Aim. Our aim was to evaluate the prevalence and impact of unexpected intraoperative cultures on the outcome of total presumed aseptic knee and hip revision surgery. Method. Data regarding patients prospectively recruited in our center, who had undergone elective complete hip and knee revision surgery from January 2003 to July 2017 with a preoperative diagnosis of aseptic loosening was retrospectively reviewed. Partial revisions and patients with follow up below 60 months were excluded from the study. The protocol of revision included at least 3 intraoperative cultures. Failure was defined as the need for re-revision due to any-cause at 5 years and/or the need for antibiotic suppressive therapy. Results. A total of 608 cases were initially included in the study, 53 patients were excluded. 123 hip and 432 knee revision surgeries were included. 420 cases (75.7%) had all cultures negative, 114 (20.5%) a single positive culture or two of different microorganisms and 21 (3.8%) had at least 2 positive cultures for the same microorganism. Early failure was found in 4.8% (1/21) of the patients with missed low grade infection. The presence of positive cultures during total exchange was not associated with a higher failure rate than in those with negative cultures (44 of 420, 10.5%). In contrast, patients revised before 24 months had a significant higher rate of re-revision, 18% (15/83) vs. 8.4%. Conclusions. Total hip and knee revisions with unexpected positive cultures were not significantly associated with a higher re-revision risk at 5 years of follow-up. Representing an overall good prognosis. However, revision surgeries performed within the first 24 months have a higher rate of failure

To wake up in the morning facing a complex total hip revision can be unpleasant. Modern designs have greatly facilitated dealing with the most difficult revision situations both on the acetabular and femoral side. The surgeon faces blood loss, dislocation, infection, and a litany of other potential complications. Our advances in total hip revision have been outstanding but can pose very complex issues. Total knee revision on the other hand is easier. The surgeon needs to ask a series of questions pre-operatively and intra-operatively. Pre-operatively, one must know the mechanism of failure. You also need to know “what is missing” in terms of skin, soft tissue, extensor mechanism, bone and ligaments. Intra-operatively, the surgeon must know the difference between the flexion and extension gap, the position of the joint line, the extent of the bone loss and whether it is load bearing or non-load bearing, the ligamentous stability and the intramedullary shaft. Most modern knee revision designs allow the surgeon to create a paradigm to deal with all of these potential problems. There, of course, are complex problems of malalignment, periprosthetic fracture and other deformities that add a level of complexity but most of these can be dealt with using standard revision designs without requiring custom prostheses

Introduction. Bone loss management represents one of the most challenging issues for the orthopaedic surgeon. In most cases, stems, structural allograft, TMcones, and sleeves are adequate to allow optimal implant stability and durable fixation. In selected cases of wide metadiaphyseal bone defects, these devices do not provide proper intraoperative stability. In such scenarios, further steps are needed and include complex modular reconstruction, substitution with megaprosthesis (exposing patients at high risk of early failure) or joint arthrodesis that can yield unacceptable results. The aim of this paper is to present early results obtained with a new custom-made implant for complex metadiaphyseal bone defects management in knee revision surgery. By means of case presentations the authors would highlight the possibilities and technical notes of this novel device in complex knee revision surgery. Methods. Since2015, 8 custom-made porous titanium devices were implanted for massive bone defect management in 6 knee arthroplasty revision procedures. Five patients were staged revision for periprosthetic joint infection (PJI) and one patient underwent a staged revision for post-traumatic septic arthritis. Main demographic and surgical data were collected. Clinical (Range of Movement [ROM], Knee Society Score [KSS] and Oxford Knee Score [OKS]), radiological findings and complications were recorded at different time points and statistically evaluated. Mean follow up was 19.5 ± 9.6months. Results. The study group included 4 males and 2 females with a mean age of 63.7 ± 5.5 years and a mean Body Mass Index of 29.3 ± 4.1. Globally, the mean number of previous surgeries was 4.8 ± 2.7. The custom made device was combined with a hinged prosthesis in 5 cases and with a constrained condylar implant in 1 patient. Hybrid fixation was used in all cases. The mean KSS and OKS of the entire population improved significantly from 35.3 ±6.5 and 19.2 ±3.5 preoperatively to 85.8 ±4.0 and 39.3 ±3.1 at the time of last follow-up evaluation (p<0.01). The range of motion improved from 46.7 ±9.8 of mean preoperative flexion and 7.8 ±6.8 of mean preoperative flexion contracture to 93.3 ±10.3 and 1.2 ±2.9 respectively (p<0.01). Radiological analysis showed no migration or implant loosening. No intraoperative or postoperative complication was recorded. One patient required a prolonged antibiotic therapy for positive culture samples of sonication of the retrieved spacer. No implant mismatch between the preoperative planning and the final implant was reported. Conclusion. The presented custom-made implant showed promising early clinical and radiological results. In extremely selected cases, this new device can be considered a safe and effective surgical step between “off the shelf” reconstruction implants and knee substitution with a tumor megaprosthesis. Accurate surgical planning and intraoperative management of soft tissues and residual bone stock are of paramount importance

