Densitometric analysis of dental implant placement between flapless technique and the two-stage technique--a pilot study

Flapless technique is a surgical approach of implant placement without raising a mucoperiosteal flap. Such approach has many advantages: shorter surgical treatment, minimal bleeding, postoperative discomfort for the patient is reduced; possibility of immediate loading of the inserted implant, faster procedure of implant placement and by that less time is needed for the complete implant-prosthetic restoration. Purpose of this pilot study was radiographic assessment of flapless technique and determination of its clinical values in comparison with two-stage dental implant technique through computerized densitometric analysis. The sample consisted of 10 patients with missing teeth in the premolar region in the upper jaw. An implant was placed in that position. In the first group of 5 patients the implants were inserted with the flapless technique, and in the other group of 5 patients implant insertion was done with a two-stage technique. All inserted implants were loaded with metal-ceramic crowns 3 months after placement. The patients were followed for 18 months through clinical follow-ups and radiovisiographical (RVG) images made after 3, 12 and 18 months. After comparing the average densities, the results showed similar decrease of density in both groups, conventional two-stage technique showed 3.24 and flapless technique 1.23. It can be concluded that flapless technique in everyday clinical usage has the same result as the two-stage dental implant technique.     

The role of patient, surgical, and implant design variation in total knee replacement performance

Clinical studies demonstrate substantial variation in kinematic and functional performance within the total knee replacement (TKR) patient population. Some of this variation is due to differences in implant design, surgical technique and component alignment, while some is due to subject-specific differences in joint loading and anatomy that are inherently present within the population. Combined finite element and probabilistic methods were employed to assess the relative contributions of implant design, surgical, and subject-specific factors to overall tibiofemoral (TF) and patellofemoral (PF) joint mechanics, including kinematics, contact mechanics, joint loads, and ligament and quadriceps force during simulated squat, stance-phase gait and stepdown activities. The most influential design, surgical and subject-specific factors were femoral condyle sagittal plane radii, tibial insert superior-inferior (joint line) position and coronal plane alignment, and vertical hip load, respectively. Design factors were the primary contributors to condylar contact mechanics and TF anterior-posterior kinematics; TF ligament forces were dependent on surgical factors; and joint loads and quadriceps force were dependent on subject-specific factors. Understanding which design and surgical factors are most influential to TKR mechanics during activities of daily living, and how robust implant designs and surgical techniques must be in order to adequately accommodate subject-specific variation, will aid in directing design and surgical decisions towards optimal TKR mechanics for the population as a whole.     

Development of a statistical shape-function model of the implanted knee for real-time prediction of joint mechanics

Outcomes of total knee arthroplasty (TKA) are dependent on surgical technique, patient variability, and implant design. Non-optimal design or alignment choices may result in undesirable contact mechanics and joint kinematics, including poor joint alignment, instability, and reduced range of motion. Implant design and surgical alignment are modifiable factors with potential to improve patient outcomes, and there is a need for robust implant designs that can accommodate patient variability. Our objective was to develop a statistical shape-function model (SFM) of a posterior stabilized implanted knee to instantaneously predict joint mechanics in an efficient manner. Finite element methods were combined with Latin hypercube sampling and regression analyses to produce modeling equations relating nine implant design and six surgical alignment parameters to tibiofemoral (TF) joint mechanics outcomes during a deep knee bend. A SFM was developed and TF contact mechanics, kinematics, and soft tissue loads were instantaneously predicted from the model. Average normalized root-mean-square error predictions were between 2.79% and 9.42%, depending on the number of parameters included in the model. The statistical shape-function model generated instantaneous joint mechanics predictions using a maximum of 130 training simulations, making it ideally suited for integration into a patient-specific design and alignment optimization pipeline. Such a tool may be used to optimize kinematic function to achieve more natural motion or minimize implant wear, and may aid the engineering and clinical communities in improving patient satisfaction and surgical outcomes.     

Are angle-fixed implants with elastic properties advantageous for the internal fixation of proximal humerus fractures?]

