Early failure of bioabsorbable anterior cervical fusion plates: case report and failure analysis.

STUDY DESIGN: Case report with forensic failure analysis. OBJECTIVE: To determine the failure modes of 3 explanted 70:30 PLDLA Mystique (Medtronic Sofamor Danek, Memphis, TN) graft containment plates retrieved from revision surgery for early device failure. SUMMARY OF BACKGROUND DATA: To reduce the problems of stress-shielding and radiopacity associated with metallic systems, bioabsorbable polymers have been used in anterior cervical discectomy and fusion procedures. Degradation of mechanical properties in vivo is a major concern when using bioabsorbable systems. Three of 6 patients who underwent anterior cervical discectomy with instrumented fusion, using Mystique graft containment systems experienced early failure requiring revision to alternate hardware. METHODS: Devices were retrieved after failure and analyzed by light microscopy and environmental scanning electron microscopy. Simulations were performed with an unused plating system to induce damage for comparison with the retrieved devices. A detailed case review was performed to identify possible sources of extraordinary loading or damage. RESULTS: One plating system failed at 6 weeks postimplantation due to fatigue fracture of the screws. Crack initiation sites were identified at the interface of the thread root and mold line of the screw. Another plating system failed at 16 weeks postimplantation due to the coalescence of radial microcracking between holes in the plate, leading to catastrophic failure of the plate. The final plating system failed during the implantation surgery, when the screw fractured in torsion. CONCLUSIONS: Stress concentrations at the screw head-shaft interface and thread-shaft interface reduce the fatigue performance of bioabsorbable screws. Hydrolysis of the polymer may also play a role in the reduction of resistance to crack initiation and propagation.

End organ effects of high-dose human equivalent methylprednisolone in a spinal cord injury rat model.

STUDY DESIGN: Interventional study. OBJECTIVE: To analyze the histologic effects of high-dose human equivalent methylprednisolone on the pulmonary, cardiac, intestinal, renal, hepatic, and splenic tissues in a spinal cord injury rat model. SUMMARY OF BACKGROUND DATA: There are numerous investigations of various medical interventions for the treatment of acute spinal cord trauma. Currently, the only generally accepted medical intervention in an acute spinal cord trauma is the intravenous administration of high doses of methylprednisolone. Although it has been nearly 2 decades since the first National Acute Spinal Cord Injury Study investigated the role high-dose steroids might play in the treatment of acute spinal cord trauma, controversy still exists regarding the efficacy of this treatment. To our knowledge, no study has examined the role of high-dose methylprednisolone in organ systems other than the spinal cord in an acute spinal cord injury model at the histologic level. This study attempts to characterize end organ histologic response to human dose equivalent (HDE) intravenous methylprednisolone administration in a rodent model of acute spinal cord injury. METHODS: A total of 48 Sprague-Dawley rats were divided equally into control and experimental groups. Each group was subdivided into 6 sets of 4 animals each, according to intervals after injury. Groups 1-6 consisted of animals euthanized at 0, 4, 8, 16, 24, and 48 hours after spinal cord injury. Paraplegia after lower thoracic laminectomy was achieved using a standardized Allen weight drop technique. Within 1 hour of injury, experimental animals were treated with HDE methylprednisolone, infused for 23 hours continuously. Liver, kidney, lung, intestine, spleen, and heart were harvested at variable intervals after injury and prepared for histologic examination. These slides were analyzed with microscopic staining techniques and compared in a blinded manner by a qualified pathologist. RESULTS: Of all the end organs analyzed, the spleens were most affected. Lymphocytic depletion was seen in as little as 4 hours after methylprednisolone infusion and continued until 48 hours. Pulmonary tissues variably showed interstitial congestion and eosinophilic alveolar collections. Intestinal mucosal tissues showed edema and autolyzed mucosa from 16 hours onwards. Cardiac, kidney, and hepatic tissue did not differ significantly from controls. CONCLUSIONS: Histologically, HDE methylprednisolone caused significant splenic lymphocytic depletion changes in as little as 4 hours. This trend of end organ lymphocytopenia continued to progress until 48 hours. Pulmonary eosinophilic infiltrates were seen from 8 until 24 hours. Intestinal mucosal edema and necrosis were seen in samples at 16 hours throughout 48 hours. This study was designed to evaluate end organ changes seen in an animal model of an acute spinal cord injury treated with HDE methylprednisolone. Study animals were infused with HDE methylprednisolone given according to the National Acute Spinal Cord Injury Study II protocol. The kidney, lung, cardiac, intestinal, splenic, and hepatic tissues from the aforementioned animals were then sectioned and analyzed using histologic staining techniques by a qualified pathologist.

