Pedicle or lateral mass screws in Goel-Harms construct? A biomechanical analysis

Maximilian Lenz; Philipp Egenolf; Maximilian Weber; Nadine Ott; Carolin Meyer; Peer Eysel; Max J Scheyerer

doi:10.1016/j.injury.2023.03.035

Pedicle or lateral mass screws in Goel-Harms construct? A biomechanical analysis

Injury. 2023 Mar 27:S0020-1383(23)00291-7. doi: 10.1016/j.injury.2023.03.035. Online ahead of print.

Authors

Maximilian Lenz¹, Philipp Egenolf², Maximilian Weber², Nadine Ott², Carolin Meyer³, Peer Eysel², Max J Scheyerer⁴

Affiliations

¹ University of Cologne, Faculty of Medicine, Department for Orthopaedic and Trauma Surgery, Joseph-Stelzmann Strasse 24, 50931 Cologne, Germany. Electronic address: maximilian.lenz@uk-koeln.de.
² University of Cologne, Faculty of Medicine, Department for Orthopaedic and Trauma Surgery, Joseph-Stelzmann Strasse 24, 50931 Cologne, Germany.
³ Department of Orthopaedic Surgery, Division of Spine Surgery, Helios Klinikum Bonn/Rhein-Sieg, 53123 Bonn, Germany.
⁴ University of Duesseldorf, Faculty of Medicine, Department for Orthopaedic and Trauma Surgery, Joseph-Stelzmann Strasse 24, 50931 Cologne, Germany.

PMID: 37005138
DOI: 10.1016/j.injury.2023.03.035

Abstract

Background: The use of the posterior arch of C1 as pedicle has shown beneficial stability regarding screw loosening, however, the C1 pedicle screw placement is challenging. Therefore, the study aimed to analyse the bending forces of the Harms construct used in fixation of C1/C2 when using pedicle screws compared to lateral mass screws.

Methods: Five cadaveric specimens with a mean age of 72 years at death and bone mineral density measuring for 512.4 Hounsfield Units (HU) on average were used. A custom-made biomechanical setup was used to test the specimens with a C1/C2 Harms construct each with the use of lateral mass screws and pedicle screws in sequence. Strain gauges were used to analyse the bending forces from C1 to C2 in cyclic axial compression (μm/m). All underwent cyclic biomechanical testing using 50, 75 and 100 N.

Findings: In all specimens, placement of lateral mass screws and pedicle screws was feasible. All underwent cyclic biomechanical testing. For the lateral mass screw, a bending of 142.04 µm/m at 50 N, 166.56 µm/m at 75 N and 188.54 µm/m at 100 N was measured. For the pedicle screws, bending force was slightly elevated with 165.98 µm/m at 50 N, 190.58 µm/m at 75 N and 195.95 µm/m at 100 N. However, bending forces did not vary significantly. In all measurements, no statistical significance was found when comparing pedicle screws and lateral mass screws.

Interpretation: The lateral mass screw used in the Harms Construct to stabilize C1/2 showed less bending forces, therefore the construct with lateral mass screws appears more stable in axial compression compared to the one with pedicle screws. However, bending forces did not vary significantly.

Keywords: Cervical fusion; Frailty fractures; Spinal injury; Upper cervical spine injury.