Increased accuracy in component positioning using an image-less robotic arm system in primary total knee arthroplasty: a retrospective study.

BACKGROUND: Robotic-assisted total knee arthroplasty (RTKA) and navigated total knee arthroplasty (NTKA) have shown improved knee alignment and reduced radiographic outliers. Recent studies have proven that conventional mechanical alignment may not be the optimal goal for every patient. The aim of this study was to compare the accuracy of the planned implant positioning of a novel image-less robotic technique with an established navigated technique (NTKA). METHOD: The study is a retrospective analysis of prospectively collected data that compared the implant positioning and lower-limb alignment of 86 image-less RTKA with 86 image-less NTKA. Radiographic analysis was performed to evaluate the lower-limb overall alignment, femoral and tibial components positioning in the coronal and sagittal planes. Outliers were evaluated with a cutoff of ± 3°. RESULTS: No difference was noted between the two groups for radiographic outliers within ± 3° from neutral (p = 0.098). The mean hip-knee-ankle angle deviation from target was 1.3° in the RTKA group compared to 1.9° in the NTKA (p < 0.001). Femoral sagittal deviation (femoral component flexion) was smaller in the RTKA group (0.9° vs 1.9°; p < 0.001). Similarly, tibial coronal deviation (0.8° vs 1.5°; p < 0.001) and tibial sagittal deviation (tibial slope) were smaller in the RTKA group compared to the NTKA group (0.9° vs 1.7°; p < 0.001). CONCLUSIONS: The RTKA group reported a substantial and significant reduced error from the planned target angles for both tibial and femoral components. No difference in terms of radiographic outliers was noted between navigation and robotic assistance.

NAVIO RATKA shows similar rates of hemoglobin-drop, adverse events, readmission and early revision vs conventional TKA: a single centre retrospective cohort study.

PURPOSE: Despite widespread adoption of NAVIO robotic-assisted total knee arthroplasty (NAVIO RATKA) in clinical practice, clinical outcome in terms of adverse events and complications remains unclear. The purpose of this study was to compare adverse events, length of stay, surgical time, hemoglobin drop, early readmission rate and revision rate between conventional TKA (CTKA) and NAVIO RATKA. METHODS: This single-centre retrospective cohort analysis compared 230 NAVIO RATKA patients to 489 CTKA patients with a minimal follow-up of 12 months. Baseline demographic and comorbidity parameters were collected, as well as length of stay, revision rate and reason for revision, early readmission rate (< 6w) and reason for readmission, post-operative hemoglobin levels, adverse events, surgical time and operating room time. Data were compared using Mann-Whitney U test for continuous data without normal distribution and ordinal data, categorical variables were compared using the Chi-square or Fisher exact test. RESULTS: There were no clinically relevant baseline demographic or comorbidity differences between groups. CTKA had shorter length of stay than NAVIO RATKA (5.0 days vs 5.4 days, p = 0.010) but trended towards a higher reoperation rate (4.1% vs 1.7%, p = .144, n.s). No differences were found in hemoglobin drop, readmission rate or overall incidence of adverse events, but CTKA showed more hematoma formation (1.6% vs 0%, p = .044) and higher incidence of periprosthetic joint infection (PJI) (1% vs 0%, p = n.s.), whilst NAVIO RATKA showed more periprosthetic fractures and persistent wound drainage (0.4% vs 2.2%, p = .038 and 0.6% vs 4.3%, p = .001, respectively). Surgical time remained significantly longer in NAVIO RATKA during all 230 cases (87 min vs 67.6 min) and showed a continuous downward trend. CONCLUSIONS: This study further validates the usage of NAVIO RATKA as a safe method to perform TKA, with comparable short term outcomes to CTKA in terms of early revisions and adverse events. Surgeons should be mindful of the differing adverse event profile in NAVIO RATKA and adjust their patient selection accordingly to ensure optimal outcomes. In addition, surgeons using NAVIO RATKA should expect a linear learning curve and a surgical time exceeding that of CTKA. LEVEL OF EVIDENCE: Level III (therapeutic retrospective cohort study).

A comparison of robotic-assisted and manual techniques in restricted kinematically aligned total knee arthroplasty: coronal alignment improvement with no significant clinical differences.

