ELSEVIER PII: SOO20-1383(97)00140-X hpry Vol. 29, No. 2, pp. 101-104, 1998 0 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0020-1383/98 $19.00+0.00 Angulated screw placement in the lateral condylar buttress plate for supracondylar femoral fractures Peter T. Simonian, Greg J. Thompson, Will Emley, Richard M. Harrington, Stephen K. Benirschke and Marc F. Swiontkowski Biomechanics Laboratory, Department of Orthopaedics, Harborview Medical Center, University of Washington, Seattle WA, USA Certain supracondylar femoral fractures are not amenable to internal fixation with fixed angle devices. In these instances, the condylar buffress plate is the recommended alternative; however, this is a less rigid device. Because of the decreased rigidity and strength of this device, there is a tendency toward varus angula- tion and malunion. In six fresh-frozen human knee specimens, segmental osteotomies were created to mimic supracondylar femoral fractures. The medial cortex was completely removed to make the fracture unstable to varus deformity. The fracture was fixed with a lateral corrdylar buttress plate using 4.5 mm screws. Each specimen was tested once with all the screws installed perpendicular to the plate, and again with the middle screw, just proximal to the fracture, angled 45 degrees diagonally across the fracture into the subchondral bone of the medial femoral condyle. For the construct with all screws placed perpendicular to the buttress plate, the initial stiffness was 410 N/mm, and after 1000 cycles it was 230 N/mm. With a screw placed diagonally across the fracture site, stiffness increased to 833 N/mm on the first cycle, and 796 N/mm after 1000 cycles. In all specimens with the screws placed perpendicular to the plate, the distal fragment had a permanent uarus deformity after 1000 cycles, under no load, of 0.91 mm. For the diagonal screw condition, the average magni- tude for all six specimens was 0.42 mm. This simple means of screw angulation in the plate strengthened the overall construct to resist the tendency toward varus deformity. The attractive features include the ease of application, and the use of an existing construct. 0 1998 Elsevier Science Ltd. All rights reserved. Injury, Vol. 29, No. 2, 101-104, 1998 Introduction A supracondylar femoral fracture with articular involvement is a serious injury and difficult to treaP. Whenever possible a fixed angle device should be used to decrease the chance of malunion or more specifically the chance of varus deformity before union. Certain fracture patterns do not allow placement of these rigid devices”. In these instances a less rigid construct is a necessary alternative, despite the increased risk of malunion or nonunion. Specifically, the condylar buttress plate is recom- mended when the distal fragment is too small for the insertion of the condylar blade plate or when the fracture lines are in the frontal plane, as in a C3 fracture, in which the blade of the condylar plate would interfere with the lag screws which must be inserted from front to back. Another construct for these difficult fractures uses both lateral and medial plate@; however, this necessitates considerable soft- tissue stripping. Others have augmented fixation with bone cement, especially when bone quality is poor6. In an attempt to resist the potential for varus deformity with the lateral condylar buttress plate, especially when the medial cortical buttress is deficient, screws in the middle of the plate can be angulated toward the dense, subchondral bone of the medial condyle (Figure 1). By this simple means, screw angulation in the plate should strengthen the overall construct to resist the tendency toward varus deformity. The attractive features include the ease of application, and the use of an existing construct. If in fact screw angulation adds significant stability to these unstable fractures, the technique could be used easily with the lateral condylar buttress plate. The purpose of this study is to compare the biochemical properties of lateral condylar buttress plate fixation of unstable supracondylar fractures with screws in the standard perpendicular position versus screw angulation toward the medial condyle in a diagonal position. Materials and methods Six fresh-frozen human knee specimens, from mid-femur to mid-tibia, were obtained from the University of Washington Department of Biological Structure. The average age of the patients from whom specimens were taken was 72 years (range