Joint line is restored in robotic-arm-assisted total knee arthroplasty performed with a tibia-based functional alignment

Introduction: Functional alignment (FA) in total knee arthroplasty (TKA) has been introduced to restore the native joint line obliquity, respect the joint line height and minimize the need of soft tissue releases. The purpose of this study was to assess the intraoperative joint line alignment and compare it with the preoperative epiphyseal orientation of the femur and tibia in patients undergoing robotic-arm-assisted (RA)-TKA using FA. Materials and Methods: This retrospective study included a consecutive series of patients undergoing RA-TKA between February 2019 and February 2021. The joint line orientation of the femur and tibia in the three-dimensions was calculated and classified on preoperative CT-scans and compared with the intraoperative implant alignment. The tibial cut was performed according to the tibial preoperative anatomy. The femoral cuts were fine-tuned based on tensioned soft tissues, aiming for balanced medial and lateral gaps in flexion and extension. Results: A total of 115 RA-TKAs were assessed. On average, the tibial component was placed at 1.8° varus (SD 1.3), while the femur was placed at 0.8° valgus (SD 2.2) and 0.6° external rotation (SD 2.6) relative to the surgical transepicondylar axis. Moderate to strong, statistically significant relationships were described between preoperative tibial coronal alignment and tibial cut orientation (r = 0.7, p < 0.0001), preoperative femoral orientation in the coronal and axial planes and intraoperative femoral cuts alignment (r = 0.7, p < 0.0001 and r = 0.5, p < 0.0001, respectively). One case (0.9%) of slight tibial component varus subsidence was reported 45-days post-operatively, but implant revision was not necessary. Conclusions: The proposed robotic-assisted functional technique for TKA alignment, with a restricted tibial component coronal alignment, based on the preoperative phenotype and femoral component positioning as dictated by the soft tissues, provided joint line respecting resections. Further studies are needed to assess long-term implant survivorship, patient satisfaction and alignment-related failures

Robotic arm-assisted unicompartmental knee arthroplasty: high survivorship and good patient-related outcomes at a minimum five years of follow-up

Purpose: Robotic arm-assisted unicompartmental knee arthroplasty (RA-UKA) has been shown to improve component placement, reduce intraoperative variability, increase patient satisfaction and improve short-term survivorship results. The aim of this retrospective study was to determine the incidence of revision and the clinical performance at a minimum of 5-year follow-up for a cohort of patients who received a medial RA-UKA. Methods: Between April 2011 and July 2013, a total of 254 patients underwent medial RA-UKA at a single centre. Clinical performance was investigated using the Forgotten Joint Score-12 (FJS-12) and a 5-level Likert scale made of five items to assess joint perception and patient satisfaction. Kaplan–Meier implant survivorship was calculated and reasons for revision were collected. The effect of age, gender and body mass index (BMI) on the probability of reporting high FJS-12 and satisfaction were assessed. Results: After considering exclusion criteria and loss to follow-up, a total of 216 patients (224 medial RA-UKAs) were assessed at a mean 5.9 years of follow-up. Five RA-UKAs underwent implant revision, resulting in an overall Kaplan–Meier survivorship of 97.8%. Unexplained knee pain (0.9%) was the most common reason for RA-UKA revision. Good-to-excellent FJS-12 scores and high satisfaction levels were reported at mid-term follow-up. Male patients had higher probability of having FJS-12 > 90 (p < 0.05) and high satisfaction levels (p < 0.05). Conclusions: RA-UKAs demonstrated high survivorship and good-to-excellent patient-reported outcome measures and satisfaction levels at minimum 5-year follow-up. Results for male patients had improved clinical performance when compared to female subjects. Level of evidence: IV

Mechanical alignment changes during flexion in total knee arthroplasty without affecting clinical outcomes

Background: Primary aim of this study is to investigate if Hip-Knee-Ankle angle, measured in the coronal plane, changes with knee flexion after total knee arthroplasty. The secondary aim is to assess the relationship between Hip-Knee-Ankle during knee flexion and clinical outcome at mid-term follow up. Methods: 334 computer assisted total knee arthroplasties were retrospectively evaluated. A total of 233 patients were available for assessment of clinical outcomes at last follow up (mean 35 months). Hip-Knee-Ankle angle at different degrees of knee flexion and components' alignment were recorded intraoperatively. Findings: Patients were stratified based on the preoperative alignment: 202 varus knees, 99 neutral knees, and 33 valgus knees. In the varus knee group, 146 patients (89%) maintained a neutral overall limb alignment when flexed to 20°, 118 (72%) remained neutrally aligned at 45° and 92 (54%) at 90°. In valgus knee group, 26 (90%) remained neutrally aligned at 20°, 22 (75%) at 45° and 16 (55%) at 90°. In neutrally-aligned knee group, 88 (96%) remained neutrally aligned at 20°, 73 (79%) at 45° and 61 (66%) at 90°. Femoral component external rotation was correlated with varus alignment in flexion. Good outcomes were reported in 181 (78%) cases, fair results in 28 (12%) cases, poor results in 24 (10%) of cases. Poor results were not correlated to Hip-Knee-Ankle angle at different knee flexion angles. Interpretation: This study demonstrates that intraoperative Hip-Knee-Ankle angle changes as the knee moves into deeper flexion. However, neutral Hip-Knee-Ankle through the range of motion does not correlate with superior outcomes

Robotic arm-assisted lateral unicompartmental knee arthroplasty: How are components aligned?

