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Background <p>Percutaneous transforaminal endoscopic decompression (PTED) has been considered an effective surgical option for lumbar spinal stenosis (LSS). In elderly patients with LSS, the pathological basis of the lumbar spine commonly involves severe disc degeneration combined with osteoporosis. This study aimed to characterize body mass index (BMI)-related biomechanical patterns in severe degeneration–osteoporosis–PTED models of elderly LSS, focusing on postoperative segmental kinematics and load redistribution under different BMI-related axial loading conditions.</p> Methods <p>Lumbar computed tomography data from a healthy 30-year-old volunteer were used to construct an intact L3–S1 finite element (FE) model (M0) in ANSYS APDL 13.0. Based on M0, a PTED model at L4–L5 was developed under severe disc degeneration and osteoporosis. Five BMI levels were simulated: 18.5&#xa0;kg/m² (M1), 24.0&#xa0;kg/m² (M2), 28.0&#xa0;kg/m² (M3), 32.0&#xa0;kg/m² (M4), and 36.0&#xa0;kg/m² (M5). The biomechanical outcomes included range of motion (ROM), intradiscal pressure (IDP), and facet joint stress (FJS).</p> Results <p>Compared with M0, all BMI models under the high-risk background (M1–M5) showed reduced ROM in all motion directions (approximately − 27.3% to − 27.9% in M1). ROM increased mildly with higher BMI; however, even at the highest BMI, ROM remained below M0 (approximately − 20.5% to − 22.5%). IDP suggested a possible BMI-related transition pattern under the present modeling assumptions: IDP was lower than M0 at lower BMI (M1–M2; approximately − 8.9% to − 13.8%), approached M0 at M3 (approximately − 1.0% to − 1.9%), and exceeded M0 at higher BMI (M4, approximately + 3.7% to + 5.1%; M5, approximately + 8.8% to + 11.2%). FJS increased monotonically with BMI in all motion directions (M1, approximately + 5.6% to + 8.0%; M5, approximately + 20.4% to + 31.5%), and the highest absolute FJS occurred during extension.</p> Conclusion <p>In severe degeneration–osteoporosis–PTED models of elderly LSS, increasing BMI was associated with an overall pattern of “restricted motion with upward load shift” compared with the healthy intact reference model. Although ROM remained lower than that in M0, higher BMI shifted postoperative load sharing toward increased IDP and persistently elevated FJS. These findings may provide biomechanical evidence to inform postoperative load management in elderly patients with LSS with compromised structural reserve and higher BMI.</p>

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Biomechanical patterns associated with body mass index in percutaneous transforaminal endoscopic decompression models of elderly lumbar spinal stenosis with severe disc degeneration and osteoporosis: a finite element study

  • 期刊论文

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  • 发表日期：

    2026年7月14日

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  • Wei Liu,
  • Tusheng Li,
  • Jingbo Ma,
  • Aobo Wang,
  • Ziqian Ma,
  • Peng Du,
  • Lei Zang

摘要

Background

Percutaneous transforaminal endoscopic decompression (PTED) has been considered an effective surgical option for lumbar spinal stenosis (LSS). In elderly patients with LSS, the pathological basis of the lumbar spine commonly involves severe disc degeneration combined with osteoporosis. This study aimed to characterize body mass index (BMI)-related biomechanical patterns in severe degeneration–osteoporosis–PTED models of elderly LSS, focusing on postoperative segmental kinematics and load redistribution under different BMI-related axial loading conditions.

Methods

Lumbar computed tomography data from a healthy 30-year-old volunteer were used to construct an intact L3–S1 finite element (FE) model (M0) in ANSYS APDL 13.0. Based on M0, a PTED model at L4–L5 was developed under severe disc degeneration and osteoporosis. Five BMI levels were simulated: 18.5 kg/m² (M1), 24.0 kg/m² (M2), 28.0 kg/m² (M3), 32.0 kg/m² (M4), and 36.0 kg/m² (M5). The biomechanical outcomes included range of motion (ROM), intradiscal pressure (IDP), and facet joint stress (FJS).

Results

Compared with M0, all BMI models under the high-risk background (M1–M5) showed reduced ROM in all motion directions (approximately − 27.3% to − 27.9% in M1). ROM increased mildly with higher BMI; however, even at the highest BMI, ROM remained below M0 (approximately − 20.5% to − 22.5%). IDP suggested a possible BMI-related transition pattern under the present modeling assumptions: IDP was lower than M0 at lower BMI (M1–M2; approximately − 8.9% to − 13.8%), approached M0 at M3 (approximately − 1.0% to − 1.9%), and exceeded M0 at higher BMI (M4, approximately + 3.7% to + 5.1%; M5, approximately + 8.8% to + 11.2%). FJS increased monotonically with BMI in all motion directions (M1, approximately + 5.6% to + 8.0%; M5, approximately + 20.4% to + 31.5%), and the highest absolute FJS occurred during extension.

Conclusion

In severe degeneration–osteoporosis–PTED models of elderly LSS, increasing BMI was associated with an overall pattern of “restricted motion with upward load shift” compared with the healthy intact reference model. Although ROM remained lower than that in M0, higher BMI shifted postoperative load sharing toward increased IDP and persistently elevated FJS. These findings may provide biomechanical evidence to inform postoperative load management in elderly patients with LSS with compromised structural reserve and higher BMI.