| The Surgical Technologist | AUGUST 2022 350 Kostretzis et al. Kinematic Alignment Total Knee Revision INTRODUCTION The number of total knee arthroplasties (TKAs) performed worldwide is constantly increasing as the population is growing and indications for TKAs are widened to include younger patients (1). It has been estimated that revision knee surgeries could increase by 601% in the USA (2), and up to 332% in England and Wales (3), by 2030. Revision TKA procedures are highly complex procedures and have inferior survival rates and poorer functional outcomes than primary arthroplasties (4, 5). Currently, the main reasons for revision include infection, loosening, instability, and pain (6). As TKA implants have improved over the years, rates of aseptic loosening have gradually lowered, and it is now the second main reason for revision (7). Despite the advances in implant technology, patient dissatisfaction has remained relatively high at 15–20% (8). In addition, up to 50% of patients report persisting residual symptoms such as pain, stiffness, and instability (9, 10). Some authors believe that many unsatisfactory outcomes may be due to anatomical changes linked to the mechanical alignment technique (11–13). In primary arthroplasty, kinematic alignment (KA) is proposed as an alternative to MA to minimize these issues. KA has shown equivalent or better functional outcomes and survival rates in the mid-term than MA (14). The logical next step is to apply the principles of KA in revision surgeries. The goal of KA is to restore or preserve the patient’s pre-arthritic knee anatomy by resurfacing the native joint and maintaining the soft tissue envelope (11). As in primary TKA, KA principles could be applied to revision TKA. However, multiple challenges intrinsic to revision surgeries and the MA technique will need to be addressed: bone loss, loss of some anatomical landmarks, soft tissue management, revision implants, and instruments designed for MA. The senior author (PAV) has used restricted KA (rKA, Figure 1) since 2011 when performing primary TKAs, and started using rKA for TKA revision in February 2013. The study objective is to describe the technique used to perform TKA revision using rKA principles and to report early outcomes, including (1) the rerevision rate, (2) patient-reported outcome measures (PROMs) assessed with WOMAC score and, (3) radiological signs of implant dysfunction. The hypotheses for the study were that revision TKA with the use of the rKA protocol would produce favorable outcomes in PROMs, while achieving low (<10%) rerevision rates at early follow-up. MATERIALS AND METHODS Patients All revision TKAs performed by the senior author between February 2013 and November 2020 were retrospectively reviewed Abbreviations: aHKA, Arithmetic hip–knee–ankle angle; BMI, Body mass index; KA, Kinematic alignment; MA, Mechanical alignment; mDFA, Mechanical distal femoral angle; mPTA, Mechanical proximal tibial angle; PROMs, Patient reported outcome measures; PS, Posterior stabilized; RCT, Randomized controlled trial; rKA, Restricted kinematic alignment; TKA, Total knee arthroplasty; TS, Total stabilizer; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index. for inclusion in this study (N =85). The following cases were excluded: revision surgeries for polyethylene liner exchange (4), for patellar resurfacing (2), with associated extra-articular deformities (1), that required long uncemented diaphyseal fixation (major metaphyseal bone loss) (15), that required hinged components (5), and 13 patients who did not want to participate in the study. A total of 42 patients (43 TKAs, one bilateral) gave their consent to participate in the study. There were 12 males and 31 females who had a mean age at the primary surgery of 67.7 years (55–85, ±7.2). Our scientific and ethics review committees approved the study, and all patients consented to include their case. Methods of Assessment A retrospective review of patients’ charts was used to record any rerevisions and adverse events during the follow-up period. Adverse events were recorded using the Knee Society standardized TKA complication list (16). At the last follow-up, a single research assistant assessed patients’ functional outcomes using the WOMAC score (15). The post-revision anteroposterior and lateral radiographs obtained during follow-up visits were evaluated following the modern Knee Society Radiographic Evaluation System (16) to assess radiolucent lines, osteolysis, and signs of component loosening. Radiographic pre- and postrevision coronal orientation measurements were calculated in AP standing long leg x-rays using the mechanical distal femoral angle (mDFA), the mechanical proximal tibial angle (mPTA), and the arithmetic hip-knee-ankle angle (aHKA=mDFA+mPTA). Using digitized image and measurement tools, the same evaluator (LK) performed all measurements. The preoperative rotational alignment of the femoral and tibial components were measured with the use of epicondylar axis and tibial tubercle as references on CT scans as described by Berger and Crossett (17). Statistical Analysis Continuous data are presented using mean, minimum, maximum, and standard deviation. Comparisons of the preoperative and postoperative continuous data were analyzed using a paired Wilcoxon test (pre- and post-revision mDFA, mPTA, aHKA). Categorial variables are presented as numbers and percentages. A significance level of p=0.05 (two-sided) was used for all tests. The analyses were performed using the SPSS software version 26 (SPSS Inc., Chicago, IL, USA). No sample size calculation was done for this study as it is a cohort report with no comparison group. Prosthesis The implant used in all patients for this study was the Triathlon TS Knee System (Stryker Orthopedics, Mahwah, NJ). This prosthesis is a revision system that features a single radius femoral articulating design. Tapered uncemented or cemented femoral and tibial stems are available and come in 50-, 100-, and 150-mm lengths. The stems have a fixed angle of 6◦ of valgus to the femoral component and neutral alignment to the tibial component. 360◦ of stem offset of 2–8 mm for both the femur and the tibia are available. Frontiers in Surgery | www.frontiersin.org 2 August 2021 | Volume 8 | Article 721379
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