PURPOSE: The purpose of this study was to compare radiographic and clinical outcomes of robotic-assisted and conventional manual techniques in restricted kinematically aligned TKA. METHODS: Patients who underwent either manual or robotic-assisted restricted kinematically aligned TKA between 2019 and 2020 were included in this retrospective comparative study. Radiographic outcomes comprised coronal plane measurements performed through standing full-length anteroposterior radiographs. The Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford score, Visual Analog Scale pain and satisfaction score, and Forgotten Joint Score were used to determine the clinical outcome. The continuous data were compared by Student's t test according to the Kolmogorov‒Smirnov normality test. RESULTS: The manual group consisted of 46 patients (38 females, eight males) with a mean age of 68.1 years, and the robotic group consisted of 70 patients (58 females, 12 males) with a mean age of 65.7 years (n.s.). Preoperatively, no significant difference was observed between groups concerning demographic characteristics, radiographic measurements, and clinical scores except for the symptom and pain domains of the KOOS score, which was significantly worse in the manual group (p = 0.011 and 0.035, respectively). At the postoperative 2-year follow-up, we observed significant differences between groups with respect to the mean HKA angle, mMPTA, and mLDFA (p = 0.034, 0.041, and 0.005, respectively). A comparison of clinical scores at the postoperative 2-year follow-up demonstrated no significant differences between groups. CONCLUSION: The current study demonstrated that using robotic-assisted technique for restricted kinematically aligned total knee arthroplasty (TKA) resulted in significantly better outcomes compared to the conventional manual technique in achieving normal ranges of lower extremity coronal alignment measurements. While the robotic-assisted group demonstrated better clinical scores, there was no statistically significant difference in clinical outcomes between the robotic-assisted group and the control group at the two-year follow-up. Concerning clinical relevance, the restoration of original anatomy and coronal alignment, a crucial concern in restricted kinematically aligned TKA, may be better achieved by the robotic-assisted technique. LEVEL OF EVIDENCE: Level III (Retrospective cohort study).

Functional alignment achieves a more balanced total knee arthroplasty than either mechanical alignment or kinematic alignment prior to soft tissue releases.

PURPOSE: Total knee arthroplasty with functional alignment uses pre-resection balancing to determine component position within the soft tissue envelope to achieve balance and restoration of native joint obliquity. The purpose of this study was to assess the balance achievable with a mechanical axis alignment and kinematic axis alignment plan, and the subsequent balance achievable after adjustment of the component position to functional alignment. METHODS: A prospective cohort of 300 knees undergoing cruciate retaining total knee arthroplasty were included in this study. Of these, 130 were initially planned with mechanical alignment (MA) and 170 with kinematic alignment (KA). Maximal stressed virtual gaps were collected using an optical tracking software system. The gaps were measured medially and laterally in flexion and extension. Following assessment of balance, implant position was adjusted to balance the soft tissues in functional alignment (FA) and the maximal gaps reassessed. Gaps were considered to be balanced when within 2 mm of equality. Incidence of balance within each cohort was compared to independent samples proportions test. RESULTS: Functional alignment obtained significantly better balance in extension, medially and overall than both MA and KA alignment without soft tissue release (p < 0.001). Overall balance was observed in 97% of FA knees, 73% of KA knees and in 55% of MA knees. The difference between KA and MA was also significant (p = 0.002). Whilst there was no difference observed in balanced achieved or limb alignment when FA was planned with either MA or KA, the joint line obliquity was maintained with an initial KA plan. CONCLUSION: Functional alignment more consistently achieves a balanced total knee arthroplasty than either mechanical alignment or kinematic alignment prior to undertaking soft tissue release. Utilising an individualised KA plan allows FA to best achieve the stated goals of maintaining joint line plane and obliquity. LEVEL OF EVIDENCE: Level III: retrospective cohort study.

The Impact of Robotic-Assisted Total Knee Arthroplasty on Resident Training.

