Pig Knee Joints Research Articles

Comparative Analysis of Hyaline Cartilage Characteristics and Chondrocyte Potential for Articular Cartilage Repair.

This study aimed to compare the histological, biochemical, and mechanical characteristics of hyaline cartilage in different regions and evaluate the potential of chondrocytes extracted from each region as donor sources for articular cartilage repair. The cartilage tissues of the femoral head and knee joint, ribs, nasal septum, thyroid, and xiphoid process of adult Bama pigs were isolated for histological, biochemical, and mechanical evaluation and analysis. The corresponding chondrocytes were isolated and evaluated for proliferation and redifferentiation capacity, using biochemical and histological analysis and RT-PCR experiments. Compared with articular cartilage, non-articular hyaline cartilage matrix stained more intensely in Safranin-O staining. Glycosaminoglycan and total collagen content were similar among all groups, while the highest content was measured in nasal septal cartilage. Regarding biomechanics, non-articular cartilage is similar to articular cartilage, but the elastic modulus and hardness are significantly higher in the middle region of costal cartilage. The chondrocytes extracted from different regions had no significant difference in morphology. Hyaline cartilage-like pellets were formed in each group after redifferentiation. The RT-PCR results revealed similar expressions of cartilage-related genes across the groups, albeit with lower expression of Col2 in the xiphoid chondrocytes. Conversely, higher expression of Col10 was observed in the chondrocytes from the rib, thyroid, and xiphoid cartilage. This study provides valuable preclinical data for evaluating heterotopic hyaline cartilage and chondrocytes for articular cartilage regeneration. The findings contribute to the selection of chondrocyte origins and advance the clinical translation of technology for cartilage regeneration.

MegaPro, a clinically translatable nanoparticle for in vivo tracking of stem cell implants in pig cartilage defects.

Rationale: Efficient labeling methods for mesenchymal stem cells (MSCs) are crucial for tracking and understanding their behavior in regenerative medicine applications, particularly in cartilage defects. MegaPro nanoparticles have emerged as a potential alternative to ferumoxytol nanoparticles for this purpose. Methods: In this study, we employed mechanoporation to develop an efficient labeling method for MSCs using MegaPro nanoparticles and compared their effectiveness with ferumoxytol nanoparticles in tracking MSCs and chondrogenic pellets. Pig MSCs were labeled with both nanoparticles using a custom-made microfluidic device, and their characteristics were analyzed using various imaging and spectroscopy techniques. The viability and differentiation capacity of labeled MSCs were also assessed. Labeled MSCs and chondrogenic pellets were implanted into pig knee joints and monitored using MRI and histological analysis. Results: MegaPro-labeled MSCs demonstrated shorter T2 relaxation times, higher iron content, and greater nanoparticle uptake compared to ferumoxytol-labeled MSCs, without significantly affecting their viability and differentiation capacity. Post-implantation, MegaPro-labeled MSCs and chondrogenic pellets displayed a strong hypointense signal on MRI with considerably shorter T2* relaxation times compared to adjacent cartilage. The hypointense signal of both MegaPro- and ferumoxytol-labeled chondrogenic pellets decreased over time. Histological evaluations showed regenerated defect areas and proteoglycan formation with no significant differences between the labeled groups. Conclusion: Our study demonstrates that mechanoporation with MegaPro nanoparticles enables efficient MSC labeling without affecting viability or differentiation. MegaPro-labeled cells show enhanced MRI tracking compared to ferumoxytol-labeled cells, emphasizing their potential in clinical stem cell therapies for cartilage defects.

Feasibility of Electromagnetic Knee Imaging Verified on Ex-Vivo Pig Knees.