Surfing for scoliosis: the quality of information available on the Internet.

STUDY DESIGN: A cross section of Web sites accessible to the general public was surveyed. OBJECTIVE: To evaluate the quality and accuracy of information on scoliosis that a patient might access on the Internet. SUMMARY OF BACKGROUND DATA: The Internet is a rapidly expanding communications network with an estimated 765 million users worldwide by the year 2005. Medical information is one of the most common sources of inquires on the Web. More than 100 million Americans accessed the Internet for medical information in the year 2000. Undoubtedly, the use of the Internet for patient information needs will continue to expand as Internet access becomes more readily available. This expansion combined with the Internet's poorly regulated format can lead to problems in the quality of information available. Since the Internet operates on a global scale, implementing and enforcing standards have been difficult. The largely uncontrolled information can potentially negatively influence consumer health outcomes. METHODS: To identify potential sites, five search engines were selected and the word "scoliosis" was entered into each search engine. A total of 50 Web sites were chosen for review. Each Web site was evaluated according to the type of Web site, quality content, and informational accuracy by three board-certified academic orthopedic surgeons, fellowship trained in spinal surgery, who each has been in practice for a minimum of 8 years. Each Web site was categorized as academic, commercial, physician, nonphysician health professional, and unidentified. In addition, each Web site was evaluated according to scoliosis-specific content using a point value system of 32 disease-specific key words pertinent to the care of scoliosis on an ordinal scale. A list of these words is given. Point values were given for the use of key words related to disease summary, classifications, treatment options, and complications. The accuracy of the individual Web site was evaluated by each spine surgeon using a scale of 1 to 4. A score of 1 represents that the examiner agreed with less than 25% of the information while a score of 4 represents greater than 75% agreement. RESULTS: Of the total 50 Web sites evaluated, 44% were academic, 18% were physician based, 16% were commercial, 12% were unidentified, and 10% were nonphysician health professionals. The quality content score (maximum, 32 points) for academic sites was 12.6 +/- 3.8, physician sites 11.3 +/- 4.0, commercial sites 11 +/- 4.2, unidentified 7.6 +/- 3.9, and nonphysician health professional site 7.0 +/- 1.8. The accuracy score (maximum, 12 points) was 6.6 +/- 2.4 for academic sites, 6.3 +/- 3.0 for physician-professional sites, 6.0 +/- 2.7 for unidentified sites, 5.5 +/- 3.8 for nonphysician professional sites, and 5.0 +/- 1.5 for commercial Web sites. The academic Web sites had the highest mean scores in both quality and accuracy content scores. CONCLUSION: The information about scoliosis on the Internet is of limited quality and poor information value. Although the majority of the Web sites were academic, the content quality and accuracy scores were still poor. The lowest scoring Web sites were the nonphysician professionals and the unidentified sites, which were often message boards. Overall, the highest scoring Web site related to both quality and accuracy of information was www.srs.org. This Web site was designed by the Scoliosis Research Society. The public and the medical communities need to be aware of these existing limitations of the Internet. Based on our review, the physician must assume primary responsibility of educating and counseling their patients.

A multicenter study of the outcomes of the surgical treatment of adolescent idiopathic scoliosis using the Scoliosis Research Society (SRS) outcome instrument.

