PEGASOS - A New Linking Mechanism for Modular Osteosynthesis Plates in Minimally Invasive Acetabular Surgery

Background: Recently presented minimally invasive endoscopic surgical techniques demonstrated the feasibility of implanting standard osteosynthesis plates for pelvic fractures. The reconstruction and internal fixation of complex acetabular fractures is still challenging. The goal of this study is to introduce a divisible implant, with a positive-locking in situ linking mechanism for plate osteosynthesis, making it possible to stabilize large and complex acetabular fractures with involvement of the quadrilateral surface. Method: Standard implants were used to recreate a base design. Using computer aided design (CAD), a three-dimensional standard implant was divided into two parts, so they could be re-allocated in situ. A critical objective was to reduce the cross-section of each part (clearance gauge). To connect the separated parts in situ, a new linking mechanism (cone in cone) was created. The new construct also features self-stabilization, self-centering, reinforced positional movement and preloading effects. Results: A linking system for plate osteosynthesis was developed entitled PEGASOS ("Percutaneous Endoscopic Guided Acetabulum-Stabilizing Osteosynthesis System"). Endoscopic implantation and in-situ-linking could be performed in a human cadaver. Therefore, we could demonstrate, that buttressing the quadrilateral surface of the acetabulum could be performed minimally invasive using a divisible suprapectineal buttress plate. Conclusion: We created a linking mechanism to couple two plates in situ. This mechanism enables an extremely strong, positive-locking connection, whereas its geometric shape allows for different relative movements during the locking procedure, with a single screw.

Comparative assessment of the primary stability of Straumann® BLX implant design using an in-vitro sinus lift-simultaneous implant insertion model

Straumann ® BLX is a novel implant system, which has been proclaimed to provide an ideal primary stability in all types of bone. In the current study, the primary stability of Straumann ® BLX implant systems with Straumann ® tapered effect (TE) implants have been comparatively assessed in bovine ribs by using a simultaneous sinus elevation and implant insertion model. In the study group, BLX (4.0 x 12 mm), TE (4.1 x 12 mm), BLX (4,5 x 12 mm) and TE (4.8 x 12 mm) were placed in each bony window, which resembles sinus maxillaris. As a control, BLX and TE implants with same sizes were inserted into the proximal diaphysis of the bovine ribs. A total of 40 implant insertions were performed. The stability was measured with resonance frequence analysis. In the study group, TE implants of 4.8 mm showed significantly higher values compared to 4.5 mm BLX implants (p=0.116). However, BLX implants of 4.0 mm in the control group showed higher stability compared to TE with 4.0 mm diameter. (p=0.014). The primary stability of BLX implants in the control group was significantly higher compared to the experimental group in both widths (p=0.018 for BLX 4.0 and p=0.002 for BLX 4.5 respectively). The use of TE design with wide diameter in simultaneous implant placement with sinus lift could present higher ISQ values and might be more appropriate option for implant recipient sites with poor bone volume and quality. However, the advantage of BLX design in standard implant insertion protocols could be precious.

Guided Bilateral Transcanine Implant Placement and Implant-Supported Oral Rehabilitation in a Patient with Progressive Systemic Scleroderma

When faced with a situation where an impacted tooth is in the way of a planned implant, one approach to avoid an invasive surgical procedure and potential associated complications is to place a transcanine implant. The aim of this report was to add a new case of a transimpacted tooth dental implant placement to the existing international literature and to share our experience of transcanine implantation in the maxilla followed by implant prosthodontic rehabilitation of a patient with progressive systemic scleroderma. A 55-year-old woman attended our office for oral cavity assessment and treatment planning for complete oral rehabilitation. Digital planning software was used, and implants were positioned according to a surgical template in regions 13, 16, 23, and 26 (Straumann, Basel, Switzerland) with screw-retained metal-ceramic bridges. Placement of the dental implants through impacted canines and the creation of interfaces other than implant-bone interfaces did not lead to postoperative pain or implant failure. Clinically, overall healing was observed, and the implants were successfully used for implant-supported prosthodontic rehabilitation of the jaw. Within the limitations of this case report, transcanine implantation could represent a valuable alternative to standard implant protocols.

Growth modulation of angular deformities with a novel constant force implant concept-preclinical results

Purpose Varus-valgus deformities in children and adolescents are often corrected by temporary hemi-epiphysiodesis, in which the physis is bridged by an implant to inhibit growth. With standard implant solutions, the acting forces cannot be regulated, rendering the correction difficult to control. Furthermore, the implant load steadily increases with ongoing growth potentially leading to implant-related failures. A novel implant concept was developed applying a controlled constant force to the physis, which carries the potential to avoid these complications. The study aim was to proof the concept in vivo by analyzing the effect of three distinct force levels on the creation of varus deformities. Methods The proposed implant is made of a conventional cerclage wire and features a twisted coil that unwinds with growth resulting in an implant-specific constant force level. The proximal medial tibial physes of 18 lambs were treated with the implant and assigned to three groups distinct by the force level of the implant (200 N, 120 N, 60 N). Results The treatment appeared safe without implant-related failures. Deformity creation was statistically different between the groups and yielded on average 10.6° (200 N), 4.8° (120 N) and 0.4° (60 N) over the treatment period. Modulation rates were 0.51°/mm (200 N), 0.23°/mm (120 N) and 0.05°/mm (60 N) and were constant throughout the treatment. Conclusion By means of the constant force concept, controlled growth modulation appeared feasible in this preclinical experiment. However, clinical trials are necessary to confirm whether the results are translatable to the human pathological situation.

