Robotic-assisted Total Knee Arthroplasty Technology Provides a Repeatable and Reproducible Method of Assessing Soft Tissue Balance.

Soft-tissue balancing is an important factor in primary total knee arthroplasty (TKA), with 30 to 50% of TKA revisions attributed to technical operative factors including soft-tissue balancing. Robotic-assisted TKA (RATKA) offers opportunities for improved soft-tissue balancing methods. This study aimed to evaluate the repeatability and reproducibility of ligamentous laxity assessments during RATKA using a digital tensioner.Three experienced RATKA surgeons assessed preresection and trialing phases of 12 human cadaveric knees with varying degrees of arthritis. Ligamentous laxity was assessed with manual varus and valgus stresses in extension and flexion, with a digital tensioner providing feedback on the change of laxity displacement. Intraclass correlation coefficient (ICC) analyses were used to determine the repeatability within a single surgeon and reproducibility between the three surgeons.The results showed excellent repeatability and reproducibility in ligamentous laxity assessment during RATKA. Surgeons had excellent repeatability for preresection and trialing assessments, with median ICC values representing excellent reproducibility between surgeons. Surgeons were repeatable within 1 or 1.5 mm for preresection and trialing assessments. On average, the variation within a surgeon was 0.33 ± 0.26 mm during preresection and 0.29 ± 0.28 mm during trialing. When comparing surgeons to each other, they were reproducible within an average of 0.69 ± 0.33 mm for preresection and 0.65 ± 0.31 mm for trialing.This study demonstrated the reliability of robotic-assisted soft-tissue balancing techniques, providing control over ligamentous laxity assessments, and potentially leading to better patient outcomes. The digital tensioner used in this study provided excellent repeatability and reproducibility in ligamentous laxity assessment during RATKA, highlighting the potential benefits of incorporating robotics in TKA procedures.

Results of Robotic-Assisted Versus Manual Total Knee Arthroplasty at 2-Year Follow-up.

Robotic-assisted technology has been developed to optimize the consistency and accuracy of bony cuts, implant placements, and knee alignments for total knee arthroplasty (TKA). With recently developed designs, there is a need for the reporting longer than initial patient outcomes. Therefore, the purpose of this study was to compare manual and robotic-assisted TKA at 2-year minimum for: (1) aseptic survivorship; (2) reduced Western Ontario and McMaster Universities Osteoarthritis Index (r-WOMAC) pain, physical function, and total scores; (3) surgical and medical complications; and (4) radiographic assessments for progressive radiolucencies. We compared 80 consecutive cementless robotic-assisted to 80 consecutive cementless manual TKAs. Patient preoperative r-WOMAC and demographics (e.g., age, sex, and body mass index) were not found to be statistically different. Surgical data and medical records were reviewed for aseptic survivorship, medical, and surgical complications. Patients were administered an r-WOMAC survey preoperatively and at 2-year postoperatively. Mean r-WOMAC pain, physical function, and total scores were tabulated and compared using Student's t-tests. Radiographs were reviewed serially throughout patient's postoperative follow-up. A p < 0.05 was considered significant. The aseptic failure rates were 1.25 and 5.0% for the robotic-assisted and manual cohorts, respectively. Patients in the robotic-assisted cohort had significantly improved 2-year postoperative r-WOMAC mean pain (1 ± 2 vs. 2 ± 3 points, p = 0.02), mean physical function (2 ± 3 vs. 4 ± 5 points, p = 0.009), and mean total scores (4 ± 5 vs, 6 ± 7 points, p = 0.009) compared with the manual TKA. Surgical and medical complications were similar in the two cohorts. Only one patient in the manual cohort had progressive radiolucencies on radiographic assessment. Robotic-assisted TKA patients demonstrated improved 2-year postoperative outcomes when compared with manual patients. Further studies could include multiple surgeons and centers to increase the generalizability of these results. The results of this study indicate that patients who undergo robotic-assisted TKA may have improved 2-year postoperative outcomes.

How Does Robotic-Arm Assisted Technology Influence Total Knee Arthroplasty Implant Placement for Surgeons in Fellowship Training?