BACKGROUND: As robotic-assisted total knee replacement (rTKA) continues to gain popularity, the impact of this technology on resident education remains unknown. The purpose of this study was to describe trainee experience and perceptions of rTKA and its effect on surgical training. METHODS: Two hundred and twenty two senior orthopaedic residents attending a national board review course completed a 17-question survey regarding their experience and perceptions regarding rTKA. Mean and standard deviations were calculated for Likert scale questions, and bivariate analyses were utilized to compare answer groups. RESULTS: Seventy percent of respondents reported exposure to rTKA during their training. Of those with robotic exposure, 20% reported that greater than half of their TKA experience involved robotics. Only 29% percent agreed that robotics improved outcomes, whereas 21% disagreed and the remainder were unsure. Over half of respondents agreed that robotics are used primarily for marketing purposes. Of those who trained with rTKA, 45% percent believed that robotics improved their understanding of the surgical procedure; however, 25% felt robotics negatively compromised their training with traditional instrumentation. Higher robotic case exposure (P = .001) and attending an industry-sponsored course (P = .02) was associated with the belief that robotics improved outcomes. Robotic case volume and percentage was associated with the belief that robotics improved understanding of the surgical procedure, however, it also was associated with reduced comfort performing traditional knee arthroplasty (P = .001). CONCLUSION: Current resident training experience varies greatly within the United States with regards to rTKA. While exposure to rTKA may be beneficial for a well-rounded surgical education, over-exposure likely results in decreased comfort with traditional instrumentation.

Variation in knee balance as a function of hip-knee-ankle angle and joint line obliquity in robotic assisted total knee arthroplasty.

PURPOSE: To describe the mediolateral (ML) gap balance in pre-resection arthritic knees undergoing robot-assisted (RA) total knee arthroplasty (TKA) within the nine phenotypes of the Coronal Plane Alignment of the Knee (CPAK) classification. METHODS: A total of 1124 RA TKA cases were retrospectively reviewed. ML balance was calculated using a digital ligament tensioning device following tibial resection and prior to any femoral resection throughout flexion (10°, 40°, and 90°). Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were landmarked intra-operatively and adjusted for wear based on hip-knee-ankle angle (HKA). Knees were then subdivided into CPAK categories based on the arithmetic HKA (aHKA) and joint line obliquity (JLO). Differences in balance between CPAK phenotypes were compared. RESULTS: For aHKA, a greater medial gap was observed in varus compared to neutral or valgus knees at 10° (5.2 ± 3.0 mm vs 3.3 ± 3.2 mm vs - 0.4 ± 5.0 mm respectively; p < 0.0001). A similar trend was observed for JLO in distal apex compared to neutral and proximal apex knees at 10° (3.4 ± 3.6 vs 1.1 ± 5.0 vs - 2.4 ± 6.3 respectively; p < 0.0001). The greatest ML balance differences were found when combining JLO and aHKA at 10° (type I vs type VI: ∆6.6 mm; p < 0.0001). CONCLUSION: There is a high degree of variability in arthritic ML balance within and between each CPAK phenotype. A single alignment philosophy based on bony landmarks alone may not be sufficient to balance all knees. Utilisation of robotics and digital ligament tensioning devices serves as important adjuncts to characterize the patient-specific soft tissue profile.

A new robotically assisted technique can improve outcomes of total knee arthroplasty comparing to an imageless navigation system.

BACKGROUND: Robotic assisted total knee arthroplasty (RTKA) has shown improved knee alignment and reduced radiographic outliers. However, there remains debate on functional outcomes and patient-reported outcomes (PROMs). This study compares the 1-year clinical outcomes of a new imageless robotically assisted technique (ROSA Knee System, Zimmer Biomet, Warsaw, IN) with an imageless navigated procedure (NTKA, iAssist Knee, Zimmer, Warsaw, IN). METHODS: The study is a retrospective analysis of prospectively collected data that compared the functional outcomes and PROMs of 50 imageless RTKA with 47 imageless NTKA at 1-year follow-up. Baseline characteristics, intraoperative and postoperative information were collected including complications, revisions, Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS) score, and Forgotten Joint Score (FJS-12). Radiographic analysis of preoperative and postoperative images evaluating hip-knee-ankle (HKA) angle was performed. RESULTS: There was no difference regarding baseline characteristics between the groups. Mean operative time was significantly longer in the RTKA group (122 min vs. 97 min; p < 0.0001). Significant differences were reported for the "Pain" (85 [RTKA] vs 79.1 [NTKA]; p = 0.0283) subsection of the KOOS score. In addition, RTKA was associated with higher maximum range of motion (119.4° vs. 107.1°; p < 0.0001) and better mean improvement of the arc of motion by 11.67° (23.02° vs. 11.36°; p < 0.0001). No significant differences were noted for other subsections of KOOS, KSS, FJS-12, complications, or limb alignment at 1-year follow-up. CONCLUSIONS: Imageless RTKA was associated with longer surgical time, better pain perception and improved ROM at 12-month follow-up compared with NTKA. No significant differences were reported on other PROMs, complication rates and radiographic outcomes. LEVEL OF EVIDENCE: III.

