Short Prosthesis Research Articles

Innovative AI-driven design of patient-specific short femoral stems in primary hip arthroplasty

This innovative study proposes a revolutionary strategy to enhance the efficacy and customization of hip arthroplasty, focusing on a short prosthesis design meticulously tailored to individual patient needs, with special emphasis on the femoral stem. The implemented methodology involves data collection through a meshless software, which quantifies the stress/strain shielding resulting from femoral insertion. Automatic pre-processing is performed using clustering algorithms, allowing the data to be divided into anatomical areas of the body. Subsequently, training of machine learning algorithms, such as random forests and stacking, is carried out to accurately predict the shielding caused by the stem. These predictions are based on design parameters, specifically linked to the patient's femoral cavity dimensions and their relationship to stem size, which are quantified through dimensionless parameters and serve as model inputs. The reliability of the models is confirmed by evaluation of data from patient with different femoral morphology than those used during the training and validation phases. This approach not only provides fast and cost-effective analyses for medical experts and engineers, but the described methodology can also be successfully extended to the development of alternative arthroplasty prostheses, such as shoulder and knee implants.

A Study on Revision Stapes Surgery

Between January 2014 and December 2019, we performed 10 revision stapes surgeries at our hospital for hearing loss. We retrospectively reviewed the data of the 10 cases to determine the causes of failure and evaluate the hearing outcomes. The identified reasons for primary surgery failure were eroded incus (4 cases), dislocated prosthesis (2 cases), prosthesis fixation (3 cases), short prosthesis (1 case), malleus ankylosis (1 case), stapes refixation (1 case), and incomplete previous operation (1 case). In 7 of the 10 cases (70%), successful hearing outcomes, as assessed based on the criteria proposed by the Japan Otological Society (2010), were obtained. The postoperative air-bone gap was 10 dB or less in 3 cases (30%), and 20 dB or less in 8 cases (80%). One patient developed sensorineural hearing loss (≥ 15 dB).

Effect of implant length variations on stress shielding in proximal humeral replacement after tumor excision under torsion: Finite element study.

The proximal humerus is the most common site of occurrence of primary bone tumors in the upper limb. Endoprosthetic replacement is deemed as the preferred reconstructive option following primary resection of bone tumors. However, it has been also associated with complications such as stress shielding and aseptic loosening compromising prosthetic survival. Our objective was to conduct a finite element (FE) study to investigate the effect of varying endoprosthesis length on bone stresses as well as to quantify the extent of stress shielding across the bone length (BL) in a humerus-prosthesis assembly for proximal humeral replacement after tumor excision thereby allowing us to identify the optimal implant length with best biomechanical performance. FE models of the intact humerus and humerus-prosthesis assemblies were established where they were loaded at the elbow joint under torsion with the glenohumeral joint fixed to represent twisting. After dividing the bone into individual slices consisting of 5% BL, the maximum cortical and cancellous principal, von Mises and shear bone stresses were calculated. To measure the level of stress shielding, the percentage stress change from the intact state was evaluated across each slice. Similar stress patterns were observed between the intact state and shorter endoprosthesis compared to the longer endoprostheses. Our findings illustrated the possibility of stress shielding occurring under torsional forces with its effect increasing with implant lengthening. To conclude, we believe that using a shorter prosthesis may substantially diminish the risk of potential implant failure due to stress shielding.

Restoration of the joint geometry after stemless shoulder arthroplasty.

