Cementing technique for total knee arthroplasty in cadavers using a pastry bone cement.

BACKGROUND: In cemented primary total knee arthroplasty (TKA), aseptic loosening remains a major cause for failure. Cementing techniques and characteristics of a chosen cement play a key role for good fixation and implant survival. A pastry bone cement was developed to facilitate the cement preparation and to rule out most of preparation-associated application errors. The pastry bone cement was compared to a conventional polymethyl methacrylate cement in a TKA setting. METHODS: Standardized implantations of total knee endoprostheses were performed in bilateral knee cadavers to investigate handling properties, variables of cement application, working time, and temperature development. Mechanical aspects and cementation quality were assessed by pull-out trials and microscopic interface analysis. RESULTS: Both cements expressed similar characteristics during preparation and application, only the curing time of the pastry cement was about 3 min longer and the temperature peak was lower. Fractures of the conventional cement specimens differed from the pastry cement specimens in the tibial part, while no differences were found in the femoral part. Penetration depth of the pastry cement was similar (tibia) or deeper (femur) compared to the conventional cement. CONCLUSIONS: The pastry cement facilitates the feasibility of cemented TKA. The pre-clinical tests indicate that the pastry bone cement fulfills the requirements for bone cement in the field of knee arthroplasty. A clinical trial is needed to further investigate the approach and ensure patient safety.

Systematic effects of femoral component rotation and tibial slope on the medial and lateral tibiofemoral flexion gaps in total knee arthroplasty.

PURPOSE: To quantify the effects of the systematic internal and external femoral component rotations and tibial slope on the medial and lateral tibiofemoral gaps in total knee endoprostheses. METHODS: Nineteen knee cadaver specimens with an intact ligament apparatus were fixed in a custom frame, facilitating physiological flexion motion. Virtual total knee arthroplasty (TKA) was performed on three-dimensional models obtained from computed tomography â€‹scans (0° and 90° flexions) with systematically altered femur rotations and tibial slopes. RESULTS: Both the femur rotation and the tibial slope influenced the medial and lateral tibiofemoral flexion gaps (p â€‹< â€‹0.001), and the effects differed between the medial and lateral sides (p â€‹< â€‹0.001). The medial tibiofemoral flexion gap increased by 2.90 â€‹± â€‹0.34 â€‹mm and decreased by 2.66 â€‹± â€‹0.26 â€‹mm for 7° external and internal femur component rotations, respectively (both with p â€‹< â€‹0.001). The lateral tibiofemoral flexion gap decreased by 3.11 â€‹± â€‹0.31 â€‹mm and increased by 3.29 â€‹± â€‹0.33 â€‹mm for 7° external and internal femur component rotations, respectively (both with p â€‹< â€‹0.001). CONCLUSION: For established surgical methods, we recommend a neutral femur rotation for a 0° tibial slope and a 3° external femur rotation for a tibial slope of 9-10°. The translational potential of this research shows that while the rotation of the femoral component in extension has no effect on the gap size, owing to the axis of rotation being perpendicular to the gap, for a 90° flexion, we not only observe differences in the gap size between the medial and lateral â€‹but also unequal differences on either side depending on the inward or outward rotation. The main reason for this is the position of the axis of rotation, which is not precisely half way between the lateral and medial contact points. The results show that rotation of the femoral component always creates an unbalanced flexion gap. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The article points out the differences in the tibiofemoral gap in total knee endoprostheses due to the systematic internal and external femoral component rotation. While in lower leg extension there are no differences seen, in 90° knee-flexion there are unequal differences within the medial and lateral compartment that show a mathematical relationship towards the femoral compartment rotation which needs to be intraoperatively considered.

The adaption of the bony microstructure of the human glenoid cavity as a result of long-term biomechanical loading.

Structural arrangements of the bony microstructure of a joint through adaptational processes are thought to be determined by the biomechanical demands and its changes. Pursuing this theory of "form follows the biomechanical function", the load distribution of the glenoid cavity, as it is mirrored in its mineralization pattern, should link not only to its thickness distribution, but also will have an impact onto the trabecular network below. To prove and confirm this hypothesis, we analysed the mineral distribution in correlation to the subchondral bone plates thickness and the distribution of architectural parameters of the trabecular network below. Our findings clearly state an inhomogeneous but regular and reproducible mineral distribution pattern in respect to the biomechanical demands and a thickness of the subchondral bone plate which shows a significant correlation (78-93%). As for the trabecular network below, the distribution of the analysed parameters also revealed an inhomogeneous distribution with a regular pattern in correlation to the biomechanical impact. We found distinctive maxima of material distribution and stability (bone volume 79%, plate-like architecture 77%) situated below areas of high long-term load intake. With increasing depth, the trabecular network administers the expression of each structural parameter following the fact that the strain energy gets more and more evenly distributed and changes from a high degree of differentiation just beneath the SBP to a more equal distribution within the deeper areas. After all, the biomechanical situation of a joint directly influences the bony formation of the subchondral bone plate and the trabecular network below.

