Author's personal copy Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-017-4558-y
KNEE
Kinematic alignment is a possible alternative to mechanical alignment in total knee arthroplasty Yong Seuk Lee1,4 · Stephen M. Howell2 · Ye‑Yeon Won3 · O‑Sung Lee1 · Seung Hoon Lee1 · Hamed Vahedi4 · Seow Hui Teo5
Received: 4 October 2016 / Accepted: 19 April 2017 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2017
Abstract Purpose A systematic review was conducted to answer the following questions: (1) Does kinematically aligned (KA) total knee arthroplasty (TKA) achieve clinical outcomes comparable to those of mechanically aligned (MA) TKA? (2) How do the limb, knee, and component alignments differ between KA and MA TKA? (3) How is joint line orientation angle (JLOA) changed from the native knee in KA TKA compared to that in MA TKA? Methods Nine full-text articles in English that reported the clinical and radiological outcomes of KA TKA were included. Five studies had a control group of patients who underwent MA TKA. Data on patient demographics, clinical scores, and radiological results were extracted. There were two level I, one level II, three level III, and three level IV studies. Six of the nine studies used patient-specific
* Stephen M. Howell
[email protected]
Yong Seuk Lee
[email protected];
[email protected]
1
Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 166 Gumi‑ro, Bundang‑gu, Seongnam‑Si, Gyeonggi‑do 463‑707, South Korea
2
8120 Timberlake Way Ste 112, Sacramento, CA 95823, USA
3
Department of Orthopedic Surgery, Ajou University College of Medicine, Suwon, South Korea
4
Rothman Institute at Thomas Jefferson University, Philadelphia, PA, USA
5
Department of Orthopaedic Surgery, National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
instrumentation, one study used computer navigation, and two studies used manual instrumentation. Results The clinical outcomes of KA TKA were comparable or superior to those of MA TKA with a minimum 2-year follow-up. Limb and knee alignment in KA TKA was similar to those in MA TKA, and component alignment showed slightly more varus in the tibial component and slightly more valgus in the femoral component. The JLOA in KA TKA was relatively parallel to the floor compared to that in the native knee and not oblique (medial side up and lateral side down) compared to that in MA TKA. The implant survivorship and complication rate of the KA TKA were similar to those of the MA TKA. Conclusion Similar or better clinical outcomes were produced by using a KA TKA at early-term follow-up and the component alignment differed from that of MA TKA. KA TKA seemed to restore function without catastrophic failure regardless of the alignment category up to midterm follow-up. The JLOA in KA TKA was relatively parallel to the floor similar to the native knee compared to that in MA TKA. The present review of nine published studies suggests that relatively new kinematic alignment is an acceptable and alternative alignment to mechanical alignment, which is better understood. Further validation of these findings requires more randomized clinical trials with longer follow-up. Level of evidence Level II. Keywords Knee · Total knee arthroplasty · Kinematic alignment · Mechanical alignment · Outcome
Introduction The current standard of care in total knee arthroplasty (TKA) is to restore the overall alignment to a neutral
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mechanical axis or slight valgus because it has been suggested that mechanical alignment leads to the longest implant survival, as well as improved function and patient satisfaction [1, 4, 17, 27]. However, an important fraction of the normal population has a constitutional varus, and the restoration of mechanical alignment to neutral in these cases may not be desirable, as it would be unnatural [3]. Mechanical alignment may also have unnatural kinematic consequences because the positioning of the components may change the angle and level of the distal femoral, posterior femoral, and tibial joint lines, and thereby deviate limb alignment from normal [3, 8, 11, 12]. The concept of anatomic restoration has gained interest in the form of kinematic alignment. Kinematic alignment corrects the arthritic deformity to correspond to the constitutional alignment of the patient, restoring the natural femoral–tibial articular surface, alignment, and laxities of the knee [14]. Nevertheless, anatomic restoration of these knees could potentially lead to a MA in varus, which could jeopardize the long-term implant survivorship. Therefore, the surgeon is confronted with a strategic dilemma in patients with constitutional varus [3]. However, patients treated with kinematically aligned (KA) TKA are being reported with favourable results in terms of pain relief, function, flexion, feelings of normality, and implant survivorship, irrespective of the varus alignment of the tibial component [6, 7, 13, 14]. Therefore, the intentional placement of the TKA implant to restore physiologic rather than neutral alignment is controversial [32]. Caution needs to be exercised before modifying the standard of care, and a rigorous assessment of the degree to which KA TKA has been objectively proven is necessary. To that end, we conducted a systematic review to answer the following questions: (1) Does KA TKA achieve clinical outcomes comparable to those of MA TKA? (2) How do the limb, knee, and component alignments differ between KA and MA TKA? (3) How is joint line orientation angle (JLOA) changed from the native knee in KA TKA compared to that in MA TKA?