This study aims to evaluate restoration of anatomy following Total Shoulder Arthroplasty (TSA) with the Mathys Affinis Short prosthesis. Over the last decade stemless shoulder arthroplasty has increased in popularity. One of the reported advantages of the stemless designs is the ability to restore anatomy following surgery. However, very few studies have evaluated restoration of anatomy following stemless shoulder arthroplasty. The study included all patients who had undergone TSA using the Affinis Short (Mathys Ltd, Bettlach, Switzerland) prosthesis for primary osteoarthritis between 2010 and 2016. The mean follow up was 42.8 months (range 9.4 to 83.4 months). Pre and post-operative radiographs were assessed for Centre of Rotation (COR), Humeral Head Height (HHH), Humeral Head Diameter (HHD), Humeral Height (HH) and, Neck Shaft Angle (NSA) using the best fit circle method on PACS software. Measurements were scored and compared to assess the accuracy of the implant in restoring the native geometry, including the intraobserver variability. The same data was collected by another experienced observer to measure the interobserver variability. The deviation of COR of the prosthesis from the anatomical centre was less than 3 mm in 58 cases (85%). Humeral head height and humeral head diameter showed a variation of less than 3 mm in 66 cases (97%) and 43 cases (63%) respectively. Humeral height followed a similar trend, with 62 cases (91.2%) showing a difference of less than 5 mm. The neck shaft angle showed a variation of more than 8 degrees in 38 cases (55%), and 29 cases (42.6%) had a postoperative angle of less than 130 degrees. Overall, stemless total shoulder arthroplasty with the Affinis Short prosthesis allows excellent restoration of anatomy confirmed by most of the measured radiographic parameters. The variability in neck shaft angle might be due to differing surgical techniques, with some surgeons preferring a slightly vertical neck cut to protect the rotator cuff insertion.

Midterm clinical and radiologic survivorship of a stemless total shoulder arthroplasty.

The aim of this study was to evaluate the clinical and radiologic outcomes of stemless total shoulder arthroplasty (TSA) in patients with glenohumeral arthritis. This is a retrospective case series of all patients who underwent a TSA with Affinis Short prosthesis during the period 2010-2017. Seventy-two TSAs were performed within our unit, in 62 patients (45 females and 17 males), with 10 patients having bilateral TSAs with this prosthesis. The mean follow-up was 3.9 years (2-8.7 years). Patients were evaluated clinically with the Oxford Shoulder Score, range of movement assessment, and a numerical patient satisfaction score. Follow-up radiographs were evaluated by 2 reviewers assessing for lucency and assigned a Lazarus grade. Six patients were lost to follow-up prior to their 2-year review. At last follow-up, the mean forward elevation was 157° (80°-180°), abduction was 150° (60°-180°), and external rotation was 39° (20°-60°). The mode internal rotation was to the lumbar spine, with 95% of patients achieving internal rotation to L5 or higher. The mean Oxford Shoulder Score was 45 (18-48). The mean patient satisfaction score was 4.93/5. No humeral lucencies were observed. Sixty-four percent (n=47) of the glenoids were Lazarus grade 0, showing no evidence of radiolucency. The remaining patients were Lazarus grade 1-3, although none were progressive and all patients were asymptomatic. No patients were revised for aseptic loosening. Four patients underwent revision: 1 for infection, 1 for heterotrophic ossification and stiffness, and 2 for rotator cuff failure. Midterm follow-up results indicate good clinical and radiologic survivorship for this stemless TSA. Our findings suggest good patient function and satisfaction, and no patients have required revision for aseptic loosening. Further follow-up is required to determine long-term survivorship.

Complications following secondary voice prosthesis insertion and impact of previous irradiation on their appearance.

The aim of this study was to analyze the complications following secondary voice prosthesis insertion and impact of previous irradiation on their appearance. This study included 106 totally laryngectomized patients who underwent secondary Provox 2 voice prosthesis insertion. Among them, 79 (74.5%) were irradiated. Surgery, prosthesis, fistula, and voice-related complications were analyzed and presented. Complications occurred in 23 (22%) patients. Fifteen of them were previously irradiated. There were no surgery-related complications. In the group of prosthesis-related complications, one patient had increased negative pressure during swallowing with extremely short prosthesis life time. There were 17 complications in the group of fistula related ones; 3 patients had excessive granulation tissue around the fistula and 14 patients experienced prosthesis displacement (7 had closed esophageal end of the fistula, 5 had the prosthesis turned sideways in an open fistula, one patient inhaled and one ingested the prosthesis). Tracheoesophageal voice was not established in 5 patients. Previous irradiation had no statistically significant influence on the complication rate (P = 0,251). The majority of complications following secondary voice prosthesis insertion are fistula-related ones, among which, displacement of the voice prosthesis is the most common. Previous irradiation does not significantly increase the risk of developing complications.