Comparison of knee joint orientation in clinically versus biomechanically aligned computed tomography coordinate system.

BACKGROUND: Preoperative planning of total knee arthroplasty is usually performed using knee-centred computed tomography (CT) data sets. The disadvantage of these data sets is having no account of the biomechanical axis of the lower extremity, known as Mikulicz line. It aligns the femoral head to the middle of the talocrural joint. For optimal prosthesis arrangement, the knee CT data set must therefore be brought in congruency with this line of loading to achieve the best results and eliminate rotational malalignments.This study aims to establish a relation between the knee-centred clinical coordinate system (CCS) and a biomechanical coordinate system (BCS) based on the Mikulicz line. METHODS: CT data sets of 45 lower extremities were evaluated. Using VG Studio Max, a visualisation and measurement software program; each CT data set was aligned according to the CCS and BCS. After superimposing both the aligned data sets, the deviations of both coordinate systems in all three planes were measured with the centre of the knee defined as the origin. RESULTS: For the coronal plane, the CCS was demonstrated to be 2.54° in adduction compared to the BCS [standard deviation (SD) = 1.8°]. In sagittal view, the CCS was demonstrated to be 0.3° retroversed (SD = 3.27°). Finally, the deviation in the axial plane showed an outward rotation of 3.39° (SD = 1.99°). The alignment as well as the measurements demonstrated high intraobserver and interobserver reproducibility. CONCLUSION: Both coordinate systems can be established in knee-centred CT data sets in a reproducible manner. Clearly, the CCS differs significantly from the BCS describing the biomechanical axis, but mathematical-based adaptations and corrections can be performed. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The findings of this study allow a mathematical conversion of a knee CT to the biomechanical axis of the leg.

Osteoarthritis alters the patellar bones subchondral trabecular architecture.

Following the principles of "morphology reveals biomechanics," the cartilage-osseous interface and the trabecular network show defined adaptation in response to physiological loading. In the case of a compromised relationship, the ability to support the load diminishes and the onset of osteoarthritis (OA) may arise. To describe and quantify the changes within the subchondral bone plate (SBP) and trabecular architecture, 10 human OA patellae were investigated by CT and micro-CT. The results are presented in comparison to a previously published dataset of 10 non-OA patellae which were evaluated in the same manner. The analyzed OA samples showed no distinctive mineralization pattern in regards to the physiological biomechanics, but a highly irregular disseminated distribution. In addition, no regularity in bone distribution and architecture across the trabecular network was found. We observed a decrease of material as the bone volume and trabecular thickness/number were significantly reduced. In comparison to non-OA samples, greatest differences for all parameters were found within the first mm of trabecular bone. The differences decreased toward the fifth mm in a logarithmic manner. The interpretation of the logarithmic relation leads to the conclusion that the main impact of OA on bony structures is located beneath the SBP and lessens with depth. In addition to the clear difference in material with approximately 12% less bone volume in the first mm in OA patellae, the architectural arrangement is more rod-like and isotropic, accounting for an architectural decrease in stability and support. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1982-1989, 2017.

Computed Tomographic Evaluation of Joint Geometry in Patients With End-Stage Ankle Osteoarthritis.

BACKGROUND: Deformation of the talus and the distal tibia can be frequently observed during ankle joint osteoarthritis (OA). The aim of this study was to objectify these morphologic changes. We hypothesized that a flattening of the talus and a broadening of the distal tibia surface occurs in end-stage OA of the ankle joint. METHODS: Twenty-seven computed tomography (CT) ankle joint examinations of unilateral ankle OA were matched by sex and age with 27 CT examinations of healthy ankle joints. Three-dimensional reformatting and measurements were performed with geometry analysis software. The following parameters were assessed: sagittal radius of the talus, talus height, and mediolateral and anteroposterior width of the distal tibial joint surface. RESULTS: Medial, midsagittal, and lateral sagittal arc radii of osteoarthritic tali were significantly larger compared to tali of controls. There was a statistically significant difference in the height of the osteoarthritic talar dome in the medial and in the lateral frontal segment and in the medial central segment compared to tali of controls. The anteroposterior width and the sagittal curvature of the distal tibia was significantly larger in OA ankles than in the control group. The mediolateral measurements were comparable across both groups. CONCLUSION: Flattening of the talus appears to be more pronounced in the frontal aspect of the talus. The distal tibia broadens anteroposteriorly. These findings may contribute to better understanding of ankle OA development. LEVEL OF EVIDENCE: Level III, retrospective comparative cohort study.

Transcutaneous pleural biopsy with a retrograde forceps: a novel approach.

PURPOSE: Pleural biopsies are commonly performed to investigate the cause of exudative pleural effusion. Biopsy needles (e.g. Abrams needle, Cope needle) are traditionally used to perform the biopsy. However, certain complications such as pneumothorax and haemothorax have been described. We present a technique utilizing a novel retrograde forceps, which could improve the simplicity and lower the complication rate of performing closed pleural biopsies. DESCRIPTION: A retrograde forceps (Retroforceps, Karl Storz, Tuttlingen, Germany) was used to perform 20 transcutaneous pleural biopsies in a cadaver thorax under thoracoscopical control. Video documentation of the procedure from outside and inside the thorax was performed. The surgeon performing the biopsy was blinded to the thoracoscopical view. After the removal of the forceps, it was checked whether biopsy material was retrieved. The video material was retrospectively used to confirm whether the biopsy was taken from the pleura parietalis. EVALUATION: Biopsy material was retrieved in 19 out of 20 biopsy attempts. Video material confirmed that the biopsy was taken from the pleura parietalis in all cases. CONCLUSIONS: Using a retrograde biopsy forceps is a simple and practicable procedure suitable for clinical application. This technique could potentially reduce the incidence of pneumothorax.

Functional and Structural Details about the Fabella: What the Important Stabilizer Looks Like in the Central European Population.

The posterolateral corner of the knee accommodating the fabella complex is of importance in orthopaedic surgery. Unfortunately, there is a lack of data in literature for clinical routine. Therefore, we investigated the fabella's characteristics, biomechanical nature, and present histologic details. Of special interest were the fabella's occurrence and position, calcium concentration as long-term load intake indicator, and the histology. Within our analysis, fabellae were found in 30.0% of all datasets, located on the upper part of the posterolateral femoral condyle. The region of fabella contact on this condyle showed a significantly lower calcium concentration than its surroundings. Histologically, the fabella showed no articular cartilage but a clearly distinguishable fabellofibular ligament that consisted of two bundles: one, as already described in literature inserted at the fibular tip, and another part newly described on the top of the lateral meniscus. In its role of stabilizing the soft tissue structures of the posterolateral knee, the fabella seems to serve as suspension for the ligaments evolving from its base. Even though a joint formation of any kind is unlikely, the presence of a fabella needs to be kept in mind during knee examination and any surgical procedures.

Insight into the 3D-trabecular architecture of the human patella.

The subchondral bone plate (SBP), a dynamic component of the osteochondral unit, shows functional adaptation to long-term loading by distribution of the mineral content in a manner best serving the mechanical demands. Since the received joint-load is transmitted into the trabecular system, the spongy bone also exhibits differences in strain energy density which models it for optimal support. To evaluate the regional variations in trabecular architecture, in accordance with the density distribution of the SBP revealing its long-term load intake, CT- and µCT-datasets of ten physiologic patellae were analysed for defined parameters of bony structure. For the SBP, the density distributions as well as area measurements were used. The trabecular architecture was described using parameters of bone morphology comprising the first 5mm (examined in 1mm steps) below the SBP. The obtained measurements are: Bone volume fraction (BV/TV); Bone surface density (BS/TV); Trabecular number (Tb.N); Trabecular separation (Tb.Sp); Trabecular thickness (Tb.Th); structure model index (SMI); and the Degree of anisotropy (DA). The evaluated architectural parameters varied within the trabecular system and showed an inhomogeneous distribution pattern. It proved to be distinctive with maxima of material and stability situated below areas of the highest long-term load intake. With increasing depth, the pattern of distribution was persistent but lessened in intensity. The parameters significantly correlated with the density distribution of the SBP within the first and second millimetres. With increasing depth down to the fifth millimetre, the coefficients of correlation decreased for all values. The trabecular network adapts to its mechanical needs and is therefore not homogenously built. Dependent upon the long-term load intake, the trabecular model optimizes the support with significant correlation to the density distribution of the SBP.

