Histology of Tissues Within Retrieved Human Titanium Mesh Cages

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Abstract
Histologic documentation of contents within retrieved, failed human titanium mesh cages. The purpose of this study is to describe the contents of a series of retrieved, clinically failed titanium mesh cages from human patients. The use of interbody fusion cages is gaining rapid acceptance, but there is little histologic documentation of tissue within retrieved cages. Eleven Titanium Surgical Mesh Cages (Harms; DePuy AcroMed, Raynham, MA) retrieved from 10 patients were histologically analyzed. Indications for cage retrieval included failed fusion or failed fusion with instrumentation failure. The cages had been in situ from 2 to 47 months. Histologic sections were reviewed qualitatively, and the approximate percent of area in the cage occupied by viable bone, necrotic bone, fibrocartilage, hyaline cartilage, fibrous tissue, and bone graft substitute was visually estimated. Particles of metal debris were estimated by a semiquantitative scoring system. All cages except one showed evidence of vascular ingrowth and areas of histologically viable bone, representing incorporating bone graft. At least a few particles of debris were present in 9 of 11 cages. Fibrocartilage of probable intervertebral disc origin ranged from 0% to 70% of the available area. Several cages contained small seams of fibrocartilage connecting segments of bone in a pattern that suggested a response to motion. Mean viable bone area within 11 retrieved, human titanium mesh cages was approximately 31%. Seams of fibrocartilage within the cages may represent tissue differentiation in response to bending or compressive load.