Chapter 11 Why Synthetic Grafts Failed

History of Synthetic Grafts for Anterior Cruciate Ligament Reconstruction

Synthetic grafts for anterior cruciate ligament (ACL) reconstruction had a brief period of popularity in the mid-1980s. At this time the routine operation was an open patellar tendon graft with 6 weeks of postoperative immobilization. The concept of implanting a sterile, off-the-shelf synthetic ligament with no postoperative immobilization was very appealing. There was no harvest site morbidity, and the rehabilitation was very quick. In a very short period, it was recognized that there was a higher rate of failure compared with autogenous grafts, an increased rate of late infection, considerable bone tunnel enlargement, and significant sterile effusions; in addition, the grafts were expensive. In a 2005 article reviewing the choices of graft for ACL reconstruction, West and Harner ¹ stated that there is no indication for synthetic ligaments.

Types of Synthetic Grafts

During the 1980s, numerous synthetic grafts were developed. They were used either as augmentation or as a complete prosthetic replacement. One of the original grafts that was designed as an augmentation device was the Kennedy ligament augmentation device (LAD). When this graft was sutured to the autogenous graft and fixed to the bone at both ends, it stressed shielded the autogenous graft and led to failure. Gore-Tex was a prosthetic graft, but it was placed in a nonanatomical position over the top of the femur. The theory was to avoid the bending forces at the entrance to a femoral tunnel. However, because this was a nonanatomical position, it eventually led to graft failure at the proximal tunnel (a second tunnel was drilled in the femur several inches above the joint capsule). The Styker Dacron graft was a complete replacement graft placed through anatomical tunnels in the femur and tibia. The ABC graft was a combination of polyester and carbon fiber, and it was also placed through bony tunnels. The Ligastic graft was another polyester graft that evolved to the LARS graft. This was placed through bony tunnels and could be used as augmentation or as a complete prosthetic replacement. The graft was anchored in the tunnels with metal interference screws. The Leeds-Keio was a coventure between Leeds University in England and Keio University in Japan. This was a polyester mesh graft designed to augment the autogenous graft. It was placed through bony tunnels and anchored outside the tunnel with staples. The Trevira ligament was polyester and resembled the LAD in design, but it was placed in a nonanatomical position.

Causes of Failure of Synthetic Grafts

The most common cause of failure of synthetic grafts was the fiber abrasion due to bending forces over the edge of the bony tunnels (Fig. 11-1). In order to avoid this problem, the Gore-Tex graft was placed over the top of the femur. This nonanatomical position eventually led to graft failure. Carson et al² have stated that approximately 50% of the failures of ACL reconstruction are due to technical error, and the anterior femoral tunnel placement is one of the most common errors. It is likely that many of the failures of synthetic grafts were due to the same causes. The literature has numerous articles reporting the unacceptable failure rate after synthetic ACL reconstruction. Kumar and Maffuli³ reported on the stress shielding caused by the use of the LAD. Riel⁴ reported numerous complications following the use of the LAD and concluded that there was no indication for its use. Muren et al⁵

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