Robotic Total Knee Replacement: Single-Centre, Prospective, Non-Randomised Comparative Study Comparing Restricted Kinematic Alignment Combined with a Load Sensor Versus Functional Alignment.

PurposeThis study aimed to compare postoperative clinical outcomes and soft tissue laxity between functional alignment (FA) and mechanical alignment (MA) in robot-assisted total knee arthroplasty (TKA).MethodsThirty-one FA and 31 MA TKAs performed using a robotic system were included in this retrospective study. Range of motion (ROM), the 2011 Knee Society Score (2011 KSS), and the Forgotten Joint Score-12 (FJS-12) at 6 weeks, 3 months, and 6 months after TKA, respectively, were compared between the two groups. Intraoperative laxities were compared between the two groups.ResultsAlthough no significant differences were noted in postoperative ROM and the 2011 KSS, the FJS-12 scores at 3 and 6 months after TKA were significantly higher in the FA group (64.4 and 68.4) than those in the MA group (51.9 and 57.0) (p<0.05 and p<0.05). At 90° flexion, the medial laxity of 1.1 mm in the FA group was significantly lower than that of 2.3 mm in the MA group (p < 0.001).ConclusionFA TKA was superior to MA TKA in achieving better FJS-12 and greater medial stability at 90° flexion.

Functional alignment (FA) in total knee arthroplasty (TKA) aims to achieve balanced gaps by adjusting implant positioning while minimizing changes to constitutional joint line obliquity (JLO). Although FA uses kinematic alignment (KA) as a starting point, the final implant positions can vary significantly between these two approaches. This study used the Coronal Plane Alignment of the Knee (CPAK) classification to compare differences between KA and final FA positions. A retrospective analysis compared pre-resection and post-implantation alignments in 2,116 robotic-assisted FA TKAs. The lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured to determine the arithmetic hip-knee-ankle angle (aHKA = MPTA - LDFA), JLO (JLO = MPTA + LDFA), and CPAK type. The primary outcome was the proportion of knees that varied ≤ 2° for aHKA and ≤ 3° for JLO from their KA to FA positions, and direction and magnitude of those changes per CPAK phenotype. Secondary outcomes included proportion of knees that maintained their CPAK phenotype, and differences between sexes. Overall, 71.6% had an aHKA change ≤ 2°, and 87.0% a JLO change ≤ 3°. Mean aHKA changed from -1.1° (SD 2.8°) in KA to -1.9° (SD 2.3°) in FA (mean difference (MD) -0.83 (SD 2.0); p < 0.001). Mean JLO changed from 173.9° (SD 3.0°) in KA to 174.2° (SD 2.6°) in FA (MD 0.38 (SD 2.3); p < 0.001). CPAK type was maintained in 58.1% of knees, with the proportion highest for Types I (73.9%), II (61.1%), and IV (51.2%). In valgus knees, 67.5% of Type III and 71.7% of Type VI were shifted to neutral phenotypes. There was minimal change to constitutional JLO across all CPAK types (MDs -2.0° to 1.2°). Functional alignment may alter CPAK type, but does not significantly change JLO. A kinematic starting point minimizes changes to native anatomy, while final position with FA provides an optimally balanced TKA.

Functional alignment (FA) has emerged as a personalized strategy in total knee arthroplasty (TKA) to optimize outcomes by accounting for patient-specific anatomical and soft tissue characteristics. Limited evidence exists on how polyethylene insert type, specifically cruciate-substituting (CS) versus posterior-stabilized (PS), impacts clinical outcomes and complications in this context. This retrospective comparative study included 329 patients who underwent robotic-assisted TKA with FA principles with a minimum 2-year follow-up. Patients were divided into two groups: CS or PS implants. CS inserts were selected for patients with an intact posterior cruciate ligament (PCL), while PS inserts were used in cases of PCL insufficiency or significant flexion contractures. Preoperative and post-operative outcomes, including Knee Society Scores (KSS), Forgotten Joint Scores (FJS), range of motion (ROM) and complications, were assessed. Implant survivorship was analyzed using the Kaplan-Meier method. At a median follow-up of 36 months, no significant differences were observed between CS and PS groups in KSS (knee: p = 0.45; function: p = 0.4), FJS (p = 0.7) or ROM (median flexion: 130° in both groups, p = 0.52). Specific complications included intraoperative lateral condyle fractures in the PS group and femoral component revisions due to instability in the CS group. The overall complication rates and implant survivorship were comparable (p = 0.55 and p = 0.85, respectively). This study is the first to evaluate polyethylene insert type in FA and demonstrates that both CS and PS inserts provide comparable outcomes and safety profiles in robotic-assisted TKA. These findings underscore the importance of patient-specific implant selection, with further research needed to assess long-term results. Level III.

