Bilateral fracture of L5 pedicles in a patient with total disc replacement of L5-S1: a case report

The Role of Vertebral Porosity and Implant Loading Mode on Bone-Tissue Stress in the Human Vertebral Body Following Lumbar Total Disc Arthroplasty

STUDY DESIGN

Micro-computed tomography- (micro-CT-) based finite element analysis of cadaveric human lumbar vertebrae virtually implanted with total disc arthroplasty (TDA) implants.

OBJECTIVE

(1) Assess the relationship between vertebral porosity and maximum levels of bone-tissue stress following TDA; (2) determine whether the implant's loading mode (axial compression vs. sagittal bending) alters the relationship between vertebral porosity and bone-tissue stress.

SUMMARY OF BACKGROUND DATA

Implant subsidence may be related to the bone biomechanics in the underlying vertebral body, which are poorly understood. For example, it remains unclear how the stresses that develop in the supporting bone tissue depend on the implant's loading mode or on typical inter-individual variations in vertebral morphology.

METHODS

Data from micro-CT scans from 12 human lumbar vertebrae (8 males, 4 females; 51-89 years of age; bone volume fraction [BV/TV] = 0.060-0.145) were used to construct high-resolution finite element models (37 μm element edge length) comprising disc-vertebra-implant motion segments. Implants were loaded to 800 N of force in axial compression, flexion-, and extension-induced impingement. For comparison, the same net loads were applied via an intact disc without an implant. Linear regression was used to assess the relationship between BV/TV, loading mode, and the specimen-specific change in stress caused by implantation.

RESULTS

The increase in maximum bone-tissue stress caused by implantation depended on loading mode (P < 0.001), increasing more in bending-induced impingement than axial compression (for the same applied force). The change in maximum stress was significantly associated with BV/TV (P = 0.002): higher porosity vertebrae experienced a disproportionate increase in stress compared with lower porosity vertebrae. There was a significant interaction between loading mode and BV/TV (P = 0.002), indicating that loading mode altered the relationship between BV/TV and the change in maximum bone-tissue stress.

CONCLUSION

Typically-sized TDA implants disproportionately increase the bone-tissue stress in more porous vertebrae; this affect is accentuated when the implant impinges in sagittal bending.Level of Evidence: N/A.

Scientific Contributions of the Mexican Association of Spine Surgeons (Asociación Mexicana de Cirujanos de Columna-AMCICO) to the Global Medical Literature: A 21-Year Systematic Review

BACKGROUND

Contributions from Latin America to the global literature are scarce; until 2011, spine surgeons had published 320 articles in indexed journals.

METHODS

This systematic review evaluates the scientific production of the Mexican Association of Spine Surgeons (Asociación Mexicana de Cirujanos de Columna-AMCICO) from its inception in 1998 to 2018 with the PRISMA statement using PubMed and Google Scholar search engines. The inclusion criteria were spine-related articles in indexed journals providing any (or no) level of evidence with ≥1 AMCICO member as an author. Journal metrics, article metrics, and author variables were analyzed using SPSS version 25.

RESULTS

Of the 444 surgeons historically belonging to AMCICO, only 126 members contributed a total of 441 articles between 1998 and 2018. An average of 21.00 annual publications with an annual scientific output per capita of 0.05 was found. The most frequent evidence level was III (211 articles, 48%), the highest level was I (12 articles, 3%). The main study objective was clinical research, with 308 articles (70%), and the main study foci was trauma, with 103 articles (23%). An average impact factor of 0.16 and 0.92 was obtained for publications in Spanish and English, respectively.

CONCLUSIONS

Scientific publications by AMCICO members are scarce, with a per capita annual index of 0.05 from a total of 441 articles in indexed journals. Second, the impact factor of these journals is low, with a mean value of 0.53. Further strategies should be implemented to increase the number and track the record of Mexican contributions to the scientific literature.

Adjacent Bi-level bilateral pedicle stress fractures after instrumented posterolateral lumbar fusion-a case report and review of the literature

Isolated bilateral pedicle stress fractures of the lumbar spine are rare events, and few cases are reported in the literature. Their occurrence is commonly related to post-operative complications of spine instrumentation but can also be associated with stress-related activities, degenerative spine conditions, trauma and other miscellaneous causes. The authors report a case of adjacent bi-level bilateral pedicle fracture that developed 5 years after an instrumented posterolateral lumbar fusion. We believe that this has never been described before, and we reviewed the current literature pertaining this subject.