Retrospective evaluation of implants--is there a need?
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Humans↗
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Experience with Memokath 051 ureteral stent.
OBJECTIVE: The Memokath 051 is a thermo-expandable titanium-nickel spiral developed for long-term ureteral stenting. The aim of this study was to investigate the drainage and safety aspects of this stent. MATERIAL AND METHODS: A total of 3-4 consecutive patients were included: 22 had benign strictures, five had post-irradiation strictures and seven had malignant strictures. Follow-up visits took place after 1 month and thereafter every 3 months for at least 1 year. RESULTS: Thirty-three patients had a total of 37 stents inserted uni- or bilaterally. Pre-insertion dilatation was impossible in one patient and difficult in two, all of whom had post-irradiation strictures. Insertion was complicated in seven patients and uneventful in the other 26. Fifteen stents were in place and functioning with no discomfort or complications at death or the end of follow-up (median 14 months; range 3-30 months), while 22 were non-functioning after 1 day to 16 months (median 5 months). Of these 22 stents, 10 had migrated and 12 were malfunctioning. Among the latter, stricture length was underestimated in four patients, and the stents were replaced successfully shortly after insertion. Four stents were occluded by stones after 1-10 months. No tissue ingrowth was seen. Stent removal was easy, with the exception of one patient with stent calcification. CONCLUSIONS: The Memokath 051 is an alternative for selected patients with non-curable ureteral obstruction but is not suitable for use in patients with functional stenosis or stone formation. Insertion and removal are easy in most patients, but can be difficult or impossible, especially in patients with post-irradiation strictures and retroperitoneal fibrosis. Migration and obstruction can occur and careful follow-up is necessary.
Adult↗
Lower limb amputation. Part 3: Prosthetics--a 10 year literature review.
This paper is intended as a follow-up to the ISPO Consensus Conference on Amputation Surgery. It reviews all the literature on lower limb prosthetics published after 1990. The review was considered under six categories: feet, knees, hips, thermoplastics, liners/suspension and computers.
Amputation, Surgical↗
Sand-casting technique for trans-tibial prostheses.
A sand-casting technique for trans-tibial sockets was applied to 28 amputees, and the prosthetic fit observed through transparent check sockets. The results were better than historical reports of fittings with plaster of Paris casting by qualified prosthetists. The fit was consistently and evenly larger than the stump, but total contact could be achieved by applying three (two to five) stump socks. This would normally be considered on the high side of a good fit.
Adult↗
Better practical evaluation for lower limb amputees.
PURPOSE: To avoid wastage of prostheses and unfair selection methods for prosthetic prescription, we aimed to develop a practical assessment tool for amputees with doubtful potential, using refurbished second hand modular prostheses. METHOD: Thirty-seven primary amputees (33 transfemoral, 4 transtibial; 22 males, 15 females; median age 71 years, range 19-91) were considered to have doubtful potential for prosthetic use, due to single or multiple impairments. Amputees were assessed using custom-made socket and refurbished second-hand modular prostheses. Liability issues were fully covered. RESULTS: Two patients died before completing the assessment. Median duration of assessment was 4 weeks (range 1-31 weeks). Among the 35 amputees who completed the trial, 14 (38%) proceeded to final prosthesis successfully and 21 (58%) decided to abandon the prostheses. The main reasons for prostheses rejection identified by the team were: hip flexion deformity (4); frailty (4); bilateral amputations (4); COAD (6), stroke (4), stump pain (3) and contralateral leg problems (2) CONCLUSION: High prosthetic rejection rate was expected and confirmed in this group (58%), but considerable number did proceed to definitive prosthesis. The method is practical and fair for amputees of doubtful potential, with considerable cost saving.
Adult↗
The Otto Aufranc Award. Image guided navigation system to measure intraoperatively acetabular implant alignment.
There has been little clinical research to examine the effects of patient positioning and pelvic motion on the alignment of the acetabular implant during total hip replacement surgery. Until now, no tools were capable of accurately measuring these variables during the actual procedure. As part of a broader program in medical robotics and computer assisted surgery, a clinical system has been developed that includes several enabling technologies. The hip navigation system (HipNav) continuously and precisely measures pelvic location and tracks relative implant alignment intraoperatively. HipNav technology is used to gauge current clinical practice and provide intraoperative feedback to surgeons with the goal of improving the precision and accuracy of acetabular alignment during total hip replacement. This system provides surgeons with a new class of image guided measurement tools and assist devices. These tools successfully were introduced into the clinical practice of surgery with results showing the following: (1) There exist unpredictable and large variations in the initial position of patients' pelves on the operating room table and significant pelvic movement during surgery and during intraoperative range of motion testing; (2) current mechanical acetabular alignment guides do not account for these variations, and result in variable and in the majority of cases unacceptable acetabular alignment; and (3) press fitting oversized acetabular components influences the final cup orientation.
