Bone Reconstruction in Revision Total Knee Arthroplasty Issada Thongtrangan, Patrick Yoon, and Khaled J. Saleh There are approximately 20,000-revision total knee ar- throplasties (TKA) performed in North America annu- ally. With a growing number of TKAs being performed and the trend toward a longer life expectancy, failure of the primary TKA is inevitable, thus, revision TKAs are going to be performed at an increasing rate for years to come. A major issue in revision TKA is the degree of bone loss that has occurred. In this article the authors discuss the different classification schemes regarding bone loss and their impact on subsequent treatment modalities. A discussion on assessment of bone loss and the multiple techniques, along with indications for each, that can be employed intraoperatively to account for the bone loss will enable the surgeon to undergo the challenge of bone reconstruction in a stepwise fashion. The article provides advantages and disadvantages to each technique as well as a review of the current liter- ature. Bone deficiency from component removal, oste- olysis, or gap balancing can prove to be a significant problem in revision TKA. With careful planning, appro- priate judgment, and good surgical technique, good results can be achieved. © 2003 Elsevier Inc. All rights reserved. A pproximately 200,000 primary total knee arthroplasties (TKA) and 20,000 revision TKA are performed annually in North America. With a trend towards performing TKA in younger and younger patients, the number of revisions will increase as patients outlive their implants. The failure of the primary implant is often associated with bone loss, a problem that is often compounded when the prosthesis, ce- ment, and membranes are removed at revision surgery. Unfortunately, the degree of bone loss typi- cally exceeds that predicted by the preoperative radiographs. Multiple options exist to fill those bony defects and include cement, autograft bone, allograft bone, modular metal wedges and blocks, and custom designed prostheses. The techniques to address bony defects must not compromise the basic principles of TKA, which include (1) correct limb alignment, (2) correct implant position, (3) flexion and extension gap balancing, (4) joint line restoration, (5) central patellar tracking, (6) adequate range of motion, and (7) ligamentous stability. 1 The purpose of this article is to review the classification of bone loss, as well as the indications, disadvantages, and published clinical results for each reported method of reconstructing bone defects in revi- sion TKA. Classification Classifying bone damage preoperatively helps the surgeon select an appropriate implant for revision. Another benefit is that it may be useful for analyzing clinical results of revision knee arthroplasty surgery. 2 Many classification schemes have been reported in the literature. Bone loss may be classified by size, depth, location, and ability to contain particulate graft or cement. Rand 3 divided bone defects into small, medium, and large sizes. Small de- fects are less than 5 mm deep and less than 50% of the condyle. Medium defects are 5 to 10 mm deep and 50% to 70% of the condyle, and large defects are more than 10 mm deep and more than 70% of the condyle. Defects can also be classified as contained versus un- contained. Contained defects are usually cen- tral and are surrounded by an intact rim of cortical bone, while uncontained defects are usually peripheral and involve a cortical de- fect. Vince divided defects into contained, un- contained, massive, and those extending into the metaphyseal-diaphyseal region (Table 1). 4 However, the most widely used system is prob- ably that proposed by Engh and Ammeen. 2,5 Their Anderson Orthopedic Research Institute From the Department of Orthopaedic Surgery, University of Min- nesota, Minneapolis, MN. Address reprint requests to Khaled J. Saleh, MD, MSc, FRCS(C), Associate Professor, Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Ave. South, R200, Minneapolis, MN 55455. E-mail: saleh002@tc.umn.edu Unrestricted research funding has been received from Stryker Howmedica Osteonics to support this work. © 2003 Elsevier Inc. All rights reserved. 1045-4527/03/1403-0004$30.00/0 doi:10.1053/S1045-4527(03)00050-6 152 Seminars in Arthroplasty, Vol 14, No 3 ( July), 2003: pp 152-158