The potential of electromagnetic knee imaging system verified on ex-vivo pig knee joint as an essential step before clinical trials is demonstrated. The system, which includes an antenna array of eight printed biconical elements operating at the band 0.7-2.2 GHz, is portable and cost-effective. Importantly, it can provide daily monitoring and onsite real-time examinations imaging tool for knee injuries. Six healthy hind legs from three dead adult pigs were removed at the hip and suspended in the developed system. For each pig, the right- and left-knee were scanning sequentially. Then ligament tear was emulated by injecting distilled water into the left knee joint of each pig for early (5 mL water) and mid-stage (10 mL water) injuries. The injured left knees were re-scanned. A modified multi-static fast delay, multiply and sum algorithm (MS-FDMAS) is used to reconstruct imaging of the knee. All knee's connective tissues, such as anterior and posterior cruciate ligaments (ACL, PCL), lateral and medial collateral ligaments (LCL, MCL), tendons, and meniscus, are extracted from a healthy hind leg along with collected synovial fluid. The extracted tissues and fluid were characterized and modelled as their data are not available in the literature, then imported to build an equivalent model for pig knee of 1 mm3 resolution in a realistic simulation environment. The obtained results proved potential of the proposed system to detect ligament/tendon tears. The proposed system has the potential to detect early knee injuries in a realistic environment. Contactless EM knee imaging system verified on ex-vivo pig joints confirms its potential to reconstruct knee images. This work lays the groundwork for clinical EM system for detecting and monitoring knee injuries. (EM).

Mechanoporation enables rapid and efficient radiolabeling of stem cells for PET imaging

Regenerative medicine uses the patient own stem cells to regenerate damaged tissues. Molecular imaging techniques are commonly used to image the transplanted cells, either right after surgery or at a later time. However, few techniques are fast or straightforward enough to label cells intraoperatively. Adipose tissue-derived stem cells (ADSCs) were harvested from knee joints of minipigs. The cells were labeled with PET contrast agent by flowing mechanoporation using a microfluidic device. While flowing through a series of microchannels, cells are compressed repeatedly by micro-ridges, which open transient pores in their membranes and induce convective transport, intended to facilitate the transport of 68Ga-labeled and lipid-coated mesoporous nanoparticles (MSNs) into the cells. This process enables cells to be labeled in a matter of seconds. Cells labeled with this approach were then implanted into cartilage defects, and the implant was imaged using positron emission tomography (PET) post-surgery. The microfluidic device can efficiently label millions of cells with 68Ga-labeled MSNs in as little as 15 min. The method achieved labeling efficiency greater than 5 Bq/cell on average, comparable to 30 min-long passive co-incubation with 68Ga-MSNs, but with improved biocompatibility due to the reduced exposure to ionizing radiation. Labeling time could also be accelerated by increasing throughput through more parallel channels. Finally, as a proof of concept, ADSCs were labeled with 68Ga-MSNs and quantitatively assessed using clinical PET/MR in a mock transplant operation in pig knee joints. MSN-assisted mechanoporation is a rapid, effective and straightforward approach to label cells with 68Ga. Given its high efficiency, this labeling method can be used to track small cells populations without significant effects on viability. The system is applicable to a variety of cell tracking studies for cancer therapy, regenerative therapy, and immunotherapy.

Magnetization‐Switchable Implant System to Target Delivery of Stem Cell‐Loaded Bioactive Polymeric Microcarriers

Various magnetic microcarrier systems capable of transporting cells to target lesions are developed for therapeutic agent-based tissue regeneration. However, the need for bioactive molecules and cells, the potential toxicity of the microcarrier, and the large volume and limited workspace of the magnetic targeting device remain challenging issues associated with microcarrier systems. Here, a multifunctional magnetic implant system is presented for targeted delivery, secure fixation, and induced differentiation of stem cells. This magnetic implant system consists of a biomaterial-based microcarrier containing bioactive molecules, a portable magnet array device, and a biocompatible paramagnetic implant. Among biomedical applications, the magnetic implant system is developed for knee cartilage repair. The various functions of these components are verified through in vitro, phantom, and ex vivo tests. As a result, a single microcarrier can load ≈1.52 ng of transforming growth factor β (TGF-β1) and 3.3 × 103 of stem cells and stimulate chondrogenic differentiation without extra bioactive molecule administration. Additionally, the implant system demonstrates high targeting efficiency (over 90%) of the microcarriers in a knee phantom and ex vivo pig knee joint. The results show that this implant system, which overcomes the limitations of the existing magnetic targeting system, represents an important advancement in the field.

