A Prospective Randomized Study to Compare Systemic Emboli Using the Computer-Assisted and Conventional Techniques of Total Knee Arthroplasty Rajesh Malhotra, MS, FRCS, Amit Singla, MBBS, MS, Chandra Lekha, MBBS, MD, Vijay Kumar, MS, Ganesan Karthikeyan, MBBS, MD, DM, Vishwas Malik, MBBS, MD, DM, and Asit R. Mridha, MBBS, MD Investigation performed at the Department of Orthopaedics, All India Institute of Medical Sciences (AIIMS), New Delhi, India Background: Conventional total knee arthroplasty is performed with use of an intramedullary alignment guide, which produces elevated intramedullary pressure that can create fat emboli. Total knee arthroplasty performed via computer- assisted surgery does not require an intramedullary femoral rod, raising the question of whether computer-assisted surgery generates less embolic material than conventional total knee arthroplasty. The purpose of this study was to compare the emboli produced in the two techniques. Methods: Fifty-seven patients were randomized into two groups: the computer-assisted surgery group (n = 29) and the conventional total knee arthroplasty group (n = 28). An intramedullary femoral alignment jig was used in the conventional total knee arthroplasty group but not in the computer-assisted surgery group. Intraoperative invasive monitoring was performed with use of transesophageal echocardiography and a pulmonary artery catheter. Results: The mean embolic score was 6.21 points for the conventional technique group and 5.48 points for the computer-assisted surgery group (p = 0.0161). After tourniquet deflation, fat emboli were observed in the blood of five patients in the conventional surgery group and one patient in the computer-assisted surgery group. Conclusions: The patients in the computer-assisted surgery group had lower embolic loads compared with the patients in the conventional total knee arthroplasty group. In patients with an uncompromised cardiopulmonary system, the embolic load difference between the techniques was not clinically relevant. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence. I n conventional total knee arthroplasty with use of intra- medullary instrumentation, the elevated intramedullary pressures generated by the alignment rods can cause fat emboli 1,2 . Emboli may enter the heart through the venous system and are referred to as “fat emboli, ” although they may also contain bone marrow elements, air, and blood clots. The emboli may adversely impact the patient’ s cardiac, pulmo- nary, and cognitive status and may even result in death 3,4 . Total knee arthroplasty performed with computer-assisted surgery avoids the use of an intramedullary femoral rod. Therefore, computer-assisted surgery should generate less embolic material compared with conventional instrumenta- tion. Previous studies 5-7 have yielded mixed results with re- gard to the computer-assisted surgery-generated embolic load. Our hypothesis was that total knee arthroplasty per- formed with computer-assisted surgery would result in a lower embolic burden compared with surgery with conven- tional instrumentation. We also studied the type of emboli generated and the immediate clinical implications of the emboli. Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article. Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors. 889 COPYRIGHT Ó 2015 BY THE J OURNAL OF BONE AND J OINT SURGERY,I NCORPORATED J Bone Joint Surg Am. 2015;97:889-94 d http://dx.doi.org/10.2106/JBJS.N.00783