There is a recent interest for the use of angle-fixed plates in the management of proximal humerus fractures. Rigid implants might be associated with an increased risk of cutting-out. In order to analyse the potential beneficial effects of the implant elasticity on fracture fixation, the biomechanical properties of a rigid and an elastic angle-fixed plating system were assessed in an experimental study. An unstable fracture of the surgical neck was created in 8 pairs of human humeri. Specimens were subjected to axial loading and torque. Stiffness, subsidence and load to failure were assessed. The implant with elastic properties was characterized by a lower torsional stiffness and a higher subsidence during axial loading and torque. This implant failed at lower loads than the rigid implant did. Elastic implant properties of angle-fixed plates have shown not to be advantageous for the management of fractures of the proximal humerus.     

Salvage of infected expander prostheses in breast reconstruction

Periprosthetic infection is a devastating complication following breast reconstruction with prostheses. Traditional surgical principles dictate removal of the prosthesis to control infection. Although successful salvage of prostheses in the presence of periprosthetic infections has been reported in the plastic and other surgical literature, salvage procedures remain seldom practiced. Reports in the plastic surgery literature have been limited to implant salvage following cosmetic breast augmentation and subcutaneous mastectomy with implants. Salvage of saline-filled expander prostheses used in breast reconstruction following mastectomy for cancer has not been previously reported. The authors review their experience with implant salvage in patients with periprosthetic infections following breast reconstruction for a 6-year period. Fourteen patients (13 with saline-filled expander prostheses and one with silicone prosthesis) underwent implant salvage. Salvage of the breast reconstruction was successful in nine patients. Staphylococcus aureus infection was associated with poorer salvage rate (p = 0.023). Previous radiotherapy to the chest wall did not affect the salvage outcome (p = 0.50). In selected patients, immediate salvage of a breast reconstruction in the presence of prosthesis-related infection remains an alternative to implant removal followed by delayed reconstruction.     

标尺模板在Branemark种植修复中的制作和应用

目的:制作并观察标尺模板在指导Branemark种植手术,提高手术安全性方面的作用。方法:选择15例患者52颗种植体,铸造制作标尺模板后戴入口腔拍摄曲面体层片。根据影象所显示的适宜种植区域与颏孔、上颌窦等颌骨重要解剖结构的位置,结合上部修复设计选择Branemark种植体数量与植入点,并借助标尺模板的定位网格予以记录。手术时将标尺模板戴入口腔,根据记录结果在颌骨表面显示种植体入点与颌骨重要解剖结构的位置,指导手术进行。术后戴入标尺模板拍摄对照片,判断种植体与预定位置的吻合性。结果:52颗种植体中,除1颗种植体因术中临时改变种植位置,其余51颗种植入位置均与术前计划一致。结论:在Branemark种植修复中制作并应用标尺模板,能方便直观地帮助术者将种植体植入预定位置,避免损伤颏孔等颌骨重要解剖结构,提高了手术的正确性与安全性。     

Use of a gonadotropin releasing hormone agonist implant as an alternative for surgical castration in male ferrets (Mustela putorius furo)

Surgical castration in ferrets has been implicated as an etiological factor in the development of hyperadrenocorticism in this species due to a castration-related increase in plasma gonadotropins. In search for a suitable alternative, the effect of treatment with the depot GnRH-agonist implant, deslorelin, on plasma testosterone concentrations and concurrent testes size, spermatogenesis, and the typical musky odor of intact male ferrets was investigated. Twenty-one male ferrets, equally divided into three groups, were either surgically castrated, received a slow release deslorelin implant or received a placebo implant. Plasma FSH and testosterone concentrations, testis size and spermatogenesis were all suppressed after the use of the deslorelin implant. The musky odor in the ferrets which had received a deslorelin implant was less compared to the ferrets which were either surgically castrated or had received a placebo implant. These results indicate that the deslorelin implant effectively prevents reproduction and the musky odor of intact male ferrets and is therefore considered a suitable alternative for surgical castration in these animals.     

Aesthetic augmentation of the malar-midface structures

Based on extensive experience with bone grafts for augmentation of the midface-malar region, an implant design has been developed using Proplast. After careful preoperative assessment, a very specific surgical method, described herein, allows precise implant positioning without the need for suture fixation. In many instances, the 6-mm implant can be inserted unchanged. One-hundred and six patients have been operated on using 176 implants over the past 6 years. There were four unilateral infections (2.3 percent of implants and 3.8 percent of patients). None had permanent motor or sensory nerve problems. Fifteen implants (8.5 percent) in 12 patients (11.3 percent) were either removed or repositioned. In those having augmentation for entirely aesthetic reasons, 3 of 60 patients (5.0 percent) required implant removal or repositioning. The incidence of needing to remove or reposition implants has decreased as the technique has evolved.     

