Feasibility of laminar screw placement in the upper thoracic spine: analysis using 3-dimensional computed tomographic simulation

Feasibility of lateral mass screw insertion in patients with the risky triad of C1: evaluation of the over-the-arch technique

OBJECTIVE

The objective of this study was to evaluate the feasibility and complications of the over-the-arch (OTA) technique for screw insertion into the C1 lateral mass in patients in whom conventional techniques (i.e., posterior arch [PA] and inferior lateral mass [ILM]) are not feasible due to 1) PA with a very small height (< 3.5 mm), 2) a caudally tilted PA blocking the inferior part of the C1 lateral mass, or 3) loss of height at the ILM (< 3.5 mm).

METHODS

The authors reviewed the medical records of 60 patients who underwent C1 screw fixation with the OTA technique (13 screws) and the PA/ILM technique (107 screws) between 2011 and 2019. Vertebral artery (VA) injuries, screw malposition, and bony union were radiologically assessed. Clinical outcome measures, including Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) scale score, and occipital neuralgia, were recorded.

RESULTS

Thirteen OTA screws were successfully inserted without any major complications. NDI and JOA scale scores did not show significant differences between the two groups at final follow-up. No VA injuries were recognized during screw insertion. There was no evidence of ischemic damage to the VA or bony erosion in the occiput or atlas. Medial wall violation was observed in 1 screw (7.7%); however, no C0-1, C1-2, or lateral wall violations were observed. No patients developed new-onset neuralgia postoperatively after C1 fixation with the OTA technique.

CONCLUSIONS

The OTA technique was safe and useful for C1 screw fixation in patients in whom conventional techniques could not be employed.

Transposterior Arch Lateral Mass Screw for C1 Fixation: Application of a 3.5-mm-Diameter Screw in the Vertebral Artery Groove with a Height of ≤3.5 mm

OBJECTIVE

To explore the feasibility and effectiveness of C1 lateral mass fixation via the posterior arch using pedicle screws of 3.5-mm diameter in patients whose atlas in the vertebral artery groove (C1 pedicle) was ≤3.5 mm in height.

METHODS

A total of 14 patients who underwent transposterior arch lateral mass screw fixation between 2014 and 2017 due to atlantoaxial instability were retrospectively studied. The height of the atlas pedicle was ≤3.5 mm on one or both sides. The position of the screw and damage of the screw trajectory were assessed using the postoperative 3-dimensional computed tomography. The patients were regularly followed up to observe the fracture union and bone graft fusion.

RESULTS

In total, 27 atlas pedicle heights were ≤3.5 mm and 22 screws were successfully inserted without any neurovascular complications. However, the pedicle wall was found to have a certain degree of damage with damaged superior/inferior wall in 4 of 6 pedicles respectively. Clinical symptoms were relieved to varying degrees, and patients demonstrated bony fusion during the postoperative follow-up.

CONCLUSIONS

Pedicle screws of 3.5-mm diameter could be fixed with a high success rate using the viscoelasticity and expansivity of the bone tissue even if the atlas pedicles were ≤3.5 mm in height. Although the screws had a certain probability of breaking the superior/inferior wall, they provided sufficient stability and enabled fracture or bone graft healing. Extraverted atlas pedicle screws should be considered in some cases.

A radiological and anatomic examination of intralaminar screws in the thoracic spine-a theoretical feasibility study

BACKGROUND

Failure of pedicle screws and anatomical variations which prevent pedicle screw implantation make the search for an alternative to pedicle screws in thoracic spine surgery necessary. To date, published data have shown that intralaminar screws could be a possible way of fixation. Object of this study is a systematic examination of the feasibility of lamina screws in the whole thoracic spine.

METHODS

Fifty females and 50 males (age 20 to 60 years) who underwent a polytrauma CT from 2010 to 2012 were randomly selected. Patients with injury of the thoracic spine, trauma-independent deformity, or dysplasia of the thoracic spine were excluded. A three-dimensional reconstruction of the thoracic spine was performed from the data set. The anatomical data of the lamina were measured under consideration of the potential trajectory of a laminar screw. The caliber of the corresponding pedicle was measured as well.

