Purpose
Early-onset degeneration of the knee is linked to genetics, overload, injury, and potentially, knee morphology. The purpose of this study is to explore the characteristics of the small medial ...femoral condyle, as a distinct knee morphotype, by means of a landmark-based three-dimensional (3D) analysis and statistical parametric mapping.
Methods
Sixteen knees with a small medial femoral condyle (SMC) were selected from a database of patients with distinct knee joint anatomy and 16 gender-matched knees were selected from a control group database. 3D models were generated from the medical imaging. After normalization for size, a set of pre-defined landmark-based parameters was analysed for the femur and tibia. Local shape differences were evaluated by matching all bone surfaces onto each other and comparing the distances to the mean control group bone shape.
Results
The small medial condyle group showed a significant association with medial compartment degeneration and had a 4% and 13% smaller medial condyle anteroposteriorly and mediolaterally, whereas the distal femur was 3% wider mediolaterally. The lateral condyle was 2% smaller anteroposteriorly and 8% wider mediolaterally. The complete tibial plateau was 3% smaller mediolaterally and the medial tibial plateau was 6% smaller.
Conclusion
A new knee morphotype demonstrated an increased risk for medial compartment degeneration and was differentiated from a healthy control group based on the following morphological characteristics: a smaller medial femoral condyle and medial tibial plateau, a wider lateral femoral condyle and a wider distal femur on a smaller tibial plateau. This pilot study suggests a role for the SMC knee morphotype in the multifactorial process of medial compartment degeneration.
Level of evidence
III
Background The aim of this study was to assess the influence of 3-dimensional (3D) preoperative planning and patient-specific instrument (PSI) guidance of glenoid component positioning on its ...inclination in total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA). Materials and methods Thirty-six shoulder arthroplasties (12 TSAs, 24 RSAs) were analyzed, of which 18 procedures (6 TSAs, 12 RSAs) were executed using preoperative 3D planning and patient-specific guides to position the central guide pin for glenoid component implantation. In 9 cases, the glenoid anatomy was severely distorted through wear or previous surgery. The inclination of the glenoid component was measured by 2 observers, using the angle between the glenoid baseplate and the floor of the supraspinatus fossa (angle β) on postoperative radiographs. Results For TSA, the average angle β was 74 ± 9 in the PSI group and 86 ± 12 in the non-PSI group; for RSA, the average angle β was 83 ± 7 in the PSI group and 90 ± 17 in the non-PSI group. Extreme angles β, which represent extreme values of glenoid component inclination, are more likely to occur in the non-PSI group than in the PSI group ( P < .001 for TSA; P = .02 for RSA). Conclusions The3D preoperative surgical planning and PSI guidance reduce variability in glenoid component inclination and avoid extreme inclination errors for TSA and RSA.
Purpose
The trochlear dysplastic femur has a specific morphotype previously characterised by not only dysplastic features of the trochlea but also by specific features of the notch and posterior ...femur. In this study the morphology of the tibia and patella was investigated to gain further insight in the complete geometrical complexity of the trochlear dysplastic knee.
Methods
Arthro-CT scan-based 3D models of 20 trochlear dysplastic and 20 normal knees were uniformly scaled and landmarks and landmark-based reference planes were created to quantify a series of morphometric characteristics of the tibia and patella.
Results
In the mediolateral direction, the 3D-analysis revealed a 3% smaller medial tibial plateau (30.4 ± 1.6 mm vs 31.5 ± 1.6 mm), a 3% smaller overall width of the tibial plateau (73.6 ± 2.0 mm vs 75.7 ± 2.0 mm), a 16% smaller medial facet (17.3 ± 2.2 mm vs 20.1 ± 1.3 mm) and a 4% smaller overall width of the patella (41.7 ± 2.5 mm vs 43.4 ± 2.3 mm) in trochlear dysplastic knees. In the anteroposterior direction, the lateral tibial plateau of trochlear dysplastic knees was 5% larger (37.2 ± 2.3 mm vs 35.5 ± 3.1 mm). A correlation test between the width of the femur and the width of the tibia revealed that trochlear dysplastic knees show less correspondence between the femur and tibia compared to normal knees.
Conclusion
Significant differences in the morphology of the tibial plateau and patella were detected between trochlear dysplastic and normal knees. Both in the trochlear dysplastic tibial plateau and patella a narrower medial compartment leads to a significant smaller overall mediolateral width. These findings are important for the understanding of knee biomechanics and the design of total knee arthroplasty components.
Level of evidence
III.