Introduction. The legion knee revision system was designed as a follow and improvement to the Genesis II knee system- allowing for a surgeon directed femoral rotation as opposed to the in-built femoral rotation in the previous system. This is a prospective review of consecutive patients who underwent knee revision surgery using the legion knee system. Methods. Clinical and functional assessments were carried out preoperatively, one year and 2 years post op. Radiographic evaluation was done at 1 and 2years follow up. Standard knee scoring systems (American Knee Scores-AKS, and Oxford score were used for the clinical and functional evaluation of these patients. The WOMAC score was also used to assess for pain, stiffness and social function in these patients. The radiographic assessment included review of standing AP, lateral and skyline views. Figgie's method was used to measure the joint line reproduction. A difference of 5 mm (pre = op/post-op) was deemed satisfactory. Results. Seventy-five consecutive patients underwent revision knee system- 38 male: 34 females with a mean age of 71.2 (50–87 yrs.). Mean BMI-26.03, (Range 11–50). We had a 2-year follow up for 32 patients Surgery was carried out at a single centre and performed by members of the Bristol knee group. Indications for surgery in these patients- were aseptic loosening (38), instability (15), pain and stiffness (7), polyarthropathy (2), ligament laxity (3), peri-prosthetic fractures (3), and impingement (4). The mean American Knee scores, and WOMAC scores at, 1 year and 2 years follow up showed significant improvements in pain and function. It was also noted that the mean oxford knee score improved from 14/48 pre-operatively to 34/48 at 2yrs. Radiographic assessment showed a mean AP coronal femoral angle of 95.3 degrees (range 89.6–99.9 degrees), coronal tibial angle of 90.1 degrees (Range 88–92 degrees). The mean sagittal femoral and tibial angles were 88.4 and 90.4 degrees respectively. Mean Kappa value for the inter observer reliability for the radiographic assessment was 0.50 showing agreement, with standard error measurement of 1.2. The joint line was reproduced in all cases. Discussion. The short-term results with the Legion Knee revision system showed significant improvement in functional and pain scores in these patients irrespective of their indications for revision surgery. Overall the legion system has showed good outcome scores that match or beat published series on revisions. It also showed a good ability to restore joint line. Ongoing work needed to refine indications and realistic outcomes for different diagnoses

Introduction: knee revision in absence of Extensor Mechanism has been always a challenging problem in Orthopaedics. Many authors are in favour to abandone any endoprosthetic substitution in front of such a situation. We think osteotendinous allografts, in this particular case whole Extensor Mechanism allografts, could play an essential role before any Knee Arthrodesis. Material and Method: From 1999 up to 2004 11 patients (4 male, 7 female) (mean age 72, range 68 to 86) underwent to a whole Extensor Mechanism allografting procedure. Mean follow up was 2.7 years (1 to 5 years). In the first four cases a whole Extensor Mechanism allograft was implanted, while the next seven cases the allograft was reinforced by means of a Leeds-Keio Dacron band. Results: There was no infections in this serie. The mean obtained R.O.M. in the first three months was – 5 of active extension (range 0 to −15) and 95 active flexion (range 80 – 110). However 3 from the 4 former operated cases had a progressive loss of active extension up to −25 (range −20 to −35) at 18 months, that did not increase after this period. Ultrasonic exams showed a lengthening of the patellar tendon in these cases. None of these 3 patients wished to undergo to a patellar tendon reinforcement. On the other hand those later cases, where patellar tendon was reinforced did not show any change over the time (at 18 months mean active extension was maintained to −5 (range 0 to 15). Conclusions: Extensor mechanism allografts are very useful in difficult knee revisions with absence of extensor mechanism, so that knee arthrodesis is not the method of choice for these patients. However augmentation of patellar tendon is necessary to maintain with the years an active extension

