Knee Surg Relat Res  
The Learning Curve for Biplane Medial Open Wedge High Tibial Osteotomy in 100 Consecutive Cases Assessed Using the Cumulative Summation Method
Do Kyung Lee, MD1, Kwang Kyoun Kim, MD1, Chang Uk Ham, MD1, Seok Tae Yun, MD2, Byung Kag Kim MD3, and Kwang Jun Oh, MD3
1Department of Orthopaedic Surgery, Konyang University Hospital, Konyang University College of Medicine, Daejeon; 2Department of Orthopaedic Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul; 3Department of Orthopaedic Surgery, Joint Center, SungMin Hospital, Incheon, Korea
Correspondence to: Kwang Jun Oh, MD
Department of Orthopaedic Surgery, Joint Center, SungMin Hospital, 70 Sinsuk-ro, Seo-gu, Incheon 22789, Korea
Tel: +82-32-726-1276, Fax: +82-32-726-1109
Received: August 13, 2017; Revised: November 22, 2017; Accepted: December 5, 2017; Published online: April 30, 2018.
© Korean Knee Society. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose: The purpose of this study was to investigate whether surgical experience could improve surgical competency in medial open wedge high tibial osteotomy (MOWHTO).
Materials and Methods: One hundred consecutive cases of MOWHTO were performed with preoperative planning using the Miniaci method. Surgical errors were defined as under- or overcorrection, excessive posterior slope change, or the presence of a lateral hinge fracture. Each of these treatment failures was separately evaluated using the cumulative summation test for learning curve (LC-CUSUM).
Results: The LC-CUSUM showed competency in prevention of undercorrection, excessive posterior slope change, and lateral hinge fracture after 27, 47, and 42 procedures, respectively. However, the LC-CUSUM did not signal achievement of competency in prevention of overcorrection after 100 procedures. Furthermore, the failure rate for overcorrection showed an increasing tendency as surgical experience increased.
Conclusions: Surgical experience may improve the surgeon’s competency in prevention of undercorrection, excessive posterior slope change, and lateral hinge fracture. However, it may not help reduce the incidence of overcorrection even after performance of 100 cases of MOWHTO over a period of 6 years.
Keywords: Knee, Osteoarthritis, Osteotomy, Accuracy, Learning curve


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