Biomechanical comparison of stemless humeral components in total shoulder arthroplasty

BackgroundThe purpose of this study was to compare initial fixation strength between various stemless and stemmed humeral components and to correlate implant fixation strength with bone mineral density (BMD).MethodsFive humeral stem designs were investigated: Stemless-A (four hollow fins), Stemless-B (central body, three solid fins), Stemless-C (central screw, peripheral rim-fit), Short stem (50 mm), and Standard stem (130 mm). Fifty cadaveric human humerii were obtained and divided into five groups. BMD within the humeral head was determined for all samples. The mean BMD was similar between groups. The 25 samples with the lowest and highest BMDs were categorized as “Low” and “High,” respectively, with a BMD threshold of 0.35 g/cm², creating BMD subgroups. After implantation, each sample underwent a standardized biomechanical testing protocol, with axial loading followed by torsional loading. Sensors attached to the specimen recorded micromotion throughout testing. Axial loading consisted of cyclic loading for 100 cycles at 3 peak forces (220, 520, and 820 N). Torsional loading consisted of 100 cycles of internal/external rotation at 0.1 Hz at 6 peak torques, or until failure (±2.5, 5, 7.5, 10, 12.5, and 15 Nm). Failure was defined as the torque at which any bone fracture, implant detachment from anchor/stem, or an excess of 50° internal/external rotation occurred. Groups and BMD subgroups were compared.ResultsAt maximal axial loading, Stemless-B demonstrated greater micromotion (540 μm) than Stemless-C (192 μm) (P = .003). Stemless-B and Stemless-A (387 μm) also had greater micromotion than Short stem (118 μm, P < .001, P = .03) and Standard stem (85 μm, P < .001, P = .01). When comparing low-BMD samples at maximal axial loading, these differences were accentuated, but comparison of high-BMD samples showed no significant differences between groups. Torsional testing demonstrated that Standard stem failed at greater torque (7.2 Nm) than Stemless-B (2.3 Nm, P < .001), Stemless-A (1.9 Nm, P < .001), and Stemless-C (3.9 Nm, P = .01). When comparing torsional testing results of low-BMD samples, both Standard stem and Short stem failed at greater torque than Stemless-B (P = .02, P = .003) and Stemless-A (P = .03, P = .004) but failed at a similar torque to Stemless-C. Torsional testing of high-BMD samples showed that Standard stem failed at a greater torque than all stemless designs.ConclusionStemless humeral implants should be used with caution in low-BMD settings (<0.35 g/cm²). A central screw and peripheral rim-fit stemless anchor design demonstrated greater fixation strength at low BMD when compared with other designs, while all stemless designs performed similarly at high BMD.Level of evidenceBasic Science Study; Cadaveric Study     

The Effect of Prostate Cancer Educational Program on the level of Knowledge and Intention to Screen among Jordanian Men in Amman

Purpose: The purpose of this study was to examine the effect of prostate cancer educational program on the level of knowledge and intention to screen for prostate cancer among Jordanian men in Amman. Methods: A quasi-experimental, with nonequivalent control group design was used. 154 participants were randomly assigned to the intervention and control groups.  Level of Knowledge and intention to screen were measured at baseline and at 1 month after the application of the prostate cancer educational program. Independent sample t-test was used to analyze the data. Results: The results showed statistically significant change in the mean knowledge scores (8.7), p < 0.001 and the mean of intention to screen scores (3.71), p < 0.001, after 1 month from the application of the educational program in the experimental group compared to the control group. Conclusion: Implementing prostate cancer educational programs help enhance knowledge and intention to screen among Jordanian men.     

Industry Funding Is Correlated With Publication Productivity of US Academic Radiation Oncologists

Purpose

Industry payments to physicians are financial conflicts of interest and may influence research findings and medical decisions. We aim to (1) characterize industry payments within radiation oncology; and (2) explore the potential correlation between receiving disclosed industry payments and academic productivity.

Parathyroid hormone 1–34 enhances extracellular matrix deposition and organization during flexor tendon repair

Parathyroid hormone (PTH) 1–34 is known to enhance fracture healing. Tendon repair is analogous to bone healing in its dependence on the proliferation and differentiation of mesenchymal stem cells, matrix formation, and tissue remodeling.^1,2,3 We hypothesized that PTH 1–34 enhances tendon healing in a flexor digitorum longus (FDL) tendon repair model. C57Bl/6J mice were treated with either intraperitoneal PTH 1–34 or vehicle‐control (PBS). Tendons were harvested at 3–28 days for histology, gene expression, and biomechanical testing. The metatarsophalangeal joint range of motion was reduced 1.5–2‐fold in PTH 1–34 mice compared to control mice. The gliding coefficient, a measure of adhesion formation, was 2–3.5‐fold higher in PTH 1–34 mice. At 14 days post‐repair, the tensile strength was twofold higher in PTH 1–34 specimens, but at 28 days there were no differences. PTH 1–34 mice had increased fibrous tissue deposition that correlated with elevated expression of collagens and fibronectin as seen on quantitative PCR. PTH 1–34 accelerated the deposition of reparative tissue but increased adhesion formation. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:17–24, 2015.