The effect of surgically implanted bullet fragments on the spinal cord in a rabbit model.

BACKGROUND: Whether or not to remove bullets or bullet fragments from the spinal column of a neurologically intact patient has been a subject of continual debate. The controversy is due in part to a lack of information about the long-term effects of bullet fragments on spinal cord tissue. Although many studies have demonstrated the toxic effects of metal fragments on brain tissue, to our knowledge no one has evaluated the effects of the metals contained in commercially available bullets on spinal cord tissue. METHODS: Copper, aluminum, and lead fragments from three commercially available bullet cartridges were implanted in intradural and extradural locations in seventeen New Zealand White rabbits. At an average of 9.8 months, the metal content of specimens of blood, cerebrospinal fluid, and liver were determined. The spinal cords were harvested and examined histologically. RESULTS: There was a significant increase in the copper level of blood from the rabbits with an implanted copper fragment compared with that of the control animals (p = 0.007). Concentrations of copper and lead were not elevated, compared with the control values, in the serum or liver. Histological examination of the spinal cords revealed major destruction of both the axons and the myelin of the dorsal column adjacent to the intradural copper fragments. Intradural fragments of lead caused similar destruction of myelin and axons in the dorsal column, but to a lesser degree. Minimal spinal cord or meningeal histological changes were noted around the aluminum intradural fragments, and no pathological changes were found near any fragments placed in an extradural location. CONCLUSIONS: The results of this study show that certain metals contained in commercially available bullets can cause varying degrees of neural destruction independent of the initial mechanical injury caused by implantation. Of the three metals tested, copper fragments consistently caused a substantial localized area of neural injury within the spinal cord. CLINICAL RELEVANCE: In our study, copper fragments caused local neural toxicity involving as much as 10% of the spinal cord area, suggesting that there may be a scientific basis for removal of copper fragments lodged in the spinal cord, even in the absence of a neurological deficit.

Fungal infections of the spine. Report of eleven patients with long-term follow-up.

BACKGROUND: Fungal infections of the spine are noncaseating, acid-fast-negative infections that occur primarily as opportunistic infections in immunocompromised patients. We analyzed eleven patients with spinal osteomyelitis caused by a fungus, and we developed suggestions for treatment. METHODS: All patients with a fungal infection of the spine treated by the authors over a sixteen-year period at three teaching institutions were evaluated. There was a total of eleven patients. Medical records and roentgenograms were available for every patient. Long-term follow-up of the nine surviving patients was performed by direct examination by the authors or by the patient's primary physician. RESULTS: For ten of the eleven patients, the average delay in the diagnosis was ninety-nine days. Nine patients were immunocompromised secondary to diabetes mellitus, corticosteroid use, chemotherapy for a tumor, or malnutrition. The sources of the spinal infections included direct implantation from trauma (one patient), hematogenous spread (four patients), and local extension (two patients). The infection followed elective spine surgery in three patients, and the cause was unknown in one. Paralysis secondary to the spine infection developed in eight patients. Ten patients were treated with surgical debridement. All eleven patients were treated with systemic antifungal medications for a minimum of six weeks. One patient died of generalized sepsis at thirty-three days, and another patient died of gastrointestinal hemorrhage at five months. After an average of 6.3 years of follow-up, the infection had resolved in all nine surviving patients. CONCLUSIONS: Treatment of fungal spondylitis is often delayed because of difficulty with the diagnosis. Delay in the diagnosis led to poorer results in terms of neurologic recovery in our study. Performing fungal cultures whenever a spinal infection is suspected might hasten the diagnosis. Patients should be given a guarded prognosis and informed of the many possible complications of the disease.

Neurologic complications after lumbar spine surgery.

With the increasing complexity and number of lumbar spine operations being performed, the potential number of patients who will sustain perioperative complications, including those that involve neural structures, has also increased. Neurologic complications after lumbar spine surgery can be categorized by the perioperative time period during which they occur and by their mechanism of injury. Although the overall incidence of neurologic complications after lumbar surgery is low, the severity of these injuries mandates careful preoperative planning, awareness of risk, and meticulous attention to perioperative details.

Effects of epidural steroids on lumbar dura material properties.