In this study presents materials and design optimization of clinically approved hydroxyapatite (HA) using extrusion based 3D printing process. The effect of various printing parameters including ...print speed, extrusion pressure, accuracy and infill density to produce defined porous structures is established using various techniques. Particularly Scanning Electron Microscopy, Micro Computed Tomography have been employed to study internal and external accuracy. Mechanical testing was employed to study the effect of porosity on compressive properties of 3D printed structures.
This study shows that, the infill density and shrinkage of 3D printed HA scaffolds post sintering have a linear relationship. Porosity and mechanical strength of 3D printed scaffolds depend on the infill density of the designed CAD file. Tailoring infill density also helps in altering mechanical properties in a predictable manner. Finally, a case study on hydroxyapatite printing of a patient specific bone graft demonstrates the ability of this material and technique to print complex porous structures created on CT-based anatomical bone models and pre-operative 3D planning, providing further promise for custom implant development for complex bony designs.
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•Extrusion based 3D printing was validated as the accurate and reliable method for hydroxyapatite scaffold manufacturing.•Infill density and shrinkage of 3D printed hydroxyapatite scaffolds follow a linear relationship.•It is possible to accurately predict % shrinkage of ceramic green bodies and rescale design files to optimise 3D printing•Comprehensive modulus of 3D printed scaffolds ranges from 33 - 200 MPa, comparable to human cortical bones (100 to 150 MPa)•Complex patient specific bone graft is 3D printed accurately from patients own CT scans
Purpose
The authors hypothesise that the trochlear dysplastic distal femur is not only characterised by morphological changes to the trochlea. The purpose of this study is to describe the ...morphological characteristics of the trochlear dysplastic femur in and outside the trochlear region with a landmark-based 3D analysis.
Methods
Arthro-CT scans of 20 trochlear dysplastic and 20 normal knees were used to generate 3D models including the cartilage. To rule out size differences, a set of landmarks were defined on the distal femur to isotropically scale the 3D models to a standard size. A predefined series of landmark-based reference planes were applied on the distal femur. With these landmarks and reference planes, a series of previously described characteristics associated with trochlear dysplasia as well as a series of morphometric characteristics were measured.
Results
For the previously described characteristics, the analysis replicated highly significant differences between trochlear dysplastic and normal knees. Furthermore, the analysis showed that, when knee size is taken into account, the cut-off values of the trochlear bump and depth would be 1 mm larger in the largest knees compared to the smallest knees. For the morphometric characteristics, the analysis revealed that the trochlear dysplastic femur is also characterised by a 10 % smaller intercondylar notch, 6–8 % larger posterior condyles (lateral–medial) in the anteroposterior direction and a 6 % larger medial condyle in the proximodistal direction compared to a normal femur.
Conclusions
This study shows that knee size is important in the application of absolute metric cut-off values and that the posterior femur also shows a significantly different morphology.
Three-dimensional planning based on computed tomography images of the malunited and the mirrored contralateral forearm allows preoperative simulations of corrective osteotomies, the fabrication of ...patient-specific osteotomy guides, and custom-made 3-dimensional printed titanium plates. This study aims to assess the precision and clinical outcome of this technique.
This was a prospective pilot study with 5 consecutive patients. The mean age at initial injury was 11 years (range, 4–16 years), and the mean interval from the time of injury to the time of corrective surgery was 32 months (range, 7–107 months). Patient-specific osteotomy guides and custom-made plates were used for multiplanar corrective osteotomies of both forearm bones at the distal level in 1 patient and at the middle-third level in 4 patients. Patients were assessed before and after surgery after a mean follow-up of 42 months (range, 29–51 months).
The mean planned angular corrections of the ulna and radius before surgery were 9.9° and 10.0°, respectively. The mean postoperative corrections obtained were 10.1° and 10.8° with corresponding mean errors in correction of 1.8° (range, 0.3°–5.2°) for the ulna and 1.4° (range, 0.2°–3.3°) for the radius. Forearm supination improved significantly from 47° (range, 25°–75°) before surgery to 89° (range, 85°–90°) at final review. Forearm pronation improved from 68° (range, 45°–84°) to 87° (range, 82°–90°). In addition, there was a statistically significant improvement in pain and grip strength.
This study demonstrates that 3-dimensional planned patient-specific guides and implants allow the surgeon to perform precise corrective osteotomies of complex multiplanar forearm deformities with satisfactory preliminary results.
Therapeutic V.