Introduction. 3 main challenges encountered in knee revision of Asians:. systemic: such as osteoporosis and laxity. anatomical variance: established in literature making revision system not appropriate. Neglected case revised late owes to extensive bone loss demanding bone substitute and increased constrain. Therefore we like to alert surgeon apprehending enhanced challenges while indulging in revision of Asian. Our emiratus author with USA background/qualification/experience has excuted 216 revision in 8yrs with at least 3yrs follow-up. Material & Method. Between 2003–2010 we performed 216 revision TKR, reviewed all parameters & compared our results with European revision statistics depicting a) intermedullary canal smaller b) metaphysis narrower & more triangular in comparision to Caucasian causing housing mechanism fit impossible, also increase impingment of stem at times. Bone loss is normally quiet extensive & available implant including the Tantalum cone sometimes is difficult to fit in a tight metaphyseal area, we had satisfactory outcome inspite of owing to intra-operative complication which lead to 3 intramedullary fracture resulting from inadequate avalibity of smaller size, incomplete seating of tibial component, overhang of femoral component.it also leads to more translucent line quoted in 15 cases. Centre of IM canal in both tibia & femur is positioned more posteriorly especially in smaller size proven by CT anatomical study analysis. These data we related to anatomic variance rather then surgical technique therefore representing deficit of proper size thereby contributing to inability to surgeon. Conclusion. Restoring joint line to tibia to prevent impingment of tibial housing is crucks, enabled by utilizing certain surgical tricks which all surgeon revising small stature Asian should bear in mind.in certain instances use totally cemented stubby stem. 2 important aspect of our abstract:. a). Present: we will review all tricks enabling appropriate/maximum utilization of inadequate current revision system. b). Future: we will also present specific recommendation to Industry based on anatomy variation alerting them need of. 1). asymmetrical tibial component. 2). natural femoral component. 3). repositioning of stem. Multiple factors contributes more challenges in Asian revision:. 1). mainly anatomy attributed to metaphyseal morphology. 2). unable to apply certain surgical tricks to fit implant in small patient. strong recommendation to Industry to alter revision system inorder to achieve more success in Asian revision surgery

Increasing age and a higher level of mobility lead to an increasing incidence in revision arthroplasty after total knee replacement and tumor surgery. So far, the reconstruction of large defects in bony and soft tissue environments can be accomplished by the modern modular components of revision implants. The consecutive reconstruction of the extensor mechanism in extended revision has its own drawbacks and is often associated with significant functional limitations for the patient. Specially designed implants and methods are required to generate good functional. Results: The modular knee revision system MML provides specific modifications of the tibial component for reconstruction of the extensor mechanism. Combined with artificial strips, an excellent functional outcome could be achieved. In this study, 70 patients were operated with the MML endoprosthesis in knee revision or tumor surgery. An excellent functional outcome could be determined. At 7 years after surgery, an average of 32±13 points was achieved on the Oxford Knee Score. The outcome measurement using the functional scoring system of the American Knee Society (AKS score) showed similarly good results with 71±25 points out of 100. A minor deficit of only 2° in active extension could be observed after reconstruction of the extensor mechanism. In conclusion, we have demonstrated that the MML modular revision system is appropriate for reconstruction of segmental bone defects

The designs available today have greatly improved our ability as surgeons to perform successful total knee revision surgery. However, as more and more knee replacements are in service for longer periods of time, the numbers of revisions have increased and have required us as surgeons to address challenging problems including infection, instability and bone loss from wear, osteolysis and loosening. Understanding the problems needed to be addressed is paramount. Careful preoperative planning is key. Knowing the cause of failure and the aspects of reconstruction that need to be addressed including skin, soft tissues, extensor mechanisms, bone and ligament loss is critical. Intraoperatively, understanding and applying principles related to establishing joint lines, balancing flexion extension gaps, addressing bone loss and ligament instability and constructing stable knee replacements with the use of stabilising implant articulations, bone deficiency reconstruction with augments and grafts as well as cones and sleeves, and stems for implant stability is also essential. Postoperatively, rehabilitation and follow-up must be tailored to the individual patient because of the marked nuances of construct in the various revision scenarios