Clinical results and survivorship of the Mathys Affinis Short, Short Stem Total Shoulder Prosthesis.

AimsThe Mathys Affinis Short is the most frequently used stemless total shoulder prosthesis in the UK. The purpose of this prospective cohort study is to report the survivorship, clinical, and radiological outcomes of the first independent series of the Affinis Short prosthesis.MethodsFrom January 2011 to January 2019, a total of 141 Affinis Short prostheses were implanted in 127 patients by a single surgeon. Mean age at time of surgery was 68 (44 to 89). Minimum one year and maximum eight year follow-up (mean 3.7 years) was analyzed using the Oxford Shoulder Score (OSS) at latest follow-up. Kaplan-Meier survivorship analysis was performed with implant revision as the endpoint. Most recently performed radiographs were reviewed for component radiolucent lines (RLLs) and proximal humeral migration.ResultsFive shoulders underwent revision surgery (3.5%); three for rotator cuff failure, one for infection, and one for component malposition. Survivorship of the implant was 95.4% (95% confidence interval 90.1% to 97.9%) at five and nine years. Mean OSS improved significantly compared to preoperative values from 19.0 (1 to 35) to 43.3 (7 to 48) (p < 0.001). Radiological analysis was undertaken for 99 shoulders. This revealed humeral RLLs in one case (1%), glenoid RLLs in 15 cases (15.2%), and radiological rotator cuff failure in 22 cases (22.2%).ConclusionThis prospective cohort study shows encouraging short- to mid-term survivorship and clinical and radiological results for the Mathys Affinis Short, Short Stem Total Shoulder Prosthesis.Level of Evidence: IVCite this article: Bone Jt Open 2021;2(1):58–65.

Conductive hearing loss after surgical treatment of otosclerosis - long-term observations.

&lt;b&gt;Introduction:&lt;/b&gt; For many years, surgical treatment of otosclerosis has been a widely accepted approach. Hearing improvement following stapes surgery is sometimes spectacular, and good treatment results are obtained in many centers in over 90% of patients. However, in the subsequent years after the treatment, some patients develop permanent or progressive conductive hearing loss. &lt;br&gt;&lt;b&gt;Aim:&lt;/b&gt; The aim of the study is to present a group of patients with conductive hearing loss after the first otosclerosis surgery and to analyze the causes of its occurrence. &lt;br&gt;&lt;b&gt;Materials and Methods:&lt;/b&gt; The retrospective review covered patients who underwent the initial surgery in the years 2000-2009. We analyzed the patients' medical records from before the end of 2019, which provided results of at least 10 years of postoperative follow-up. The group consisted of 1118 patients aged 14-82, including 802 women and 316 men.&lt;br&gt;&lt;b&gt; Results:&lt;/b&gt; Reoperations due to conductive hearing loss were performed on 93 patients, who accounted for 8.3% of the originally operated patients. They were much more common in patients after stapedectomies (19.7%) than in patients after stapedotomy (5.5%). Prosthesis dislocation was found to be the most frequent intraoperative observation (44.1%) and was often associated with erosion or necrosis of the long process of incus (28%). Less frequent reasons for hearing loss were: adhesions around the prosthesis (10.8%), too small hole in the stapes footplate (8.6%), too short prosthesis (8.6%), progression of otosclerosis (7.5%), too long prosthesis (6.4%), presence of a granuloma around the prosthesis (5.4 %), and displacement of incus (4.3%). &lt;br&gt;Conclusions:&lt;/b&gt; Surgical treatment of otosclerosis is a widely accepted and good method. It allows to achieve an improvement in hearing in the vast majority of patients treated in this way. Unfortunately, over the years some patients develop recurrent conductive hearing loss. Reoperation creates an opportunity for finding the cause and improving hearing in the majority of cases.