Mineral density and penetration strength of the subchondral bone plate of the talar dome: high correlation and specific distribution patterns.

The subchondral bone plate plays an important role in stabilizing the osteochondral joint unit and in the pathomechanism of osteochondral lesions and osteoarthritis. The objective of the present study was to measure the mineral density distribution and subchondral bone plate penetration strength of the talar dome joint facet to display and compare the specific distribution patterns. Ten cadaver specimens were used for computed tomography (CT) scans, from which densitograms were derived using CT-osteoabsorptiometry, and for mechanical indentation testing from which the penetration strength was obtained. Our results showed 2 different distribution patterns for mineral density and penetration strength. Of the 10 specimens, 6 (60%) showed bicentric maxima (anteromedially and anterolaterally), and 4 (40%) showed a monocentric maximum (either anteromedially or anterolaterally). A highly significant correlation (p < .0001) for both methods confirmed that the mineral density relied on local load characteristics. In conclusion, the biomechanical properties of the subchondral bone plate of the talar dome joint facet showed specific distribution patterns. CT-osteoabsorptiometry is a reliable method to display the mineral density distribution noninvasively. We recommend CT-osteoabsorptiometry for noninvasive analysis of the biomechanical properties of the subchondral bone plate in osteochondral joint reconstruction and the prevention and treatment of osteoarthritis and osteochondral lesions.

The glenohumeral joint - a mismatching system? A morphological analysis of the cartilaginous and osseous curvature of the humeral head and the glenoid cavity.

BACKGROUND: Radial mismatch, glenohumeral conformity ratios and differences between cartilaginous and osseous radii highly depend on the measured plane. The comparison of cartilaginous radii between humeral head and glenoid in different planes provides new information to understand the degree of conformity during abduction of the upper limb. METHODS: To investigate the radii, CT-images in soft-tissue kernel of 9 specimen were analysed using an image visualization software. Statistical analysis of the obtained data was performed using the t-test. RESULTS: Measurements of the radii in the glenoid revealed a significantly larger radius for bone than cartilage, whereas for the humeral head the opposite was the case. Highest ratios for cartilage in the transverse plane were found in the inferior and central areas of the joint surface, whereas the smallest ratios were found in the superior area. The radial mismatch varied between 0.1 mm and 13.6 mm, depending on the measured plane. CONCLUSIONS: The results suggest that in abduction, the cartilaginous guidance of the humeral head decreases. This might permit the humeral head an anterior-posterior shifting as well as superior-inferior translation. Surgical reconstruction of the normal glenohumeral relationships necessitates precise information about the glenohumeral morphology to ensure proper sizing and correct placement of prosthetic components and osteochondral allografts.

Thickness distribution of the glenohumeral joint cartilage: a quantitative study using computed tomography.

PURPOSE: Among late signs like sclerosis, cysts and osteophytes, alteration of cartilage is a common problem in osteoarthritis. To detect abnormal states in the glenohumeral joint, the physiologic distribution of the cartilage thickness must be known, which will allow physicians to better advise patients. High-resolution computed tomography (CT) data in soft tissue kernel provide highly accurate quantitative results and are a useful method to determine the geometrical situation of the glenohumeral joint. The objective of this study was to characterize the distribution of the thickness of the glenohumeral joint cartilage using CT. METHODS: To investigate the distribution of thickness of the joint cartilage, CT images in soft tissue kernel of nine specimens were analyzed using image visualization software. Statistical analysis of the obtained data was performed using the ANOVA test. RESULTS: Results showed different patterns in the glenoid cavity than in humeral head. Cartilage thickness in all glenoids showed maxima in the inferior and anterior portion, whereas central areas are covered with the thinnest cartilage layer. Maximum cartilage thickness in the humeral head was found in the central and superior parts. CONCLUSION: We could show that the distribution of cartilage thickness in the glenohumeral joint is not homogenous and that there exist several reproducible patterns. Evaluation of cartilage thickness in the glenohumeral joint is of high interest in basic and clinical research.

The subtalar and talonavicular joints: a way to access the long-term load intake using conventional CT-data.