This is a prospective review of consecutive patients who underwent knee revision surgery using the Legion knee system. Clinical and functional assessments (American Knee Scores-AKS, WOMAC and Oxford knee score-OKS) were carried out preoperatively, one year and 2 years post op. Radiographic evaluation was done at 1 and 2 years included review of standing AP, lateral and skyline views. Figgie's method was used to measure the joint line reproduction. 210 patients underwent revision knee system 103 male: 107 females with a mean age of 66.4 (44–87) yrs. Mean BMI-26.03 (21–50). We had a 2-year follow up for 110 patients. Surgery was carried out at a single centre and performed by Bristol knee specialists. Indications for surgery were aseptic loosening (84), infection (27) instability (47), pain and stiffness (31), progression of disease (6), peri-prosthetic fractures (15). The AKS and WOMAC scores at, 1 year and 2 years follow up showed significant improvements in pain and function. The mean total AKS improved from 75.7/200 pre-operatively to 140.5/200 at 2 yrs. Radiographic assessment showed a mean AP coronal femoral angle of 95.3 degrees (89.6–99.9), coronal tibial angle of 90.1 degrees (88–92). The mean sagittal femoral and tibial angles were 88.4 and 90.4 degrees respectively. The short-term results showed significant improvement in functional and pain scores irrespective of indications for revision surgery. The Legion system has showed good outcome scores that match or beat published series on revisions. It also showed a good ability to restore joint line

Aim. Femoral or tibial massive bone defects (AORI F2B-F3 / T2B-T3) are common in septic total knee replacement. Different surgical techniques are described in literature. In our study we show clinical and radiological results associated with the use of tantalum metaphyseal cones in the management of cavitary bone defects in two-stage complex knee revision. Method. Since 2010 we have implanted 70 tantalum metaphyseal cones associated with constrained or semiconstrained knee prostheses in 47 patients. The indication for revision was periprosthetic knee infection (43 cases, 91.5%) or septic knee arthritis (4 patients, 8.5%) with massive bone defect. All cases underwent a two-stage procedure. Patients were screened for main demographic and surgical data. Clinical and radiological analysis was performed in the preoperative and at 3,6 months, 1 years and each year thereafter in the postoperative. The mean follow-up was 31.1 months ± 18.8. No dropout was observed. Results. Objective and subjective functional scores (KSS, OKS) showed a statistically significant improvement from the preoperative to last follow-up (p <0.001). All cones but one (98.6%) showed radiological osteointegration. We did not find any cone-related intraoperative or postoperative mechanical complication with a 100% survival rate when we consider aseptic loosening as cause of revision. Six non progressive radiolucencies were observed. Two septic failures (4.3%) with implant and cone removal were reported. Conclusions. The ideal treatment for cavitary bone defects in two-stage TKA septic revision is still unclear. The use of metaphyseal tantalum cones showed excellent clinical and radiographic results with a low rate of related complications. The main finding of our study is the cone-related infection rate (2.9%) in this particular series of patients. This data is comparable or better than other previous report about this topic with unhomogeneous cohort of patients

Aims: To determine the anthropometric measurements of bony landmarks in the knee using MR scans and so assist revision knee surgeons in prostheses placement. Methods: We analysed 100 MR scans of patients aged 16–50 (50 male, 50 female) which were performed for meniscal pathology, patellar dislocation and ACL injury. Those over the age of 50 or with symptoms suggestive of general osteoarthritis, or where the epiphyses had not yet fused were excluded. All measurements recorded were to the level of joint line and are shown below. Results:(Tables removed). Conclusions: To ensure near normal knee mechanics are achieved during revision knee surgery the joint line should be within 5mm of the original. Our study provides mean values for the distance from various bony landmarks to the joint line in non-arthritic knees on MR scan. The use of the medial epicondyle value as a sole reference will place the joint line within 5mm in 88% of males and 96% of females. Use of multiple landmarks further increases accuracy. The final position of the joint will depend on trialling prostheses

