The most considerable cause of nerve root damage are compression force and stretch force. Many researchers had reported about experimental study of the compression force, but it is difficult to find the report describing the stretch force to the nerve roots. The purpose of this study is to evaluate the physiological reaction of nerve roots of rats nuder stretch force.

The nerve roots were prepared from the cauda equina of 8 Wister rats (weight: 300 – 400g). We investigated the changes in threshold and action potential of the nerve roots under stretch force and compression force.

The threshold of the nerve roots increased and action potential decreased in parallel with stretch force. Also, the threshold and action potential recovered after releasing the stretch force. On the other hand, by compression force, the action potential decreased parallel with compression force, but the threshold did not change with compression force. Ten minutes after releasing compression force, the action potential did not recover as much as before, and the threshold increased rather than control.

The different physiological reactions that occurred between compression force and stretch force are hard to explain by circulation insufficiency, as previously reported (hypoxemia and lack of nutrition). We considered that the etiology of the stretch force might be a change in internal pressure of nerve roots and a structural change in nerve cells.

The physiological reaction of the nerve root under stretch force differed from that under compression force and recovered from the damage after release from stretch force.

Purpose: When we treat burst fractures, we try to preserve the movable vertebra as much as possible and see to it that the instrument can be extracted finally.

We have performed short-segment posterior spinal instrumentation and fusion (PSIF) for cases with no neurological symptoms, and combined short-segment posterior spinal instrumentation and fusion with anterior decompression and fusion (PSIF with AF) for cases with obvious neurological symptoms.

In this report, we review the postoperative results of our methods.

Methods: We have operated on 18 cases of burst fracture in the past seven years, eleven of them, who had been treated with PSIF (attachment of one level above the fracture to one level below the fracture), were selected for the subjects of the investigation. They consisted of 7 males and 4 females. The average age was 42 years and the mean follow-up of the postoperative image findings was one year and six months (range, eight months to two years and ten months). The number of the cases by traumatic ascensus was T11: 1, T12: 2, L1: 5, L2: 2. Among them, seven cases underwent PSIF. All the cases were operated on with a pedicle screw in combination with a hook. Four cases underwent PSIF with AF. In these cases, only a pedicle screw was used for the posterior, and only the bone transplantation after decompression was done for the anterior. For all cases, the angulation, alignment, and compliance were measured and examined before and after the operation using lateral radiographs, in addition to degree of improvement in the neurological symptoms.

Result: Preoperatively, the results of these cases showed that PSIF and PSIF with AF tend to cause larger damage to all of angulation, alignment, and compliance. Postoperatively, the difference in values between PSIF and PSIF with AF was small, and both groups maintained their respective values even with time. Based on the preoperative Frankel classification, the numbers of the cases undergoing PSIF were C: 1, D: 3, and E: 3. The numbers of the cases undergoing PSIF with AF were B: 1, C, 2, and E: 1. Improvement of one stage was seen in three cases undergoing PSIF. Improvement of two stages was seen in two cases undergoing PSIF with AF. No case showed postoperative deterioration of the neurological symptoms.

Conclusion: We perform PSIF with no neurological symptoms. In these cases, a pedicle screw and a hook are installed in the same vertebral body and arch to reduce the load on the pedicle screw and prevent the pedicle screw damage. AF is performed together with PSIF, and decompression is done surely for cases with obvious neurological symptoms. In these cases, a pedicle screw is used solely and no hook is used because there is a transplant bone as the prop in the anterior. At the moment, we cannot refer to the occurrence of kyphosis transformation in the future for lack of sufficient cases and length of the observation period. However, it was suggested that cases with no neurological symptoms could be treated with PSIF solely.

Purpose: In recent years, many reports have described spontaneous resorption of lumbar disc herniation evaluated with Gd-enhanced MRI. We also found retrospectively that sequestrated lumbar disc herniation with Gd-enhanced MRI would disappear, and that patient with this type of lumbar disc herniation would improve clinically. But there is a question that Gd-enhanced MRI is really needed to speculate the prognosis of sequestrated lumbar disc herniation. The purpose of this study is to clarify the prognostic value of Gd-enhanced MRI for sequestrated lumber disc herniation.

Materials and methods: Since Nov. 1995, 22 patients of sequestrated lumber disc herniation were treated non-operatively under the speculation of getting good clinical result prospectively. From Nov. 1995 to Oct. 1997, 9 patients with sequestrated lumbar disc herniation with ring-enhancement on Gd-enhanced MRI were treated non-operatively (Group A). From Nov. 1997 to July 2000, 13 patients with sequestrated lumbar disc herniation were treated non-operatively without Gd-enhanced MRI examination (Group B). Clinical results and the last MRI findings of Group A were compared with that of Group B.

Results: In Group A, all cases were treated non-operatively and all of them improved clinically within a month of the first MRI examinations. Mean period of NSAID administration was 37 days (range 14–67 days), and the last MRI examinations revealed that the herniated masses disappeared in 5 cases and that the size of herniations diminished in 4 cases. All of 9 cases obtained good clinical results. In Group B, all cases were treated non-operatively but one, whose clinical symptoms were not improved within a month of the first MRI examination. Mean period of NSAID administration was 38 days (range 7–110 days), and the last MRI examinations revealed that the herniated masses disappeared in 5 cases and that the size of herniations diminished in 5 cases. Remaining 2 cases, the second MRI was not examined for some reasons. All of 12 cases obtained good clinical results. There were no differences between Group A and Group B by means of clinical results.

Conclusions: Gd-enhanced MRI is not needed to speculate the prognosis of sequestrated lumbar disc herniation. In the case of sequestrated lumbar disc herniation, good clinical result could be obtained without Gd-enhanced MRI examination at the first MRI examination.