Healthy Knee Kinematic Phenotypes Identification Based on a Clustering Data Analysis

The purpose of this study is to identify healthy phenotypes in knee kinematics based on clustering data analysis. Our analysis uses the 3D knee kinematics curves, namely, flexion/extension, abduction/adduction, and tibial internal/external rotation, measured via a KneeKG™ system during a gait task. We investigated two data representation approaches that are based on the joint analysis of the three dimensions. The first is a global approach that is considered a concatenation of the kinematic data without any dimensionality reduction. The second is a local approach that is considered a set of 69 biomechanical parameters of interest extracted from the 3D kinematic curves. The data representations are followed by a clustering process, based on the BIRCH (balanced iterative reducing and clustering using hierarchies) discriminant model, to separate 3D knee kinematics into homogeneous groups or clusters. Phenotypes were obtained by averaging those groups. We validated the clusters using inter-cluster correlation and statistical hypothesis tests. The simulation results showed that the global approach is more efficient, and it allows the identification of three descriptive 3D kinematic phenotypes within a healthy knee population.

Three-Dimensional-Printed Scaffolds for Meniscus Tissue Engineering: Opportunity for the Future in the Orthopaedic World

The meniscus is a critical component of a healthy knee joint. It is a complex and vital fibrocartilaginous tissue that maintains appropriate biomechanics. Injuries of the meniscus, particularly in the inner region, rarely heal and usually progress into structural breakdown, followed by meniscus deterioration and initiation of osteoarthritis. Conventional therapies range from conservative treatment, to partial meniscectomy and even meniscus transplantation. All the above have high long-term failure rates, with recurrence of symptoms. This communication presents a brief account of in vitro and in vivo studies and describes recent developments in the field of 3D-printed scaffolds for meniscus tissue engineering. Current research in meniscal tissue engineering tries to combine polymeric biomaterials, cell-based therapy, growth factors, and 3D-printed scaffolds to promote the healing of meniscal defects. Today, 3D-printing technology represents a big opportunity in the orthopaedic world to create more specific implants, enabling the rapid production of meniscal scaffolds and changing the way that orthopaedic surgeons plan procedures. In the future, 3D-printed meniscal scaffolds are likely to be available and will also be suitable substitutes in clinical applications, in an attempt to imitate the complexity of the native meniscus.

Effects of Textured Insoles on the Balance of Individuals with Knee Osteoarthritis in Dynamic Perturbations

The effectiveness of adding plantar-surface texture to improve balance has been demonstrated in a variety of demographics. It is critical to investigate whether textured insoles can improve balance in people with knee osteoarthritis (OA), who have compromised the somatosensory function of the affected joint and, as a result, are at a higher risk of falling. Thus, this study investigated the degree of benefit from the use of textured insoles for improving balance and compared the balance of people with knee OA to healthy matched peers. This study included eighteen people with knee OA and eighteen healthy, aged, gender, height, weight, and BMI matched controls who were assessed on balance using the sensory organization test and the motor control test. Balance was improved in both groups when the textured insoles were worn, and the healthy knee group demonstrated significantly better balance performance than the knee OA group. The benefits of this study for individuals with knee OA are that it may lead to the development of an evidence-based footwear intervention that is noninvasive, simple to use, and inexpensive, in addition to allowing the user to self-manage and the ability to reduce the risk of falls, thereby improving their quality of life.

An insert with less than spherical medial conformity causes a loss of passive internal rotation after calipered kinematically aligned TKA

Introduction In total knee arthroplasty (TKA), the level of conformity, a medial stabilized (MS) implant, needs to restore native (i.e., healthy) knee kinematics without over-tensioning the flexion space when the surgeon chooses to retain the posterior cruciate ligament (PCL) is unknown. Whether an insert with a medial ball-in-socket conformity and lateral flat surface like the native knee or a less than spherical medial conformity restores higher and closer to native internal tibial rotation without anterior lift-off, an over-tension indicator, when implanted with calipered kinematic alignment (KA), is unknown. Methods and materials Two surgeons treated 21 patients with calipered KA and a PCL retaining MS implant. Validated verification checks that restore native tibial compartment forces in passive flexion without release of healthy ligaments were used to select the optimal insert thickness. A goniometer etched onto trial inserts with the ball-in-socket and the less than spherical medial conformity measured the tibial rotation relative to the femoral component at extension and 90° and 120° flexion. The surgeon recorded the incidence of anterior lift-off of the insert. Results The insert with the medial ball-in-socket and lateral flat surface restored more internal tibial rotation than the one with less than spherical medial conformity, with mean values of 19° vs. 17° from extension to 90° flexion (p < 0.01), and 23° vs. 20°–120° flexion (p < 0.002), respectively. There was no anterior lift-off of the insert at 90° and 120° flexion. Conclusion An MS insert with a medial ball-in-socket and lateral flat surface that matches the native knee’s spherical conformity restores native tibial internal rotation when implanted with calipered KA and PCL retention without over-tensioning the flexion space.