The purpose of this multicenter, retrospective, observational study was to investigate the association between intraoperative component positioning and soft tissue balancing, as reported by robotic technology for a cohort of patients who received robotic arm-assisted lateral unicompartmental knee arthroplasty (UKA) as well as short-term clinical follow-up of these patients. Between 2013 and 2016, 78 patients (79 knees) underwent robotic arm-assisted lateral UKAs at two centers. Pre- and postoperatively, patients were administered the Knee Injury and Osteoarthritis Score (KOOS) and the Forgotten Joint Score-12 (FJS-12). Clinical results were dichotomized based upon KOOS and FJS-12 scores into either excellent or fair outcome, considering excellent KOOS and FJS-12 to be greater than or equal to 90. Intraoperative, postimplantation robotic data relative to computed tomography-based components placement were collected and classified. Following exclusions and loss to follow-up, a total of 74 subjects (75 knees) who received robotic arm-assisted lateral UKAs were taken into account with an average follow-up of 36.3 months (range: 25.0-54.2 months) postoperative. Of these, 66 patients (67 knees) were included in the clinical outcome analysis. All postoperative clinical scores showed significant improvement compared with the preoperative evaluation. No association was reported between three-dimensional component positioning and soft tissue balancing throughout knee range of motion with overall KOOS, KOOS subscales, and FJS-12 scores. Lateral UKA three-dimensional placement does not seem to affect short-term clinical performance. However, precise boundaries for lateral UKA positioning and balancing should be taken into account. Robotic assistance allows surgeons to acquire real-time information regarding implant alignment and soft tissue balancing

Does component placement affect short-term clinical outcome in robotic-arm assisted unicompartmental knee arthroplasty?

Aims The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA). Patients and Methods Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded. Results Following exclusions and losses to follow-up, 334 medial robotic-arm assisted UKAs were assessed at a mean follow-up of 30.0 months (8.0 to 54.9). None of the measured parameters were associated with overall KOOS outcome. Correlations were described between specific KOOS subscales and intraoperative, post-implantation robotic data, and between FJS-12 and femoral component sagittal alignment. Three UKAs were revised, resulting in 99.0% survival at two years (95% confidence interval (CI) 97.9 to 100.0). Conclusion Although little correlation was found between intraoperative robotic data and overall clinical outcome, surgeons should consider information regarding 3D component placement and soft-tissue balancing to improve patient satisfaction. Reproducible and precise placement of components has been confirmed as essential for satisfactory clinical outcome

Clinical results and short-term survivorship of robotic-arm-assisted medial and lateral unicompartmental knee arthroplasty

Purpose: The aim of this multicentre, retrospective, observational study was to determine the incidence of revision and clinical results of a large cohort of robotic-arm-assisted medial and lateral UKAs at short-term follow-up. It was hypothesized that patients who receive robotic-arm-assisted UKA will have high survivorship rates and satisfactory clinical results. Methods: Between 2013 and 2016, 437 patients (470 knees) underwent robotic-arm-assisted medial and lateral UKAs at two centres. Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score 12 (FJS-12) and Short-Form Physical and Mental Health Summary Scales (SF-12) were administered to estimate patients’ overall health status pre- and post-operatively. Results were dichotomized as ‘excellent’ and ‘poor’ if KOOS/FJS-12 were more than or equal to 90 and SF-12 was more or equal to 45. Associations between patients’ demographic characteristics and clinical outcomes were investigated. Post-operative complications and pain persistence were recorded. Results: Following exclusions and losses to follow-up, 338 medial and 67 lateral robotic-arm-assisted UKAs were assessed at a mean follow-up of 33.5 and 36.3 months, respectively. Three medial UKAs were revised, resulting in a survivorship of 99.0%. No lateral implants underwent revision (survivorship 100%). On average, significant improvement in all clinical scores was reported in both medial and lateral UKA patients. In medial UKA patients, male gender was associated with higher probability of better scores in overall KOOS, FJS-12 and in specific KOOS subscales. No other associations were reported between biometric parameters and outcome for either medial or lateral UKA. Conclusions: Robotic-assisted medial and lateral UKAs demonstrated satisfactory clinical outcomes and excellent survivorship at 3-year follow-up. Continued patient follow-up is needed to determine the long-term device performance and clinical satisfaction. Level of evidence: Retrospective cohort study, Level IV

Robotic-Assisted versus Manually Implanted Total Hip Arthroplasty: A Clinical and Radiographic Comparison.

