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Thirty-six of 44 patients (82%) who underwent ACL reconstruction using freeze-dried, ethylene oxide-sterilized, bone-patellar tendon-bone allografts were evaluated at least 2 years postoperatively. A detailed subjective evaluation using the Lysholm scale was recorded as well as a functional evaluation using the Tegner activity scale. All of the patients received a detailed physical examination that included testing with the KT-1000 ligament arthrometer and the Cybex dynamometer. Complete chart reviews and radiographic evaluations were also obtained. Only 17 patients were considered to be functionally successful and performing at their desired activity level. The average KT-1000 showed a side-to-side difference of 5.9 mm at 30 pounds for the successful group and 7.9 mm for those who had functional failure. The Lysholm scores were 91.6/100 versus 61.1/100 in the failures. Eight patients (22%) at repeat surgery were noted to have complete dissolution of the graft. Large femoral cysts were noted radiographically in all of these patients. It was concluded that freeze-dried, ethylene oxide-sterilized, bone-patellar tendon-bone allografts have a high failure rate and cannot be recommended for ACL reconstruction.

From July 1988 to August 1989, six children with open physes and injuries to the anterior cruciate ligament were treated operatively. All injuries involved twisting episodes during sports activities. All six patients had meniscal abnormalities, and, additionally, one patient sustained a Grade III medical ligament tear and had a lateral patellar dislocation. Operative reconstruction used hamstring tendons and place a groove over the front of the tibia and a groove over the top of the femur without violation of the growth plates. The anterior cruciate ligament was primarily repaired (three patients) at the time of reconstruction, if possible. At 3 months, one patient underwent arthroscopic resection of adhesions for arthrofibrosis. There were no other complications. Five patients were evaluated with clinical examination, radiographs, magnetic resonance imaging, and functional testing at an average followup of 33.2 months (range, 25 to 38). Four of the five had returned to their preinjury level of sports participation. Manual maximum KT-1000 arthrometer side-to-side differences averaged 3.6 +/- 1.9 mm. The average Lysholm knee score was 95.2 +/- 2.5; the average Hospital for Special Surgery knee score was 96.6 +/- 2.3. There were no growth plate injuries. Despite the overall clinical stability, magnetic resonance image scans of the five patients consistently demonstrated areas of increased signal in the anterior cruciate ligament grafts.

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Total anterior-posterior translation is commonly used to assess the integrity of the cruciate ligaments and the success of reconstructive surgery. The purpose of this study was to determine, after surgical reconstruction of the anterior cruciate ligament with a biological graft, if total anterior-posterior translation correlated with graft length, cross-sectional area, or mechanical properties. These factors were investigated by analyzing data from three previous studies. These studies involved replacement of the anterior cruciate ligament in cynomolgus monkeys and goats, with free and vascularized patellar tendon autografts and both patellar tendon and anterior cruciate ligament allografts. Data were available at time periods of 6 and 12 months after surgery. We found statistically significant inverse correlations between the amount of anterior-posterior translation and cross-sectional area of a graft at the time of sacrifice. The Pearson correlation coefficients ranged from -0.966 (p < 0.002) to -0.830 (p < 0.05). We hypothesize that these correlations result from the following mechanism: the increased anterior translation reflects a slack graft; a slack graft is stress shielded by other structures about the knee; the reduced in vivo stresses on the graft modulate cellular metabolism in a way that over time produces a small cross-sectional area.

In 16 adult dogs the anterior cruciate ligament (ACL) was transected and then reconstructed using freeze dried fascia lata allografts. Eight of the dogs had the intraarticular graft passed through drill holes in the tibia and femur, while in the other eight dogs the graft was passed through a drill hole in the tibia and routed "over-the-top" of the lateral femoral condyle. In all dogs the grafts were then passed deep to the lateral collateral ligament and secondarily secured to the tibia as an extraarticular reconstruction. Specimens from each group underwent histologic study and biomechanical testing on a mechanical testing system at 3, 6, 12, and 24 week intervals. All grafts were found to be intact at sacrifice with no overt evidence of biologic incompatibility. The knees displayed only mild instability to clinical testing without evidence of arthrosis. Histologically, the grafts appeared to function as a collagenous scaffolding for revascularization and fibrovascular creeping substitution. The mean maximum load at failure in the 24 week specimens reached 536.44 N, compared to values of 801.85 N in contralateral knees with an intact ACL.

Twenty-eight goats underwent ACL reconstruction with freeze-dried bone-patellar tendon-bone allografts in one knee, the opposite knee serving as a control. One group of 16 knees was evaluated, in groups of four, at 6, 12, 26, and 52 weeks by histologic and vascular injection techniques. The other group of 12 knees was evaluated in two groups of six at 26 and 52 weeks by morphological and biomechanical techniques of analysis. Within the first 12 weeks these allografts were revascularized; in the first 26 weeks they had matured to resemble normal connective tissue. Graft stiffness was 29% of the control value and maximum force to failure was 43% of the control value. The results of this study indicated that freeze-dried bone-patellar tendon-bone allografts are biomechanically and biologically similar to patellar tendon autografts.

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