Increased body mass index (BMI) poses challenges in total knee arthroplasty (TKA), including higher complication rates. Functional knee positioning (FKP) with robotic assistance provides a personalized approach to optimize alignment and soft-tissue balance, but its impact on patients with increased BMI remains unclear. This retrospective comparative study aims to evaluate the influence of obesity and its severity on clinical outcomes and complications in TKA performed with an image-based robotic system-guided by FKP principles. This retrospective comparative study included 372 patients who underwent robotic-assisted TKA following FKP principles. Patients were stratified into two main groups based on BMI (<30 ​kg/m2; 238 patients and ≥30 ​kg/m2; 134 patients). Outcomes included Knee Society Scores (KSS), Forgotten Joint Scores (FJS), range of motion (ROM), implant positioning, and complications, evaluated at a minimum follow-up of two years. Patients with increased BMI (≥30 ​kg/m2) demonstrated similar functional outcomes to patients with BMI <30 ​kg/m2 in terms of ROM, KSS, and FJS. However, the revision rate due to mechanical failures was significantly higher in the obese group (2.99% vs. 0.42%, p ​= ​0.04; hazard ratio ​= ​6.8; 95% CI, 1.09-42.31). Implant positioning was consistent across groups, except for reduced femoral external rotation in the increased BMI group (p ​= ​0.004). Robotic-assisted TKA with FKP principles achieves comparable functional outcomes for obese patients at a minimum of a 2-year follow-up, demonstrating the system's ability to address anatomical and functional challenges. However, obesity remains a critical risk factor for mechanical failures. III.

Use of computer-assisted navigation (CAN) and robotic-assisted (RA) surgery in total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) both necessitate the use of tracking pins rigidly fixed to the femur and tibia. Although periprosthetic fractures through tracking pin sites are rare, there is a paucity of literature on this potential complication. Therefore, the purpose of this study was to perform a systematic review of the current literature to assess the incidence and clinical outcomes of periprosthetic fractures through tracking pin sites following CAN and RA TKA and UKA. A systematic review was performed following PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines using the PubMed, MEDLINE, and Cochrane databases in April 2020. Studies were assessed for the presence of pin site fractures, fracture characteristics, and clinical outcomes. Seventeen clinical studies (5 case series, 1 cohort study, and 11 case reports) involving 29 pin-related fractures were included for review. The overall incidence ranged from 0.06% to 4.8%. The mean time from index arthroplasty to fracture was 9.5 weeks (range, 0 to 40 weeks). The majority of fractures occurred in the femoral diaphysis (59%). Nineteen fractures (66%) were displaced and 10 (34%) were nondisplaced or occult. The majority of cases were atraumatic in nature or involved minor trauma and were typically preceded by persistent leg pain. A transcortical pin trajectory, large pin diameter (>4 mm), diaphyseal fixation, multiple placement attempts, and the use of non-self-drilling, non-self-tapping pins were the most commonly reported risk factors for pin-related periprosthetic fractures following CAN or RA TKA. Surgeons should maintain a high index of suspicion for pin-related fractures in patients with ongoing leg or thigh pain after CAN or RA TKA in order to avoid fracture displacement and additional morbidity. As CAN and RA TKA have unique complication risks, the debate regarding the value of technology-assisted TKA and its cost-effectiveness continues. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Robotic-assisted (RA) technology is becoming increasingly popular in total knee arthroplasty (TKA) due to its improved alignment, accuracy, and precision compared with the conventional TKA. Despite reported benefits, disagreements exist regarding patient-reported outcomes and complication rates comparing RA TKA and conventional TKA. Thus, the purpose of the study is to report differences in patient outcomes and complication rates between patients who underwent RA versus conventional TKA. Methods: The authors retrospectively reviewed 239 primary knee arthroplasty cases (n=137 robot-assisted and n=102 conventional TKA) performed by a single fellowship-trained orthopaedic surgeon from January 1, 2016 to February 26, 2019. The electronic medical record and patient outcomes database were reviewed for demographic characteristics (age, sex, body mass index, and comorbidities), patient-reported outcomes (Short Form Health Survey and Oxford Knee Score), 90-day complications, and revision rates. Results: There was no statistically significant difference in patient-reported outcomes between conventional versus RA groups at two time points: preoperative and 2-year. Differences remained insignificant after controlling for age, sex, body mass index, and comorbidities. There was no statistically significant difference between the conventional and RA groups in revision rates (0.7% and 1%, respectively; P=1.00) or complication rates (1.5% and 3.9%, respectively; P=0.406). Conclusions: There were no differences in 90-day complications, revisions, and patient-reported outcome scores between RA TKA and conventional TKA groups at short-term follow-up. Surgeons can expect similar clinical outcomes without an increase in complications while taking advantage of increased accuracy in alignment and component placement. Further long-term study of RA TKA outcomes is warranted. Level of Evidence: Level III.

