Transfemoral Fixation in Soft Tissue Cruciate Ligament Reconstructions - Composite versus Polymeric Implant Analysis

摘要

Different methods are available for fixation on the femoral side of a quadruple soft tissue autograft in anterior cruciate ligament reconstruction and the best method is still to be found. There are also a large number of polymers in current practice, with a trend towards ceramic composites, required for better bone formation around the implant. If ceramic - polymer composites have better bioactive properties can be demonstrated only by long term in vivo follow up. Several methods of trans-femoral fixation are currently in use in our clinic - two of them being compared in this study: Rigidfix (Mitek DePuy Westwood, MA) and Biosteon (Stryker). First system produces a very stiff fixation using two implant pins made of poly-L-lactic acid (PLLA);;the second technique is using a large composite (25% hydroxyapatite and 75% PLLA) suspension system with the mechanical advantage of achieving a " press-fit" graft fixation in the tunnel. We prospectively follow our cases with clinical visits at 1, 3, 6 and 12 months - for research purposes, in a series of 20 cases (10 from each group) MRI (Siemens, 1,5 Tesla) were performed at same time intervals. Volume loss of the implant, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative pin replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels at more than 24 months of folllow-up. Several of the Biosteon sites were surrounded by an area of increased signal on the fat-suppressed images. At 12 months, the femoral implants showed an average volume loss of 80% (±10%) P0.05), respectively. At 3, 6, and 12 months volume losses range from 5 % (±2%), 29% (±19%) and 89% (±7%) for the composite implant. The femoral tunnel enlargement was less than 50% of the original bone tunnel volume after 12 months. Bone ingrowth was observed in all patients. Use of a composite ceramic - polymer bioabsorbable material (enhanced to form bone) will be easily incorporated by the body, retain strength for an adequate period of time, obviate the need for secondary procedures such as hardware removal, and facilitate revision surgery.