Epidural steroid injections are commonly used in the treatment of low back pain and radiculopathy based on their antiinflammatory and analgesic benefits. However, steroids are known to affect collagen synthesis, material strength, and tissue healing. The purpose of this study was to assess the effects of serial epidural steroid injections on the material properties of the lumbar dura mater. Serial epidural steroid injections of saline or methylprednisolone at 2-week intervals were performed in three paired groups of canines; a separate noninjected group was used as controls. Postmortem, dural sample testing to failure and histologic analysis was performed. Mechanical failure testing revealed no clinically significant change in the transverse dorsal dura tensile strength between all saline-injected, steroid-injected, or noninjected controls. Histologic analysis demonstrated no overt disruption of collagen matrix organization; however, electron microscopy demonstrated a significant decrease in the number of intracytoplasmic mitochondria of dural fibroblasts in steroid-injected animals, suggesting a metabolic inhibitory effect within steroid-injected dura mater. In the clinical time frame of this study, serial epidural steroid injections appeared to produce no significant material or matrix changes in the lumbar dura.

Early failure of long segment anterior cervical plate fixation.

A retrospective, multicenter study was undertaken to evaluate the early postoperative failure rate of long segment anterior cervical fusion and plating to stabilize the cervical spine after a two- or three-level corpectomy for degenerative, traumatic, and neoplastic diseases of the cervical spine. Patient demographic factors as well as technical factors such as bone graft placement, plate and screw position, and postoperative brace immobilization were analyzed. During the early postoperative period, the graft/plate construct dislodged in 3 of 33 patients with a two-level corpectomy and fusion (9%) compared with 6 of 12 patients with a three-level corpectomy and fusion (50%). The difference in failure rates after a three- versus two-level corpectomy and fusion was statistically significant (p < 0.05). A higher early failure rate was also seen with failure to correctly lock the screws to the plate and the use of a peg-in-hole type bone grafting technique, although these differences were not statistically significant. Although several technical and patient-specific factors may contribute to this, anterior cervical plating and bone grafting alone after a three-level cervical corpectomy for various spinal disorders appears to afford inadequate stability in the early postoperative period, regardless of immobilization methods.

Complications in spinal fusion.

Complications in spinal fusion can lead to less than desirable results. The complications of spinal fusion in the cervical and lumbar spine are discussed. Methods of avoiding and correcting complications also are reviewed. Through a better understanding, it is hoped that complications can be prevented.

Efficacy of five cervical orthoses in restricting cervical motion. A comparison study.

STUDY DESIGN: Twenty volunteers, 10 men and 10 women, with clinically and radiographically normal cervical spines were studied. OBJECTIVES: To evaluate the effectiveness of five cervical orthoses in their ability to restrict cervical motion in flexion, extension, lateral tilt, rotation, and intervertebral motion. SUMMARY OF BACKGROUND DATA: The five cervical orthoses evaluated were the Philadelphia collar (Philadelphia Collar Co., Philadelphia, PA), Aspen (International Healthcare Devices, Long Beach, CA), Stifneck (Laerdal, Armonk, NY), Miami J (Jerome Medical, Moorestown, NJ), and NecLoc (Jerome Medical, Moorestown, NJ) orthoses. Together these five orthoses comprise 80% of the rigid cervical and extrication devices in current use. METHODS: The normal and unrestricted ranges of active cervical motion in flexion, extension, and lateral tilt were measured in each subject and compared with the motion permitted in each of the five cervical orthoses. Lateral radiographs of the cervical spine in the neutral position and at maximum flexion and extension were obtained. Measurements of flexion, extension, and combined flexion-extension were determined for the cervical spine as a whole as measured from the occiput to the seventh cervical vertebra and at each intervertebral cervical level. Lateral tilt was measured on an anteroposterior radiograph at the extreme of motion. Rotation was measured using a compass goniometer. Each volunteer served as his own control for the radiographic and goniometric measurements. RESULTS AND CONCLUSION: The NecLoc cervical orthosis demonstrated statistically superior restriction of cervical motion in flexion, extension, rotation, and lateral tilt in comparison with the other four orthoses studied in healthy volunteers. The Miami J cervical orthosis was the next most restrictive orthosis and was superior to the Philadelphia Collar and Aspen orthosis in all parameters of motion.

Carbon monoxide levels in cell saver salvaged blood exposed to electrocautery during lumbar spine surgery.

