Polymerase chain reaction-based screening of childhood acute lymphoblastic leukemia (ALL) samples showed that a TEL/AML1 fusion transcript was detected in 27% of all cases, representing the most common known gene rearrangement in childhood cancer. The TEL/AML1 fusion results from a t(12;21)(p13;q22) chromosomal translocation, but was undetectable at the routine cytogenetic level. TEL/AML1-positive patients had exclusively B-lineage ALL, and most patients were between the ages of 2 and 9 years at diagnosis. Only 3/89 (3.4%) adult ALL patients were TEL/AML1-positive. Most importantly, TEL/AML1-positive children had a significantly lower rate of relapse compared with TEL/AML1-negative patients (0/22 v 16/54, P = .004). Co- immunoprecipitation experiments demonstrated that TEL/AML-1 formed homodimers in vitro, and heterodimerized with the normal TEL protein when the two proteins were expressed together. The elucidation of the precise mechanism of transformation by TEL/AML1 and the role of TEL/AML1 testing in the treatment of childhood ALL will require additional studies.

Modular connections have been commonly and successfully utilized in orthopaedic implant systems for the last 15 or so years, particularly at the head/neck junction in total hip arthroplasty (THA). However, recent retrieval studies have shown that some of the tapered junctions between femoral heads and stems in total hip arthoplasty can be prone to fretting corrosion, and may be a cause for concern in the longevity of implants. Fretting corrosion, which may release metallic products (particulate debris and ions) into the joint space, is a complex phenomenon in which the interplay between mechanically induced interfacial micromotion (fretting) and electrochemical corrosive activity play an important role, along with materials selection and processes. This suggests that interfacial fretting corrosion at modular implant interfaces can be significantly affected by the design variables of the modular junction. The working hypothesis of this study was that different designs of the modular head/stem combination of femoral hip prostheses exhibit different release of fretting corrosion metal products during fatigue testing used to simulate ten years of in vivo service. Three designs of femoral head (Co-Cr-Mo alloy) and stem (Ti-6Al-4V alloy) combinations were investigated in this study. The study included detailed taper metrology followed by environmental fatigue testing of the tapered junctions. The results of this study showed that important taper design differences do exist in the three constructs tested, and these differences manifested in different fretting corrosion behavior.

Today in the United States, 95% of all total hip implants contain at least one modular junction. The most common of these junctions connects the femoral head and neck taper. Because this connection utilizes a Morse taper, various materials and design variables can influence fretting and corrosion behavior at the mating surfaces, and ultimately the longevity of the device. In order to isolate and study the behavior of the femoral head/neck taper connection, a simplified model of a neck taper was designed. Test specimens were manufactured of Ti-6Al-4V and Co-Cr, and were designed to accept a Co-Cr femoral head. These constructs provided control in the experiment by focusing on the femoral head/neck taper interface, and by facilitating debris collection. Each construct was encapsulated with Ringer's solution and subjected to a fatigue load of 490 N to 4900 N at a rate of 10 hertz for ten million cycles. Using direct current plasma-optical emission spectroscopy (DCP-OES), the Ringer's solution was analyzed for titanium and cobalt ions after the fatigue test. The titanium level measured for the Ti-6Al-4V/Co-Cr constructs was less than 0.05 mg/L. For the Ti-6Al-4V/Co-Cr and Co-Cr/Co-Cr constructs, the cobalt levels were 0.95 – 0.23 mg/L and 1.16 – 0.57 mg/L, respectively. This test method was designed to determine the debris generated at the femoral head/neck taper interface by controlling for specific design/fixation variables. It can be used to predict how such factors as material, taper diameter, taper angle, taper engagement, and tolerances affect the generation of wear debris during fatigue. Although the results do not predict the debris generation of an actual hip prosthesis, they may indicate performance characteristics which can be generalized to in-vivo behavior of the device.

The acetabular component is the focus of new testing methods dedicated to the development of improved total hip prostheses. Test methods had previously been developed to assess the performance of the femoral component in both the static and dynamic modes. These methods were designed in accordance with standards generated by such organizations as ASTM, ISO, and by research institutions. However, acetabular components were generally tested in the static mode to evaluate engagement strength and torsional resistance of the liner. While these tests are important and give a measure of the mechanical integrity of the device, they do not fully address clinical performance. From retrieved components, it appears that a loose or failing locking mechanism allows torsional forces to transfer through the liner causing liner abrasion, burnishing, and in some cases degradation of the locking mechanism itself. Success of the device may be further compromised by the biological response to debris created by micromotion between the mating components. This study was undertaken to assess the rotational stability of the acetabular liner in a dynamic mode. Several acetabular component designs were torsionally fatigued at ±2.5 Nm at a rate of 3–5 hertz for 10 million cycles. The test components exhibited liner micromotion ranging from 0.059° to 2.89°, and damage to the nonarticulating interface and locking mechanism of tested liners was visually identified. This method for dynamic testing of acetabular components provides an understanding of the performance of the device under torsional fatigue conditions. It demonstrates the importance of a rotationally stable liner, as damage to the nonarticulating interface of tested liners is similar to damage reported in the literature for retrieved components. Further, it determines the endurance of the liner locking mechanism when subjected to dynamic torsional forces.