PURPOSE: The aim of this study was to investigate the distribution of density of the subchondral bone plate within the articular surfaces of the subtalar and talonavicular joint regarding to its mineralisation and to verify whether a correlation to the mechanical bone strength exists. METHODS: A total of 21 cadaverous lower leg specimens were investigated. Computed tomography osteo-absorptiometry (CT-OAM) was used to display the mineralisation of the subchondral bone plate analysing its density. The mechanical strength was measured by means of indentation testing. The distribution pattern was analysed regarding their dissemination with the main focus on number and location of their maxima. The correlation of both parameters was evaluated by linear regression. RESULTS: The mineralisation and the mechanical strength were not distributed homogenously throughout the articular surfaces but showed unique and reproducible patterns. The range of absolute values for density and strength varied in between the samples and joint surfaces, but the number and location of the maxima evaluated by both methods showed to be concurring. The coefficient of correlation of both datasets ranged from 0.76 to 0.95 (median 0.88) and showed a linear dependency. CONCLUSIONS: Density distribution and mechanical strength of the subchondral bone plate are significantly associated and can be seen as a mirror of the long-term load intake of a joint. It can be concluded that CT-OAM as a tool to visualize subchondral bone plate density distribution regarding to its mineralisation can be used to indirectly gain information about joint biomechanics in vivo by the use of conventional CT-data.

The human hip joint and its long-term load intake--how x-ray density distribution mirrors bone strength.

The aim of this study was to gain information about the topographical distribution of the mechanical strength of the subchondral bone plate of the hip joint and evaluate the correlation to its density distribution. Our intention was to describe a method of visualising and monitoring the long-term load intake of the hip using conventional CT-data in a way which might be applied in clinical practice. We examined the lunate surface of the acetabulum (facies lunata) and femoral head in 25 cases, looking at the density of the subchondral bone plate by computed tomography osteoabsorptiometry (CT-OAM) and determined its mechanical strength by indentation testing using an osteo-penetrometer. The resulting distribution patterns were matched and statistically analysed, showing an inhomogeneous but regular and reproducible distribution of mineralisation and mechanical strength throughout the joint surface. Maximal density was found anterosuperiorly and near the rim of the facies lunata and in the superior area of the femoral head. For each specimen a correlation of density and strength (r(2) = 0.77 - 0.97) was found (p<0.01). The density distribution pattern shown by CT-OAM allows conclusions to be drawn about the distribution of strength and therefore the long term load intake within the subchondral bone plate of the hip. Using conventional CT-data, the method can be used in the clinical setting for evaluation and monitoring.

Density and strength distribution in the human subchondral bone plate of the patella.

PURPOSE: The aim of this study was to map the strength distribution of the human patella and correlate it to the subchondral bone plate density obtained by means of computed tomographyosteoabsorptiometry (CT-OAM). METHODS: Measurements were performed at 34 standardized points on each patella. The mineralization patterns of the subchondral bone plate of 20 patellae were displayed with the help of CT-OAM. False-coloured distribution patterns for our measurements were generated. The mechanical strength was determined at the same points by indentation testing. RESULTS: We showed that neither the density nor the mechanical strength is distributed homogeneously but exhibited regular, reproducible distribution patterns which mirror long-term stress distribution in articular surfaces. A direct correlation was found between both parameters in the subchondral bone plate. CONCLUSION: The correlation of density and mechanical strength makes CT-OAM a valuable tool to assess and monitor changes in the strength of the subchondral bone plate in vivo.

Computer tomographic evaluation of talar edge configuration for osteochondral graft transplantation.

To successfully surgically reconstruct osteochondral lesions of the talus, the exact three-dimensional (3D) configuration of the upper articular surface of the talus has to be respected. We assessed the talar geometry by measuring the coronal and sagittal talar edge radius and the frontal talar profile in multiplanar reconstructions of computer tomographic (CT) studies of 79 patients (83 feet) with a healthy ankle joint. An image visualization software designated for coordinate measurement was used to perform the measurement. In the coronal plane, the mean lateral talar edge radius was 4.0 mm and the medial 4.5 mm. In the sagittal planes the mean lateral talar edge radius was 20.3 mm, the radius of the sulcus 20.7 mm and the medial talar edge radius 20.4 mm. The talus showed a concave shape in coronal cuts. These results show a significant difference between medial and lateral talar edge configuration in coronal planes. The measurements of the lateral and medial sagittal radius and the mid-sagittal radius in the sulcus tali show no statistically significant difference. The depth of the talar sulcus shows no correlation to age or sex. Different sizes of custom-made tissue-engineered grafts according to the location of the osteochondral lesion at the talus are needed for exact surgical reconstruction of the anatomy. Osteochondral lesions are three dimensional; therefore, a 3D preoperative planning tool by CT scan or MRI is mandatory.