Do Morphological Changes in the Anterior Mandibular Region Interfere with Standard Implant Placement? A Cone Beam Computed Tomographic Cross-Sectional Study

Objective. To determine the morphological features in the anterior mandibular region, the presence of lingual foramen and canal dimensions in Saudi subjects that would interfere with standard implant placement. Methods. CBCT scans of patients seeking implant treatment were examined. Based on the dentition status, patients were categorized into edentulous (group I) and dentulous (group I). On the panoramic view, the distance between the two mental foramina was divided into vertical segments of 10 mm width. In each segment, vertical bone height and buccolingual thickness at three levels (alveolar crest, 5 mm, and 10 mm apical to the crest) were assessed. The lingual foramen prevalence and canal features were assessed as well. Comparisons between the two groups regarding the assessed parameters were performed using the t-test. The percentage of edentulous mandibles with thickness <6 mm corresponding to the standard implant diameter was also calculated. Results. Following the inclusion and exclusion criteria, group I consisted of 45 subjects and group II comprised 26 subjects. Bone height and thickness at the crestal level were significantly less in edentulous (I) than dentate mandibles (II) ( P < 0.0001 ). The lingual foramen was detected in 90% of patients. In both groups, males had significantly greater mandibular height than females ( P = 0.02 and 0.005). At the crestal level, the thickness was <6 mm in 50% of the anterior mandibular segments. Conclusion. Half of the edentulous patients may receive normal size implants in the anterior interforaminal segments, while the other half will be limited to narrow implants (3.5 mm and less). The lingual foramen location, canal size, and position may represent another limitation for implant placement in that segment.

Variation of the femoral J-Curve in the native knee

The J-Curve in the native knee as well as the femoral component’s J-Curve after total knee arthroplasty are known to have a high influence on kinematics. Furthermore, the J-Curve’s shape affects ligament strain and tension and consequently already slight changes may strongly alter knee forces and stability. To optimize current implants’ J-Curve design with regard to the population’s morphology, information about the main sources of contour variation is necessary.In this study, a principal component analysis (PCA) was performed on the medial and lateral femoral J-Curves of 90 cadavers without history of osteoarthritis. The J-Curves’ mean shapes were further investigated by geometric parameter analysis and effect sizes were calculated for the first three principal components (PCs). In addition, a combined PCA for both sides was performed and evaluated qualitatively. The results were compared with the variation in standard implants’ J-Curve shape.The isolated PCA of medial and lateral J-Curves resulted in PCs involving changes in contour orientation, arc length, scaling and circularity. The combined PCA of both sides resulted in PCs comprising combinations of the individual variations together with changes in relative position. In contrast, the qualitative evaluation of J-Curves from 2 different standard implant systems revealed no visible changes in shape but only changes in size.Limitations of this study were the restriction to a 2-dimensional contour derivation and the sole consideration of the femoral contours. Nevertheless, the sagittal variability in the medial, lateral and combined femoral J-Curves should be considered in implant design.

Comparison of failure loads and compressive stress in Press on metal and Press on Y-TZP copings

Objective: The aim of the study was to assess the failure loads and compressive stresses among bilayered press on Y-TZP (POZ) and press on metal (POM) crowns with different core-veneer thickness. Methods: Thirty metal and Y-TZP copings were fabricated using CAD-CAM technology with specified thickness. All copings were veneered with ceramic materials using hot pressing technique, with 2mm and 2.5mm thickness. The different coping veneer thickness of crowns resulted in six study groups, including, POM: Coping/ veneer thickness of 0.7/2mm (Gp1), 0.7/2.5mm (Gp 2) and 1mm/2mm (Gp 3)- POZ: 0.7/2mm (Gp A), 0.7/2.5mm (Gp B) and 1mm/2mm (Gp C). Crowns were cemented to a standard implant analog and failure loads (FL) and compressive stress (CS) was ascertained by controlled load application in a universal testing machine. Data was analysed using ANOVA and multiple comparisons test. Results: The maximum FL were observed in the POM specimens with a C/V ratio of 1/2 (Group 3-1880.67± 256.78 N), however the lowest FL were exhibited by POZ crowns with 1/2 C/V ratio (Group C-611.89± 72.79 N). Mean FL and CS were significantly higher in POM compared to POZ crowns in respective groups. Increasing the coping-veneer thickness increased FL and CS among POM crowns. Increasing veneer and decreasing coping thickness improved FL and CS among POZ crowns. Conclusions: Press on metal specimen showed higher resistance to fracture than Press on Y-TZP specimens. Improved failure loads were observed in thin coping and thick veneers among Press on Y-TZP crowns. doi: https://doi.org/10.12669/pjms.36.7.2472 How to cite this:Vohra F, Shuwaish MB, Al-Deeb M, Alhamdan R, Alotaibi N, Abduljabbar T. Comparison of failure loads and compressive stress in Press on metal and Press on Y-TZP copings. Pak J Med Sci. 2020;36(7):---------. doi: https://doi.org/10.12669/pjms.36.7.2472 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Biofunctional Glycol-Modified Polyethylene Terephthalate and Thermoplastic Polyurethane Implants by Extrusion-Based Additive Manufacturing for Medical 3D Maxillofacial Defect Reconstruction