A paradigm for the development and evaluation of novel implant topologies for bone fixation: Implant design and fabrication

The future development of bio-integrated devices will improve the functionality of robotic prosthetic limbs. A critical step in the advancement of bio-integrated prostheses will be establishing long-term, secure fixation to the remnant bone. To overcome limitations associated with contemporary bone-anchored prosthetic limbs, we established a paradigm for developing and fabricating novel orthopedic implants undergoing specified loading. A topology optimization scheme was utilized to generate optimal implant macrostructures that minimize deformations near the bone-implant interface. Variations in implant characteristics and interfacial connectivity were investigated to examine how these variables influence the layout of the optimized implant. For enhanced tissue integration, the optimally designed macroscopic geometry of a titanium (Ti)-alloy implant was further modified by introducing optimized microstructures. The complex geometries of selected implants were successfully fabricated using selective laser sintering (SLS) technology. Fabrication accuracy was assessed by comparing volumes and cross-sectional areas of fabricated implants to CAD data. The error of fabricated volume to CAD design volume was less than 8% and differences in cross sectional areas between SEM images of fabricated implants and corresponding cross sections from CAD design were on average less than 9%. We have demonstrated that this computational design method, combined with solid freeform fabrication techniques, provides a versatile way to develop novel orthopedic implants.     

A One-Piece Ocular Drainage Implant for Glaucoma Surgery: A Preliminary Report

A one-piece silicone filtration implant for glaucoma surgery was evaluated in 18 normotensive rabbits. During the follow-up period of 60 days the function of the implant and the effect of the implant on intraocular pressure (IOP) and local reaction in operated eyes were examined. Mean IOP in operated eyes during the whole follow-up period stayed in a level that was statistically significantly (p<0.001) lower than the preoperative starting value. Despite of a slight inflammatory reaction in the immediate postoperative period the implants were well tolerated. No marked foreign body reaction were noted around the implants in histological sections. In 3 eyes the implants had to be removed due to complications caused by surgical technique.     

Palatal implant surgery effectiveness in treatment of obstructive sleep apnea: A numerical method with 3D patient-specific geometries

Obstructive sleep apnea (OSA) affects a large percentage of the population and is increasingly recognized as a major global health problem. One surgical procedure for OSA is to implant polyethylene (PET) material into the soft palate, but its efficacy remains to be discussed. In this study, we provide input to this topic based on numerical simulations. Three 3 dimensional (3D) soft palate finite element models including mouth-close and mouth-open cases were created based on three patient-specific computed tomography (CT) images. A simplified material modeling approach with the Neo-Hookean material model was applied, and nonlinear geometry was accounted for. Young’s modulus for the implant material was obtained from uniaxial tests, and the PET implant pillars were inserted to the 3D soft palate model. With the finite element model, we designed different surgical schemes and investigated their efficacy with respect to avoiding the soft palate collapse. Several pillar schemes were tested, including different placement directions, different placement positions, different settings for the radius and the array parameters of the implant pillars, and different Young’s moduli for the pillars. Based on our simulation results, the longitudinal-direction implant surgery improved the stiffness of the soft palate to a small degree, and implanting in the transverse direction was evaluated to be a good choice for improving the existing surgical scheme. In addition, the Young’s modulus of the polyethylene material implants has an influence on the reinforcement efficacy of the soft palate.     

Non-anatomical placement adversely affects the functional performance of the meniscal implant: a finite element study

Biomechanics and Modeling in Mechanobiology - Non-anatomical placement may occur during the surgical implantation of the meniscal implant, and its influence on the resulting biomechanics of the...     

