Comparison of Clinical Outcomes and Soft Tissue Laxity Between Robot-Assisted Functionally and Mechanically Aligned Total Knee Arthroplasty

Background: Total knee arthroplasty (TKA) is an effective procedure for symptomatic end-stage knee arthritis with good clinical and survivorship outcomes. However, up to 20% of patients report dissatisfaction following TKA. Recent studies have suggested that this may be at least partially due to suboptimal limb alignment or ligament imbalance. This study compared clinical outcomes at 1 year post-operatively (i.e., the 2011 Knee Society Score [KSS] and Forgotten Joint Score [FJS]) between two robotic-assisted personalised TKA techniques: functional alignment (FA) and an original technique combining restricted kinematic alignment (rKA) with a load sensor to achieve reliable ligament balancing (via bone re-cutting with a robotic arm). Methods: This single-centre, prospective, comparative study was performed at a robotic-assisted arthroplasty centre. The study population consisted of an FA group (43 patients) and rKA/sensor group (47 patients). Clinical outcomes were measured at 1 month post-operatively (visual analogue scale [VAS] pain score, flexion, range of motion [ROM], use of a mobility aid and stiffness) and at 1 year (2011 KSS, FJS, VAS, flexion and ROM). Results: There were no statistical significant differences in 2011 KSS or FJS at 1 year post-operatively between the two groups. Multivariate analysis showed no independent association of either technique with the 1-year follow-up KSS Objective Knee Indicators score (adjusted beta coefficient (aβ) = -2.371 [-7.380; 2.638], p = 0.357), KSS Patient Satisfaction score (aβ = -2.522 [-6.887; 1.842], p = 0.262), KSS Patient Expectations score (aβ = 0.629 [-0.928; 2.186], p = 0.431), KSS Functional Activities score (aβ = -3.399 [-10.881; 4.082], p = 0.377) or 1-year follow-up FJS (aβ = -5.168 [-19.887; 9.550], p = 0.494). Conclusions: There were no significant differences between the FA and rKA/load sensor groups in the 2011 KSS or FJS at 1 year post-operatively. To our knowledge, this is the first study to compare clinical outcomes between robotic-assisted FA TKA and rKA TKA. Clinical outcomes in the rKA/sensor group were similar to previous studies using rKA without robotic assistance or a load sensor. This was also the first report of the clinical outcomes of FA. The results need to be validated by larger scale studies to avoid potential type 2 errors.

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

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.

The prevalence of obesity has been steadily increasing over the last two decades1. Total knee arthroplasty (TKA) in the setting of obesity demonstrates increased risk of medical perioperative complications, however there is no conclusive evidence on the impact obesity has on TKA outcomes2,3. The purpose of this study was to investigate the effects of obesity on functional outcomes after TKA in a prospective cohort analysis. Patients undergoing unilateral TKA due to osteoarthritic changes were recruited. Functionality was measured at pre-op, 6 and 12 months post-op using the Forgotten Joint Score-12 (FJS-12) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC). Two linear-fixed effects models with contrasts were performed examining the impact of obesity (pre-op BMI, treated as a continuous variable) on return to function (FJS-12; WOMAC). Contrasts of estimated marginal means (EMMs) were used to examine functional change over time between various BMI levels (18, 21.75, 27.5, 32.5, 37.5, 42.5) representative of the World Health Organization's BMI classifications (underweight, normal, pre-obesity, obesity class I, II, and III) with pre-obesity serving as the comparison level. Both models controlled for potential effects of age, sex, and two comorbid conditions (diabetes, cardiovascular) that were associated with elevated pre-op BMI. Of the 351 enrolled patients, 296 completed one year follow-up and were included in the analysis. Approximately 61% (n=180) of participants were female, the mean (SD) age was 66.04 (7.64) years, and mean BMI (SD; range) at pre-op was 34.04 (6.93; 18.3, 53.0). Overall mean (SD) FJS-12 scores at pre-op, 6, and 12 months were 11.9 (11.8), 62.7 (27.5), 64.9 (27.9) respectively. Overall mean (SD) WOMAC scores at pre-op, 6, and 12 months were 51 (15.8), 14.1 (15.0), 12.3 (13.9) respectively. No differences were found in length of stay (LOS), readmissions, and ED visits among BMI categories. Compared to the pre-operative score, significant differences by BMI categories were observed for the 6-month FJS-12 (β = −0.66, p = .007) and 12-month WOMAC (β = −0.34, p = .021) scores. For example, at 6 months a greater change in FJS-12 score was observed for those with lower levels of BMI compared to those with higher levels of BMI. However, by 12 months, all patients appeared to return to functional levels regardless of BMI level. Despite a slower return to function, patients with elevated BMI are able to return to similar levels of function to those with a lower BMI by 12 months. We did not find any significant differences in readmission, ED visits, or LOS. This similar return to function justifies candidacy for surgery.

