Subaxial cervical pedicle screw fixation through paraspinal approach: anatomic and clinical studies

Objective To investigate the feasibility and clinical application of the cervical pedicle screw fixation through intermuscular planes between musculus semispinalis cervicis and musculus semispinalis capitis. Methods Five adult specimens were selected for studying the anatomic features of musculus semispinalis cervicis and musculus semispinalis capitis and the distributions of surrounding deep cervical vassels and carotid nerve. Fifty cervical pedicle screws were placed into C3-C7 for all specimens. Besides, cervical transpedicular fixation with 49 screws was performed in 12 patients via the intermuscular planes between musculus semispinalis cervicis and musculus semispinalis capitis. Wounds and complications were detected after operation. Screw position was assessed by CT imaging. Results Musculus semispinalis capitis was the main part of the lateral intermuscular septum. Musculus semispinalis cervicis was the main part of the medial intermuscular septum. Multifidus and rotator participated in forming the cervical dorsal rami nerve bone fiber tube. Medial and lateral intermuscular tissues were dominated respectively by cervical dorsal medial branch and lateral branch. Deep cervical artery lied in upward branches between the semispinalis capitis and semispinalis cervicis, supplying both sides of the semispinalis. Six screws placed in the specimens cut through the pedicle wall. Screws were placed successfully in all the 12 patients. The plane between musculus semispinalis capitis and semispinalis cervicis could be separated easily. Four screws broke the pedicle wall, but there were no screw-related complications. Conclusions A new intermuscular plane through musculus semispinalis cervicis and musculus semispinalis capitis is developed to facilitate the low cervical pedicle screw insertion. Primary clinical results show cervical pedicle screw placement through the new approach is safe, feasible, easy and minimally invasive. Key words: Cervical vertebrae; Anatomy; Pedicle screws