A threaded center line cage assembly includes a cylindrical intervertebral spacer member to which is attached a winged end cap. The spacer member is implanted along a center line or median plane between a pair of adjacent vertebrae to engage inner regions of mutually facing surfaces of the vertebrae....http://www.google.com.tw/patents/US7235105?utm_source=gb-gplus-share專利 US7235105 - Threaded center line cage with winged end gap