Anthropometry↗
Malrotation causing patellofemoral complications after total knee arthroplasty.
Thirty patients with isolated patellofemoral complications after total knee arthroplasty were compared with 20 patients with well functioning total knee replacements without patellofemoral complications. The epicondylar axis and tibial tubercle were used as references on computed tomography scans to measure quantitatively rotational alignment of the femoral and tibial components. The group with patellofemoral complications had excessive combined (tibial plus femoral) internal component rotation. This excessive combined internal rotation was directly proportional to the severity of the patellofemoral complication. Small amounts of combined internal rotation (1 degree-4 degrees) correlated with lateral tracking and patellar tilting. Moderate combined internal rotation (3 degrees-8 degrees) correlated with patellar subluxation. Large amounts of combined internal rotational (7 degrees-17 degrees) correlated with early patellar dislocation or late patellar prosthesis failure. The control group was in combined external rotation (10 degrees-0 degree). The direct correlation of combined (femoral and tibial) internal component rotation to the severity of the patellofemoral complication suggests that internal component rotation may be the predominant cause of patellofemoral complications in patients with normal axial alignment. The epicondylar axis and tibial tubercle are reproducible landmarks which are visible on computed tomography scans and can be used intraoperatively. Using this computed tomography study can determine wether rotational malalignment is present and thus, whether revision of one or both components may be indicated.
Arthroplasty, Replacement, Knee↗
Use of extendable total femoral replacements in children with malignant bone tumors.
Although rarely required, extendable reconstruction devices for replacing the entire femur offer children with malignant bone tumors the opportunity of a nearly normal development by overcoming an expected leg length discrepancy. Femoral integrity can be restored, allowing most patients to walk without the use of aids. There are no data available to provide evidence regarding long term results and morbidity in such patients. Six patients (range 2-12 years of age), three with osteogenic osteosarcoma and three with Ewing's sarcoma, were treated between 1988 and 1996 with custom made Stanmore extendable prosthetic total femoral replacements. One patient died 12 months after surgery because of complications relating to pulmonary metastasis. The remaining five patients were observed between 2.7 and 8.9 years (average, 5 years). No tumor recurrence has been recorded and no amputation has been performed. All surviving patients underwent an average of 9.4 operative procedures (range, 4-16 procedures) including 6.4 extension procedures (range, 3-10 procedures), and one prosthetic revision (range, 0-3 procedures). Five revisions in two patients were necessary because of infection, loosening of the prosthesis, mismatch between femoral head and acetabulum, or full extension of the extending mechanism. The functional results were measured in accordance with the Musculoskeletal Tumor Society rating score, with an average result of 77.3%. Total femoral replacement in a growing individual achieves good functional results yet has various risks for an uncertain outcome. Careful selection of the patient and realistic appraisal of the long term prospects are essential for successful treatment.
Bone Neoplasms↗
Clinical and finite element analysis of a modular femoral prosthesis consisting of a head and stem component in the treatment of pertrochanteric fractures.
OBJECTIVE: To determine the biomechanical characteristics and potential clinical efficacy of a cementless modular femoral prosthesis consisting of a variable head (50 to 80 millimeters) and stem (length 120 to 280 millimeters, diameter 10 to 20 millimeters) component in patients with pertrochanteric femoral fracture. DESIGN: Finite element analysis (FEA) of different lengths and diameters of prosthesis components and first clinical prospective study in pertrochanteric femoral fracture. METHOD: Using a 3D-CAD program, a model of femoral cortical bone with a pertrochanteric fracture was created and combined with a model of the prosthesis. This model was transferred into an FEA program. After applying a torsion-bending load of 2,000 N (25 degrees, 45 degrees) on the prosthesis, stress distribution in the cortical bone was determined for different lengths (160 to 240 millimeters) and diameters (10 and 12 millimeters) of stem. PATIENTS: Twenty-eight patients with pertrochanteric fractures (very unstable or osteoarthritis) were treated with a modular hip arthroplasty. Complications, fracture healing, and results at first follow-up (average 13 months) were determined. RESULTS: FEA analysis indicated that reduction in stress was less when a prosthesis with a short stem was used. Shear stress in the interface bone/prosthesis was not affected by stem length. Prostheses with thin stems produced higher sheer stresses than those with thick stems. Results of FEA were used as the basis for clinical application of the device. None of the patients died, and all patients were able to walk, although some needed a cane or walker after surgery. There was no increase in thigh pain compared with reported pretrauma levels. Radiographs showed subsidence of up to 5 millimeters in 20 percent of patients. However, all but one prosthesis was stable at follow-up. Fracture healing was achieved in all patients. CONCLUSIONS: If proximal fixation of a femoral uncemented stem cannot be achieved, stem diameter should provide maximum cortical contact to reduce sheer stress. Longer stems do not necessarily provide additional stability. By using this prosthesis and selection method, a good outcome at first follow-up was observed.
Activities of Daily Living↗
In vivo analysis of bacterial biofilm formation on facial plastic bioimplants.
OBJECTIVES: This study examines the formation of biofilm on biomaterials commonly used in facial plastics and reconstruction including titanium, silicone, ion-bombarded silicone (Ultrasil), e-PTFE (Gore-Tex), e-PTFE with silver/chlorhexidine (Gore-Tex Plus), and PHDPE (Medpor). METHODS: These biomaterials were implanted subcutaneously in the dorsum of 11 guinea pigs after contamination with Staphylococcus aureus and examined with scanning electron microscopy after 7 days. Wounds were also inspected for infection and extrusion rates. RESULTS: Results show biofilm formation on titanium, silicone, ion-bombarded silicone, e-PTFE, and PHDPE associated with high rates of extrusion and infection. Implants of e-PTFE with silver/chlorhexidine, on the other hand, appeared resistant to biofilm formation and demonstrated significantly lower rates of extrusion and infection. CONCLUSIONS: Contamination of bioimplants in vivo leads to formation of bacterial biofilm on the surface of the biomaterial, causing infection, pus formation, and extrusion. The authors hypothesize that the antiseptic agents impregnated in the biomaterial form a protective coat of silver, chlorhexidine, and inflammatory cells that inhibits initial bacterial adhesion to the biomaterial surface.
Animals↗
Silicone in nasal augmentation rhinoplasty: a decade of clinical experience.
A number of materials, both biologic and alloplastic, have been used for nasal augmentation. Although biologic bone and cartilage grafts are associated with lower infection rates, they are also associated with long-term resorption and donor-site morbidity. Alloplastic materials, in particular silicone, have been associated in the literature with extrusion and infection but have the advantages of being affordable and easy to reshape with no requirement for harvesting autografts. A 10-year experience with silicone nasal augmentation documenting clinical experience, acute and long-term complications, and patient satisfaction was reviewed. All patients undergoing silicone augmentation rhinoplasty between July of 1985 and December of 1995 were reviewed. Preoperative nasal phenotype, operative data, and postoperative outcome were recorded. Long-term follow-up was undertaken using a telephone survey. There were 422 patients who underwent silicone nasal augmentation from July of 1985 to December of 1995. Only nine were men. The indications were for aesthetic nasal augmentation in 98 percent, and the majority (98 percent) were of South East Asian origin. Mean age was 26 (range 17 to 36), and 41 of the 422 patients had had previous nasal augmentation performed before presentation. Twenty-three patients (5.5 percent) had complications requiring removal of the implant within 30 days of surgery. These included displacement, prominence, hemorrhage, and excessive pressure in addition to obvious supratip deformity. On late follow-up, a further 18 patients (4.3 percent) had subsequent removal of the prosthesis. The most common reason for this was either displacement or over-prominence, more often judged by the surgeon than the patient. There were only two patients (0.5 percent) who had extrusion of the prosthesis. A total of 266 patients (63 percent) were contacted for a telephone interview. The majority of patients (84.2 percent) were satisfied with their nasal shape. Of the 42 patients (15.8 percent) who were not satisfied, 21 patients still wanted further augmentation of their nose. Photographic analysis of 198 patients showed a mean augmentation of 16.5 percent (range 4.0 to 27.5). Amount of augmentation correlated with preoperative nasal phenotype. Silicone nasal augmentation is a safe and effective procedure when used for moderate increases in nasal height. Contrary to previous reports, this series showed no associated infection. If the implant is shaped appropriately to the patient's nasal phenotype, the risk of extrusion may be reduced.
Adolescent↗
Gluttony at the bar: suing for fun and profit.
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Humans↗
Computer-assisted navigation increases precision of component placement in total knee arthroplasty.
