Study design: Cadaver study and clinical application; a pilot study.
Objective: To minimize muscle dissection and enhance accuracy of cervical pedicle screw (CPS) placement by using a percutaneous cannula system.
Summary of background data: Many studies have reported that the most frequent misplacement of CPSs is breach of the lateral wall; thus, an easy technique for securing medial convergence is required. We developed a percutaneous cannula system for this purpose and report the results of a cadaver study and its clinical application.
Methods: A cadaver study was conducted to confirm the possibility of this percutaneous technique in 5 specimens (50 CPSs, C3-C7). Then, the technique was applied in 8 patients (40 CPSs, C3-C7). The surgical technique was a hybrid of miniopen surgery and the use of percutaneous cannula system under lateral fluoroscopic guidance. Entry holes were made in the open field and a cannula was used for tapping and insertion of CPSs. A stiff pedicle probe through the cannula was used to locate the pedicle in the lateral mass.
Results: In the cadaver study, there were 12 (24%) misplacements among 50 CPSs used. The hybrid technique was applied clinically in 4 traumatic, 2 degenerative, and 2 failed back surgery lesions. Thirty CPSs were inserted using the percutaneous cannula system and 10 were inserted using a cannula as a retractor. Misplacement occurred in 6.7% (n = 2) and 20% (n = 2) pedicles, respectively, and there were no symptomatic complications (total incidence, 10%). An additional incision for the cannula system can be made for 2-level CPS insertions.
Conclusion: Use of the percutaneous cannula system facilitated a secure convergence angle for CPS insertion without extending muscle dissection or shifting cervical alignment because of muscle retraction. Moreover, this system can be used for CPS insertion in bull-necked patients.
Level of evidence: 3.