Reverse coronal deformity: use of robotic total knee arthroplasty for identification and correction.

BACKGROUND: Despite continued advances in techniques and implant designs, a population of patients who are dissatisfied after total knee arthroplasty (TKA) remains. During robotic-assisted arthroplasty, real-time intraoperative assessment of patient knee alignment is performed. Here, we assess the prevalence of an under-appreciated deformity, reverse coronal deformity (RCD), and the benefits of utilizing robotic-assisted knee arthroplasty to help correct this dynamic deformity. METHODS: A retrospective study evaluating patients undergoing robotic-assisted cruciate-retaining TKA was performed. Intraoperative measurements were obtained using tibial and femoral arrays to assess coronal plane deformity at full extension and at 90° flexion. RCD was defined as ≥ 2° varus in knee extension that reversed to ≥ 2° valgus in flexion, or vice-versa. Coronal plane deformity was then reassessed after robotic-assisted bony resection and implant placement. RESULTS: Of 204 patients that underwent TKA, 16 patients (7.8%) were found to have RCD, with 14 patients (87.5%) transitioning from varus in extension to valgus in flexion. The average coronal deformity was 7.75°, with a maximum of 12°. These improved to an average coronal change of 0.93° post-TKA. Final medial and lateral gaps were all balanced to within 1° in extension and flexion. Another 34 patients (16.7%) had ≥ 5° change in coronal plane deformity from extension to flexion (average 6.39°), however, did not experience a reversal of their coronal deformity. Outcomes were assessed with KOOS Jr. scores postoperatively. CONCLUSION: Computer and robotic assistance were utilized to demonstrate the prevalence of RCD. We also demonstrated accurate identification and successfully balancing of RCD utilizing robotic-assisted TKA. An increased awareness of these dynamic deformities could aid surgeons in proper gap balancing even in the absence of navigation and robotic-assisted surgery.

Imageless robotic-assisted total knee arthroplasty leads to similar 24-month WOMAC scores as compared to conventional total knee arthroplasty: a retrospective cohort study.

PURPOSE: Robotic-assisted total knee arthroplasty (RA-TKA) was introduced to improve limb alignment, component positioning, soft-tissue balance and to minimize surgical outliers. This study investigates perioperative outcomes, complications, and early patient-reported outcome measures (PROMs) of one imageless RA-TKA system compared to conventional method TKA (CM-TKA) at 24-month follow-up. METHODS: This multi-surgeon retrospective cohort analysis compared 111 imageless RA-TKA patients to 110 CM-TKA patients (n = 221). Basic demographic information, intraoperative and postoperative data, and PROMs, including the functional score of the Knee Society Score (KSS-FS), The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Short Form 12 Mental and Physical scores (SF-12M and P), were collected and recorded preoperatively, at 3-, 12- and 24-months postoperatively. Range of motion (ROM), estimated blood loss (EBL), surgical duration, and complications were also collected. RESULTS: There were no baseline patient demographic differences between groups. EBL (240 vs. 190 mL, p < 0.001) and surgical duration (123 vs. 107 min, p < 0.001) were significantly greater in RA-TKA. There were no significant differences in postoperative complications, ROM, length of stay (LOS), and PROMs between cohorts at 3-, 12-, 24-months postoperatively. CONCLUSIONS: Imageless RA-TKA is associated with greater EBL and surgical duration compared to CM-TKA. However, at 24-month follow-up, there were no significant differences in ROM, LOS, complications and PROMs between cohorts. Imageless robotic surgery leads to similar 24-month clinical outcomes as compared to CM-TKA. LEVEL OF EVIDENCE: III.

A cautionary case: osteoporotic femur fracture after robotic-assisted total knee arthroplasty.