Carboxyhemoglobin levels were measured in patients undergoing posterior lumbar spine surgery with use of intraoperative cell saver blood salvage. Increased carboxyhemoglobin levels were demonstrated in cell saver salvaged blood. Systemic blood carboxyhemoglobin levels increased with cell saver blood transfusion. No patient demonstrated clinical effects of carbon monoxide toxicity.

Gentamicin penetration into normal rabbit nucleus pulposus.

STUDY DESIGN: Radioactively labeled gentamicin was administered to 24 rabbits to assess the concentration of antibiotic in the nucleus pulposus. OBJECTIVES: The purpose of the study was to investigate the pharmacokinetics of gentamicin penetration into normal rabbit nucleus pulposus. SUMMARY OF BACKGROUND DATA: Disc space infection is a complication of spinal surgery that can be prevented by prophylactic antibiotics. Gentamicin can be used in conjunction with other antibiotics as a prophylactic agent. One previous study demonstrated that a similar antibiotic, tobramycin, penetrates the disc, but no data have been reported on the pharmacokinetics of disc penetration. METHODS: Twenty-four rabbits were given an intravenous injection of gentamicin labeled with iodine 125. Four rabbits were killed at hourly intervals 1 to 6 hours after injection. Specimens of nucleus pulposus, blood, whole liver, and saline-perfused liver were obtained and prepared. The radioactivity in the specimens was measured. RESULTS: The gentamicin concentration in the nucleus pulposus peaked at 2 hours and remained at this level for the duration of the experiment. Twenty percent of the gentamicin recovered from the nucleus pulposus was tissue bound. CONCLUSIONS: Gentamicin concentration in the rabbit nucleus pulposus does not peak until 2 hours after an intravenous bolus of drug. If gentamicin penetrates human nucleus pulposus in a similar fashion, this study could have implications for the timing of administration of this agent for prophylaxis.

Tissue distribution of antibiotics in the intervertebral disc.

STUDY DESIGN: This study analyzed the distribution of antibiotics within the intervertebral disc of rabbits. Specimens were tested with specific antibodies against antibiotics using an immunofluorescent technique. OBJECTIVES: The results were correlated to provide a rationale for perioperative prophylaxis of infection. SUMMARY OF BACKGROUND DATA: Several groups of investigators and the recent data from our laboratory showed quantitative changes in penetration of antibiotics into intervertebral disc. No previous study has assessed antibiotic distribution in anulus fibrosus and nucleus pulposus. METHODS: Discs were obtained from rabbits after intravenous injection of penicillin or gentamicin. Antibiotics were localized in tissue sections using specific antibodies with a immunofluorescent method. RESULTS: Penicillin (negatively charged) and gentamicin (positively charged) penetrated the neutrally charged anulus fibrosus, but penicillin had less ability than gentamicin to penetrate into the negatively charged nucleus pulposus. CONCLUSION: Our data suggest that penetration and distribution of antibiotics into avascular intervertebral disc is significantly influenced by the charge of antibiotics.

The fate of autogenous bone graft in surgically treated pyogenic vertebral osteomyelitis.

A retrospective study of all surgically treated patients with pyogenic vertebral osteomyelitis grafted with autogenous bone for stability from 1980 to 1985 at the University of Miami and from 1985 to 1987 at Portsmouth Naval Hospital was performed. Eradication of infection occurred in all patients. Infection resolution occurred equally well in cases caused by gram-positive, gram-negative, and multiple organisms. In those patients requiring surgical treatment for pyogenic vertebral osteomyelitis, we found placement of autogenous bone graft at the time of primary debridement not to hinder eradication of infection. Arthrodesis occurred in 96% of the cases (26 of 27 patients).

Transthoracic disc excision and fusion for herniated thoracic discs.

Transthoracic discectomy and fusion were performed on 19 patients for a central or central-lateral herniated thoracic disc. At initial visit, 14 patients had evidence of myelopathy, 5 had bowel or bladder dysfunction, and 13 had pain. Previous laminectomy in three patients compromised the result of later anterior decompression. Coexistent multiple sclerosis was diagnosed in two patients, who had an atypical postoperative course. The overall results of transthoracic discectomy and fusion in patients without prior laminectomy or coexistent multiple sclerosis were excellent in six, good in six, fair in one, and poor in one, demonstrating that it is a safe and effective procedure.

Diagnosis of subtle thoracolumbar burst fractures. A new radiographic sign.

