[Perspectives of artistic prosthesis design and prosthesis construction].
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Artificial Limbs↗
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A new patella prosthesis. Design and application.
The new patella prosthesis design is based on an anatomical study of 80 arthritic patellas and on the normal patellofemoral contact area under loading in cadaver knees. The metal dome-shaped prosthesis is attached by a central pin. The patellar prosthesis is constructed either of metal or plastic for use in combination with the Hospital for Special Surgery design of total knee prosthesis. Methylmethacrylate is used to supplement the fixation after resection of the abnormal patellar articular surface. The fixation tests gave excellent laboratory results for contact area and stability. The prosthesis has been used in 19 cases with encouraging early results.
Adult↗
Biomechanical evaluation of metacarpophalangeal joint prosthesis designs.
A laboratory biomechanical analysis of metacarpophalangeal joint prosthesis designs was done with fresh cadaver finger rays. The center of rotation, range of motion, tendon excursion, and fingertip force were determined on the specimens before and after implanting Swanson, Niebauer, Steffee II, St. Georg-Buchholz, Schultz, and modified Strickland prostheses. Their biomechanical behavior varied considerably and none duplicated the normal metacarpophalangeal (MP) joint. Each has design characteristics that may be clinically advantageous as well as disadvantageous. Irrespective of the design, the studies done cannot be divorced from the following factors: (1) implant material properties--silicone rubber implants buckled with tendon loading; this deformity created a significant flexor mechanical advantage and an extensor mechanical disadvantage; (2) implant fixation--freely movable implant stems dampened part of the applied load; braided suture provided inadequate immediate fixation; (3) implantation technique--the articulated prostheses can be technically unforgiving; errors in technique resulted in alteration of their biomechanical behavior.
Biomechanical Phenomena↗
A new approach towards hip-prosthesis design.
A new femoral prosthesis with a stemless design, different from conventional types, has been conceived in an effort to preserve the physiological stress distribution in magnitude and direction within the living bone as far as possible. The most important feature is that the hip joint forces are transmitted directly to the cortical bone of the resected femoral neck by means of a thrust plate, which maintains the physiological stress an the proximal end of the femur. The prosthesis, the instruments required for its implantation and the surgical technique are described in detail. Up to now, 3 patients have received this new prosthesis.
Hip Joint↗
Prosthesis design for osseointegrated implants in the edentulous maxilla.
The position of osseointegrated implants in the edentulous maxilla is dictated by available bone and can vary widely among patients. Anatomy limits the amount of bone available for placement of osseointegrated implants. With increasing resorption, the number, length, and position of implants are further compromised. Bone grafts are frequently needed to place implants of adequate length. The variability of implant placement indicates the need for multiple prosthesis designs in the maxilla. Prosthesis design considerations are suggested for patients with minimal, moderate, and severe resorption of the edentulous maxilla.
Alveolar Bone Loss↗
The influence of prosthesis designs and loading conditions on the stress distribution of tooth-implant supported prostheses.
The aim of this study was to observe the influence of prosthesis design and loading condition on the stress distributions of tooth-implant supported prostheses. Six 2D finite element models, two reference models, and four experimental models were computed to simulate different prosthesis designs. Six different loading conditions were applied to investigate the stress distributions of tooth and implant, respectively. The stresses of reference models were considered as 100%; the stresses of experimental models at the same locations were compared with those of reference models. The stresses around implants were higher than those around teeth. When vertical loading was applied only on the implant, the stresses to both the implant and teeth were at their lowest. The highest stress to the tooth was in the model TTPF and the lowest in the model TPFF. The highest stress to the implant was in the model TPPF and the lowest in the model TPFF. These data indicated that the loading on the tooth-implant supported prosthesis was mainly supported by the implant. Minimizing the loading on the tooth decreased the stress to both the tooth and the implant. Adding fixtures as abutment was more effective in decreasing the stress than adding tooth as abutment in tooth-implant supported prosthesis.
Alveolar Process↗
Survival of various implant-supported prosthesis designs following 36 months of clinical function.