A simple method for in vivo measurement of implant rod three-dimensional geometry during scoliosis surgery

Scoliosis is defined as a spinal pathology characterized as a three-dimensional deformity of the spine combined with vertebral rotation. Treatment for severe scoliosis is achieved when the scoliotic spine is surgically corrected and fixed using implanted rods and screws. Several studies performed biomechanical modeling and corrective forces measurements of scoliosis correction. These studies were able to predict the clinical outcome and measured the corrective forces acting on screws, however, they were not able to measure the intraoperative three-dimensional geometry of the spinal rod. In effect, the results of biomechanical modeling might not be so realistic and the corrective forces during the surgical correction procedure were intra-operatively difficult to measure. Projective geometry has been shown to be successful in the reconstruction of a three-dimensional structure using a series of images obtained from different views. In this study, we propose a new method to measure the three-dimensional geometry of an implant rod using two cameras. The reconstruction method requires only a few parameters, the included angle θ between the two cameras, the actual length of the rod in mm, and the location of points for curve fitting. The implant rod utilized in spine surgery was used to evaluate the accuracy of the current method. The three-dimensional geometry of the rod was measured from the image obtained by a scanner and compared to the proposed method using two cameras. The mean error in the reconstruction measurements ranged from 0.32 to 0.45 mm. The method presented here demonstrated the possibility of intra-operatively measuring the three-dimensional geometry of spinal rod. The proposed method could be used in surgical procedures to better understand the biomechanics of scoliosis correction through real-time measurement of three-dimensional implant rod geometry in vivo.     

Mathematical modelling of implant in an operated hernia for estimation of the repair persistence

This paper presents mathematical modelling of an implanted surgical mesh used in the repair process of the abdominal hernia. The synthetic implant is simulated by a membrane structure. The author provides a material modelling of the implant based on the dense net model appropriate for technical fabrics. The accuracy of the proposed solution is evaluated by comparing the simulations of the dynamic behaviour of the system with the experiments carried out on physical models of implanted mesh. The model can be used to estimate the repair persistence for different mesh materials, fixing systems and different numbers of tacks to be provided during the surgery in order to resist the cough pressure and required action to avoid hernia recurrence. The persistence of the repaired hernia is assessed on the basis of the values of the forces in the tissue–implant joints because the usual form of the repair failure is due to as the joint disconnection or tissue failure.     

Camouflage and the Augmentation Mammaplasty

Augmentation mammaplasty has become a safe and accepted surgical procedure since the introduction of silicone prosthesis. Proper selection of the type and size of the implant and careful attention to making the line of incision as nearly invisible as possible are important for a natural-appearing breast. Placement of a silicone gel filled prosthetic implant through a periareolar incision achieves excellent contour and consistency in the augmented breast, with an essentially invisible scar.     

Flexible device for vertebral body replacement

A novel vertebral prosthesis is presented. The prosthesis was developed for surgical procedures requiring the resection of a complete vertebral body and the adjacent intervertebral discs, the design objective being to develop a flexible implant that would be robust enought to withstand the in vivo stress environment of the human spine. In theory, a flexible implant should preserve a more normal range of motion and apply less stress to surrounding tissue than a rigid implant. A prototype implant was constructed so as to combine a rigid stainless steel structure with flexible silicon rubber elements in order to form an implant with static and dynamic mechanical characteristics similar to those of the anterior spinal column. Implant flexibility characteristics were determined from ex vivo stress-strain behaviour during bending and compressive creep testing. Results from the bending tests indicated good agreement for the lateral and sagittal bending characteristics in comparison with in vitro bending tests of human lumbar motion segments. Comparison of the implant compressive creep responsé with similar in vitro tests on human lumbar intervertebral discs also demonstrated similarities in the time-dependent mechanical parameters.     

A novel rapid prototyping and finite element method-based development of the patient-specific temporomandibular joint implant

Objective: The objective of this study was to fabricate a successful implant for temporomandibular joint (TMJ) disorder patients who could not be treated through conventional surgeries.

Methods: A custom-made implant was fabricated using rapid prototyping (RP) for the TMJ surgery. The stability of the metallic implant was validated using a finite element analysis.

Results: The results of finite elements were stable and the design of the TMJ implant was suitable as per the patient's need. The customised implant was made using a fused deposition modelling method of RP and a vertical machining centre. The implant has provided normal jaw function for over 2 years since surgery.

Conclusions: The approach utilised will be helpful in providing successful treatment to the deformed mandible and the mandible joints. This method allows to customise and to accurately fabricatie the implant. Advantages of this approach are that the physical model of the implant was tested for stability before the implantation, the surgeon can plan and rehearse the surgery in advance, it is a less invasive and less time-consuming surgical procedure.     

