The hollow tubular implant of the invention comprises an internal cavity delimited by a peripheral wall open at its first end and having a generally circular cross-section external surface. Two side surfaces are solid and top and bottom surfaces have communicating holes in them. Annular...http://www.google.com.hk/patents/US5683463?utm_source=gb-gplus-share專利 US5683463 - Intersomatic vertebral column implant
