Background:Dislocation following total knee arthroplasty (TKA) is the worst form of instability. The incidence is from 0.15 to 0.5%. We report six cases of TKA dislocation and analyze the patterns of dislocation and the factors related to each of them.Materials and Methods:Six patients with dislocation of knee following TKA are reported. The causes for the dislocations were an imbalance of the flexion gap (n=4), an inadequate selection of implants (n=1), malrotation of components (n=1) leading to incompetence of the extensor mechanism, or rupture of the medial collateral ligament (MCC). The patients presented complained of pain, giving way episodes, joint effusion and difficulty in climbing stairs. Five patients suffered posterior dislocation while one anterior dislocation. An urgent closed reduction of dislocation was performed under general anaesthesia in all patients. All patients were operated for residual instability by revision arthroplasty after a period of conservative treatment.Results:One patient had deep infection and knee was arthrodesed. Two patients have a minimal residual lag for active extension, including a patient with a previous patellectomy. Result was considered excellent or good in four cases and fair in one, without residual instability. Five out of six patients in our series had a cruciate retaining (CR) TKA designs: four were revised to a posterior stabilized (PS) TKA and one to a rotating hinge design because of the presence of a ruptured MCL.Conclusion:Further episodes of dislocation or instability will be prevented by identifying and treating major causes of instability. The increase in the level of constraint and correction of previous technical mistakes is mandatory.

Background and purpose The most reliable results when treating an infected total knee arthroplasty have been obtained with a two-stage reimplantation protocol. We have used a simple technique for hand-made spacers and now report the outcome.Patients and methods 30 patients with an infected total knee arthroplasty (TKA) were treated with a 2-stage reimplantation protocol. Spacers were built and customized to the type of defect using only 2 retractors and a high-speed tip burr. Partial weight bearing and discharge from the hospital were encouraged in the time between surgeries. 29 of 30 patients (97%) had successful reimplantations and they were followed for an average of 3 (2-5) years.Results Range of motion with the articulating spacer averaged 80° (55-100) and 21 of the 30 patients achieved motion greater than 75°. At the latest follow-up, there were no reinfections. According to the Knee Society score (KSS), the results were considered excellent or good in 25 patients, and fair or poor in 4 of the 29 patients with reimplantations. Motion after reimplantation averaged 107° (90-120).Interpretation One of the key factors related to a successful outcome with a two-stage reimplantation procedure is to keep the joint mobile and functional in the time between surgeries. Hand-made articulating spacers retain most of the advantages of more complex spacers in terms of mobility, pain, bone loss, success, or re-infection rate-with the major advantages of price and universal availability. Limitations related to this technique

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Abstract.Individual users of medical language manifest great variation in the expression of concepts and have difficulty in selecting appropriate terminology when confronted with systems that rely on standardized language, such as MeSH, SNOMED, or ICD, and the special terms sets of systems such as HELP, INTERNIST-I/QMR, and DXplain. Indeed, the need to map natural language into appropriate special terms-as well as the need to map one system's specialized terminology into another's-is one of the problems being addressed by the National Library of Medicine's UMLS System, with its associated information sources maps. The problem is extremely difficult, in part, because such mappings depend on semantic equivalences among terms, not merely the superficial matching of words or phrases.As a general and robust solution to the problem of mapping across vocabularies, we implemented a version of "latent semantic indexing", taking terms from different vocabularies as the 'documents' to be retrieved by natural-language expressions of concepts, taken as 'queries'. In one of several experiments testing our approach, for example, we selected approximately 225 terms each from the INTERNIST-I/QMR, PTXT, and META-1 vocabularies corresponding to clinical findings under the physical exam. We constructed a source matrix of associations between the findings and all the 'words' they contained, supplemented with word-level synonyms and related terms. The resulting source rectangular matrix was approximately 650x3000. Under singular value decomposition, this was reduced to a compressed space of at most 650 dimensions. The performance of the reduced space as a "latent semantic" map of the source domain was evaluated by processing phrases, intended to be interpreted as clinical findings, as term-vectors, projected into the reduced space. In calculating the projections, we considered only the 150 most significant dimensions. Mappings to concepts (i.e., standardized terms) were determined by taking the cosine-distance measure of the vector to all the term-points in the reduced space. As an example of the results, the phrase "stomach discomfort worse after eating" scored as follows ( The power of the approach is that it does not depend on explicit, declarative semantic representations or on word-for-word correspondences among terms; and that multiple vocabularies can be represented side-by-side.Communications should be directed to: