Introduction

The number of surgeons using hamstring tendons for anterior cruciate ligament (ACL) reconstruction has continuously increased in the past years. As a result, various modifications associated with graft preparation and fixation have been introduced. However, despite these variations in technique, the goal of reconstructing a strong and viable graft with a dependable fixation system remains unaltered. The standard means by which mechanical fixation of hamstring grafts is achieved can either be through direct (interference screws) or indirect (Endobutton [Smith & Nephew, Andover, MA] or screw and washer) techniques. Direct fixation is achieved with an interference screw. With this technique, factors such as divergence, direction of screw placement, the geometry and material composition of the screw, and the graft and tunnel characteristics should be considered to increase the likelihood of a successful outcome.^1,2

Indirect fixation techniques, on the other hand, require a linkage material (tape or suture) that would connect the graft tissue to the fixation device. Factors to consider with this technique include: (1) the strength and stiffness of the linkage material to minimize both the potential for elongation of the graft-fixation device construct^3–5 and graft-tunnel motion^6–8 and (2) the distance of graft fixation from the joint line, which can also influence graft-tunnel motion, especially with early stress on the graft during aggressive rehabilitation. The farther the fixation site from the joint line, the greater the creep of the graft-fixation device construct.^2,5

The technique described here incorporates the use of the Fastlok device (Neoligaments, Leeds, United Kingdom), which is an indirect graft tibial fixation system for hamstring tendon grafts.

Scientific Rationale

A variety of options are available for hamstring tendon graft tibial fixation during ACL reconstruction. These include different types of washers (AO, Washerloc, and Spiked Washer), staples, suture/post, and bioabsorbable screws.^9–12 Ideally, the type of fixation chosen should provide the strength and stiffness necessary to withstand failure during cyclical loading, allow the strands to be equally tensioned and compressed into the tibial tunnel wall, and also have the provision for removal when the need arises for revision reconstruction.

The use of only the semitendinosus tendon for ACL reconstruction minimizes the possibility of having subsequent flexor weakness from the disruption of the hamstring muscle. With the quadrupled configuration of this graft construct, indirect fixation is usually required because of the total length of the graft achieved.^13,14 In the description of the technique that follows, the Fastlok device is combined with a tibial tunnel bone plug that provides additional tunnel compression, which facilitates tendon to bone healing and at the same time reduces the risk for tunnel widening by limiting the sagittal motion of the graft.¹⁵ The Fastlok, on the other hand, offers the ease of using a simple threading technique during application, which helps the graft to retain tension throughout the fixation procedure. In addition, it also minimizes slippage with the staple and buckle fixation, reducing the risk of suture and graft loosening while at the same time maintaining a low profile, which is very important considering the relatively thin soft tissues that cover the involved area of the medial aspect of the proximal tibia.

Surgical Technique

Following the administration of the appropriate anesthesia, the patient is positioned supine on the operating table. A thigh support is placed at the level of the tourniquet cuff while a foot bar is positioned at the end of the table to enable the knee to be fixed at 90 degrees of flexion during surgery while at the same time still allowing free range of motion. Standard prepping and draping of the operative field are performed. During the graft harvest, the tourniquet is kept inflated. Anatomical dissection is carried out to identify the semitendinosus tendon (ST) and separate its accessory limb to avoid premature amputation of the graft. The tendon’s proximal end is detached with the use of an open tendon stripper while its distal end is harvested with an attached tibial bone plug obtained with the aid of an osteotome. Ideally, a graft length of 28 to 30 cm is desired. In the meantime, diagnostic arthroscopy and any associated procedures (e.g., meniscectomy) are performed prior to the preparation of the bone tunnels.

The graft is then prepared at the back table, as described in Chapter 16, “Hamstring Anterior Cruciate Ligament Reconstruction with a Quadrupled or Tripled Semitendinosus Tendon Graft.”