RESULTS

The diameters of the lamina show a decline in superior-inferior direction (0.66 cm in T1 to 0.60 cm in T12 in males, 0.62 to 0.56 cm in females). Diameters of pedicle and lamina show no correlation. Twenty percent of the pedicles have a hypoplasia with a diameter of less than 0.5 cm. However, in these vertebrae, 62.3% of the laminae would be suitable for 0.4-cm lamina screws. Only in 2.75% of the vertebral bodies, there was no possibility for intralaminar or pedicle screws.

CONCLUSIONS

This study shows that it is possible to use intralaminar screws in the thoracic spine in most of patients.

Feasibility Study of Free-Hand Technique for Pedicle Screw Insertion at C7 without Fluoroscopy-Guidance

Study Design

Retrospective interventional study.

Purpose

To introduce a free-hand pedicle screw (PS) insertion technique without fluoroscopic guidance in the C7 vertebra and evaluate the procedure's feasibility and radiologic outcomes.

Overview of Literature

Although PS insertion at C7 has been recognized as a critical procedure in posterior cervical fusion surgery, conventional techniques for C7 PS have several limitations.

Methods

Thirty two patients (64 screws) who underwent PS insertion in C7 with the novel technique were included in this study. Postoperative clinical and radiological outcomes were evaluated. Special attention was paid to the presence of any problems in the screw position including cortical breaches of the PS and encroachment of the PS into the spinal canal or the vertebral foramen. This novel technique for PS insertion in C7 without fluoroscopy guidance had three key elements. First, the ideal PS entry point was chosen near the C6–7 facet joint using preoperative images. Second, the convergent angle distance was measured at axial computed tomography (CT) imaging, which defined the distance between the tip of C7 spinous process and the extended line passing through the pedicle axis from the ideal entry point. Third, the cranial-caudal angle distance was measured in sagittal CT images, which defined the distance between the tip of the C7 spinous process and the extended line passing through the pedicle axis.

Results

Cortical breach on postoperative CT images was observed in three screws. All violated only the lateral wall of the affected pedicle. The breached screws occurred in the initial five cases. Postoperative neurologic deterioration was not observed in any patient, regardless of cortical breaching.

Conclusions

The novel technique successfully allows for C7 PS to be placed and is associated with a low rate of cortical breach.

Bone fusion rate in the thoracic and lumbar spine after laminoplasty with laminar screws

STUDY DESIGN

Retrospective clinical study.

OBJECTIVE

The purpose of this study was to determine the bone fusion rate after laminoplasty with laminar screws.

SUMMARY OF BACKGROUND DATA

There are many procedures, mostly with miniplates and screws, to repair an opened lamina after surgery for intraspinal pathology. Laminoplasty with laminar screws is an alternative procedure; however, the surgical outcome of this procedure has not been reported before.

METHODS

Laminoplasty with laminar screws was performed in 40 consecutive patients (male to female ratio=18:22; age, 47.4±13.6 yr) after surgery for intradural pathology. The lamina flap, which was opened with a high-speed drill or Kerrison punch, was reattached to the host bone with bilateral laminar screws. The bony fusion was assessed with computed tomographic scans that were taken 14.1±6.4 months postoperatively. If the gap between the host bone and the grafted lamina was filled up with a bony bridge, it was regarded as "fused." The fusion rate was assessed in terms of the hemilamina, the operated level, and the patient. The operated level was considered fused when at least 1 side of the hemilamina was completely fused to the host bone. Fusion success for a patient was defined as "all operated levels were fused." The follow-up period was 40.7±13.8 months.

RESULTS

Screw fixation was successfully achieved in 97.7% (150/154 hemilaminae, 77 levels) of the hemilaminae. Solid bony fusion was achieved in 56.7% (85/150) of the hemilaminae, 75.3% (58/77) of the operated levels, and 67.5% (27/40) of the patients. Screw breakage or displacement of the grafted laminae was not observed during the follow-up period.

CONCLUSION

Laminoplasty with laminar screws had a 67.5% fusion rate, and migration of the grafted laminae was not observed in any of the patients probably due to additional fibrous unions.

LEVEL OF EVIDENCE

4.