Patellofemoral joint arthroplasty: patient selection,surgical technique and outcomes

Isolated patellofemoral arthritis is an increasingly recognized entity, and is usually associated with previous patellofemoral dysplasia or instability. Patellofemoral arthroplasty (PFA) has evolved significantly in recent years, both in terms of implant design and importantly in the understanding of appropriate patient selection. This review outlines the indications and investigations for PFA, provides a brief history of the development of contemporary implants, and presents the clinical outcomes for the prostheses most commonly used in the UK. In addition, it provides a detailed surgical technique for implantation of an onlay implant, with tips on how to optimize patellofemoral biomechanics and thus achieve a consistently good outcome.     

Treatment of refractoriness to platelet transfusion by protein A column therapy

Ten thrombocytopenic patients (platelets < 10–24 × 10(9)/L) who were refractory to platelet transfusion were investigated for their responsiveness to staphylococcal protein A column therapy. Nine patients had previously been treated with steroids, intravenous immune globulin, and/or other forms of immunosuppressive therapy without improvement in their transfusion response. All patients were receiving multiple platelet transfusions without achieving 1-hour corrected count increments (CCIs) > or = 7500. Eight patients had antibodies that reacted with platelets and were directed against HLA class I antigens, ABO antigens, and/or platelet-specific alloantigens. Plasma (500-2000 mL) from each patient was passed over a protein A silica gel column and then returned to the patient. Patients received from 1 to 14 treatments. A positive response to protein A therapy was defined as at least a doubling of the pretreatment platelet count and/or two successive 10- to 120-minute posttransfusion CCIs > or = 7500. Following plasma treatments, 6 of 10 patients responded with daily platelet counts that averaged 48 +/− 11 × 10(9) per L as compared with counts of 16 +/− 7 × 10(9) per L (p < 0.0005) before treatment. Posttransfusion CCI values determined in four of these patients averaged 2480 +/− 810 and 10,010 +/− 3540 (p < 0.005) before and after treatment, respectively. In contrast, among the four unresponsive patients, platelet counts averaged 10 +/− 9 and 13 +/− 10 × 10(9) per L (p = NS), respectively, while posttransfusion CCIs were 700 +/− 1410 and 1520 +/− 2460 (p = NS), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Botrocetin agglutination of rat megakaryocytes: a rapid method for megakaryocyte isolation.

Botrocetin isolated from the venom of Bothrops jaracara has been shown by others to induce binding of von Willebrand Factor to glycoprotein Ib and thereby produce platelet agglutination in a wide range of animal species. We have found that botrocetin also facilitates the agglutination of megakaryocytes and have used this property to develop a method to isolate megakaryocytes from rat bone marrow. When botrocetin is added to a mixture of rat bone marrow, rat platelets, and rat plasma, coagglutination of megakaryocytes and platelets occurs. The agglutinated complexes, containing > 95% of the megakaryocytes, may then be separated from the remaining marrow cells by filtration. Megakaryocytes account for 39% (range 30%-48%) of the isolated cells and 83% (range 77%-88%) of the isolated cell mass. This method allows the virtually complete removal of megakaryocytes from bone marrow as well as their isolation to a high degree of purity. It should provide a useful, inexpensive, general method for the rapid isolation of megakaryocytes from multiple, small marrow samples from a wide range of species.