Which method for femoral component sizing when performing kinematic alignment TKA? An in silico study

Comparative study of a single design of total knee arthroplasty inserted with or without a robotic system based on control of ligament balance: Accuracy and functional outcome at 1 year

INTRODUCTION

Robotic systems are helping to improve surgical precision with the aim of improving the functional outcome of total knee arthroplasty (TKAs). The OMNIBotics system is a semi-autonomous robotic system combining a dynamic ligament tensor and a robotic cutting guide for personalized ligament balancing. To our knowledge, there is no single-operator comparative series evaluating the contribution of this system. A retrospective comparative study was therefore carried out to compare, for the same prosthesis and operator: 1) the precision of the OMNIBotics system versus conventional ancillary equipment, 2) the functional results at 1 year postoperative for each groups.

HYPOTHESIS

The OMNIBotics system would be more accurate than the mechanical ancillary for performing planned alignments by reducing the number of outliers and would allow a significant improvement in functional scores at 1 year postoperative.

MATERIAL AND METHODS

A total of 106 patients were retrospectively included between October 2017 and December 2021; 53 patients (34 women, 19 men) underwent TKA using the OMNIBotics system (OMNI group) and 53 patients (41 women, 12 men) underwent TKA using conventional mechanical ancillary (Non OMNI group). The two groups were comparable (gender, Body Mass Index (BMI), American Society of Anesthesiologist (ASA) score, deformity, preoperative Oxford score) except for age. All patients underwent a full length X-ray of the lower limbs at 3 months post-operatively to calculate the postoperative Hip Knee Ankle (HKA) angle. This was compared with the planned HKA angle, which was different for the two groups (defined by the software for the OMNI group, equal to 180 ° for the Non OMNI group). All patients responded to an Oxford score preoperatively and then to an Oxford score and Forgotten Joint Score (FJS) at 1 year postoperative.

RESULTS

The number of patients with a difference ≤1 ° between measured and planned HKA angle was significantly higher (p = 0.032) in the OMNI group (60%, n = 32) than in the non-OMNI group (40%, n = 21). The OMNI group also had significantly fewer outliers (measured HKA angle >3° of the planned HKA angle) than the non-OMNI group (94%, n = 50 versus 81%, n = 43, p = 0.038). Postoperative Oxford and Forgotten Knee scores were significantly better in the OMNI group with a mean value of 38.4 ± 6.7 [range, 24 to 48] and 70.7 ± 22.5 [range 9 to 100] for Oxford and FJS scores in the OMNI group versus 33.5 ± 10.1 [range 8 to 45] and 56.9 ± 22.7 [range 8 to 100] for the Non OMNI group (p = 0.004 and 0.002 respectively).

CONCLUSION

The OMNIBotics is a non-imaging robotic assistance system which, after analysis of the ligament balance, enables accurate reproduction of the planning carried out, improving the patient's functional result at one year compared to a conventional ancillary system.

LEVEL OF EVIDENCE

III; Retrospective comparative study.

Kinematic alignment adequately restores trochlear anatomy, patellar kinematics and kinetics in total knee arthroplasty: A systematic review

PURPOSE

Patellofemoral pain, maltracking and instability remain common and challenging complications after total knee arthroplasty. Controversy exists regarding the effect of kinematic alignment on the patellofemoral joint, as it generally leads to more femoral component valgus and internal rotation compared to mechanical alignment. The aim of this systematic review is to thoroughly examine the influence of kinematic alignment on the third space.

METHODS

A systematic search of the Pubmed, Cochrane and Web of Science databases was performed to screen for relevant articles published before 7 April 2024. This led to the final inclusion of 42 articles: 2 cadaveric, 9 radiographic, 12 computer simulation and 19 clinical studies. The risk of bias was evaluated with the risk of bias in non-randomised studies - of interventions tool as the lowest level of evidence of the included clinical studies was IV. The effects of kinematic alignment on patellar kinematics and kinetics, trochlear anatomy reconstruction and patellofemoral complication rate were investigated.

RESULTS

Kinematic alignment closely restores native patellar kinematics and kinetics, better reproduces native trochlear anatomy than mechanical alignment and leads to a 0%-11.4% incidence of patellofemoral complications. A more valgus joint line of the distal femur can cause lateral trochlear undercoverage and a trochlear angle orientation medial to the quadriceps vector when applying kinematic alignment, both of which can be solved by using an adjusted design with a 20.5° valgus trochlea.

CONCLUSION

Kinematic alignment appears to be a safe strategy for the patellofemoral joint in most knees, provided that certain precautions are taken to minimize the risk of complications.

LEVEL OF EVIDENCE

Level IV clinical studies, in vitro research.

Automated Landmark Annotation for Morphometric Analysis of Distal Femur and Proximal Tibia

Manual anatomical landmarking for morphometric knee bone characterization in orthopedics is highly time-consuming and shows high operator variability. Therefore, automation could be a substantial improvement for diagnostics and personalized treatments relying on landmark-based methods. Applications include implant sizing and planning, meniscal allograft sizing, and morphological risk factor assessment. For twenty MRI-based 3D bone and cartilage models, anatomical landmarks were manually applied by three experts, and morphometric measurements for 3D characterization of the distal femur and proximal tibia were calculated from all observations. One expert performed the landmark annotations three times. Intra- and inter-observer variations were assessed for landmark position and measurements. The mean of the three expert annotations served as the ground truth. Next, automated landmark annotation was performed by elastic deformation of a template shape, followed by landmark optimization at extreme positions (highest/lowest/most medial/lateral point). The results of our automated annotation method were compared with ground truth, and percentages of landmarks and measurements adhering to different tolerances were calculated. Reliability was evaluated by the intraclass correlation coefficient (ICC). For the manual annotations, the inter-observer absolute difference was 1.53 ± 1.22 mm (mean ± SD) for the landmark positions and 0.56 ± 0.55 mm (mean ± SD) for the morphometric measurements. Automated versus manual landmark extraction differed by an average of 2.05 mm. The automated measurements demonstrated an absolute difference of 0.78 ± 0.60 mm (mean ± SD) from their manual counterparts. Overall, 92% of the automated landmarks were within 4 mm of the expert mean position, and 95% of all morphometric measurements were within 2 mm of the expert mean measurements. The ICC (manual versus automated) for automated morphometric measurements was between 0.926 and 1. Manual annotations required on average 18 min of operator interaction time, while automated annotations only needed 7 min of operator-independent computing time. Considering the time consumption and variability among observers, there is a clear need for a more efficient, standardized, and operator-independent algorithm. Our automated method demonstrated excellent accuracy and reliability for landmark positioning and morphometric measurements. Above all, this automated method will lead to a faster, scalable, and operator-independent morphometric analysis of the knee.