Functional, patient-reported, and radiographic outcomes of kinematic versus mechanical alignment in robotic total knee arthroplasty: A systematic review and meta-analysis.

Letter to the Editor on “Robot-Assisted Total Knee Arthroplasty Does Not Improve Long-Term Clinical and Radiologic Outcomes”

BackgroundRobot-assisted total knee arthroplasty (TKA) has been largely studied to confirm its advantages in terms of accurate component positioning, microembolus formation, less blood loss, and so on, but is currently usually performed under tourniquet due to its longer operative time than conventional TKA. The aim of this study was to estimate the effects of tourniquet use in robot-assisted TKA on blood loss, pain, functional recovery, and complications.MethodsPatients scheduled for robot-assisted TKA were prospectively randomized into a tourniquet or non-tourniquet group (each n = 14). The primary outcome measure was blood loss. The secondary outcome measures were operation time; visual analog scale (VAS) pain scores; time to achieve the first straight-leg raise; swelling of the thigh, knee, and calf; range of motion; Hospital for Special Surgery score; length of stay; and postoperative complications.ResultsThere was no significant difference in total blood loss between the tourniquet and non-tourniquet groups (738.57 ± 276.158 vs. 866.85 ± 243.422 ml, P = 0.061). The tourniquet group showed significantly lower intraoperative blood loss (P < 0.001), but higher hidden blood loss (P = 0.002). The non-tourniquet group showed better knee range of motion on postoperative days (PODs) 1–3 (all P < 0.001), less thigh swelling on PODs 2 and 3 (P < 0.05), earlier straight-leg raising (P = 0.044), and shorter length of stay (P = 0.044). Thigh pain VAS score at 1 month after surgery was significantly greater in the tourniquet group (P < 0.001), as was knee pain during activity and at rest on PODs 2–3 (all P < 0.05). The tourniquet group also showed a significantly higher rate of tension blisters (28.8% vs. 7.1%, P = 0.038).ConclusionsTourniquet use during robot-assisted TKA does not reduce total blood loss, and it appears to increase postoperative pain, aggravate muscle injury, and prolong postoperative recovery.Trial registration ChiCTR, ChiCTR2100041800. Registered 5 January 2021, http://www.chictr.org.cn/index.aspx.