Rehabilitation Program Using Short Prostheses after Bilateral Transfemoral Amputation: A Case Report

ABSTRACT Introduction Individuals with bilateral lower-limb (LL) amputations require more energy when using bilateral prostheses compared with those who have unilateral LL amputations. A short prosthesis is often used to determine whether someone will be functional using a more advanced prosthesis long term. Patient Information This case report describes physical therapy interventions for a 72-year-old male subject in subacute rehabilitation after a bilateral transfemoral amputation secondary to peripheral artery disease (PAD). At initial examination, the patient was dependent for all transfers and unable to sit unsupported. Intervention The interventions were done in three phases. Phase 1 focused on trunk strengthening, postural control, sitting and standing balance, and standing tolerance using short prostheses on a tilt table. Phase 2 progressed to dynamic standing activities using a tilt table and LiteGait with the goal to increase standing tolerance. Phase 3 focused on transfers and gait with assistance from the LiteGait and a platform walker. Outcomes After 8 weeks of rehabilitation, the patient achieved all short-term goals (STGs) and made 75% progress toward meeting his long-term goals. His Functional Balance Grades Scale (FBGS) score increased from poor to fair, whereas his Functional Independence Measure (FIM) scores for transfers and ambulation increased from 3 to 4 and 0 to 1, respectively. Discussion There is limited information in the literature on progressing exercise programs in individuals with bilateral transfemoral amputation. Physical therapists may wish to consider the interventions described in this case report when designing programs for individuals with bilateral transfemoral amputation.

Treatment of Severely Atrophic Edentulous Mandible Fractures: Load-Bearing or Load-Sharing?

Several nonsurgical and surgical techniques have been employed to treat fractures of the severely atrophic mandible. The aim of this study was to analyze the repair outcome of these fractures. From 2010 to 2016, patients with fractures of the severely atrophic mandible were included. All files were retrospectively studied. Twelve patients (mean age: 76 years; female, n = 8) with a single ( n = 6) or multiple fracture(s) of the atrophic edentulous mandible (mean height was 10.1 mm) were identified. Fracture occurred following trauma ( n = 9), explantation of dental implants ( n = 2), and placing an overdenture bar ( n = 1). In seven cases, consolidation was successful following open reduction and internal fixation (ORIF) using a load-bearing reconstruction plate. In five cases, the initial treatment was different: conservative treatment, using gunning splint, and performing ORIF using miniplates. In all five cases, additional ORIF using a load-bearing reconstruction plate was needed. In four cases, short dental implants were placed several months following fracture repair. In case of a severely atrophic mandibular fracture, the authors advise ORIF with a load-bearing reconstruction plate. In selected cases, secondary oral rehabilitation with short dental implants and implant-supported prosthesis is feasible.

The process of becoming a user of an osseointegrated prosthesis following transfemoral amputation: a qualitative study

Purpose: To investigate what characterizes the process of becoming a user of an osseointegrated prosthesis following transfemoral amputation.Method: The study is based on the descriptive phenomenological framework Reflective Lifeworld Research. Data were collected through in-depth interviews with seven participants who had undergone transfemoral implant surgery and currently used their osseointegrated prosthesis. Data were analyzed according to the guidelines given in Reflective Lifeworld Research.Results: The essential meaning of becoming a user of an osseointegrated prosthesis is characterized by determination to achieve rehabilitation results as well as a struggle to get familiar with the new prosthesis. When familiar with the prosthesis, participants begin to experience radical improvements in their everyday life, compared to their life with the socket suspended prosthesis. The essential meaning is elaborated on in four constituents: Determination to achieve rehabilitation results with the short training prosthesis, struggling to get familiar with the osseointegrated prosthesis, experiencing improvements in everyday life and reconnecting with one’s prior self-perception.Conclusion: All the participants experienced increased action space and a more positive outlook on life. However, it took determination and stamina to become a user of an osseointegrated prosthesis, and participants faced several challenges throughout this process. Consequently, it remains important to raise awareness of the difficulties faced during this process.Implications for RehabilitationThe findings from this study suggest an increased healthcare support to users of an transfemoral osseointegrated prosthesis in the period of rehabilitation and adjustment, as the results of being able to use the osseointegrated prosthesis may outweigh the obstacles of getting there.Implementation of long-term follow-up and psychosocial support initiatives may improve the adjustment process following osseointegration.Support of patients with an osseointegrated prosthesis may be facilitated through formation of specific rehabilitation groups together with increased use of information technology such as social media and relevant online communities which provide forums for interaction and dialog with people in similar situations.