STUDY DESIGN: A multicenter study of the outcomes of the surgical treatment of adolescent idiopathic scoliosis using the Scoliosis Research Society Questionnaire (SRS 24). OBJECTIVE: To evaluate the patient based outcome of the surgical treatment of adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: A paucity of information exists with respect to patient measures of outcome regarding the surgical treatment of adolescent idiopathic scoliosis. To our knowledge, no prospective outcome study on this topic thus far exists. METHODS: Using the SRS 24 questionnaire, seven scoliosis centers agreed to prospectively assess outcome for surgically treated patients with adolescent idiopathic scoliosis. Data were collected before surgery and at 24 months after surgery. Data were analyzed using paired and independent samples t test for all seven SRS 24 questionnaire domains (Pain, General Self-Image, Postoperative Self-Image, Postoperative Function, Function From Back Condition, General Level of Activity, and Satisfaction) using Statistical Package for Social Science. The domains were analyzed with respect to the total cohort, gender, curve magnitude, and type of surgery using independent-samples t tests. RESULTS: A total of 242 patients were included in our analysis. A baseline preoperative pain level of 3.68 of 5 was found. This improved to 4.63 after surgery, representing an improvement of 0.95 points. Surgical intervention was associated with improving outcome when compared with preoperative status. Pain, General Self-Image, Function From Back Condition, and Level of Activity all demonstrated statistically significant improvement as compared with preoperative status (P < 0. 001). Overall, patients were highly satisfied with the results of surgery. CONCLUSION: Preoperative pain exists in our adolescent scoliosis population. Pain scores were improved in our study population at the 2-year postsurgical follow-up. Statistically significant improvements were likewise seen in the General Self-Image, Function From Back Condition, and Level of Activity domains. The present study demonstrates the ability of surgery to improve the outcome of patients afflicted with adolescent idiopathic scoliosis.

Anatomic consideration for standard and modified techniques of cervical lateral mass screw placement.

BACKGROUND CONTEXT: Posterior screw placement techniques have been previously described. Each technique differs with respect to starting point, lateral angulation and sagittal orientation. PURPOSE: To examine the potential for injury to critical anatomic structures, such as nerve roots and vertebral arteries, during posterior cervical screw placement and to determine safe screw placement. STUDY DESIGN/SETTING: An anatomic study was conducted to determine the optimal screw angulation for posterior cervical lateral mass screws. SPECIMEN SAMPLE: Ten fresh-frozen human cadaveric cervical spine specimens were used, consisting of four females and six males, ranging in age from 32 to 68 years. OUTCOME MEASURES: Angular measurements and distance from nerve root and vertebral arteries were measured with a single caliper and recorded. One millimeter of proximity to a vital structure was considered a violation of that structure. METHODS: Ten fresh-frozen human cadaveric cervical spine specimens were instrumented from C2 to C7 by a single surgeon. Kirschner wires (2.0 mm) were used to reproduce the Roy-Camille, Anderson and Magerl screw trajectories. The wire was drilled through each lateral mass, simulating overdrill error. Each technique was instrumented according to the original description and with additional modifications. The modification consisted of varying the angle of screw placement in the axial plane of the original description from 0 to 30 degrees. Distances to the closest neurovascular structures were averaged for all assays. RESULTS: The Magerl technique is safe at the standard position and modified positions of 20 degrees and 30 degrees from C3-C6. The Roy-Camille technique frequently violates neurovascular structures below C3, especially the nerve root with more lateral screw angulation. The standard technique is noted to have good bone purchase only at C2 and C3. The Anderson technique is safe at 20 degrees and 30 degrees modified positions from C3-C7. Posterior screw placement at the C7 vertebral level was safe only with a modified Anderson technique of 20 degrees and 30 degrees of lateral screw angulation. CONCLUSIONS: The present study indicates that there are significant differences of potential neurovascular injury, which is dependent on the technique used for screw entry, the level instrumented and the angle of screw trajectory in the parasagittal plane.