Materials and methods Search strategy To answer each research question, a literature review was performed with use of the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines [23]. In phase 1 of the PRISMA search process, MEDLINE, EMBASE, and Cochrane database were systematically searched in September 2016 using the following search terms: ((((((patient specific) OR kinematically
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Knee Surg Sports Traumatol Arthrosc
aligned) OR kinematic aligned) OR mechanically aligned) OR mechanical aligned)) AND ((total knee arthroplasty) OR total knee replacement) (“Appendix”). The identified citations were screened, and unpublished articles were also checked with hand searches. The bibliographies of the relevant articles were subsequently cross-checked for articles not identified in the search. In phase 2, abstracts and titles were screened for their relevance. In phase 3, the full text of the selected studies was reviewed to assess for the inclusion criteria and methodological appropriateness with a predetermined question. In phase 4, the studies underwent a systematic review process. Extracted data using a standardized protocol are presented in Table 1. The extracted data were then crosschecked for accuracy, and any disagreement was resolved by the third review author. Eligibility criteria Studies meeting the following criteria were included: (1) articles written in English, (2) full-text availability for the articles, (3) human in vivo studies, (4) reports of TKA using kinematic alignment, and (5) articles that document clinical and/or radiological outcomes. The following studies were excluded: (1) articles written in a language other than English, (2) unavailable full text, (3) experimental studies, (4) clinical studies not reporting clinical and/or radiological outcomes, (5) studies using patient-specific instrumentation (PSI) not considering kinematic alignment, and (6) preliminary report of longer-term studies that were published by the same study group (Fig. 1). Quality assessment and grading of the quality of the evidence The methodological quality of the randomized controlled trials (RCTs) was assessed using risk of bias (ROB), based on the Cochrane handbook, with nine standard criteria. Each criterion was scored as “Yes (low ROB)”, “No (high ROB)”, or “Unclear”. The methodological quality of the non-randomized case–control study was assessed using the Newcastle–Ottawa assessment scale. A study was awarded a maximum of one star for each item within the selection and outcome domains. A maximum of two stars was given for the comparability domain. As suggested by the Effective Practice and Organization of Care (EPOC), the ROB for interrupted time series studies was used to assess case series, which were also scored as “Yes (low ROB)”, “No (high ROB)”, or “Unclear”. In addition to describing the methodological quality of the included studies, evidence was examined using the guidelines of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) working group [2].
I
II
2014 Dossett
2016 Calliess
Level of evidence
I
First author
2016 Young
Year
KA TKA, 100
KA TKA, 44
KA TKA, 49
Cases
Table 1 Demographics of included studies
MA TKA, 100
MA TKA, 44
MA TKA, 50
Controls
67;70
66;66
72;70
39;61, 43;57
41;3, 38;6
24;25, 24;26
Age (years) (case; M; F (case, control) control)
12 months
2 years
24 months
Follow-up
Patient-specific guide using MRI
Patient-specific guide using MRI
Patient-specific guide using MRI
Method (KA)
Exclusion criteria
(1) Primary OA suitable for a cruciate retaining knee replacement, (2) ability to undergo MRI
(1) History of osteotomy, (2) gross deformity (>15o varus or valgus deformity or fixed flexion contracture) that may require the use of stems, wedges, or augments, (3) instability for which the use of constrained implants (1) Previous fracture of the femur or tibia, (2) infection, (3) previous joint replacement or osteotomy involving the knee, (4) medical condition precluding surgery, (5) patients who required bilateral surgery, and (6) not undergo MRI of knee (1) The preopera- (1) BMI > 40, (2) infection, (3) tive varus–valpost-traumatic gus deformOA, (4) bony ity
