The Accuracy and Absolute Reliability of a Knee Surgery Assistance System Based on ArUco-Type Sensors.

Recent advances allow the use of Augmented Reality (AR) for many medical procedures. AR via optical navigators to aid various knee surgery techniques (e.g., femoral and tibial osteotomies, ligament reconstructions or menisci transplants) is becoming increasingly frequent. Accuracy in these procedures is essential, but evaluations of this technology still need to be made. Our study aimed to evaluate the system's accuracy using an in vitro protocol. We hypothesised that the system's accuracy was equal to or less than 1 mm and 1° for distance and angular measurements, respectively. Our research was an in vitro laboratory with a 316 L steel model. Absolute reliability was assessed according to the Hopkins criteria by seven independent evaluators. Each observer measured the thirty palpation points and the trademarks to acquire direct angular measurements on three occasions separated by at least two weeks. The system's accuracy in assessing distances had a mean error of 1.203 mm and an uncertainty of 2.062, and for the angular values, a mean error of 0.778° and an uncertainty of 1.438. The intraclass correlation coefficient was for all intra-observer and inter-observers, almost perfect or perfect. The mean error for the distance's determination was statistically larger than 1 mm (1.203 mm) but with a trivial effect size. The mean error assessing angular values was statistically less than 1°. Our results are similar to those published by other authors in accuracy analyses of AR systems.

Integration of Square Fiducial Markers in Patient-Specific Instrumentation and Their Applicability in Knee Surgery.

Computer technologies play a crucial role in orthopaedic surgery and are essential in personalising different treatments. Recent advances allow the usage of augmented reality (AR) for many orthopaedic procedures, which include different types of knee surgery. AR assigns the interaction between virtual environments and the physical world, allowing both to intermingle (AR superimposes information on real objects in real-time) through an optical device and allows personalising different processes for each patient. This article aims to describe the integration of fiducial markers in planning knee surgeries and to perform a narrative description of the latest publications on AR applications in knee surgery. Augmented reality-assisted knee surgery is an emerging set of techniques that can increase accuracy, efficiency, and safety and decrease the radiation exposure (in some surgical procedures, such as osteotomies) of other conventional methods. Initial clinical experience with AR projection based on ArUco-type artificial marker sensors has shown promising results and received positive operator feedback. Once initial clinical safety and efficacy have been demonstrated, the continued experience should be studied to validate this technology and generate further innovation in this rapidly evolving field.

Patient-specific instrumentation makes sense in total knee arthroplasty.

INTRODUCTION: Patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) surgery was initially developed to increase accuracy. The potential PSI benefits have expanded in the last decade, and other advantages have been published. However, different authors are critical of PSI and argue that the advantages are not such and do not compensate for the extra cost. This article aims to describe the recently published advantages and disadvantages of PSI. AREAS COVERED: Narrative description of the latest publications related to PSI in accuracy, clinical and functional outcomes, operative time, efficiency, and other benefits. EXPERT OPINION: We have published high accuracy of the system, with a not clinically relevant loss of accuracy, significantly higher precision with PSI than with conventional instruments, and a high percentage of cases in the optimal range and similar to that obtained with computer-assisted navigation, greater imprecision for tibial slope, a significant blood loss reduction, and time consumption, an acceptable and non-significant increase in the cost per procedure, and no difference in complications during hospital admission and at 90 days. We think that PSI will not follow the Scott Parabola and that it will continue to be a valuable type of device in some instances of TKA surgery.

Computed Tomography-Based Patient-Specific Instrumentation Loses Accuracy with Significant Varus Preoperative Misalignment.

