Cage plus plate (CP) and zero-profile (Zero-P) devices are widely used in anterior cervical discectomy
and fusion (ACDF). This study aimed to compare adjacent segment biomechanical changes after ACDF when
using Zero-P device and CP in different segments. First, complete C1—C7 cervical segments were constructed
and validated. Meanwhile, four surgery models were developed by implanting the Zero-P device or CP into C4—C5
or C5—C6 segments based on the intact model. The segmental range of motion (ROM) and maximum value of the
intradiscal pressure of the surgery models were compared with those of the intact model. The implantation of CP
and Zero-P devices in C4—C5 segments decreased ROM by about 91.6% and 84.3%, respectively, and increased
adjacent segment ROM by about 8.3% and 6.82%, respectively. The implantation of CP and Zero-P devices in
C5—C6 segments decreased ROM by about 93.3% and 89.9%, respectively, while increasing adjacent segment
ROM by about 4.9% and 4%, respectively. Furthermore, the implantation of CP and Zero-P devices increased
the intradiscal pressure in the adjacent segments of C4—C5 segments by about 4.5% and 6.7%, respectively. The
implantation of CP and Zero-P devices significantly increased the intradiscal pressure in the adjacent segments of
C5—C6 by about 54.1% and 15.4%, respectively. In conclusion, CP and Zero-P fusion systems can significantly
reduce the ROM of the fusion implant segment in ACDF while increasing the ROM and intradiscal pressure of
adjacent segments. Results showed that Zero-P fusion system is the best choice for C5—C6 segmental ACDF.
However, further studies are needed to select the most suitable cervical fusion system for C4—C5 segmental
ACDF. Therefore, this study provides biomechanical recommendations for clinical surgery.
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