Osteoporosis is a disease of low bone mass which leads to an increased risk of fracture. The prevalence of osteoporosis is greatest amongst postmenopausal women who also form a large portion of patients with osteoarthritis presenting for total knee arthroplasty. We present a case of a 77-year-old female with knee osteoarthritis and osteoporosis on denosumab who underwent robotic-assisted total knee arthroplasty. Postoperatively, she suffered an atraumatic midshaft femur fracture at the pin site associated with the use of intraoperative robotic technology. This is a unique complication related to the use of robotics which requires additional skeletal fixation versus standard arthroplasty surgical technique. We recommend caution and further study regarding the use of robotics in total knee arthroplasty in the setting of osteoporosis and denosumab use.

Imageless robotic-assisted total knee arthroplasty accurately restores the radiological alignment with a short learning curve: a randomized controlled trial.

PURPOSE: The study compared a novel imageless robotic-assisted total knee arthroplasty (RATKA) and conventional TKA by considering (1) radiological outcomes, (2) outliers of radiological outcomes, and (3) learning curve. METHODS: This prospective randomized controlled study performed by a single surgeon evaluated 152 patients (152 knees): 75 patients undergoing RATKA and 77 patients undergoing conventional TKA. Mechanical alignment, radiological implant positioning, and outliers were analyzed for radiological outcomes. Cumulative summation (CUSUM) analysis was used to assess the learning curve for operative time in RATKA. RESULTS: The RATKA had significantly better accuracy of knee alignment and component positioning than conventional TKA. The hip-knee-ankle axis and implant position outliers were significantly lower in the RATKA, with 94.7% of patients had achieved an overall mechanical alignment within 3° of a neutral mechanical axis. Changes in posterior condylar offset and joint line were significantly lower in the RATKA. A learning curve of seven cases for operative time was obtained for the RATKA. CONCLUSION: The imageless RATKA has better alignment accuracy with a short learning curve; thus, it presents an attractive option for TKA.

Robotic-assisted total knee arthroplasty may lead to improvement in quality-of-life measures: a 2-year follow-up of a prospective randomized trial.

PURPOSE: Despite reduction in radiological outliers in previous randomized trials comparing robotic-assisted versus conventional total knee arthroplasty (TKA), no differences in short-term functional outcomes were observed. The aim of this study was to determine whether there was improvement in functional outcomes and quality-of-life (QoL) measures between robotic-assisted and conventional TKA. METHODS: All 60 knees (31 robotic-assisted; 29 conventional) from a previous randomized trial were available for analysis. Differences in range of motion, Knee Society (KSS) knee and function scores, Oxford Knee scores (OKS), SF-36 subscale and summative (physical PCS/mental component scores MCS) were analysed. In addition, patient satisfaction, fulfilment of expectations and the proportion attaining a minimum clinically important difference (MCID) in KSS, OKS and SF-36 were studied. RESULTS: Both robotic-assisted and conventional TKA displayed significant improvements in majority of the functional outcome scores at 2 years. Despite having a higher rate of complications, the robotic-assisted group displayed a trend towards higher scores in SF-36 QoL measures, with significant differences in SF-36 vitality (p = 0.03), role emotional (p = 0.02) and a larger proportion of patients achieving SF-36 vitality MCID (48.4 vs 13.8 %, p = 0.009). No significant differences in KSS, OKS or satisfaction/expectation rates were noted. CONCLUSION: Subtle improvements in patient QoL measures were observed in robotic-assisted TKA when compared to conventional TKA. This finding suggests that QoL measures may be more sensitive and clinically important than surgeon-driven objective scores in detecting subtle functional improvements in robotic-assisted TKA patients. LEVEL OF EVIDENCE: II.

Computed tomography radiomics in predicting patient satisfaction after robotic-assisted total knee arthroplasty.

