We hypothesized that an exogenous bone growth factor could augment healing of a tendon graft in a bone tunnel in a rabbit anterior cruciate ligament-reconstruction model. Seventy rabbits underwent bilateral anterior cruciate ligament reconstructions with a semitendinosus tendon graft. One limb received a collagen sponge carrier vehicle containing a mixture of bone-derived proteins while the contralateral limb was treated with either no sponge or a sponge without bone-derived proteins. The reconstruction was evaluated at 2, 4, or 8 weeks with histologic, biomechanical, and magnetic resonance imaging analysis. Histologic analysis demonstrated that specimens treated with bone-derived proteins had a more consistent, dense interface tissue and closer apposition of new bone to the graft, with occasional formation of a fibrocartilaginous interface, when compared with control specimens. The treated specimens had significantly higher load-to-failure rates than did control specimens. Treatment with bone-derived proteins resulted in an average increase in tensile strength of 65%. The treated specimens were stronger than control specimens at each time point, but the difference was greatest at 8 weeks. On the basis of signal characteristics and new bone formation, magnetic resonance imaging was useful for predicting which limb was treated, the site of failure, and the limbs with higher load-to-failure values. This study demonstrates the potential for augmenting tendon healing in an intraarticular bone tunnel using an osteoinductive growth factor.
Based on results of this study, and given the low turnover of collagen in ligaments, it is unlikely that a 2- to 3-day per month increase in circulating estrogen would result in rapid, clinically significant alterations in material properties of the anterior cruciate ligament in vivo. The etiology of noncontact anterior cruciate ligament injuries is complex and multifactorial in nature, meriting further investigation.
Patients may present with a primary complaint of intra-articular knee masses causing mechanical symptoms of snapping or locking. If the history, physical examination, laboratory tests, and imaging studies point to a benign process, acceptable treatment consists of arthroscopic excision and postoperative pathology analysis. As reported in several case series, the final diagnosis can be pigmented villonodular synovitis, localized nodular synovitis, hemangioma, lipoma, or rheumatoid nodules. In this case presentation, a 39-year-old man with no previous medical conditions and a negative preoperative chest radiograph underwent arthroscopic surgery for a single intra-articular knee mass. The unexpected diagnosis, after pathology review and further medical work-up, was arthritis secondary to chronic sarcoidosis.
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