Patient-specific instrumentation (PSI) has been introduced to simplify and make total knee arthroplasty (TKA) surgery more precise, effective, and efficient. We performed this study to determine whether the postoperative coronal alignment is related to preoperative deformity when computed tomography (CT)-based PSI is used for TKA surgery, and how the PSI approach compares with deformity correction obtained with conventional instrumentation. We analyzed pre- and post-operative full length standing hip-knee-ankle (HKA) X-rays of the lower limb in both groups using a convention > 180 degrees for valgus alignment and < 180 degrees for varus alignment. For the PSI group, the mean (± SD) pre-operative HKA angle was 172.09 degrees varus (± 6.69 degrees) with a maximum varus alignment of 21.5 degrees (HKA 158.5) and a maximum valgus alignment of 14.0 degrees. The mean post-operative HKA was 179.43 degrees varus (± 2.32 degrees) with a maximum varus alignment of seven degrees and a maximum valgus alignment of six degrees. There has been a weak correlation among the values of the pre- and post-operative HKA angle. The adjusted odds ratio (aOR) of postoperative alignment outside the range of 180 ± 3 degrees was significantly higher with a preoperative varus misalignment of 15 degrees or more (aOR: 4.18; 95% confidence interval: 1.35-12.96; p = 0.013). In the control group (conventional instrumentation), this loss of accuracy occurs with preoperative misalignment of 10 degrees. Preoperative misalignment below 15 degrees appears to present minimal influence on postoperative alignment when a CT-based PSI system is used. The CT-based PSI tends to lose accuracy with preoperative varus misalignment over 15 degrees.

Reliability of the posterior condylar offset.

The posterior condylar offset (PCO) has been proposed as a determinant of a postoperative range of motion after total knee arthroplasty, although there is no consensus. This study aimed to demonstrate the error introduced by forcing the femoral rotation to overlap both condyles for the "true" lateral X-ray projection for the PCO measurement. We hypothesize that the angular discrepancy between the posterior femoral cortical reference plane and the posterior condylar axis plane due to rotation invalidates the acquisition of reliable measurements on X-rays. We have measured the PCO in 50 "true" lateral X-rays and compared it with the medial and lateral condyles PCO's assessed on a computed tomography-scan-based three-dimensional (3D) model of each knee. PCO based on the 3D imaging differed significantly between the medial (25.8 ± 3.67 mm) and lateral (16.59 ± 2.92 mm) condyle. Three-dimensional PCO values differ significantly from those determined in the radiographic studies. Also, the mean values of the medial and lateral condyle PCO measurements differed significantly (p < 0.001) with all PCO measurements on radiographs. We have identified a difference between the posterior cortical plane and the posterior condylar axis projections, both on the axial plane with a mean value of 11.23° ± 3.64°. Our data show an interplane discrepancy angle between the posterior femoral diaphyseal cortical and the posterior condylar axis plane (due to the femur's necessary rotation to overlap both condyles) may invalidate the 2D X-ray PCO assessment as a reliable measurement.

Coronal and axial alignment relationship in Caucasian patients with osteoarthritis of the knee.

Individualized pre-operative assessment of the patterns of the lower extremity anatomy and deformities in patients undergoing total knee arthroplasty seems essential for a successful surgery. In the present study, we investigated the relationship among the coronal alignment and the rotational profile of the lower extremities in the Caucasian population with end-stage knee osteoarthritis. We conducted a prospective study of 385 knees that underwent a pre-operative three-dimensional computed tomography-based model. The lower extremity alignment was determined (mechanical tibiofemoral or hip-knee-ankle angle, supplementary angle of the femoral lateral distal angle, and proximal medial tibial angle). For each case, the femoral distal rotation (condylar twist angle), the femoral proximal version, and the tibial torsion were determined. As the coronal alignment changed from varus to valgus, the femoral external rotation increased (r = 0.217; p < 0.0005). As the coronal alignment changed from varus to valgus, the external tibial torsion increased (r = 0.248; p < 0.0005). No correlation was found between the global coronal alignment and the femoral version. The present study demonstrates a linear relationship between the coronal alignment and the rotational geometry of the distal femur. This correlation also occurs with the tibial torsion. Perhaps outcomes of total knee arthroplasty surgery might be improved by addressing these deformities as well.

Patient-Specific Instrumentation Accuracy Evaluated with 3D Virtual Models.

There have been remarkable advances in knee replacement surgery over the last few decades. One of the concerns continues to be the accuracy in achieving the desired alignment. Patient-specific instrumentation (PSI) was developed to increase component placement accuracy, but the available evidence is not conclusive. Our study aimed to determine a PSI system's three-dimensional accuracy on 3D virtual models obtained by post-operative computed tomography. We compared the angular placement values of 35 total knee arthroplasties (TKAs) operated within a year obtained with the planned ones, and we analyzed the possible relationships between alignment and patient-reported outcomes. The mean (SD) discrepancies measured by two experienced engineers to the planned values observed were 1.64° (1.3°) for the hip-knee-ankle angle, 1.45° (1.06°) for the supplementary angle of the femoral lateral distal angle, 1.44° (0.97°) for the proximal medial tibial angle, 2.28° (1.78°) for tibial slope, 0.64° (1.09°) for femoral sagittal flexion, and 1.42° (1.06°) for femoral rotation. Neither variables related to post-operative alignment nor the proportion of change between pre-and post-operative alignment influenced the patient-reported outcomes. The evaluated PSI system's three-dimensional alignment analysis showed a statistically significant difference between the angular values planned and those obtained. However, we did not find a relevant effect size, and this slight discrepancy did not impact the clinical outcome.

