OBJECTIVE The goal of this study was to clarify the clinical utility of paravertebral foramen screws (PVFSs) and to determine intraoperative indicators for appropriate screw placement during posterior cervical fusion surgery to improve its safety.
METHODS The authors included data from 46 patients (29 men and 17 women, mean age 61.7 years) who underwent posterior cervical spine surgery with 94 PVFSs. Of the 94 PVFSs, 77 were used in C6, 9 in C3, 5 in C4, and 3 in C5. According to the cervical lateral radiographic view, the authors divided the 94 PVFSs into 3 groups as follows: a longer group, in which the tip of PVFS was located anteriorly from the line of the posterior wall of the vertebral body (> +0 mm); an intermediate group, in which the screw tip was located up to 2 mm posteriorly to the posterior wall of the vertebral body (–2 to 0 mm); and a shorter group, in which the screw tip was located more than 2 mm posteriorly (< –2 mm). The accuracy of screw placement was assessed using CT imaging in the axial plane, and the proportion of screws penetrating a vertebral foramen or a transverse foramen was compared between the 3 groups. Screw loosening was defined as a lucent zone around the screw evaluated on cervical radiography at 1 year after surgery. Complications related to PVFS insertion and revision surgery related to PVFS were evaluated.
RESULTS The authors classified 25 PVFSs into the longer group, 43 into the intermediate group, and 26 into the shorter group. The proportion of screws penetrating a vertebral foramen was largest in the shorter group, and the proportion penetrating a transverse foramen was largest in the longer group. Screw loosening was confirmed for 3 of 94 PVFSs. One PVFS inserted in C6 unilaterally within a long construct from C2 to C7 showed loosening, but it did not cause clinical symptoms. Revision surgery was required for 2 PVFSs inserted in C3 bilaterally as the lower instrumented vertebra in occiput–cervical fusion because they pulled out. There was no neurovascular complication related to PVFS insertion.
CONCLUSIONS PVFSs are useful for posterior cervical fusion surgery as alternative anchor screws, and the line of the posterior wall of the cervical body on lateral fluoroscopic images is a potential intraoperative reference to indicate an appropriate trajectory for PVFSs.
The optimal treatment for cervical facet dislocations is controversial, but the generally accepted process recommends an initial closed reduction with the next step determined according to the success of the closed reduction and the presence of traumatic disc herniation. This study aimed to show the efficacy of a posterior approach performed with an open reduction and pedicle screw fixation with removal of disc particles, if required, in the management of subaxial cervical dislocations.
Methods Between March 2012 and September 2013, 21 consecutive patients with cervical facet dislocations were enrolled. The affected levels were as follows: 4 at C3–4; 2 at C4–5; 5 at C5–6; and 10 at the C6–7 level. Seven patients had traumatic disc herniations. Closed reduction was not attempted; a prompt posterior cervical surgery was performed instead. After open reduction, pedicle screw fixation was performed. In cases with traumatic disc herniation, herniated disc fragments were excised via a posterolateral approach and successful decompressions were determined by postoperative MRI studies. Clinical outcomes were assessed using the American Spinal Injury Association (ASIA) grading system. Radiological outcomes were assessed by comparing the degree of subluxation and the angle of segmental lordosis between pre- and postoperative CT scans.
Results All patients improved neurologically. The mean segmental angles improved from 7.3° ± 8.68° to -5.9° ± 4.85°. The mean subluxation improved from 23.4% ± 16.52% to 2.6% ± 7.19%. Disc fragments were successfully removed from the 7 patients with herniated discs, as shown on MRI.
Conclusions Open reduction followed by pedicle screw fixation or posterolateral removal of herniated disc fragments is a good treatment option for cervical facet dislocations.
The aim of this study was to retrospectively evaluate the reliability and accuracy of cervical pedicle screw (CPS) placement using an intraoperative, full-rotation, 3D image (O-arm)–based navigation system and to assess the advantages and disadvantages of the system.
Methods. The study involved 21 consecutive patients undergoing posterior stabilization surgery of the cervical spine between April and December 2009. The patients, in whom 108 CPSs had been inserted, underwent screw placement based on intraoperative 3D imaging and navigation using the O-arm system. Cervical pedicle screw positions were classified into 4 grades, according to pedicle-wall perforations, by using postoperative CT.
Results. Of the 108 CPSs, 96 (88.9%) were classified as Grade 0 (no perforation), 9 (8.3%) as Grade 1 (perforations < 2 mm, CPS exposed, and < 50% of screw diameter outside the pedicle), and 3 (2.8%) as Grade 2 (perforations between ≥ 2 and < 4 mm, CPS breached the pedicle wall, and > 50% of screw diameter outside the pedicle). No screw was classified as Grade 3 (perforation > 4 mm, complete perforation). No neurovascular complications occurred because of CPS placement.
Conclusions. The O-arm offers high-resolution 2D or 3D images, facilitates accurate and safe CPS insertion with high-quality navigation, and provides other substantial benefits for cervical spinal instrumentation. Even with current optimized technology, however, CPS perforation cannot be completely prevented, with 8.3% instances of minor violations, which do not cause significant complications, and 2.8% instances of major pedicle violations, which may cause catastrophic complications. Therefore, a combination of intraoperative 3D image–based navigation with other techniques may result in more accurate CPS placement.
You must be logged in to post a comment.