In an attempt to assess reconstruction of the anterior cruciate ligament (ACL) by a new method, 18 New Zealand white rabbits underwent ACL replacement using the medial one-third of the patellar tendon and the semitendinosus tendon, thus partly reproducing the anatomical configuration of the ACL, with the semitendinosus tendon replacing the posterolateral bundle of the ACL and the patellar tendon replacing the anteromedial bundle. The Noulis-Trillat-Lachman test was performed before and after transection of the ACL, after reconstruction and before sacrifice. The animals were divided into four groups and were killed at 3, 6, 12 and 22 weeks after surgery. Femur-ligament-tibia complexes were evaluated postoperatively for gross morphology and histological appearance. The tendons of the first group showed compact parallel fibres with no definitive separation of their bundles and areas of disorganized collagen matrix. Tendons were surrounded by trabecular lamellar bone haphazardly arranged. The tendons of the second, third and fourth groups looked more like normal tendon. The trabecular bone surrounding the tendons formed a tunnel. The Noulis-Trillat-Lachman test result was negative before the procedure, 6.5 +/- 0.5 mm on average after transection of the ACL, 1.5 +/- 0.6 mm after the procedure, and negative again before sacrifice. The joints of the animals killed at 12 and 22 weeks showed signs of osteoarthritic lesions.

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Though osteoid osteoma is a common primary benign lesion of the bones, intra-articular involvement is rare and poses diagnostic difficulties when it affects middle-aged patients. We present the case of a 51-year-old woman with a 2.5 year history of anterior knee pain that was misdiagnosed as osteochondritis dissecans. Radiological findings were absent, whereas MRI showed a well-circumscribed lesion. A local excisional biopsy was performed and microscopic appearance confirmed diagnosis.

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