Aim. One of the most challenging problems in total knee arthroplasty (TKA) is periprosthetic infection. A major problem that arises in septic revision TKA (RTKA) are extended bone defects. In case of extended bone defects revision prostheses with metaphyseal sleeves are used. Only a few studies have been published on the use of metaphyseal sleeves in RTKA - none were septic exclusive. The aim of our study was to determine the implant survival, achieved osseointegration as well as the radiological mid-term outcomes of metaphyseal sleeve fixation in septic two-stage knee revision surgery. Method. Clinical and radiological follow-up examinations were performed in 49 patients (25 male and 24 female). All patients were treated with a two-stage procedure, using a temporary non-articulating bone cement spacer. The spacer was explanted after a median of 12 weeks (SD 5, min. 1 – max. 31) and reimplantation was performed, using metaphyseal sleeves in combination with stem fixation. Bone defects were classified on preoperative radiographs using the Anderson Orthopaedic Research Institute (AORI) classification. During follow-up postoperative range of motion (ROM) was measured and radiographs were performed to analyse: (i) osseointegration (radiolucent lines and spot welds), (ii) leg alignment, (iii) patella tilt and shift. Results. All types of bone defects were found on the tibial (4× type 1, 7× type 2a, 26× type 2b, 9× type 3) as well as on the femoral side (1× type 1, 4× type 2a, 20× type 2b, 6× type 3). Mean follow-up time was 4.7 years (minimum 1 year). In total 12 knees (24.5%) had to be re-revised, all due to re-infection. We did not encounter any case of aseptic loosening. In 3 patients (6.8%) we detected an insufficient osseointegration, but no patient had to be re-revised due to only minimal or to the absence of symptoms and no clinical signs of loosening. The ROM (mean 93°, SD 20.6, min. 25° max. 125°) has shown very satisfying results at the time of follow-up. Malalignment was detected in 4 patients (10.3%), a patella tilt in 7 (19.4%) and a patella shift in 14 (48.3%). Conclusions. Metaphyseal Sleeves have shown very promising mid-term results regarding osseointegration and aseptic implant survival in RTKA with compromised metaphyseal bone stock. Our results indicate that they are a reliable fixation option in septic RTKA patients

Aims: To determine the anthropometric measurements of bony landmarks in the knee using MR scans and so assist revision knee surgeons in prostheses placement. Methods: We analysed 100 MR scans of patients aged 16–50 (50 male, 50 female) which were performed for meniscal pathology, patellar dislocation and ACL injury. Those over the age of 50 or with symptoms suggestive of general osteoarthritis, or where the epiphyses had not yet fused were excluded. All measurements recorded were to the level of joint line and are shown below. Conclusions: To ensure near normal knee mechanics are achieved during revision knee surgery the joint line should be within 5mm of the original. Our study provides mean values for the distance from various bony landmarks to the joint line in non-arthritic knees on MR scan. The use of the medial epicondyle value as a sole reference will place the joint line within 5mm in 88% of males and 96% of females. Use of multiple landmarks further increases accuracy. The final position of the joint will depend on trialling prostheses

Introduction. We discuss the use of the SMILES (Stanmore Modular Individualised Lower Extremity System) in salvage revision knee surgery and review the medium-long term results of 42 cases. Methods. This is a prospective, single-centre study. The SMILES prosthesis is a custom-made implant incorporating a rotating hinge knee joint. 42 prostheses were used in 40 patients as salvage revision procedures between September 1991 and September 1999. Patients undergoing surgery for tumours were excluded. The minimum follow-up was seven years with a mean follow-up of ten years and six months. Patients were independently assessed using the Knee Society Rating Score. The age of the patients ranged from 36-85 years (mean 68 years and 6 months). 23 of the patients were male. The original pathology was osteoarthritis in 32 patients and rheumatoid arthritis in 8 patients. The number of previous arthroplasties ranged from 1-4. The main indications for a SMILES prosthesis were aseptic loosening, periprosthetic fracture and infection in the presence of bone loss and ligamentous laxity. Results. There was a highly statistically significant improvement in overall Knee Society scores from a mean of 26 pre-op to 72 post-op. The mean knee score improved from 26 pre-op to 68 post-op while the mean function score improved from 27 to 75. The average range of motion was 60 degrees pre-op and 90 degrees post-op. Complications included: failure to eradicate infection in two patients, with one patient needing amputation; infection of the prosthesis leading to revision in one, and failure of the tibial component needing revision. Conclusion. The SMILES has produced satisfactory results in the medium to long term, offering an alternative to amputation in some cases. The cost compares favourably with other designs and the use is increasing in frequency

Revision surgery for total knee replacement is a complex procedure, carrying an increased risk for the patient and cost for hospitals. As well as increased cost of peri-operative investigations, blood transfusions, surgical instrumentation, implants and theatre time, there is a well documented increased length of stay (LOS), accounting for the majority of actual costs associated with surgery. We compared revision surgery for infection vs. other causes (aseptic loosening, dislocation, mal-alignment). Clinical, demographic and economic data were obtained for 180 consecutive revision total knee replacements performed at a tertiary referral centre between 2003 and 2012. Actual costs and National Health Service tariffs were compared per patient and mean difference calculated. Mean age was 66 years (range 17–87) with 62 male and 117 female patients. Mean LOS for aseptic cases was 10 days (range 1–62) and 20 days (range 4–103) for infection. Mean cost difference in aseptic cases (n = 125) was £−933 (SD = £12,204), and £−3907 (SD = £7,256) for infection (n = 54). Surgery for infection was associated with increased operating times, blood loss and complications compared to revision for aseptic causes. LOS for infection was on average double that for aseptic cases (p < 0.05). Current NHS tariffs do not fully reimburse the increased costs associated with providing a revision knee surgery service, with even greater cost incurred by the treating hospital for infected cases. These losses may negatively influence the provision of revision surgery in the NHS

Background

A limited number of investigations with conflicting results have described perivascular lymphocytic infiltration (PVLI) in the setting of total knee arthroplasty. The purpose of this study was to determine if PVLI found in total knee replacements at the time of aseptic revision surgery was associated with worse clinical outcomes and survivorship.

