A surgical access assembly comprising a retractor and a smooth and rounded introducer, wherein: the retractor (10, 50, 106) comprises: smooth outer walls having a continuous perimeter with no sharp edges, an oblong cross-section, and a gapless contour adapted to distribute pressure evenly along said outer wall and to minimize localized retraction pressure, smooth inner walls having a continuous perimeter with no sharp edges an oblong cross-section, a hollow access channel (28, 68, 116), and a gapless contour adapted to receive the smooth and rounded introducer (12, 42, 104); at least two vertical fixation shafts (22, 72, 114) adapted to receive fixating devices (18, 54, 118), the vertical fixation shafts (22, 72, 114) are placed at opposite ends of the retractor (10, 50, 106); and the smooth and rounded introducer (12, 42, 104) comprises: a continuous perimeter with no sharp edges, adapted with a contour and size to fit within said hollow access channel (28, 68, 116), and a length such that the distal end of said introducer (12, 42, 104) protrudes past the end of said hollow access channel (28, 68, 116) when inserted into said retractor (10, 50, 106) thereby providing a protruding nub (32, 62, 102), and said nub (32, 62, 102) forming a smooth contour characterized in that said retractor (10, 50, 106) has a flange (76, 136) forming the upper perimeter of said retractor (10, 50, 106), adapted to prevent tissue creep and extrusion over the top of said retractor (10, 50, 106). the retractor (10, 50, 106) comprises: smooth outer walls having a continuous perimeter with no sharp edges, an oblong cross-section, and a gapless contour adapted to distribute pressure evenly along said outer wall and to minimize localized retraction pressure, smooth inner walls having a continuous perimeter with no sharp edges an oblong cross-section, a hollow access channel (28, 68, 116), and a gapless contour adapted to receive the smooth and rounded introducer (12, 42, 104); at least two vertical fixation shafts (22, 72, 114) adapted to receive fixating devices (18, 54, 118), the vertical fixation shafts (22, 72, 114) are placed at opposite ends of the retractor (10, 50, 106); and smooth outer walls having a continuous perimeter with no sharp edges, an oblong cross-section, and a gapless contour adapted to distribute pressure evenly along said outer wall and to minimize localized retraction pressure, a continuous perimeter with no sharp edges, an oblong cross-section, and a gapless contour adapted to distribute pressure evenly along said outer wall and to minimize localized retraction pressure, smooth inner walls having a continuous perimeter with no sharp edges an oblong cross-section, a hollow access channel (28, 68, 116), and a gapless contour adapted to receive the smooth and rounded introducer (12, 42, 104); a continuous perimeter with no sharp edges an oblong cross-section, a hollow access channel (28, 68, 116), and a gapless contour adapted to receive the smooth and rounded introducer (12, 42, 104); at least two vertical fixation shafts (22, 72, 114) adapted to receive fixating devices (18, 54, 118), the vertical fixation shafts (22, 72, 114) are placed at opposite ends of the retractor (10, 50, 106); and the smooth and rounded introducer (12, 42, 104) comprises: a continuous perimeter with no sharp edges, adapted with a contour and size to fit within said hollow access channel (28, 68, 116), and a length such that the distal end of said introducer (12, 42, 104) protrudes past the end of said hollow access channel (28, 68, 116) when inserted into said retractor (10, 50, 106) thereby providing a protruding nub (32, 62, 102), and said nub (32, 62, 102) forming a smooth contour a continuous perimeter with no sharp edges, adapted with a contour and size to fit within said hollow access channel (28, 68, 116), and a length such that the distal end of said introducer (12, 42, 104) protrudes past the end of said hollow access channel (28, 68, 116) when inserted into said retractor (10, 50, 106) thereby providing a protruding nub (32, 62, 102), and said nub (32, 62, 102) forming a smooth contour