Use of short prosthesis segments for brachiocephalic arteriovenous fistulas in elderly hemodialysis population

IntroductionThe autogenous brachiocephalic fistula is a recognized secondary access for hemodialysis. However, veins in the antecubital fossa are often damaged, due to repeated venipunctures and subsequent scarring. Sometimes their anatomy does not enable successful arteriovenous fistula creation. In cases when the proximal part of the cephalic vein seemed patent, during ultrasound Doppler examination, we decided to use a short segment of 6 mm polytetrafluoroethylene graft to connect the vein with the brachial artery. We report our series of this procedure.Material and methodsOver an 8-year period, 34 patients underwent such an operation. Grafts were anastomosed either to the end of the cephalic vein or to the side. The decision was made based on the vein condition: small-caliber veins were considered better for the end-to-side anastomosis. All procedures were performed under local anesthesia, and were well tolerated.ResultsThirty-three fistulas were successfully cannulated at 2-8 weeks after the operation. Fistula patency rates were 84%, 73% and 55% at 12, 24 and 36 months. Comparison of two anastomosis types showed differences, 50% and 62.8% at 36 months, yet without statistical significance (p = 0.27, log-rank test). Fistula patency was not influenced by patient's age, sex or comorbidities.ConclusionsThe described procedure provides satisfactory cumulative patency with an acceptable complication rate. It can enhance the number of cephalic veins used with its main advantages of simple surgical technique and low perioperative morbidity.

CO2 laser revision stapedotomy

To evaluate the safety and efficacy of the one-shot noncontact technique in stapedotomy for revision stapes surgery with a CO₂ laser combined with a scanning system. Prospective study. Intraoperative findings and hearing results of 106 patients who underwent revision CO₂ laser stapedotomy because of conductive or sensorineural hearing loss or vertigo were analyzed. Leading pathologies were displacement of the prosthesis, incus erosion, fibrous adhesions, and bony reobliteration or a too long or too short prosthesis. Surgery was successfully performed in all cases with a noncontact technique resulting in significantly improved postoperative air and bone conduction. The rate of permanent complications was 0.9%. A comparison of the effect of higher laser energies used for the perforation of bony stapes footplates and lower energies for neomembranes revealed no significant difference in hearing results, underscoring the safety of the technique. To avoid any manipulation of the conductive hearing chain that may cause sensorineural hearing loss, we adapted the noncontact technique previously introduced by us for use in revision stapedotomy. This technique was successfully applied to improve conductive and sensorineural hearing loss as well as vertigo in first and second revision stapedotomy cases. Because the rate of postoperative complications was comparable to what is achieved with other laser systems, we conclude that the method has at least an equal level of safety. In conclusion, we advocate the use of a noncontact technique as suitable for an early revision of failed stapedotomy.

Telescope Allograft Method to Reconstitute the Diaphysis in Limb Salvage Surgery

We propose a surgical technique for structural allograft reconstitution of the diaphysis of long bones, maximizing surface contact between host and allograft bone. This method, analogous to a telescope, overlaps the graft and host bone, theoretically increasing bone surface contact substantially. We report the outcome of 22 telescoped allograft junction sites in 19 patients who lacked sufficient host bone to accommodate a regular-length stemmed implant. This joint-sparing reconstruction preserved 15 of 16 adjacent joints at risk for replacement. Five patients needed additional surgery, but none for nonunion. The diaphyseal length could be reconstructed enough so that a short prosthesis (less than the critical 40% of total bone length) could be used. This biologic method to reconstruct major segments of the diaphysis is best suited for patients with quantitatively or qualitatively deficient residual bone stock after tumor resection or prosthetic revision. We believe it is an excellent technique for revision knee megaprostheses when there is a short remnant of proximal femur. Level IV, therapeutic study.

