Keith H. Bridwell

Free-Hand Pedicle Screw Placement During Revision Spinal Surgery : Analysis of 552 Screws

Study Design. A retrospective study. Objective. To evaluate the safety of free-hand pedicle screw placement during revision surgery at levels with a solid posterior fusion mass and/or identified pseudarthroses of the thoracic and lumbosacral spine. Summary of Background Data. Placement of pedicle screws into previous fusion masses or pseudarthrosis levels of the spine is challenging because of the loss of anatomic landmarks. We are aware of no study focusing on screw placement without any type of radiographic or navigational assistance. Methods. Thirty-seven patients underwent revision spinal surgery with posterior spinal instrumentation and fusion using 552 transpedicular screws by a single surgeon from 1994 to 2003. Among 552 screws, 184 were inserted into virgin levels, 60 were inserted into the vertebral body through previous screw holes, 208 were inserted into fusion masses, and 100 were inserted into pseudarthrosis levels. We used the quadrangulation method to gain pedicle access in a prior fusion mass after diligent exposure of any and all visible anatomic landmarks. All screws were analyzed using radiographs, intraoperative monitoring data, and clinical outcomes. Results. There were 29 women and 8 men. The mean age of patients at the time of surgery was 38 + 6 years (range, 8–75 years). Six screws were removed intraoperatively according to the triggered electromyography criteria and 4 of them were repositioned after checking the integrity of the pedicle by a careful probing technique (1.09%). Six screws were removed after checking the intraoperative radiographs and 5 screws were misplaced, as noted, in postoperative radiographs (1.99%). Two patients underwent revision surgery at 3 days and 6 weeks after initial surgery, respectively, for root decompression at the osteotomy site although screw positions were correct. Conclusion. The free-hand technique of thoracic and lumbosacral pedicle screw placement in revision spinalsurgery is reliable and safe when using the quadrangulation method of gaining pedicle access in a prior fusion mass or at pseudarthrosis levels.

Failure of Intraoperative Monitoring to Detect Postoperative Neurologic Deficits: A 25-year Experience in 12,375 Spinal Surgeries

Study Design. Retrospective. Objective. The purpose was to categorize and evaluate intraoperative monitoring (IOM) failure to detect neurologic deficits occurring during spinal surgery. Summary of Background Data. The efficacy of spinal cord/nerve root monitoring regarding undetected neurologic deficits is examined in a large, single institution series involving all levels of the spinal column and all spinal surgical procedures. Methods. Multimodality IOM included somatosensory-evoked potentials (SSEPs), descending neurogenic-evoked potentials (DNEPs), transcranial motor-evoked potentials (MEPs), dermatomal somatosensory-evoked potentials (DSEPs), and spontaneous and triggered electromyography (spEMG, trgEMG). We reviewed 12,375 patients who underwent surgery for spinal pathology from 1985 to 2010. There were 7178 females (59.3%) and 5197 males (40.7%); 9633 (77.8%) primary surgeries and 2742 (22.2%) revisions. Procedures by spinal level were cervical 29.7% (3671), thoracic/thoracolumbar 45.4% (5624), and lumbosacral 24.9% (3080). Age at surgery was > 18 years - 72.7% (8993) and < 18 years - 27.3% (3382). Results. Forty-five of the 12,375 patients (0.36%) had false negative outcomes. False negative results by modality were as follows: spEMG (n = 22, 48.8%), trgEMG (n = 8, 17.7%), DSEP (n = 4, 8.8%), DNEP (n = 4, 8.8%), SSEP (n = 3, 6.6%), DSEP/spEMG (n = 3, 6.6%), and trgEMG/spEMG (n = 1, 2.2%). Thirty-seven patients had immediate postoperative deficits unidentified by IOM; 30 patients (81%) involved nerve root monitoring, four patients had spinal cord deficits, and three patients had peripheral sensory deficits. Eight patients had permanent neurologic deficits, six (0.048%) were nerve root and two (0.016%) were spinal cord in nature. Conclusion. Despite correct application and usage, IOM data failed to identify 45 (0.36%) patients with false negative outcomes out of 12,375 surgical patients. Eight patients (0.064%) of these 45 patients had permanent neurologic deficits, six patients had nerve root deficits in nature and two patients had spinal cord deficits. Although admittedly small, this represents the risk of undetected neurologic deficits even when properly using IOM. Deficits are at a higher risk to remain unresolved when not detected by IOM. Level of Evidence: 4

