Custom-made Prosthesis Research Articles

Endurance verification of custom-made hip prostheses

Custom-made stems are a particular class of hip prostheses manufactured in a single sample for a specific patient. Experimental fatigue testing according to ISO standards cannot be performed for pre-clinical validation of these devices. However, the implant manufacturers need to assess the endurance properties of custom-made stems. This study investigates a theoretical protocol to predict the maximum stress induced in the stem by the ISO experimental test set-up. Stress was predicted using beam theory and finite element analysis (FEA). Strain measurements were used to assess the accuracy of the theoretical calculation. Fatigue testing was performed to verify the theoretical prediction about the fatigue stem performance. The results showed that FEA is more accurate than beam theory. Beam theory calculation is able to predict the static stresses induced by the ISO 7206/4 loading set-up with a difference always lower than 20% with respect to a prediction of a simplified FEA. Hence beam theory can be used to estimate the maximum stress. FEA becomes useful for a stem stressed at a limit condition. In both cases precise data about the endurance properties of the material are required for corrected predictions. However, endurance verification should be performed by introducing a safety factor to account for the material and manufacturing variations.

Development of a software for the design of custom-made hip prostheses using an open-source rapid application development environment.

The present work describes a technology transfer project called HIPCOM devoted to the re-engineering of the process used by a medical devices manufacturer to design custom-made hip prostheses. Although it started with insufficient support from the end-user management, a very tight scheduling and a moderate budget, the project developed into what is considered by all partners a success story. In particular, the development of the design software, called HIPCOM Interactive Design Environment (HIDE) was completed in a time shorter than any optimistic expectation. The software was quite stable since its first beta version, and once introduced at the user site it fully replaced the original procedure in less than two months. One year after the early adoption, more than 80 custom-made prostheses had been designed with HIDE and the user had reported only two bugs, both cosmetics. The scope of the present work was to report the development experience and to investigate the reasons for these positive results, with particular reference to the development procedure and the software architecture. The choice of TCL/TK as development language and the adoption of well-defined software architecture were found to be the success key factors. Other important determinants were found to be the adoption of an incremental software engineering strategy, well suited for small to medium projects and the presence in the development staff of a technology transfer expert.

Fabrication of a radiation bolus prosthesis for the maxillectomy patient

Radiation therapy has been used in the treatment of numerous head and neck malignancies. Unfortunately, this treatment also causes complications by increasing the morbidity to the surrounding tissues. The fabrication of a tissue bolus prosthesis is recommended to compensate for the loss of tissue and to help distribute the radiation homogeneously to the tissues. This article describes the procedures necessary for making an impression and fabricating a tissue bolus prosthesis. This custom-made prosthesis is simple, efficient, and atraumatic for the patient. Use of a tissue bolus prosthesis allows the radiation oncologist to adequately irradiate the tissues. (J Prosthet Dent 2000;83:119-21.)

What are the basic possibilities for operative treatment of multiple loosening of the hip acetabulum?

Pronounced osteoporosis of and surrounding the acetabulum commonly leads to early loosening of endoprosthetic hip replacements following implantation. Large osseous defects in the subimplant bed are the result and the reason why multiple revisions of loosened acetabular cups have to be performed so often in rheumatic surgery. The defects extend from the cranial to the central; ventral and dorsal anchorage losses may occur in addition to this. The anchorage of a new implant must be adapted to the individual circumstances. The new implant must be selected in accordance with point of surgical access, the patient's general status and osseous regenerationability. In the optimum case, osseous buildup of lost anatomical structures is the preferred method. If this is not possible, special implants, mostly custom-made prostheses, have to be incorporated. However, the survival time of the implants is much shorter than in patients with degenerative diseases.

Multiple surgical possibilities for the correction of acetabulum failure in rheumatoid arthritis

Pronounced osteoporosis of and surrounding the acetabulum commonly leads to early loosening of endoprosthetic hip replacements following implantation. Large osseous defects in the subimplant bed are the result and the reason why multiple revisions of loosened acetabular cups have to be performed so often in rheumatic surgery. The defects extend from the cranial to the central; ventral and dorsal anchorage losses may occur in addition to this. The anchorage of a new implant must be adapted to the individual circumstances. The new implant must be selected in accordance with point of surgical access, the patient's general status and osseous regenerationability. In the optimum case, osseous buildup of lost anatomical structures is the preferred method. If this is not possible, special implants, mostly custom-made prostheses, have to be incorporated. However, the survival time of the implants is much shorter than in patients with degenerative diseases.