Coil embolization of an anastomotic leak after ascending aorta replacement

Surgical treatment of diseases of the thoracic aorta (aneurysms, dissections, and ruptures) may be associated with serious postoperative complications. Endovascular repair of thoracic aorta pathology is less invasive and offers a therapeutic alternative in high-surgical-risk patients, particularly in the presence of previous surgical repair of the thoracic aorta. The endovascular procedure, however, is almost only possible in the descending thoracic aorta, although advances have also been made in the aortic arch as well as in the ascending aorta with branched stent grafts. We report a case of a surgically treated aneurysm in the ascending thoracic aorta complicated with an anastomotic leak. If a short prosthesis (6 cm) had been available, the anastomotic leak would have been treated with endovascular repair. In lack of this prosthesis, we were forced to treat the patient with a method not generally accepted--embolization with endovascular coils--successfully resulting in occlusion of the leakage.

Endoskopische Behandlung von malignen Gallengangsstenosen mit Endoprothesen

In 65 patients (36 men, 29 women; mean age 74 [43-90] years) obstructive jaundice caused by malignant biliary stenosis was treated by endoscopic retrograde insertion of a 10 or 12 F synthetic endoprosthesis. The rate of complications of the endoscopic intervention was 5% (n = 3), 30-day mortality rate was 11% (n = 7) and method-related mortality was 8% (n = 5). Good drainage was achieved in 39 of 41 patients (95%) with the 12 F endoprosthesis, and in 15 of 21 patients with a 10 F one (71%) (P less than 0.001). Renewed jaundice due to prosthesis occlusion occurred in 31 patients an average of 103 (11-350) days after placement. Interval until occlusion correlated with the site of the stenosis and the length of the endoprosthesis. Jaundice recurred earlier in patients with long prostheses and proximal biliary stenosis than in those with a short prosthesis and distal stenosis. In 20 patients with renewed jaundice the endoprosthesis was replaced endoscopically. At that time 13 of the patients had a cholangitis. Occlusion of the new endoprosthesis was more common in patients with cholangitis (9 of 13) than those without (2 of 7; P less than 0.05). These findings indicate that endoscopic biliary tract drainage should be performed with as short a 12 F endoprosthesis as possible. In view of the potential need for early change of endoprosthesis the biochemical parameters of cholestasis should be regularly monitored.

Long-Term Results of Venous Bypass for Lower Extremity Arteries with Selective Short Segment Prosthetic Reinforcement of Varicose Dilatations

The long-term benefit of venous bypass has been clearly demonstrated, but procedure feasibility is contingent upon availability of a suitable vein. In this study, we evaluated the outcome of venous bypasses performed by the first author using veins presenting dilatations that were selectively reinforced with a short prosthesis. The purpose was to answer three questions. First, should ectasis be reduced before reinforcement? Second, do hyperplasia and stenosis develop in reinforced zones? Third, do dilatation and rupture develop in unreinforced zones? Twelve patients, including 10 men and 2 women ranging in age from 36 to 77 years (median 68), underwent bypass for peripheral artery disease in seven cases, popliteal aneurysm in four, and prosthetic rupture in one. Ten patients had poor distal runoff. The bypass was femoral-to-popliteal in eight cases, femoral-to-infrapopliteal in three, and popliteal-to-popliteal in one. The graft was reversed in nine cases and ex situ devalvulated in three. The number of prosthetic reinforcements used was one in two cases, two in three cases, three in six cases, and four in one case. All but one prosthetic reinforcement were made of polytetrafluoroethylene (PTFE). Bypass occlusion was observed in two cases, including one case observed in the early postoperative period after bypass for limb salvage in a young man in whom distal runoff was limited to a few collaterals and one case that occurred 4 years after a repeat bypass procedure. The other 10 bypasses remained patent throughout follow-up, which varied from 1 to 11 years (median 4). There were three deaths during follow-up. Doppler ultrasound revealed no stenosis in the reinforced zones and no dilatation in the unreinforced zones but demonstrated progressive deterioration of the runoff in 50% of cases. At the last follow-up examination, two bypasses were patent despite poor runoff. Although the number of patients in this series was small, the outcome of venous bypass using reinforced vein grafts appeared clearly better than outcomes of prosthetic bypass reported in the literature. Reinforcement can be easily achieved using a short, thin-walled PTFE prosthesis adjusted to the proper diameter by gentle dilatation using forceps. Unlike most authors, we do not recommend reducing dilatation by resection or oversewing. Reinforced zones did not develop stenosis and unreinforced intermediate zones showed little or no dilatation and no risk of rupture.

