BACKGROUND:
Controversy exists regarding the safety of bilateral simultaneous total hip arthroplasty, in part because of the potentially higher prevalence of pulmonary fat embolism. The purpose of the present study was to determine if unilateral and bilateral simultaneous total hip arthroplasty procedures resulted in different prevalences of fat embolization, different degrees of hemodynamic compromise, or different levels of hypoxemia or mental status changes.

METHODS:
One hundred and fifty-six consecutive patients undergoing primary total hip arthroplasty were prospectively enrolled in the study. The study group included fifty patients undergoing bilateral simultaneous total hip arthroplasty and 106 patients undergoing unilateral total hip arthroplasty. One hundred hips were treated with a cemented stem, and 106 were treated with a cementless stem. Arterial and right atrial blood samples were obtained before implantation (baseline); at one, three, five, and ten minutes after implantation of the acetabular and femoral components; and at twenty-four and forty-eight hours after the operation. Arterial blood pressure, right atrial pressure, arterial oxygen tension, and carbon-dioxide tension were also monitored at these times. The presence of lipid and cellular contents of bone marrow was determined.

RESULTS:
The prevalence of fat embolism was not significantly different between the groups managed with bilateral and unilateral total hip arthroplasty or between the groups managed with cemented and cementless stems. Similarly, the prevalence of bone-marrow-cell embolization was not significantly different between the groups managed with bilateral and unilateral total hip arthroplasty or between the groups managed with cemented and cementless stems. Patients with bone-marrow-cell embolization had a significantly lower arterial oxygen tension (p = 0.022) and oxygen saturation (p = 0.017) than did patients without bone-marrow-cell embolization on the first postoperative day. Four patients with bone-marrow cells in the blood samples that were obtained from the right atrium on the first postoperative day had development of diffuse encephalopathy with confusion and agitation that lasted for about twenty-four hours.

CONCLUSIONS:
The prevalence of fat and bone-marrow-cell embolization was similar in the groups managed with bilateral simultaneous and unilateral total hip arthroplasty as well as in the groups managed with cemented and cementless stems.



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