Transfemoral amputation following total knee arthroplasty: mortality and functional outcomes.

AIMS: The aim of this study was to characterize the factors leading to transfemoral amputation after total knee arthroplasty (TKA), as well as the rates of mortality and functional independence after this procedure in these patients. PATIENTS AND METHODS: This was a multicentre retrospective review with a prospective telephone survey for the assessment of function. All patients with a TKA who subsequently required transfemoral amputation between January 2001 and December 2015 were included. Demographic information, medical comorbidities, and postoperative mortality data were collected. A 19-item survey was used for the assessment of function in surviving patients. RESULTS: A total of 111 patients were included. Their mean age was 61.0 years (42.0 to 88.0) at the time of TKA, with a subsequent mean of 3.7 operations (0 to 15) over a mean period of 6.1 years (0.05 to 30.1) before amputation. The indication for amputation was chronic infection in 97 patients (87.4%). The rate of five-year survival was 51.7%, and advanced age (p = 0.001) and renal failure (p = 0.045) were associated with an increased risk of mortality. Of the 62 surviving patients, 34 completed the survey; 32 (94.1%) owned a prosthesis but only 19 (55.9%) used it; 19 (55.9%) primarily used a wheelchair for mobility; 27 (79.5%) had phantom pain; and 16 (47.1%) required chronic pain medication. Only 18 patients (52.9%) were satisfied with the quality of life. CONCLUSION: Patients with complications after TKA, in whom transfemoral amputation is considered, should be made aware of the high rate of mortality and the poor functional outcome in the survivors. Alternative forms of treatment including arthrodesis of the knee should be investigated.

In vivo regulation of beta-adrenergic receptors on human mononuclear leukocytes: assessment of receptor number, location, and function after posture change, exercise, and isoproterenol infusion.

We studied the regulation of beta-adrenergic receptors in human mononuclear leukocytes (MNL). Total receptor number was determined as specific binding at 4 C of [3H] dihydroalprenolol or [125I]iodopindolol, and redistributed receptors were defined as those binding sites to which the hydrophilic antagonist CGP-12177 did not have access. Receptor function was assessed as cAMP accumulation stimulated by isoproterenol. In in vitro experiments, high concentrations of isoproterenol desensitized receptor function and promoted redistribution of about 80% of the receptors away from the cell surface. However, three in vivo protocols (upright posture for 3 h, moderate exercise, and infusion of isoproterenol for 30 min) redistributed few beta-adrenergic receptors on MNL. The 30-min isoproterenol infusion did not alter later cAMP accumulation, but posture change and exercise increased isoproterenol-stimulated cAMP accumulation in intact MNL. Infusion of isoproterenol for 120 min redistributed 9 +/- 2% (+/- SEM) of the receptors and decreased isoproterenol-stimulated cAMP accumulation by 19 +/- 6%. Isoproterenol-stimulated adenylate cyclase activity in membranes isolated from MNL previously was found to be decreased with upright posture, and we confirmed these findings in assays that did not include exogenous GTP, but instead relied upon guanine nucleotides retained in the membrane preparation. However, when excess GTP was included, isoproterenol-stimulated adenylate cyclase activity in MNL membranes was not altered by posture change. We conclude that substantial receptor redistribution of beta-receptors on MNL does not readily occur in physiological situations.