In malunion cases, restoration of anatomy is a key factor in obtaining a good functional outcome, but this can be technically very challenging.Three-dimensional printed bone models can further ...improve understanding of the malunion pattern.The use of three-dimensional (3D) computer planning, and the assembly of patient-specific instruments and implants, especially in complex deformities of the upper limb, allow accurate correction while reducing operation time, blood loss volume and radiation exposure during surgery.One of the major disadvantages of the 3D technique is the additional cost because it requires specific computer software, a dedicated clinical engineer, and a 3D printer.Further technical developments and clinical investigations are necessary to better define the added value and cost/benefit relationship of 3D in the treatment of complex fractures, non-unions, and malunions. Cite this article:
2019;4 DOI: 10.1302/2058-5241.4.180074.
Background Only a few articles describe the reproducibility and clinical feasibility of glenoid inclination measurements on conventional radiographs, and none of them validated their method in ...shoulder arthroplasty cases. From a clinical point of view, the angle measured between the supraspinatus fossa and the glenoid fossa line (angle β) appears to be the most interesting angle to assess glenoid inclination. This study aimed to validate the angle β in shoulder arthroplasty patients to facilitate the assessment of glenoid component inclination. Materials and methods Seventeen patients who underwent total or reverse shoulder arthroplasty were evaluated. The angle β was measured by 2 independent observers on postoperative radiographs and 3-dimensional (3D) models. The interobserver variability and accuracy of angle β were analyzed by calculating the intraclass correlation coefficient (ICC) and by generating Bland-Altman plots. Results The angle β showed a good interobserver variability (ICC = 0.971 for radiographs, ICC = 0.980 for 3D models) and a good agreement between the radiographic and 3D measurements (ICC = 0.904 for observer 1 and ICC = 0.908 for observer 2). Bland-Altman plots demonstrated that in 95% of the measurements on radiographs, the error will be <10. In the investigated population, 85% showed an error <6. Conclusion This study demonstrates that angle β can be measured on radiographs to assess glenoid component inclination in total and reverse shoulder arthroplasty, but clinicians and researchers should keep in mind that measurement errors of 10° may occur in a minority of cases.
Malunion is a common complication of distal radius fractures, especially those treated conservatively. In clinical studies, a significant correlation between anatomic reduction and wrist function has ...been shown. Corrective osteotomy is the preferred treatment for symptomatic cases, notwithstanding the technical challenges. The use of computer simulation improves pre-operative understanding of the three-dimensional deformity. Patient-specific surgical guides, based on precise pre-operative planning, lead to superior perioperative accuracy and reproducibility. The pre-operative planning and surgical technique of distal radius corrective surgery using three-dimensional computer technology are described in detail. The preliminary results demonstrate the excellent clinical and radiographic outcome of this technique.
Manual anatomical landmarking for morphometric knee bone characterization in orthopedics is highly time-consuming and shows high operator variability. Therefore, automation could be a substantial ...improvement for diagnostics and personalized treatments relying on landmark-based methods. Applications include implant sizing and planning, meniscal allograft sizing, and morphological risk factor assessment. For twenty MRI-based 3D bone and cartilage models, anatomical landmarks were manually applied by three experts, and morphometric measurements for 3D characterization of the distal femur and proximal tibia were calculated from all observations. One expert performed the landmark annotations three times. Intra- and inter-observer variations were assessed for landmark position and measurements. The mean of the three expert annotations served as the ground truth. Next, automated landmark annotation was performed by elastic deformation of a template shape, followed by landmark optimization at extreme positions (highest/lowest/most medial/lateral point). The results of our automated annotation method were compared with ground truth, and percentages of landmarks and measurements adhering to different tolerances were calculated. Reliability was evaluated by the intraclass correlation coefficient (ICC). For the manual annotations, the inter-observer absolute difference was 1.53 ± 1.22 mm (mean ± SD) for the landmark positions and 0.56 ± 0.55 mm (mean ± SD) for the morphometric measurements. Automated versus manual landmark extraction differed by an average of 2.05 mm. The automated measurements demonstrated an absolute difference of 0.78 ± 0.60 mm (mean ± SD) from their manual counterparts. Overall, 92% of the automated landmarks were within 4 mm of the expert mean position, and 95% of all morphometric measurements were within 2 mm of the expert mean measurements. The ICC (manual versus automated) for automated morphometric measurements was between 0.926 and 1. Manual annotations required on average 18 min of operator interaction time, while automated annotations only needed 7 min of operator-independent computing time. Considering the time consumption and variability among observers, there is a clear need for a more efficient, standardized, and operator-independent algorithm. Our automated method demonstrated excellent accuracy and reliability for landmark positioning and morphometric measurements. Above all, this automated method will lead to a faster, scalable, and operator-independent morphometric analysis of the knee.
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