A previously undescribed radiographic sign, the posterior vertebral body angle is successful in distinguishing subtle burst type fractures from compression fractures of the thoracolumbar spine. Correct diagnosis is imperative for proper treatment and accurate prognosis. When positive, this sign will alert the orthopaedist so that further diagnostic testing with computed tomography or sagittal tomograms may be performed. The sensitivity of this sign in diagnosing subtle burst type injuries is 75%.

Atypical hangman's fractures.

Nineteen cases of traumatic spondylolisthesis of the axis, including 13 standard hangman's fractures and 6 anterolistheses of the C2 vertebral body associated with Effendi's atypical hangman's fractures, were studied. Unlike the standard Effendi Type I or Type II fractures, atypical hangman's fractures, occurring through the posterior aspect of the vertebral body with unilateral or bilateral continuity of the posterior cortex or pedicle, routinely narrow the spinal canal because of the fracture pattern and degree of subluxation. These atypical C2 injuries were more frequent and more often accompanied by paralysis (33%) than was previously anticipated. Because of their greater potential for neurologic compromise, it is essential that these fractures be recognized as distinct from standard Types I and II C2 fractures. Larger series should clarify both the true incidence of paralysis and long-term results from these unique C2 injuries.

A biomechanical evaluation of magnetic resonance imaging-compatible wire in cervical spine fixation.

In a bovine cervical spine model, the ultimate and fatigue strengths as well as relative magnetic resonance imaging artifact produced by titanium, cobalt chrome, and stainless-steel wires in various gauges were assessed. Single-cycle and fatigue strength of wire constructs were measured. Although larger wires generally had greater static strength, fatigue strength was mixed. Sixteen-gauge titanium, and all stainless-steel models (22-gauge braided, 18-gauge, and Songer cable) withstood 10,000 cycles without failure, whereas all other constructs rarely could withstand a similar 10,000 cycles. Magnetic resonance imaging was performed on calf cervical spines instrumented with the various materials. Titanium exhibited the least artifact, stainless-steel showed the greatest artifact, and cobalt chrome an intermediate amount. Although titanium wire produces the least amount of magnetic resonance imaging artifact, it remains a poor choice for implant fixation because its notch sensitivity reduces its fatigue resistance compared with stainless steel, which remains the more dependable choice.

Penetration of glycopeptide antibiotics in nucleus pulposus.

The penetration of the glycopeptide antibiotics vancomycin and teicoplanin into the nucleus pulposus of rabbits was studied. Blood samples were obtained at 0.5, 1, 4, 8, and 24 hours after intravenous administration of 30 mg/kg vancomycin or 16 mg/kg teicoplanin. Concentrations of antibiotics were determined in tissue specimens and serum samples by fluorescence polarization immunoassays. Antimicrobial activity in the nucleus pulposus was determined with an agar diffusion method using a strain of Micrococcus luteus as the indicator organism. A peak concentration of vancomycin in the nucleus pulposus was attained 8 hours after drug administration. Teicoplanin reached its maximum level and plateaued 1 and 2 hours, respectively, after injection, and it remained unchanged for the rest of the study. This microbiologic analysis showed that the nucleus pulposus contained an antimicrobial level of glycopeptide antibiotics after administration. Because rabbit nucleus pulposus is similar anatomically to that of humans, these results may have implications regarding the timing and choice of antibiotic administration.

Nonoperative management of stable thoracolumbar burst fractures with early ambulation and bracing.

Eighteen neurologically intact patients with burst fractures at the thoracolumbar junction were treated with early ambulation in a total contact orthosis. No attempt was made to reduce the associated deformity. Selection criteria excluded patients with posterior column disruption. Hospital stay averaged 10 days. Follow-up averaged 19 months. Mean kyphosis was 19 at time of injury and 20 at follow-up. At follow-up, 15 patients rated their pain as little or none. Seventeen patients had little or no restriction of activity. Follow-up computed tomography (CT) scans obtained in eight patients showed significant resorption of retropulsed bone. No deterioration of neurologic function developed in any patient. In patients with intact posterior elements and thoracolumbar burst fractures, early mobilization in a total contact TLSO can lead to satisfactory functional results. Prolonged bed rest was not required in this series. The authors attribute the good results of nonoperative management to the exclusion of patients with posterior column disruption.