Diagnostic external fixation of the lumbar spine

Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 14: brace therapy as an adjunct to or substitute for lumbar fusion

Although conflicting reports have been presented in the literature regarding the utility of lumbar braces for the prevention of low-back pain, most Class III medical evidence suggests that these supports used prophylactically do not reduce the incidence of low-back pain or decrease the amount of time lost from work in the general working population. Among workers with a history of a back injury, their use appears to decrease the number of work days lost due to back pain. Lumbar braces appear to be an effective treatment for acute low-back pain in some populations. They do not appear to be effective in the chronic low-back pain population. If a brace is used, rigid braces offer some benefit over soft braces. There are no data to suggest that relief of low-back pain with preoperative external bracing predicts a favorable outcome following lumbar spinal fusion. No information is available on the benefit of bracing for improving fusion rates or clinical outcomes following instrumented lumbar fusion for degenerative disease.

Three-dimensional stabilization provided by the external spinal fixator compared to two internal fixation devices: a biomechanical in vitro flexibility study

We performed an in vitro study to investigate the stabilization (i.e. motion reduction) provided by the external spinal fixator (ESF), and to compare the three configurations of the ESF with two internal fixation techniques. Six human cadaveric lumbar spine specimens (L3-S1) were subjected to multidirectional flexibility testing in six configurations: (1) intact, (2) ESF in neutral, (3) ESF in distraction, (4) ESF in compression, (5) translaminar facet screw fixation, and (6) internal transpedicular fixation. Both the ESF and the internal fixation systems stabilized the specimens from L4 to S1. In each testing configuration, pure bending moments of flexion-extension, bilateral axial rotation, and bilateral lateral bending were applied to the uppermost vertebra stepwise to a maximum of 10 Nm. The rigid body motion between the vertebrae was measured using an optoelectronic camera system, and custom software was used to calculate the intervertebral rotations. For each applied motion in all testing configurations, the total range of motion (ROM) of L4-S1 is reported. All three ESF configurations stabilized the spine significantly when compared to the intact specimen. The ESF in compression provided significantly more stabilization in flexion-extension than the two other ESF configurations, but no other significant differences were found between the three ESF modes. In flexion-extension the ESF stabilized the spine significantly when compared with the two internal fixation devices. Only in bilateral lateral bending was the ESF inferior to internal transpedicular fixation in providing stabilization. The results of the present study suggest that the ESF provides a high degree of stabilization for preoperative assessment of selected low back pain patients. Whether other non-mechanical factors affect the pain relief experienced by the patients remains unknown.

The external spinal fixator does not reduce anterior column motion under axial compressive loads. A mechanical in vitro study

We performed an in vitro study to investigate the effect of external spinal fixation on anterior column motion under physiological axial compression loading. The AO external spinal fixator (ESF) was applied to 5 human cadaveric lumbar spine specimens (L3-S1) at levels L4 to S1. All specimens were tested in 4 configurations: i) intact, ii) ESF in a neutral position, iii) ESF in distraction (12 mm), and iv) ESF in compression (8-12 mm). Cyclic sinusoidal axial compressive loads from 60 to 600 N were applied for 10 cycles in each test condition. The axial displacement of the load application point was recorded as an indicator of anterior column axial translation. The axial motion with the fixator in distraction was significantly greater than all other conditions, including intact. Compression of the fixator resulted in the least axial displacement. External fixation in the neutral position did not significantly affect the overall axial translation, when compared to the intact state. In conclusion, the external spinal fixator did not significantly reduce anterior column axial translation and, in distraction, this motion exceeded that of the intact specimen. Since pain relief is frequently observed during distraction of the painful segment/s with the external fixator, the mechanical basis of the pain relief is not well understood.

Mechanics of the external fixation test in the lumbar spine. A roentgen stereophotogrammetric analysis

STUDY DESIGN

By implanting tantalum indicators percutaneously during application of pedicular screws, lumbosacral mobility could be studied with roentgen stereophotogrammetric analysis in seven patients having a diagnostic external fixation test.

OBJECTIVES

To determine the mechanical effects on the segmental mobility during an external fixation test of the lumbar spine.

SUMMARY OF BACKGROUND DATA

External pedicular fixation test of the lumbar spine has been reported a valuable prognostic instrument in fusion for low back pain.

METHODS

A Magerl external fixation device was applied in seven patients with low-grade spondylolysis-olisthesis. By using roentgen stereophotogrammetric technique, the intervertebral translations in the lumbosacral segment were determined. Each patient had three separate examinations; with the frame fixed, with the frame loosened, and without frame 6 weeks after screw removal.

RESULTS

With the external frame fixed, the sagittal intervertebral translations were significantly reduced, in three cases to a level beneath the accuracy of the measuring method. One patient had the same immobilizing effect even with the frame loosened while for the others loosening of the frame meant regained mobility of the segment.

CONCLUSION

The properties of the external fixator give an adequate mechanical basis for the prognostic external fixation test in lumbar fusion.

Posterolateral lumbar fusion. Outcome of 71 consecutive operations after 4 (2-7) years

We report the outcome of 71 consecutive posterolateral lumbar fusions without spinal instrumentation. The indication for the operation was spondylolysis-olisthesis, degenerative disc disease/facet joint arthrosis, or pain after prior laminectomy. Concerning pain relief, 29/43 patients with spondylolysis-olisthesis were classified as good. The corresponding figures in the group with degenerative disc disease and/or facet joint arthrosis were 8/16 patients and in the group with pain post-laminectomy, 6/12 patients. No surgical complications were noted. In the total material 54 patients had a solid fusion, as defined by radiographic osseous trabecular bridging at all intended levels. One-level fusions tended to heal solidly in a higher frequency than two-level fusions. For the spondylolysis-olisthesis group, healed fusion correlated with a good clinical result. Such a correlation could not be verified for the other diagnostic groups. We conclude that non-instrumented posterolateral lumbar fusion is a valid method for treating low-grade spondylolysis-olisthesis, especially when the aim is to fuse a single level. Improved patient selection methods are required in fusion for degenerative disc disease and pain after laminectomy.