Tiny but risky: The reasons why the Caspar pin distractor causes suffocating cervical hematoma-Two cases and a literature review

Symptomatic cervical hematoma (CH) after cervical spine surgery through an anterolateral approach is a feared complication. In up to 60% of CH cases, no source of bleeding is detected during drainage. Bleeding from the pin holes of the Caspar distractor is a known complication, briefly mentioned in the patent, but harmfulness has never been thoroughly assessed. Our team experienced two consecutive postoperative acute CHs, in which the origin of active bleeding obviously came from pin holes, despite careful obturation. The aim of this study was to report these two cases and provide a comprehensive assessment of the dangers of Caspar pin distractors. The intrabody vascularization was well organized and there was a central pedicle arising from the center of the posterior wall. The pedicle penetrated deeply into the body and constituted Batson's channel posteriorly. Retrospectively, it was well-identified in both cases on preoperative imaging. Given the morphological features of the vertebral cervical bodies and Caspar pin, the pin may reach the center of the posterior wall where the pedicle arises. Comparison between vertebral body volumes and the volume of the screwable part of the pins revealed that the pin could occupy up to 7.3% of the total body if randomly inserted. However, pins are in fact inserted into a particular place that contains the pedicle. Epidural bleeding is variable and may be undetected before closure. This also depends on blood pressure variations and changes in the patient's position. Even though Caspar pins are tiny, the likelihood of intrabody vascularization damage appears to be significant. Caspar pins should not be used systematically. Pin hole obturation must be solid and deep. Alternative options such as an interbody distractor and a microscope for the discectomy should be considered.