The benefits of computer-assisted total knee arthroplasty on coronal alignment with marked femoral bowing in Asian patients

Lee et al. Journal of Orthopaedic Surgery and Research 2014, 9:122 http://www.josr-online.com/content/9/1/122 RESEARCH ARTICLE Open Access The benefits of computer-assisted total knee arthroplasty on coronal alignment with marked femoral bowing in Asian patients Chien-Yin Lee1, Shih-Jie Lin1, Liang-Tseng Kuo1, Kuo-Ti Peng1,2, Kuo-Chin Huang1,2, Tsan-Wen Huang1,2*, Mel S Lee1,2, Robert Wen-Wei Hsu1,2 and Wun-Jer Shen3 Abstract Background: Mechanical alignment guides are designed to compensate for variations in the valgus alignment angle; however, these guides may not be adequate when a patient has coronal alignment with marked bowing deformity. Previous study demonstrates better radiographic results, but the clinical benefits are a matter of speculation. The aim of this study was to investigate whether radiographic benefits of computer-assisted surgery total knee arthroplasty (CAS-TKA) would translate to clinical outcomes. Methods: Patients with osteoarthritis and coronal alignment with marked bowing deformity who underwent total knee arthroplasty (TKA) at our institution between January 2005 and June 2012 were entered into this retrospective study. Patients were divided into three groups: patients with coronal alignment with marked bowing deformity treated with CAS-TKA; with coronal alignment with marked bowing deformity treated with conventional TKA; and without marked coronal bowing deformity treated with conventional TKA. The computer-assisted navigation and the conventional technique were then compared by radiographic parameters. The International Knee Society (IKS) scores and patellar score were obtained for all patients preoperatively and at the last follow-up visit. Results: One hundred and thirty-seven patients (198 knees) met the inclusion criteria. For patients with osteoarthritic knees with marked femoral bowing deformity, the reconstructed mechanical axis (MA) was significantly closer to normal in the CAS-TKA group (P = 0.002) than in the conventional group. Significant differences in the reconstructed MA after conventional TKA were noted between patients without bowing and those with bowing (P = 0.003). Using the patellar score and IKS score, at a mean follow-up of 52.2 months, the differences did not achieve statistical significance among the three groups. Conclusions: CAS-TKA was an effective alternative for obtaining proper alignment in patients with coronal alignment with marked bowing deformity. However, there was no statistically significant difference in clinical function between patients treated with CAS-TKA and conventional TKA. Long-term follow-up will be needed to determine if the improvement in radiographic results translates to better clinical outcomes. Keywords: Bowing deformity of femur, Arthroplasty, Knee, Replacement, Surgery, Computer-assisted * Correspondence: 1 Department of Orthopaedic Surgery, Chang Gung Memorial Hospital, 6, West Section, Chia-Pu Road, Pu-Tz City, Chia-Yi Hsien 613, Taiwan 2 Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan Full list of author information is available at the end of the article © 2014 Lee et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Lee et al. Journal of Orthopaedic Surgery and Research 2014, 9:122 http://www.josr-online.com/content/9/1/122 Introduction Patient factors, prosthetic design, and surgical technique all affect the survivorship of total knee arthroplasty (TKA) [1-6]. Studies using finite element models as well as long-term survival studies confirm that the longevity of the implants and optimal long-term outcomes depend on the accuracy of bone cuts (within 3° from the ideal position) and proper restoration of the mechanical axis of the leg [7-12]. Current mechanical alignment guides for TKA have many limitations. Several authors have reported malaligned components in more than 25% of patients they used an intramedullary alignment system [13-15]. Deformities of the femur, such as the presence of diaphyseal deformity, distortion of the bony canal, and variations in femoral anatomy, are likely to further decrease the accuracy [13-17]. The prevalence of coronal alignment with marked bowing deformity in patients with end-stage osteoarthritis of the knee is particularly relevant in Asian populations because this deformity reportedly affects as many as 62% of Asians [18-20]. Such deformities will alter the desired angle between the mechanical and anatomical axis of the lower extremity and thereby jeopardize positioning of the femoral component and postoperative mechanical axis of the limb [18-22]. Computer-assisted surgery total knee arthroplasty (CAS-TKA) has been shown to improve component alignments and limb axis correction and to lessen gap asymmetry in patients with arthritic knees complicated by extra-articular deformities [23-25]. However, few studies have addressed the benefits of CAS-TKA in patients with coronal alignment with marked bowing deformity [18-21]. In 2011, we published a radiographic study to investigate the impact of marked femoral bowing on the placement of components and postoperative mechanical axis in TKA [6]. A total of 306 knees were compared and demonstrated that marked femoral bowing resulted in inaccuracy of the position of femoral component and limb alignment when a conventional technique was used. However, several limitations in the previous radiological study must be acknowledged. First, patients underwent primary TKA by three surgeons using different prostheses. Secondly, we were unable to assess any correlation between alignment and functional outcome. In order to further clarify the clinical influence of marked coronal femoral bowing and the role of CASTKA, we now report the comparisons of radiographic and clinical outcomes. All patients received the same total knee prosthesis (cruciate-retaining design press-fit condylar sigma fixed-bearing components [DePuy PFC Knee Systems, DePuy Orthopaedics, Warsaw, IN, USA]). All procedures were performed by the senior surgeon (Hsu RWW) who has extensive experience in the use of both conventional mechanical guides and computer- Page 2 of 10 assisted navigation. The strict inclusion criteria for this investigation were designed to limit the variables under study. The purpose was to assess whether the CAS-TKA is more useful than the conventional TKA for patients with coronal alignment with marked bowing deformity. We hypothesize that CAS-TKA provides better clinical outcomes when marked coronal femoral bowing is presented. Methods This retrospe (...truncated)