INTRODUCTION: Component positioning during THA is one of the more critical surgeon-controlled factors as malposition has been associated with higher rates of hip dislocations, poor biomechanics, accelerated wear rates, leg length discrepancies (LLDs), and revision surgeries. In order to reduce the rates of component malposition and improve surgical accuracy, robotic-assisted THA has developed increased interest. The primary objective of this study was to compare patient outcomes following THA using the Mako Stryker robotic system (Stryker Orthopaedics, Mahwah, New Jersey) to outcomes in patients who underwent conventional instrumented THA. MATERIALS AND METHODS: Consecutive patients undergoing THA with a direct-lateral surgical approach from a single surgeon were reviewed. Patients were treated with either a robotic-arm assisted total hip arthroplasty (RTHA) or a conventional-instrumented total hip arthroplasty (CTHA). Minimum follow up was 16 months. RESULTS: Robotic-assisted THA significantly improved patient outcomes compared to conventional THA. No significant differences were observed in postoperative radiographic outcomes between the RTHA and CTHA cohorts. In our analysis, patients in the RTHA cohort compared to the CTHA cohort had significantly higher Western Ontario and McMaster Universities Arthritis Index (WOMAC) (P CONCLUSION: Further studies, particularly prospective randomized studies, are necessary to investigate the short- and long-term clinical outcomes, possible long-term complications, and cost-effectiveness of robotic-assisted THA in regard to improving outcomes and accuracy

Robotic-Assisted versus Manually Implanted Total Hip Arthroplasty: A Clinical and Radiographic Comparison

INTRODUCTION: Component positioning during THA is one of the more critical surgeon-controlled factors as malposition has been associated with higher rates of hip dislocations, poor biomechanics, accelerated wear rates, leg length discrepancies (LLDs), and revision surgeries. In order to reduce the rates of component malposition and improve surgical accuracy, robotic-assisted THA has developed increased interest. The primary objective of this study was to compare patient outcomes following THA using the Mako Stryker robotic system (Stryker Orthopaedics, Mahwah, New Jersey) to outcomes in patients who underwent conventional instrumented THA. MATERIALS AND METHODS: Consecutive patients undergoing THA with a direct-lateral surgical approach from a single surgeon were reviewed. Patients were treated with either a robotic-arm assisted total hip arthroplasty (RTHA) or a conventional-instrumented total hip arthroplasty (CTHA). Minimum follow up was 16 months. RESULTS: Robotic-assisted THA significantly improved patient outcomes compared to conventional THA. No significant differences were observed in postoperative radiographic outcomes between the RTHA and CTHA cohorts. In our analysis, patients in the RTHA cohort compared to the CTHA cohort had significantly higher Western Ontario and McMaster Universities Arthritis Index (WOMAC) (P<0.001) and Harris Hip Scores (P<0.05) at final follow up. There were no significant differences between the RTHA cohort and CTHA cohorts in regard to cup inclination (°) (P=0.10), hip length difference (mm) (P=0.80), hip length discrepancy (mm) (P=0.10), and global offset difference (mm) (P=0.20). CONCLUSION: Further studies, particularly prospective randomized studies, are necessary to investigate the short- and long-term clinical outcomes, possible long-term complications, and cost-effectiveness of robotic-assisted THA in regard to improving outcomes and accuracy

Assessment of patient-specific instrumentation precision through bone resection measurements

Purpose: In the present study, the precision of two patient-specific instrumentation (PSI) systems for total knee arthroplasty (TKA) was evaluated by comparing bony resection thicknesses of the pre-operative PSI planning and intra-operative measurements by a vernier calliper. It was hypothesized that the data provided by pre-operative planning were accurate within \ub12 mm of the bone resection thickness measured intra-operatively. Methods: Forty-one patient-specific TKAs were examined: 25 performed with Visionaire\uae technology and 16 with OtisMed\uae system. PSI accuracy was analysed comparing the resected bone thicknesses in the femoral and tibial cuts with pre-operatively planned resections. To determine pre-operative planning precision, the thickness values reported by the PSI planning were subtracted from the values reported intra-operatively by the calliper. Results: The mean absolute differences between pre-operatively planned resections and corresponding intra-operative thickness measurements ranged from a minimum of 2.6 mm (SD 0.8) to a maximum of 3.6 mm (SD 1.3) in all three anatomical planes in both groups. In every plane, the mean absolute discrepancies between planned resections and measured cuts differed significantly from zero (p < 0.0001). The proportion of differences within \ub12 mm between intra-operative measured resections and planned PSI cuts occurred in more than 90 % of the cohort for femoral distal resections. Less precision was reported for the femoral posterior medial cuts (70.7 % within \ub12 mm) and the tibial cuts (70.7 % on the medial, 75.6 % on the lateral side). Prosthetic component alignment on the coronal and transverse planes resulted in considerable deviations from the pre-operative planning. Conclusion: The two examined PSI technologies were accurate in femoral distal cuts, determining acceptable femoral component placement on the coronal plane. Posterior femoral and tibial cuts were less precise. Deviations from the pre-operative resection planning were reported in every plane. Inaccuracy was explained by ambiguous custom-made jigs placement on the bony surface. Level of evidence: III