Buckle transducers were used to directly measure load sharing and overall force in three segment (semitendinosus, gracilis, Ligament Augmentation Device) and two segment (patellar tendon, LAD) composite ACL grafts during the application of anteriorly directed loads to a series of five fresh knee specimens with a pneumatic load apparatus. The total graft forces generated in the two segment and three segment composite reconstructions during this immediate postoperative state were highly variable when compared to the normal ACL in each specimen, and were irreproducible among the five specimens. Load sharing among the graft components occurred and was also variable in both reconstructions, with this variation being greater in the three segment graft. The LAD carried an average of 45% of the total graft force in the three segment graft and 28% in the two segment graft. Further work is required to clarify the source of the variability in the total graft force and load sharing observed in this study.

Biomechanical Phenomena↗

PubMedDate not supplied

Graft force-setting technique in reconstruction of the anterior cruciate ligament.

The objective of this work was to present a method for controlling the mechanical state of the knee during graft fixation in an ACL reconstruction; that is, adjusting the unloaded length of the graft at the time of fixation so that the force-carrying characteristics of the graft match that of the intact ACL, when the normal and reconstructed knees are subjected to the same external load. To demonstrate the new method, an experimental knee testing system was used to measure ligament and graft forces with buckle transducers, as external loads were applied to five fresh knee specimens with a pneumatic load apparatus. ACL and collateral ligament force data were collected as anteriorly directed loads of 90 N (20 pounds) were applied at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion in the normal intact knee and the same knee following ACL excision. A composite graft was prepared, consisting of distally based semitendinosus and gracilis autogenous tissue augmented with the Kennedy Ligament Augmentation Device. Femoral fixation was obtained using a fixation plug that was inserted through the lateral femoral condyle. With a 90 N anterior tibial load applied at 30 degrees of flexion and a single buckle transducer measuring the total composite graft force, the graft length was varied using the fixation plug until the force matched that seen by the intact ACL under the same loading condition. The graft was then clamped in the fixation plug and the anterior load sequence at the four flexion angles was applied to this reconstructed knee state.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMedDate not supplied

The effect of an iliotibial tenodesis on intraarticular graft forces and knee joint motion.

Lateral extraarticular reconstructions are used as isolated procedures in knees with moderate rotatory instability and as "backups" in knees requiring primary repair or intraarticular reconstruction for major rotatory instability. We used an experimental knee testing system to analyze the immediate postoperative mechanical effect of an iliotibial band tenodesis on an intraarticular reconstruction of the ACL in fresh cadaver knees using a composite graft consisting of a bone-patellar tendonbone segment augmented with the Kennedy Ligament Augmentation Device (LAD, 3M Co., St. Paul, MN). The intraarticular graft was standardized by using a forcesetting technique. Ligament and graft forces were measured using buckle transducers, and joint motion was measured using an instrumented spatial linkage as 90 N anteriorly directed tibial loads were applied to seven fresh knee specimens at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. The following knee states were tested in each specimen: intact ACL, excised ACL, intraarticular reconstruction, intraarticular reconstruction with the tenodesis added, and tenodesis with the intraarticular reconstruction added. Adding the iliotibial band tenodesis to an existing standardized intraarticular reconstruction significantly decreased the force in the ACL composite graft by an average of 43%. When the standardized intraarticular reconstruction was added to an existing tenodesis, the graft forces were an average of 15% below the level of when the reconstruction was performed alone. The force in the tenodesis was significantly less than the composite graft force at extension; however, the differences between the tenodesis and total graft force were not significant from 30 degrees to 90 degrees of flexion.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMedDate not supplied

Effect of anterior cruciate ligament graft tensioning direction, magnitude, and flexion angle on knee biomechanics.

The objective of this study was to determine the biomechanical effect of graft tensioning during reconstruction of the anterior cruciate ligament. We evaluated the magnitude of the tensioning force (22 or 67 N), the flexion angle at which the tension was applied (extension or 30 degrees of flexion), and the direction of application of the tensioning force (proximal, distal, or distal with a posterior force simultaneously applied to the tibia) on 10 fresh cadaveric knees. The anterior cruciate ligament was reconstructed using a bone-patellar tendon-bone graft. The graft was then temporarily fixed during the application of each of 12 combinations of tensioning variables listed above. After each fixation, graft force and joint motion were measured during anterior tibial loads. Tensioning direction and the flexion angle significantly affected graft force and joint motion, while the magnitude of the graft tensioning did not. Graft forces were greater when the tensioning was applied at 30 degrees of flexion. Compared with distal tensioning with and without posterior tibial force, graft forces with proximal tensioning were greater in extension and lower in flexion. The position of the tibia relative to the femur was posterior and externally rotated, compared with normal, for all combinations of tensioning variables in both unloaded and anterior load states.

Anterior Cruciate Ligament↗

PubMedDate not supplied

Biomechanics of ankle ligament reconstruction. An in vitro comparison of the Broström repair, Watson-Jones reconstruction, and a new anatomic reconstruction technique.

We wanted to use biomechanical testing in a cadaveric model to compare the Broström repair, the Watson-Jones reconstruction, and a new anatomic reconstruction method. Eight specimens were held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantar flexion and supination-pronation) could be varied in a controlled manner. Testing was done with intact ligaments and was repeated after sectioning of the anterior talofibular ligament and the calcaneofibular ligament and after a Broström repair, a Watson-Jones reconstruction, and a new anatomic reconstruction were performed. An anterior drawer test was performed using an anterior translating force of 10 to 50 N, and a talar tilt test was performed using a supination torque of 1.1 to 3.4 N-m. The forces in the anterior talofibular ligament and calcaneofibular ligament were measured with buckle transducers, and tibiotalar motion and total ankle joint motion were measured with an instrumented spatial linkage. The increase in ankle joint laxity observed after sectioning of both the anterior talofibular and calcaneofibular ligaments was significantly reduced by the three reconstructive techniques, although not always to the level of the intact ankle. Joint motion was restricted after the Watson-Jones procedure compared with that in the intact ankle. Unlike the Watson-Jones procedure, the ligament or graft force patterns observed during loading after the Broström repair and the new anatomic technique resembled those observed in the intact ankle.

Adult↗