How Many Screws Are Necessary to Be Considered an Experienced Surgeon for Freehand Placement of Thoracolumbar Pedicle Screws?: Analysis Using the Cumulative Summation Test for Learning Curve.

OBJECTIVE

To determine the amount of screws needed to achieve an adequate skill level for pedicle screw placement (PSP) via the freehand technique in the nondeformed thoracolumbar spine using the cumulative summation test for learning curve (LC-CUSUM) analysis.

METHODS

This study includes the first 85 patients who underwent pedicle screw installation in the thoracic and lumbar spine by a single orthopedic surgeon. The surgeon had 1 years' experience of fellowship training in a tertiary teaching hospital. The learning curve of freehand PSP was investigated using the LC-CUSUM analysis. Procedure success was defined as acceptable accuracy of PSP, which was divided into group 1 (the screw breaches the pedicle's cortex by less than 2 mm) and group 2 (the screw is completely within the pedicle).

RESULTS

A total of 52 cases and 313 pedicle screws were included and analyzed in this study. The LC-CUSUM analysis signaled competency for freehand PSP at the 115th pedicle screw (17th case) in group 1 and at the 312th pedicle screw (52nd case) in group 2. This means that a trainee with no experience with freehand PSP reached an adequate accuracy level of PSP with less than 2 mm pedicle breaches at the 115th screw and completely within the pedicle at the 312th screw. There were no major complications, such as neurovascular injury, and life-threatening complications.

CONCLUSIONS

In this study, the learning curve analysis demonstrated that a substantial learning period may be necessary before an adequate level of performance is achieved for freehand PSP in the nondeformed thoracolumbar spine.