J Neurol Surg A Cent Eur Neurosurg 2018; 79(04): 273-278
DOI: 10.1055/s-0038-1639333
Original Article
Georg Thieme Verlag KG Stuttgart · New York

Fixation Strength of Pedicle and Cortical Lumbar Vertebral Screws after Laminectomy: A Cadaver Study

Dai-Soon Kwak
1  Department of Anatomy, Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul, Korea (the Republic of)
,
Jae-Hyuk Shin
2  Department of Orthopedic Surgery, Hallym University Dongtan Sacred Heart Hospital, Hwaseong-si, Gyeonggi-do, Korea (the Republic of)
,
Ho-Jung Cho
1  Department of Anatomy, Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul, Korea (the Republic of)
,
Ho Guen Chang
3  Department of Orthopaedic Surgery, Hallym University Sacred Heart Hospital, Anyang, Korea (the Republic of)
,
Moon Soo Park
3  Department of Orthopaedic Surgery, Hallym University Sacred Heart Hospital, Anyang, Korea (the Republic of)
,
In-Sung Kim
4  Department of Orthopedic Surgery, Hallym University Dongtan Sacred Heart Hospital, Dongtan, Korea (the Republic of)
› Author Affiliations
Funding Source This study was supported by Hallym University Medical Center institutional grant (01–2012–25).
Further Information

Publication History

31 October 2017

08 February 2018

Publication Date:
23 April 2018 (online)

Abstract

Background and Study Aim Cortical screws were proposed as an alternative to the traditional pedicle screws. Diverse experimental results support the biomechanical superiority of cortical screws compared to pedicle screws. Laminectomy is often part of multilevel lumbar surgeries. Laminectomy might weaken the medial bony edge at the entry of the divergently oriented screw and, thereby, the screw purchase. This study investigated the biomechanical strength of lumbar cortical screw after laminectomy.

Objective To compare the fixation strength of cortical screws and traditional pedicle screws after lumbar laminectomy.

Material and Methods A total of 120 pedicles from 60 lumbar vertebrae of 12 cadavers (8 men, 4 women) were assessed. The mean age of the cadavers was 73.4 ± 6.2 years (range: 62–82 years). Using a posterior midline approach, we inserted the traditional pedicle screws into one and the cortical screws into the other side of each vertebra. Laminectomy was performed after screw insertion. Vertical pullout strength and toggle strength testing were performed to compare the fixation strength between the two sides.

Results After laminectomy, the pullout strength of the cortical screws was 718.92 ± 340.76 N, and that of the pedicle screws was 625.78 ± 287.10 N (p = 0.183). The toggle strength of the cortical screws was 544.83 ± 329.97 N; that of the pedicle screws was 613.17 ± 311.70 N (p = 0.145). No significant difference was found in biomechanical strength between the two types of screws.

Conclusion Despite laminectomy, lumbar cortical screws offers comparable pullout and toggle biomechanical strength as traditional pedicle screws.