Differential proteomic analysis of tibial subchondral bone from male and female guinea pigs with spontaneous osteoarthritis.

A proteomic study on the tibial subchondral bone in guinea pigs with spontaneous osteoarthritis was performed to investigate the molecular alterations that occur in early osteoarthritis. A total of 132 healthy Hartley guinea pigs (aged 1 month; 66 female and 66 male) were randomly divided into 11 groups of six. Changes in articular cartilage and tibial subchondral bone were assessed using macroscopic examinations and micro-computed tomography. iTRAQ-integrated liquid chromatography-tandem mass spectrometry was used to identify differentially altered proteins in the tibial subchondral bone between 1- and 3-month-old guinea pigs, which were then validated using western blotting. A gradual progression of cartilage degeneration was observed in the knee joints of the subject animals from 5-11 months. With aging, the tibial subchondral trabecular bone acquired more plate-like and less anisotropic properties, with increased bone mineral density, bone volume, trabecular thickness and numbers. The proteomic study identified 138 and 113 proteins significantly differentially expressed between 3- and 1-month old guinea pigs in both the male and female animals, respectively. Western blotting confirmed the increased expression of osteoblast-associated protein S100 calcium-binding protein A8 (S100A8) and the deregulated expression of osteoclast-associated proteins coronin 1A (CORO1A) and T-cell immune regulator 1 (TCIRG1) in the 3-month old guinea pigs in comparison to the 1-month old guinea pigs. Spontaneous cartilage degeneration in the knee joints of male Hartley guinea pigs tended to be more serious compared with the females during the development of osteoarthritis. Together, the results suggest that osteoblast-associated protein S100A8 and osteoclast-associated proteins CORO1A and TCIRG1 are potentially key regulators of early osteoarthritic development in tibial subchondral bone.

Biochemical and Morphological Abnormalities of Subchondral Bone and Their Association with Cartilage Degeneration in Spontaneous Osteoarthritis.

This study aims to investigate how biochemical composition in subchondral bone (SB) relates to the sulfated glycosaminoglycan (sGAG) content of articular cartilage (AC) in the knee joint of guinea pigs from the early to moderate osteoarthritis (OA). Male Dunkin Hartley strain guinea pigs were grouped according to age (1, 3, 6, and 9months, with 10 guinea pigs in each group). The biochemical properties of the AC and SB in the tibial plateau of the guinea pigs were determined through histology and Raman spectroscopy, respectively. Furthermore, the microstructures of the SB were investigated using micro-computed tomography (micro-CT) and histology. Increased thickness and bone mineral density (BMD) and decreased porosity were observed in the subchondral plate (SP) with the progression of spontaneous OA, accompanied by a decreasing trend in sGAG integrated optical density (IOD) of AC. Compared with the changes in the microstructure of subchondral bone, the content of sGAG was more correlated to the changes in the mineral/matrix ratio of subchondral bone. The mineralization of the matrix was significantly correlated to the content of sGAG compared with crystallinity/maturity and Type B carbonate substitution. PO43- ν1/Amide III was more correlated to the content of sGAG than PO43- ν1/Amide I, PO43- ν1/CH2 wag during the progression of spontaneous osteoarthritis. This study demonstrated that the mineralization of subchondral bone plays a crucial role in the pathogenesis of OA. Future studies may access to the mineralization of subchondral bone in addition to its microstructure in the study for pathogenesis and early diagnosis of osteoarthritis.

Repair of articular cartilage defect using adipose-derived stem cell-loaded scaffold derived from native cartilage extracellular matrix.

