Perioperative morbidity after single-stage bilateral total hip arthroplasty: a matched control study.

We asked whether the perioperative morbidity and mortality of patients having bilateral single-stage total hip arthroplasties would be increased. We retrospectively compared 400 patients who had bilateral total hip replacements with a matched group of 400 patients who had unilateral total hip replacements. Patients were matched according to age (+/- 1 year), gender, American Society of Anesthesiologists (ASA) classification, body mass index (+/- 4 kg/m), and diagnosis (osteoarthritis, 81.2%). There were no deaths in either group. The group of patients who had bilateral total hip arthroplasties had a greater number of minor complications per hip (0.34 +/- 0.6 versus 0.25 +/- 0.6) but only a trend toward an increased number of major complications per hip (0.037 +/- 0.2 versus 0.015 +/- 0.1). Patients who had bilateral total hip arthroplasties had a trend toward increased risk of dislocation (1.6%/hip versus 0.5%/hip). The patients in this group also had increased number of fat emboli syndrome per surgically treated hip (0.015 versus 0.0025). Based on a calculation per surgically treated hip, patients who had bilateral total hip arthroplasties had a similar percentage of blood transfusions (1.2 versus 0.9/hip), but more patients received allogeneic blood (23% versus 3.8%). The ASA classification was the only independent predictor for minor complications, major complications, and fat emboli syndrome. We think bilateral single-stage total hip arthroplasties have an acceptable perioperative risk for patients with ASA Class 1 or 2 physical status.

The pathogenesis of fat embolism.

Fat embolism is a common autopsy finding in patients with or without a history of trauma. There are two basic mechanisms causing fat to embolize. Depot-derived fat embolism arises by disruption of depot fat, usually as a result of trauma, allowing direct entry into the bloodstream. Plasma-derived fat embolism is caused by agglutination of endogenous or infused exogenous fat such as Intralipid, with consequent embolism. Chylomicrons and Intralipid liposomes are known to undergo calcium-dependent agglutination by C-reactive protein (CRP), and this may play a role in vivo in this type of fat embolism.