An FEA-based protocol for the pre-clinical validation of custom-made hip implants

Custom-made prostheses are successfully used to treat particular pathologies such as congenital hip dysplasia. The new EC rules on medical devices require a complete technical dossier for each produced custom-made device counter signed by the surgeon who ‘prescribes' the custom-made device. Thus, a specific preclinical validation protocol must be developed, considering the economical and temporal constraints imposed by the device type. As a first step, in the present study a protocol based on finite element analysis (FEA) was developed and validated, to verify each custom-made hip stem in terms of mechanical strength. The study was carried out on 12 custom-made cementless hip stem designs already produced and implanted, for which the 3D solid model was available. Two of the selected designs were used for the method validation, comparing strain gauges measurements with the stresses predicted by the finite element (FE) model. Once the proposed methodology was verified, all the remaining stem designs were analysed. The developed protocol made possible a complete analysis in less than 4 h; its accuracy (7–8% on the strain gauge measurements) was considered acceptable for the specific application.

Resection arthrodesis of the knee in the treatment of tumours--a long-term follow-up.

Limb salvage operations using large custom-made prostheses have become the treatment of choice for juxta-articular tumours at the knee. Resection-arthrodesis has been used since the 1920s and offers a satisfactory long term solution for young active patients. The good functional results after this procedure in 9 patients is presented here. This method should still be considered in selected cases.

Fabrication of custom-made facial prosthesis by mirror image stereolithography modelling, titanium casting and laser welding

Fabrication of custom-made facial prosthesis by mirror image stereolithography modelling, titanium casting and laser welding

ASEPTIC LOOSENING IN CEMENTED CUSTOM-MADE PROSTHETIC REPLACEMENTS FOR BONE TUMOURS OF THE LOWER LIMB

We have made a retrospective study of 1001 custom-made prostheses used as replacements after surgery for bone tumours. There were 493 distal femoral, 263 proximal femoral and 245 proximal tibial prostheses. Aseptic loosening was shown to be the principal mode of failure of the implants, and 71 patients had revision for aseptic loosening of a cemented intramedullary stem. The probability of a patient surviving aseptic loosening for 120 months was 93.8% for a proximal femoral replacement, 67.4% for a distal femoral prosthesis and 58% for a proximal tibial implant. In patients with distal femoral replacements the age of the patient at the time of operation and the percentage of bone resected were related to the risk of aseptic loosening. Young patients with distal femoral prostheses in whom a high percentage of the femur had been replaced had the poorest prognosis for survival without aseptic loosening. The percentage of bone removed had a significant effect in the proximal tibial replacement group, but the age of the patient did not. By contrast, neither the age nor the percentage of bone removed was a factor after proximal femoral replacement. The significance of these findings is discussed in relation to mechanical factors.

Management of bone loss in revision total hip arthroplasty using custom cementless femoral components

Forty-seven consecutive revision total hip arthroplasties were performed using porous ingrowth custom-made prostheses designed from plain radiographs and computed tomography scans. At an average follow-up period of 30 months (range, 2–4 years), one rerevision has been required for loosening. The average Harris pain score was 39 and the average total score was 84 at the last follow-up evaluation. Complications included nine cases (19%) with intraoperatively detected fractures of the proximal femur treated with cerclage wires and seven cases (15%) with subsidence greater than 3 mm. There were no postoperative infections and only two dislocations. At the time of surgery local particulate bone graft was used in all cases. Thirty-four percent required structural graft to restore bone stock; no case required grafting for prosthesis stability. Management of bone loss in total hip arthroplasty using a custom cementless prosthesis appears to provide an attractive alternative to massive bone grafting.

Replantation of an autoclaved, autogenous humerus in a patient who had chondrosarcoma. Report of a case with ten-year follow-up.

There is little doubt that low-grade intramedullary chondrosarcoma can be treated succesfully with segmental resection. Questions then arise regarding the best type of reconstruction after resection - whether the use of allografts, custom-made prostheses, or replantation of an autoclaved, autogenous segment is best. Recurrence of the chondrosarcoma after replantation of an autoclaved segment has not been reported, to our knowledge. The case that it reported here is unique for two reasons

The morphology of the proximal femur. A three-dimensional radiographic analysis

Biological fixation of cementless femoral implants requires primary stability by optimal fit in the proximal femur. The anatomy of the bone must then be known precisely. We analysed in vitro the accuracy of bone measurements of 32 femurs and compared the dimensions obtained from radiographs and CT scans with the true anatomical dimensions. Standard radiographs gave only a rough approximation of femoral geometry (mean difference: 2.4 +/- 1.4 mm) insufficiently accurate to allow selection of the best fitting prosthesis from a range of sizes and altogether inadequate to design a custom-made prosthesis. CT scans give greater accuracy (mean difference: 0.8 +/- 0.7 mm) in our experimental conditions, but in clinical practice additional sources of error exist.

