A spinal fusion implant comprising: a leading end , an opposite trailing end , an upper portion extending between the leading and trailing ends , and a lower portion extending between the leading and trailing ends , the upper portion including a first portion positioned adjacent the leading end , a second portion positioned adjacent the trailing end , and at least two rails extending between the first and second portions of the upper portion , the lower portion including a first portion positioned adjacent the leading end , a second portion positioned adjacent the trailing end , and at least two rails extending between the first and second portions of the lower portion , the at least two rails of the upper portion including a first rail including a bone-contacting surface being at least partially smoothened and a second rail including a bone-contacting surface being at least partially serrated, and the at least two rails of the lower portion including a first rail including a bone-contacting surface being at least partially smoothened and a second rail including a bone-contacting surface being at least partially serrated, wherein a portion of the at least partially serrated bone-contacting surface of the second rail of the upper portion is smoothened and another portion of the at least partially serrated bone-contacting surface of the second rail of the upper portion is roughened, wherein a portion of the at least partially serrated bone-contacting surface of the second rail of the lower portion is smoothened and another portion of the at least partially serrated bone-contacting surface of the second rail of the lower portion is roughened, wherein the first rail of the upper portion and the first rail of the lower portion facilitate insertion of the implant into a disc space between adjacent vertebrae, and the second rail of the upper portion and the second rail of the lower portion serve in holding the implant in position between the adjacent vertebrae. a leading end , an opposite trailing end , an upper portion extending between the leading and trailing ends , and a lower portion extending between the leading and trailing ends , the upper portion including a first portion positioned adjacent the leading end , a second portion positioned adjacent the trailing end , and at least two rails extending between the first and second portions of the upper portion , the lower portion including a first portion positioned adjacent the leading end , a second portion positioned adjacent the trailing end , and at least two rails extending between the first and second portions of the lower portion , the at least two rails of the upper portion including a first rail including a bone-contacting surface being at least partially smoothened and a second rail including a bone-contacting surface being at least partially serrated, and the at least two rails of the lower portion including a first rail including a bone-contacting surface being at least partially smoothened and a second rail including a bone-contacting surface being at least partially serrated, wherein a portion of the at least partially serrated bone-contacting surface of the second rail of the upper portion is smoothened and another portion of the at least partially serrated bone-contacting surface of the second rail of the upper portion is roughened, wherein a portion of the at least partially serrated bone-contacting surface of the second rail of the lower portion is smoothened and another portion of the at least partially serrated bone-contacting surface of the second rail of the lower portion is roughened, wherein the first rail of the upper portion and the first rail of the lower portion facilitate insertion of the implant into a disc space between adjacent vertebrae, and the second rail of the upper portion and the second rail of the lower portion serve in holding the implant in position between the adjacent vertebrae. <EOS>