The purpose of this study is to compare the safety and efficacy of continuous infusion versus intermittent bolus infusion employing rAHF-PFM, a recombinant antihemophilic factor manufactured without added human or animal proteins, in previously treated patients with severe or moderately severe hemophilia A (baseline factor VIII level <= 2% of normal) who are undergoing unilateral primary total knee replacement. The total study period per subject (from consent to study completion) will vary from approximately 9 to 12 weeks and will involve clinical and laboratory assessments.

• Drug: Recombinant Protein-Free Factor VIII (rAHF-PFM)

  An initial loading dose will be administered intravenously over a period <= 5 minutes (maximum of infusion rate of 10 mL/minute) within 60 minutes prior to surgery dose in order to maintain a minimum target FVIII level of at least 80% of normal.

  CI will start prior to surgery as soon as the loading dose has been administered, at a rate calculated according to a formula provided by the sponsor.

  All study product must be administered with a syringe pump running at an infusion rate according to the dosing regimen, but always >= 0.4 mL/h.

• Drug: Recombinant Protein-Free Factor VIII (rAHF-PFM)
  The treatment schedule for intermittent BI of rAHF-PFM will begin with the administration of the loading dose according to the dose recommendations provided by the sponsor. If required by the hemostatic challenge, additional boluses may be administered after a blood sample for FVIII determination has been drawn. All infusions of rAHF PFM will be given over a period <= 5 minutes (maximum infusion rate, 10 mL/min).

• BI: Experimental
  Bolus infusion of rAHF-PFM
  Intervention: Drug: Recombinant Protein-Free Factor VIII (rAHF-PFM)
• CI: Experimental
  Continuous infusion of rAHF-PFM
  Intervention: Drug: Recombinant Protein-Free Factor VIII (rAHF-PFM)

Inclusion Criteria:

• The subject or the subject's legally authorized representative has provided signed informed consent.
• The subject is within 18 to 70 years of age.
• The subject has severe or moderately severe hemophilia A, defined by a baseline factor VIII level <= 2% of normal, as tested at screening. A subset of 15 subjects per group must have baseline factor VIII levels < 1% of normal.
• The aPTT must be within the range of normal after administration of FVIII concentrate, as determined in the preoperative pharmacokinetic evaluation, or as documented in the medical history, if available.
• The subject is scheduled to undergo an elective unilateral primary total knee replacement (with cemented or uncemented prosthesis).
• The subject was previously treated with factor VIII concentrate(s) for a minimum of at least 150 exposure days (as estimated by the investigator) prior to study entry.
• Human immunodeficiency virus (HIV) positive subjects must be immunocompetent as determined with a CD4 count >= 400 cells/mm³ (CD4 count at screening), but HIV negative subjects with a CD4 count < 400 cells/mm³ qualify, if immunocompetency is documented.
• The subject has a life expectancy of at least 28 days from the day of surgery.

Exclusion Criteria:

• The subject has a detectable factor VIII inhibitor at screening, with a titer >= 0.4 BU (Nijmegen modification of the Bethesda assay) in the central laboratory.
• The subject has a history of factor VIII inhibitors with a titer >= 0.4 BU (by Nijmegen assay) or >= 0.5 BU (by Bethesda assay) at any time prior to screening.
• The subject is scheduled to undergo any other concurrent minor or major surgery during the course of the study. The placement of central venous lines and the performance of fine needle aspiration biopsies are permitted.
• Excluding hemophilia-related physical impairments, the subject is assigned to NYHA class >= III according to the New York Heart Association (NYHA).
• The subject has an abnormal renal function (serum creatinine > 1.5 mg/dL).
• The subject has active hepatic disease (alanine aminotransferase [ALT] or aspartate aminotransferase [AST] levels > 5 times the upper limit of normal).
• The subject has severe chronic liver disease as evidenced by, but not limited to, any of the following: International Normalized Ratio (INR) > 1.4, hypoalbuminemia, portal vein hypertension including presence of otherwise unexplained splenomegaly and history of esophageal varices.
• The subject has clinical and/or laboratory evidence of abnormal hemostasis from causes other than hemophilia A (e.g., late-stage chronic liver disease, immune thrombocytopenia purpura).
• The subject is currently receiving, or is scheduled to receive during the course of the study, an immunomodulating drug other than anti-retroviral chemotherapy (e.g., alpha-interferon, corticosteroid agents at a dose equivalent to hydrocortisone greater than 10 mg/day).
• The subject has a known hypersensitivity to mouse or hamster proteins.
• The subject is participating in another investigational drug study within 30 days prior to screening.
• The subject is identified by the investigator as being unable or unwilling to cooperate with study procedures.