Orthopaedic robotics. Third Annual International Symposium on Custom-made Prostheses. October 1990--Nice, France

The Journal of Bone and Joint Surgery. British volumeVol. 73-B, No. 2 ArticlesFree AccessOrthopaedic robotics. Third Annual International Symposium on Custom-made Prostheses. October 1990--Nice, FranceJ GoodfellowJ GoodfellowSearch for more papers by this authorPublished Online:1 Mar 1991https://doi.org/10.1302/0301-620X.73B2.2005178AboutSectionsPDF/EPUB ToolsAdd to FavouritesDownload CitationsTrack CitationsPermissions ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited ByRobotic Interactive laparoscopic cholecystectomyThe Lancet, Vol. 343, No. 8897 Vol. 73-B, No. 2 Metrics Downloaded 87 times History Published online 1 March 1991 Published in print 1 March 1991 InformationCopyright © 1991, The British Editorial Society of Bone and Joint Surgery: All rights reservedPDF download

A Custom-Made Prosthesis for the Treatment of Supracondylar Femoral Fractures After Total Knee Arthroplasty

Four supracondylar femoral fractures following total knee arthroplasty, two because of intraoperative notching of the anterior femoral cortex and two because of osteoporosis, were revised using a custom-made prosthesis with femoral condyle section. At 1-6 year follow-up (median 3 years) after the revision, all patients had an excellent clinical result, although 2 had a prolonged rehabilitation period because of severe osteoporosis. At roentgenographic examination, no signs of loosening of the prostheses at the cement-bone interface were present.

Custom-made nipple-areola prostheses in breast reconstruction

The nipple-areola prosthesis is a useful temporary or permanent adjunct to breast reconstruction. The commercially available prostheses, however, are unable to reflect the remarkable normal variation in this anatomical feature. We describe the production and use of custom-made prostheses using the remaining nipple-areola complex as a template. Their success in 72 patients has led us to adopt such prostheses as routine in breast reconstruction.

Technical considerations of total knee arthroplasty after proximal tibial osteotomy.

Forty-five total knee replacements in forty-one patients who had continued to have progressive osteoarthritis after a proximal tibial osteotomy were evaluated prospectively. There were 51 per cent excellent, 29 per cent good, 4 per cent fair, and 16 per cent poor results after a minimum follow-up of two years. The resection of tibial bone that was produced by the osteotomy could not be related causally to the fair or poor clinical results that were found after arthroplasty. Radiographic study, however, showed that 80 per cent of the knees had patella infera before the arthroplasty, which may contribute to altered biomechanics of the patellofemoral joint of the arthroplasty. The procedure for total knee replacement is made more difficult by the previous osteotomy, and a custom-made prosthesis may be required. The clinical results that were obtained in this series are similar to those for the revision total knee arthroplasties that have been done at this institution, but they were not as satisfactory as those that were obtained after primary total knee replacement. Our results should be considered when a surgeon compares the advantages and disadvantages of proximal tibial osteotomy with those of total knee arthroplasty for an older patient who has unicompartmental osteoarthritis of the knee.

Distal femoral replacement by custom-made prostheses. Clinical follow-up and survivorship analysis

We report the long-term clinical follow-up and survivorship analysis of 40 distal femoral replacements performed between 1964 and 1980 for traumatic, locally aggressive and malignant conditions. Custom-made prostheses with fully-constrained knee joints were used to replace a mean of 42% of the length of the femur. Survivorship analysis showed a cumulative success rate of 80% at eight years, with no subsequent deterioration at 18 years. Clinical assessment revealed 78% excellent or good results. Failure was due to infection in three cases, and in two to fracture of a now-outmoded femoral stem.

Two-stage reimplantation for the salvage of infected total knee arthroplasty.

The results of eleven two-stage reimplantations to salvage eleven infected total knee arthroplasties in ten women (seven with osteoarthritis and three with rheumatoid arthritis) were evaluated after an average follow-up of thirty-four months. The staged procedures included removal of all of the components of the prosthesis and all cement, then six weeks of parenteral antibiotic therapy (monitored by maintaining serum bactericidal levels at a peak dilution of 1:8), and finally reimplantation with a total condylar-type prosthesis. All antibiotics were discontinued after reimplantation. At follow-up, no patient had had a recurrence of the original infection, but one had a hematogenous infection with a different organism secondary to an infected bunion. The results after reimplantation were rated excellent in five knees, good in four, and fair in two. Weakness of the extensor mechanism with an extension lag was the most frequent complication. We do not believe that antibiotic therapy alone is adequate for the management of an infection around a prosthesis. The method described appears to be effective but it is costly and time-consuming. The surgical procedures and medical management are technically difficult, often special equipment and a custom-made prosthesis are required, and there are no shortcuts.