The purpose of this study was to investigate the feasibility of adipose-derived stem cells (ADSCs) as the seed cells of cartilage tissue engineering. ADSCs were isolated from adipose tissue that was harvested under sterile conditions from the inguen fold of porcines and cultured in vitro. Acellular cartilage extracellular matrix (ACECM) scaffolds of pigs were then constructed. Moreover, inflammatory cells, as well as cellular and humoral immune responses, were detected using hematoxylin and eosin staining staining, immunohistochemical staining, and western blot analysis. The results showed that the cartilage complex constructed by ADSCs and ACECM through tissue engineering successfully repaired the cartilage defect of the pig knee joint. The in vivo repair experiment showed no significant difference between chondrocytes, ADSCs, and induced ADSCs, indicating that ADSCs do not require in vitro induction and have the potential for chondrogenic differentiation in the environment around the knee joint. In addition, pig-derived acellular cartilage scaffolds possess no obvious immune inflammatory response when used in xenotransplantation. ADSCs may serve as viable seed cells for cartilage tissue engineering.

STUDY ON MECHANICAL PROPERTIES OF TOTAL KNEE ARTICULAR CARTILAGE UNDER DIFFERENT LOADING RATES

Knee joint is the main weight bearing tissue of human body, also it is one of the prone parts of the clinical disease. Under different sports conditions, knee joint was loaded at different forms. In this study, the changes of average contact pressure, peak contact pressure, contact area and pressure-sharing regions were researched using the intact and defect pig knee joints under different loading rates and loads, including fast rates and large loads. These data were measured and recorded by usage of the sensor plate that placed between the unilateral meniscus and the femur cartilage during loading process. As for the intact cartilage samples, the average contact pressure and peak contact pressure of the femur cartilage increase with the loading rate, while the contact area is contrast to it. As for defect cartilage samples, it not only emerged stress concentration on the edge of the defect and pressure distribution in joint cavity was different with intact cartilage samples, but also the main bearing region was transferred from the femur cartilage-meniscus contact area to the femur cartilage-tibial cartilage contact area at different loading forms. In different loading stages, the pressure-sharing regions between the cartilage and the meniscus also changes. Different loading rates, different loads and defects will change the mechanical states of the knee joint. In loading forms, the mechanical condition may cause or aggravate damnification of the knee joint cartilage. Therefore, this study is beneficial for promoting and perfecting the research of mechanical properties of knee joint cartilage and provides a theoretical basis for the prevention and treatment of knee cartilage injury.

Storage solution containing hydrogen improves the preservation effect of osteochondral allograft.

As an ideal antioxidant and anti-apoptotic substance, hydrogen (H2) has protective effects on many isolated organs, such as the heart, lung and kidney. In this study, we explore whether H2 improves the preservation effect of osteochondral allograft by adding it to Dulbecco's Modified Eagle Medium (DMEM) solution during the tissue culture stage. The osteochondral allograft apparatus was used to harvest 60 pieces of cylindrical allografts (l = 10mm, d = 6mm) cartilage in the lateral loading area of the femoral condyle from the pig knee joint in the aseptic condition, and the grafts were randomly divided into 4 groups: Control group (DMEM solution without hydrogen); H-1 group (DMEM solution with hydrogen concentration of 0.2mmol/L); H-2 group (DMEM solution with hydrogen concentration of 0.4mmol/L); and H-3 group (DMEM solution with hydrogen concentration of 0.8mmol/L). The chondrocyte viability, histological changes (hematoxylin and eosin staining, Safranine O staining, and collagen type II immunohistochemistry staining) and biomechanical properties (Young's modulus) of the osteochondral allograft were investigated after 28days' storage. The chondrocyte viability and proteoglycan and collagen type II contents in the H-3 and H-2 groups were higher than that in the Control and H-1 groups, and the H-3 group had the highest values. However, significant differences were not observed between the four groups based on Young's modulus. Hydrogen as an additive to the DMEM solution improved the preservation effect of osteochondral allograft. The preservation effect of hydrogen occurred in a concentration-dependent manner.

