Gunshot wounds to the spine: literature review and report on a migratory intrathecal bullet.

Treatment of the complex injury to the spine produced by a gunshot wound remains controversial. Treatment depends on the physician's ability to understand mechanism of injury, principles of medical management, diagnostic imaging, and surgical options. Antibiotics are an important component of treatment and should be continued for a minimum of 7 days in cases of wounds that both perforate the colon and injure the spine. Corticosteroids do not affect neurologic outcome and therefore should not be used. Decompression and removal of intracanal bullets at T12 and below may improve motor function. In select cases of cervical injuries, removal of intracanal bullet fragments may be justified, particularly with incomplete lesions. Regardless of injury level, new-onset or progressive neurologic deterioration is an indication for urgent decompression. Optimal surgical timing remains a controversial issue, and more study is needed to develop treatment guidelines. Intrathecal migratory missiles represent a very rare subset of the gunshot wounds to the spine, and their treatment should be individualized. In this article, we review the literature and then describe the case of a migratory intrathecal bullet in the lumbar spine of a patient who presented with cauda equina-type symptoms.

A novel technique of intra-spinous process injection of PMMA to augment the strength of an inter-spinous process device such as the X STOP.

STUDY DESIGN: Biomechanical. OBJECTIVE: To determine if cement injection into the spinous process will improve compression strength. SUMMARY OF BACKGROUND DATA: The X STOP (St. Francis Medical Technologies) has been shown to be a safe and effective means for decompressing 1- or 2-level lumbar spinal stenosis (LSS). The X STOP is indicated for LSS patients with osteoporosis, but contraindicated for patients with severe osteoporosis. In an attempt to address these LSS patients with demonstrably weaker bone, a technique to strengthen the spinous process with polymethylmethacrylate (PMMA) injection is presented. METHODS: Nine pairs of adjacent fresh frozen cadaveric lumbar vertebrae were DEXA scanned before testing. They were randomly assigned to the PMMA group and a control group. Nine of the specimens were injected with PMMA. Each spinous process was then compressed between 2 X STOPs. The testing model was designed to simulate the loading of a 2-level X STOP placement. The mean load to failure and stiffness values of the treated and untreated groups were calculated. The specimens were inspected carefully for PMMA infiltration and extrusion. RESULTS: The mean bone mineral density (BMD) values of the control and PMMA treatment groups were 0.99 +/- 0.13 g/cm and 0.98 +/- 0.10 g/cm, respectively; P > 0.616. The mean volume of cement injected was 2.2 +/- 0.3 cc. The mean failure load values of the control and PMMA treatment groups were 1250 +/- 627 N and 2386 +/- 1034 N, respectively; P < 0.001. The mean stiffness values of the control and PMMA treatment groups were 296 +/- 139 N/mm and 381 +/- 131 N/mm, respectively; P > 0.059. Most specimens had flow of the cement into the laminae and some into the facet and pedicle. No PMMA was found within the spinal canal. CONCLUSION: This first reported technique of posterior element vertebroplasty may increase the indications and success for patients with decreased BMD who seek an interspinous implant such as the X STOP. A possible role may exist in increasing the effectiveness of such devices. However, clinical trials have yet been performed. These results demonstrate that PMMA injection in the spinous processes is effective in increasing resistance to compressive forces in an X STOP model.

ProDisc-L total disc replacement: a comparison of 1-level versus 2-level arthroplasty patients with a minimum 2-year follow-up.