Implant malalignment during total knee arthroplasty (TKA) may lead to suboptimal postoperative outcomes. Accuracy studies are typically performed with experienced surgeons; however, it is important to study less experienced surgeons when considering teaching hospitals where younger surgeons operate. Therefore, this study assessed whether robotic-arm assisted TKA (RATKA) allowed for more accurate and precise implant position to plan when compared with manual techniques when the surgery is performed by in-training orthopaedic surgical fellows. Two surgeons, currently in their fellowship training and having minimal RATKA experience, performed a total of six manual TKA (MTKA) and six RATKAs on paired cadaver knees. Computed tomography scans were obtained for each knee pre- and postoperatively. These scans were analyzed using a custom autosegmentation and autoregistration process to compare postoperative implant position with the preoperative planned position. Mean system errors and standard deviations were compared between RATKA and MTKA for the femoral component for sagittal, coronal, and axial planes and for the tibial component in the sagittal and coronal planes. A 2-Variance testing was performed using an α = 0.05. Although not statistically significant, RATKA was found to have greater accuracy and precision to plan than MTKA for: femoral axial plane (1.1° ± 1.1° vs. 1.6° ± 1.3°), coronal plane (0.9° ± 0.7° vs. 2.2° ± 1.0°), femoral sagittal plane (1.5° ± 1.3° vs. 3.1° ± 2.1°), tibial coronal plane (0.9° ± 0.5° vs. 1.9° ± 1.3°), and tibial sagittal plane (1.7° ± 2.6° vs. 4.7° ± 4.1°). There were no statistical differences between surgical groups or between the two surgeons performing the cases. With limited RATKA experience, fellows showed increased accuracy and precision to plan for femoral and tibial implant positions. Furthermore, these results were comparable to what has been reported for an experienced surgeon performing RATKA.

Effect of Manual versus Robotic-Assisted Total Knee Arthroplasty on Cervical Spine Static and Dynamic Postures.

This study compared surgeon cervical (C) spine postures and repetitive motions when performing traditional manual total knee arthroplasty (MTKA) versus robotic-assisted TKA (RATKA). Surgeons wore motion trackers on T3 vertebra and the occiput anatomical landmarks to obtain postural and repetitive motion data during MTKA and RATKA performed on cadavers. We assessed (1) flexion-extension at T3 and the occiput anatomical landmarks, (2) range of motion (ROM) as the percentage of time in the flexion-extension angle, (3) repetition rate, defined as the number of the times T3 and the occiput flexion-extension angle exceeded ±10°; and (4) static posture, where T3 or occiput postures exceed 10° for more than 30 seconds. The average T3 flexion-extension angle for MTKA cases was 5-degree larger than for RATKA cases (19 ± 8 vs. 14 ± 8 degrees). The surgeons who performed MTKA cases spent 15% more time in nonneutral C-spine ROM than those who performed RATKA cases (78 ± 25 vs. 63 ± 36%, p < 0.01). The repetition rate at T3 was 4% greater for MTKA than RATKA (14 ± 5 vs. 10 ± 6 reps/min). The percentage of time spent in static T3 posture was 5% greater for overall MTKA cases than for RATKA cases (15 ± 3 vs. 10 ± 3%). In this cadaveric study, we found differences in cervical and thoracic ergonomics between manual and robotic-assisted TKA. Specifically, we found that RATKA may reduce a surgeon's ergonomic strain at both the T3 and occiput locations by reducing the time the surgeon spends in a nonneutral position.

Robotic-Arm Assisted Total Knee Arthroplasty Demonstrated Greater Accuracy and Precision to Plan Compared with Manual Techniques.

This study determined if robotic-arm assisted total knee arthroplasty (RATKA) allows for more accurate and precise bone cuts and component position to plan compared with manual total knee arthroplasty (MTKA). Specifically, we assessed the following: (1) final bone cuts, (2) final component position, and (3) a potential learning curve for RATKA. On six cadaver specimens (12 knees), a MTKA and RATKA were performed on the left and right knees, respectively. Bone-cut and final-component positioning errors relative to preoperative plans were compared. Median errors and standard deviations (SDs) in the sagittal, coronal, and axial planes were compared. Median values of the absolute deviation from plan defined the accuracy to plan. SDs described the precision to plan. RATKA bone cuts were as or more accurate to plan based on nominal median values in 11 out of 12 measurements. RATKA bone cuts were more precise to plan in 8 out of 12 measurements (p ≤ 0.05). RATKA final component positions were as or more accurate to plan based on median values in five out of five measurements. RATKA final component positions were more precise to plan in four out of five measurements (p ≤ 0.05). Stacked error results from all cuts and implant positions for each specimen in procedural order showed that RATKA error was less than MTKA error. Although this study analyzed a small number of cadaver specimens, there were clear differences that separated these two groups. When compared with MTKA, RATKA demonstrated more accurate and precise bone cuts and implant positioning to plan.

