A Comparison of the Long-Term Results of Posterior Transarticular Stand-Alone Screw Instrumentation and Magerl Technique in Patients with Traumatic Atlantoaxial Instability: Mean 5-Year Follow-Up Study with Radiological and Patient-Rated Outcomes Assessments

The limitations of fully threaded screws in isolated percutaneous transarticular screw fixation of C1/C2

Demographic aging accompanied by increased falls inevitably leads to an increased incidence of atlantoaxial instabilities (AAI). Minimally invasive surgical procedures decrease the perioperative risk and regarding the treatment of AAI, percutaneous transarticular screw fixation of C1/C2 was more frequently considered in the past. This study aims to investigate the outcome of patients treated for AAI by isolated percutaneous transarticular screw fixation of C1/C2 (IPTSFC1/C2) using 3.5 mm fully threaded screws to identify its chances and limitations. In this retrospective study, data from patients who underwent IPTSFC1/C2 were analyzed. 23 patients (17 females and 6 males) with an average age of 73.1 years (y) were included. Mean VAS decreased significantly from preoperative 3.9 ± 1.8 to the last follow-up 2.6 ± 2.5 (p = 0.020) and neurological functions were preserved. In the radiological follow-up, we saw a single malposition of an inserted screw (2.27%) and one single bony fusion (4.54%). However, in 6 of 7 patients (85.71%), there was a loosening of the inserted screws due course. We demonstrated that the use of 3.5 mm fully threaded screws for IPTSFC1/C2 results in low rates of osseous fusions between C1 and C2. Therefore, their use in IPTSFC1/C2 is not suitable, especially for geriatric patients with impaired bone status.

Fluoroscopic landmarks and trajectories for safe posterior percutaneous transarticular C1-C2 screw insertion: a CT-based simulation study

PURPOSE

To determine the safe screw trajectory for posterior transarticular fixation of C1-C2 without direct visualisation of C2 lateral masses and by using fluoroscopic landmarks only.

METHODS

Fluoroscopic models of the craniovertebral region in frontal and sagittal planes were reconstructed using 1-mm interval computed tomography scans of the cervical spine in 30 patients. The imitation model of the screw trajectory was then applied with verification of the exact screw localisation using multiplanar reconstruction. Twenty-seven trajectories for 60 oblique C1-C2 reformations were tested.

RESULTS

In the frontal plane, all correct trajectories passed through the medial waistline point (WstP) of C3 and through the middle of the lateral mass of C1. In the lateral plane, the posterior spinal process-lateral mass (SpLM) point-middle C1 anterior tuberculum point (ATP), middle SpLM-upper ATP, and lower SpLM-odontoid point (ODP)-had relatively low rates of vertebral artery (VA) injury (2.3%, 4.6%, and 7%, respectively) and other screw malpositions (6.9%, 4.6%, and 4.6%, respectively). In cases of an isthmus height exceeding 8 mm, there were no incidences of VA injury. Patients with an isthmus width greater than 7 mm had a lower risk of screw malposition.

CONCLUSION

We identified potentially safe trajectories for percutaneous posterior transarticular fixation of C1-C2. Using SpLM, ATP, and ODP landmarks in the lateral plane, and WstP and C1 middle landmarks in the frontal plane, it is possible to achieve an acceptable screw position without direct visualisation of the C2 lateral mass.

Posterior percutaneous transarticular stand-alone screw instrumentation of C1-C2 with endoscopic assistance: A report of two cases

We present two cases of minimally invasive posterior transarticular screw fixation of C1-C2. The points for screw insertion were visualized by endoscopy via the instrumental port. A patient with a type III odontoid fracture with subluxation underwent a minimally invasive posterior stand-alone transarticular screw fixation. Despite the application of compression screws, for technical reasons, only minimal compression on the anterior third of the C1-C2 lateral joint was achieved. However, complete fracture fusion was achieved with stable fibrous C1-C2 fusion 2.5 years postoperatively. A second patient with a chronic type II odontoid fracture underwent percutaneous C1-C2 fixation by the same method. After 2 years, fracture fusion and C1-C2 lateral mass ankylosis were achieved. The use of a tubular retractor and endoscopy in stand-alone screw fixation of C1-C2 allows direct visualization of the screw entry point and decreases surgical trauma. This procedure might be an alternative to other methods of transarticular instrumentation.

Minimally Invasive Posterior Transarticular Stand-Alone Screw Instrumentation of C1-C2 Using a Transmuscular Approach: Description of Technique, Results and Comparison with Posterior Midline Exposure

PURPOSE

The aim of this study was to compare the feasibility, safety, and fusion results of posterior transarticular stand-alone screw (SAS) instrumentation of C1-C2 with a minimally invasive technique to those of a posterior midline exposure.

METHODS

Between 2008 and 2016, 164 patients underwent surgical treatment for traumatic injuries to the upper cervical vertebrae at our institution. We included 38 patients (27 men and 11 women; age range, 17-81 years) in the study. The posterior midline approach (PMA) group (23 patients) included patients who underwent surgery by means of a conventional midline incision after percutaneous screw insertion. The transmuscular approach (TMA) group (15 patients) included patients who underwent SAS fixation by use of a minimally invasive technique. The mean follow-up period was 58 months (range, 12-118 months).

RESULTS

Statistical analysis revealed that the operative time, blood loss volume, and severity of postoperative pain were lower in the TMA group. No significant excess of radiation exposure to the surgical team and the patients occurred in TMA group compared with the PMA group. C1-C2 fusion was observed in 37 patients. Stable fibrous fusion between the C1 and C2 vertebrae was found in 1 patient.

CONCLUSIONS

A minimally invasive technique by use of a paravertebral transmuscular approach provides an alternative to routine posterior transarticular SAS fixation of C1 and C2 through a posterior midline approach. The minimally invasive technique reduces the duration of surgery and the volume of blood loss, decreases the severity of postoperative pain, and does not increase the amount of radiation exposure for the surgical team and the patient.