Patient dissatisfaction rates following total knee arthroplasty (TKA) reported in the literature reach 20%. The optimal coronal alignment is still under debate. The aim of this retrospective study was to compare clinical outcomes in different coronal plane alignment of the knee (CPAK) phenotypes undergoing mechanically aligned (MA) TKA. The hypothesis was that knees with preoperative varus arithmetic hip-knee-ankle angle (aHKA) would achieve inferior clinical outcomes after surgery compared to other aHKA categories. Additionally, another objective was to assess CPAK phenotypes distribution in the study population. A retrospective selection was made of 180 patients who underwent MA TKA from April 2021 to December 2022, with a 1-year follow-up. Coronal knee alignment was classified according to the CPAK classification. Clinical outcome evaluations were measured using the Knee Society Score (KSS), Oxford Knee Score (OKS), Short Form Survey 12and Forgotten Joint Score (FJS). Differences in clinical outcomes were considered statistically significant with a p value <0 .05. Patients with varus aHKA achieved significantly inferior outcomes at final follow-up compared to other aHKA categories in KSS pt. 1 (79.7 ± 17.2 vs. 85.6 ± 14.7; p = 0.028), OKS (39.2 ± 9.2 vs. 42.2 ± 7.2; p = 0.019) and FJS (75.4 ± 31.0 vs. 87.4 ± 22.9; p =0 .003). The most common aHKA category was the varus category (39%). The most common CPAK phenotypes were apex distal Types I (23.9%), II (22.8%)and III (13.3%). MA TKA does not yield uniform outcomes across all CPAK phenotypes. Varus aHKA category shows significantly inferior results at final follow-up. The most prevalent CPAK categories are varus aHKA and apex distal JLO, with phenotypes I, IIand III being the most common. However, their gender distribution varies significantly. Level IV.

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.

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.

Kinematic alignment is bone and soft tissue preserving compared to mechanical alignment in total knee arthroplasty

To identify, synthesise and critically appraise the findings of meta-analyses that compare patient-reported outcome measures (PROMs) between unrestricted kinematic alignment and mechanical alignment in total knee arthroplasty (TKA). It was hypothesised that some meta-analyses inaccurately combine PROMs from unrestricted and restricted kinematic alignment techniques. Two authors independently screened articles based on inclusion and exclusion criteria and assessed the methodological quality based on the 16 domains of A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). Effect sizes of difference in PROMs were tabulated for each meta-analysis. Studies included in the meta-analyses were assessed to determine if they were on true unrestricted kinematic alignment. A secondary meta-analysis excluded studies on restricted kinematic alignment techniques, to recalculate pooled estimates (mean difference (MD) with their 95% confidence interval (CI)) of the Knee Society Score (KSS), Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Forgotten Joint Score (FJS). The quality of evidence was assessed using the GRADE. There were 15 meta-analyses pooling data from 39 clinical studies eligible for data extraction. None fulfilled all seven critical AMSTAR-2 domains. Some reported kinematic alignment yielded superior KSS (Function, n = 9; Knee, n = 6: Combined, n = 8), OKS (n = 7), WOMAC (n = 8) and FJS (n = 1). The secondary meta-analysis included only studies on unrestricted kinematic alignment and results at the latest follow-up, for which the mean and standard deviations were reported and revealed no difference in KSS, OKS, WOMAC or FJS between kinematic and mechanical alignment. GRADE analysis revealed 'very low' quality of evidence for KSS, WOMAC and FJS, while it was 'low' quality for OKS. Current evidence suggests no difference in PROMs between kinematic and mechanical alignment in TKA. Meta-analyses that report the contrary often need more rigour as they pool studies on various kinematic alignment techniques or represent the same cohort at different times. Orthopaedic societies should promote using objective outcome measures to evaluate and compare alignment techniques. Systematic review protocol registration (Prospero: CRD42023434713). Level III.