This work addresses the topic of extrusion-based additive manufacturing (filament-based material extrusion) of patient-specific biofunctional maxillofacial implants. The technical approach was chosen to overcome the shortcomings of medically established fabrication processes such as a limited availability of materials or long manufacturing times. The goal of the work was a successful fabrication of basic implants for defect reconstruction. The underlying vision is the implants’ clinic-internal and operation-accompanying application. Following a literature search, a material selection was conducted. Digitally prepared three-dimensional (3D) models dealing with two representative mandible bone defects were printed based on the material selection. An ex-vivo model of the implant environment evaluated dimensional and fitting traits of the implants. Glycol-modified PET (PETG) and thermoplastic polyurethane (TPU) were finally selected. These plastics had high cell acceptance, good mechanical properties, and optimal printability. The subsequent fabrication process yielded two different implant strategies: the standard implant made of PETG with a build-up rate of approximately 10 g/h, and the biofunctional performance implant with a TPU shell and a PETG core with a build-up rate of approximately 4 g/h. The standard implant is meant to be intraoperatively applied, as the print time is below three hours even for larger skull defects. Standard implants proved to be well fitting, mechanically stable and cleanly printed. In addition, the hybrid implant showed particularly cell-friendly behavior due to the chemical constitution of the TPU shell and great impact stability because of the crack-absorbing TPU/PETG combination. This biofunctional constellation could be used in specific reconstructive patient cases and is suitable for pre-operative manufacturing based on radiological image scans of the defect. In summary, filament-based material extrusion has been identified as a suitable manufacturing method for personalized implants in the maxillofacial area. A further clinical and mechanical study is recommended.

Distal Radius Fracture Fixation Devices and Their Radiographs

Background: Distal radius fractures are among the most common fractures encountered in orthopedic practices. If treated operatively, most implants are retained after the fracture heals unless there is hardware failure, limitation of wrist motion, pain, infection, tendon rupture, or tenosynovitis. Complications have been reported during hardware removal, including not knowing the exact implant prior to its removal. If a patient presents for plate removal to a surgeon who did not perform the initial fracture fixation, having a preoperative visual aid can help the treating surgeon choose the right instruments for their removal. Methods: To identify many of the available distal radius fixation devices, we searched the Internet and contacted local industry representatives. We also approached industry personnel at the commercial exhibit of a national hand society meeting to provide us with implants they manufacture. The implants were placed on the volar and dorsal aspects of sawbone models of the distal radius and in one case the radial styloid, using the screws, screwdrivers and accessories in the standard implant set and then posteroanterior and lateral x-rays of the implants were obtained. We created an atlas and a list of the screwdriver(s) used for each. Results: We obtained radiographs and photographs for 28 implants that were manufactured by 14 different companies. Two companies sent us radiographs and photographs placed on either a sawbone or cadaveric model. We found that 7 of the implants were outliers and could be identified easily on the x-rays, whereas 21 implants had similar design of shaft and distal components. Conclusions: To aid the orthopedic surgeon in their removal, we compiled a comprehensive list of most distal radius fixation devices on the market including plates and their corresponding screws and screwdrivers. The goal was to help the surgeon when removing the plate to identify the implant on radiographs.

Clinical and radiographic classification of implant supported prosthesis for edentulous patients

Relevance. In domestic and foreign professional literature there is a lack of aggregated consolidated data about immediate long span implant supported prosthesis which could be fundamental in making decision making process during the treatment planning stage, as well as at the estimation of quality of implant supported prosthetics. The aim of this study – the creation of a conceptual model of the standard implant prosthetics for edentulous patients.Materials and methods. A comprehensive examination and implantation prosthetics 382 patients aged 38 to 84 years (211 women, 171 men) with 582 implant supported prosthesis of various types, supporting on implants "Nobel Replace Select / Groove», «Nobel Parallel CC», «Nobel Speedy Groove», «Nobel Trefoil CC» (3775 implants). We have created a new clinical and radiographic classifcation of implant-supported prosthesis for edentulous patients.Result. As a result of the classifcation in the I (1-2 implants) class rallied 6.2% of implant supported prosthesis, to II class (3-4 implant, «TREFOIL» included) was assigned 19.2% of prostheses, to III class (5-6 implants) – 30.2% of replacement structures IV- to (7-10 implants) – 44%, and V – 0,3%. Meanwhile II, III, IV classes and I statistically revealed age differences.Conclusions: We have sorted out fve main classes, 8 subclasses and 18 groups with 34 subgroups of implant supported prosthesis based on the number of abutments, type of prosthesis, retention method and the presence of unilateral or bilateral cantilever.