BACKGROUND: The use of endosseous dental implants to replace natural teeth lost to trauma, dental caries, or periodontal disease has become a predictable form of prosthetic treatment since gaining popularity in the early 1980s. While numerous clinical studies have focused on the survival of implants, few address the survival of different prosthesis designs. METHODS: Beginning in 1991, 882 prostheses supported by more than 2,900 implants (687 patients) were placed by the Department of Veterans Affairs Dental Implant Clinical Research Group (DICRG). These prostheses were divided into five research strata based on arch location. The recommended design for each stratum was: bar-supported overdenture (maxillary completely edentulous); screw-retained hybrid denture (mandibular completely edentulous); screw-retained fixed partial denture (mandibular and maxillary posterior partially edentulous); and cemented single crown (maxillary anterior single tooth). Alternative overdenture designs were utilized in the edentulous arches when the recommended prosthesis could not be fabricated. Prosthesis success rates for the research strata were calculated for an observation time of up to 36 months following prosthesis placement. RESULTS: Success rates for the maxillary edentulous stratum ranged from 94.6% for the bar-retained overdenture supported by five to six fixtures to 81.8% for the cap-retained overdenture. The mandibular edentulous strata produced success rates of 98.1% for the fixed hybrid prosthesis to 91.7% for the cap-retained prosthesis. Success rates for maxillary and mandibular posterior fixed partial dentures were 94.3% and 92.6%, respectively, while the maxillary anterior single-tooth prosthesis yielded a success rate of 98.1% for the 36-month observation period. CONCLUSIONS: The recommended prosthesis designs investigated in this study proved to be reliable, with encouraging success rates for an observation period of 36 months following placement.
Alloys↗
The effect of prosthesis design on vibration of the reconstructed ossicular chain: a comparative finite element analysis of four prostheses.
HYPOTHESIS: It was hypothesized that the differences in the bioacoustic performance of ossicular replacement prosthesis designs, and insertion positions, could be quantified using finite element analysis. BACKGROUND: Many designs of prosthesis are available for middle ear surgery. The materials used, and the shape of the implants, differ widely. Advances in computer simulation technologies offer the possibility of replicating the in vivo behavior of the different prostheses. If this can be achieved, insight into the design attributes required for improved biofunctionality may be gained. METHODS: Micro-computed tomography and nuclear magnetic resonance imaging were used to obtain geometric information that was translated into a finite element model of the outer and middle ear. The forced frequency response across the hearing range of the normal middle ear was compared with the middle ear reconstructed with partial and total ossicular replacement prostheses. RESULTS: The amplitude of vibration of the footplate was more similar to that of the normal ear when a Kurz total ossicular replacement prosthesis was implanted than when a Xomed total ossicular replacement prosthesis was implanted. This may be attributed to the latter's titanium link. Partial ossicular replacement prostheses were stiffest and had lower umbo vibrations and higher stapedial footplate vibrations. In all cases but one, the vibration of the prostheses had resonances that caused the vibration of the stapes footplate to be noticeably different from normal. CONCLUSION: The authors confirmed the hypothesis that finite element modeling can be used to predict the differences in the response of ossicular replacement prostheses. This study shows that computer simulation can potentially be used to test or optimize the vibroacoustic characteristics of middle ear implants.
Acoustic Impedance Tests↗
The anatomic features of the radial head and their implication for prosthesis design.
