Posterior arch C-1 screw technique: a cadaveric comparison study

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Posterior atlantoaxial stabilization and fusion using C-1 lateral mass screw fixation has become commonly used in the treatment of instability and for reconstructive indications since its introduction by Goel and Laheri in 1994 and modification by Harms in 2001. Placement of such lateral mass screws can be challenging because of the proximity to the spinal cord, vertebral artery, an extensive venous plexus, and the C-2 nerve root, which overlies the designated starting point on the posterior center of the lateral mass. An alternative posterior access point starting on the posterior arch of C-1 could provide a C-2 nerve root–sparing starting point for screw placement, with the potential benefit of greater directional control and simpler trajectory. The authors present a cadaveric study comparing an alternative strategy (i.e., a C-1 screw with a posterior arch starting point) to the conventional strategy (i.e., using the lower lateral mass entry site), specifically assessing the safety of screw placement to preserve the C-2 nerve root.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Five US-trained spine fellows instrumented 17 fresh human cadaveric heads using the Goel/Harms C-1 lateral mass (GHLM) technique on the left and the posterior arch lateral mass (PALM) technique on the right, under fluoroscopic guidance. After screw placement, a CT scan was obtained on each specimen to assess for radiographic screw placement accuracy. Four faculty spine surgeons, blinded to the surgeon who instrumented the cadaver, independently graded the quality of screw placement using a modified Upendra classification.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>Of the 17 specimens, the C-2 nerve root was anatomically impinged in 13 (76.5%) of the specimens. The GHLM technique was graded Type 1 or 2, which is considered “acceptable,” in 12 specimens (70.6%), and graded Type 3 or 4 (“unacceptable”) in 5 specimens (29.4%). In contrast, the PALM technique had 17 (100%) of 17 graded Type 1 or 2 (p = 0.015). There were no vertebral artery injuries found in either technique. All screw violations occurred in the medial direction.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>The PALM technique showed statistically fewer medial penetrations than the GHLM technique in this study. The reason for this is not clear, but may stem from a more angulated ”up-and-in” screw direction necessary with a lower starting point.</jats:p></jats:sec>

Retrotransverse foramen of the atlas: prevalence and bony variations

“…Our results suggest the need for special preoperative knowledge of the RTF and its bony variations in surgical treatment of atlantoaxial instability through atlas lateral mass screw insertion or Goel-Harms procedure [19]. Knowledge of the presence of an RTF and its bony variations is important for safe surgery because the ideal entry point for the insertion of a posterior arch and lateral mass screw is on the arch posterior to the lateral mass and directly above the middle of the lateral mass, respecting its convergence [3].…”

Morbidity and Mortality in Patients over 90 Years of Age Following Posterior Stabilization for Acute Traumatic Odontoid Type II Fractures: A Retrospective Study with a Mean Follow-Up of Three Years

“…Posterior cervical fusion was performed in all 15 patients using a modified Goel-Harms technique with a so-called posterior arch C1 lateral mass (PALM) screw [16][17][18]. Not only are there fewer cortical breaches, but bleeding from the epidural venous plexus and manipulation of the C2 nerve root with a potential risk of occipital neuralgia can also be avoided when using an entry point through the posterior arch of C1.…”

Letter to the Editor. Optimal entry point for C-1 lateral mass screw placement

“…Optimal entry point for C-1 lateral mass screw placement TO THE EDITOR: In a recently published cadaver study regarding the optimal entry point for C-1 lateral mass screw placement, Moisi et al 1 compared the traditional lateral mass entry point used in the Goel/Harms technique to a proposed alternative entry point in the posterior arch of the C-1 (i.e., the posterior arch lateral mass [PALM]), concluding that the latter technique is not only safe but also results in fewer medial penetrations of the spinal canal compared to the accepted Goel/Harms technique (Moisi M, Fisahn C, Tkachenko L, et al: Posterior arch C-1 screw technique: a cadaveric comparison study. J Neurosurg Spine 26:679-683, June 2017).…”