To explore the short-term effectiveness of domestic robot-assisted total knee arthroplasty (RATKA) conducted by a prospective randomized controlled trial. Patients who were scheduled for primary unilateral TKA between October 2020 and December 2020 were eligible in this randomized controlled trial. According to the random number table method, they were allocated to the traditional TKA group and the RATKA group [application of the Yuanhua robotic-assisted TKA (YUANHUA-TKA) system during operation]. A total of 63 patients met the selection criteria were enrolled in the study, of which 3 cases voluntarily withdrew from the trial. And finally 60 cases were enrolled for analysis; of which 28 cases were in the RATKA group and 32 cases were in the traditional TKA group. There was no significant difference in gender, age, body mass index, American Society of Anesthesiologists (ASA) classification, duration of osteoarthritis, surgical side, and preoperative knee visual analogue scale (VAS) resting and motion scores, joint range of motion (ROM), Knee Society Score (KSS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) pain, stiffness, and function scores, hip-knee-ankle angle (HKA) deviation ( P>0.05). The operation time and intraoperative blood loss of the two groups were recorded. Knee joint VAS resting and motion scores, ROM, KSS scores, and WOMAC pain, stiffness, and function scores were used to evaluate the knee joint function and pain. Gait analysis (flexion and extension angle) was conducted at 3 months after operation. The full length X-ray films of lower limbs and anteroposterior and lateral X-ray films of knee joint were taken. The HKA deviation, lateral tibia component (LTC), frontal femoral component (FFC), frontal tibia component (FTC), and lateral femoral component (LFC) measured on the X-ray films were used to evaluat the lower limb alignment and prosthesis position. The operations of the two groups completed successfully; the incisions healed by first intention after operation, and no complications related to the operation occurred. The operation time of the RATKA group was significantly longer than that of the traditional TKA group ( t=12.253, P=0.001), and there was no significant difference in intraoperative blood loss between the two groups ( t=3.382, P=0.071). All patients were followed up 3 months. At 3 months after operation, the knee joint VAS resting and motion scores, ROM, KSS scores, and WOMAC pain, stiffness, and function scores improved significantly when compared with preoperatively in the two groups ( P<0.05); there was no significant difference of pre- and post-operative indicators between the two groups ( P>0.05). The gait analysis showed that the flexion and extension angle in the RATKA group was significantly bigger than that in the traditional TKA group ( t=9.469, P=0.003). X-ray films reexamination at 3 months after operation showed that the prostheses in the two groups were in good positions, and there was no adverse events such as prosthesis loosening or sinking. There were significant differences in the HKA deviation between pre- and post-operation in the two groups ( P<0.05), but the difference of pre- and post-operative HKA deviation between the two groups was not significant ( t=1.254, P=0.267). There was no significant difference in FFC, FTC, and LFC between the two groups ( P>0.05); the LTC was significantly smaller in the RATKA group than in the traditional TKA group ( t=17.819, P=0.000), which was closer to the ideal value. YUANHUA-TKA system can improve the accuracy of osteotomy and the prosthesis placement as well as the lower limb alignment. Its short-term effectiveness can be promised, but long-term effectiveness needs to be further studied.

Surgeon physical stress in the operating room is a known potential cause of musculoskeletal overuse injuries, specifically in surgeons who perform total knee arthroplasty (TKA). Injuries have been attributed to ergonomically challenging postures. This study compared surgeon lower back and shoulder posture between manual TKA (MTKA) and robotic assisted TKA (RATKA).Two surgeons performed a total six MTKA and six RATKA on a set of cadaveric knees. Movement and EMG sensors were secured to each surgeon to monitor lower back and shoulder movements, as well as muscle activities. Data was analyzed and activities were assessed as low, medium, or high risk, providing a score between 0-lowest and 16-highest. Risk data was compared between MTKA and RATKA for three separate surgical tasks: 1-bone cut preparation &amp;amp; cutting (MTKA = placement of cutting jigs, bone cutting, RATKA = array placement, bone registration, bone cutting), 2-knee balancing and 3-trialing.Overall, there were more high-risk shoulder than lower back activities in MTKA and RATKA. More high-risk movement and EMG stimulation were measured in the dominant shoulder than the non-dominant. When lower back and shoulder data were combined, highest risk task was bone cut preparation &amp;amp; cutting (MTKA: 13 vs. 6 vs. 6 and RATKA: 11 vs. 8 vs. 6), with a higher risk for MTKA than RATKA.Poor posture can be a potential cause for surgeon work-related injuries. This study evaluated which tasks presented highest risk to surgeon ergonomic safety while performing TKA, and found lower overall ergonomics risk for performing RATKA vs. MTKA. Although this study provides data indicating reduced ergonomic risk with RATKA, additional studies in the operating room need to be performed.