Mechanical study of spinal interbody implants--characteristics and limits of standardized testing]

Spinal interbody fusion has proved to be a useful procedure for the surgical stabilization of spinal segments, for which fusion cases made of metal or reinforced polymers are increasingly being used. For the mechanical testing of spinal interbody implants, a test setup has been developed on the basis of an ASTM proposal. Initially, testing of lumbar fusion cages made of CFRP (carbon fibre reinforced polymer) was carried out. The implants (UNION Cages, Medtronic Sofamor Danek), which are characterised by their radiolucency on radiography, NMR and CT scans, have a cube-shaped body with three table-tracks on the under and upper surfaces. The cages were tested at different loads. Modifications of the proposed standardized method were carried out to enable implementation of implant-oriented testing. The tested cages were shown to have adequate axial compression, shear and torsional strengths with regard to the implant body. The maximum axial compression force tolerated by the table-tracks was less than the maximal potential loading of the lumbar spine, and, with account being taken of implant design, consequences with regard to surgical technique were drawn. As dictated by the geometry of the table-tracks, parallel grooves have to be made intra-operatively in the vertebral end plates. Axial compressive loads then act on the implant body, and the table-tracks are protected from damage. To avoid in vivo failure, the tested cages should be implanted only when this specific surgical technique is employed. Using supplementary anterior or posterior instrumentation, in vivo failure of the table-tracks under physiological spinal loading is not to be expected.     

Standardized Loads Acting in Knee Implants

The loads acting in knee joints must be known for improving joint replacement, surgical procedures, physiotherapy, biomechanical computer simulations, and to advise patients with osteoarthritis or fractures about what activities to avoid. Such data would also allow verification of test standards for knee implants. This work analyzes data from 8 subjects with instrumented knee implants, which allowed measuring the contact forces and moments acting in the joint. The implants were powered inductively and the loads transmitted at radio frequency. The time courses of forces and moments during walking, stair climbing, and 6 more activities were averaged for subjects with I) average body weight and average load levels and II) high body weight and high load levels. During all investigated activities except jogging, the high force levels reached 3,372–4,218N. During slow jogging, they were up to 5,165N. The peak torque around the implant stem during walking was 10.5 Nm, which was higher than during all other activities including jogging. The transverse forces and the moments varied greatly between the subjects, especially during non-cyclic activities. The high load levels measured were mostly above those defined in the wear test ISO 14243. The loads defined in the ISO test standard should be adapted to the levels reported here. The new data will allow realistic investigations and improvements of joint replacement, surgical procedures for tendon repair, treatment of fractures, and others. Computer models of the load conditions in the lower extremities will become more realistic if the new data is used as a gold standard. However, due to the extreme individual variations of some load components, even the reported average load profiles can most likely not explain every failure of an implant or a surgical procedure.     

Correlation of compartment pressure data from an intraoperative sensing device with postoperative fluoroscopic kinematic results in TKA patients

Fluoroscopy has recently been used to analyze postoperative kinematics in total knee arthroplasty (TKA). These analyses have reported varying results even in patients with similar implant design. In addition, patterns of wear in retrieved tibial polyethylene inserts of similar design have been found to vary substantially. These findings suggest that surgical technique, especially soft tissue balancing, may play a role in postoperative kinematics and implant failure. Accurate soft-tissue balancing is hypothesized to result in similar pressures within the medial and lateral compartments of the knee. However, a method of easily measuring these pressures at TKA has not been developed. In the present study, 32 patients were implanted with a mobile-bearing LCS TKA utilizing the balanced gap technique. An electronic pressure sensor, developed specifically to record pressure magnitude and distribution in the medial and lateral compartments, was incorporated into the implant trials. The knee was then passively taken through a range of motion while pressure data was recorded via computer. Postoperatively, 16 patients underwent active fluoroscopic kinematic analysis to assess for condylar liftoff and femorotibial translation. We found that abnormal compartment pressures and distributions as recorded by the intraoperative pressure sensor were correlated with inappropriate or paradoxical postoperative kinematics. In addition, subjects having similar pressures in both compartments throughout a range of motion did not experience condylar liftoff values greater than 1.0 mm. These data suggest that surgical technique influences the magnitude and distribution of forces at the articulation, postoperative kinematics, and likely, implant longevity.