Forgotten Joint Score: Comparison between total and unicondylar knee arthroplasty

Background: It is generally accepted that total knee arthroplasty (TKA) after high tibial osteotomy (HTO) is technically more difficult; however, there is still disagreement whether the subsequent arthroplasty is compromised. Objectives: The current case series study aimed to assess patients treated by knee arthroplasty after a previous high tibial osteotomy and to determine the influence of this osteotomy on the clinical and radiologic outcomes of subsequent arthroplasty. Methods: Up to April 2013, twenty-three patients with a history of twenty-five proximal tibial osteotomies prior to TKA were identified and compared with a matched group who underwent primary TKA in Shafa Orthopedic Hospital, Tehran, Iran. Demographic parameters of patients, surgical details, the knee range of motion (ROM), and American functional knee society (AKS) scores before and after TKA were recorded in the HTO and control groups. Weight bearing alignment radiographs were taken preoperatively and at the last follow-up. At the latest visit, patients’ satisfaction was recorded. Results: After an average of 49 months follow-up, all patients in the HTO and control groups were satisfied with their current level of function. In the HTO group, the rectus snip had to be used for better exposure in eight cases. There was no statistically significant difference between the two groups in postoperative knee ROM, mechanical leg alignment and mean functional knee society score, but the mean of operation time in the HTO group was significantly longer than that of the TKA time in the control group. Conclusion: Although knee arthroplasty after HTO is technically more challenging than a primary procedure, the results of clinical scores, postoperative ROM and radiological evaluation in the study subjects were comparable with those of the primary TKA in midterm follow-up. Rectus snip is a safe procedure in such difficult cases for better exposure.

BackgroundThis study evaluates the clinical evidence for performing total knee arthroplasty (TKA) without a tourniquet, a shift from the near-universal use in 2009 to current trends towards tourniquet-less TKA in Norway and Sweden. This change is set against a backdrop of conflicting evidence regarding the positive and negative effects of tourniquet use.Questions/purposesThe aims were to determine if the tourniquet has an impact on [1] Forgotten Joint Score-12 (FJS-12) at 8 weeks after surgery; [2] postoperative strength and function; [3] postoperative pain and opioid analgesic use; and [4] operative time, bleeding, and length of stay (LOS).MethodsEighty-one patients were randomised to TKA with or without a tourniquet. The outcome measures, FJS-12, muscle strength, functional test, pain, estimated blood loss, haemoglobin (Hb) loss, knee circumference, opioid consumption, and LOS were assessed preoperatively and at 1 day, 8 weeks, and 1 year after surgery.ResultsNo significant difference in FJS-12 scores was found between the two groups at postoperative 8 weeks. However, the tourniquet group showed statistically significant better knee extension strength at 8 weeks (p = 0.045). There were no differences in other outcomes, except for a greater decrease in haemoglobin levels (p = 0.02) and higher estimated perioperative blood loss (p < 0.001) in the no tourniquet group than the torniquet group.ConclusionsOur study indicates that tourniquet use during TKA causes no significant differences in FJS-12 at 8 weeks, significantly reduces bleeding and postoperative Hb loss, and improves quadriceps strength at 8 weeks.Trial registrationClinicaltrails.gov. Registry Number: NCT03666598. Registered 30 August 2018.