Corticosteroids Can Reduce the Severity of Scoliosis in Duchenne Muscular Dystrophy

From the first work by Drachman et al. that recognized a benefit from corticosteroids1 in boys with Duchenne muscular dystrophy through the excellent randomized controlled trials (RCTs)2-5 of the 1980s and 1990s, the recognition that daily corticosteroids benefit boys with Duchenne muscular dystrophy is clear. More than forty years of work with hundreds of boys have demonstrated that corticosteroids prolong walking and improve the strength of boys with Duchenne muscular dystrophy. Deflazacort, available in Canada and Europe, is not approved by the U.S. Food and Drug Administration (FDA) for use in the United States. However, there are extensive long-term positive data showing that it is effective in boys with Duchenne muscular dystrophy6,7. Although weight gain with deflazacort is less than that with daily prednisone, other side effects, including loss of height, loss of bone density, and cataracts, do occur. The study by Lebel et al. clearly adds to these data with, to our knowledge, the longest continual follow-up of a treated cohort. However, the known side effects have led to many …

Genetic Risk for Aortic Aneurysm in Adolescent Idiopathic Scoliosis

BACKGROUND Scoliosis is a feature of several genetic disorders that are also associated with aortic aneurysm, including Marfan syndrome, Loeys-Dietz syndrome, and type-IV Ehlers-Danlos syndrome. Life-threatening complications of aortic aneurysm can be decreased through early diagnosis. Genetic screening for mutations in populations at risk, such as patients with adolescent idiopathic scoliosis, may improve recognition of these disorders. METHODS The coding regions of five clinically actionable genes associated with scoliosis (COL3A1, FBN1, TGFBR1, TGFBR2, and SMAD3) and aortic aneurysm were sequenced in 343 adolescent idiopathic scoliosis cases. Gene variants that had minor allele frequencies of <0.0001 or were present in human disease mutation databases were identified. Variants were classified as pathogenic, likely pathogenic, or variants of unknown significance. RESULTS Pathogenic or likely pathogenic mutations were identified in 0.9% (three) of 343 adolescent idiopathic scoliosis cases. Two patients had pathogenic SMAD3 nonsense mutations consistent with type-III Loeys-Dietz syndrome and one patient had a pathogenic FBN1 mutation with subsequent confirmation of Marfan syndrome. Variants of unknown significance in COL3A1 and FBN1 were identified in 5.0% (seventeen) of 343 adolescent idiopathic scoliosis cases. Six FBN1 variants were previously reported in patients with Marfan syndrome, yet were considered variants of unknown significance based on the level of evidence. Variants of unknown significance occurred most frequently in FBN1 and were associated with greater curve severity, systemic features of Marfan syndrome, and joint hypermobility. CONCLUSIONS Clinically actionable pathogenic mutations in genes associated with adolescent idiopathic scoliosis and aortic aneurysm are rare in patients with adolescent idiopathic scoliosis who are not suspected of having these disorders, although variants of unknown significance are relatively common. CLINICAL RELEVANCE Routine genetic screening of all patients with adolescent idiopathic scoliosis for mutations in clinically actionable aortic aneurysm disease genes is not recommended on the basis of the high frequency of variants of unknown significance. Clinical evaluation and family history should heighten indications for genetic referral and testing.

It May Be More Than Age and Experience

This is a very interesting study of the outcomes of adolescent idiopathic scoliosis surgery that compared young surgeons with veteran surgeons. The authors chose five years of experience as the threshold. Many surgeons voice that it takes about five years to become a mature surgeon, so I presume this is why the authors chose this threshold, which seems reasonable. Candidate membership in the Scoliosis Research Society (SRS) lasts five years1. Regarding the number of cases, the two surgeon groups were unbalanced, with many more cases being performed by the veteran surgeons than by the young surgeons. This could be a problem if most of the surgical procedures in the smaller group were performed by one surgeon2. The authors did a very good job of following the patients and studying the appropriate radiographic and clinical parameters. They found several statistical differences between the two groups. The operative values that differed most significantly were duration of surgery and mean estimated blood loss. Among postoperative SRS results, scores for function differed the most. It is of interest that there was no significant difference between the two groups in terms of satisfaction. The radiographic correction was the same in both groups. The results raise a number of questions. Why was the estimated blood loss higher and …