OBJECTIVE: To establish the anatomical features of the radial head of an average normal human being and to verify the hypothesis that no significant difference exists between the geometry of the left and right normal radial heads. DESIGN: 17 proximal ends of the radius from the left and right forearms of fresh male (average age 50 and range 40-70) cadavers were measured. BACKGROUND: A reconstruction of anatomical features of the normal bone is important for prosthesis design. METHODS: A morphologic study of the radial head was performed using a co-ordinate measuring machine integrated with a computer aided design system. For comparative purposes, a statistical analysis including linear regression and correlation was performed. RESULTS: The maximum diameter (mean 23.36 mm (SD, 1.14 mm)) and height (mean 10.14 mm (SD, 1.38 mm)) of the radial head as well as the depth (mean 1.92 mm (SD, 0.32 mm)) and maximum radius (mean 20.27 mm (SD, 4.61 mm)) of the concave articulate surface are the most important anatomical features, which should be implicated in prosthesis design. The inclinations mean 2.50 degrees (SD, 0.41 degrees ) and mean 9.50 degrees (SD, 0.52 degrees ) and shift (mean 1.71 mm (SD, 0.35 mm)) of the radial head relative to its neck should also be taken into account in prosthetic design. CONCLUSIONS: The results of the study showed that "left is equal to right" (no significant differences between sides were obtained, for probability value P>0.05). RELEVANCE: This paper describes a morphological study of the proximal radius. The results can be used to reconstruct the geometry of the injured radial head based on the obtained geometric features of the contra-lateral side. These results can be also used to design radial head prosthesis.
Adult↗
Prosthesis design and treatment planning for the partially edentulous implant patient.
The evolution of prosthesis design principles over the last ten years has contributed to an improved clinical prognosis for the partially edentulous patient. Restorations can now be created with significant cosmetic improvements and less stressful long-term maintenance, due to a better understanding of restorative procedures which include natural tooth connection, biomechanical loading, tooth form modifications, and esthetic componentry. This presentation will review these concepts as the basis for recommending currently acceptable design principles and treatment plans for the fixed reconstruction of the partially edentulous implant patient.
Dental Abutments↗
Loosening performance of cemented glenoid prosthesis design pairs.
OBJECTIVE: The purpose of this pilot study (n=3) was to compare the loosening performance of glenoid prosthesis design pairs where only one design variable differed. DESIGN: Glenoids were subjected to dynamic edge loading in a biaxial test setup. BACKGROUND: Glenoid component loosening is the primary concern in total shoulder arthroplasty. METHODS: After the humeral head was cycled 100,000 times to the superior and inferior edges of the glenoid, the tensile edge displacements were measured under superior and inferior off-center loading. RESULTS AND CONCLUSIONS: Based on this study, a rough-backed design had dramatically better loosening performance than a smooth-backed; curved-backed was superior to flat-backed; a less-constrained articular surface was better than a more-constrained articular surface; pegs outperformed a keel; threaded pegs were marginally preferable to cylindrical pegs; and an all-polyethylene design rocked slightly less than a metal-mesh-backed design. RELEVANCE: A comparison of the laboratory loosening behavior of glenoid prostheses may lead to improved designs, subsequently leading to a reduction in the incidence of clinical loosening.
Biomechanical Phenomena↗
A study of Chinese knee joint geometry for prosthesis design.
This study for the first time provides the geometric parameters of the knee joint of Chinese, which is indispensible to the design of knee prosthesis used for compatriotic patients. Thirty-five items, including linear, radial and angular measurements, were taken from 105 cadaveric knees and knee X-ray films of 1,100 subjects. The method and calculation for proper correction of the X-ray image magnification and joint cartilage space was established. Correlation was found to exist between the X-ray correction coefficients and the body weight, which formed the basis for individualized correction of X-ray measurements. Statistical analysis revealed that most of the linear and radial measurements were highly related while the angular measurements were independent of others. Principal component analysis showed that the width of femoral condyle might be taken as the leading index in determining the dimension of the knee, and regression functions were established to supply the serial parameters for prosthetic design. Multivariate discriminate functions could aid the selection of knee prosthesis.
Anthropometry↗
Early results of a reverse design prosthesis in the treatment of arthritis of the shoulder in elderly patients with a large rotator cuff tear.
Results of shoulder arthroplasty in patients with a deficient rotator cuff often are suboptimal with significant limitations in postoperative active mobility. Short-term results using a reverse design prosthesis in the treatment of the cuff-deficient arthritic shoulder are encouraging. This prosthesis compares favorably, particularly with regard to postoperative active anterior elevation, to other treatment options in this challenging patient population.
Aged↗
Obturator prosthesis design for acquired maxillary defects.