BackgroundThe FINE total knee was developed in Japan and clinical use began in 2001. It has unique design features, including an oblique 3o femorotibial joint line that reproduces anatomical geometry. Although 20 years have passed since the FINE knee was clinically used for the first time in Japan, a formal clinical evaluation including patient-reported and radiographic outcomes has not been undertaken.MethodsA total of 175 consecutive primary cruciate-retaining (CR)-FINE total knee arthroplasties (TKAs) at our hospital between February 2015 and March 2017 were included in this study. Three years postoperatively, range of motion (ROM), Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Forgotten Joint Score (FJS) were recorded and compared with preoperative scores. Radiographic analyses including mechanical alignment, component alignment, and incidence of radiolucent lines also were undertaken based on the radiographs 3 years postoperatively.ResultsOne-hundred twenty-two knees (70%) were available for 3-year follow-up data using KOOS, except for the sports subscale. Postoperative KOOS-symptom, −pain and -ADL were > 85 points, but KOOS-sports, −QOL and FJS were less satisfactory. ROM, KSS and all the subscales of KOOS were significantly improved compared with preoperative scores. Postoperative mean FJS was 66 and was significantly correlated with all the subscales of KOOS, but not with postoperative ROM. Radiolucent lines ≧1 mm wide were detected in five knees (4.1%). There were no major complications needing revision surgeries.ConclusionsPatient-reported outcomes (PROs) for symptoms, pain and ADL after the CR-FINE TKA were generally improved, but those for sports, QOL and FJS were improved less. The incidence of radiolucent lines was rare but detected around the femoral components. With the mid- to long-term follow-up, improvements of surgical technique will be necessary to achieve better PROs from patients receiving the FINE knee.

BackgroundMaking decisions in alignment techniques in total knee arthroplasty (TKA) remains controversial. This study aims to identify the potential patients who were suitable for the kinematic (KA) or mechanical alignment (MA).MethodsWe reviewed 296 consecutive patients (296 TKAs, including 114 KA-TKAs and 182 MA-TKAs) who underwent unilateral TKA using a computer-assisted navigation from 2016 to 2018 in our prospectively maintained database. The minimum followup was 1 year. Clinical outcomes including the range of motion (ROM) and knee society score (KSS) were compared between KA-TKAs and MA-TKAs. Multiple regression models were used to evaluate the relationship between alignment techniques and KSS at the 1-year followup. Interaction and stratified analyses were conducted according to gender, age, body mass index (BMI), preoperative hip-knee-ankle (HKA) angle, ROM and KSS.ResultsROM and KSS at the 1-year followup didn’t differ between MA-TKAs and KA-TKAs (all p > 0.05). Alignment techniques did not associate with postoperative ROM (Adjusted β = 0.4, 95% confidence interval [CI]: − 0.3, 1.6; p = 0.752) or 1-year KSS (Adjusted β = 2.2, 95%CI: − 0.7, 5.6; p = 0.107). Patients with a BMI more than 30 kg/m^2 achieved better 1-year KSS when using MA than KA (p for interaction< 0.05). Additionally, patients with preoperative HKA angle more than 10 degrees varus benefited more from KA than MA (p for interaction< 0.05).ConclusionsPatients with severe varus deformity may be suitable for the KA technique, whereas MA should be used in obese patients.

BackgroundLow knee awareness after minimally invasive total knee arthroplasty (TKA) has become the ultimate target of a natural-feeling knee that meets patient expectations. The objective of this research was to compare the clinical outcomes of TKA via the mini-midvastus (MMV) approach or the medial parapatellar (MPP) approach, and to evaluate which approach can lead to a better quality of life after surgery.MethodsFrom January 2015 to December 2016, a retrospective cohort study was conducted in 330 patients who underwent TKA via a mini-midvastus (MMV) approach. During this period, we also selected 330 patients who underwent TKA via a medial parapatellar (MPP) approach (MPP group) for comparison. Clinical results were assessed with the visual analog scale score for pain, range of motion, and the Knee Society Score. The Forgotten Joint Score was used to analyze the ability to forget the joint.ResultsThere were significant differences with regard to visual analog scale score, range of motion, and the Knee Society Score until 6 months after surgery between the MMV and MPP groups (p < 0.05), but the differences were not significant at 12 months, 24 months, and 36 months after surgery. However, there were significant differences in the Forgotten Joint Score between the groups during the follow-up period (p < 0.05).ConclusionWhen forgetting the artificial joint after TKA is the ultimate target, better quality of life can be acquired by performing TKA via the MMV approach. In addition, compared with the MPP approach, the MMV approach can offer less pain and a faster recovery.