Depiction of a knee joint of pig by means of synchrotron X-ray diffraction enhanced imaging with a Laue-type analyzer

Depiction of a knee joint of pig by means of synchrotron X-ray diffraction enhanced imaging with a Laue-type analyzer

Comparison of Standard Suture vs Barbed Suture for Closing the Porcine Knee Joint: Evaluation of Biomechanical Integrity and Permeability

BackgroundThis study aimed to compare the biomechanical strength and permeability of barbed vs traditional suture for closure of the porcine knee joint. MethodsThis study used Duroc pig knee joints. For each specimen, a 5-cm medial parapatellar arthrotomy was performed with the knee at 30° of flexion. We closed the arthrotomy wound using barbed suture (size 1/0 V-Loc 180) or traditional suture (size 1/0 PDS II). Specimens were divided into a PDS II (n = 9) and a V-Loc group (n = 9) for biomechanical testing, and a PDS II (n = 9) and a V-Loc group (n = 9) for permeability testing. In biomechanical testing, a continuous load was applied and the wound was pulled apart at 50 mm/min. We compared the maximum load under which each suture type could maintain wound closure. In permeability testing, the knee joints were flexed and extended for 200 cycles at 0.5 Hz from 0° to 120° of flexion. A tube was fixed in the articular cavity of the specimen and connected to a 1.5-m high water capsule. The time taken to wound effusion was compared. ResultsThere was no significant difference between the mean load at initial failure for PDS II (424 ± 192 N) vs V-Loc (471 ± 100 N, P = .529), or between the mean time until effusion for PDS II (6.8 ± 3.4 seconds) vs V-Loc (5.5 ± 2.5 seconds, P = .390). ConclusionStandard and barbed suture had similar wound holding strength and permeability. The barbed suture was as stable as traditional suture.

Age-related modulation of angiogenesis-regulating factors in the swine meniscus.

An in‐depth knowledge of the native meniscus morphology and biomechanics in its different areas is essential to develop an engineered tissue. Meniscus is characterized by a great regional variation in extracellular matrix components and in vascularization. Then, the aim of this work was to characterize the expression of factors involved in angiogenesis in different areas during meniscus maturation in pigs. The menisci were removed from the knee joints of neonatal, young and adult pigs, and they were divided into the inner, intermediate and outer areas. Vascular characterization and meniscal maturation were evaluated by immunohistochemistry and Western blot analysis. In particular, expression of the angiogenic factor Vascular Endothelial Growth Factor (VEGF) and the anti‐angiogenic marker Endostatin (ENDO) was analysed, as well as the vascular endothelial cadherin (Ve‐CAD). In addition, expression of Collagen II (COLL II) and SOX9 was examined, as markers of the fibro‐cartilaginous differentiation. Expression of VEGF and Ve‐CAD had a similar pattern in all animals, with a significant increase from the inner to the outer part of the meniscus. Pooling the zones, expression of both proteins was significantly higher in the neonatal meniscus than in young and adult menisci. Conversely, the young meniscus revealed a significantly higher expression of ENDO compared to the neonatal and adult ones. Analysis of tissue maturation markers showed an increase in COLL II and a decrease in SOX9 expression with age. These preliminary data highlight some of the changes that occur in the swine meniscus during growth, in particular the ensemble of regulatory factors involved in angiogenesis.

'Iron accumulation' gene expression profile in obese hartley guinea pig knee joints is associated with more severe osteoarthritis

'Iron accumulation' gene expression profile in obese hartley guinea pig knee joints is associated with more severe osteoarthritis

Cartilage Imaging using HR Propagation-Based Phase-contrast CT in a Guinea Pig Knee Joint Model of Different Age Groups

Cartilage Imaging using HR Propagation-Based Phase-contrast CT in a Guinea Pig Knee Joint Model of Different Age Groups

Instruments for reproducible setting of defects in cartilage and harvesting of osteochondral plugs for standardisation of preclinical tests for articular cartilage regeneration.

