Jeff C. Brand

Graft Fixation in Cruciate Ligament Reconstruction

Cruciate ligament reconstruction has progressed dramatically in the last 20 years. Anatomic placement of ligament substitutes has fostered rehabilitation efforts that stress immediate and full range of motion, immediate weightbearing, neuromuscular strength and coordination, and early return to athletic competition (3 months). This has placed extreme importance on secure graft fixation at the time of ligament reconstruction. Current ligament substitutes require a bony or soft tissue component to be fixed within a bone tunnel or on the periosteum at a distance from the normal ligament attachment site. Fixation devices have progressed from metal to biodegradable and from far to near-normal native ligament attachment sites. Ideally, the biomechanical properties of the entire graft construct would approach those of the native ligament and facilitate biologic incorporation of the graft. Fixation should be done at the normal anatomic attachment site of the native ligament (aperture fixation) and, over time, allow the biologic return of the histologic transition zone from ligament to fibrocartilage, to calcified fibrocartilage, to bone. The purpose of this article is to review current fixation devices and techniques in cruciate ligament surgery.

Interference Screw Fixation Strength of a Quadrupled Hamstring Tendon Graft Is Directly Related to Bone Mineral Density and Insertion Torque

The purpose of this study was to determine whether bone mineral density of the host bone, measured using conventional dual photon absorptiometry techniques, and insertion torque can predict part of the ultimate failure strength of interference screw fixation of quadrupled hamstring tendon grafts. The semitendinosus and gracilis tendons were harvested from 10 human cadaveric knees, mean age 66.5 years (range, 53 to 81). The bone tunnel was sized within 0.5 mm of the graft. The graft was fixed with a biodegradable screw (7 25 mm for the femur, and 9 25 mm for the tibia) directly against the tendon and at the joint surfaces. Tibial fixation and femoral fixation were tested to failure using a materials testing system. Bone mineral density was measured in the metaphyseal region of the tibia and femur. The results of multiple regression analyses showed that both insertion torque and bone mineral density were related to the maximum load the graft withstood. These two variables explained 77.1% of the maximum load observed. We concluded that bone mineral density measurements of the host bone site are an important determinant of postoperative graft strength and thus have an important, but previously unrecognized, clinical role in establishing individual postsurgery rehabilitation protocols. Insertion torque in this study was a useful predictor of graft fixation strength.

A Biomechanical Comparison of Initial Soft Tissue Tibial Fixation Devices The Intrafix Versus a Tapered 35-mm Bioabsorbable Interference Screw

Background Biomechanical testing of the Intrafix device has not been performed using human tibiae. Hypothesis The Intrafix device would provide comparable or superior tibial fixation of a quadrupled hamstring tendon graft to a 35-mm-long bioabsorbable interference screw. Study Design In vitro, biomechanical study. Methods Eight paired human tibiae and 16 quadrupled hamstring tendon grafts were divided into 2 groups. Each quadrupled hamstring tendon graft was fixed in a tunnel sized to 0.5 mm graft diameter with either an Intrafix device or a screw. Results Displacement at failure was greater in the Intrafix group (17.3 ± 4.6 mm versus 10.9 ± 4.4 mm, P = .002). Load at failure (796 ± 193 N versus 647 ± 269 N), stiffness (49.2 ± 21.9 N/mm versus 64.5 ± 22 N/mm), and bone mineral density (0.74 ±0.15 gm/cm3 versus 0.74 ± 0.14 gm/cm3) did not display significant differences for the Intrafix device and the screw, respectively (P > .05). Conclusions Displacement at failure was greater for the Intrafix device. Clinical Relevance Increased displacement at failure for the Intrafix group suggests slippage from sheath channel deployment. Concentric fixation may not occur when less than optimal tibial bone mineral density increases the difficulty of attaining precise sheath deployment and quadrupled hamstring tendon graft strand alignment.

Graft fixation issues in kneeligament surgery

Abstract The popularity of soft tissue grafts, particularly the semitendinosus and gracilis, has raised several issues with regard to graft fixation in cruciate ligament reconstruction. What is the force required by activities of daily living and a progressive rehabilitation program? Does soft tissue fixation alter the biological process of graft incorporation compared with the use of a bone plug? This article reviews the mechanical properties and use of fixation devices. Interference screw fixation of a patella tendon bone plug has been clinically reliable. Relative ease of fixation, acceptable initial strength, and fixation close to joint surfaces contribute to the popularity of cruciate ligament reconstruction with patella tendon bone plug. Biodegradable interference screw fixation of a bone plug is a reasonable alternative to metal screw fixation, which has several disadvantages. Many forms of tendon fixation are placed at a distance from the joint and rely on linkage materials, resulting in graft tunnel shear forces and possible tunnel expansion. Direct interference screw fixation may alleviate these detractions, but ultimate failure at time zero, particularly tibial fixation, may not allow for a progressive rehabilitation program, which our patients currently benefit from with interference fixation of a bone plug. Diminishing individual fiber movement within the tendon graft and the elimination of linkage materials will improve future soft tissue fixation.

Initial Assessment: Physical Examination and Imaging Studies

Generally considered rare, from 0.001 to 0.013% per year at various institutions, the multiple ligament injured knee may be more common than we in the orthopaedic community appreciate.1–8 A spectrum exists between the high velocity knee dislocation and the low velocity (bicruciate injuries) or sports-related multiple ligament injured knee. The multiple ligament injured knee can be missed, particularly by primary care physicians who increasingly provide care to this patient population.