Chinese Journal of Tissue Engineering Research ›› 2025, Vol. 29 ›› Issue (27): 5765-5772.doi: 10.12307/2025.830

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Biomechanical performance of novel fully cortical bone threaded screws in modified cortical bone trajectory screw technique for lumbar vertebrae

Muzaipaer · Maitusong1, Xiao Yang2, Gulimire · Adili3, Zhigeer · Lehalebieke1, Aizihaier · Aisikaer1, Wang Yixi2, Chen Ruilin1, #br# Paerhati · Rexiti2, 4, 5   

  1. 1First Clinical Medical College, Xinjiang Medical University, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; 2Department of Minimally Invasive and Precision Orthopedics, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; 3Fourth Clinical Medical College, Xinjiang Medical University, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; 4Key Laboratory of High Incidence Diseases Research in Xinjiang (Xinjiang Medical University), Ministry of Education, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; 5Xinjiang Orthopedic Clinical Research Center, Urumqi 830000, Xinjiang Uygur Autonomous Region, China
  • Received:2024-04-07 Accepted:2024-07-10 Online:2025-09-28 Published:2025-03-04
  • Contact: Paerhati · Rexiti, Chief physician, Professor, Doctoral and Master’s supervisor, Department of Minimally Invasive and Precision Orthopedics, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; Key Laboratory of High Incidence Diseases Research in Xinjiang (Xinjiang Medical University), Ministry of Education, Urumqi 830000, Xinjiang Uygur Autonomous Region, China; Xinjiang Orthopedic Clinical Research Center, Urumqi 830000, Xinjiang Uygur Autonomous Region, China
  • About author:Muzaipaer · Maitusong, First Clinical Medical College, Xinjiang Medical University, Urumqi 830000, Xinjiang Uygur Autonomous Region, China
  • Supported by:
    Outstanding Youth Science Fund Project of Xinjiang Uygur Autonomous Region, No. 2021D01E29 (to PR); Undergraduate Innovation Training Program Project of Xinjiang Medical University, No. 202210760027 (to MM)

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Abstract: BACKGROUND: Osteoporotic trabecular structures are insufficient to maintain screw holding force, often leading to spinal fixation failure. Currently, the following four aspects are mainly used to solve this problem: (1) screw material; (2) surface coating treatment; (3) screw channel solidification strategy; (4) screw shape. The screw channel of the modified cortical bone trajectory screw placement technique has been proven to have a good fixation effect, but there is an urgent need to develop matching screws. 
OBJECTIVE: To compare the biomechanical performance differences of various types of spinal cortical bone thread screws in the modified cortical bone trajectory fixation of lumbar vertebrae using the finite element method.
METHODS: The L4 vertebral models were constructed based on the CT data of three adult wet lumbar specimens (two males and one female) and subjected to finite element analysis. In the modified cortical bone trajectory fixation technique, fully cortical bone thread screws (single thread screws) with lengths of 45 mm and diameters of 5.5 mm and 4.5 mm were used and considered as groups A and B, which were compared with those of the traditional pedicle screw technique group (group C, 6.0 mm diameter, 45 mm length, double-threaded screw) and the cortical bone trajectory screw group (group D, 4.5 mm diameter, 45 mm length, double-threaded screw). Axial pull-out force, screw stability (determined by the displacement ratio of upper, lower, left, and right loads), and anti-spin-out torque were measured to compare fixation strength of each group of screws.
RESULTS AND CONCLUSION: (1) Axial pull-out force: Group A > group B (P=0.003), and both group A and group B were greater than the group C (P < 0.001, P=0.003) and group D (all P < 0.001). (2) Screw stability: When load was applied in the upward and downward directions on the screw, the load displacement ratio of the four screw double threads was greater in group A than in group B (P > 0.05); both group A and group B were greater than the group C (all P < 0.001) and the group D (all P < 0.001). (3) Anti-spin-out torque: Group A > group B (P=0.008), and both group A and group B were greater than the group C (P=0.008, P=0.131). (4) It is indicated that during modified cortical bone trajectory fixation of lumbar vertebrae, the novel spinal cortical bone thread screw demonstrates superior biomechanical performance compared to double thread screws applied in the clinically classic pedicle screw trajectory and cortical bone trajectory. Additionally, the novel spinal cortical bone thread screw (D=5.5 mm, L=45 mm) becomes the optimal adaptation for the modified cortical bone trajectory screw path.

Key words: fully cortical bone screw, modified cortical bone trajectory, lumbar vertebrae, axial pull-out force, screw stability, anti-spin-out torque, finite element analysis, biomechanics 

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