Percutaneous posterior full-endoscopic cervical foraminotomy and discectomy: a finite element analysis and radiological assessment.

Percutaneous posterior full-endoscopic cervical foraminotomy and discectomy (PECFD) is recognized as a safe, effective, and minimally invasive treatment for cervical spondylotic radiculopathy (CSR). However, the potential mechanisms of the degenerative changes and postoperative recurrence after PECFD are unclear. In this study, a finite element (FE) analysis and radiological assessment were performed to evaluate the biomechanical effects after PECFD. The FE model indicated that the ROM and IDP of C5-C6 increased significantly after PECFD in the extension loading. The radiological evaluation revealed that the extension ROM of C2-C7 and the operative level increased significantly at the one-year follow-up compared with that obtained preoperatively. Combining the FE results and radiological changes, we conclude that the increase in the ROM and IDP at the operative level in the extension loading is the potential cause of the degenerative changes and recurrences after PECFD surgery.

Adjacent segment biomechanical changes after one- or two-level anterior cervical discectomy and fusion using either a zero-profile device or cage plus plate: A finite element analysis.

Anterior cervical discectomy and fusion (ACDF) is a well-established surgical treatment for patients with symptomatic cervical degenerative disc disease, while the biomechanical changes of adjacent segments after ACDF using either a zero-profile device or cage plus plate remain uncertain. The present study is to compare adjacent segment biomechanical changes after one- or two-level ACDF using either a zero-profile device or cage plus plate. A three-dimensional finite element (FE) intact cervical model (C2-C7) was constructed and validated. In the one-level surgery model, either a zero-profile device or cage plus plate was implanted at the C5-C6 segment of the model; while in the two-level surgery model, the prostheses were implanted at the C4-C5 and C5-C6 segments of the model. A pure moment of 1.0 Nm combined with a follower load of 73.6 N were imposed on C2 to determine the flexion-extension, lateral bending, and axial rotation of different segments. The segmental range of motion (ROM) and maximum value of the intradiscal pressure of the surgery models were determined and compared with those of the intact model. In both one- and two-level ACDF models, the ROM of the fused segments was sacrificed, while loss of ROM at the fused segments was greater in cage plus plate models than in zero-profile device models because of structural differences of the implanted devices. However, the ROM and intradiscal pressure were increased at the C4-C5 and C6-C7 segments in the one-level model of ACDF using either a zero-profile device or cage plus plate, the ROM and intradiscal pressure were also increased at the C3-C4 and C6-C7 segments in the two-level surgery models. In conclusion, decreased ROM was observed at the fused segments, while increased ROM and intradiscal pressure were observed at the adjacent segments of the fused segments in ACDF, regardless of whether zero-profile devices or cage plus plate was used. Moreover, loss of ROM at the fused segments was greater in cage plus plate models than in zero-profile device models.

Biomechanical evaluation of adjacent segment degeneration after one- or two-level anterior cervical discectomy and fusion versus cervical disc arthroplasty: A finite element analysis.

BACKGROUND AND OBJECTIVE: To compare the biomechanical changes of adjacent segment degeneration (ASD) after one- or two-level anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA). METHODS: A three-dimensional finite element (FE) model of intact C2-C7 segments was constructed and validated. In the one-level surgery model, the cage with plate implant or Prestige LP cervical disc prosthesis were integrated at C5-C6 segment into the FE model; while in the two-level surgery model, the prostheses were integrated at both C4-C5 and C5-C6 segments into the FE model. A pure moment of 1.0 Nm combined with a follower load of 73.6 N were imposed on C2 to investigate the flexion-extension, lateral bending, and axial rotation of different segments in the FE model. The segmental range of motion (ROM) and intradiscal pressure of the surgery models were investigated and compared with the intact model. RESULTS: In the one-level model of ACDF, the ROM at C5-C6 was decreased, the ROM and intradiscal pressure at C4-C5 and C6-C7 segments were increased. In the two-level model of ACDF, the ROM at C4-C5 and C5-C6 were decreased, the ROM and intradiscal pressure at C3-C4 and C6-C7 were increased. However, in both one- and two-level models of CDA, the ROM of surgery segments were preserved, avoiding the increase of the ROM and intradiscal pressure at the adjacent segments. CONCLUSIONS: Abnormal ROM and intradiscal pressure at the adjacent segments may contribute to the higher risk of ASD after ACDF compared with CDA.