PURPOSE: After robotic-assisted total knee arthroplasty (RA-TKA) surgery, some patients still experience joint discomfort. We aimed to establish an effective machine learning model that integrates radiomic features extracted from computed tomography (CT) scans and relevant clinical information to predict patient satisfaction three months postoperatively following RA-TKA. MATERIALS AND METHODS: After careful selection, data from 142 patients were randomly divided into a training set (n = 99) and a test set (n = 43), approximately in a 7:3 ratio. A total of 1329 radiomic features were extracted from the regions of interest delineated in CT scans. The features were standardized using normalization algorithms, and the least absolute shrinkage and selection operator regression model was employed to select radiomic features with ICC > 0.75 and P < 0.05, generating the Rad-score as feature markers. Univariate and multivariate logistic regression was then used to screen clinical information (age, body mass index, operation time, gender, surgical side, comorbidities, preoperative KSS score, preoperative range of motion (ROM), preoperative and postoperative HKA angle, preoperative and postoperative VAS score) as potential predictive factors. The satisfaction scale ≥ 20 indicates patient satisfaction. Finally, three prediction models were established, focusing on radiomic features, clinical features, and their fusion. Model performance was evaluated using Receiver Operating Characteristic curves and decision curve analysis. RESULTS: In the training set, the area under the curve (AUC) of the clinical model was 0.793 (95% CI 0.681-0.906), the radiomic model was 0.854 (95% CI 0.743-0.964), and the combined radiomic-clinical model was 0.899 (95% CI 0.804-0.995). In the test set, the AUC of the clinical model was 0.908 (95% CI 0.814-1.000), the radiomic model was 0.709 (95% CI 0.541-0.878), and the combined radiomic-clinical model was 0.928 (95% CI 0.842-1.000). The AUC of the radiomic-clinical model was significantly higher than the other two models. The decision curve analysis indicated its clinical application value. CONCLUSION: We developed a radiomic-based nomogram model using CT imaging to predict the satisfaction of RA-TKA patients at 3 months postoperatively. This model integrated clinical and radiomic features and demonstrated good predictive performance and excellent clinical application potential.

Predictive factors for deep medial collateral ligament release in adjusted mechanical alignment total knee arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) demands precision in achieving optimal alignment and soft tissue balance, especially in cases of medial compartment osteoarthritis where the need for medial soft tissue release is critical yet challenging to ascertain. OBJECTIVE: This study aims to systematically investigate the relationship between preoperative data, initial knee conditions and the necessity for deep collateral ligament (MCL) release in adjusted mechanical alignment total knee arthroplasty. METHODS: We conducted a retrospective study involving 61 TKA patients who underwent adjusted mechanical alignment robotic-assisted procedures. Soft tissue release was carried out when clinically indicated. We collected and statistically analyzed patient demographics, initial knee conditions, and surgical details. RESULTS: Among the patients, 52% required deep MCL release. Notably, patients without soft tissue release exhibited lower initial hip-knee-ankle (HKA) angles, reduced varus-valgus stress test angles, and a greater range of flexion. We identified a predictive threshold HKA angle of 6.250 degrees, demonstrating high sensitivity and specificity for determining the need for deep MCL release. CONCLUSION: This study underscores the significance of the initial HKA angle and varus-valgus stress tests in predicting deep MCL release during TKA. The established HKA angle threshold simplifies surgical decision-making, reducing the likelihood of unnecessary soft tissue release.

Is 80% satisfaction still the expectation in modern TKA mechanically aligned with robot assist? We think not.

Several studies reported that20% of patients were unhappy with the outcome of their total knee arthroplasty (TKA). Having commenced robot assist TKA whilst maintaining the goal of implanting the prosthesis to a neutral mechanical axis, we reviewed our patients to find out if we also have a 20% rate of patients being unhappy with the outcome of their knee replacement surgery. We hypothesized that rate of patient satisfaction would be higher than 90% with robot-surgical assistant (ROSA) technique. The first 175 patients who underwent ROSA TKA were reviewed at a minimum of 1 year postoperatively. All TKAs were performed using ROSA technique with Persona cementless prosthesis aiming to restore neutral mechanical coronal alignment with flexion gap balancing. We investigated whether or not the patients were happy they had their knee replacement surgery and whether they were happy with the outcome. 165 (94%) of 175 patients, were contactable with 1 deceased and 9 uncontactable. From the 165 patients who participated in the study, 95% of patients were happy they had the surgery done and 93% were happy with the outcome of their knee replacement. A sub analysis showed that patients who had simultaneous bilateral TKA were significantly less likely to be happy than staged procedures (p < 0.05). Total knee replacement utilising robot technique with modern implants and aiming for mechanical coronal alignment of the implants to restore the mechanical axis with flexion gap balancing may result in > 90% of patients being happy with the outcome of their surgery.