Failure to Restore Normal Trochlear Orientation Does Not Affect Postoperative Patella-Related Outcomes in Robotic-Assisted Functional Alignment Total Knee Arthroplasty.

Forgotten Joint Score: Comparison between total and unicondylar knee arthroplasty

Robotic-assisted total knee arthroplasty (RA-TKA) aims to improve outcomes and reduce costs, but its effect on in-hospital direct costs remains unclear. This study compares in-hospital direct costs between RA-TKA and conventional TKA (C-TKA). A retrospective review of elective TKAs from 1/2018-5/2023 at a single center was performed. RA-TKA and C-TKA patients were matched by demographics and surgery date. Cost metrics included total, fixed, variable direct costs and indirect costs. Operative times, length of stay (LOS), and in-hospital costs were compared using independent t-tests, Mann-Whitney U, and Chi-square tests. Pearson correlations assessed relationships between costs and clinical metrics. A hierarchical multilinear model was used to control for demographics, operative time, and LOS to isolate the cost of robotic assistance. Of 2590 primary TKAs, 440 used robotic assistance. After matching, 788 patients remained (397 RA-TKA, 391 C-TKA). Preoperative Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) and Veterans Rand 12 Item Health Survey (VR-12) scores were similar. RA-TKAs had longer operative times ("cut-to-close": 128 vs. 110min; "room-in to room-out": 202 vs. 182min; p < 0.001) and longer LOS (2.39 vs. 1.56days; p < 0.001). RA-TKAs had 17.8% higher total direct costs and 18.5% higher variable direct costs (p < 0.001). After adjusting for operative time and LOS, robotic assistance independently increased total direct cost by 4.2% of median C-TKA cost (p < 0.001). Robotics remained an independent predictor of total and variable direct cost (p < 0.001). RA-TKA incurs higher in-hospital direct costs than C-TKA, largely due to increased variable costs. Even after adjusting for operative time and LOS, robotic assistance independently contributes to higher total direct cost.

ABSTRACTBackgroundRobotic assistance and computer navigation systems are increasingly being used for total knee arthroplasty (TKA) with demonstrated improvements in early functional outcomes relative to conventional instrumentation. Patients are commonly discharged to inpatient rehabilitation following TKA with substantial associated costs to health care providers. We aimed to directly compare rates of discharge to inpatient rehabilitation between robotic assisted and computer navigated TKA to investigate differences in early functional outcomes between these technologies.MethodsA retrospective cohort study of patients with knee osteoarthritis undergoing computer navigated or robotic assisted primary TKA at a single institution between 01 January 2016 and 31 December 2023 was conducted. Propensity score matching was performed 1:1 with propensity scores estimated using logistic regression accounting for age, sex, body mass index, American Society of Anaesthesiologists classification, insurance status, and unilateral vs. bilateral procedure. Multivariable regression analyses were performed to evaluate differences in discharge to inpatient rehabilitation and hospital length of stay.ResultsData analyses included 1034 patients (517 matched pairs) who underwent robotic assisted, or computer navigated TKA procedures respectively. The odds of discharge to inpatient rehabilitation for robotic assisted compared to computer navigated TKA were not significantly different (odds ratio (OR) = 0.79, 95% CI 0.54–1.2, p = 0.22). A significant mean difference in acute hospital length of stay was observed (−0.42 days, 95% CI −0.73 to −0.11 days, p = 0.008) between robotic assisted compared to computer navigated TKA groups.ConclusionRobotic assisted TKA does not reduce the odds of discharge to inpatient rehabilitation but may result in significantly shorter acute hospital length of stay compared to computer navigated TKA.