Letter to the Editor Concerning “Implant-Related Complications After Spinal Fusion: A Multicenter Study.” by Koshimizu et al.

To the Editor,

We recently read the study conducted by Ye et al. ¹ with considerable interest. While the research offers valuable insights into the occurrence and causes of implant-related complications, we would like to highlight some methodological considerations that may have influenced the study’s results.

One major concern is the study’s disregard for the potential influence of comorbidities and surgical variables on implant-related complications. A plethora of literature supports the notion that comorbidities and surgical variables significantly impact the incidence and nature of postoperative complications. For example, a study by John et al. ² shows that comorbidities such as diabetes and obesity significantly heighten the risk of complications and reoperation following spinal fusion surgery. Similarly, a study by Rajaee et al. ³ suggests that surgical variables like surgical duration, intraoperative blood loss, and procedure complexity considerably affect the rate of postoperative complications. The exclusion of these variables in your study might have resulted in the underestimation or overestimation of the incidence of certain implant-related complications. For instance, patients with specific comorbidities might be more susceptible to particular complications, such as screw loosening or pull out, due to impaired bone healing. Likewise, certain surgical variables might elevate the risk of specific complications. For example, longer surgical duration and higher intraoperative blood loss could increase the risk of screw malposition due to surgeon fatigue and decreased concentration.

Another concern pertains to the identification of screw malposition as the most common implant-related complication. While your study mainly attributes this to factors such as the deep surgical field, degeneration, proximity to neurovascular tissue, and vertebrae with axial rotation, it overlooks the role of surgeon experience. The literature extensively documents that surgeon experience significantly influences the rate of screw malposition. For instance, a study by Gautschi et al. ⁴ suggests that less experienced surgeons have a higher rate of malpositioned screws compared to their more experienced peers. Moreover, a systematic review by Gelalis et al. ⁵ found that the accuracy of pedicle screw placement was significantly influenced by the surgeon’s experience and the utilization of advanced intraoperative imaging techniques. Thus, the omission of surgeon experience in your study may have led to an incomplete understanding of the factors contributing to screw malposition. In addition, the study by Gautschi et al. ⁶ emphasizes the importance of the learning curve in spinal surgery, indicating that the rate of complications, including screw malposition, significantly decreases after the surgeon has performed a certain number of procedures. This factor, not considered in your study, could provide further insights into the high incidence of screw malposition observed.

In conclusion, while your study offers valuable insights, considering comorbidities, surgical variables, surgeon experience, and the type of surgical instrumentation used may provide a more comprehensive understanding of implant-related complications in spinal fusion surgery.