Analysis of robot-specific operative time and surgical team anxiety level and its effect on alignment during robot-assisted TKA.

Adapting to robotic-assisted (RA) total knee arthroplasty (TKA) is hindered by the surgeon's fear of extra time. The main purpose of this study was to determine the robot's operative time, and the secondary goals were to assess the surgical team's anxiety, implant location and size, and limb alignment. From February to April 2022, 40 participants participated in prospective research. The study included primary Cuvis joint active RA-TKA patients for end-stage arthritis, but conversion of unicompartmental knee arthroplasty to TKA, and patients with prior knee surgery were excluded. The active RA-TKA surgical time included surgeon-dependent and surgeon-independent/active robot time. The surgeon's anxiety was measured using the state-trait anxiety inventory (STAI). The implant size/position and limb alignment were checked by post-operative weight-bearing lateral, anteroposterior, and full-length scanograms. Operative time specifically related to active RA-TKA was higher in the first 10 cases as against 10-20, 20-30 and 30-40 cases which was observed to lower from cohort 2. A similar trend was observed for the surgical team's anxiety levels which seem to lower from cohort 2 (case 10-20). Cumulative experience of active RA-TKA showed no effect on the precision of implant alignment/ size, limb alignment and complications. The study showed progressive improvement in the surgical anxiety scores and reduction in operating time indicating the proficiency gained by the surgical team. Further no learning curve was involved in achieving the implant positioning and sizing, limb alignment with the absence of complications.

Kinematic Alignment Achieves a More Balanced Total Knee Arthroplasty Than Mechanical Alignment among CPAK Type I Patients: A Simulation Study.

Background: There is no consensus on whether mechanical alignment (MA) or kinematic alignment (KA) should be chosen for total knee arthroplasty (TKA) for coronal plane alignment of the knee (CPAK) Type I with a varus arithmetic HKA (aHKA) and apex distal joint line obliquity (JLO). The aim of this study was to investigate whether MA or KA is preferable for soft tissue balancing in TKA for this phenotype. Method: This prospective cohort study included 64 knees with CPAK Type I osteoarthritis that had undergone cruciate-retaining TKA. Using optical tracking software, we simulated implant placement in the Mako system before making the actual bone cut and compared the results between MA and KA. Extension balance (the difference between medial and lateral gaps in extension) and medial balance (the difference in medial gaps in flexion and extension) were examined. These gap differences within 2 mm were defined as good balance. Achievement of overall balance was defined as an attainment of good extension and medial balance. The incidence of balance in each patient was compared with an independent sample ratio test. Results: Compared with the MA group, the KA group achieved better soft tissue balance in extension balance (p < 0.001). A total of 75% of the patients in the KA group achieved overall balance, which was greater than the 38% achieved in the MA group (p < 0.001). Conclusions: In robot-assisted TKA for CPAK Type I osteoarthritis, KA achieved knee balance during extension without soft tissue release in a greater percentage of patients than MA.

Surgeon-Applied Stress and a Ligament Tensor Instrument Provide a Similar Assessment of Preresection Flexion Laxity During Robotic Total Knee Arthroplasty.

Background: Robotic-assisted total knee arthroplasty (RA-TKA) allows surgeons to perform intraoperative soft tissue laxity assessments prior to bone resections and is used to alter resections to achieve gap balance. This study compared 2 techniques for flexion gap laxity assessment during RA-TKA. Methods: A prospective study of 50 primary RA-TKAs performed by a single surgeon was conducted between February and October 2023. Following full exposure, anterior tibial dislocation, and osteophyte removal, maximal medial and lateral compartment flexion laxity was quantified to the nearest 0.5 mm by the robotic system using a dynamic, surgeon-applied stress (SURGEON). This data was used to plan a balanced flexion gap by adjusting the femoral component size, rotation, and anterior-posterior translation. Flexion laxity was quantified again after distal femoral and proximal tibial resections using a ligament tensor instrument (TENSOR). These new data were used to plan for the same desired flexion gap using the same variables. Paired-samples t-tests and a simple linear regression were used for analysis. Results: Both methods produced near-identical recommendations for femoral component sizing (mean deviation 0.06 sizes, range -1 to +1 size; P = .569), rotation (deviation mean 1.0°, range -3.0° to +3.0°; P = .741), and anterior-posterior translation (deviation mean 0.13 mm, range -0.5 to +0.5 mm, P = .785). SURGEON femoral component rotation predicted TENSOR rotation (R2 = 0.157; 95% confidence interval = 0.124, 0.633; P = .004). Conclusions: Assessing flexion laxity with a surgeon-applied stress vs a ligament tensor produced near-identical laxity data in RA-TKA, suggesting surgeons may comfortably choose either technique as a reliable method. Level of Evidence: Level III.

