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The objective of the current study was to determine the effect of arthroscopic acromioplasty, and combined acromioplasty and distal clavicle resection on joint kinematics and in situ forces in response to an anterior, posterior, and superior load of 70 N. The loading conditions were applied to 10 fresh-frozen cadaveric shoulders using a robotic and universal force and moment sensor testing system. Translations in response to a posterior load increased by approximately 30% after combined acromioplasty and distal clavicle resection when compared with the intact and acromioplasty conditions. The in situ force in the trapezoid and conoid ligaments increased significantly from 13 +/- 15 N to 40 +/- 25 N and 13 +/- 13 N to 38 +/- 28 N, respectively, between the intact and combined acromioplasty and distal clavicle resection conditions during anterior loading. The results suggest that an arthroscopic acromioplasty alone does not significantly affect the mechanics of the acromioclavicular joint with these loading conditions. However, an acromioplasty combined with a distal clavicular resection does result in significant increases in joint motion and ligament forces. In some circumstances, such as after a previous joint separation, the increased forces in the coracoclavicular ligaments could result in additional damage to weak ligaments.

Prostaglandin E2 (PGE2) is known to stimulate osteolysis in vitro and has been implicated in mediating bone resorption in several animal and human tumors. Little attention has yet to be directed toward local humoral control (including PGE2) of bone resorption in primary and metastatic bone tumors. For investigation of whether histologically identified areas of osteolytic or osteoblastic bone tumors differentially secrete PGE2 under in vitro conditions, culture media from explants of central and peripheral areas of tissue were sterilely collected from 13 surgical specimens of primary and metastatic bone tumors and assayed for (PGE2) radioimmunoassay. The results indicate a marked heterogeneity in the concentration of immunoreactive (I-PGE2) synthesis by tumors of different as well as similar cell type. PGE2 production was time-dependent in culture, and at 72 hours substantial increases were apparent compared to cultures of non-neoplastic fascia controls. Significantly higher levels of I-PGE2 were found in cultures derived from "bone-destructive" tumors. No difference in I-PGE2 synthesis was found between explants of peripheral versus central tissue of the same tumors. PGE2 is synthesized in culture by bone tumors characterized as destructive of bone at higher levels than "bone-forming" tumors, and this synthesis is inhibited by indomethacin.