Surface Myoelectric Signal Analysis: Dynamic Approaches for Change Detection and Classification

Toward the goal of elbow and wrist prostheses control by characterizing events in surface myoelectric signals, this paper presents a dynamic method to simultaneously detect and classify such events. Dynamic cumulative sum of local generalized likelihood ratios using wavelet decomposition of the myoelectric signal is used for on-line detection. Frequency as well as energy changes are detected with this hybrid approach. Classification is composed of using multiresolution wavelet analysis and autoregressive modeling to extract signal features while polynomial classifiers are used for pattern modeling and matching. The results of detecting and classifying four elbow and wrist movements show that, in average, 91% of the events are correctly detected and classified using features obtained from multiresolution wavelet analysis while 95% accuracy is achieved with AR modeling. The classification accuracy decreases, however, if short prostheses response delay is desired. This paper also shows that the performance of the polynomial classifiers is better than that of the commonly used neural networks since it gives higher classification accuracy and consistent classification outcomes. In comparison to the well known support vector machine classification, the polynomial classifier gives similar results without the need to optimize and search for classifier parameters.

Migration and cyclic motion of a new short-stemmed hip prosthesis – a biomechanical in vitro study

Uncemented, short-stemmed hip prostheses have been developed to reduce the risk of stress shielding and to preserve femural bone stock. The long-term success of these implants is yet uncertain. Prerequisite for osseointegration is sufficient primary stability. In this study the cyclic motion and migration patterns of a new short-stemmed hip implant were compared with those for two clinically successful shaft prostheses. The prostheses were implanted in paired fresh human femura and loaded dynamically (gait cycle) with increasing load (max 2,100 N) up to 15,000 cycles. Relative displacements between prosthesis and bone were recorded using a 3D-video analysis system. The short stem displayed a biphasic migration pattern with stabilisation at maximum load. Initial migration was predominantly into varus and was greater than that for the shaft prostheses. Failure occurred in cases of poor bone quality and malpositioning. Cyclic motion of the short prosthesis was less than that for the shaft prostheses. Surface finish showed no effect. System stiffness for the new stem was lower than for the shaft prostheses. The new stem tended to migrate initially more than the shaft prostheses, but stabilised when cortical contact was achieved or the cancellous bone was compacted sufficiently. Bone quality and correct positioning were important factors for the short stem. The lower cyclic motion of the new stem should be favourable for bony ingrowth. The lower system bending stiffness with the new implant indicated a more physiological loading of the bone and should thereby reduce the effects of stress shielding.

Léiomyosarcome du segment moyen de la veine cave inférieure : problèmes tactiques soulevés par la revascularisation cave et rénale

Introduction Leiomyosarcoma of the inferior vena cava is mesenchymal tumor accounting for 95% of primary tumors of the vena cava. Characteristic features include late invasion of adjacent structures and metastases, and delayed diagnosis. Observation We report a case of inferior vena cava (IVC) leiomyosarcoma (LMS) found in a 53 year-old man who complained of abdominal pain. Morphologic exams found a very large polycyclic mass in the inferior vena cava involving the middle segment of the vena cava extending from the renal veins to the hepatic veins. An «en bloc» resection of the tumor was achieved. Caval outflow was restored using a ring-reinforced PTFE tube graft, the left renal vein was ligated and not re-implanted, the right renal vein was implanted in a lumbar sub-renal vein using a short prosthesis. Pathological examination documented a grade II leiomyosarcoma of the inferior vena cava and the patient was given adjuvant chemotherapy (anthracycline). One year later, there was no local or regional relapse. Comment We emphasize the importance of restoring caval outflow which provides effective results when used with a ring-reinforced polytetrafluoroethylene (PTFE) prosthesis. Furthermore, the importance of restoring right renal outflow is highlighted because ligature of the renal vein can lead to renal ischemia and nephrectomy which should only be performed in specific cases. The tactical problems of renal and caval revascularisation, including the place of prosthetic replacement, are discussed. (J Mal Vasc 2006; 31: 79-84).