.002 for Group II, and p < 0.005 for Group III). With the numbers available, there were no significant differences in the results among the three groups with regard to the relief of pain (p = 0.25 for Group I compared with Group II, p = 0.36 for Group II compared with Group III, and p = 0.92 for Group I compared with Group III).(ABSTRACT TRUNCATED AT 250 WORDS)

Posterior surgical approach to the lumbar spine and its effect on the multifidus muscle.

Study Design. This study investigated the changes in the lumbar muscles after posterior fusion of the lumbar spine and the potential correlation between muscular changes and the persistence of low back pain. Objectives. To evaluate prospectively the effect of the posterior approach to the spine on the lumbar erector spinae. Summary of Background Data. The posterior approach to the spine leads to considerable alteration of the erector spinae muscles. An eventual correlation between these changes and persisting pain or other clinical symptoms has not been investigated previously. Methods. Seventy‐five patients undergoing spondylosyndesis for different indications (43 patients) or a second operation for the removal of internal fixation (32 patients) were allotted to the study. In each patient, four biopsy specimens from the lumbar multifidus muscle were harvested; in 14 patients, biopsies were taken at both operations. Size and distribution of the fiber types (I, IIA, IIB, IIC) were determined, and pain scoring (visual analogue scale) and the presence of neurologic deficits were recorded. Results. At the time of the first operation, 88% of the patients showed pathologic changes (altered internal structure, atrophy, type grouping) in one or more biopsies. Statistical analysis showed a correlation between both age and pain and type II (A + B) atrophy. After surgery, the patients showed significantly more biopsies with denervation signs than before surgery. No correlation could be made, however, between the intensity of pain before or after surgery and the relative number of biopsies with signs of denervation. Conclusions. Posterior surgery causes muscular alterations; however, no correlation with pain or other clinical symptoms could be established. Therefore, in the case of unsatisfactory results after surgery of the lumbar spine, reasons other than muscle damage caused by use of the posterior approach must be considered.

Posterior occipitocervical fusion : a preliminary report of a new technique

A new technique for occipitocervical fusion is described. The fixation of the upper cervical spine with plates and screws avoids the possible disadvantages of the commonly used wiring technique. By the establishment of a rigid fixation between the occiput and upper cervical spine with a combination of plates and screws, especially with transarticular atlantoaxial screw fixation, reliable, multidirectional, and immediate stability is achieved. The clinical picture and analysis of 14 patients with a variety of pathologies of the upper cervical spine is presented. The satisfactory outcome and solid bony fusion in all 14 patients and the absence of severe complications encourages the continued use of this technique of occipitocervical fusion.

Longitudinal validation of the Fear-Avoidance Beliefs Questionnaire (FABQ) in a Swiss-German sample of low back pain patients

Work and activity-specific fear-avoidance beliefs have been identified as important predictor variables in relation to the development of, and treatment outcome for, chronic low back pain. The objective of this study was to provide a cross-cultural German adaptation of the Fear-Avoidance Beliefs Questionnaire (FABQ) and to investigate its psychometric properties (reliability, validity) and predictive power in a sample of Swiss-German low back pain patients. Questionnaires from 388 operatively and non-operatively treated patients were administered before and 6 months after treatment to assess: socio-demographic data, disability (Roland and Morris), pain severity, fear-avoidance beliefs, depression (ZUNG) and heightened somatic awareness (MSPQ). Complete baseline and follow-up questionnaires were available from 255 participants. The corrected item-total correlations, coefficients of test-retest reliability and internal consistencies of the two scales of the questionnaire were highly satisfactory. In a confirmatory factor analysis (CFA), all items loaded on the appropriate factor with minor loadings on the other. Cross-sectional regression analysis with disability and work loss as the dependent variables yielded results that were highly comparable with those reported for the original version. Prognostic regression analysis replicated the findings for work loss. The cross-cultural German adaptation of the FABQ was very successful and yielded psychometric properties and predictive power of the scales similar to the original version. The inclusion of fear-avoidance beliefs as predictor variables in studies of low back pain is highly recommended, as they appear to have unique predictive power in analyses of disability and work loss.

Predictors of Bad and Good Outcome of Lumbar Spine Surgery: A Prospective Clinical Study With 2 Years' Follow-up

Study Design Based on prospective assessment, patients with lumbar disc surgery were examined to determine reliable predictors for clinical outcome. Objectives The prognostic value of a screening checklist developed in a previous study was evaluated in a 2‐year follow‐up. Summary of Background Data Outcome studies of lumbar disc surgery document a success rate between 49–90%. It has been shown that a number of medical history data and sociodemographic and psychodiagnostic findings are of prognostic value for the outcome of lumbar spine surgery. Methods In addition to clinical and neuroradiologic examinations, 164 patients took part in a standardized interview. Eighty‐two percent participated in a follow‐up performed 2 years after the operation. Preoperative findings, outcome, and prediction of three diagnostic subgroups were compared. Eighty‐three (51%) patients had disc herniation only, 29 (18%) had disc herniation and other relevant back diagnoses, and 51 (31%) had no disc herniation but had other relevant back diagnoses. Results In patients with disc herniation only, good results were observed in 53%, moderate in 19%, and bad in 28%. The accuracy of prediction of the postoperative result was 75% for the patients with good outcome and 86% for those with bad outcome. In the group of patients with diagnoses other than disc herniation, the success rate of the operation was 38% good, 28% moderate, and 41% bad, but the predictor score was not as useful as for the other groups. Conclusion Patietns with a high risk of a bad operation outcome after lumbar discectomy could be identified preoperatively. It is suggested that those patients take part in a pain management approach instead of or in addition to surgical intervention.

On the understanding of clinical instability

Study Design Three-dimensional flexibility changes due to the application of an external fixator at C4-C5 were studied in cervical spine specimens. Objectives to evaluate the biomechanical effects of applying a cervical external fixator to a patient using an in vitro model. Summary of Background Data There is controversy regarding the relationship between the changes in spinal motion and clinical instability. Methods Using fresh cadaveric C4-C7 specimens, multidirectional flexibility was measured at all vertebral levels, before and after the fixator application at C4-C5, C5-C6, and C4-C6. Results The average ranges of motion for flexion, extension, lateral bending, and axial rotation were 8.3° 7.2°, 5.3°, and 5.6°, which descreased by 40%, 27%, 32%, and 58%, repectively, because of the fixator application. The corresponding neutral zones were 3.4°, 3.4°, 3.0°, and 2.0°, which decreased by 76%, 76%, 54%, and 69%, respectively. The decreases with the fixation at C4-C5 were similar to those for fixation at C5-C6. Conclusions This in vitro study documented that the application of an external fixator to the cervical spine decreases the intervertebral motion in general, and decreases flexion, extension and torsional neutral zones in particular. The findings help explain the clincal instability of the spine and support the hypothesis that the neutral zone is more closely associated with the clinical instability than is the range of motion.