Pascal‐André Vendittoli MD MSc1, William Blakeney MBBS MSc MS FRACS2, Charles Rivière3, and Gene Dossett4 1 Surgery Department, Université de Montréal, Hôpital Maisonneuve Rosemont, Montreal, QC, Canada 2 Albany Health Campus, Department of Surgery, Albany, Australia 3 The MSK Lab, Charing Cross Campus, Imperial College London, UK 4 Phoenix VA Health Care System, Phoenix, AZ, USA A stable knee with a neutral mechanically aligned lower limb MA has been one of the primary surgical aims of TKA,1 as it provides good long‐term implant survivorship.2 Despite the many improvements in implant design and in the precision of surgery (computer navigation, patient‐specific instrumentation and robotics), MA TKA functional outcomes are disappointing (high rates of dissatisfaction and residual symptoms).3,4 Interest in alternative, more anatomical, surgical techniques like the kinematic alignment (KA) TKA has recently re‐emerged,5 with the hope they would provide better knee kinematics and functional outcomes than MA TKA. At one or two years’ follow‐up, three randomized controlled trials (RCTs)6–8 found better clinical scores (Knee Society Score [KSS] and Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) with KA TKA, while two others found no significant difference.9,10 The KA technique demonstrated quicker recovery (measured by the KSS and WOMAC scores), higher rates of forgotten knee, and lower rates of residual pain.6–8 Five meta‐analyses including the above RCTs have also demonstrated improved functional outcomes according to WOMAC, Oxford Knee Score (OKS), and KSS scales, and increased knee flexion with KA compared to MA.11–15 Another meta‐analysis limiting the analysis to studies including patient‐specific instruments did not find a difference.16 None have found improved outcomes for MA. Mechanical alignment is known to modify knee kinematics and gait.17 A case‐control study demonstrated that MA TKAs displayed several significant knee kinematic differences to a healthy group: less sagittal plane range of motion, decreased maximum flexion, increased adduction angle, and increased external tibial rotation. Conversely, there was no significant knee kinematic differences between KA and healthy knees. The postoperative Knee injury and Osteoarthritis Outcome Score (KOOS) was significantly higher in the KA group compared to the MA group. Similarly, Niki et al. in a matched study of KA and MA TKAs found an increased knee adduction moment in the MA group.18 Another gait study by McNair et al., however, found little difference between KA and MA.19 One of the concerns about performing KA TKA is that it might be associated with an increased risk of early failure and other complications. It is therefore important to assess the evidence regarding complications in KA versus MA TKA. When considering a new technique for surgery, it is important to compare its clinical performance with the current standard of practice. A meta‐analysis of an aggregated 877 kinematic TKAs reported a cumulative survivorship of 97.4% at a weighted mean follow‐up of 37.9 months.12 The most common reasons for revision were patellofemoral problems in eight patients (1.2%). There was no difference reported in the complication rate between 229 KA and 229 MA TKA patients (3.9% vs 4.4%, p = 0.83). A second meta‐analysis had the same findings.11
40 Mechanical versus Kinematic Alignment in Total Knee Arthroplasty
Clinical scenario
Top three questions
Question 1: In patients undergoing TKA, does kinematic alignment provide better functional outcomes than mechanical alignment?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Resolution of clinical scenario
Question 2: In patients undergoing TKA, does kinematic alignment (KA) result in different complications compared to mechanical alignment (MA)
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
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