The varus-valgus stability of M knees with unicompartmental osteoarthritis was studied in vivo at the time of total knee replacement. Intact osteoarthritic knees had an average of 11.0" of varus-valgus motion. Removal of osteophytes from the osteoarthritic compartment significantly increased the motion to 13.1" (P < 0.05), while subsequent removal of osteophytes from the nonosteoarthritic compartment further increased motion to 14.7" ( P < 0.025). In primarily unicompartmental osteoarthritis, marginal osteophytes appear to stabilize osteoarthritic knees, but can cause fixed deformity.

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A B S T R A C T The removal of bovine proinsulin by the isolated perfused rat liver has been studied and the results compared with the removal of insulin. At high concentrations of insulin (> 180 ng/ml) the removal process was saturated and the ti varied between 35 and 56 min. With low initial insulin levels the disappearance followed first-order kinetics, the mean regression coefficient being -0.022, to 13.8 min, and the hepatic extraction 4.0 ml/min. The results with proinsulin were in striking contrast to these findings. At both high and low concentrations the hepatic removal of proinsulin was considerably slower, averaging 10-15 times less than that of insulin. Specific immunoassay techniques and gel filtration of samples taken from perfusions to which both labeled and unlabeled proinsulin had been added did not show conversion to either insulin or the C-peptide.Bovine and rat 'I-labeled proinsulins were degraded more slowly than bovine insulin-'1I by bovine and rat liver homogenates. Both proinsulin and insulin inhibited the degradation of insulin-tI, equimolar quantities of proinsulin being 2-5 times less effective than insulin.These results indicate significant differences in the capacity of the liver to remove and degrade insulin and proinsulin. The low hepatic extraction of proinsulin may account for its prolonged half-life in vivo and contribute to its relatively high plasma concentration in the fasting state. Furthermore this finding will have to be taken into account in the interpretation of changes in the proinsulin: insulin ratios in peripheral blood in a variety of metabolic situations.

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