Arthroscopic and Computer-Assisted High Tibial Osteotomy Using Standard Total Knee Arthroplasty Navigation Software  Stephen R. Thompson, M.D., M.Ed., F.R.C.S.C., Nazar Zabtia, M.D., F.R.C.S.C., Bradley Weening, M.D., F.R.C.S.C., Paul Zalzal, M.D., F.R.C.S.C.  Arthroscopy Techniques  Volume 2, Issue 2, Pages e161-e166 (May 2013) DOI: 10.1016/j.eats.2013.01.009 Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 1 Preoperative templating for high tibial osteotomy. (A) The mechanical axis from the center of the femoral head to the center of the tibial plafond is drawn. (B) A line from the center of the femoral head (a˙) is extended through the correction point, which is at 62.5% of the tibial plateau width. Another line (ḃ) is drawn from the center of the tibial plafond through the correction point. (C) The image is enlarged. (D) The proposed osteotomy is drawn (line ė). (E) This line is then transposed onto line ḃ and termed line ë. (F) A perpendicular line from line ë is drawn until it intersects line a˙. This distance (l) is the required osteotomy opening size. In this case it measures 12.5 mm. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 2 Operative setup. The navigation system is placed on the contralateral side, along with the arthroscopy tower. The fluoroscopy unit (not shown) is positioned on the ipsilateral side. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 3 Insertion of patient tracker arrays. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 4 Arthroscopic image of pointing device registering center of trochlear sulcus. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 5 Screenshot from navigation software, displaying angular deformity in coronal and sagittal planes. (A, anterior; L, lateral; M, medial; Max, maximum; Min, minimum; P, posterior.) Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 6 Intraoperative radiograph showing guide pin placement and insertion of osteotome. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 7 The Osteotome Wedge Trial is inserted and advanced with the guidance of the navigation software to the desired correction point. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 8 Screenshot from navigation software. The coronal-plane angular deformity has been corrected, but slope has been increased (because flexion has increased). The Osteotome Wedge Trial is inserted more posteriorly to avoid slope correction. (A, anterior; L, lateral; M, medial; Max, maximum; Min, minimum; P, posterior.) Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions

Fig 9 Screenshot from navigation software. As the knee flexes, valgus increases. Arthroscopy Techniques 2013 2, e161-e166DOI: (10.1016/j.eats.2013.01.009) Copyright © 2013 Arthroscopy Association of North America Terms and Conditions