Placement of thoracolumbar pedicle screws using three-dimensional image guidance: experience in a large patient cohort

Accuracy of pedicle screw placement in the lumbosacral spine using conventional technique: computed tomography postoperative assessment in 102 consecutive patients

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.

On health sustenance and surgical innovation: an inquiry into linear and circular causality

Innovative surgery teeters on the horns of a dilemma. Although a surgical innovation may offer substantial improvement over conventional treatment strategies on one hand, it may on the other be perceived as involving significant risk by both the surgeon and the patient. Based on primary data collected from field research in the operating rooms of a local hospital and from in-depth interviews with a consultant surgeon of orthopedics and traumatology, this article looks into 2 real-life spine surgery cases: an exploration of the possibilities for cervical spine fusion surgery and the creative use of a computerized surgical navigation tool. The discussion centers on how a surgeon thinks and acts when presented with such scenarios. It is argued that surgical innovation as well as the responses to it develop through a process of "nested" circular causalities that arise from a linearly directed intention-that is, the intention to cure illness. In relation to how a surgeon thinks, it is argued that if the causes for intervention were different-that is, the surgeon's desire to cure an illness and, at the same time, allow the patient to live a better and happier life-then the effect would be the decision to carry out an alternate procedure, thus, presenting a new choice. In relation to how a surgeon acts, it is argued that rigid, unquestioning adherence to prevailing assumptions and practices can serve to stifle originality. Surprise and novelty emerge only when the surgeon challenges existing assumptions as well as the validity of their constituent elements.

Pedicle morphometry for thoracic screw fixation in ethnic koreans : radiological assessment using computed tomographic myelography

OBJECTIVE

In the thoracic spine, insertion of a pedicle screw is annoying due to small pedicle size and wide morphological variation between different levels of the spine and between individuals. The aim of our study was to analyze radiologic parameters of the pedicle morphometry from T1 to T8 using computed tomographic myelography (CTM) in Korean population.

METHODS

For evaluation of the thoracic pedicle morphometry, the authors prospectively analyzed a consecutive series of 26 patients with stable thoracic spines. With the consent of patients, thoracic CTM were performed, from T1 to T8. We calculated the transverse outer diameters and the transverse angles of the pedicle, distance from the cord to the inner cortical wall of the pedicle, and distance from the cord to the dura.

RESULTS

Transverse outer pedicle diameter was widest at T1 (7.66 +/- 2.14 mm) and narrowest at T4 (4.38 +/- 1.55 mm). Transverse pedicle angle was widest at T1 (30.2 +/- 12.0 degrees ) and it became less than 9.0 degrees below T6 level. Theoretical safety zone of the medial perforation of the pedicle screw, namely, distance from the cord to inner cortical wall of the pedicle was more than 4.5 mm.

CONCLUSION

Based on this study, we suggest that the current pedicle screw system is not always suitable for Korean patients. Computed tomography is required before performing a transpedicular screw fixation at the thoracic levels.

Image-guided pedicle screw insertion accuracy: a meta-analysis

Improved pedicle screw insertion accuracy has been reported with the assistance of computer tomography-based navigation. Studies also indicated that fluoroscopy-based navigation offers high accuracy and is comparable to CT-based assistance. However, different population characteristics and assessment methods resulted in inconsistent conclusions. We searched OVID, Springer, and MEDLINE databases to conduct a meta-analysis of the published literature specifically looking at accuracy of pedicle screw placement with different navigation methods. Subgroups and descriptive statistics were determined based on the subject type (in vivo or cadaveric), navigational method, and spinal level. A total number of 7,533 pedicle screws were summarised in our database with 6,721 screws accurately inserted into the pedicles (89.22%). Overall, the median placement accuracy for the in vivo CT-based navigation subgroup (90.76%) was higher than that with the use of two-dimensional (2D) fluoroscopy-based navigation (85.48%). We concluded that CT-based navigation could provide a higher accuracy in the placement of pedicle screws for all subgroups presented. In the lumbar level, 2D fluoroscopy-based navigation was comparable with CT-based navigation. Discrepancy between the two navigation types increased in the thoracic level for the in vivo populations, where there was less potential in the use of 2D fluoroscopy-based navigation than CT-based navigation.