Biocompatibility Evaluation of PEO-treated Magnesium Alloy Implants Placed in Rabbit Femur Condyle Notches and Paravertebral Muscles

Background: Magnesium alloys have been receiving much attention for use in biodegradable metal implants because of their excellent mechanical properties and biocompatibility. However, their rapid breakdown and low bioactivity can cause the implant to lose mechanical integrity before the bone is completely healed. Moreover, hydrogen gas released during degradation can significantly delay the tissue regeneration process. To solve the instability of magnesium alloys, Zn and Ca can be added to improve the mechanical properties and biocompatibility. One other way to improve the mechanical properties of Mg is plasma electrolytic oxidation (PEO), which provides a dense, thick ceramic-like coating on the Mg surface. In this study, high-purity Mg was selected as the control, and Mg-1wt%Zn-0.1wt%Ca alloy and PEO-treated Mg-1wt%Zn-0.1wt%Ca alloy were selected as the test materials; the results of radiographic and histological analyses of their biocompatibility are reported herein. Materials and method: Nineteen New Zealand white rabbits were used in the study. Rod-bars (Ø2.7x13.6mm) were placed on both paravertebral muscles, and cannulated screws (Ø2.7x10mm) were placed on both femur condyle notches. Each animal was implanted in all four sites. X-rays were taken at 0, 2, 4, 8, and 12 weeks, micro-CT, and live-CT were taken at 4, 8, and 12 weeks. At weeks 4, 8, and 12, individuals representing each group were selected and sacrificed to prepare specimens for histopathological examination. Result: The results confirm that in vivo, Mg-1wt%Zn-0.1wt%Ca alloy had higher corrosion resistance than high-purity Mg and safely degraded over time without causing possible side effects (foreign body or inflammatory reactions, etc.). In addition, PEO treatment of Mg-1wt%Zn-0.1wt%Ca alloy had a positive effect on fracture recovery by increasing the bonding area with bone. Conclusion: Our results suggest that PEO treatment of Mg-1wt%Zn-0.1wt%Ca alloy can be a promising biomaterials in the field of various clinical situations such as orthopedic and maxillofacial surgerys.

Percutaneous cryoablation of chondroblastoma and osteoblastoma in pediatric patients

Background To review the safety and efficacy of percutaneous cryoablation for the treatment of chondroblastoma and osteoblastoma in the pediatric and adolescent population. Materials and methods A retrospective review from 2016 to 2020 was performed to evaluate clinical and imaging response to percutaneous cryoablation in 11 symptomatic patients with diagnosis of chondroblastoma and osteoblastoma treated from two pediatric hospitals with at least 12-month follow-up. Technical success (correct needle placement and potential full coverage of the tumor with the planned ablation zone) and clinical success (relief of the symptoms) were evaluated. The primary objective was to alleviate pain related to the lesion(s). Immediate and late complications were recorded. Patients were followed in clinic and with imaging studies such as MRI or CT for a minimum of 6 months. Results A total of 11 patients were included (mean 14 years, age range 9–17; male n = 8). Diagnoses were osteoblastoma (n = 4) and chondroblastoma (n = 7). Locations were proximal humerus (n = 1), femur condyle (n = 1), and proximal femur (n = 1) tibia (n = 3), acetabulum (n = 3), thoracic vertebra (n = 1) and lumbar vertebra (n = 1). Cryoablation was technically successful in all patients. Clinical success (cessation of pain) was achieved in all patients. No signs of recurrence were observed on imaging follow-up in any of the patients. One of the patients developed periprocedural right L2–L3 transient radiculopathy as major immediate complication. Conclusions Percutaneous image-guided cryoablation can be considered potentially safe and effective treatment for chondroblastoma and osteoblastoma in children and adolescents.

Ideal Donor Site for Osteochondral Autografting of the Distal Femur Using Radius of Curvature: A 3-Dimensional High-Resolution Scanner Comparison

Objective To compare radius of curvature (RoC) of distal femur osteochondral autograft transfer (OAT) donor sites from the intercondylar notch and trochlear ridge with recipient sites on the distal and posterior condyles and evaluate differences between recipient sites. Design Nineteen cadaveric femurs were scanned with a 3-dimensional high-resolution sensor. Donor regions included the lateral (LTR) and medial trochlear ridges (MTR), and the lateral (LICN) and medial intercondylar notch (MICN). Recipient regions analyzed were the distal medial (DMFC), posterior medial (PMFC), distal lateral (DLFC), and posterior lateral femur condyle (PLFC). Six-millimeter OAT grafts were simulated, and average RoC of all regions was compared using an analysis of variance. Post hoc testing was performed using Fisher’s least significant difference. Results We found no significant differences in RoC of the LICN compared with all 4 recipient sites ( P = 0.19, 0.97, 0.11, and 0.75 for DLFC, PLFC, DMFC, and PMFC, respectively) or the LTR and MTR to the posterior condyles (LTR vs. PLFC and PMFC; P = 0.72, 0.47, MTR vs. PLFC and PMFC P = 0.39, 0.22, respectively). Significant differences were found for RoC of the MICN compared with each recipient site ( P < 0.001) and between distal and posterior femoral condyles (DLFC vs. PLFC, P = 0.016; DMFC vs. PMFC, P = 0.023). Conclusion The LICN is the ideal donor option for all recipient sites on the femoral condyles with respect to RoC of 6-mm OAT plugs. The MTR and LTR were acceptable donor sources for the posterior condyles, while the MICN was a poor match for all recipient sites. Additionally, the distal femur condyle and posterior femur condyle have different RoCs.