BackgroundStandardisation is required in research, so are approval procedures for advanced therapy medical products and other procedures for articular cartilage therapies. The process of creating samples needs to be reproducible.The aim of this study was to design, create and validate instruments (1) to create reproducible and accurate defects and (2) to isolate samples in the shape of osteochondral cylinders in a quick, reliable and sterile manner.MethodsAdjustable instruments were created: a crown mill with a resolution of 0.05 mm and a front mill to create defects in articular cartilage and subchondral bone. The instruments were tested on knee joints of pigs from the slaughterhouse; 48 defects were created and evaluated. A punching machine was designed to harvest osteochondral plugs. These were validated in an in vivo animal study.ResultsThe instruments respect the desired depth of 0.5 and 1.5 mm when creating the defects, depending on whether the person using the instrument is highly experienced (0.451 mm; confidence interval (CI): 0.390 mm; 0.512 mm and 1.403 mm; CI: 1.305 mm; 1.502 mm) or less so (0.369 mm; CI: 0.297 mm; 0.440 mm and 1.241 mm; CI: 1.141 mm; 1.341 mm). Eighty samples were taken from knee joints of Göttingen Minipigs with this punching technique. The time needed for the harvesting of the samples was 7.52 min (±2.18 min), the parallelism of the sides of the cylinders deviated by −0.63° (CI: −1.33°; 0.08°) and the surface of the cartilage deviated from the perpendicularity by 4.86° (CI: 4.154°; 5.573°). In all assessed cases, a sterile procedure was observed.ConclusionsInstruments and procedures for standardised creation and validation of defects in articular cartilage and subchondral bone were designed. Harvesting of samples in the shape of osteochondral cylinders can now be performed in a quick, reliable and sterile manner. The presented instruments and procedures can serve as helpful steps towards standardised operating procedures in the field of regenerative therapies of articular cartilage in research and for regulatory requirements.

The morphology of the articular surfaces of biological knee joints provides essential guidance for the construction of functional knee endoprostheses.

In comparative examinations of kinematics of the knees of humans and pigs in flexional/extensional motion under compressive loads, the significant differential geometric essentials of articular guidance are elaborated to criticise the shaping of the articular surfaces of conventional knee-endoprostheses and to suggest constructional outlines that allow the endoprosthesis to adopt natural knee kinematics. Implantation is discussed with regard to the remaining ligamentous apparatus. Twelve fresh pig knee joints and 19 preserved human knee joints were moved into several flexional/extensional positions. In each joint, the tibia and femur were repeatably caught by metal plates. After removing all ligaments, the tibia and femur were again caught in these positions, and their points of contact were marked on both articular surfaces. Along the marker points, a thin lead wire was glued onto each surface. The positions and shapes of the four contact lines were mapped by teleradiography. All contact lines were found to be plane curves. The medial and lateral planes were parallel, thus defining the joint's sagittal plane. In the human knee, as compared to the lateral, the medial femoral contact line was always shifted anteriorly by several millimetres. The tibial contact curve was laterally convex and medially concave. In the pig knees, the lateral and medial contact lines were asymmetrically placed. Both tibial curves were convex. Both knees represent cam mechanisms (with one degree of freedom) that produce rolling of the articular surfaces during the stance phase. Implantation requires preservation of the anterior cruciate ligament, and ligamentous balancing is disadvantageous.

