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

Abstract

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 x 25 mm for the femur, and 9 x 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.

RETRACTED ARTICLE: Graft fixation alternatives in anterior cruciate ligament reconstruction

“…The reasons for this are biomechanical and include greater bone mineral density of the distal femur as well as an angle of stress relative to fixation that is mechanically stronger in the femur than the tibia. Several studies indicate improved fixation in bone with increased bone mineral density [30,31]. The higher the bone mineral density, the higher the compressive stiffness.…”

“…The higher the bone mineral density, the higher the compressive stiffness. The distal femur has been demonstrated to have a greater bone mineral density than the proximal tibia [31]. The angle at which force is applied to the tibial fixation is in line with the intraosseous portion of the graft, whereas the force is oblique, and sometimes perpendicular, in the femoral bone tunnel.…”

Bioabsorbable screw divergence angle, not tunnel preparation method influences soft tissue tendon graft-bone tunnel fixation in healthy bone

“…While the use of young 7 Relationship between bioabsorbable interference screw divergence angle and construct displacement during cyclic testing (r 2 = 0.54) Fig. 8 Relationship between bioabsorbable interference screw divergence angle and load at failure (r 2 = 0.41) cadaveric femurs and tibiae would provide the most valid data for assessing soft tissue tendon graft fixation in a bone tunnel, the majority of cadaveric bones are from elderly specimens and have poor BMD which substantially lowers fixation strength [1,4,18]. In an active younger female population, proximal tibia apparent BMD [10,17,32] ranges from 1.07 to 1.3 g/ cm 2 while distal femur BMD ranges from 1.25 to 1.4 g/ cm 2 [10].…”

Prospective Comparison of Auto and Allograft Hamstring Tendon Constructs for ACL Reconstruction

“…This was to prevent the windshield wiper effect of the graft in the tunnel that sometimes has been implicated in tunnel widening. The metaphyseal fixation helped protect against theoretical cyclic slippage that has been reported with biointerference screw fixation of soft tissue grafts [7,8,18]. An identical postoperative rehabilitation protocol was used in both sets of patients and included immediate range of motion, home exercise, physical therapy, and continuous passive motion with importance placed on extension and flexion exercises.…”