Impact of change in coronal plane alignment of knee (CPAK) classification on outcomes of robotic-assisted TKA.

BACKGROUND: Mechanical alignment with total knee arthroplasty (TKA) has been widely used since the implantation of the first prosthetic knee. Multiple studies have reported 80% patient satisfaction with TKA. However, the reported patients' dissatisfaction is believed to be caused by having to convert different knee alignments to neutral alignments. It is postulated that a change in the CPAK classification of knees leads to patient dissatisfaction. Thus, we hypothesized that a change in CPAK classification with robot-assisted TKA with mechanical alignment does not significantly lead to patient dissatisfaction. METHODS: We retrospectively analyzed 134 patients who underwent robot-assisted mechanical alignment total knee arthroplasty (MA-TKA) using cementless implants and classified them into CPAK system pre- and post-operatively. One year after TKA surgery, we recorded binary responses to patients' satisfaction with the outcome of surgery and analyzed if a change in CPAK classification is associated with the outcome of surgery. RESULTS: We found that 125 out of 134 patients (93.28%) were happy with the outcome of surgery. CPAK classification was changed in 116 patients (86.57%) and maintained in 18 patients (13.43%). Our results also showed that 111 (95.7%) out of 116 patients who had a change in CPAK and 14 (77.8%) out of 18 patients who maintained their CPAK post-surgery were happy with the outcome of surgery (OR = 6.3, CI 1.741-25.17, P value = 0.019). CONCLUSION: We concluded that changing the patient's native joint line and CPAK classification does not significantly change the outcome of surgery in terms of satisfaction. The dissatisfaction rate of 20% as published by previous researchers may be confounded by other reasons and not just due to changes in alignment and joint line.

Evaluation of the External Rotation of the Femur Component in Functionally Aligned Robotic-Assisted Total Knee Arthroplasty.

Background The conventional total knee arthroplasty (TKA) for grade 4 knee arthritis lacks individualized strategies for determining femur component rotation, contributing to suboptimal clinical outcomes and heightened patient dissatisfaction. Methods One hundred consecutive active robotic-assisted TKA (RA-TKA) patients were retrospectively evaluated. The control group is the patients undergoing conventional TKA for grade 4 arthritis of the knee joint, where the femoral component is placed in a fixed 3-degree external rotation. The study aimed to explore the relationships between the posterior femoral axis of the functionally aligned TKA (FAA), the trans-epicondylar axis (TEA), and the posterior condylar axis (PCA). Specifically, it investigated whether there is a statistically significant difference in femoral component rotation between the functionally aligned TKA (FTKA) and the conventional 3-degrees of external rotation of the femoral component used in traditional TKA (C-TKA). Internal rotation is indicated by a negative value for the femur component. A student's t-test was employed to compare mean rotation values between FTKA and C-TKA, with a p-value below 0.05 considered statistically significant. Results A total of 100 patients (male: female, 11:89) were studied. The FAA was externally rotated in relation to the TEA (mean 1.451°, SD 1.023°, p-value <0.0001). As regards the PCA, the FAA was externally rotated (mean 2.36°, SD 2.221°, p-value 0.0002). These findings demonstrate a statistically significant difference in femoral component rotation between FTKA and C-TKA. Clinically, no patellofemoral complications or premature loosening were observed at one-year follow-up. Conclusion Functional alignment TKA technique resulted in external rotation of the femur component with respect to TEA and PCA. This negates the null hypothesis, indicating a statistically significant difference amongst the femur component rotation implanted according to the FTKA concept with robotic assisted technology and C-TKA.