UNLABELLED: In our clinical study, 200 total knee arthroplasties were evaluated to compare the use of the OrthoPilot system with conventional mechanical instrumentation. Long-term outcome of total knee replacement depends mainly on the accuracy of implant positioning and restoration of the mechanical leg axis. Our experience was that navigation could achieve a greater degree of accuracy concerning the aforementioned aspects. Among 513 primary-inserted total knee replacements, 100 navigated knees were compared with 100 conventionally implanted knees after matching the two groups of patients by gender, body mass index, age, preoperative deformities, radiographic findings, and operating time. Three weeks after surgery, the radiographic results were significantly better in the computer-assisted group compared with the results in the conventional group when we assessed component positioning in four axes. Only the sagittal tibial component angle was not significantly different. Total knee arthroplasty using the OrthoPilot system led to increased precision of tibial and femoral component positioning in comparison with hand-guided replacement surgery. An additional 10 minutes of operating time was acceptable. Navigation-specific complications were not seen, and the number of outliers decreased. Because computer navigation in orthopaedics is a new technology, data regarding long-term outcomes are not available. LEVEL OF EVIDENCE: Diagnostic study, Level II-1 (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.
Aged↗
A constrained device with increased range of motion prevents early dislocation.
Constrained components can treat or prevent instability after total hip arthroplasty. Some previous designs have shown a high rate of early dislocation. These early dislocations appear to be secondary to component impingement and levering out of the femoral head. We report the early rate of dislocation in 81 consecutive patients undergoing constrained total hip arthroplasty using a novel constrained device that allows substantially more range of motion and a higher lever out strength. One hip redislocated at 6 months followup, for a success rate of 98.8%. The success rate was 93% for patients for whom a constrained device was placed during revision for recurrent instability. This device allows a higher range of motion before prosthetic impingement and maintains a higher levering out strength when impingement occurs. These changes should provide long lasting hip stability in these difficult cases.
Adult↗
Influence of total hip design on dislocation: a computer model and clinical analysis.
Dislocation following hip arthroplasty remains problematic. While the etiology of dislocation may be multifactorial, implant system design may play a role. Using a computer aided design program, virtual range of motion of several commonly implanted designs was performed with prosthetic interference representing impingement used as an endpoint. Implants with small diameter head size (22 mm) and a larger trunion geometry (type II taper) demonstrated impingement in flexion at less than 90 degrees , suggesting an increased risk for dislocation. To investigate this clinically, we performed a review of a consecutive series of 254 primary hip arthroplasties performed by a single surgeon using an implant with a type II taper (Biomet, Warsaw, IN). At a minimum 2 year followup, 12 patients with 12 hips (4.8%) had at least one episode of dislocation. Stratified by head size, the dislocation rates were 3.6% for 28 mm, 4.8% for 26 mm, and 18.8% for 22 mm bearings. These findings support the notion that computer aided design modeling of implant systems is useful in evaluating range of motion and this technique could be employed during the design of any new implant system.
Arthroplasty, Replacement, Hip↗
A novel approach to re-pegging hydroxyapatite implants using bioactive glass.
PURPOSE: To determine if bioactive glass, originally designed for craniomaxillofacial use, can be used effectively for re-pegging of hydroxyapatite orbital implants. METHODS: Over a 2-year period, 3 patients with pegged hydroxyapatite orbital implants and related complications that did not respond to conservative treatment, underwent removal of the implant pegs and/or sleeves. Peg tracts were subsequently filled with bioactive glass. RESULTS: No complications occurred in any case during 3 years of follow-up. After 2 months, 2 patients underwent successful re-drilling of the peg site and insertion of titanium pegs. Both patients were satisfied with the results. The third patient has deferred re-pegging at this time. CONCLUSION: Bioactive glass is effective for refilling old peg tracts and allowing timely re-pegging of hydroxyapatite implants.
Adolescent↗
Replacement of the left-side valves of an implanted total artificial heart.
The MagScrew total artificial heart (TAH) is under development. Despite its anticipated durability and reliability, the possibility of a bioprosthetic valve malfunction exists. As a result, the potential for valve replacement surgery, instead of device replacement, would be desirable after a TAH implant. In two of our 90-day animal experiments, we successfully replaced the left-side valves through a left thoracotomy opposite to the right-sided incision site for the initial TAH implant. The results of these cases suggest that the left-side valves could also be replaced through a left thoracotomy approach in humans. To confirm the ability to access the left-side valves in humans, four human cadaver studies were performed with the use of a mock pump designed for human application. This report describes the operative techniques for left-side valve replacement in animals and discusses the advantages of a left thoracotomy in clinical situations, based on results from the human cadaver studies.
Animals↗