Impact of surgical instrumentation on hospital length of stay and cost of total knee arthroplasty.

BACKGROUND: We aimed to analyze the impact of two different types of surgical instrumentation (conventional manual instrumentation (CI) and patient-specific instrumentation (PSI)) on length of stay (LOS) and objectify differences in cost. We hypothesized that there are no differences in the LOS and cost due to the instrumentation system used. RESEARCH DESIGN AND METHODS: LOS was registered using inpatient admission data provided by the Institutional Management Control Department. We recorded the costs associated with each procedure that could be influenced by the use of one system or another during the in-hospital stay. We conducted a prospectively single-center cohort study of 305 TKAs. Surgery was performed with conventional CI in 122 cases and with PSI in 183 cases. RESULTS: The mean LOS for the CI group was 4.29 days (SD 1.65) and 4.22 days (SD 1.26), for the PSI group. No significant difference among both instrumentation systems was obtained. When comparing global costs, the mean cost was slightly higher (without a significant difference) for the PSI cases (€3110.24 vs. €2852.7 for the CI cases). CONCLUSIONS: LOS and overall cost, in hospitals with a low annual TKA surgery volume, are unrelated to conventional or patient-specific instrumentation.

Revision of total knee arthroplasty with the use of patient-specific instruments: an alternative surgical technique.

INTRODUCTION: Accuracy in the placement of components in revision total knee arthroplasty (R-TKA) surgery is sometimes challenging. The applicability of patient­specific instruments (PSI) in knee surgery has progressively expanded to types of surgery other than primary arthroplasty. Could this assistive technology be used to facilitate accurate R-TKA surgery? The aim of the current manuscript is to describe this new application of PSI for revision of TKA-to-TKA and to provide a step-by-step technical guideline for use. AREAS COVERED: We will describe the application and a detailed description of PSI technology to TKA revision surgery, step-by-step, from CT images acquisition for preoperative planning and PSI blocks production to the surgery. EXPERT COMMENTARY: The system can facilitate the accomplishment of the bony cuts for optimal implant placement and that can be useful in minimally altering the femoral and the tibial joint line. It is obvious that technology alone will not replace surgical skill and that accuracy of the system will also depend on the quality of the CT images and the ability of the software to prevent metal artifacts. Despite that, our initial results are promising and prove that the concept of applying PSI technology to the R-TKA surgery is feasible.

Comparison of weight-bearing full-length radiographs and computed-tomography-scan-based three-dimensional models in the assessment of knee joint coronal alignment.

BACKGROUND: The aim of the study was to determine any discrepancies among preoperative full-leg standing radiographs (LLR) and supine non-weight-bearing computed tomography (CT)-scan-based three-dimensional (3D) models in the assessment of the lower limb alignment prior to total knee arthroplasty (TKA) and answer the question of whether the LLR study can be obviated in preoperative planning when TKA is performed with patient-specific instrumentation (PSI). METHODS: LLR and CT-scan-based 3D models of 227 knees (183 patients) were measured. LLR data was then compared to 3D alignment data used to design the PSI for TKA surgery. RESULTS: Alignment on LLR ranged from 153 to 194° versus 161.5 to 190.5° with CT-scan-based 3D models. The mean (standard deviation, SD) difference among techniques was 1.9° (1.15°) with a statistically significant difference (P = 2e-16, namely P < .0001). Supine CT-scan-based 3D models underestimated the deformity in 167 cases (73.6%), exactly matched the value of LLR in 24 cases (10.6%) and overestimated the deformity in 36 cases (15.8%). CONCLUSION: CT-scan-based models underestimate the degree of deformity at the knee joint. Despite the accurate information provided by the CT-scan and the 3D models (which is the basis for the planning of bone cuts), weight-bearing LLR should not be overlooked in the planning of TKA surgery to assess the extent of the coronal mediolateral instability.

