Object The goal of this study was to determine the incidence of screw misplacement and complications in a group of 102 patients who underwent transpedicle screw fixation in the lumbosacral spine with conventional open technique and intraoperative fluoroscopy. The results are compared with published data. Methods Cases involving 102 consecutive patients (424 inserted screws) were reviewed. Surgery was performed in all cases by the same surgeon's team, using the same implant, and all results were assessed by means of a specific CT protocol. The screw position was assessed by the authors and an independent observer. Screw position was classified as correct when the screw was completely surrounded by the pedicle cortex, as “cortical encroachment” (questionable violation) if the pedicle cortex could not be visualized, and as “frank penetration” when the screw was outside the pedicular boundaries. Frank penetration was further subdivided as minor (when the edge of the screw thread was up to 2.0 mm outside the pedicle cortex), moderate (2.1–4 mm), and severe (> 4 mm). The incidence of intra- and postoperative complications not related to screw position as well as hardware failures were also registered, with a minimum follow-up duration of 8 months. Results The rate of frank pedicle screw misplacement was 5%. The rate of minimal or questionable pedicle wall violation was 2.8%. Among the frank misplacements, 6 were classified as minor, 12 as moderate, and 3 as severe penetration. Two patients (2%) had radicular pain and neurological deficits (inferomedial and inferolateral minor misplacement at L-4 and L-5, respectively), and 5 patients (4.9%) complained only of radicular pain. At the follow-up examination all patients had completely recovered their neurological function and radicular pain was resolved in all cases. The complications not related to screw malposition were 2 pedicle fractures (2% of patients), 1 nerve root injury (1%), and 1 dural laceration (1%). Five patients (4.8%) had postoperative anemia and required transfusions. Superficial or deep wound infection was noted in 3 patients (2.9%). Late hardware failure occurred in 2 patients (2%). One patient developed adjacent segmental instability and required additional surgery to extend the fusion. Conclusions Our rates of screw misplacement and complications compare favorably with the lowest rates of the series in which conventional technique was used and are close to the rates reported for image-guided methods. The risk of malpositioning may be reduced with careful preoperative surgical planning, accurate knowledge of the spinal anatomy, surgical experience, and correct indication for conventional surgery. The conventional technique still remains a practical, safe, and effective surgical method for lumbosacral fixation.

Intramedullary tumors and syringomyelia typically present with slowly progressing deficits. More rarely, they are characterized by acute presentation or worsening, at times mimicking other more common etiologies. The acute onset of syringomyelia is most likely attributable to an acute increase in cerebrospinal fluid and epidural venous pressure that results in impulsive fluid movement and, ultimately, in the rupture of the syrinx and dissection into the spinal cord or brainstem. Reported here is a case of acute presentation of a small cervical intramedullary neurinoma due to the upward dissection of its associated syrinx. Critical questions are: (1) how can a small tumor produce a large syrinx? and (2) in the absence of craniospinal interferences, which mechanism underlies the acute expansion of the cavity, resulting in a rapid onset? The authors examined the pathophysiology of syrinx formation and enlargement in intramedullary tumors and reviewed the literature, emphasizing the relationship between spinal cord movements and intramedullary pressure. On the basis of current pathogenetic concepts, the authors concluded that tumor-related syringomyelia might be caused by an association of mechanisms, both from within (obstruction of perivascular spaces; increase in extracellular fluid viscosity due to the tumor itself; intramedullary pressure gradients among different cord levels and between the cord and the subarachnoid space) and from without (the cerebrospinal fluid entering the tissue). All these factors may be amplified, as in the reported case, by a tumor located dorsally at the cervical level. Abnormal postures of the spine, such as a prolonged and excessive flexed neck position, may ultimately contribute to the acute dissection of the syrinx.

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