Bioimpedance Measurement of Knee Injuries using Bipolar Electrode Configuration

Currently, there is no suitable solution for the point-of-care of knee injuries. A potential portable and low-cost technique for accessing and monitoring knee injuries is bioimpedance measurement. This study validated the feasibility of the bipolar electrode configuration for knee bioimpedance measurements with two electrodes placed on a fixed pair of knee acupuncture locations called Xiyan. Then, the study collected 82 valid samples to investigate the relationship between bioimpedance and knee injuries, among whom 45 patients, each with one healthy knee and one injured knee, and 37 individuals all with healthy knees. The self-contrast results indicated that knee injuries caused a reduction of bioimpedance of the knee by about 5% on average, which was detectable at around 100 kHz (p ≈ 0.001). Furthermore, the results analyzed by principal component analysis and support vector machines show that the detection sensitivity can reach 91.11% using the leave-one-out cross-validation.

Restoring the Patient’s Pre-Arthritic Posterior Slope Is the Correct Target for Maximizing Internal Tibial Rotation When Implanting a PCL Retaining TKA with Calipered Kinematic Alignment

Introduction: The calipered kinematically-aligned (KA) total knee arthroplasty (TKA) strives to restore the patient’s individual pre-arthritic (i.e., native) posterior tibial slope when retaining the posterior cruciate ligament (PCL). Deviations from the patient’s individual pre-arthritic posterior slope tighten and slacken the PCL in flexion that drives tibial rotation, and such a change might compromise passive internal tibial rotation and coupled patellofemoral kinematics. Methods: Twenty-one patients were treated with a calipered KA TKA and a PCL retaining implant with a medial ball-in-socket and a lateral flat articular insert conformity that mimics the native (i.e., healthy) knee. The slope of the tibial resection was set parallel to the medial joint line by adjusting the plane of an angel wing inserted in the tibial guide. Three trial inserts that matched and deviated 2°> and 2°< from the patient’s pre-arthritic slope were 3D printed with goniometric markings. The goniometer measured the orientation of the tibia (i.e., trial insert) relative to the femoral component. Results: There was no difference between the radiographic preoperative and postoperative tibial slope (0.7 ± 3.2°, NS). From extension to 90° flexion, the mean passive internal tibial rotation with the pre-arthritic slope insert of 19° was greater than the 15° for the 2°> slope (p < 0.000), and 15° for the 2°< slope (p < 0.000). Discussion: When performing a calipered KA TKA with PCL retention, the correct target for setting the tibial component is the patient’s individual pre-arthritic slope within a tolerance of ±2°, as this target resulted in a 15–19° range of internal tibial rotation that is comparable to the 15–18° range reported for the native knee from extension to 90° flexion.

Evaluation of Patellar Dimension and Bristol Index in Asian Population: An MRI Study

Introduction: Restoration of patellar thickness is pivotal during a total knee arthroplasty (TKA). This study aims to evaluate the patellar dimension and Bristol Index of patellar width to thickness (BIPWiT) using magnetic resonance imaging (MRI) in Asian population.Methods: 101 MRI scans of young adults with normal patellofemoral joint (PFJ) age 17-40 were evaluated from January 2019 to December 2020. Exclusion criteria included patella-femoral pathology and degenerative joint disease. Data of gender, body height and weight were obtained from physical examination, while patella height, width and thickness were obtained using MRI measurement. Descriptive analysis was used to get the mean and standard deviation of patella dimension, whereas correlation between patella thickness with patella width and length were analysed using Pearson correlation and BIPWiT ratio was obtained by dividing the patellar width and patellar thickness. Results: Mean patellar length was 30.06 ± 2.94 (29.48-30.64); patellar width was 44.13 ± 4.44 (43.26-45.01); and patellar thickness was 23.89 ± 2.33 (23.43-24.35). Patellar dimension in male were significantly larger compared to female (P < 0.001). However, there was no difference in cartilage thickness between male and female (P = 0.305). There was strong correlation between patellar width and patellar thickness (r = 0.66; P < 0.001) with BIPWiT ratio of 1.85 ± 0.15.Conclusion: BIPWiT of 1.8:1 between patellar width and patellar thickness was recommended as a guide for patellar thickness restoration during TKA. There is no difference of patellar dimension between Asian and Western population in a healthy knee.Level of Evidence: Level III