Diagnostic Value of 3.0T MRI in Cartilage Injury Grading of Knee Osteoarthritis

Objective: At present, the grading diagnosis of knee osteoarthritis is mostly subjective evaluation, and lack of quantitative criteria, which brings some difficulty to diagnosis. To solve this problem, this study selected easily quantifiable indicators, such as cartilage thickness, cartilage volume and signal value, and analyzes their application value in grading diagnosis of cartilage injury by observing their change characteristics under MRI. Methods: Clinical data were collected from 54 patients with osteoarthritis of the knee (KOA) and 12 healthy volunteers, including 27 males and 39 females; age 38–63 years, with an average age of 47 ± 6.9 years. A total of 110 knee joints were tested, including 86 affected and 24 healthy joints. MRI data were collected, including patella, medial and lateral femoral condyle, medial and lateral tibial condyle, and for grading. The results were compared with those of arthroscopy to analyze the consistency of the two diagnostic methods. The 110 knee joints were divided into 5 groups according to the arthroscopic grading (0–IV grade), and compare the differences of cartilage thickness, cartilage volume and signal value under MRI among groups. Result: Among them, in terms of MRI grading, there were 15 cases of I grade, 21 cases of II grade, 26 cases of III grade, and 24 cases of IV grade. In terms of arthroscopy grading, there were 16 cases of I grade, 23 cases of II grade, 25 cases of III grade, and 22 cases of IV grade. The kappa value of the two diagnostic methods was 0.91, with high consistency (P < 0.01). According to the results of arthroscopic grading diagnosis and analysis of the corresponding MRI data, it was found that the average thickness of normal articular cartilage in the patella, lateral tibia condyle, medial tibia condyle, lateral femur condyle, medial femur condyle is gradually thinning, and the thickness of articular cartilage in each part gradually thinned with the increase of injury grade. The difference between I grade and 0 grade was not statistically significant, and except for that, among other groups there were statistically significant (P < 0.01); The volume of normal articular cartilage decreased from medial femoral condyle, lateral femoral condyle, patella, lateral tibial condyle and medial tibial condyle in turn, and the volume decreased gradually with the increase of injury grade. Except for the difference between I grade and 0 grade, there were statistical significance between other groups (P < 0.01); signal value of normal articular cartilage decreased from medial tibial condyle, lateral femur condyle, medial femur condyle, lateral tibial condyle and patella in turn. Signal value increased with the increase of injury grade. Except for the difference between III grade and IV grade, there were statistical significance between other groups (P < 0.01). Conclusion : MRI grading of cartilage injury in knee osteoarthritis is highly consistent with arthroscopy, with high accuracy. In MRI grading, reference to cartilage thickness, cartilage volume and signal value can effectively improve the diagnosis rate.

Remodeling Capacity of Femoral Bone Defect by POP-CHA Bone Substitute: A Study in Rats’ Osteoclast (First Series of POP-based Bone Graft Improvement)

Reconstruction of large bone defects caused by trauma, excision of tumors, and congenital malformations can be very difficult to perform. Bone engineering offers an option to improve bone reconstruction procedures. This interdisciplinary field applies the principles of biology and engineering to the development of functional substitutes for damaged bone. Our research aimed to find the ideal scaffold for bone regeneration, focusing on Calcium and Phosphate combination. In this study, Plaster of Paris (POP) was combined with CHA and implanted in femoral condyles of rats. According to the experimental result, it can be concluded that there was no significant difference in response to the implantation of POP and POP-CHA in Sprague Dawley rat femur condyle (p<0.05). It can be stated that both POP-CHA and POP shows similar trait in bone healing.

Differences in Quantitative Architecture of Sciatic Nerve May Explain Differences in Potential Vulnerability to Nerve Injury, Onset Time, and Minimum Effective Anesthetic Volume

Background In sciatic nerve (SN) blocks, differences are seen in risk of nerve damage, minimum effective anesthetic volume, and onset time. This might be related to differences in the ratio neural:nonneural tissue within the nerve. For the brachial plexus, a higher proximal ratio may explain the higher risk for neural injury in proximal nerve blocks. A similar trend in risk is reported for SN; however, equivalent quantitative data are lacking. The authors aimed to determine the ratio neural:nonneural tissue within SN in situ in the upper leg. Methods From five consecutive cadavers, the region between the sacrum and distal femur condyle was harvested and frozen. Using a cryomicrotome, consecutive transversal sections (interval, 78 mum) were obtained and photographed. Reconstructions of SN were made strictly perpendicular to its long axis in the midgluteal, subgluteal, midfemoral, and popliteal regions. The epineurial area and all neural fascicles were delineated and measured. The nonneural tissue compartment inside and outside SN was also delineated and measured. Results The amount of neural tissue inside the epineurium decreased significantly toward distal (midfemoral/popliteal region) (P &lt; 0.001). The relative percentage of neural tissue decreased from midgluteal (67 +/- 7%), to subgluteal (57 +/- 9%), to midfemoral (46 +/- 10%), to popliteal (46 +/- 11%). Outside the SN, the adipose compartment increased significantly toward distal (P &lt; 0.007). Conclusion In SN, the ratio neural:nonneural tissue changes significantly from 2:1 (midgluteal and subgluteal) to 1:1 (midfemoral and popliteal). This suggests a higher vulnerability for neurologic sequelae in proximal SN, and may explain differences observed in minimum effective anesthetic volume and onset time between proximal and distal SN blocks.

On the Kinematic Modeling and the Parameter Estimation of the Human Knee Joint

This paper presents some results on the modeling and the parameter estimation of the human knee joint. Based on the geometric characteristics of the femur condyle and the tibia plateau, a part of femoro-tibial joint model includes an involute-on-plane submodel. Data recorded by camera type device are used to analyze the kinematic characteristics of the knee joint and to estimate the corresponding submodel parameters. Experimental results are presented and the model is further validated.