Aim

Due to medical and organizational factors, it occurs in everyday practice that spacers are left in place longer than originally planned during a two-stage prosthesis exchange in the case of prosthetic joint infections. Patients are severely restricted in their mobility and, after initial antibiotic administration, the spacer itself only acts as a foreign body. The aim of this study is to analyze whether the duration of the spacer in situ has an influence on the long-term success of treatment and mortality.

Introduction

PSI technology have proved helpful in difficult primary Total Knee Replacement. However applying it to revision was impossible due to multiple factor. To Start with the landmark We usually destroy it. There is an extensive damage at the bone at the epiphysis, the implant prevent an accurate visualization and debridement usually change the surface of the bone as well which make applying the psi dyed impossible, we are proposing a new way of using psi in revision where we don't depend on the all masses adjusted in primary. However we depend on the metaphysical area of the bone.

The Dual Articular Knee (Biomet®) is a modular revision prosthesis with a mobile bearing. We performed 24 operations on 23 patients: 16 female and 7 male patients. The average age at revision was 71.6 years, range 42–84 y, the average time span between primary TKR and revision was 8 years, range 1–19 y. The average follow up was 25 months, range 3–68 months.

Diagnoses at primary TKR were: Osteoarthritis 19, Rheumatoid arthritis 1, Post-traumatic arthrosis 2, s/a medial Unicondylar 1, s/a High Tibial Osteotomy 1.

Primary Implants were: Total Condylar (Howmedica) 4 (3 with metal trays and 1 all PE tibia); IB 2 (Zimmer) 9, IB 1 (Zimmer) 2, Miller Galante (Zimmer) 1, AGC (Biomet) 5, Sigma (J& J) 2, Sigma RP (J& J) 1.

Inciations for revision were:

Aseptic loosening and PE wear 20, Infection 4 (Organisms: MRSA 1, Enterococcus Faeconium 1, Streptococcus Gr.6 1, Negative Culture 1).

Surgical Technique: We used a medial parapatellar approach in 22 knees and the lateral parapatellar approach in 2 knees, osteotomy of the tibial tuberosity was performed in 16 operations and a lateral patellar release in 7. The patellar implant was replaced in 5 knees, left in situ in 4 and not replaced in 15 knees (one of the knees was after a previous patellectomy). Two stage revision was performed in 4 infected knees and in one non-infected. Cement spacers impregnated with antibiotics were used in 3 operations. Original implants as temporary implants with antibiotic loaded cement were used in 2 operations.

Results: Results were rated as good if the knee was stable with flexion of 90 degrees or more without evidence of infection and fair with less than 90 degrees of flexion.

Good results were obtained in 19 knees, fair in 2, failure due to late infection in one knee. One patient was lost for follow up, one patient died 6 months after surgery of an unrelated cause.

Conclusions: The Dual Articular Revision Prosthesis is a useful implant system in cases with satisfactory collateral ligament stability.

A computer assisted technique for TKA Revision is presented. It is based on the use of a navigation system, RTKANav consisting of anl optical localizer, a dedicated software specifically done for TKA revision and some navigated tools developed for this application.

The system doesn’t use any patient model derived from medical images, but on the system interface patient anatomy model is represented with dots and lines corresponding to acquired landmarks and data derived from them. These data describe the main anatomical features and provide the surgeon with the main references for the intervention; angles between the mechanical axes can be controlled and monitored at any time.

Even if during acquisition phase some specific points can not be identified, since for each prosthetic component several criteria to set each degree of freedom are considered and compared, the system is always able suggest an intervention plan.

The system provides the surgeon with tools to analyse and modify the proposed plan, and to reproduce it on the patient.

Navigated technique validation is under development. Till now it was used on two patients by an expert surgeon. Computer guidance showed early promising results providing the surgeon with useful indications achieve a satisfactory prosthesis implant.