Construction of tissue engineering cartilage for the damaged load bearing section of pig knee-joint by CD44 monoclonal antibody-biotin-avidin binding technique

Objective To evaluate the effect of repairing cartilage defect using tissue engineering cartilage with CD44 monoclonal antibody-biotin-avidin (CBA) binding technique in vitro and in vivo.Methods The tissue engineering cartilages were designed and divided into 3 groups:general group,chitosan scaffold + chondrocyte group; biotin-avidin (BA) group,chitosan scaffold bound with BA + chondrocyte; CBA group,chitosan scaffold bound with CD44 monoclonal antibody-BA + chondrocyte.The levelthrough cartilage damages of load bearing sections were divided into four groups:group A,transplanted with the tissue engineering cartilage in the general group; group B,transplanted with the tissue engineering cartilage in the BA group; group C,transplanted with the tissue engineering cartilage in the CBA group;group D,transplanted with the autologous cartilage.Samples were taken after transplantation for 12 weeks,and estimated by Moran estimate system.The modulus of elasticity and rigidity of the samples were estimated by biomechanics method.The contents of collagen Ⅱ (col Ⅱ) and aggrecan were tested by Western blotting.The samples were stained with hematoxylin and eosin (HE),and TB dye,and the Wakitani scores were recorded.Results In the Moran estimate system,the score in group D was 4.48 ± 0.23,which showed no statistically significant difference from group C (P ＞ 0.05),but higher than in groups A and B,P ＜ 0.05.The modulus of elasticity in group D was (20.61 ± 2.02) mPa and the rigidity was (72.28 ±6.16) N/mm.The expression of col Ⅱ and aggrecan in group D was 1.59 ±0.14 and 1.44 ± 0.13 respectively,significantly higher than other groups,P ＜ 0.05.The histologic staining and Wakitani score revealed the more satisfactory repair effectiveness in group D.Conclusion The repair effect of tissue engineering cartilage constructed by the BA technique for the damaged load bearing section of pig knee-joint is more satisfactory than the general method.The effect,however,is much better when the tissue engineering cartilage is prepared by CD44 monoclonal antibody-BA binding technique.Though it cannot be equal to the autologous repair totally,the CD44 monoclonal antibody-BA binding technique can achieve nearly the same repair effect. Key words: CD44 monoclonal antibody; Biotin ; Adivin ; Tissue engineering; Cartilage damage

Three‐dimensional motion analysis of the patellar component in total knee arthroplasty by the image matching method using image correlations

In total knee arthroplasty (TKA), the patella is significantly associated with range of motion and gait performance. Currently, no highly accurate methods are available that can measure the 3D in vivo behavior of the TKA patellar component, as the component is made of x-ray-permeable ultra-high molecular weight polyethylene. Previously, we developed a computer simulation that matches CT scan and unidirectional radiographic images using image correlations, and applied it to kinematic studies of natural and TKA knees. The examination of the measurement accuracy for the patellar bone of a fresh-frozen pig knee joint yielded a root mean square error of 0.2 mm in translation and 0.2° in rotation. In this study, we recruited four patients who had a TKA and investigated 3D movements of the patellar component during squatting. We could visualize the patellar component using the position of the holes drilled for the component peg, and estimated and visualized the contact points between the patellar and femoral components. The principles and the utility of the simulation method are reported. This analytical method is useful for evaluating the pathologies and post-surgical conditions of the knee and other joints.

Total ankle arthroplasty: optimizing computed tomography imaging protocol

To evaluate parameters and positioning when imaging total ankle prostheses on computed tomography (CT). An ankle prosthesis implanted into a pig's knee joint underwent 16 different CT imaging protocols. Four defects were drilled around prosthesis components simulating periprosthetic osteolytic lesions. The specimen with the implant was imaged in four different orientations with the tibial stem parallel to the table and at 25, 45, and 90° angles to it. The protocol consisted of scanning at 100, 120, and 140kVp in every position with a pitch of 1.2. The scanning at 120kVp in every position was repeated with a pitch of 1.0. CT proved to be a reliable imaging modality when studying periprosthetic lesions adjacent to the ankle prosthesis when the tibial stem alignment was parallel to the table. When imaging at higher angles, metal artifacts distorted the image, making the analysis of periprosthetic bone structure unreliable. There were no statistically significant differences between different tube voltages or pitch in volume measurements of the osteolytic lesions. CT is a reliable imaging method to evaluate periprosthetic bone structure around ankle prostheses when orientation of the prosthesis and acquisition parameters is optimized.