Planning on CT-Based 3D Virtual Models Can Accurately Predict the Component Size for Total Knee Arthroplasty.

The ability to predict accurate sizing of the implant components for total knee arthroplasty surgery can have several benefits in the operating room, in terms of simplifying the workflow and reducing the number of required instrument trays. Planning on a three-dimensional (3D) virtual model can be used to predict size. The aim of this study was to quantify the accuracy of the surgeon-validated plan prediction on a computed tomography (CT)-based system. The clinical records of 336 cases (267 patients), operated using a CT-based patient-specific instrumentation, have been reviewed for the size of implanted components. Preoperative default planning (according to the preferences of the surgeon) and approved planning have been compared with the size of implanted components for both the femur and tibia. The prosthesis size, preplanned by the manufacturers, was modified by the surgeon during the validation process in 0.9% of cases for the femoral component and in 2.7% of cases for the tibial component. The prosthesis size, preplanned by the surgeon after the validation process, was used in 95.8% for the femur and 92.6% for the tibia. Concordance on the size of the surgeon-validated plan and the finally implanted size was perfect for both, the femoral (κ = 0.951; 95% confidence interval [CI]: 0.92-0.98) and the tibial component (κ = 0.902; 95% CI: 0.86-0.94). The most frequent change of size (51%) was an increase by one size of the planned tibial component. Planning of knee arthroplasty surgery on a 3D virtual, CT-based model is useful to surgeons to help predict the size of the implants to be used in surgery. The system we have used can accurately predict the component size for both the femur and tibia. This study reflects a study of level III evidence.

Patient-specific instrumentation in total knee arthroplasty.

INTRODUCTION: Total knee arthroplasty (TKA) is one of the most commonly performed orthopedic procedures. During the past decade, patient-specific instrumentation (PSI) has been commercially introduced in order to simplify and make TKA surgery more effective, precise and efficient than conventional mechanical instrumentation (CI) and computer-assisted surgery (CAS). Nevertheless, there are critical arguments against PSI for routine use. The aim of the current manuscript is to describe advantages and limitations of PSI for primary TKA. AREAS COVERED: By means of a description of the available literature different aspects are discussed (accuracy, clinical and functional outcomes, operative time, blood loss, efficiency and costs). EXPERT OPINION: Most publications do not claim a significant increase in PSI accuracy over CI, but they also do not postulate PSIs accuracy is worse either. Regarding clinical aspects, PSI did not appear to give any advantage over standard techniques although, equally, it did not appear to show any disadvantages. PSI seems to reduce operative time, could reduce perioperative blood loss and provides logistical benefits in the operation room. Further studies will be required to more thoroughly assess all the advantages and disadvantages of this promising technology as an alternative to CI and CAS.

Silicone ring tourniquet versus pneumatic cuff tourniquet in total knee arthroplasty surgery: A randomised comparative study.

INTRODUCTION: The aim of the present study was to compare a silicone ring tourniquet (SRT) and a classic pneumatic cuff tourniquet (PT) in patients undergoing total knee replacement. We have compared the impact on the glycolytic activity caused by the ischaemia applied to the limb during the surgery. MATERIAL AND METHODS: 140 patients that underwent total knee arthroplasty (TKA) were randomised in two groups. Serum lactate determination was made by reactive strips of enzymatic-amperometric detection, 5 min before tourniquet application and 5 min after tourniquet removal. RESULTS: The mean tourniquet time was similar for both groups (p 0.13). Postoperative serum lactate levels were higher with statistical significance than the preoperative levels and with a positive Pearson´s correlation in the overall cases. The postoperative serum lactate levels where higher in the PT group (4.097 ±â€¯2.248 mmol/L) than the SRT group (3.499 ±â€¯1.566 mmol/L). There was no significant difference (p 0.07) to be able to affirm that there was a difference of the anaerobic metabolism according to the tourniquet system used. DISCUSSION: Ischaemia applied to the lower extremity during knee replacement surgery can produce tissue injury. Serum lactate determination allows comparison of the ischaemic changes during TKA surgery caused by two different tourniquet systems. CONCLUSIONS: SRT may be not disadvantageous compared to the classic PT from the impact on the glycolytic activity caused by the ischaemia.Level of evidence II.