Effects of Seating Load Magnitude on Incremental Cyclic Fretting Corrosion in 5°40' Mixed Alloy Modular Taper Junctions.

BACKGROUND: Mechanically assisted crevice corrosion of modular tapers continues to be a concern in total joint arthroplasties. A surgical factor that may affect taper fretting corrosion during cyclic loading is seating load magnitude. In this study, modular head-neck taper junctions were seated, capturing load-displacement, over a range of axially oriented loads, and electrochemical and micromotion data were captured during short-term incremental cyclic fretting corrosion (ICFC) tests. The hypothesis is low seating loads result in greater motion and fretting corrosion in ICFC tests. The effect of assembly load on pull-off force post-ICFC testing was also evaluated. METHODS: The study employed custom-built test fixtures which measured head-neck micromotion and an electrochemical chamber to monitor electrochemical reactions. Head-neck motion measurements were captured using 2 noncontact differential variable reluctance transducers mounted to the head. Seating experiments ranged from 1000 to 8000 N. RESULTS: Significant differences due to seating loads were reported in seating displacement, ICFC subsidence, and fretting current at 4000 N cyclic load. Seating load decreased but did not eliminate currents. Fretting onset load remained fixed (approximately 1200 N) for tapers seated above 2000 N. Fretting subsidence was negligible for seating loads of 4000 N or higher, and increased subsidence was observed below 4000 N. CONCLUSION: This short-term test method evaluated the acute performance of modular implants which were assembled under various loads and demonstrated the link between seating loads, fretting motions, and electrochemical reactions. While increased seating loads reduced fretting corrosion and taper subsidence, it did not prevent fretting corrosion even at 8 kN seating.

Robotic-Arm Assisted Total Knee Arthroplasty Demonstrated Soft Tissue Protection.

INTRODUCTION: While total knee arthroplasty (TKA) procedures have demonstrated clinical success, occasionally intraoperative complications can occur. Collateral or posterior cruciate ligament injury, instability, extensor mechanism disruption, and tibiofemoral or patellofemoral dislocation are among a few of the intraoperatively driven adverse events prevalently ranked by The Knee Society. Robotic-arm assisted TKA (RATKA) provides a surgeon the ability to three-dimensionally plan a TKA and use intraoperative visual, auditory, and tactile feedback to ensure that only the desired bone cuts are made. The potential benefits of soft tissue protection in these surgeries need to be further evaluated. The purpose of this cadaver study was to assess the a) integrity of various knee soft tissue structures (medial collateral ligament [MCL], lateral collateral ligament [LCL], posterior cruciate ligament [PCL], and the patellar ligament), as well as b) the need for tibial subluxation and patellar eversion during RATKA procedures. MATERIALS AND METHODS: Six cadaver knees were prepared using RATKA by a surgeon with no prior clinical robotic experience. These were compared to seven manually performed cases as a control. The mean Kellgren-Lawrence score was 2.8 (range, 0 to 4) in RATKA and 2.6 (range, 1 to 4) in the manual cohort. The presence of soft tissue damage was assessed by having an experienced surgeon perform a visual evaluation and palpation of the PCL, MCL, LCL, and the patellar ligament after the procedures. In addition, leg pose and retraction were documented during all bone resections. The amount of tibial subluxation and patellar eversion was recorded for each case. RESULTS: For all RATKA-assisted cases, there was no visible evidence of disruption of any of the ligaments. All RATKA cases were left with a bone island on the tibial plateau, which protected the PCL. Tibial subluxation and patella eversion were not required for visualization in any RATKA cases. In two of the seven MTKA cases, there was slight disruption noted of the PCL, although this did not lead to any apparent change in the functional integrity of the ligament. All MTKA cases required tibial subluxation and patellar revision to achieve optimal visualization. DISCUSSION: Several aspects of soft tissue protection were noted during the study. During bone resections, the tibia in RATKA procedures did not require subluxation, which may reduce ligament stretching or decrease complication rates. Potential patient benefits for short-term recovery and decreased morbidity to reduce operative complications should be studied in a clinical setting. Since RATKA uses a stereotactic boundary to constrain the sawblade, which is generated based on the implant size, shape, and plan, and does not have the ability to track the patient's soft tissue structures, standard retraction techniques during cutting are recommended. Therefore, the retractor placement and potential for soft tissue protection needs to be further investigated. RATKA has the potential to increase soft tissue protection when compared to manual TKA.