Association between limb alignment and patient-reported outcomes after total knee arthroplasty using an implant that reproduces anatomical geometry

Nakajima et al. Journal of Orthopaedic Surgery and Research https://doi.org/10.1186/s13018-018-1030-8 (2018) 13:320 RESEARCH ARTICLE Open Access Association between limb alignment and patient-reported outcomes after total knee arthroplasty using an implant that reproduces anatomical geometry Arata Nakajima1*, Masato Sonobe1, Yorikazu Akatsu1, Yasuchika Aoki2,3, Hiroshi Takahashi1, Toru Suguro4 and Koichi Nakagawa1 Abstract Background: A kinematically aligned (KA) total knee arthroplasty (TKA) is expected to improve patient satisfaction, but its effect remains controversial. We investigated differences in patient-reported outcomes (PROs) between KA and non-KA TKAs using an implant that reproduces anatomical geometry. Methods: TKAs for varus deformity were performed in consecutive 129 patients (149 knees) via a measured resection technique with conventional instruments. The femorotibial angle (FTA), hip-knee-ankle angle (HKAA), and the angle between the joint line and the line perpendicular to the mechanical axis (AJLMA) were measured postoperatively (mean 13.6 months), and an AJLMA of ≥ 2° was defined as kinematic alignment. Patients were assigned to two or three alignment categories in each measurement method, and the Knee Society Scores (KSS) and Japanese Knee Injury and Osteoarthritis Outcome Scores (J-KOOS) was compared among the groups. Results: For patients assessed by FTA, an ADL-related J-KOOS subscale (J-KOOS-A) showed a significant difference between valgus and varus outliers (p < 0.05). When assessed by HKAA, neither the KSS nor J-KOOS subscales were significantly different among groups. When assessed by AJLMA, J-KOOS-A was significantly different between groups, and a group for AJLMA of ≥ 2° had higher scores than a group for AJLMA of < 2° (95% CI 0.323–7.763; p < 0.05). Conclusions: Patients with an AJLMA of ≥ 2° reported significantly higher patient’s satisfaction regarding ADL. This suggests the importance of restoration of the physiological joint line which can be achieved via KA TKAs. Keywords: Total knee arthroplasty (TKA), Anatomical geometry, Limb alignment, Kinematic alignment, Patient-reported outcomes (PROs) Background Postoperative restoration of a neutral limb alignment to preserve knee function and longevity has been the primary goal of conventional total knee arthroplasty (TKA) over the past two decades [1, 2]. Conventional TKAs have relieved patients’ symptoms of pain and corrected deformities, resulting in improvements in the activities of daily living (ADL). However, in general, patients’ satisfaction with TKAs is not as favorable as it is for total hip * Correspondence: 1 Department of Orthopaedic Surgery, Toho University Sakura Medical Center, 564-1 Shimoshizu, Sakura-shi, Chiba 285-8741, Japan Full list of author information is available at the end of the article arthroplasties [3–5], generating the need for improved surgical techniques and new technological developments. Recently, kinematically aligned (KA) TKAs were introduced by Bellemans [6]. With KA TKAs, the femoral and tibial components are implanted with mild varus limb alignment, relative to neutral alignment, in order to restore the physiological joint line to a pre-arthritic state. Whether KA TKAs are superior to the mechanically aligned (MA) TKAs based on patients’ postoperative satisfaction has been an ongoing point of debate [7–9]. Furthermore, little information is available in terms of the postoperative association between the limb alignment and patient-reported outcomes (PROs) in KA TKAs. © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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. Nakajima et al. Journal of Orthopaedic Surgery and Research (2018) 13:320 The FINE total knee (Teijin-Nakashima Medical, Okayama, Japan) has unique design features, including a femorotibial joint line with an oblique 3° angle (Fig. 1). This feature enables the implant to reproduce anatomical geometry and allows the osteotomy to be performed perpendicular to the mechanical axis. The FINE total knee is also designed to guide internal movements of the tibia via medial pivotal rotation, thus permitting deeper flexion of the knee to better match the lifestyle needs of Japanese populations [10]. The medial surface of the polyethylene insert has a convex curve which is designed to increase the rate of conformity to the femoral component, thereby enhancing internal rotation of the tibia. Conversely, the lateral surface has a flat surface which has been designed to allow femoral rollback, thereby enhancing internal rotation of the tibia via medial pivotal motion [10]. Hence, the design concepts of FINE total knee facilitate to obtain kinematic alignment via conventional osteotomy performed for MA TKAs. The aim of the present study was to investigate, retrospectively, whether there are differences in the postoperative patient-reported outcomes (PROs) including Knee Society Score (KSS) and Knee Injury and Osteoarthritis Outcome Score (KOOS) in different alignment categories for patients undergoing TKAs using the FINE total knee. We hypothesized that the KSS would be similar among the groups, but that patients with kinematic alignment would have a higher KOOS compared with those without it. Page 2 of 8 Patients and methods Patients A total of consecutive 129 patients (24 males and 105 females) underwent primary TKAs (149 knees) for varus knees resulting from osteoarthritis or rheumatoid arthritis at our institution between August 2013 and January 2016 and were included in this study. The exclusion criteria included valgus deformity, occurrence of fractures in lower limbs receiving TKAs, and deterioration of dementia during the follow-up period. Preoperative patient demographics and knee physical function indicators such as deformities, range of movement (ROM), and KSS are shown in Table 1. Surgical procedures All implants used in this study were FINE total knee, of which 115 were the cruciate-retaining type and 34 were the posterior ligament-substituting type. Surgeries were performed using a measured resection technique and conventional instruments, that is, the distal femoral osteotomy was conducted perpendicular to the mechanical axis and the posterior condyle was osteotomized parallel to the surgical epicondylar axis; a tibial osteotomy was subsequently conducted perpendicular to the anatomical axis of the tibia. Following osteotomy, adjustments for soft tissue balancing were per (...truncated)