Regarding “Delayed presentation of aortic injury by pedicle screws: Report of two cases and review of the literature”

Abstract

We read with great interest the recent article by Kakkos and Shepard,1Kakkos S.K. Shepard A.D. Delayed presentation of aortic injury by pedicle screws: report of two cases and review of the literature.J Vasc Surg. 2008; 47: 1047-1082Google Scholar which is a timely reminder of the vascular implications of misplaced thoracic pedicle screws now widely used in spine surgery. Thoracic pedicle screws have numerous advantages over hooks, including stronger three column fixation, improved curve correction both in the coronal and axial planes, and the potential to save fusion levels. However, misplacement rates vary from a low of 1.4% reported by Suk et al2Suk S.-I. Kim W.-J. Lee S.-M. Kim J.-H. Chung E.-R. Thoracic pedicle screw fixation in spinal deformities: are they really safe?.Spine. 2001; 26: 2049-2057Crossref PubMed Scopus (428) Google Scholar to 40%.3Belmont Jr, P.J. Klemme W.R. Robinson M. Polly Jr, D.W. Accuracy of thoracic pedicle screws in patients with and without coronal plane spinal deformities.Spine. 2002; 27: 1558-1566Crossref PubMed Scopus (101) Google Scholar This large variation in misplacement rates likely results from the method utilized to determine the breach, with plain x-rays missing many breaches. Spine surgeons are most concerned with a medial breach secondary to the possibility of inflicting a neurologic injury. However, Polly et al4Polly Jr, D.W. Potter B.K. Kuklo T. Young S. Johnson C. Klemme W.R. Volumetric spinal canal intrusion: a comparison between thoracic pedicle screws and thoracic hooks.Spine. 2004; 29: 63-69Crossref PubMed Scopus (85) Google Scholar conducted a volumetric study comparing hooks, which have been placed in the spinal canal for decades, with pedicle screws. They demonstrated that a medial breach of greater than 3 mm is needed to incur a volumetric intrusion equivalent to that of a large hook. In addition, improved neuromonitoring aids the surgeon in the early detection and prevention of spinal cord injury.5Schwartz D.M. Auerbach J.D. Dormans J.P. Flynn J. Drummond D.S. Bowe J.A. et al.Neurophysiological detection of impending spinal cord injury during scoliosis surgery.J Bone Joint Surg [Am]. 2007; 89: 2440-2449Crossref PubMed Scopus (260) Google Scholar With a lateral thoracic screw breach, the surgeon must rely on intraoperative x-rays and fluoroscopy for detection. In certain scenarios, these modalities may be of limited use, particularly in large patients and in those with marked spinal deformity. Intraoperative computed tomography (CT) scanners will be of tremendous help, once the technology advances to the point of ready availability. Since 2005, we have routinely obtained a postoperative CT scan on our patients undergoing spine surgery. To date, we have obtained 233 scans and have returned two patients to the operating room for screws impinging the aorta. Since metal artifact from the pedicle screws can be significant, if we suspect a screw is in close proximity to the aorta, we proceed with an aortogram to confirm the presence of aortic contour deformity. This methodology is based on the work by Sucato et al on anterior thoracic surgery.6Sucato D.J. Kassab F. Dempsey M. Analysis of screw placement relative to the aorta and spinal canal following anterior instrumentation for thoracic idiopathic scoliosis.Spine. 2004; 29: 554-559Crossref PubMed Scopus (66) Google Scholar In addition, once the screws are placed, modern techniques such as direct vertebral body rotation to maximize spine deformity correction place the thoracic screws under considerable stress. This may contribute to an initially adequately placed screw breaching laterally. The case report by Kakkos and Shepard1Kakkos S.K. Shepard A.D. Delayed presentation of aortic injury by pedicle screws: report of two cases and review of the literature.J Vasc Surg. 2008; 47: 1047-1082Google Scholar highlights the potential morbidity of pedicle screws breaching the aorta and should aid the spine surgeon in both the intra- and postoperative care of these patients. Regarding “Delayed presentation of aortic injury by pedicle screws: Report of two cases and review of the literature”Journal of Vascular SurgeryVol. 48Issue 4PreviewWe read with great interest the letter sent to the Journal by Dr Samdani, regarding our recent publication on delayed presentation of aortic injury by pedicle screws.1 We would agree with the author that prevention is the cornerstone of treating this problem. As mentioned in the discussion or our article, several methods have been proposed and could be of great help. Intraoperative computed tomography scanning certainly has the potential to eliminate this underreported and serious complication of spinal fixation surgery. Full-Text PDF Open Archive