RESUMEN

Small and unintended offsets, tilts, and eccentricity of the mechanical and optical components in laser trackers introduce systematic errors in the measured spherical coordinates (angles and range readings) and possibly in the calculated lengths of reference artifacts. It is desirable that the tests described in the ASME B89.4.19 Standard [1] be sensitive to these geometric misalignments so that any resulting systematic errors are identified during performance evaluation. In this paper, we present some analysis, using error models and numerical simulation, of the sensitivity of the length measurement system tests and two-face system tests in the B89.4.19 Standard to misalignments in laser trackers. We highlight key attributes of the testing strategy adopted in the Standard and propose new length measurement system tests that demonstrate improved sensitivity to some misalignments. Experimental results with a tracker that is not properly error corrected for the effects of the misalignments validate claims regarding the proposed new length tests.

RESUMEN

Since pulsed low-intensity ultrasound (frequency: 1.5 MHz, pulsed by 1 kHz, signal burst width: 200 microseconds, intensity: 30 mW/cm2) has been proven to stimulate fracture healing both clinically and experimentally, our question was whether this therapy also accelerates healing of fresh stable scaphoid fractures. Addressing this question, we did the following prospective randomized clinical trial. Regarding the results of former clinical fresh fracture studies by Heckman and Kristiansen, we postulated that low intensity ultrasound accelerates healing by about 30%. Based on this thesis, we calculated that 30 patients divided into two groups would be necessary to show significant differences between the standard treatment (treated by casting) and an adjunctive ultrasound treatment (treated by casting and additional daily 20 minutes ultrasound treatment) if present. Diagnosis and healing was assessed by CT scans every two weeks. CT's were analyzed by two independent radiologists and one hand surgeon. Furthermore, areas of cancellous bone bridging in correlation to the diameter of the scaphoid was measured in each CT scan. The results showed ultrasounded fractures healing in 43.2 +/- 10.9 days versus 62 +/- 19.2 days in the control group (p < 0.01). Trabecular bridging six weeks after injury showed 81.2% +/- 10.4% healed in the ultrasound-stimulated fractures versus 54.6% +/- 29% in the control (p < 0.05). Our study results confirm those of Heckman and Kristiansen and show a similar acceleration of bone healing. Low intensity ultrasound is successful in accelerating the healing of fresh scaphoid fractures.

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RESUMEN

This report examines the results of the ball plate round robin administered by NIST. The round robin was part of an effort to assess the current state of industry practices for measurements made using coordinate measuring machines. Measurements of a two-dimensional ball plate (240 mm by 240 mm) on 41 coordinate measuring machines were collected and analyzed. Typically, the deviations of the reported X and Y coordinates from the calibrated values were within ± 5 µm, with some coordinate deviations exceeding 20.0 µm. One of the most significant observations from these data was that over 75 % of the participants failed to correctly estimate their measurement error on one or more of the ball plate spheres.

RESUMEN

The continuous extension of Dupuytren's contracture prior to aponeurectomy in severe cases, introduced by Messina, is presented. This technique demonstrates the possibility of reversing contractures; it simplifies the surgical treatment thereafter and avoids difficulties in blood circulation and sensibility. First results in ten patients are presented.

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RESUMEN

Dupuytren's contracture is a disease of the connective tissue, especially of the palmar side of the hand. Today, by means of electron microscopy and histochemistry, several alternations specific of pathology of the disease can be shown, providing a better understanding. However, a revolutionary change of treatment is far out of reach. Dupuytren's diathesis can be influenced by none of today's known methods, and therapy is still empirical. Operative therapy is only indicated in functional impairment. Treatment should be done by well-trained surgeons and in case of extensive diathesis by carefully planning and longtime follow-up to avoid complications and eruption of the disease.

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