From January 2018 to April 2021, we performed 123 primary TKAs using bi-cruciatestabilised (BCS) TKA (Journey II, Smith & Nephew, Tokyo, Japan) in 110 patients at our institute. Patients with OA and knee varus deformities were included. The exclusion criteria were rheumatoid arthritis, osteonecrosis of the knee, posttraumatic OA, and valgus deformity of the knee. Ultimately, 113 knees (100 patients) were eligible for this study. We performed 55 TKAs (51 patients) using conventional extramedullary systems from January 2018 to December 2019, and 58 TKAs (49 patients) were performed using Navio RA-TKA from January 2020 to April 2021. Therefore, we divided the patients into two groups: the control group and the RA-TKA group. All study participants provided informed consent, andGifu University School of MedicineInstitutionalEthics approved all procedures performed during this study (approval number: 2019-238).The following methods were carried out in accordance with relevant guidelines and regulations.
Extramedullary (EM)-guided TKA was performed in accordance with previously reported procedures [15, 16]. Before the operation, the patients were restrained against the operating table using surgical tape. The centre of the femoral head was marked with a rounded magnetic marker. The knee joint was exposed employing a medial parapatellar approach, and also the anterior and posterior cruciate ligaments were resected. The proximal tibia was cut using an EM guide. After resecting the tibial plateau, the surgeon followed the manufacturer’s instructions regarding the use of the femoral EM guide. After setting the cutting guide sleeve, the EM rod was aligned with the magnetic marker from the Whiteside’s line. After the distal femur was cut, gap balancing was performed to determine the rotation of the femoral component following soft-tissue balancing. The goal of the femoral alignment was 90° to the mechanical axis within the frontal plane and 3° flexion within the sagittal plane to avoid femoral cortex notching. After these procedures, additional osteophytes were removed, especially in the posterior aspect of the medial femoral condyle. The rotation of the tibial component made up our minds using the range-of-movement technique . We then implanted the tibial and femoral components with cement.
Robotic-assisted TKA group
All procedures were performed within the same way as the control group before knee jointexposure. Then, two partially threaded pins were placed into the proximal tibia and distal femur for the tracking arrays of the robot system.The osteophytes were excised, and also the anterior and posterior cruciateligaments were resected before gathering data using the robot. The anatomical landmarks, including the hip centre, were registered in keeping with the manufacturer’s procedure. The femur and tibiamorphologies were determined through mapping of the condylaranatomy bytracingthe surfaces with the probe tomake a virtual 3D model of the knee. Following this, varus and valgus stresses were applied duringthe full range of motion (ROM)to balance the dynamic soft tissue. The robotic systemcreated a graphical gap space through a full ROM. The surgeon can adjust the desired mechanical axis.In this study, we planned the femoral and tibial components to be perpendicular to the mechanical axis. Adjustments ofthe implant size, position, and insert thickness in all planes were adjusted tooptimise soft tissue balance and component tracking beforebone preparation. After planning the component, a high-speed 5-mm burr was wont to cut the distalfemur bone. This drill burr continuously moved the handpiece and switched on and offbecause the motorised burr moved in and out of the mapped cuttingarea. The pin holes for the proximal tibia saw guides were preparedwith a 5-mm burr for the proximal tibia and a 2-mmburr for the distal femur. The saw guides were then fixedin an optimal position tomake bone cuts of the proximal tibia and anterior andposterior femur.After placing the trial components, balancing and componenttracking were checked with varus and valgusstress during full ROManda graphical representationof gap spacing.We then implanted the tibial and femoral components with cement.
The postoperative pain intensity was recorded by physical therapists employing a 100-mm visual analogue scale (VAS; where 0=no pain and 100=worst imaginable pain) at rest (rVAS) and during movement (mVAS) preoperatively and on postoperative days (PODs)3, 7, 10, and 14. They also evaluated lower extremity functional recovery by quadriceps muscle strength and therefore the knee’s ROM.Adynamometer (Isoforce, OG GIKENCo., Ltd., Okayama, Japan) was accustomedto measure the manual muscle strength (MS)preoperatively and on PODs3, 7, 10, and 14 in a very manner the same as manual muscle testing. The ROM was measured using a goniometer. Preoperative MSand ROM were considered as 100%, and the postoperative topreoperative MS ratio was calculated.
We further examined the femoral circumference at 10cm above the superior margin of the patellae to evaluate soft tissue swelling. Preoperative femoral circumference was considered to be 100%, and also the ratio of the postoperative to the preoperative circumference was calculated.
All patients received oral celecoxib,200mg every 8h, for 14days postoperatively. Intravenous or oral acetaminophen was provided if patients required additional analgesic drugs for postoperative pain.The number of rescue drugs administered for pain was recorded on PODs14.
Preoperative and postoperative radiological assessments included anteroposterior views of the full-length lower extremities. We assessed the preoperative femorotibial angle (FTA) and postoperative implant coronal alignment, including the varus-valgus (α and β) angles of the femoral and tibial components [15, 16]. In this BCS TKA, the femoral component had a 3° physiological line against the mechanical axis. Therefore, an α angle of 93° was perpendicular to the mechanical axis.
A sample size calculation was performedusing the primary outcome measure of quadriceps muscle strength during the 14-day postoperative period , and28 patients in eacharm were required. All parameters are reported as mean ± standard deviation. Differences between the groups were compared using Student’s t-test or the Wilcoxon rank-sum test. These statistical analyses were performed using GraphPad Prism software (version 5.0; GraphPad Software, Inc., San Diego, CA, USA). Statistical significance was set at P <0.05.