Recovery of preoperative absolute knee extension and flexion strength after ACL reconstruction

Background The recovery of muscle function after an Anterior Cruciate Ligament (ACL) reconstruction is most commonly reported as limb-to-limb differences using the Limb Symmetry Index (LSI), which is not free from limitations. The purpose of this study was to compare the proportion of patients who recover their Preoperative Absolute Muscle Strength (PAMS) 8 and 12 months after ACL reconstruction with the proportion of patients who recover their symmetrical knee strength. A secondary aim was to assess the relationship between psychological Patient-Reported Outcomes (PROs) and recovering PAMS at 8 and 12 months after ACL reconstruction and rehabilitation. Method Preoperative, 8- and 12-month results from quadriceps and hamstring strength tests and PROs for 117 patients were extracted from a rehabilitation registry. Individual preoperative peak torques from strength tests were compared with results from the 8- and 12-month follow-ups respectively. Patients were defined as having recovered their PAMS upon reaching 90% of their preoperative peak torque for both quadriceps and hamstring strength. Patients were defined as having recovered their LSI upon reaching a value ≥90% when comparing the results for their injured knee with those of their healthy knee. Correlations between the recovery of PAMS and PROs at 8 and 12 months were analyzed. Results There was no difference in the proportion of patients who recovered their PAMS compared with patients who recovered their LSI. In all, 30% and 32% of the patients who recovered their LSI had not recovered their PAMS at 8 months and 12 months respectively. In the patients who had recovered their PAMS, 24% and 31% had not recovered their symmetrical LSI at 8 months and 12 months respectively. There was no significant correlation between the recovery of PAMS and psychological PROs. Conclusion The use of both PAMS and LSI provides more detailed information on the recovery of muscle strength after ACL reconstruction. The recovery of PAMS was not correlated with psychological traits, which implies that both PROs and PAMS are important when evaluating patients after ACL reconstruction. Trial registration This trial was not registered.

Patellotrochlea Index in Normal Healthy Knees

Patella alta is a common and significant abnormality responsible for many patellofemoral joint-related conditions. Many methods of patella height measurements are described; however, patellotrochear index (PTI) is the most logical method as it measures the direct relation between patella and trochlea. The aim of this study is to investigate PTI in normal healthy asymptomatic volunteers to understand the patellofemoral relation in normal knees. Twenty-five healthy volunteers underwent magnetic resonance imaging (MRI) scans of both knees. Two observers independently measured PTI on two different occasions at 6-week interval. Statistical analysis was performed to identify intra- and interobserver correlation between two observers and the mean value of PTI. Agreement analysis was performed according to Bland and Altman. Comparisons of means were made using paired t-tests. The mean age of 25 healthy volunteers was 21.28 years (19–23) with a male:female ratio of 14:11. The overall mean PTI value of all observations was 36.8% and pooled standard deviation (SD) 11.5%. Intraclass correlation (ICC) testing showed “good” interobserver ICC between two observers for PTI for both first (0.80) and second (0.84) set of measurements. There was “excellent” intraobserver correlation for two sets of measurements of PTI made by each first (0.96) and second (0.91) observer. Intraobserver repeatability for PTI was ± 0.07 and ± 0.1, respectively, for the first and second observer. Interobserver repeatability for PTI was ± 0.159 and ± 0.133, respectively, for the first and second set of measurements. Analysis of individual measurements of patella and trochlear articular cartilage revealed that the largest repeatability values were for trochlea measurements. The study reports that the average PTI in asymptomatic healthy knee utilizing current clinical MRI scanning conditions is 36.8%. This provides surgeons with a gold standard normal PTI value, which can serve as a target value in clinical diagnosis as well as surgical correction of patella height. There is good to excellent intra- and interobserver correlation with limited variability in assessing patella height using PTI on MRI scan.