Fabrication of obturator prostheses does not require a special ability to fabricate a prosthesis extension into a defect or an arbitrary extension of a prosthesis into a defect. Fabrication of an obturator prosthesis depends on the application of basic prosthodontic principles that are used in the treatment of patients without maxillary defects. Some principles must be modified because of the defect and the character and position of the remaining structures. The defect, in conjunction with the remaining structures, must be used to provide support, retention, and stability of an obturator prosthesis. If basic prosthodontic principles are applied the size and extension of the obturator will be determined, and the extensive variation so commonly seen in obturators will be minimized. Acceptable prosthodontic care for the patient with the acquired maxillary defect should include cautious prosthesis design combined with routine maintenance care to provide comfort, function, cosmetics, and minimal change to the compromised remaining structures.
Alveolar Process↗
[A study on knee joint geometry in Chinese: significance to prosthesis design].
This study for the first time provided the geometric parameters of knee joints in Chinese, which are indispensable for the design of domestic knee prosthesis. Thirty five items, including linear, radial and angular measurements, were taken from 105 cadaver knees and knee X-ray films of 100 subjects. The method and calculation for proper correction of the X-ray image magnification and joint cartilage space was established. Correlation between the X-ray correction coefficients and the body weight was found to exist, and it formed the basis for individualized correction of X ray measurements. Statistical analysis revealed that most of the linear and radial measurements were highly related while the angular measurements were independent of others. Principal component analysis showed that the width of femoral condyle might be taken as the leading index in determining the dimension of the knee, and regression functions were established. Multivariate discriminate functions could aid the selection of knee prosthesis.
Adolescent↗
Geometry and mechanics of the human ankle complex and ankle prosthesis design.
The main objective of the study was to develop a model of the intact human ankle complex. It was also aimed at designing total ankle replacement which would better reproduce the physiological function of the joint. Passive flexion was analysed in seven lower-leg preparations with a stereophotogrammetric system. The articular surfaces and fibres within the calcaneofibular and tibiocalcaneal ligaments prescribed the changing positions of the axis of rotation. Joint motion included rolling as well as sliding. A computer-based model elucidated the observed kinematics at the intact joint. The experimental evidence and the geometrical model gave the basis for the design of models of replaced ankle in the sagittal plane. A three-component, convex-tibia prosthesis was eventually selected with articular surface shapes compatible with the geometry of the ligaments. It was demonstrated that in intact ankle joint, the geometry of the articular surfaces is strictly related to that of the ligaments and that current prosthesis designs do not restore physiological pattern of ligament tensioning. Careful reconstruction of the ligaments is recommended in any ankle surgery for maintenance of the normal kinematics and mechanics. A proposed novel design based on ligament/shape compatibility may improve total ankle replacement results.
Ankle Joint↗
The derivation of elbow joint forces, and their relation to prosthesis design.
A literature review showed a lack of accurate data for upper limb joint forces. After discussing methods to determine muscle forces, the physiological cross-sections of muscles were used to estimate their strengths. Elbow joint forces were predicted for isometric actions which gave severe loading conditions. The predicted forces were discussed in relation to prosthesis design, and the use of a radial head replacement was recommended.
Biomechanical Phenomena↗
A quantitative approach to modeling mammalian myelinated nerve fibers for electrical prosthesis design.
This paper presents an upgraded cable model of mammalian myelinated nerve fibers in an extracellularly applied field. The kinetics of the nodes is based upon voltage clamp data in rat motor fibers at 37 degrees C, while the resting membrane potential is computed with the Goldman equation. The resulting spike shape, conduction velocity, strength/duration behavior, and absolute and relative refractory period are in good quantitative agreement with published experimental data in mammals at normal body temperature and at 20 degrees C. Results at intermediate temperatures however, suggest that the widely used concept of a constant Q10 for the rate constants is invalid. In addition, the model generates realistic abortive spikes towards the end of the absolute refractory period and it can describe the consequences of repetitive firing. The results stress the advantages of a multiple nonlinear node model even if only time aspects of nerve behavior are under study. It turned out, that the model presented here describes in vivo neural properties relevant for electrical prosthesis design better than previous models in literature.
Animals↗