STUDY DESIGN: This is a retrospective analysis of data that was collected prospectively from 2 concurrent FDA IDE lumbar arthroplasty clinical trials performed at a single center. OBJECTIVE: To determine if there is a clinical difference between the 1-level ProDisc patients versus the 2-level ProDisc patients at a minimum of 2 years of follow-up. SUMMARY OF BACKGROUND DATA: Marnay's work with ProDisc I prompted the U.S. Clinical Trials of the ProDisc II under the direction of the FDA. Disc replacement surgery in the United States has shown promising results for all types of prostheses up to 6 months. Marnay and colleagues showed that their results at 10 years were still promising, and they saw no significant difference between 1-level and multilevel disc replacements. The findings of Ipsen and colleagues suggest that multilevel arthroplasty cases may be less successful than disc replacement at a single level. METHODS: Patients were part of the FDA clinical trial for the Prodisc II versus circumferential fusion study at a single institution. We identified 27 patients who received ProDisc at 1 level and 32 who received it at 2 levels with at least a 2-year follow-up, for a total of 59 patients. Unpaired t tests were performed on the mean results of Visual Analog Scale, Oswestry Disability Index, SF-36 Healthy Survey Physical Component Summary, and satisfaction using 10-cm line visual scale scores to determine a clinical difference if any between the 2 populations. RESULTS: While patients receiving ProDisc at 2 levels scored marginally lower in all evaluation indexes, score differences in each category were also found to hold no statistical significance. CONCLUSION: This study was unable to identify a statistically significant difference in outcome between 1- and 2-level ProDisc arthroplasty patients in a cohort from a single center. The equality of clinical effectiveness between 1- and 2-level ProDisc has yet to be determined.

Vertebroplasty versus kyphoplasty: biomechanical behavior under repetitive loading conditions.

STUDY DESIGN: Ex vivo biomechanical study using osteoporotic cadaveric fractured vertebral bodies. OBJECTIVE: To investigate the behavior of fractured osteoporotic vertebral bodies treated with either vertebroplasty or kyphoplasty under repetitive loading conditions. SUMMARY OF BACKGROUND DATA: Vertebroplasty and kyphoplasty are newer alternatives for the treatment of osteoporotic vertebral fractures. Loading conditions that can lead to fractures treated with these methods will likely be encountered subsequently; as such, it is important to understand differences in the biomechanical behavior of the resultant constructs. METHODS: There were 7 pairs of osteoporotic T8 and T10 vertebral bodies cyclically loaded to produce a vertebral compression fracture. Of each pair, one was assigned to the kyphoplasty group and the other to the vertebroplasty group. After treatment, specimens were cyclically loaded to 100,000 cycles, between 20% and 70% of the predicted failure load. RESULTS: Height was restored with kyphoplasty, but the vertebral bodies showed significant height loss during cyclic loading. Vertebroplasty specimens had higher compression stiffness and smaller height reduction. CONCLUSIONS: Under repetitive loading conditions, fractured vertebral bodies treated with kyphoplasty were initially taller, but because of a progressive loss of height during loading, the resulting constructs were shorter after 100,000 cycles than those treated with vertebroplasty.

Interspinous process decompression with the X-STOP device for lumbar spinal stenosis: a 4-year follow-up study.

X-STOP is the first interspinous process decompression device that was shown to be superior to nonoperative therapy in patients with neurogenic intermittent claudication secondary to spinal stenosis in the multicenter randomized study at 1 and 2 years. We present 4-year follow-up data on the X-STOP patients. Patient records were screened to identify potentially eligible subjects who underwent X-STOP implantation as part of the FDA clinical trial. The inclusion criteria for the trial were age of at least 50 years, leg, buttock, or groin pain with or without back pain relieved during flexion, being able to walk at least 50 feet and sit for at least 50 minutes. The exclusion criteria were fixed motor deficit, cauda equina syndrome, previous lumbar surgery or spondylolisthesis greater than grade I at the affected level. Eighteen X-STOP subjects participated in the study. The average follow-up was 51 months and the average age was 67 years. Twelve patients had the X-STOP implanted at either L3-4 or L4-5 levels. Six patients had the X-STOP implanted at both L3-4 and L4-5 levels. Six patients had a grade I spondylolisthesis. The mean preoperative Oswestry score was 45. The mean postoperative Oswestry score was 15. The mean improvement score was 29. Using a 15-point improvement from baseline Oswestry Disability Index score as a success criterion, 14 out of 18 patients (78%) had successful outcomes. Our results have demonstrated that the success rate in the X-STOP interspinous process decompression group was 78% at an average of 4.2 years postoperatively and are consistent with 2-year results reported by Zucherman et al previously and those reported by Lee et al. Our results suggest that intermediate-term outcomes of X-STOP surgery are stable over time as measured by the Oswestry Disability Index.

