Tomographic Assessment of Fusion Rate, Implant-Endplate Contact Area, Subsidence, and Alignment With Lumbar Personalized Interbody Implants at 1-Year Follow-Up

Christopher P. Ames; Justin S. Smith; Rodrigo J. Nicolau

doi:10.14444/8640

Abstract

Background Incongruity between irregularly shaped vertebral endplates and the uniform surfaces of stock interbody fusion cages has been identified as contributing to cage subsidence, pseudarthrosis, and unpredictable alignment. Advances in manufacturing techniques have driven the development of personalized interbody cages (PICs) that can match individual endplate morphology and provide the exact shape and size needed to fill the disc space and achieve the planned correction. This study used computed tomography (CT) imaging to evaluate the implant-endplate contact area, fusion, subsidence, and achievement of planned alignment correction in patients receiving PIC devices.

Methods This retrospective study included patients treated for adult spinal deformity at a single site and implanted with PIC devices at L4 to L5 or L5 to S1 for segmental stabilization and alignment correction, who received 1-year postoperative CT images as part of their standard of care. An evaluation using 3-dimensional thin-section scans was conducted. Implant-endplate contact and signs of fusion were assessed in each CT slice across both endplates. The degree of subsidence as well as measures of segmental and global lumbar alignment were also assessed.

Results Fifteen patients were included in the study, with a mean age of 68.2 years. Follow-up ranged between 9 and 14 months. Twenty-six total lumbar levels were implanted; 20 with PIC devices via the anterior lumbar interbody fusion approach, 2 with stock cages via the anterior lumbar interbody fusion approach, and 4 with PIC devices via the transforaminal lumbar interbody fusion approach. CT analysis of PIC-implanted levels found an overall implant-endplate contact area ratio of 93.9%, a subsidence rate of 4.5%, a fusion rate of 100%, and satisfactory segmental and global lumbar correction compared with the preoperative plan.

Conclusions PIC implants can provide nearly complete contact with endplate surfaces regardless of the individual endplate morphology. Subsidence, fusion, and alignment assessments in this tomographic study illustrated results consistent with the benefits of a personalized interbody implant.

Level of Evidence 4.

Footnotes

Funding This work was supported by funding from Carlsmed.
Declaration of Conflicting Interests Christopher P. Ames discloses that he is a clinical research investigator and receives consulting fees from Carlsmed. Justin S. Smith discloses that he is a shareholder and receives consulting fees from Carlsmed. Rodrigo J. Nicolau discloses that he is an employee of Carlsmed and receives or has received consulting fees, honoraria, support for attending meetings/travel, and stock/stock options from Carlsmed.
Disclosures In addition to relationships listed in the Conflicts of Interest, Christopher P. Ames discloses that he has received grants or contracts from SRS; receives royalties or licenses from DePuy Synthes, K2M, Next Orthosurgical, Stryker, Biomet Zimmer Spine, Medicrea, and Nuvasive; receives consulting fees from DePuy Synthes, Medicrea, Agada Medical, Medtronic, and K2M; is the chair of the SRS Safety and Value Committee and serves on the ISSG Executive Committee; and has other financial/nonfinancial interests in Operative Neurosurgery and Neurospine (editorial boards), Global Spinal Analytics (director), and Titan Spine, ISSG, and DePuy Synthes (research). Justin Smith reports grants/contracts from SeaSpine Orthofix, NREF, AOSpine, and DePuy Synthes; royalties/licenses from Highridge and Globus/NuVasive; consulting fees from Highridge, SeaSpine Orthofix, Medtronic, Cerapedics, and Globus/NuVasive; support for attending meetings/travel from AOSpine; serves on the SRS Board of Directors and ISSGF Executive Committee; and stock/stock options from Alphatec, Globus/NuVasive, and Carlsmed. Rodrigo J. Nicolau reports to be an employee of Carlsmed.
IRB Approval This study utilized secondary research consisting of de-identified data for which consent is not required and was therefore exempt from institutional review board review under 45 CFR §46.104 (d)(4)(ii). No direct patient involvement occurred.

This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2024 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.

View Full Text