The monotonic and fatigue properties of osteoporotic thoracic vertebral bodies.

STUDY DESIGN: Measurement of the monotonic and fatigue properties of osteoporotic thoracic vertebral bodies. OBJECTIVES: To determine the loading values at which osteoporotic vertebral bodies are susceptible to failure. SUMMARY OF BACKGROUND DATA: Vertebral compression fractures are the most common osteoporotic fracture. Eighty-three percent of vertebral compression fractures are caused by moderate or less trauma, and there is not a specific traumatic event in 59% of these cases. Fatigue loading can lead to premature failure, although the relationship between loading and cycles to failure is not well established. METHODS: Eighteen osteoporotic thoracic vertebral bodies were tested in monotonic compression to determine the correlation between the bone mineral content and the ultimate compressive load. Seventeen osteoporotic thoracic vertebral bodies were cyclically loaded at varying percentages of the ultimate compressive load until failure to determine the relationship between loading and fatigue life. RESULTS: The bone mineral content was linearly correlated with ultimate compressive load. Based on our regression analysis, a 10% decrease in bone mineral content will lead to an approximate 10% decrease in ultimate compressive load. The percentage of ultimate compressive load was inversely correlated to the logarithm of cycles to failure, with specimens loaded at 60%, 70%, and 80% of ultimate compressive load lasting on average 5.6 x 10, 4.0 x 10, and 31 cycles to failure, respectively. CONCLUSIONS: The bone mineral content is a strong predictor of the ultimate compressive load, while the percentage of the ultimate compressive load is a strong predictor of the cycles to failure for osteoporotic thoracic vertebral bodies.

Diagnostic evaluation of low back pain.

The diagnostic evaluation of chronic LBP is at best a complex and involved undertaking. The most important part of the process lies in the knowledge of the patient and a solid history and physical examination. From there, most of the serious and life-threatening causes of LBP can be elucidated and studies may be used for confirmation. Imaging studies are used most practically as confirmation studies once a working diagnosis is determined. MRI, although excellent at defining tumor, infection, and nerve compression, can be too sensitive with regard to degenerative disease findings and commonly displays pathology that is not responsible for the patient's symptoms. As an example, the high-intensity zones (HIZ) seen on MRI are reliable in determining annular defects in the disc but are not reliable in establishing internal disc disruption as the cause of LBP. Discography is the primary tool used by many physicians to determine the true pain generator when discogenic LBP is suspected. Because the reliability of the patient response is fundamental to discography, interpreting the test in different settings must be considered. In individuals with disc degeneration and annular defects, discography may elicit LBP with injection whether the patient is symptomatic with serious LBP or not. The pain response may be amplified in those subjects with issues of chronic pain, social stressors, such as secondary gain or litigation claims, or psychologic distress disorder. These factors have been shown experimentally to be associated with an increased risk for a false positive injection. The ability of an individual to differentiate the true site of LBP by the quality of sensation with disc injection (concordancy) of pain produced by the injected disc also may not be reliable. In fact, individuals may not have the neural discrimination to differentiate sclerotomal pain originating from different sites in the low back and pelvis. One may realize that chronic LBP illness may not stem from a mechanical spinal disorder alone. In fact, the mechanical pathology may be just a portion of the problem with amplification by neurophysiologic, social, and psychologic issues. Chronic disabling LBP commonly is confounded by chronic pain, emotional troubles, poor job satisfaction, alcohol and narcotic abuse, and compensation issues, just to identify a few. It would follow that expecting to identify a single cause for this symptom complex is impractical and any single test may not be a reasonable approach. Furthermore, surgical correction of the mechanical portion of chronic LBP. even if correctly identified, then can be expected only to relieve a portion of a patient's symptoms as long as the confounding issues continue to be significant or have become life long adaptive mechanisms. In the end, the discogram and other diagnostic tests are tools that have clear limitations. In this field, clinical judgment begins and ends with an understanding of a patient's life and circumstances as much as with their specific spinal pathology.